Added Debian 13 policies and hardening guides.

* print config v2

 - printconfig script
 - test_printconfig for tox testing
 - update globals for GUIDES_UPDATED date value
 - update ssh_audit for print_config argument and checks

* pr307 update 1

* pr307 update 2

* pr307 - attempt 2

* Update ssh_audit.py

Missed a TAB

.github/workflows/tox.yaml

@@ -7,7 +7,7 @@ jobs:
     runs-on: ubuntu-latest
     strategy:
       matrix:
-        python-version: ["3.8", "3.9", "3.10", "3.11", "3.12", "3.13"]
+        python-version: ["3.9", "3.10", "3.11", "3.12", "3.13"]
 
     steps:
       - uses: actions/checkout@v4

README.md

@@ -35,18 +35,24 @@
 - historical information from OpenSSH, Dropbear SSH and libssh;
 - policy scans to ensure adherence to a hardened/standard configuration;
 - runs on Linux and Windows;
-- supports Python 3.8 - 3.13;
+- supports Python 3.9 - 3.13;
 - no dependencies
 
 ## Usage
 ```
 usage: ssh-audit.py [-h] [-4] [-6] [-b] [-c] [-d]
-                    [-g <min1:pref1:max1[,min2:pref2:max2,...]> / <x-y[:step]>] [-j] [-l {info,warn,fail}] [-L]
+                    [-g <min1:pref1:max1[,min2:pref2:max2,...]> / <x-y[:step]>]
-                    [-M custom_policy.txt] [-m] [-n] [-P "Built-In Policy Name" / custom_policy.txt] [-p N]
+                    [-j] [-l {info,warn,fail}] [-L] [-M custom_policy.txt]
-                    [-T targets.txt] [-t N] [-v] [--conn-rate-test N[:max_rate]] [--dheat N[:kex[:e_len]]]
+                    [-m] [-n] [-P "Built-In Policy Name" / custom_policy.txt]
-                    [--lookup alg1[,alg2,...]] [--skip-rate-test] [--threads N]
+                    [-p N] [-T targets.txt] [-t N] [-v]
+                    [--conn-rate-test N[:max_rate]] [--dheat N[:kex[:e_len]]]
+                    [--get-hardening-guide platform] [--list-hardening-guides]
+                    [--lookup alg1[,alg2,...]] [--skip-rate-test]
+                    [--threads N]
                     [host]
 
+# ssh-audit.py v3.4.0-dev, https://github.com/jtesta/ssh-audit
+
 positional arguments:
   host                  target hostname or IPv4/IPv6 address
 
@@ -55,44 +61,74 @@ optional arguments:
   -4, --ipv4            enable IPv4 (order of precedence)
   -6, --ipv6            enable IPv6 (order of precedence)
   -b, --batch           batch output
-  -c, --client-audit    starts a server on port 2222 to audit client software config (use -p to change port; use -t
+  -c, --client-audit    starts a server on port 2222 to audit client software
-                        to change timeout)
+                        config (use -p to change port; use -t to change
+                        timeout)
   -d, --debug           enable debugging output
   -g <min1:pref1:max1[,min2:pref2:max2,...]> / <x-y[:step]>, --gex-test <min1:pref1:max1[,min2:pref2:max2,...]> / <x-y[:step]>
-                        conducts a very customized Diffie-Hellman GEX modulus size test. Tests an array of minimum,
+                        conducts a very customized Diffie-Hellman GEX modulus
-                        preferred, and maximum values, or a range of values with an optional incremental step amount
+                        size test. Tests an array of minimum, preferred, and
-  -j, --json            enable JSON output (use -jj to enable indentation for better readability)
+                        maximum values, or a range of values with an optional
+                        incremental step amount
+  -j, --json            enable JSON output (use -jj to enable indentation for
+                        better readability)
   -l {info,warn,fail}, --level {info,warn,fail}
                         minimum output level (default: info)
-  -L, --list-policies   list all the official, built-in policies. Combine with -v to view policy change logs
+  -L, --list-policies   list all the official, built-in policies. Combine with
+                        -v to view policy change logs
   -M custom_policy.txt, --make-policy custom_policy.txt
-                        creates a policy based on the target server (i.e.: the target server has the ideal
+                        creates a policy based on the target server (i.e.: the
-                        configuration that other servers should adhere to), and stores it in the file path specified
+                        target server has the ideal configuration that other
-  -m, --manual          print the man page (Docker, PyPI, Snap, and Windows builds only)
+                        servers should adhere to), and stores it in the file
-  -n, --no-colors       disable colors (automatic when the NO_COLOR environment variable is set)
+                        path specified
+  -m, --manual          print the man page (Docker, PyPI, Snap, and Windows
+                        builds only)
+  -n, --no-colors       disable colors (automatic when the NO_COLOR
+                        environment variable is set)
   -P "Built-In Policy Name" / custom_policy.txt, --policy "Built-In Policy Name" / custom_policy.txt
-                        run a policy test using the specified policy (use -L to see built-in policies, or specify
+                        run a policy test using the specified policy (use -L
-                        filesystem path to custom policy created by -M)
+                        to see built-in policies, or specify filesystem path
-  -p N, --port N        the TCP port to connect to (or to listen on when -c is used)
+                        to custom policy created by -M)
+  -p N, --port N        the TCP port to connect to (or to listen on when -c is
+                        used)
   -T targets.txt, --targets targets.txt
-                        a file containing a list of target hosts (one per line, format HOST[:PORT]). Use -p/--port
+                        a file containing a list of target hosts (one per
-                        to set the default port for all hosts. Use --threads to control concurrent scans
+                        line, format HOST[:PORT]). Use -p/--port to set the
-  -t N, --timeout N     timeout (in seconds) for connection and reading (default: 5)
+                        default port for all hosts. Use --threads to control
+                        concurrent scans
+  -t N, --timeout N     timeout (in seconds) for connection and reading
+                        (default: 5)
   -v, --verbose         enable verbose output
   --conn-rate-test N[:max_rate]
-                        perform a connection rate test (useful for collecting metrics related to susceptibility of
+                        perform a connection rate test (useful for collecting
-                        the DHEat vuln). Testing is conducted with N concurrent sockets with an optional maximum
+                        metrics related to susceptibility of the DHEat vuln).
-                        rate of connections per second
+                        Testing is conducted with N concurrent sockets with an
+                        optional maximum rate of connections per second
   --dheat N[:kex[:e_len]]
-                        continuously perform the DHEat DoS attack (CVE-2002-20001) against the target using N
+                        continuously perform the DHEat DoS attack
-                        concurrent sockets. Optionally, a specific key exchange algorithm can be specified instead
+                        (CVE-2002-20001) against the target using N concurrent
-                        of allowing it to be automatically chosen. Additionally, a small length of the fake e value
+                        sockets. Optionally, a specific key exchange algorithm
-                        sent to the server can be chosen for a more efficient attack (such as 4).
+                        can be specified instead of allowing it to be
+                        automatically chosen. Additionally, a small length of
+                        the fake e value sent to the server can be chosen for
+                        a more efficient attack (such as 4).
+  --get-hardening-guide platform
+                        retrieves the hardening guide for the specified
+                        platform name (use --list-hardening-guides to see list
+                        of available guides).
+  --list-hardening-guides
+                        list all official, built-in hardening guides for
+                        common systems. Their full names can then be passed to
+                        --get-hardening-guide. Add -v to this option to view
+                        hardening guide change logs and prior versions.
   --lookup alg1[,alg2,...]
-                        looks up an algorithm(s) without connecting to a server.
+                        looks up an algorithm(s) without connecting to a
-  --skip-rate-test      skip the connection rate test during standard audits (used to safely infer whether the DHEat
+                        server.
-                        attack is viable)
+  --skip-rate-test      skip the connection rate test during standard audits
-  --threads N           number of threads to use when scanning multiple targets (-T/--targets) (default: 32)
+                        (used to safely infer whether the DHEat attack is
+                        viable)
+  --threads N           number of threads to use when scanning multiple
+                        targets (-T/--targets) (default: 32)
 ```
 * if both IPv4 and IPv6 are used, order of precedence can be set by using either `-46` or `-64`.
 * batch flag `-b` will output sections without header and without empty lines (implies verbose flag).
@@ -183,7 +219,7 @@ Below is a screen shot of the client-auditing output when an unhardened OpenSSH
 ![client_screenshot](https://user-images.githubusercontent.com/2982011/68867998-b946c100-06c4-11ea-975f-1f47e4178a74.png)
 
 ## Hardening Guides
-Guides to harden server & client configuration can be found here: [https://www.ssh-audit.com/hardening_guides.html](https://www.ssh-audit.com/hardening_guides.html)
+Guides to harden server & client configuration are built into the tool (see `--list-hardening-guides` and `--get-hardening-guide` options).  Additionally, they are also available online at: [https://www.ssh-audit.com/hardening_guides.html](https://www.ssh-audit.com/hardening_guides.html)
 
 ## Pre-Built Packages
 Pre-built packages are available for Windows (see the [Releases](https://github.com/jtesta/ssh-audit/releases) page), PyPI, Snap, and Docker:
@@ -215,11 +251,16 @@ For convenience, a web front-end on top of the command-line tool is available at
 
 ### v3.4.0-dev
  - BIG THANKS to [realmiwi](https://github.com/realmiwi) for being the project's *very first sponsor!!*
+ - Dropped support for Python 3.8, as it reached end-of-life in October 2024.
  - Added warning to all key exchanges that do not include protections against quantum attacks due to the Harvest Now, Decrypt Later strategy (see https://en.wikipedia.org/wiki/Harvest_now,_decrypt_later).
  - Removed SSHv1 support (rationale is documented in: https://github.com/jtesta/ssh-audit/issues/298).
+ - Added hardening guides (see `--list-hardening-guides` and `--get-hardening-guide`).  Previously, they were only available at <https://ssh-audit.com/hardening_guides.html>, but now they are built-in for convenience; partial credit [oam7575](https://github.com/oam7575).
+ - Added `allow_hostkey_subset_and_reordering` policy option to allow targets to have a more stringent list of host keys and/or a different ordering of them.
  - Migrated from deprecated `getopt` module to `argparse`; partial credit [oam7575](https://github.com/oam7575).
  - When running against multiple hosts, now prints each target host regardless of output level.
  - Batch mode (`-b`) no longer automatically enables verbose mode, due to sometimes confusing results; users can still explicitly enable verbose mode using the `-v` flag.
+ - Added built-in policy for OpenSSH 10.0.
+ - Added hardening guides and policies for Debian 13.
  - Added 2 new key exchanges: `mlkem768nistp256-sha256`, `mlkem1024nistp384-sha384`.
  - Added 2 new ciphers: `AEAD_CAMELLIA_128_GCM`, `AEAD_CAMELLIA_256_GCM`.
 

docker_test.sh

@@ -793,6 +793,9 @@ run_custom_policy_test "config2" "test16" "${PROGRAM_RETVAL_FAILURE}"
 # Passing test with larger key matching.
 run_custom_policy_test "config2" "test17" "${PROGRAM_RETVAL_GOOD}"
 
+# Passing test with host key subset matching.
+run_custom_policy_test "config2" "test18" "${PROGRAM_RETVAL_GOOD}"
+
 # Failing test for built-in OpenSSH 8.0p1 server policy (RSA host key size is 3072 instead of 4096).
 run_builtin_policy_test "Hardened OpenSSH Server v8.0 (version 4)" "8.0p1" "test1" "-o HostKeyAlgorithms=rsa-sha2-512,rsa-sha2-256,ssh-ed25519 -o KexAlgorithms=curve25519-sha256,curve25519-sha256@libssh.org,diffie-hellman-group16-sha512,diffie-hellman-group18-sha512,diffie-hellman-group-exchange-sha256 -o Ciphers=chacha20-poly1305@openssh.com,aes256-gcm@openssh.com,aes128-gcm@openssh.com,aes256-ctr,aes192-ctr,aes128-ctr -o MACs=hmac-sha2-256-etm@openssh.com,hmac-sha2-512-etm@openssh.com,umac-128-etm@openssh.com" "${PROGRAM_RETVAL_FAILURE}"
 

setup.cfg

@@ -19,7 +19,6 @@ classifiers =
     License :: OSI Approved :: MIT License
     Operating System :: OS Independent
     Programming Language :: Python :: 3
-    Programming Language :: Python :: 3.8
     Programming Language :: Python :: 3.9
     Programming Language :: Python :: 3.10
     Programming Language :: Python :: 3.11
@@ -34,7 +33,7 @@ classifiers =
 packages = find:
 package_dir =
      = src
-python_requires = >=3.8,<4
+python_requires = >=3.9,<4
 
 [options.packages.find]
 where = src

src/ssh_audit/builtin_policies.py

@@ -38,6 +38,8 @@ BUILTIN_POLICIES: Dict[str, Dict[str, Union[Optional[str], Optional[List[str]],
 
     'Hardened Debian 12 (version 2)': {'version': '2', 'changelog': 'Re-ordered host keys to prioritize ED25519 due to efficiency.  Re-ordered cipher list to prioritize larger key sizes as a countermeasure to quantum attacks.', 'banner': None, 'compressions': None, 'host_keys': ['ssh-ed25519', 'rsa-sha2-512', 'rsa-sha2-256'], 'optional_host_keys': ['sk-ssh-ed25519@openssh.com', 'ssh-ed25519-cert-v01@openssh.com', 'sk-ssh-ed25519-cert-v01@openssh.com', 'rsa-sha2-256-cert-v01@openssh.com', 'rsa-sha2-512-cert-v01@openssh.com'], 'kex': ['sntrup761x25519-sha512@openssh.com', 'curve25519-sha256', 'curve25519-sha256@libssh.org', 'diffie-hellman-group16-sha512', 'diffie-hellman-group18-sha512', 'diffie-hellman-group-exchange-sha256', 'kex-strict-s-v00@openssh.com'], 'ciphers': ['chacha20-poly1305@openssh.com', 'aes256-gcm@openssh.com', 'aes256-ctr', 'aes192-ctr', 'aes128-gcm@openssh.com', 'aes128-ctr'], 'macs': ['hmac-sha2-256-etm@openssh.com', 'hmac-sha2-512-etm@openssh.com', 'umac-128-etm@openssh.com'], 'hostkey_sizes': {"rsa-sha2-256": {"hostkey_size": 4096}, "rsa-sha2-256-cert-v01@openssh.com": {"ca_key_size": 4096, "ca_key_type": "ssh-rsa", "hostkey_size": 4096}, "rsa-sha2-512": {"hostkey_size": 4096}, "rsa-sha2-512-cert-v01@openssh.com": {"ca_key_size": 4096, "ca_key_type": "ssh-rsa", "hostkey_size": 4096}, "sk-ssh-ed25519-cert-v01@openssh.com": {"ca_key_size": 256, "ca_key_type": "ssh-ed25519", "hostkey_size": 256}, "sk-ssh-ed25519@openssh.com": {"hostkey_size": 256}, "ssh-ed25519": {"hostkey_size": 256}, "ssh-ed25519-cert-v01@openssh.com": {"ca_key_size": 256, "ca_key_type": "ssh-ed25519", "hostkey_size": 256}}, 'dh_modulus_sizes': {'diffie-hellman-group-exchange-sha256': 3072}, 'server_policy': True},
 
+    'Hardened Debian 13 (version 1)': {'version': '1', 'changelog': 'Initial revision.  As compared to the Debian 12 guide, the following changes were made: 1.) all non-post-quantum key exchanges were removed, and mlkem768x25519-sha256 and sntrup761x25519-sha512 were added, 2.) editing the /etc/ssh/moduli file is no longer done, as we no longer use any group-exchange algorithms (none of them currently protect against quantum attacks), 3.) editing the sshd_config file is no longer done, in order to make system upgrades easier for users, 4.) network-level connection throttling is no longer done, as OpenSSH prevents the DHEat attack by default now.', 'banner': None, 'compressions': None, 'host_keys': ['ssh-ed25519', 'rsa-sha2-512', 'rsa-sha2-256'], 'optional_host_keys': ['sk-ssh-ed25519@openssh.com', 'ssh-ed25519-cert-v01@openssh.com', 'sk-ssh-ed25519-cert-v01@openssh.com', 'rsa-sha2-256-cert-v01@openssh.com', 'rsa-sha2-512-cert-v01@openssh.com'], 'kex': ['mlkem768x25519-sha256', 'sntrup761x25519-sha512', 'sntrup761x25519-sha512@openssh.com', 'ext-info-s', 'kex-strict-s-v00@openssh.com'], 'ciphers': ['chacha20-poly1305@openssh.com', 'aes256-gcm@openssh.com', 'aes256-ctr', 'aes192-ctr', 'aes128-gcm@openssh.com', 'aes128-ctr'], 'macs': ['hmac-sha2-512-etm@openssh.com', 'hmac-sha2-256-etm@openssh.com', 'umac-128-etm@openssh.com'], 'hostkey_sizes': {"rsa-sha2-256": {"hostkey_size": 4096}, "rsa-sha2-256-cert-v01@openssh.com": {"ca_key_size": 4096, "ca_key_type": "ssh-rsa", "hostkey_size": 4096}, "rsa-sha2-512": {"hostkey_size": 4096}, "rsa-sha2-512-cert-v01@openssh.com": {"ca_key_size": 4096, "ca_key_type": "ssh-rsa", "hostkey_size": 4096}, "sk-ssh-ed25519-cert-v01@openssh.com": {"ca_key_size": 256, "ca_key_type": "ssh-ed25519", "hostkey_size": 256}, "sk-ssh-ed25519@openssh.com": {"hostkey_size": 256}, "ssh-ed25519": {"hostkey_size": 256}, "ssh-ed25519-cert-v01@openssh.com": {"ca_key_size": 256, "ca_key_type": "ssh-ed25519", "hostkey_size": 256}}, 'dh_modulus_sizes': {'diffie-hellman-group-exchange-sha256': 3072}, "allow_hostkey_subset_and_reordering": True, 'server_policy': True},
+
 
