Merge aab105c398 into f326d58068

When evaluating policy compliance, use less-than operator so keys bigger
than expected (and hence very often better) don't fail policy
evaulation. This change reduces the amount of false-positives and allows
for more flexibility when hardening SSH installations.

Signed-off-by: szubersk <szuberskidamian@gmail.com>

Makefile.docker

@@ -4,10 +4,21 @@ ifeq ($(VERSION),)
 endif
 
 all:
-	docker build -t positronsecurity/ssh-audit:${VERSION} .
+	docker buildx create --name multiarch --use || exit 0
+	docker buildx build \
+		--platform linux/amd64,linux/arm64,linux/arm/v7 \
+		--tag positronsecurity/ssh-audit:${VERSION} \
+		--tag positronsecurity/ssh-audit:latest \
+		.
+	docker buildx build \
+		--tag positronsecurity/ssh-audit:${VERSION} \
+		--tag positronsecurity/ssh-audit:latest \
+		--load \
+		--builder=multiarch \
+		.
 
 upload:
-	docker login
+	docker login -u positronsecurity
 	docker buildx build \
 		--platform linux/amd64,linux/arm64,linux/arm/v7 \
 		--tag positronsecurity/ssh-audit:${VERSION} \

PACKAGING.md

@@ -2,7 +2,7 @@
 
 An executable can only be made on a Windows host because the PyInstaller tool (https://www.pyinstaller.org/) does not support cross-compilation.
 
-1.) Install Python v3.11.x from https://www.python.org/.  To make life easier, check the option to add Python to the PATH environment variable.
+1.) Install Python v3.x from https://www.python.org/.  To make life easier, check the option to add Python to the PATH environment variable.
 
 2.) Install Cygwin (https://www.cygwin.com/).
 
@@ -15,7 +15,7 @@ An executable can only be made on a Windows host because the PyInstaller tool (h
 
 # PyPI
 
-To create package and upload to test server:
+To create package and upload to test server (hint: use username '\_\_token\_\_' and API token for test.pypi.org):
 
 ```
     $ sudo apt install python3-virtualenv python3.10-venv
@@ -31,7 +31,7 @@ To download from test server and verify:
     $ pip3 install --index-url https://test.pypi.org/simple ssh-audit
 ```
 
-To upload to production server (hint: use username '\_\_token\_\_' and API token):
+To upload to production server (hint: use username '\_\_token\_\_' and API token for production pypi.org):
 
 ```
     $ make -f Makefile.pypi uploadprod
@@ -61,19 +61,22 @@ Upload the snap with:
     $ snapcraft export-login ~/snap_creds.txt
     $ export SNAPCRAFT_STORE_CREDENTIALS=$(cat ~/snap_creds.txt)
     $ snapcraft upload --release=beta ssh-audit_*.snap
-    $ snapcraft upload --release=stable ssh-audit_*.snap
+    $ snapcraft status ssh-audit  # Note the revision number of the beta channel.
+    $ snapcraft release ssh-audit X stable  # Fill in with the revision number.
 ```
 
 
 # Docker
 
+Ensure that the buildx plugin is available by following the installation instructions available at: https://docs.docker.com/engine/install/ubuntu/
+
 Build a local image with:
 
 ```
     $ make -f Makefile.docker
 ```
 