     # Rocky Linux 9
     'Hardened Rocky Linux 9 (version 1)': {'version': '1', 'changelog': 'Initial version', 'banner': None, 'compressions': None, 'host_keys': ['rsa-sha2-512', 'rsa-sha2-256', 'ssh-ed25519'], 'optional_host_keys': ['sk-ssh-ed25519@openssh.com', 'ssh-ed25519-cert-v01@openssh.com', 'sk-ssh-ed25519-cert-v01@openssh.com', 'rsa-sha2-256-cert-v01@openssh.com', 'rsa-sha2-512-cert-v01@openssh.com'], 'kex': ['sntrup761x25519-sha512@openssh.com', 'curve25519-sha256', 'curve25519-sha256@libssh.org', 'diffie-hellman-group16-sha512', 'diffie-hellman-group18-sha512', 'diffie-hellman-group-exchange-sha256', 'kex-strict-s-v00@openssh.com'], 'ciphers': ['chacha20-poly1305@openssh.com', 'aes256-gcm@openssh.com', 'aes128-gcm@openssh.com', 'aes256-ctr', 'aes192-ctr', 'aes128-ctr'], 'macs': ['hmac-sha2-256-etm@openssh.com', 'hmac-sha2-512-etm@openssh.com', 'umac-128-etm@openssh.com'], 'hostkey_sizes': {"rsa-sha2-256": {"hostkey_size": 4096}, "rsa-sha2-256-cert-v01@openssh.com": {"ca_key_size": 4096, "ca_key_type": "ssh-rsa", "hostkey_size": 4096}, "rsa-sha2-512": {"hostkey_size": 4096}, "rsa-sha2-512-cert-v01@openssh.com": {"ca_key_size": 4096, "ca_key_type": "ssh-rsa", "hostkey_size": 4096}, "sk-ssh-ed25519-cert-v01@openssh.com": {"ca_key_size": 256, "ca_key_type": "ssh-ed25519", "hostkey_size": 256}, "sk-ssh-ed25519@openssh.com": {"hostkey_size": 256}, "ssh-ed25519": {"hostkey_size": 256}, "ssh-ed25519-cert-v01@openssh.com": {"ca_key_size": 256, "ca_key_type": "ssh-ed25519", "hostkey_size": 256}}, 'dh_modulus_sizes': {'diffie-hellman-group-exchange-sha256': 3072}, 'server_policy': True},
@@ -57,6 +59,8 @@ BUILTIN_POLICIES: Dict[str, Dict[str, Union[Optional[str], Optional[List[str]],
 
     'Hardened Ubuntu Server 22.04 LTS (version 6)': {'version': '6', 'changelog': 'Re-ordered host keys to prioritize ED25519 due to efficiency. Re-ordered cipher list to prioritize larger key sizes as a countermeasure to quantum attacks.', 'banner': None, 'compressions': None, 'host_keys': ['ssh-ed25519', 'rsa-sha2-512', 'rsa-sha2-256'], 'optional_host_keys': ['sk-ssh-ed25519@openssh.com', 'ssh-ed25519-cert-v01@openssh.com', 'sk-ssh-ed25519-cert-v01@openssh.com', 'rsa-sha2-256-cert-v01@openssh.com', 'rsa-sha2-512-cert-v01@openssh.com'], 'kex': ['sntrup761x25519-sha512@openssh.com', 'curve25519-sha256', 'curve25519-sha256@libssh.org', 'diffie-hellman-group16-sha512', 'diffie-hellman-group18-sha512', 'diffie-hellman-group-exchange-sha256', 'kex-strict-s-v00@openssh.com'], 'ciphers': ['chacha20-poly1305@openssh.com', 'aes256-gcm@openssh.com', 'aes256-ctr', 'aes192-ctr', 'aes128-gcm@openssh.com', 'aes128-ctr'], 'macs': ['hmac-sha2-256-etm@openssh.com', 'hmac-sha2-512-etm@openssh.com', 'umac-128-etm@openssh.com'], 'hostkey_sizes': {"rsa-sha2-256": {"hostkey_size": 4096}, "rsa-sha2-256-cert-v01@openssh.com": {"ca_key_size": 4096, "ca_key_type": "ssh-rsa", "hostkey_size": 4096}, "rsa-sha2-512": {"hostkey_size": 4096}, "rsa-sha2-512-cert-v01@openssh.com": {"ca_key_size": 4096, "ca_key_type": "ssh-rsa", "hostkey_size": 4096}, "sk-ssh-ed25519-cert-v01@openssh.com": {"ca_key_size": 256, "ca_key_type": "ssh-ed25519", "hostkey_size": 256}, "sk-ssh-ed25519@openssh.com": {"hostkey_size": 256}, "ssh-ed25519": {"hostkey_size": 256}, "ssh-ed25519-cert-v01@openssh.com": {"ca_key_size": 256, "ca_key_type": "ssh-ed25519", "hostkey_size": 256}}, 'dh_modulus_sizes': {'diffie-hellman-group-exchange-sha256': 3072}, 'server_policy': True},
 
+    'Hardened Ubuntu Server 24.04 LTS (version 2)': {'version': '2', 'changelog': 'Removed commands directly editing sshd_config to make system updates easier for users.', 'banner': None, 'compressions': None, 'host_keys': ['ssh-ed25519', 'rsa-sha2-512', 'rsa-sha2-256'], 'optional_host_keys': ['sk-ssh-ed25519@openssh.com', 'ssh-ed25519-cert-v01@openssh.com', 'sk-ssh-ed25519-cert-v01@openssh.com', 'rsa-sha2-256-cert-v01@openssh.com', 'rsa-sha2-512-cert-v01@openssh.com'], 'kex': ['sntrup761x25519-sha512@openssh.com', 'curve25519-sha256', 'curve25519-sha256@libssh.org', 'diffie-hellman-group18-sha512', 'diffie-hellman-group-exchange-sha256', 'diffie-hellman-group16-sha512', 'ext-info-s', 'kex-strict-s-v00@openssh.com'], 'ciphers': ['chacha20-poly1305@openssh.com', 'aes256-gcm@openssh.com', 'aes256-ctr', 'aes192-ctr', 'aes128-gcm@openssh.com', 'aes128-ctr'], 'macs': ['hmac-sha2-512-etm@openssh.com', 'hmac-sha2-256-etm@openssh.com', 'umac-128-etm@openssh.com'], 'hostkey_sizes': {"rsa-sha2-256": {"hostkey_size": 4096}, "rsa-sha2-256-cert-v01@openssh.com": {"ca_key_size": 4096, "ca_key_type": "ssh-rsa", "hostkey_size": 4096}, "rsa-sha2-512": {"hostkey_size": 4096}, "rsa-sha2-512-cert-v01@openssh.com": {"ca_key_size": 4096, "ca_key_type": "ssh-rsa", "hostkey_size": 4096}, "sk-ssh-ed25519-cert-v01@openssh.com": {"ca_key_size": 256, "ca_key_type": "ssh-ed25519", "hostkey_size": 256}, "sk-ssh-ed25519@openssh.com": {"hostkey_size": 256}, "ssh-ed25519": {"hostkey_size": 256}, "ssh-ed25519-cert-v01@openssh.com": {"ca_key_size": 256, "ca_key_type": "ssh-ed25519", "hostkey_size": 256}}, 'dh_modulus_sizes': {'diffie-hellman-group-exchange-sha256': 3072}, "allow_hostkey_subset_and_reordering": True, "server_policy": True},
+
     'Hardened Ubuntu Server 24.04 LTS (version 1)': {'version': '1', 'changelog': 'Initial version.', 'banner': None, 'compressions': None, 'host_keys': ['ssh-ed25519', 'rsa-sha2-512', 'rsa-sha2-256'], 'optional_host_keys': ['sk-ssh-ed25519@openssh.com', 'ssh-ed25519-cert-v01@openssh.com', 'sk-ssh-ed25519-cert-v01@openssh.com', 'rsa-sha2-256-cert-v01@openssh.com', 'rsa-sha2-512-cert-v01@openssh.com'], 'kex': ['sntrup761x25519-sha512@openssh.com', 'curve25519-sha256', 'curve25519-sha256@libssh.org', 'diffie-hellman-group18-sha512', 'diffie-hellman-group-exchange-sha256', 'diffie-hellman-group16-sha512', 'ext-info-s', 'kex-strict-s-v00@openssh.com'], 'ciphers': ['chacha20-poly1305@openssh.com', 'aes256-gcm@openssh.com', 'aes256-ctr', 'aes192-ctr', 'aes128-gcm@openssh.com', 'aes128-ctr'], 'macs': ['hmac-sha2-512-etm@openssh.com', 'hmac-sha2-256-etm@openssh.com', 'umac-128-etm@openssh.com'], 'hostkey_sizes': {"rsa-sha2-256": {"hostkey_size": 4096}, "rsa-sha2-256-cert-v01@openssh.com": {"ca_key_size": 4096, "ca_key_type": "ssh-rsa", "hostkey_size": 4096}, "rsa-sha2-512": {"hostkey_size": 4096}, "rsa-sha2-512-cert-v01@openssh.com": {"ca_key_size": 4096, "ca_key_type": "ssh-rsa", "hostkey_size": 4096}, "sk-ssh-ed25519-cert-v01@openssh.com": {"ca_key_size": 256, "ca_key_type": "ssh-ed25519", "hostkey_size": 256}, "sk-ssh-ed25519@openssh.com": {"hostkey_size": 256}, "ssh-ed25519": {"hostkey_size": 256}, "ssh-ed25519-cert-v01@openssh.com": {"ca_key_size": 256, "ca_key_type": "ssh-ed25519", "hostkey_size": 256}}, 'dh_modulus_sizes': {'diffie-hellman-group-exchange-sha256': 3072}, 'server_policy': True},
 
     # Generic OpenSSH Server policies
@@ -107,6 +111,8 @@ BUILTIN_POLICIES: Dict[str, Dict[str, Union[Optional[str], Optional[List[str]],
 
     'Hardened OpenSSH Server v9.9 (version 1)': {'version': '1', 'changelog': 'Initial version.', 'banner': None, 'compressions': None, 'host_keys': ['rsa-sha2-512', 'rsa-sha2-256', 'ssh-ed25519'], 'optional_host_keys': ['sk-ssh-ed25519@openssh.com', 'ssh-ed25519-cert-v01@openssh.com', 'sk-ssh-ed25519-cert-v01@openssh.com', 'rsa-sha2-256-cert-v01@openssh.com', 'rsa-sha2-512-cert-v01@openssh.com'], 'kex': ['sntrup761x25519-sha512', 'sntrup761x25519-sha512@openssh.com', 'mlkem768x25519-sha256', 'curve25519-sha256', 'curve25519-sha256@libssh.org', 'diffie-hellman-group16-sha512', 'diffie-hellman-group18-sha512', 'diffie-hellman-group-exchange-sha256', 'ext-info-s', 'kex-strict-s-v00@openssh.com'], 'ciphers': ['chacha20-poly1305@openssh.com', 'aes256-gcm@openssh.com', 'aes128-gcm@openssh.com', 'aes256-ctr', 'aes192-ctr', 'aes128-ctr'], 'macs': ['hmac-sha2-256-etm@openssh.com', 'hmac-sha2-512-etm@openssh.com', 'umac-128-etm@openssh.com'], 'hostkey_sizes': {"rsa-sha2-256": {"hostkey_size": 4096}, "rsa-sha2-256-cert-v01@openssh.com": {"ca_key_size": 4096, "ca_key_type": "ssh-rsa", "hostkey_size": 4096}, "rsa-sha2-512": {"hostkey_size": 4096}, "rsa-sha2-512-cert-v01@openssh.com": {"ca_key_size": 4096, "ca_key_type": "ssh-rsa", "hostkey_size": 4096}, "sk-ssh-ed25519-cert-v01@openssh.com": {"ca_key_size": 256, "ca_key_type": "ssh-ed25519", "hostkey_size": 256}, "sk-ssh-ed25519@openssh.com": {"hostkey_size": 256}, "ssh-ed25519": {"hostkey_size": 256}, "ssh-ed25519-cert-v01@openssh.com": {"ca_key_size": 256, "ca_key_type": "ssh-ed25519", "hostkey_size": 256}}, 'dh_modulus_sizes': {'diffie-hellman-group-exchange-sha256': 3072}, 'server_policy': True},
 
+    'Hardened OpenSSH Server v10.0 (version 1)': {'version': '1', 'changelog': 'Initial version.', 'banner': None, 'compressions': None, 'host_keys': ['rsa-sha2-512', 'rsa-sha2-256', 'ssh-ed25519'], 'optional_host_keys': ['sk-ssh-ed25519@openssh.com', 'ssh-ed25519-cert-v01@openssh.com', 'sk-ssh-ed25519-cert-v01@openssh.com', 'rsa-sha2-256-cert-v01@openssh.com', 'rsa-sha2-512-cert-v01@openssh.com'], 'kex': ['mlkem768x25519-sha256', 'sntrup761x25519-sha512', 'sntrup761x25519-sha512@openssh.com', 'ext-info-s', 'kex-strict-s-v00@openssh.com'], 'ciphers': ['chacha20-poly1305@openssh.com', 'aes256-gcm@openssh.com', 'aes256-ctr', 'aes192-ctr', 'aes128-gcm@openssh.com', 'aes128-ctr'], 'macs': ['hmac-sha2-512-etm@openssh.com', 'hmac-sha2-256-etm@openssh.com', 'umac-128-etm@openssh.com'], 'hostkey_sizes': {"rsa-sha2-256": {"hostkey_size": 4096}, "rsa-sha2-256-cert-v01@openssh.com": {"ca_key_size": 4096, "ca_key_type": "ssh-rsa", "hostkey_size": 4096}, "rsa-sha2-512": {"hostkey_size": 4096}, "rsa-sha2-512-cert-v01@openssh.com": {"ca_key_size": 4096, "ca_key_type": "ssh-rsa", "hostkey_size": 4096}, "sk-ssh-ed25519-cert-v01@openssh.com": {"ca_key_size": 256, "ca_key_type": "ssh-ed25519", "hostkey_size": 256}, "sk-ssh-ed25519@openssh.com": {"hostkey_size": 256}, "ssh-ed25519": {"hostkey_size": 256}, "ssh-ed25519-cert-v01@openssh.com": {"ca_key_size": 256, "ca_key_type": "ssh-ed25519", "hostkey_size": 256}}, 'dh_modulus_sizes': {}, 'server_policy': True},
+
     # Amazon Linux Policies
 
     'Hardened Amazon Linux Client 2023 (version 1)': {'version': '1', 'changelog': 'Initial version.', 'banner': None, 'compressions': None, 'host_keys': ['sk-ssh-ed25519-cert-v01@openssh.com', 'ssh-ed25519-cert-v01@openssh.com', 'rsa-sha2-512-cert-v01@openssh.com', 'rsa-sha2-256-cert-v01@openssh.com', 'sk-ssh-ed25519@openssh.com', 'ssh-ed25519', 'rsa-sha2-512', 'rsa-sha2-256'], 'optional_host_keys': None, 'kex': ['sntrup761x25519-sha512@openssh.com', 'curve25519-sha256', 'curve25519-sha256@libssh.org', 'diffie-hellman-group16-sha512', 'diffie-hellman-group18-sha512', 'diffie-hellman-group-exchange-sha256', 'ext-info-c', 'kex-strict-c-v00@openssh.com'], 'ciphers': ['chacha20-poly1305@openssh.com', 'aes256-gcm@openssh.com', 'aes128-gcm@openssh.com', 'aes256-ctr', 'aes192-ctr', 'aes128-ctr'], 'macs': ['hmac-sha2-256-etm@openssh.com', 'hmac-sha2-512-etm@openssh.com', 'umac-128-etm@openssh.com'], 'hostkey_sizes': None, 'dh_modulus_sizes': None, 'server_policy': False},
@@ -120,6 +126,8 @@ BUILTIN_POLICIES: Dict[str, Dict[str, Union[Optional[str], Optional[List[str]],
 
     'Hardened Debian Client 12 (version 2)': {'version': '2', 'changelog': 'Re-ordered cipher list to prioritize larger key sizes as a countermeasure to quantum attacks.', 'banner': None, 'compressions': None, 'host_keys': ['sk-ssh-ed25519-cert-v01@openssh.com', 'ssh-ed25519-cert-v01@openssh.com', 'rsa-sha2-512-cert-v01@openssh.com', 'rsa-sha2-256-cert-v01@openssh.com', 'sk-ssh-ed25519@openssh.com', 'ssh-ed25519', 'rsa-sha2-512', 'rsa-sha2-256'], 'optional_host_keys': None, 'kex': ['sntrup761x25519-sha512@openssh.com', 'curve25519-sha256', 'curve25519-sha256@libssh.org', 'diffie-hellman-group16-sha512', 'diffie-hellman-group18-sha512', 'diffie-hellman-group-exchange-sha256', 'ext-info-c', 'kex-strict-c-v00@openssh.com'], 'ciphers': ['chacha20-poly1305@openssh.com', 'aes256-gcm@openssh.com', 'aes256-ctr', 'aes192-ctr', 'aes128-gcm@openssh.com', 'aes128-ctr'], 'macs': ['hmac-sha2-256-etm@openssh.com', 'hmac-sha2-512-etm@openssh.com', 'umac-128-etm@openssh.com'], 'hostkey_sizes': None, 'dh_modulus_sizes': None, 'server_policy': False},
 
+    'Hardened Debian Client 13 (version 1)': {'version': '1', 'changelog': 'Initial revision.  As compared to the Debian 12 guide, the following changes were made: all non-post-quantum key exchanges were removed, and mlkem768x25519-sha256 and sntrup761x25519-sha512 were added.', 'banner': None, 'compressions': None, 'host_keys': ['sk-ssh-ed25519-cert-v01@openssh.com', 'ssh-ed25519-cert-v01@openssh.com', 'rsa-sha2-512-cert-v01@openssh.com', 'rsa-sha2-256-cert-v01@openssh.com', 'sk-ssh-ed25519@openssh.com', 'ssh-ed25519', 'rsa-sha2-512', 'rsa-sha2-256'], 'optional_host_keys': None, 'kex': ['mlkem768x25519-sha256', 'sntrup761x25519-sha512', 'sntrup761x25519-sha512@openssh.com', 'ext-info-c', 'kex-strict-c-v00@openssh.com'], 'ciphers': ['chacha20-poly1305@openssh.com', 'aes256-gcm@openssh.com', 'aes256-ctr', 'aes192-ctr', 'aes128-gcm@openssh.com', 'aes128-ctr'], 'macs': ['hmac-sha2-512-etm@openssh.com', 'hmac-sha2-256-etm@openssh.com', 'umac-128-etm@openssh.com'], 'hostkey_sizes': None, 'dh_modulus_sizes': None, 'server_policy': False},
+
 
     # Rocky Linux Policies
 

src/ssh_audit/gextest.py

@@ -30,6 +30,7 @@ from typing import Callable, Optional, Union, Any  # noqa: F401
 
 from ssh_audit.banner import Banner
 from ssh_audit.kexdh import KexDHException, KexGroupExchange, KexGroupExchange_SHA1, KexGroupExchange_SHA256
+from ssh_audit.software import Software
 from ssh_audit.ssh2_kexdb import SSH2_KexDB
 from ssh_audit.ssh2_kex import SSH2_Kex
 from ssh_audit.ssh_socket import SSH_Socket
@@ -158,9 +159,22 @@ class GEXTest:
 
                     smallest_modulus, reconnect_failed = GEXTest._send_init(out, s, kex_group, kex, gex_alg, bits, bits, bits)
 
-                # If the smallest modulus is 2048 and the server is OpenSSH, then we may have triggered the fallback mechanism, which tends to happen in testing scenarios such as this but not in most real-world conditions (see X).  To better test this condition, we will do an additional check to see if the server supports sizes between 2048 and 4096, and consider this the definitive result.
+                # If the banner exists, then parse it into a Software object.  Next, if the target host is OpenSSH, check if its version is 9.9 or less; these versions are known to have a GEX fallback mechanism.
+                software = None if banner is None else Software.parse(banner)
+                is_openssh = False
+                has_fallback_mechanism = False
+                if (software is not None) and (software.product == "OpenSSH"):
+                    is_openssh = True
+                    try:
+                        if float(software.version) <= 9.9:
+                            has_fallback_mechanism = True
+                            out.d(f"Found version of OpenSSH that includes GEX fallback mechanism: {software}")
+                    except ValueError:
+                        pass
+
+                # If the smallest modulus is 2048 and the server is OpenSSH v9.9 or less, then we may have triggered the fallback mechanism, which tends to happen in testing scenarios such as this but not in most real-world conditions.  To better test this condition, we will do an additional check to see if the server supports sizes between 2048 and 4096, and consider this the definitive result.
                 openssh_test_updated = False
-                if (smallest_modulus == 2048) and (banner is not None) and (banner.software is not None) and (banner.software.find('OpenSSH') != -1):
+                if (smallest_modulus == 2048) and is_openssh and has_fallback_mechanism:
                     out.d('First pass found a minimum GEX modulus of 2048 against OpenSSH server.  Performing a second pass to get a more accurate result...')
                     smallest_modulus, _ = GEXTest._send_init(out, s, kex_group, kex, gex_alg, 2048, 3072, 4096)
                     out.d('Modulus size returned by server during second pass: %d bits' % smallest_modulus, write_now=True)