-Create a multi-architecture build and upload it to Dockerhub with:
+Create a multi-architecture build and upload it to Dockerhub with (hint: use the API token as the password):
 
 ```
     $ make -f Makefile.docker upload

README.md

@@ -178,6 +178,10 @@ For convenience, a web front-end on top of the command-line tool is available at
 
 ## ChangeLog
 
+### v3.2.0-dev (???)
+ - Expanded filter of CBC ciphers to flag for the Terrapin vulnerability.  It now includes more rarely found ciphers.
+ - Color output is disabled if the `NO_COLOR` environment variable is set (see https://no-color.org/).
+
 ### v3.1.0 (2023-12-20)
  - Added test for the Terrapin message prefix truncation vulnerability ([CVE-2023-48795](https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2023-48795)).
  - Dropped support for Python 3.7 (EOL was reached in June 2023).

src/ssh_audit/globals.py

@@ -22,7 +22,7 @@
    THE SOFTWARE.
 """
 # The version to display.
-VERSION = 'v3.1.0'
+VERSION = 'v3.2.0-dev'
 
 # SSH software to impersonate
 SSH_HEADER = 'SSH-{0}-OpenSSH_8.2'

src/ssh_audit/kexdh.py

@@ -80,7 +80,7 @@ class KexDH:  # pragma: nocover
     # contains the host key, among other things.  Function returns the host
     # key blob (from which the fingerprint can be calculated).
     def recv_reply(self, s: 'SSH_Socket', parse_host_key_size: bool = True) -> Optional[bytes]:
-        # Reset the CA info, in case it was set from a prior invokation.
+        # Reset the CA info, in case it was set from a prior invocation.
         self.__hostkey_type = ''
         self.__hostkey_e = 0  # pylint: disable=unused-private-member
         self.__hostkey_n = 0  # pylint: disable=unused-private-member
@@ -100,7 +100,7 @@ class KexDH:  # pragma: nocover
             # A connection error occurred.  We can't parse anything, so just
             # return.  The host key modulus (and perhaps certificate modulus)
             # will remain at length 0.
-            self.out.d("KexDH.recv_reply(): received packge_type == -1.")
+            self.out.d("KexDH.recv_reply(): received package_type == -1.")
             return None
 
         # Get the host key blob, F, and signature.

src/ssh_audit/policy.py

@@ -419,11 +419,11 @@ macs = %s
             hostkey_types = list(self._hostkey_sizes.keys())
             hostkey_types.sort()  # Sorted to make testing output repeatable.
             for hostkey_type in hostkey_types:
-                expected_hostkey_size = self._hostkey_sizes[hostkey_type]['hostkey_size']
+                expected_hostkey_size = cast(int, self._hostkey_sizes[hostkey_type]['hostkey_size'])
                 server_host_keys = kex.host_keys()
                 if hostkey_type in server_host_keys:
-                    actual_hostkey_size = server_host_keys[hostkey_type]['hostkey_size']
-                    if actual_hostkey_size != expected_hostkey_size:
+                    actual_hostkey_size = cast(int, server_host_keys[hostkey_type]['hostkey_size'])
+                    if actual_hostkey_size < expected_hostkey_size:
                         ret = False
                         self._append_error(errors, 'Host key (%s) sizes' % hostkey_type, [str(expected_hostkey_size)], None, [str(actual_hostkey_size)])
 
@@ -439,7 +439,7 @@ macs = %s
                             ret = False
                             self._append_error(errors, 'CA signature type', [expected_ca_key_type], None, [actual_ca_key_type])
                         # Ensure that the actual and expected signature sizes match.
-                        elif actual_ca_key_size != expected_ca_key_size:
+                        elif actual_ca_key_size < expected_ca_key_size:
                             ret = False
                             self._append_error(errors, 'CA signature size (%s)' % actual_ca_key_type, [str(expected_ca_key_size)], None, [str(actual_ca_key_size)])
 
@@ -462,7 +462,7 @@ macs = %s
                 expected_dh_modulus_size = self._dh_modulus_sizes[dh_modulus_type]
                 if dh_modulus_type in kex.dh_modulus_sizes():
                     actual_dh_modulus_size = kex.dh_modulus_sizes()[dh_modulus_type]
-                    if expected_dh_modulus_size != actual_dh_modulus_size:
+                    if expected_dh_modulus_size > actual_dh_modulus_size:
                         ret = False
                         self._append_error(errors, 'Group exchange (%s) modulus sizes' % dh_modulus_type, [str(expected_dh_modulus_size)], None, [str(actual_dh_modulus_size)])
 

src/ssh_audit/ssh_audit.py

@@ -106,7 +106,8 @@ def usage(uout: OutputBuffer, err: Optional[str] = None) -> None:
     uout.info('        --lookup=<alg1,alg2,...>    looks up an algorithm(s) without\n                                    connecting to a server')
     uout.info('   -M,  --make-policy=<policy.txt>  creates a policy based on the target server\n                                    (i.e.: the target server has the ideal\n                                    configuration that other servers should\n                                    adhere to)')
     uout.info('   -m,  --manual           print the man page (Windows only)')
-    uout.info('   -n,  --no-colors        disable colors')
+    uout.info('   -n,  --no-colors        disable colors (automatic when the NO_COLOR')
+    uout.info('                                  environment variable is set)')
     uout.info('   -p,  --port=<port>      port to connect')
     uout.info('   -P,  --policy=<policy.txt>  run a policy test using the specified policy')
     uout.info('   -t,  --timeout=<secs>   timeout (in seconds) for connection and reading\n                               (default: 5)')
@@ -491,7 +492,7 @@ def post_process_findings(banner: Optional[Banner], algs: Algorithms, client_aud
         if algs.ssh2kex is not None:
             ciphers_supported = algs.ssh2kex.client.encryption if client_audit else algs.ssh2kex.server.encryption
             for cipher in ciphers_supported:
-                if cipher.endswith("-cbc"):
+                if cipher.endswith("-cbc") or cipher.endswith("-cbc@openssh.org") or cipher.endswith("-cbc@ssh.com") or cipher == "rijndael-cbc@lysator.liu.se":
                     ret.append(cipher)
 
         return ret
@@ -501,7 +502,7 @@ def post_process_findings(banner: Optional[Banner], algs: Algorithms, client_aud
         ret = []
 
         for cipher in db["enc"]:
-            if cipher.endswith("-cbc") and cipher not in _get_cbc_ciphers_enabled(algs):
+            if (cipher.endswith("-cbc") or cipher.endswith("-cbc@openssh.org") or cipher.endswith("-cbc@ssh.com") or cipher == "rijndael-cbc@lysator.liu.se") and cipher not in _get_cbc_ciphers_enabled(algs):
                 ret.append(cipher)
 
         return ret
@@ -814,6 +815,7 @@ def list_policies(out: OutputBuffer) -> None:
         out.fail("Error: no built-in policies found!")
     else:
         out.info("\nHint: Use -P and provide the full name of a policy to run a policy scan with.\n")
+        out.info("Note: the general OpenSSH policies apply to the official releases only. OS distributions may back-port changes that cause failures (for example, Debian 11 back-ported the strict KEX mode into their package of OpenSSH v8.4, whereas it was only officially added to OpenSSH v9.6 and later).  In these cases, consider creating a custom policy (-M option).\n")
     out.write()
 
 
@@ -857,6 +859,11 @@ def process_commandline(out: OutputBuffer, args: List[str], usage_cb: Callable[.
     aconf = AuditConf()
 
     enable_colors = not any(i in args for i in ['--no-colors', '-n'])
+
+    # Disable colors if the NO_COLOR environment variable is set.
+    if "NO_COLOR" in os.environ:
+        enable_colors = False
+
     aconf.colors = enable_colors
     out.use_colors = enable_colors
 

src/ssh_audit/versionvulnerabilitydb.py

@@ -122,7 +122,7 @@ class VersionVulnerabilityDB:  # pylint: disable=too-few-public-methods
             ['2.1',     '4.1p1',   1, 'CVE-2005-2798',  5.0, 'leak data about authentication credentials'],
             ['3.5',     '3.5p1',   1, 'CVE-2004-2760',  6.8, 'leak data through different connection states'],
             ['2.3',     '3.7.1p2', 1, 'CVE-2004-2069',  5.0, 'cause DoS via large number of connections (slot exhaustion)'],
-            ['3.0',     '3.4p1',   1, 'CVE-2004-0175',  4.3, 'leak data through directoy traversal'],
+            ['3.0',     '3.4p1',   1, 'CVE-2004-0175',  4.3, 'leak data through directory traversal'],
             ['1.2',     '3.9p1',   1, 'CVE-2003-1562',  7.6, 'leak data about authentication credentials'],
             ['3.1p1',   '3.7.1p1', 1, 'CVE-2003-0787',  7.5, 'privilege escalation via modifying stack'],
             ['3.1p1',   '3.7.1p1', 1, 'CVE-2003-0786', 10.0, 'privilege escalation via bypassing authentication'],

ssh-audit.1

@@ -1,4 +1,4 @@
-.TH SSH-AUDIT 1 "March 13, 2022"
+.TH SSH-AUDIT 1 "January 28, 2024"
 .SH NAME
 \fBssh-audit\fP \- SSH server & client configuration auditor
 .SH SYNOPSIS
@@ -114,7 +114,7 @@ Creates a policy based on the target server.  Useful when other servers should b
 .TP
 .B -n, \-\-no-colors
 .br
-Disable color output.
+Disable color output.  Automatically set when the NO_COLOR environment variable is set.
 
 .TP
 .B -p, \-\-port=<port>