src/ssh_audit/hardening_guides.py

@@ -0,0 +1,687 @@
+"""
+   The MIT License (MIT)
+
+   Copyright (C) 2025 Joe Testa (jtesta@positronsecurity.com)
+
+   Permission is hereby granted, free of charge, to any person obtaining a copy
+   of this software and associated documentation files (the "Software"), to deal
+   in the Software without restriction, including without limitation the rights
+   to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+   copies of the Software, and to permit persons to whom the Software is
+   furnished to do so, subject to the following conditions:
+
+   The above copyright notice and this permission notice shall be included in
+   all copies or substantial portions of the Software.
+
+   THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+   IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+   FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+   AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+   LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+   OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+   THE SOFTWARE.
+"""
+from typing import Any, Dict
+
+from ssh_audit.outputbuffer import OutputBuffer
+
+
+class Hardening_Guides:
+
+    HARDENING_GUIDES: Dict[str, Any] = {
+        "Amazon Linux 2023": [
+            {
+                "server_guide": True,
+                "version": 3,
+                "version_date": "2024-10-01",
+                "change_log": "Re-ordered host keys to prioritize ED25519 due to efficiency. Re-ordered cipher list to prioritize larger key sizes as a countermeasure to quantum attacks.",
+                "notes": "all commands below are to be executed as the root user.",
+                "commands": [
+                    {
+                        "heading": "Re-generate the RSA and ED25519 keys",
+                        "comment": "",
+                        "command": "rm -f /etc/ssh/ssh_host_*\nssh-keygen -t rsa -b 4096 -f /etc/ssh/ssh_host_rsa_key -N \"\"\nssh-keygen -t ed25519 -f /etc/ssh/ssh_host_ed25519_key -N \"\""
+                    },
+                    {
+                        "heading": "Enable the ED25519 and RSA keys",
+                        "comment": "Enable the ED25519 and RSA HostKey directives in the /etc/ssh/sshd_config file:",
+                        "command": "echo -e \"\\nHostKey /etc/ssh/ssh_host_ed25519_key\\nHostKey /etc/ssh/ssh_host_rsa_key\" >> /etc/ssh/sshd_config"
+                    },
+                    {
+                        "heading": "Remove small Diffie-Hellman moduli",
+                        "comment": "",
+                        "command": "awk '$5 >= 3071' /etc/ssh/moduli > /etc/ssh/moduli.safe\nmv -f /etc/ssh/moduli.safe /etc/ssh/moduli"
+                    },
+                    {
+                        "heading": "Restrict supported key exchange, cipher, and MAC algorithms",
+                        "comment": "",
+                        "command": "echo -e \"# Restrict key exchange, cipher, and MAC algorithms, as per sshaudit.com hardening guide.\\nKexAlgorithms sntrup761x25519-sha512@openssh.com,curve25519-sha256,curve25519-sha256@libssh.org,gss-curve25519-sha256-,diffie-hellman-group16-sha512,gss-group16-sha512-,diffie-hellman-group18-sha512,diffie-hellman-group-exchange-sha256\\n\\nCiphers chacha20-poly1305@openssh.com,aes256-gcm@openssh.com,aes256-ctr,aes192-ctr,aes128-gcm@openssh.com,aes128-ctr\\n\\nMACs hmac-sha2-256-etm@openssh.com,hmac-sha2-512-etm@openssh.com,umac-128-etm@openssh.com\\n\\nHostKeyAlgorithms sk-ssh-ed25519-cert-v01@openssh.com,ssh-ed25519-cert-v01@openssh.com,rsa-sha2-512-cert-v01@openssh.com,rsa-sha2-256-cert-v01@openssh.com,sk-ssh-ed25519@openssh.com,ssh-ed25519,rsa-sha2-512,rsa-sha2-256\\n\\nCASignatureAlgorithms sk-ssh-ed25519@openssh.com,ssh-ed25519,rsa-sha2-512,rsa-sha2-256\\n\\nGSSAPIKexAlgorithms gss-curve25519-sha256-,gss-group16-sha512-\\n\\nHostbasedAcceptedAlgorithms sk-ssh-ed25519-cert-v01@openssh.com,ssh-ed25519-cert-v01@openssh.com,sk-ssh-ed25519@openssh.com,ssh-ed25519,rsa-sha2-512-cert-v01@openssh.com,rsa-sha2-512,rsa-sha2-256-cert-v01@openssh.com,rsa-sha2-256\\n\\nPubkeyAcceptedAlgorithms sk-ssh-ed25519-cert-v01@openssh.com,ssh-ed25519-cert-v01@openssh.com,rsa-sha2-512-cert-v01@openssh.com,rsa-sha2-256-cert-v01@openssh.com,sk-ssh-ed25519@openssh.com,ssh-ed25519,rsa-sha2-512,rsa-sha2-256\\n\\n\" > /etc/crypto-policies/back-ends/opensshserver.config"
+                    },
+                    {
+                        "heading": "Restart OpenSSH server",
+                        "comment": "",
+                        "command": "systemctl restart sshd"
+                    },
+                    {
+                        "heading": "Implement connection rate throttling",
+                        "comment": "Connection rate throttling is needed in order to protect against the DHEat denial-of-service attack. A complete and flexible solution is to use iptables to allow up to 10 connections every 10 seconds from any one source address. An alternate solution is to set OpenSSH's PerSourceMaxStartups directive to 1 (note, however, that this can cause incomplete results during ssh-audit scans, as well as other client failures when bursts of connections are made).",
+                        "command": "dnf install -y iptables\niptables -I INPUT -p tcp --dport 22 -m state --state NEW -m recent --set\niptables -I INPUT -p tcp --dport 22 -m state --state NEW -m recent --update --seconds 10 --hitcount 10 -j DROP\nip6tables -I INPUT -p tcp --dport 22 -m state --state NEW -m recent --set\nip6tables -I INPUT -p tcp --dport 22 -m state --state NEW -m recent --update --seconds 10 --hitcount 10 -j DROP\ndnf install -y iptables-services\niptables-save > /etc/sysconfig/iptables\nip6tables-save > /etc/sysconfig/ip6tables\nsystemctl enable iptables\nsystemctl enable ip6tables\nsystemctl start iptables\nsystemctl start ip6tables"
+                    },
+                ]
+            },
+            {
+                "server_guide": True,
+                "version": 2,
+                "version_date": "2024-04-22",
+                "change_log": "Added connection throttling instructions to counteract the DHEat denial-of-service attack.",
+                "notes": "",
+                "commands": []  # Commands for this older version are not tracked here.
+            },
+            {
+                "server_guide": True,
+                "version": 1,
+                "version_date": "2024-03-15",
+                "change_log": "Initial revision.",
+                "notes": "",
+                "commands": []  # Commands for this older version are not tracked here.
+            },
+            {
+                "server_guide": False,
+                "version": 3,
+                "version_date": "2024-10-01",
+                "change_log": "Re-ordered cipher list to prioritize larger key sizes as a countermeasure to quantum attacks.",
+                "notes": "",
+                "commands": [
+                    {
+                        "heading": "Run the following in a terminal to harden the SSH client for the local user:",
+                        "comment": "",
+                        "command": "mkdir -p -m 0700 ~/.ssh; echo -e \"\\nHost *\\n Ciphers chacha20-poly1305@openssh.com,aes256-gcm@openssh.com,aes256-ctr,aes192-ctr,aes128-gcm@openssh.com,aes128-ctr\\n\\n KexAlgorithms sntrup761x25519-sha512@openssh.com,gss-curve25519-sha256-,curve25519-sha256,curve25519-sha256@libssh.org,gss-group16-sha512-,diffie-hellman-group16-sha512,diffie-hellman-group18-sha512,diffie-hellman-group-exchange-sha256\\n\\n MACs hmac-sha2-256-etm@openssh.com,hmac-sha2-512-etm@openssh.com,umac-128-etm@openssh.com\\n\\n HostKeyAlgorithms sk-ssh-ed25519-cert-v01@openssh.com,ssh-ed25519-cert-v01@openssh.com,rsa-sha2-512-cert-v01@openssh.com,rsa-sha2-256-cert-v01@openssh.com,sk-ssh-ed25519@openssh.com,ssh-ed25519,rsa-sha2-512,rsa-sha2-256\\n\\n CASignatureAlgorithms sk-ssh-ed25519@openssh.com,ssh-ed25519,rsa-sha2-512,rsa-sha2-256\\n\\n GSSAPIKexAlgorithms gss-curve25519-sha256-,gss-group16-sha512-\\n\\n HostbasedAcceptedAlgorithms sk-ssh-ed25519-cert-v01@openssh.com,ssh-ed25519-cert-v01@openssh.com,sk-ssh-ed25519@openssh.com,ssh-ed25519,rsa-sha2-512-cert-v01@openssh.com,rsa-sha2-512,rsa-sha2-256-cert-v01@openssh.com,rsa-sha2-256\\n\\n PubkeyAcceptedAlgorithms sk-ssh-ed25519-cert-v01@openssh.com,ssh-ed25519-cert-v01@openssh.com,sk-ssh-ed25519@openssh.com,ssh-ed25519,rsa-sha2-512-cert-v01@openssh.com,rsa-sha2-512,rsa-sha2-256-cert-v01@openssh.com,rsa-sha2-256\\n\\n\" >> ~/.ssh/config"
+                    },
+                ]
+            },
+            {
+                "server_guide": False,
+                "version": 2,
+                "version_date": "2024-04-22",
+                "change_log": "added connection throttling instructions to counteract the DHEat denial-of-service attack.",
+                "notes": "",
+                "commands": []  # Commands for this older version are not tracked here.
+            },
+            {
+                "server_guide": False,
+                "version": 1,
+                "version_date": "2024-03-15",
+                "change_log": "Initial revision.",
+                "notes": "",
+                "commands": []  # Commands for this older version are not tracked here.
+            },
+        ],
+
+        "Debian 11": [
+            {
+                "server_guide": True,
+                "version": 1,
+                "version_date": "2021-09-17",
+                "change_log": "Latest version.",
+                "notes": "all commands below are to be executed as the root user.",
+                "commands": [
+                    {
+                        "heading": "Re-generate the RSA and ED25519 keys",
+                        "comment": "",
+                        "command": "rm -f /etc/ssh/ssh_host_*\nssh-keygen -t rsa -b 4096 -f /etc/ssh/ssh_host_rsa_key -N \"\"\nssh-keygen -t ed25519 -f /etc/ssh/ssh_host_ed25519_key -N \"\""
+                    },
+                    {
+                        "heading": "Enable the RSA and ED25519 keys",
+                        "comment": "Enable the RSA and ED25519 HostKey directives in the /etc/ssh/sshd_config file:",
+                        "command": "sed -i 's/^\\#HostKey \\/etc\\/ssh\\/ssh_host_\\(rsa\\|ed25519\\)_key$/HostKey \\/etc\\/ssh\\/ssh_host_\\1_key/g' /etc/ssh/sshd_config"
+                    },
+                    {
+                        "heading": "Remove small Diffie-Hellman moduli",
+                        "comment": "",
+                        "command": "awk '$5 >= 3071' /etc/ssh/moduli > /etc/ssh/moduli.safe\nmv -f /etc/ssh/moduli.safe /etc/ssh/moduli"
+                    },
+                    {
+                        "heading": "Restrict supported key exchange, cipher, and MAC algorithms",
+                        "comment": "",
+                        "command": "echo -e \"\\n# Restrict key exchange, cipher, and MAC algorithms, as per sshaudit.com\\n# hardening guide.\\nKexAlgorithms curve25519-sha256,curve25519-sha256@libssh.org,diffie-hellman-group16-sha512,diffie-hellman-group18-sha512,diffie-hellman-group-exchange-sha256\\nCiphers chacha20-poly1305@openssh.com,aes256-gcm@openssh.com,aes128-gcm@openssh.com,aes256-ctr,aes192-ctr,aes128-ctr\\nMACs hmac-sha2-256-etm@openssh.com,hmac-sha2-512-etm@openssh.com,umac-128-etm@openssh.com\\nHostKeyAlgorithms ssh-ed25519,ssh-ed25519-cert-v01@openssh.com,sk-ssh-ed25519@openssh.com,sk-ssh-ed25519-cert-v01@openssh.com,rsa-sha2-256,rsa-sha2-512,rsa-sha2-256-cert-v01@openssh.com,rsa-sha2-512-cert-v01@openssh.com\" > /etc/ssh/sshd_config.d/ssh-audit_hardening.conf"
+                    },
+                    {
+                        "heading": "Restart OpenSSH server",
+                        "comment": "",
+                        "command": "service ssh restart"
+                    },
+                ]
+            },
+        ],
+
+        "Debian 12": [
+            {
+                "server_guide": True,
+                "version": 3,
+                "version_date": "2025-04-18",
+                "change_log": "Added sntrup761x25519-sha512 to KexAlgorithms.",
+                "notes": "all commands below are to be executed as the root user.",
+                "commands": [
+                    {
+                        "heading": "Re-generate the RSA and ED25519 keys",
+                        "comment": "",
+                        "command": "rm /etc/ssh/ssh_host_*\nssh-keygen -t rsa -b 4096 -f /etc/ssh/ssh_host_rsa_key -N \"\"\nssh-keygen -t ed25519 -f /etc/ssh/ssh_host_ed25519_key -N \"\""
+                    },
+                    {
+                        "heading": "Enable the ED25519 and RSA keys",
+                        "comment": "Enable the ED25519 and RSA HostKey directives in the /etc/ssh/sshd_config file:",
+                        "command": "echo -e \"\\nHostKey /etc/ssh/ssh_host_ed25519_key\\nHostKey /etc/ssh/ssh_host_rsa_key\" >> /etc/ssh/sshd_config"
+                    },
+                    {
+                        "heading": "Remove small Diffie-Hellman moduli",
+                        "comment": "",
+                        "command": "awk '$5 >= 3071' /etc/ssh/moduli > /etc/ssh/moduli.safe\nmv /etc/ssh/moduli.safe /etc/ssh/moduli"
+                    },
+                    {
+                        "heading": "Restrict supported key exchange, cipher, and MAC algorithms",
+                        "comment": "",
+                        "command": "echo -e \"# Restrict key exchange, cipher, and MAC algorithms, as per sshaudit.com\\n# hardening guide.\\n KexAlgorithms sntrup761x25519-sha512,sntrup761x25519-sha512@openssh.com,curve25519-sha256,curve25519-sha256@libssh.org,gss-curve25519-sha256-,diffie-hellman-group16-sha512,gss-group16-sha512-,diffie-hellman-group18-sha512,diffie-hellman-group-exchange-sha256\\n\\nCiphers chacha20-poly1305@openssh.com,aes256-gcm@openssh.com,aes256-ctr,aes192-ctr,aes128-gcm@openssh.com,aes128-ctr\\n\\nMACs hmac-sha2-256-etm@openssh.com,hmac-sha2-512-etm@openssh.com,umac-128-etm@openssh.com\\n\\nHostKeyAlgorithms sk-ssh-ed25519-cert-v01@openssh.com,ssh-ed25519-cert-v01@openssh.com,rsa-sha2-512-cert-v01@openssh.com,rsa-sha2-256-cert-v01@openssh.com,sk-ssh-ed25519@openssh.com,ssh-ed25519,rsa-sha2-512,rsa-sha2-256\\n\\nRequiredRSASize 3072\\n\\nCASignatureAlgorithms sk-ssh-ed25519@openssh.com,ssh-ed25519,rsa-sha2-512,rsa-sha2-256\\n\\nGSSAPIKexAlgorithms gss-curve25519-sha256-,gss-group16-sha512-\\n\\nHostbasedAcceptedAlgorithms sk-ssh-ed25519-cert-v01@openssh.com,ssh-ed25519-cert-v01@openssh.com,sk-ssh-ed25519@openssh.com,ssh-ed25519,rsa-sha2-512-cert-v01@openssh.com,rsa-sha2-512,rsa-sha2-256-cert-v01@openssh.com,rsa-sha2-256\\n\\nPubkeyAcceptedAlgorithms sk-ssh-ed25519-cert-v01@openssh.com,ssh-ed25519-cert-v01@openssh.com,sk-ssh-ed25519@openssh.com,ssh-ed25519,rsa-sha2-512-cert-v01@openssh.com,rsa-sha2-512,rsa-sha2-256-cert-v01@openssh.com,rsa-sha2-256\\n\\n\" > /etc/ssh/sshd_config.d/ssh-audit_hardening.conf"
+                    },
+                    {
+                        "heading": "Restart OpenSSH server",
+                        "comment": "",
+                        "command": "service ssh restart"
+                    },
+                    {
+                        "heading": "Implement connection rate throttling",
+                        "comment": "Connection rate throttling is needed in order to protect against the DHEat denial-of-service attack. A complete and flexible solution is to use iptables to allow up to 10 connections every 10 seconds from any one source address. An alternate solution is to set OpenSSH's PerSourceMaxStartups directive to 1 (note, however, that this can cause incomplete results during ssh-audit scans, as well as other client failures when bursts of connections are made).",
+                        "command": "apt update\nDEBIAN_FRONTEND=noninteractive apt install -q -y iptables netfilter-persistent iptables-persistent\niptables -I INPUT -p tcp --dport 22 -m state --state NEW -m recent --set\niptables -I INPUT -p tcp --dport 22 -m state --state NEW -m recent --update --seconds 10 --hitcount 10 -j DROP\nip6tables -I INPUT -p tcp --dport 22 -m state --state NEW -m recent --set\nip6tables -I INPUT -p tcp --dport 22 -m state --state NEW -m recent --update --seconds 10 --hitcount 10 -j DROP\nservice netfilter-persistent save"
+                    },
+                ]
+            },
+            {
+                "server_guide": True,
+                "version": 2,
+                "version_date": "2024-10-01",
+                "change_log": "Re-ordered host keys to prioritize ED25519 due to efficiency. Re-ordered cipher list to prioritize larger key sizes as a countermeasure to quantum attacks.",
+                "notes": "",
+                "commands": []  # Commands for this older version are not tracked here.
+            },
+            {
+                "server_guide": True,
+                "version": 1,
+                "version_date": "2024-04-24",
+                "change_log": "Added connection throttling instructions to counteract the DHEat denial-of-service attack.",
+                "notes": "",
+                "commands": []  # Commands for this older version are not tracked here.
+            },
+            {
+                "server_guide": False,
+                "version": 2,
+                "version_date": "2024-10-01",
+                "change_log": "Added RequiredRSASize directive to enforce a minimum of 3072-bit user and host-based authentication keys. Re-ordered cipher list to prioritize larger key sizes as a countermeasure to quantum attacks.",
+                "notes": "",
+                "commands": [
+                    {
+                        "heading": "Run the following in a terminal to harden the SSH client for the local user:",
+                        "comment": "",
+                        "command": "mkdir -p -m 0700 ~/.ssh; echo -e \"\\nHost *\\n Ciphers chacha20-poly1305@openssh.com,aes256-gcm@openssh.com,aes256-ctr,aes192-ctr,aes128-gcm@openssh.com,aes128-ctr\\n\\n KexAlgorithms sntrup761x25519-sha512@openssh.com,gss-curve25519-sha256-,curve25519-sha256,curve25519-sha256@libssh.org,gss-group16-sha512-,diffie-hellman-group16-sha512,diffie-hellman-group18-sha512,diffie-hellman-group-exchange-sha256\\n\\n MACs hmac-sha2-256-etm@openssh.com,hmac-sha2-512-etm@openssh.com,umac-128-etm@openssh.com\\n\\n RequiredRSASize 3072\\n\\n HostKeyAlgorithms sk-ssh-ed25519-cert-v01@openssh.com,ssh-ed25519-cert-v01@openssh.com,rsa-sha2-512-cert-v01@openssh.com,rsa-sha2-256-cert-v01@openssh.com,sk-ssh-ed25519@openssh.com,ssh-ed25519,rsa-sha2-512,rsa-sha2-256\\n\\n CASignatureAlgorithms sk-ssh-ed25519@openssh.com,ssh-ed25519,rsa-sha2-512,rsa-sha2-256\\n\\n GSSAPIKexAlgorithms gss-curve25519-sha256-,gss-group16-sha512-\\n\\n HostbasedAcceptedAlgorithms sk-ssh-ed25519-cert-v01@openssh.com,ssh-ed25519-cert-v01@openssh.com,sk-ssh-ed25519@openssh.com,ssh-ed25519,rsa-sha2-512-cert-v01@openssh.com,rsa-sha2-512,rsa-sha2-256-cert-v01@openssh.com,rsa-sha2-256\\n\\n PubkeyAcceptedAlgorithms sk-ssh-ed25519-cert-v01@openssh.com,ssh-ed25519-cert-v01@openssh.com,sk-ssh-ed25519@openssh.com,ssh-ed25519,rsa-sha2-512-cert-v01@openssh.com,rsa-sha2-512,rsa-sha2-256-cert-v01@openssh.com,rsa-sha2-256\\n\\n\" >> ~/.ssh/config"
+                    },
+                ]
+            },
+            {
+                "server_guide": False,
+                "version": 1,
+                "version_date": "2024-03-15",
+                "change_log": "Initial revision.",
+                "notes": "",
+                "commands": []  # Commands for this older version are not tracked here.
+            },
+        ],
+
+        "Debian 13": [
+            {
+                "server_guide": True,
+                "version": 1,
+                "version_date": "2025-09-01",
+                "change_log": "Initial revision.  As compared to the Debian 12 guide, the following changes were made: 1.) all non-post-quantum key exchanges were removed, and mlkem768x25519-sha256 and sntrup761x25519-sha512 were added, 2.) editing the /etc/ssh/moduli file is no longer done, as we no longer use any group-exchange algorithms (none of them currently protect against quantum attacks), 3.) editing the sshd_config file is no longer done, in order to make system upgrades easier for users, 4.) network-level connection throttling is no longer done, as OpenSSH prevents the DHEat attack by default now.",
+                "notes": "all commands below are to be executed as the root user.",
+                "commands": [
+                    {
+                        "heading": "Re-generate the ED25519 and RSA keys",
+                        "comment": "",
+                        "command": "rm /etc/ssh/ssh_host_*\nssh-keygen -t ed25519 -f /etc/ssh/ssh_host_ed25519_key -N \"\"\nssh-keygen -t rsa -b 4096 -f /etc/ssh/ssh_host_rsa_key -N \"\""
+                    },
+                    {
+                        "heading": "Restrict supported key exchange, cipher, and MAC algorithms",
+                        "comment": "",
+                        "command": "echo -e \"# Restrict key exchange, cipher, and MAC algorithms, as per sshaudit.com\\n# hardening guide.\\nKexAlgorithms mlkem768x25519-sha256,sntrup761x25519-sha512,sntrup761x25519-sha512@openssh.com\\n\\nCiphers chacha20-poly1305@openssh.com,aes256-gcm@openssh.com,aes256-ctr,aes192-ctr,aes128-gcm@openssh.com,aes128-ctr\\n\\nMACs hmac-sha2-512-etm@openssh.com,hmac-sha2-256-etm@openssh.com,umac-128-etm@openssh.com\\n\\nRequiredRSASize 3072\\n\\nHostKeyAlgorithms sk-ssh-ed25519-cert-v01@openssh.com,ssh-ed25519-cert-v01@openssh.com,rsa-sha2-512-cert-v01@openssh.com,rsa-sha2-256-cert-v01@openssh.com,sk-ssh-ed25519@openssh.com,ssh-ed25519,rsa-sha2-512,rsa-sha2-256\\n\\nCASignatureAlgorithms sk-ssh-ed25519@openssh.com,ssh-ed25519,rsa-sha2-512,rsa-sha2-256\\n\\nGSSAPIKexAlgorithms gss-curve25519-sha256-,gss-group16-sha512-\\n\\nHostbasedAcceptedAlgorithms sk-ssh-ed25519-cert-v01@openssh.com,ssh-ed25519-cert-v01@openssh.com,rsa-sha2-512-cert-v01@openssh.com,rsa-sha2-256-cert-v01@openssh.com,sk-ssh-ed25519@openssh.com,ssh-ed25519,rsa-sha2-512,rsa-sha2-256\\n\\nPubkeyAcceptedAlgorithms sk-ssh-ed25519-cert-v01@openssh.com,ssh-ed25519-cert-v01@openssh.com,rsa-sha2-512-cert-v01@openssh.com,rsa-sha2-256-cert-v01@openssh.com,sk-ssh-ed25519@openssh.com,ssh-ed25519,rsa-sha2-512,rsa-sha2-256\" > /etc/ssh/sshd_config.d/debian13_ssh-audit_hardening.conf"
+                    },
+                    {
+                        "heading": "Restart OpenSSH server",
+                        "comment": "",
+                        "command": "service ssh restart"
+                    },
+                ]
+            },
+            {
+                "server_guide": False,
+                "version": 1,
+                "version_date": "2025-09-01",
+                "change_log": "Initial revision.  As compared to the Debian 12 guide, the following changes were made: all non-post-quantum key exchanges were removed.",
+                "notes": "",
+                "commands": [
+                    {
+                        "heading": "Run the following in a terminal to harden the SSH client for the local user:",
+                        "comment": "",
+                        "command": "mkdir -p -m 0700 ~/.ssh; echo -e \"\\nHost *\\n Ciphers chacha20-poly1305@openssh.com,aes256-gcm@openssh.com,aes256-ctr,aes192-ctr,aes128-gcm@openssh.com,aes128-ctr\\n\\n KexAlgorithms mlkem768x25519-sha256,sntrup761x25519-sha512,sntrup761x25519-sha512@openssh.com\\n\\n MACs hmac-sha2-512-etm@openssh.com,hmac-sha2-256-etm@openssh.com,umac-128-etm@openssh.com\\n\\n RequiredRSASize 3072\\n\\n HostKeyAlgorithms sk-ssh-ed25519-cert-v01@openssh.com,ssh-ed25519-cert-v01@openssh.com,rsa-sha2-512-cert-v01@openssh.com,rsa-sha2-256-cert-v01@openssh.com,sk-ssh-ed25519@openssh.com,ssh-ed25519,rsa-sha2-512,rsa-sha2-256\\n\\n CASignatureAlgorithms sk-ssh-ed25519@openssh.com,ssh-ed25519,rsa-sha2-512,rsa-sha2-256\\n\\n GSSAPIKexAlgorithms gss-curve25519-sha256-,gss-group16-sha512-\\n\\n HostbasedAcceptedAlgorithms sk-ssh-ed25519-cert-v01@openssh.com,ssh-ed25519-cert-v01@openssh.com,sk-ssh-ed25519@openssh.com,ssh-ed25519,rsa-sha2-512-cert-v01@openssh.com,rsa-sha2-512,rsa-sha2-256-cert-v01@openssh.com,rsa-sha2-256\\n\\n PubkeyAcceptedAlgorithms sk-ssh-ed25519-cert-v01@openssh.com,ssh-ed25519-cert-v01@openssh.com,sk-ssh-ed25519@openssh.com,ssh-ed25519,rsa-sha2-512-cert-v01@openssh.com,rsa-sha2-512,rsa-sha2-256-cert-v01@openssh.com,rsa-sha2-256\\n\\n\" >> ~/.ssh/config"
+                    },
+                ]
+            },
+        ],
+
+        "Rocky Linux 9": [
+            {
+                "server_guide": True,
+                "version": 2,
+                "version_date": "2024-10-01",
+                "change_log": "Re-ordered host keys to prioritize ED25519 due to efficiency. Re-ordered cipher list to prioritize larger key sizes as a countermeasure to quantum attacks.",
+                "notes": "all commands below are to be executed as the root user.",
+                "commands": [
+                    {
+                        "heading": "Re-generate the RSA and ED25519 keys",
+                        "comment": "",
+                        "command": "rm -f /etc/ssh/ssh_host_*\nssh-keygen -t rsa -b 4096 -f /etc/ssh/ssh_host_rsa_key -N \"\"\nssh-keygen -t ed25519 -f /etc/ssh/ssh_host_ed25519_key -N \"\""
+                    },
+                    {
+                        "heading": "Enable the ED25519 and RSA keys",
+                        "comment": "Enable the ED25519 and RSA HostKey directives in the /etc/ssh/sshd_config file:",
+                        "command": "echo -e \"\\nHostKey /etc/ssh/ssh_host_ed25519_key\\nHostKey /etc/ssh/ssh_host_rsa_key\" >> /etc/ssh/sshd_config"
+                    },
+                    {
+                        "heading": "Remove small Diffie-Hellman moduli",
+                        "comment": "",
+                        "command": "awk '$5 >= 3071' /etc/ssh/moduli > /etc/ssh/moduli.safe\nmv -f /etc/ssh/moduli.safe /etc/ssh/moduli"
+                    },
+                    {
+                        "heading": "Restrict supported key exchange, cipher, and MAC algorithms",
+                        "comment": "",
+                        "command": "echo -e \"# Restrict key exchange, cipher, and MAC algorithms, as per sshaudit.com\\n# hardening guide.\\nKexAlgorithms sntrup761x25519-sha512@openssh.com,curve25519-sha256,curve25519-sha256@libssh.org,gss-curve25519-sha256-,diffie-hellman-group16-sha512,gss-group16-sha512-,diffie-hellman-group18-sha512,diffie-hellman-group-exchange-sha256\\n\\nCiphers chacha20-poly1305@openssh.com,aes256-gcm@openssh.com,aes256-ctr,aes192-ctr,aes128-gcm@openssh.com,aes128-ctr\\n\\nMACs hmac-sha2-256-etm@openssh.com,hmac-sha2-512-etm@openssh.com,umac-128-etm@openssh.com\\n\\nHostKeyAlgorithms sk-ssh-ed25519-cert-v01@openssh.com,ssh-ed25519-cert-v01@openssh.com,rsa-sha2-512-cert-v01@openssh.com,rsa-sha2-256-cert-v01@openssh.com,sk-ssh-ed25519@openssh.com,ssh-ed25519,rsa-sha2-512,rsa-sha2-256\\n\\nRequiredRSASize 3072\\n\\nCASignatureAlgorithms sk-ssh-ed25519@openssh.com,ssh-ed25519,rsa-sha2-512,rsa-sha2-256\\n\\nGSSAPIKexAlgorithms gss-curve25519-sha256-,gss-group16-sha512-\\n\\nHostbasedAcceptedAlgorithms sk-ssh-ed25519-cert-v01@openssh.com,ssh-ed25519-cert-v01@openssh.com,sk-ssh-ed25519@openssh.com,ssh-ed25519,rsa-sha2-512-cert-v01@openssh.com,rsa-sha2-512,rsa-sha2-256-cert-v01@openssh.com,rsa-sha2-256\\n\\nPubkeyAcceptedAlgorithms sk-ssh-ed25519-cert-v01@openssh.com,ssh-ed25519-cert-v01@openssh.com,rsa-sha2-512-cert-v01@openssh.com,rsa-sha2-256-cert-v01@openssh.com,sk-ssh-ed25519@openssh.com,ssh-ed25519,rsa-sha2-512,rsa-sha2-256\\n\\n\" > /etc/crypto-policies/back-ends/opensshserver.config"
+                    },
+                    {
+                        "heading": "Restart OpenSSH server",
+                        "comment": "",
+                        "command": "systemctl restart sshd"
+                    },
+                    {
+                        "heading": "Implement connection rate throttling",
+                        "comment": "Connection rate throttling is needed in order to protect against the DHEat denial-of-service attack. A complete and flexible solution is to use iptables/firewalld to allow up to 10 connections every 10 seconds from any one source address. An alternate solution is to set OpenSSH's PerSourceMaxStartups directive to 1 (note, however, that this can cause incomplete results during ssh-audit scans, as well as other client failures when bursts of connections are made).",
+                        "command": "firewall-cmd --permanent --direct --add-rule ipv4 filter INPUT 0 -p tcp --dport 22 -m state --state NEW -m recent --set\nfirewall-cmd --permanent --direct --add-rule ipv4 filter INPUT 1 -p tcp --dport 22 -m state --state NEW -m recent --update --seconds 10 --hitcount 10 -j DROP\nfirewall-cmd --permanent --direct --add-rule ipv6 filter INPUT 0 -p tcp --dport 22 -m state --state NEW -m recent --set\nfirewall-cmd --permanent --direct --add-rule ipv6 filter INPUT 1 -p tcp --dport 22 -m state --state NEW -m recent --update --seconds 10 --hitcount 10 -j DROP\nsystemctl reload firewalld"
+                    },
+                ]
+            },
+            {
+                "server_guide": True,
+                "version": 1,
+                "version_date": "2024-04-24",
+                "change_log": "Added connection throttling instructions to counteract the DHEat denial-of-service attack.",
+                "notes": "",
+                "commands": []  # Commands for this older version are not tracked here.
+            },
+            {
+                "server_guide": False,
+                "version": 2,
+                "version_date": "2024-10-01",
+                "change_log": "Added RequiredRSASize directive to enforce a minimum of 3072-bit user and host-based authentication keys. Re-ordered cipher list to prioritize larger key sizes as a countermeasure to quantum attacks.",
+                "notes": "",
+                "commands": [
+                    {
+                        "heading": "Run the following in a terminal to harden the SSH client for the local user:",
+                        "comment": "",
+                        "command": "mkdir -p -m 0700 ~/.ssh; echo -e \"\\nHost *\\n Ciphers chacha20-poly1305@openssh.com,aes256-gcm@openssh.com,aes256-ctr,aes192-ctr,aes128-gcm@openssh.com,aes128-ctr\\n\\n KexAlgorithms sntrup761x25519-sha512@openssh.com,gss-curve25519-sha256-,curve25519-sha256,curve25519-sha256@libssh.org,gss-group16-sha512-,diffie-hellman-group16-sha512,diffie-hellman-group18-sha512,diffie-hellman-group-exchange-sha256\\n\\n MACs hmac-sha2-256-etm@openssh.com,hmac-sha2-512-etm@openssh.com,umac-128-etm@openssh.com\\n\\n RequiredRSASize 3072\\n\\n HostKeyAlgorithms sk-ssh-ed25519-cert-v01@openssh.com,ssh-ed25519-cert-v01@openssh.com,rsa-sha2-512-cert-v01@openssh.com,rsa-sha2-256-cert-v01@openssh.com,sk-ssh-ed25519@openssh.com,ssh-ed25519,rsa-sha2-512,rsa-sha2-256\\n\\n CASignatureAlgorithms sk-ssh-ed25519@openssh.com,ssh-ed25519,rsa-sha2-512,rsa-sha2-256\\n\\n GSSAPIKexAlgorithms gss-curve25519-sha256-,gss-group16-sha512-\\n\\n HostbasedAcceptedAlgorithms sk-ssh-ed25519-cert-v01@openssh.com,ssh-ed25519-cert-v01@openssh.com,sk-ssh-ed25519@openssh.com,ssh-ed25519,rsa-sha2-512-cert-v01@openssh.com,rsa-sha2-512,rsa-sha2-256-cert-v01@openssh.com,rsa-sha2-256\\n\\n PubkeyAcceptedAlgorithms sk-ssh-ed25519-cert-v01@openssh.com,ssh-ed25519-cert-v01@openssh.com,sk-ssh-ed25519@openssh.com,ssh-ed25519,rsa-sha2-512-cert-v01@openssh.com,rsa-sha2-512,rsa-sha2-256-cert-v01@openssh.com,rsa-sha2-256\\n\\n\" >> ~/.ssh/config"
+                    },
+                ]
+            },
+            {
+                "server_guide": False,
+                "version": 1,
+                "version_date": "2024-03-15",
+                "change_log": "Initial revision.",
+                "notes": "",
+                "commands": []  # Commands for this older version are not tracked here.
+            },
+        ],
+
+        "Ubuntu 22.04": [
+            {
+                "server_guide": True,
+                "version": 2,
+                "version_date": "2024-10-01",
+                "change_log": "Re-ordered host keys to prioritize ED25519 due to efficiency. Re-ordered cipher list to prioritize larger key sizes as a countermeasure to quantum attacks.",
+                "notes": "all commands below are to be executed as the root user.",
+                "commands": [
+                    {
+                        "heading": "Re-generate the RSA and ED25519 keys",
+                        "comment": "",
+                        "command": "rm /etc/ssh/ssh_host_*\nssh-keygen -t rsa -b 4096 -f /etc/ssh/ssh_host_rsa_key -N \"\"\nssh-keygen -t ed25519 -f /etc/ssh/ssh_host_ed25519_key -N \"\""
+                    },
+                    {
+                        "heading": "Enable the ED25519 and RSA keys",
+                        "comment": "Enable the ED25519 and RSA HostKey directives in the /etc/ssh/sshd_config file:",
+                        "command": "echo -e \"\\nHostKey /etc/ssh/ssh_host_ed25519_key\\nHostKey /etc/ssh/ssh_host_rsa_key\" >> /etc/ssh/sshd_config"
+                    },
+                    {
+                        "heading": "Remove small Diffie-Hellman moduli",
+                        "comment": "",
+                        "command": "awk '$5 >= 3071' /etc/ssh/moduli > /etc/ssh/moduli.safe\nmv /etc/ssh/moduli.safe /etc/ssh/moduli"
+                    },
+                    {
+                        "heading": "Restrict supported key exchange, cipher, and MAC algorithms",
+                        "comment": "",
+                        "command": "echo -e \"# Restrict key exchange, cipher, and MAC algorithms, as per sshaudit.com\\n# hardening guide.\\nKexAlgorithms sntrup761x25519-sha512@openssh.com,curve25519-sha256,curve25519-sha256@libssh.org,gss-curve25519-sha256-,diffie-hellman-group16-sha512,gss-group16-sha512-,diffie-hellman-group18-sha512,diffie-hellman-group-exchange-sha256\\n\\nCiphers chacha20-poly1305@openssh.com,aes256-gcm@openssh.com,aes256-ctr,aes192-ctr,aes128-gcm@openssh.com,aes128-ctr\\n\\nMACs hmac-sha2-256-etm@openssh.com,hmac-sha2-512-etm@openssh.com,umac-128-etm@openssh.com\\n\\nHostKeyAlgorithms sk-ssh-ed25519-cert-v01@openssh.com,ssh-ed25519-cert-v01@openssh.com,rsa-sha2-512-cert-v01@openssh.com,rsa-sha2-256-cert-v01@openssh.com,sk-ssh-ed25519@openssh.com,ssh-ed25519,rsa-sha2-512,rsa-sha2-256\\n\\nCASignatureAlgorithms sk-ssh-ed25519@openssh.com,ssh-ed25519,rsa-sha2-512,rsa-sha2-256\\n\\nGSSAPIKexAlgorithms gss-curve25519-sha256-,gss-group16-sha512-\\n\\nHostbasedAcceptedAlgorithms sk-ssh-ed25519-cert-v01@openssh.com,ssh-ed25519-cert-v01@openssh.com,sk-ssh-ed25519@openssh.com,ssh-ed25519,rsa-sha2-512-cert-v01@openssh.com,rsa-sha2-512,rsa-sha2-256-cert-v01@openssh.com,rsa-sha2-256\\n\\nPubkeyAcceptedAlgorithms sk-ssh-ed25519-cert-v01@openssh.com,ssh-ed25519-cert-v01@openssh.com,sk-ssh-ed25519@openssh.com,ssh-ed25519,rsa-sha2-512-cert-v01@openssh.com,rsa-sha2-512,rsa-sha2-256-cert-v01@openssh.com,rsa-sha2-256\" > /etc/ssh/sshd_config.d/ssh-audit_hardening.conf"
+                    },
+                    {
+                        "heading": "Implement connection rate throttling",
+                        "comment": "Connection rate throttling is needed in order to protect against the DHEat denial-of-service attack. A complete and flexible solution is to use iptables to allow up to 10 connections every 10 seconds from any one source address. An alternate solution is to set OpenSSH's PerSourceMaxStartups directive to 1 (note, however, that this can cause incomplete results during ssh-audit scans, as well as other client failures when bursts of connections are made).",
+                        "command": "iptables -I INPUT -p tcp --dport 22 -m state --state NEW -m recent --set\niptables -I INPUT -p tcp --dport 22 -m state --state NEW -m recent --update --seconds 10 --hitcount 10 -j DROP\nip6tables -I INPUT -p tcp --dport 22 -m state --state NEW -m recent --set\nip6tables -I INPUT -p tcp --dport 22 -m state --state NEW -m recent --update --seconds 10 --hitcount 10 -j DROP\nDEBIAN_FRONTEND=noninteractive apt install -q -y netfilter-persistent iptables-persistent\nservice netfilter-persistent save"
+                    },
+                    {
+                        "heading": "Restart OpenSSH server",
+                        "comment": "",
+                        "command": "service ssh restart"
+                    },
+                ]
+            },
+            {
+                "server_guide": True,
+                "version": 1,
+                "version_date": "2024-04-22",
+                "change_log": "Added connection throttling instructions to counteract the DHEat denial-of-service attack.",
+                "notes": "",
+                "commands": []  # Commands for this older version are not tracked here.
+            },
+            {
+                "server_guide": False,
+                "version": 1,
+                "version_date": "2024-10-01",
+                "change_log": "Re-ordered cipher list to prioritize larger key sizes as a countermeasure to quantum attacks.",
+                "notes": "",
+                "commands": [
+                    {
+                        "heading": "Run the following in a terminal to harden the SSH client for the local user:",
+                        "comment": "",
+                        "command": "mkdir -p -m 0700 ~/.ssh; echo -e \"\\nHost *\\n Ciphers chacha20-poly1305@openssh.com,aes256-gcm@openssh.com,aes256-ctr,aes192-ctr,aes128-gcm@openssh.com,aes128-ctr\\n\\n KexAlgorithms sntrup761x25519-sha512@openssh.com,gss-curve25519-sha256-,curve25519-sha256,curve25519-sha256@libssh.org,gss-group16-sha512-,diffie-hellman-group16-sha512,diffie-hellman-group18-sha512,diffie-hellman-group-exchange-sha256\\n\\n MACs hmac-sha2-256-etm@openssh.com,hmac-sha2-512-etm@openssh.com,umac-128-etm@openssh.com\\n\\n HostKeyAlgorithms sk-ssh-ed25519-cert-v01@openssh.com,ssh-ed25519-cert-v01@openssh.com,rsa-sha2-512-cert-v01@openssh.com,rsa-sha2-256-cert-v01@openssh.com,sk-ssh-ed25519@openssh.com,ssh-ed25519,rsa-sha2-512,rsa-sha2-256\\n\\n CASignatureAlgorithms sk-ssh-ed25519@openssh.com,ssh-ed25519,rsa-sha2-512,rsa-sha2-256\\n\\n GSSAPIKexAlgorithms gss-curve25519-sha256-,gss-group16-sha512-\\n\\n HostbasedAcceptedAlgorithms sk-ssh-ed25519-cert-v01@openssh.com,ssh-ed25519-cert-v01@openssh.com,sk-ssh-ed25519@openssh.com,ssh-ed25519,rsa-sha2-512-cert-v01@openssh.com,rsa-sha2-512,rsa-sha2-256-cert-v01@openssh.com,rsa-sha2-256\\n\\n PubkeyAcceptedAlgorithms sk-ssh-ed25519-cert-v01@openssh.com,ssh-ed25519-cert-v01@openssh.com,sk-ssh-ed25519@openssh.com,ssh-ed25519,rsa-sha2-512-cert-v01@openssh.com,rsa-sha2-512,rsa-sha2-256-cert-v01@openssh.com,rsa-sha2-256\\n\\n\" >> ~/.ssh/config"
+                    },
+                ]
+            },
+        ],
+
+        "Ubuntu 24.04": [
+            {
+                "server_guide": True,
+                "version": 3,
+                "version_date": "2025-09-01",
+                "change_log": "Removed commands directly editing sshd_config to make system updates easier for users.",
+                "notes": "all commands below are to be executed as the root user.",
+                "commands": [
+                    {
+                        "heading": "Re-generate the ED25519 and RSA keys",
+                        "comment": "",
+                        "command": "rm /etc/ssh/ssh_host_*\nssh-keygen -t ed25519 -f /etc/ssh/ssh_host_ed25519_key -N \"\"\nssh-keygen -t rsa -b 4096 -f /etc/ssh/ssh_host_rsa_key -N \"\""
+                    },
+                    {
+                        "heading": "Remove small Diffie-Hellman moduli",
+                        "comment": "",
+                        "command": "awk '$5 >= 3071' /etc/ssh/moduli > /etc/ssh/moduli.safe\nmv /etc/ssh/moduli.safe /etc/ssh/moduli"
+                    },
+                    {
+                        "heading": "Restrict supported key exchange, cipher, and MAC algorithms",
+                        "comment": "",
+                        "command": "echo -e \"# Restrict key exchange, cipher, and MAC algorithms, as per sshaudit.com\\n# hardening guide.\\nKexAlgorithms sntrup761x25519-sha512@openssh.com,gss-curve25519-sha256-,curve25519-sha256,curve25519-sha256@libssh.org,diffie-hellman-group18-sha512,diffie-hellman-group-exchange-sha256,gss-group16-sha512-,diffie-hellman-group16-sha512\\n\\nCiphers chacha20-poly1305@openssh.com,aes256-gcm@openssh.com,aes256-ctr,aes192-ctr,aes128-gcm@openssh.com,aes128-ctr\\n\\nMACs hmac-sha2-512-etm@openssh.com,hmac-sha2-256-etm@openssh.com,umac-128-etm@openssh.com\\n\\nRequiredRSASize 3072\\n\\nHostKeyAlgorithms sk-ssh-ed25519-cert-v01@openssh.com,ssh-ed25519-cert-v01@openssh.com,rsa-sha2-512-cert-v01@openssh.com,rsa-sha2-256-cert-v01@openssh.com,sk-ssh-ed25519@openssh.com,ssh-ed25519,rsa-sha2-512,rsa-sha2-256\\n\\nCASignatureAlgorithms sk-ssh-ed25519@openssh.com,ssh-ed25519,rsa-sha2-512,rsa-sha2-256\\n\\nGSSAPIKexAlgorithms gss-curve25519-sha256-,gss-group16-sha512-\\n\\nHostbasedAcceptedAlgorithms sk-ssh-ed25519-cert-v01@openssh.com,ssh-ed25519-cert-v01@openssh.com,rsa-sha2-512-cert-v01@openssh.com,rsa-sha2-256-cert-v01@openssh.com,sk-ssh-ed25519@openssh.com,ssh-ed25519,rsa-sha2-512,rsa-sha2-256\\n\\nPubkeyAcceptedAlgorithms sk-ssh-ed25519-cert-v01@openssh.com,ssh-ed25519-cert-v01@openssh.com,rsa-sha2-512-cert-v01@openssh.com,rsa-sha2-256-cert-v01@openssh.com,sk-ssh-ed25519@openssh.com,ssh-ed25519,rsa-sha2-512,rsa-sha2-256\" > /etc/ssh/sshd_config.d/ssh-audit_hardening.conf"
+                    },
+                    {
+                        "heading": "Restart OpenSSH server",
+                        "comment": "",
+                        "command": "service ssh restart"
+                    },
+                    {
+                        "heading": "Implement connection rate throttling",
+                        "comment": "Connection rate throttling is needed in order to protect against the DHEat denial-of-service attack. A complete and flexible solution is to use iptables to allow up to 10 connections every 10 seconds from any one source address. An alternate solution is to set OpenSSH's PerSourceMaxStartups directive to 1 (note, however, that this can cause incomplete results during ssh-audit scans, as well as other client failures when bursts of connections are made).",
+                        "command": "iptables -I INPUT -p tcp --dport 22 -m state --state NEW -m recent --set\niptables -I INPUT -p tcp --dport 22 -m state --state NEW -m recent --update --seconds 10 --hitcount 10 -j DROP\nip6tables -I INPUT -p tcp --dport 22 -m state --state NEW -m recent --set\nip6tables -I INPUT -p tcp --dport 22 -m state --state NEW -m recent --update --seconds 10 --hitcount 10 -j DROP\nDEBIAN_FRONTEND=noninteractive apt install -q -y netfilter-persistent iptables-persistent\nservice netfilter-persistent save"
+                    },
+                ]
+            },
+            {
+                "server_guide": True,
+                "version": 2,
+                "version_date": "2024-10-01",
+                "change_log": "Added RequiredRSASize directive to enforce a minimum of 3072-bit user and host-based authentication keys.",
+                "notes": "all commands below are to be executed as the root user.",
+                "commands": [
+                    {
+                        "heading": "Re-generate the ED25519 and RSA keys",
+                        "comment": "",
+                        "command": "rm /etc/ssh/ssh_host_*\nssh-keygen -t ed25519 -f /etc/ssh/ssh_host_ed25519_key -N \"\"\nssh-keygen -t rsa -b 4096 -f /etc/ssh/ssh_host_rsa_key -N \"\""
+                    },
+                    {
+                        "heading": "Remove small Diffie-Hellman moduli",
+                        "comment": "",
+                        "command": "awk '$5 >= 3071' /etc/ssh/moduli > /etc/ssh/moduli.safe\nmv /etc/ssh/moduli.safe /etc/ssh/moduli"
+                    },
+                    {
+                        "heading": "Enable the ED25519 and RSA keys",
+                        "comment": "Enable the ED25519 and RSA HostKey directives in the /etc/ssh/sshd_config file:",
+                        "command": "echo -e \"\\nHostKey /etc/ssh/ssh_host_ed25519_key\\nHostKey /etc/ssh/ssh_host_rsa_key\" >> /etc/ssh/sshd_config"
+                    },
+                    {
+                        "heading": "Restrict supported key exchange, cipher, and MAC algorithms",
+                        "comment": "",
+                        "command": "echo -e \"# Restrict key exchange, cipher, and MAC algorithms, as per sshaudit.com\\n# hardening guide.\\nKexAlgorithms sntrup761x25519-sha512@openssh.com,gss-curve25519-sha256-,curve25519-sha256,curve25519-sha256@libssh.org,diffie-hellman-group18-sha512,diffie-hellman-group-exchange-sha256,gss-group16-sha512-,diffie-hellman-group16-sha512\\n\\nCiphers chacha20-poly1305@openssh.com,aes256-gcm@openssh.com,aes256-ctr,aes192-ctr,aes128-gcm@openssh.com,aes128-ctr\\n\\nMACs hmac-sha2-512-etm@openssh.com,hmac-sha2-256-etm@openssh.com,umac-128-etm@openssh.com\\n\\nRequiredRSASize 3072\\n\\nHostKeyAlgorithms sk-ssh-ed25519-cert-v01@openssh.com,ssh-ed25519-cert-v01@openssh.com,rsa-sha2-512-cert-v01@openssh.com,rsa-sha2-256-cert-v01@openssh.com,sk-ssh-ed25519@openssh.com,ssh-ed25519,rsa-sha2-512,rsa-sha2-256\\n\\nCASignatureAlgorithms sk-ssh-ed25519@openssh.com,ssh-ed25519,rsa-sha2-512,rsa-sha2-256\\n\\nGSSAPIKexAlgorithms gss-curve25519-sha256-,gss-group16-sha512-\\n\\nHostbasedAcceptedAlgorithms sk-ssh-ed25519-cert-v01@openssh.com,ssh-ed25519-cert-v01@openssh.com,rsa-sha2-512-cert-v01@openssh.com,rsa-sha2-256-cert-v01@openssh.com,sk-ssh-ed25519@openssh.com,ssh-ed25519,rsa-sha2-512,rsa-sha2-256\\n\\nPubkeyAcceptedAlgorithms sk-ssh-ed25519-cert-v01@openssh.com,ssh-ed25519-cert-v01@openssh.com,rsa-sha2-512-cert-v01@openssh.com,rsa-sha2-256-cert-v01@openssh.com,sk-ssh-ed25519@openssh.com,ssh-ed25519,rsa-sha2-512,rsa-sha2-256\" > /etc/ssh/sshd_config.d/ssh-audit_hardening.conf"
+                    },
+                    {
+                        "heading": "Restart OpenSSH server",
+                        "comment": "",
+                        "command": "service ssh restart"
+                    },
+                    {
+                        "heading": "Implement connection rate throttling",
+                        "comment": "Connection rate throttling is needed in order to protect against the DHEat denial-of-service attack. A complete and flexible solution is to use iptables to allow up to 10 connections every 10 seconds from any one source address. An alternate solution is to set OpenSSH's PerSourceMaxStartups directive to 1 (note, however, that this can cause incomplete results during ssh-audit scans, as well as other client failures when bursts of connections are made).",
+                        "command": "iptables -I INPUT -p tcp --dport 22 -m state --state NEW -m recent --set\niptables -I INPUT -p tcp --dport 22 -m state --state NEW -m recent --update --seconds 10 --hitcount 10 -j DROP\nip6tables -I INPUT -p tcp --dport 22 -m state --state NEW -m recent --set\nip6tables -I INPUT -p tcp --dport 22 -m state --state NEW -m recent --update --seconds 10 --hitcount 10 -j DROP\nDEBIAN_FRONTEND=noninteractive apt install -q -y netfilter-persistent iptables-persistent\nservice netfilter-persistent save"
+                    },
+                ]
+            },
+            {
+                "server_guide": True,
+                "version": 1,
+                "version_date": "2024-04-29",
+                "change_log": "Initial revision. In comparison to Ubuntu 22.04 LTS guide, the following changes were made: 1.) For key exchanges, diffie-hellman-group18-sha512 and diffie-hellman-group-exchange-sha256 were prioritized over diffie-hellman-group16-sha512 due to greater security strength; GSS algorithms were prioritized over their non-GSS equivalents in order to match the client guide, 2.) For ciphers, 256-bit AES ciphers were prioritized over 192 and 128-bit AES ciphers due to their increased resistence against quantum computing attacks (previously, weaker GCM ciphers had priority over CTR ciphers), 3.) The HostbasedAcceptedAlgorithms and PubkeyAcceptedAlgorithms settings are now the same as HostKeyAlgorithms setting, 4.) The hmac-sha2-512-etm@openssh.com MAC was increased in priority due to its increased resistence against quantum computing attacks, and 5.) The ED25519 host keys were given priority over RSA host keys due to their greater efficiency.",
+                "notes": "",
+                "commands": []  # Commands for this older version are not tracked here.
+            },
+            {
+                "server_guide": False,
+                "version": 2,
+                "version_date": "2024-10-01",
+                "change_log": "Added RequiredRSASize directive to enforce a minimum of 3072-bit user and host-based authentication keys.",
+                "notes": "",
+                "commands": [
+                    {
+                        "heading": "Run the following in a terminal to harden the SSH client for the local user:",
+                        "comment": "",
+                        "command": "mkdir -p -m 0700 ~/.ssh; echo -e \"\\nHost *\\n Ciphers chacha20-poly1305@openssh.com,aes256-gcm@openssh.com,aes256-ctr,aes192-ctr,aes128-gcm@openssh.com,aes128-ctr\\n\\n KexAlgorithms sntrup761x25519-sha512@openssh.com,gss-curve25519-sha256-,curve25519-sha256,curve25519-sha256@libssh.org,diffie-hellman-group18-sha512,diffie-hellman-group-exchange-sha256,gss-group16-sha512-,diffie-hellman-group16-sha512\\n\\n MACs hmac-sha2-512-etm@openssh.com,hmac-sha2-256-etm@openssh.com,umac-128-etm@openssh.com\\n\\n RequiredRSASize 3072\\n\\n HostKeyAlgorithms sk-ssh-ed25519-cert-v01@openssh.com,ssh-ed25519-cert-v01@openssh.com,rsa-sha2-512-cert-v01@openssh.com,rsa-sha2-256-cert-v01@openssh.com,sk-ssh-ed25519@openssh.com,ssh-ed25519,rsa-sha2-512,rsa-sha2-256\\n\\n CASignatureAlgorithms sk-ssh-ed25519@openssh.com,ssh-ed25519,rsa-sha2-512,rsa-sha2-256\\n\\n GSSAPIKexAlgorithms gss-curve25519-sha256-,gss-group16-sha512-\\n\\n HostbasedAcceptedAlgorithms sk-ssh-ed25519-cert-v01@openssh.com,ssh-ed25519-cert-v01@openssh.com,rsa-sha2-512-cert-v01@openssh.com,rsa-sha2-256-cert-v01@openssh.com,sk-ssh-ed25519@openssh.com,ssh-ed25519,rsa-sha2-512,rsa-sha2-256\\n\\n PubkeyAcceptedAlgorithms sk-ssh-ed25519-cert-v01@openssh.com,ssh-ed25519-cert-v01@openssh.com,rsa-sha2-512-cert-v01@openssh.com,rsa-sha2-256-cert-v01@openssh.com,sk-ssh-ed25519@openssh.com,ssh-ed25519,rsa-sha2-512,rsa-sha2-256\\n\\n\" >> ~/.ssh/config"
+                    },
+                ]
+            },
+            {
+                "server_guide": False,
+                "version": 1,
+                "version_date": "2024-04-29",
+                "change_log": "Initial revision. In comparison to Ubuntu 22.04 LTS Client guide, the following changes were made: 1.) For key exchanges, diffie-hellman-group18-sha512 and diffie-hellman-group-exchange-sha256 were prioritized over diffie-hellman-group16-sha512 due to greater security strength, 2.) For ciphers, 256-bit AES ciphers were prioritized over 192 and 128-bit AES ciphers due to their increased resistence against quantum computing attacks (previously, weaker GCM ciphers had priority over CTR ciphers), 3.) The HostbasedAcceptedAlgorithms and PubkeyAcceptedAlgorithms settings are now the same as HostKeyAlgorithms setting, and 4.) The hmac-sha2-512-etm@openssh.com MAC was increased in priority due to its increased resistence against quantum computing attacks.",
+                "notes": "",
+                "commands": []  # Commands for this older version are not tracked here.
+            },
+        ],
+
+        "Linux Mint 21": [
+            {
+                "server_guide": False,
+                "version": 1,
+                "version_date": "2024-10-01",
+                "change_log": "Re-ordered cipher list to prioritize larger key sizes as a countermeasure to quantum attacks.",
+                "notes": "",
+                "commands": [
+                    {
+                        "heading": "Run the following in a terminal to harden the SSH client for the local user:",
+                        "comment": "",
+                        "command": "mkdir -p -m 0700 ~/.ssh; echo -e \"\\nHost *\\n Ciphers chacha20-poly1305@openssh.com,aes256-gcm@openssh.com,aes256-ctr,aes192-ctr,aes128-gcm@openssh.com,aes128-ctr\\n\\n KexAlgorithms sntrup761x25519-sha512@openssh.com,gss-curve25519-sha256-,curve25519-sha256,curve25519-sha256@libssh.org,gss-group16-sha512-,diffie-hellman-group16-sha512,diffie-hellman-group18-sha512,diffie-hellman-group-exchange-sha256\\n\\n MACs hmac-sha2-256-etm@openssh.com,hmac-sha2-512-etm@openssh.com,umac-128-etm@openssh.com\\n\\n HostKeyAlgorithms sk-ssh-ed25519-cert-v01@openssh.com,ssh-ed25519-cert-v01@openssh.com,rsa-sha2-512-cert-v01@openssh.com,rsa-sha2-256-cert-v01@openssh.com,sk-ssh-ed25519@openssh.com,ssh-ed25519,rsa-sha2-512,rsa-sha2-256\\n\\n CASignatureAlgorithms sk-ssh-ed25519@openssh.com,ssh-ed25519,rsa-sha2-512,rsa-sha2-256\\n\\n GSSAPIKexAlgorithms gss-curve25519-sha256-,gss-group16-sha512-\\n\\n HostbasedAcceptedAlgorithms sk-ssh-ed25519-cert-v01@openssh.com,ssh-ed25519-cert-v01@openssh.com,sk-ssh-ed25519@openssh.com,ssh-ed25519,rsa-sha2-512-cert-v01@openssh.com,rsa-sha2-512,rsa-sha2-256-cert-v01@openssh.com,rsa-sha2-256\\n\\n PubkeyAcceptedAlgorithms sk-ssh-ed25519-cert-v01@openssh.com,ssh-ed25519-cert-v01@openssh.com,sk-ssh-ed25519@openssh.com,ssh-ed25519,rsa-sha2-512-cert-v01@openssh.com,rsa-sha2-512,rsa-sha2-256-cert-v01@openssh.com,rsa-sha2-256\\n\\n\" >> ~/.ssh/config"
+                    },
+                ]
+            },
+        ],
+
+        "Linux Mint 22": [
+            {
+                "server_guide": False,
+                "version": 2,
+                "version_date": "2024-10-01",
+                "change_log": "Added RequiredRSASize directive to enforce a minimum of 3072-bit user and host-based authentication keys.",
+                "notes": "",
+                "commands": [
+                    {
+                        "heading": "Run the following in a terminal to harden the SSH client for the local user:",
+                        "comment": "",
+                        "command": "mkdir -p -m 0700 ~/.ssh; echo -e \"\\nHost *\\n Ciphers chacha20-poly1305@openssh.com,aes256-gcm@openssh.com,aes256-ctr,aes192-ctr,aes128-gcm@openssh.com,aes128-ctr\\n\\n KexAlgorithms sntrup761x25519-sha512@openssh.com,gss-curve25519-sha256-,curve25519-sha256,curve25519-sha256@libssh.org,diffie-hellman-group18-sha512,diffie-hellman-group-exchange-sha256,gss-group16-sha512-,diffie-hellman-group16-sha512\\n\\n MACs hmac-sha2-512-etm@openssh.com,hmac-sha2-256-etm@openssh.com,umac-128-etm@openssh.com\\n\\n RequiredRSASize 3072\\n\\n HostKeyAlgorithms sk-ssh-ed25519-cert-v01@openssh.com,ssh-ed25519-cert-v01@openssh.com,rsa-sha2-512-cert-v01@openssh.com,rsa-sha2-256-cert-v01@openssh.com,sk-ssh-ed25519@openssh.com,ssh-ed25519,rsa-sha2-512,rsa-sha2-256\\n\\n CASignatureAlgorithms sk-ssh-ed25519@openssh.com,ssh-ed25519,rsa-sha2-512,rsa-sha2-256\\n\\n GSSAPIKexAlgorithms gss-curve25519-sha256-,gss-group16-sha512-\\n\\n HostbasedAcceptedAlgorithms sk-ssh-ed25519-cert-v01@openssh.com,ssh-ed25519-cert-v01@openssh.com,rsa-sha2-512-cert-v01@openssh.com,rsa-sha2-256-cert-v01@openssh.com,sk-ssh-ed25519@openssh.com,ssh-ed25519,rsa-sha2-512,rsa-sha2-256\\n\\n PubkeyAcceptedAlgorithms sk-ssh-ed25519-cert-v01@openssh.com,ssh-ed25519-cert-v01@openssh.com,rsa-sha2-512-cert-v01@openssh.com,rsa-sha2-256-cert-v01@openssh.com,sk-ssh-ed25519@openssh.com,ssh-ed25519,rsa-sha2-512,rsa-sha2-256\\n\\n\" >> ~/.ssh/config"
+                    },
+                ]
+            },
+            {
+                "server_guide": False,
+                "version": 1,
+                "version_date": "2024-04-29",
+                "change_log": "Initial revision. In comparison to Ubuntu 22.04 LTS Client guide, the following changes were made: 1.) For key exchanges, diffie-hellman-group18-sha512 and diffie-hellman-group-exchange-sha256 were prioritized over diffie-hellman-group16-sha512 due to greater security strength, 2.) For ciphers, 256-bit AES ciphers were prioritized over 192 and 128-bit AES ciphers due to their increased resistence against quantum computing attacks (previously, weaker GCM ciphers had priority over CTR ciphers), 3.) The HostbasedAcceptedAlgorithms and PubkeyAcceptedAlgorithms settings are now the same as HostKeyAlgorithms setting, and 4.) The hmac-sha2-512-etm@openssh.com MAC was increased in priority due to its increased resistence against quantum computing attacks.",
+                "notes": "",
+                "commands": []  # Commands for this older version are not tracked here.
+            },
+        ],
+    }
+
+
+    @staticmethod
+    def list_guides(out: OutputBuffer, verbose: bool) -> None:
+        '''Print all the server and client hardening guides.'''
+
+
+        server_guide_names = []
+        client_guide_names = []
+
+        # Iterate through the guides, and record a list of server guide names, along with a separate list for client guide names.
+        for name, guides in Hardening_Guides.HARDENING_GUIDES.items():
+            for guide in guides:
+                version = guide["version"]
+                version_date = guide["version_date"]
+                change_log = guide["change_log"]
+                if guide["server_guide"]:
+                    full_name = f"{name} Server" if not verbose else f"{name} Server (version {version}): {version_date}: {change_log}"
+                    if full_name not in server_guide_names:
+                        server_guide_names.append(full_name)
+                else:
+                    full_name = f"{name} Client" if not verbose else f"{name} Client (version {version}): {version_date}: {change_log}"
+                    if full_name not in client_guide_names:
+                        client_guide_names.append(full_name)
+
+        # Sort the names.
+        server_guide_names.sort()
+        client_guide_names.sort()
+
+        # Print the lists.
+        out.head("\nServer hardening guides:\n")
+        out.info("  * %s" % "\n  * ".join(server_guide_names))
+
+        out.head("\nClient hardening guides:\n")
+        out.info("  * %s" % "\n  * ".join(client_guide_names))
+        out.info("\n")
+
+        if not verbose:
+            out.info("Hint: add -v to --list-hardening-guides in order to see change log messages and prior versions.  Prior versions of hardening guides can be retrieved as well with --get-hardening-guide (i.e.: --get-hardening-guide \"Ubuntu 24.04 Server (version 1)\").\n")
+        out.write()
+
+
+    @staticmethod
+    def print_hardening_guide(out: OutputBuffer, platform: str) -> None:
+        '''Prints a hardening guide for the specified platform.'''
+
+
+        platform_orig = platform
+        invalid_guide_name_error = "Invalid guide name.  Run --list-hardening-guides to see list of valid guide names."
+
+        # If the user provided a version with the platform name, parse the version number they're interested in.
+        use_latest_version = True
+        use_version = 0
+        pos = platform.find(" (version ")
+        if pos != -1:
+            use_latest_version = False
+            end_pos = platform.find(")", pos)
+            try:
+                use_version = int(platform[pos + 10:end_pos])
+            except ValueError:
+                out.fail(invalid_guide_name_error, write_now=True)
+                return
+
+            platform = platform[0:pos]
+
+        last_space_pos = platform.rfind(" ")
+        if last_space_pos == -1:
+            out.fail(invalid_guide_name_error, write_now=True)
+            return
+
+        # From input such as "Ubuntu 24.04 Server", parse the OS name ("Ubuntu 24.04") and last word ("Server").
+        os_name = platform[0:last_space_pos]
+        last_word = platform[last_space_pos + 1:]
+
+        # Determine if this is a server or client guide.
+        is_server = False
+        if last_word == "Server":
+            is_server = True
+        elif last_word != "Client":
+            out.fail(invalid_guide_name_error, write_now=True)
+            return
+
+        # Ensure that this OS exists in the database.
+        if os_name not in Hardening_Guides.HARDENING_GUIDES:
+            out.fail(invalid_guide_name_error, write_now=True)
+            return
+
+        # Pull all guides for this OS name.
+        guides = Hardening_Guides.HARDENING_GUIDES[os_name]
+
+        # Iterate over guides until we find the type (server/client) we need, as well as the version of the guide we need.
+        selected_guide = None
+        latest_version = 0
+        for guide in guides:
+            if guide["server_guide"] == is_server:
+                version = guide["version"]
+                if use_latest_version and (version > latest_version):
+                    selected_guide = guide
+                    latest_version = version
+                elif use_latest_version is False and use_version == version:
+                    selected_guide = guide
+
+        # Ensure we found a guide from above.
+        if selected_guide is None:
+            out.fail(invalid_guide_name_error, write_now=True)
+            return
+
+        # Now print the guide.
+        version_header = f"\n#\n# Hardening guide for {platform_orig}\n#\n" if not use_latest_version else f"\n#\n# Hardening guide for {platform_orig} (version {latest_version})\n#\n"
+        out.info(version_header)
+
+        commands = selected_guide["commands"]
+        for command_dict in commands:
+            heading = command_dict["heading"]
+            comment = command_dict["comment"]
+            command = command_dict["command"]
+            if heading != "":
+                out.info(f"# {heading}")
+
+            if comment != "":
+                out.info(f"# {comment}")
+
+            out.info(f"{command}")
+            out.info(s="")
+
+        out.write()

src/ssh_audit/policy.py

@@ -1,7 +1,7 @@
 """
    The MIT License (MIT)
 
-   Copyright (C) 2020-2024 Joe Testa (jtesta@positronsecurity.com)
+   Copyright (C) 2020-2025 Joe Testa (jtesta@positronsecurity.com)
 
    Permission is hereby granted, free of charge, to any person obtaining a copy
    of this software and associated documentation files (the "Software"), to deal
@@ -55,6 +55,7 @@ class Policy:
         self._dh_modulus_sizes: Optional[Dict[str, int]] = None
         self._server_policy = True
         self._allow_algorithm_subset_and_reordering = False
+        self._allow_hostkey_subset_and_reordering = False
         self._allow_larger_keys = False
         self._errors: List[Any] = []
         self._updated_builtin_policy_available = False  # If True, an outdated built-in policy was loaded.
@@ -116,7 +117,7 @@ class Policy:
             key = key.strip()
             val = val.strip()
 
-            if key not in ['name', 'version', 'banner', 'compressions', 'host keys', 'optional host keys', 'key exchanges', 'ciphers', 'macs', 'client policy', 'host_key_sizes', 'dh_modulus_sizes', 'allow_algorithm_subset_and_reordering', 'allow_larger_keys'] and not key.startswith('hostkey_size_') and not key.startswith('cakey_size_') and not key.startswith('dh_modulus_size_'):
+            if key not in ['name', 'version', 'banner', 'compressions', 'host keys', 'optional host keys', 'key exchanges', 'ciphers', 'macs', 'client policy', 'host_key_sizes', 'dh_modulus_sizes', 'allow_algorithm_subset_and_reordering', 'allow_hostkey_subset_and_reordering', 'allow_larger_keys'] and not key.startswith('hostkey_size_') and not key.startswith('cakey_size_') and not key.startswith('dh_modulus_size_'):
                 raise ValueError("invalid field found in policy: %s" % line)
 
             if key in ['name', 'banner']:
@@ -211,6 +212,9 @@ class Policy:
                 self._server_policy = False
             elif key == 'allow_algorithm_subset_and_reordering' and val.lower() == 'true':
                 self._allow_algorithm_subset_and_reordering = True
+                self._allow_hostkey_subset_and_reordering = True  # We force subsets/reorderings of the host keys as well in this case.
+            elif key == 'allow_hostkey_subset_and_reordering' and val.lower() == 'true':
+                self._allow_hostkey_subset_and_reordering = True
             elif key == 'allow_larger_keys' and val.lower() == 'true':
                 self._allow_larger_keys = True
 
@@ -300,9 +304,12 @@ name = "Custom Policy (based on %s on %s)"
 # The version of this policy (displayed in the output during scans).  Not parsed, and may be any value, including strings.
 version = 1
 
-# When false, host keys, kex, ciphers, and MAC lists must match exactly.  When true, the target host may support a subset of the specified algorithms and/or algorithms may appear in a different order; this feature is useful for specifying a baseline and allowing some hosts the option to implement stricter controls.
+# When false, host keys, kex, ciphers, and MAC lists must match exactly.  When true, the target host may support a subset of the specified algorithms and/or algorithms may appear in a different order; this feature is useful for specifying a baseline and allowing some hosts the option to implement stricter controls.  A value of true automatically sets "allow_hostkey_subset_and_reordering" to true as well.
 allow_algorithm_subset_and_reordering = false
 
+# When false, the host key list must match exactly.  When true, the target host may support a subset of the specified host keys and/or the keys may appear in a different order.
+allow_hostkey_subset_and_reordering = true
+
 # When false, host keys, CA keys, and Diffie-Hellman key sizes must exactly match what's specified in this policy.  When true, target systems are allowed to have larger keys; this feature is useful for specifying a baseline and allowing some hosts the option to implement stricter controls.
 allow_larger_keys = false
 
@@ -358,7 +365,7 @@ macs = %s
         # Check host keys.
         if self._host_keys is not None:
             # If the policy allows subsets and re-ordered algorithms...
-            if self._allow_algorithm_subset_and_reordering:
+            if self._allow_hostkey_subset_and_reordering:
                 for hostkey_t in kex.key_algorithms:
                     if hostkey_t not in self._host_keys:
                         ret = False
@@ -467,11 +474,18 @@ macs = %s
     def _get_errors(self) -> Tuple[List[Any], str]:
         '''Returns the list of errors, along with the string representation of those errors.'''
 
-        subset_and_reordering_semicolon = "; subset and/or reordering allowed" if self._allow_algorithm_subset_and_reordering else "; exact match"
+        all_subset_and_reordering_semicolon = "; subset and/or reordering allowed" if self._allow_algorithm_subset_and_reordering else "; exact match"
-        subset_and_reordering_parens = " (subset and/or reordering allowed)" if self._allow_algorithm_subset_and_reordering else ""
+        all_subset_and_reordering_parens = " (subset and/or reordering allowed)" if self._allow_algorithm_subset_and_reordering else ""
+        hostkey_subset_and_reordering_semicolon = "; subset and/or reordering allowed" if self._allow_hostkey_subset_and_reordering else "; exact match"
+        hostkey_subset_and_reordering_parens = " (subset and/or reordering allowed)" if self._allow_hostkey_subset_and_reordering else ""
+
         error_list = []
         spacer = ''
         for e in self._errors:
+
+            subset_and_reordering_semicolon = hostkey_subset_and_reordering_semicolon if e["mismatched_field"] == "Host keys" else all_subset_and_reordering_semicolon
+            subset_and_reordering_parens = hostkey_subset_and_reordering_parens if e["mismatched_field"] == "Host keys" else all_subset_and_reordering_parens
+
             e_str = "  * %s did not match.\n" % e['mismatched_field']
 
             if ('expected_optional' in e) and (e['expected_optional'] != ['']):
@@ -579,6 +593,7 @@ macs = %s
             p._dh_modulus_sizes = cast(Optional[Dict[str, int]], policy_struct['dh_modulus_sizes'])  # pylint: disable=protected-access
             p._server_policy = cast(bool, policy_struct['server_policy'])  # pylint: disable=protected-access
             p._name_and_version = "%s (version %s)" % (p._name, p._version)  # pylint: disable=protected-access
+            p._allow_hostkey_subset_and_reordering = cast(bool, policy_struct['allow_hostkey_subset_and_reordering']) if 'allow_hostkey_subset_and_reordering' in policy_struct else False  # pylint: disable=protected-access
 
             # Ensure this struct has all the necessary fields.
             p._normalize_hostkey_sizes()  # pylint: disable=protected-access
@@ -646,7 +661,7 @@ macs = %s
         if self._dh_modulus_sizes is not None:
             dh_modulus_sizes_str = str(self._dh_modulus_sizes)
 
-        return "Name: %s\nVersion: %s\nAllow Algorithm Subset and/or Reordering: %r\nBanner: %s\nCompressions: %s\nHost Keys: %s\nOptional Host Keys: %s\nKey Exchanges: %s\nCiphers: %s\nMACs: %s\nHost Key Sizes: %s\nDH Modulus Sizes: %s\nServer Policy: %r" % (name, version, self._allow_algorithm_subset_and_reordering, banner, compressions_str, host_keys_str, optional_host_keys_str, kex_str, ciphers_str, macs_str, hostkey_sizes_str, dh_modulus_sizes_str, self._server_policy)
+        return "Name: %s\nVersion: %s\nAllow Algorithm Subset and/or Reordering: %r\nAllow Host Key Subset and/or Reordering: %r\nBanner: %s\nCompressions: %s\nHost Keys: %s\nOptional Host Keys: %s\nKey Exchanges: %s\nCiphers: %s\nMACs: %s\nHost Key Sizes: %s\nDH Modulus Sizes: %s\nServer Policy: %r" % (name, version, self._allow_algorithm_subset_and_reordering, self._allow_hostkey_subset_and_reordering, banner, compressions_str, host_keys_str, optional_host_keys_str, kex_str, ciphers_str, macs_str, hostkey_sizes_str, dh_modulus_sizes_str, self._server_policy)
 
 
     def __getstate__(self) -> Dict[str, Any]:

src/ssh_audit/ssh_audit.py

@@ -53,6 +53,7 @@ from ssh_audit.gextest import GEXTest
 from ssh_audit.hostkeytest import HostKeyTest
 from ssh_audit.outputbuffer import OutputBuffer
 from ssh_audit.policy import Policy
+from ssh_audit.hardening_guides import Hardening_Guides
 from ssh_audit.product import Product
 from ssh_audit.protocol import Protocol
 from ssh_audit.software import Software
@@ -332,7 +333,7 @@ def output_info(out: OutputBuffer, software: Optional['Software'], client_audit:
 
         # If any warnings or failures were given, print a link to the hardening guides.
         if any_problems:
-            out.warn('(nfo) For hardening guides on common OSes, please see: <https://www.ssh-audit.com/hardening_guides.html>')
+            out.warn('(nfo) For hardening guides on common OSes, a built-in list can be viewed with --list-hardening-guides, or an online list can be found at: <https://www.ssh-audit.com/hardening_guides.html>')
 
         # Add any additional notes.
         for additional_note in additional_notes:
@@ -789,11 +790,14 @@ def process_commandline(out: OutputBuffer, args: List[str]) -> 'AuditConf':  # p
     # Add long options to the parser
     parser.add_argument("--conn-rate-test", action="store", dest="conn_rate_test", metavar="N[:max_rate]", type=str, default=None, help="perform a connection rate test (useful for collecting metrics related to susceptibility of the DHEat vuln). Testing is conducted with N concurrent sockets with an optional maximum rate of connections per second")
     parser.add_argument("--dheat", action="store", dest="dheat", metavar="N[:kex[:e_len]]", type=str, default=None, help="continuously perform the DHEat DoS attack (CVE-2002-20001) against the target using N concurrent sockets.  Optionally, a specific key exchange algorithm can be specified instead of allowing it to be automatically chosen.  Additionally, a small length of the fake e value sent to the server can be chosen for a more efficient attack (such as 4).")
+    parser.add_argument("--get-hardening-guide", action="store", metavar="platform", dest="get_hardening_guide", type=str, default=None, help="retrieves the hardening guide for the specified platform name (use --list-hardening-guides to see list of available guides).")
+    parser.add_argument("--list-hardening-guides", action="store_true", dest="list_hardening_guides", default=False, help="list all official, built-in hardening guides for common systems.  Their full names can then be passed to --get-hardening-guide.  Add -v to this option to view hardening guide change logs and prior versions.")
     parser.add_argument("--lookup", action="store", dest="lookup", metavar="alg1[,alg2,...]", type=str, default=None, help="looks up an algorithm(s) without connecting to a server.")
     parser.add_argument("--skip-rate-test", action="store_true", dest="skip_rate_test", default=False, help="skip the connection rate test during standard audits (used to safely infer whether the DHEat attack is viable)")
     parser.add_argument("--threads", action="store", dest="threads", metavar="N", type=int, default=32, help="number of threads to use when scanning multiple targets (-T/--targets) (default: %(default)s)")
 
-    # The mandatory target option.  Or rather, mandatory when -L, -T, or --lookup are not used.
+
+    # The mandatory target option.  Or rather, mandatory when -L, -T, --lookup or --print-config are not used.
     parser.add_argument("host", nargs="?", action="store", type=str, default="", help="target hostname or IPv4/IPv6 address")
 
     # If no arguments were given, print the help and exit.
@@ -889,8 +893,8 @@ def process_commandline(out: OutputBuffer, args: List[str]) -> 'AuditConf':  # p
         parser.print_help()
         sys.exit(exitcodes.UNKNOWN_ERROR)
 
-    if argument.host == "" and argument.client_audit is False and argument.targets is None and argument.list_policies is False and argument.lookup is None and argument.manual is False:
+    if argument.host == "" and argument.client_audit is False and argument.targets is None and argument.list_policies is False and argument.lookup is None and argument.manual is False and argument.list_hardening_guides is False and argument.get_hardening_guide is None:
-        out.fail("target host must be specified, unless -c, -m, -L, -T, or --lookup are used", write_now=True)
+        out.fail("target host must be specified, unless -c, -m, -L, -T, --lookup or --list-hardening-guides are used", write_now=True)
         sys.exit(exitcodes.UNKNOWN_ERROR)
 
     if aconf.manual:
@@ -903,6 +907,14 @@ def process_commandline(out: OutputBuffer, args: List[str]) -> 'AuditConf':  # p
         list_policies(out, aconf.verbose)
         sys.exit(exitcodes.GOOD)
 
+    # Print a list of the hardening guides, or the specific guide requested by the user.
+    if argument.list_hardening_guides is True:
+        Hardening_Guides.list_guides(out, aconf.verbose)
+        sys.exit(exitcodes.GOOD)
+    elif argument.get_hardening_guide is not None:
+        Hardening_Guides.print_hardening_guide(out, argument.get_hardening_guide)
+        sys.exit(exitcodes.GOOD)
+
     if aconf.client_audit is False and aconf.target_file is None:
         if oport is not None:
             host = argument.host

ssh-audit.1

@@ -1,4 +1,4 @@
-.TH SSH-AUDIT 1 "July 26, 2025"
+.TH SSH-AUDIT 1 "August 17, 2025"
 .SH NAME
 \fBssh-audit\fP \- SSH server & client configuration auditor
 .SH SYNOPSIS
@@ -51,6 +51,11 @@ Enable debug output.
 .br
 Run the DHEat DoS attack (CVE-2002-20001) against the target server (which will consume all available CPU resources).  The number of concurrent sockets, N, needed to achieve this effect will be highly dependent on the CPU resources available on the target, as well as the latency between the source and target machines.  The key exchange is automatically chosen based on which would cause maximum effect, unless explicitly chosen in the second field.  Lastly, an (experimental) option allows the length in bytes of the fake e value sent to the server to be specified in the third field.  Normally, the length of e is roughly the length of the modulus of the Diffie-Hellman exchange (hence, an 8192-bit / 1024-byte value of e is sent in each connection when targeting the diffie-hellman-group18-sha512 algorithm).  Instead, it was observed that many SSH implementations accept small values, such as 4 bytes; this results in a much more network-efficient attack.
 
+.TP
+.B \-\-get\-hardening\-guide=<platform_name>
+.br
+Retrieves the hardening guide for the specified platform name (use \-\-list\-hardening\-guides to see list of available guides).
+
 .TP
 .B -g, \-\-gex-test=<x[,y,...] | min1:pref1:max1[,min2:pref2:max2,...] | x-y[:step]>
 .br
@@ -91,10 +96,15 @@ Output results in JSON format.  Specify twice (-jj) to enable indent printing (u
 .br
 Specify the minimum output level.  Default is info.
 
+.TP
+.B \-\-list-hardening-guides
+.br
+List all official, built-in hardening guides for common systems.  Their full names can then be passed to \-\-get\-hardening\-guide.  Add \-v to this option to view hardening guide change logs and prior versions.
+
 .TP
 .B -L, \-\-list-policies
 .br
-List all official, built-in policies for common systems.  Their full names can then be passed to -P/--policy.  Add \-v to \-L to view policy change logs.
+List all official, built-in policies for common systems.  Their full names can then be passed to \-P/\-\-policy.  Add \-v to \-L to view policy change logs.
 
 .TP
 .B \-\-lookup=<alg1,alg2,...>

test/docker/expected_results/dropbear_2019.78_test1.txt

@@ -93,5 +93,5 @@
 (rec) -kexguess2@matt.ucc.asn.au     -- kex algorithm to remove 
 
 # additional info
-(nfo) For hardening guides on common OSes, please see: <https://www.ssh-audit.com/hardening_guides.html>
+(nfo) For hardening guides on common OSes, a built-in list can be viewed with --list-hardening-guides, or an online list can be found at: <https://www.ssh-audit.com/hardening_guides.html>
 

test/docker/expected_results/openssh_4.0p1_test1.txt

@@ -107,5 +107,5 @@
 (rec) -aes256-cbc                         -- enc algorithm to remove 
 
 # additional info
-(nfo) For hardening guides on common OSes, please see: <https://www.ssh-audit.com/hardening_guides.html>
+(nfo) For hardening guides on common OSes, a built-in list can be viewed with --list-hardening-guides, or an online list can be found at: <https://www.ssh-audit.com/hardening_guides.html>
 

test/docker/expected_results/openssh_5.6p1_test1.txt

@@ -117,5 +117,5 @@
 (rec) -umac-64@openssh.com                  -- mac algorithm to remove 
 
 # additional info
-(nfo) For hardening guides on common OSes, please see: <https://www.ssh-audit.com/hardening_guides.html>
+(nfo) For hardening guides on common OSes, a built-in list can be viewed with --list-hardening-guides, or an online list can be found at: <https://www.ssh-audit.com/hardening_guides.html>
 

test/docker/expected_results/openssh_5.6p1_test2.txt

@@ -118,5 +118,5 @@
 (rec) -umac-64@openssh.com                  -- mac algorithm to remove 
 
 # additional info
-(nfo) For hardening guides on common OSes, please see: <https://www.ssh-audit.com/hardening_guides.html>
+(nfo) For hardening guides on common OSes, a built-in list can be viewed with --list-hardening-guides, or an online list can be found at: <https://www.ssh-audit.com/hardening_guides.html>
 

test/docker/expected_results/openssh_5.6p1_test3.txt

@@ -117,5 +117,5 @@
 (rec) -umac-64@openssh.com                  -- mac algorithm to remove 
 
 # additional info
-(nfo) For hardening guides on common OSes, please see: <https://www.ssh-audit.com/hardening_guides.html>
+(nfo) For hardening guides on common OSes, a built-in list can be viewed with --list-hardening-guides, or an online list can be found at: <https://www.ssh-audit.com/hardening_guides.html>
 

test/docker/expected_results/openssh_5.6p1_test4.txt

@@ -116,5 +116,5 @@
 (rec) -umac-64@openssh.com                  -- mac algorithm to remove 
 
 # additional info
-(nfo) For hardening guides on common OSes, please see: <https://www.ssh-audit.com/hardening_guides.html>
+(nfo) For hardening guides on common OSes, a built-in list can be viewed with --list-hardening-guides, or an online list can be found at: <https://www.ssh-audit.com/hardening_guides.html>
 

test/docker/expected_results/openssh_5.6p1_test5.txt

@@ -115,5 +115,5 @@
 (rec) -umac-64@openssh.com                  -- mac algorithm to remove 
 
 # additional info
-(nfo) For hardening guides on common OSes, please see: <https://www.ssh-audit.com/hardening_guides.html>
+(nfo) For hardening guides on common OSes, a built-in list can be viewed with --list-hardening-guides, or an online list can be found at: <https://www.ssh-audit.com/hardening_guides.html>
 

test/docker/expected_results/openssh_8.0p1_custom_policy_test18.json

@@ -0,0 +1,8 @@
+{
+    "errors": [],
+    "host": "localhost",
+    "passed": true,
+    "policy": "Docker policy: test18 (version 1)",
+    "port": 2222,
+    "warnings": []
+}

test/docker/expected_results/openssh_8.0p1_custom_policy_test18.txt

@@ -0,0 +1,3 @@
+Host:   localhost:2222
+Policy: Docker policy: test18 (version 1)
+Result: ✔ Passed

test/docker/expected_results/openssh_8.0p1_test1.txt

@@ -104,5 +104,5 @@
 (rec) -umac-64@openssh.com                  -- mac algorithm to remove 
 
 # additional info
-(nfo) For hardening guides on common OSes, please see: <https://www.ssh-audit.com/hardening_guides.html>
+(nfo) For hardening guides on common OSes, a built-in list can be viewed with --list-hardening-guides, or an online list can be found at: <https://www.ssh-audit.com/hardening_guides.html>
 

test/docker/expected_results/openssh_8.0p1_test2.txt

@@ -96,5 +96,5 @@
 (rec) -umac-64@openssh.com                  -- mac algorithm to remove 
 
 # additional info
-(nfo) For hardening guides on common OSes, please see: <https://www.ssh-audit.com/hardening_guides.html>
+(nfo) For hardening guides on common OSes, a built-in list can be viewed with --list-hardening-guides, or an online list can be found at: <https://www.ssh-audit.com/hardening_guides.html>
 

test/docker/expected_results/openssh_8.0p1_test3.txt

@@ -45,5 +45,5 @@
 (rec) -curve25519-sha256@libssh.org         -- kex algorithm to remove 
 
 # additional info
-(nfo) For hardening guides on common OSes, please see: <https://www.ssh-audit.com/hardening_guides.html>
+(nfo) For hardening guides on common OSes, a built-in list can be viewed with --list-hardening-guides, or an online list can be found at: <https://www.ssh-audit.com/hardening_guides.html>
 

test/docker/policies/policy_test18.txt

@@ -0,0 +1,17 @@
+#
+# Docker policy: test18
+#
+
+name = "Docker policy: test18"
+version = 1
+allow_algorithm_subset_and_reordering = false
+allow_hostkey_subset_and_reordering = true
+allow_larger_keys = false
+banner = "SSH-2.0-OpenSSH_8.0"
+compressions = none, zlib@openssh.com
+host keys = ssh-rsa, rsa-sha2-256, rsa-sha2-512, ecdsa-sha2-nistp256, ssh-ed25519, x
+key exchanges = curve25519-sha256, curve25519-sha256@libssh.org, ecdh-sha2-nistp256, ecdh-sha2-nistp384, ecdh-sha2-nistp521, diffie-hellman-group-exchange-sha256, diffie-hellman-group16-sha512, diffie-hellman-group18-sha512, diffie-hellman-group14-sha256, diffie-hellman-group14-sha1
+ciphers = chacha20-poly1305@openssh.com, aes128-ctr, aes192-ctr, aes256-ctr, aes128-gcm@openssh.com, aes256-gcm@openssh.com
+macs = umac-64-etm@openssh.com, umac-128-etm@openssh.com, hmac-sha2-256-etm@openssh.com, hmac-sha2-512-etm@openssh.com, hmac-sha1-etm@openssh.com, umac-64@openssh.com, umac-128@openssh.com, hmac-sha2-256, hmac-sha2-512, hmac-sha1
+host_key_sizes = {"ssh-rsa": {"hostkey_size": 3072}, "rsa-sha2-256": {"hostkey_size": 3072}, "rsa-sha2-512": {"hostkey_size": 3072}, "ssh-ed25519": {"hostkey_size": 256}}
+dh_modulus_sizes = {"diffie-hellman-group-exchange-sha256": 4096}

test/test_hardeningguides.py

@@ -0,0 +1,81 @@
+import pytest
+
+from ssh_audit.hardening_guides import Hardening_Guides
+
+
+class TestHardeningGuides:
+    @pytest.fixture(autouse=True)
+    def init(self, ssh_audit):
+        self.OutputBuffer = ssh_audit.OutputBuffer()
+
+
+    def test_hardening_guides_consistency(self):
+        '''Ensure that the HARDENING_GUIDES struct is consistent.'''
+
+        # Required keys in each guide dict.
+        required_guide_fields = ["server_guide", "version", "version_date", "change_log", "notes", "commands"]
+
+        # Required keys in the commands dict.
+        required_command_fields = ["heading", "comment", "command"]
+
+        for name, guides in Hardening_Guides.HARDENING_GUIDES.items():
+
+            # Ensure the key (guide name) is a string.
+            assert type(name) is str
+
+            # Ensure the value (guides) is a list.
+            assert type(guides) is list
+
+            for guide in guides:
+
+                # Ensure each guide is a dict.
+                assert type(guide) is dict
+
+                # Ensure each required key is in this guide.
+                for required_guide_field in required_guide_fields:
+                    assert required_guide_field in guide
+
+                # Check the guide values are the correct type.
+                assert type(guide["server_guide"]) is bool
+                assert type(guide["version"]) is int
+                assert type(guide["version_date"]) is str
+                assert type(guide["change_log"]) is str
+                assert type(guide["notes"]) is str
+                assert type(guide["commands"]) is list
+
+                # The version must be creater than zero.
+                assert guide["version"] > 0
+
+                # Ensure the format is "YYYY-MM-DD".
+                version_date = guide["version_date"]
+                date_fields = version_date.split("-")
+                assert len(date_fields) == 3
+
+                # Check that the year is 4 digits and greater than 0.
+                year = date_fields[0]
+                assert len(year) == 4
+                assert int(year) > 0
+
+                # Check that the month is 2 digits and between 1 and 12.
+                month = date_fields[1]
+                assert len(month) == 2
+                assert 1 <= int(month) <= 12
+
+                # Check that the day is 2 digits and between 1 and 31.
+                day = date_fields[2]
+                assert len(day) == 2
+                assert 1 <= int(day) <= 31
+
+                # Check that the change log is filled in.
+                assert len(guide["change_log"]) > 0
+
+                commands = guide["commands"]
+                for command in commands:
+
+                    # Ensure each required key is in this command list.
+                    for required_command_field in required_command_fields:
+                        assert required_command_field in command
+
+                    # Check that these fields are not empty.
+                    assert len(command["heading"]) > 0
+                    assert len(command["command"]) > 0

test/test_policy.py

@@ -60,9 +60,6 @@ class TestPolicy:
             except ValueError:
                 assert False, "version field of %s policy is not parseable as an integer." % policy_name
 
-            # Ensure no extra fields are present.
-            assert len(required_fields) == len(BUILTIN_POLICIES[policy_name])
-
             # Ensure that the changelog field is a string and non-empty.
             assert type(BUILTIN_POLICIES[policy_name]['changelog']) is str
             assert len(BUILTIN_POLICIES[policy_name]['changelog']) > 0
@@ -158,7 +155,7 @@ ciphers = cipher_alg1, cipher_alg2, cipher_alg3
 macs = mac_alg1, mac_alg2, mac_alg3'''
 
         policy = self.Policy(policy_data=policy_data)
-        assert str(policy) == "Name: [Test Policy]\nVersion: [1]\nAllow Algorithm Subset and/or Reordering: False\nBanner: {undefined}\nCompressions: comp_alg1\nHost Keys: key_alg1\nOptional Host Keys: {undefined}\nKey Exchanges: kex_alg1, kex_alg2\nCiphers: cipher_alg1, cipher_alg2, cipher_alg3\nMACs: mac_alg1, mac_alg2, mac_alg3\nHost Key Sizes: {undefined}\nDH Modulus Sizes: {undefined}\nServer Policy: True"
+        assert str(policy) == "Name: [Test Policy]\nVersion: [1]\nAllow Algorithm Subset and/or Reordering: False\nAllow Host Key Subset and/or Reordering: False\nBanner: {undefined}\nCompressions: comp_alg1\nHost Keys: key_alg1\nOptional Host Keys: {undefined}\nKey Exchanges: kex_alg1, kex_alg2\nCiphers: cipher_alg1, cipher_alg2, cipher_alg3\nMACs: mac_alg1, mac_alg2, mac_alg3\nHost Key Sizes: {undefined}\nDH Modulus Sizes: {undefined}\nServer Policy: True"
 
 
     def test_policy_invalid_1(self):
@@ -305,7 +302,7 @@ macs = mac_alg1, mac_alg2, mac_alg3'''
         pol_data = pol_data.replace(date.today().strftime('%Y/%m/%d'), '[todays date]')
 
         # Instead of writing out the entire expected policy--line by line--just check that it has the expected hash.
-        assert hashlib.sha256(pol_data.encode('ascii')).hexdigest() == 'fb84bce442cff2bce9bf653d6373a8a938e3bfcfbd1e876f51a08c1842df3cff'
+        assert hashlib.sha256(pol_data.encode('ascii')).hexdigest() == '3862e56ea60c1ecba6dffbf724216c4391b6fe00a790b0075617477d4addf761'
 
 
     def test_policy_evaluate_passing_1(self):