SSH1 and SSH2 protocol server support;
analyze SSH client configuration;
grab banner, recognize device or software and operating system, detect compression;
gather key-exchange, host-key, encryption and message authentication code algorithms;
output algorithm information (available since, removed/disabled, unsafe/weak/legacy, etc);
output algorithm recommendations (append or remove based on recognized software version);
output security information (related issues, assigned CVE list, etc);
analyze SSH version compatibility based on algorithm information;
historical information from OpenSSH, Dropbear SSH and libssh;
policy scans to ensure adherence to a hardened/standard configuration;
runs on Linux and Windows;
no dependencies

Usage

usage: ssh-audit.py [options] <host>

   -h,  --help             print this help
   -1,  --ssh1             force ssh version 1 only
   -2,  --ssh2             force ssh version 2 only
   -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 to change timeout)
   -j,  --json             JSON output
   -l,  --level=<level>    minimum output level (info|warn|fail)
   -L,  --list-policies    list all the official, built-in policies
        --lookup=<alg1,alg2,...>    looks up an algorithm(s) without
                                    connecting to a server
   -M,  --make-policy=<policy.txt>  creates a policy based on the target server
                                    (i.e.: the target server has the ideal
                                    configuration that other servers should
                                    adhere to)
   -n,  --no-colors        disable colors
   -p,  --port=<port>      port to connect
   -P,  --policy=<"policy name" | policy.txt>  run a policy test using the
                                                   specified policy
   -t,  --timeout=<secs>   timeout (in seconds) for connection and reading
                               (default: 5)
   -T,  --targets=<hosts.txt>  a file containing a list of target hosts (one
                                   per line, format HOST[:PORT])
   -v,  --verbose          verbose output

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).
verbose flag -v will prefix each line with section type and algorithm name.
an exit code of 0 is returned when all algorithms are considered secure (for a standard audit), or when a policy check passes (for a policy audit).

Basic server auditing:

ssh-audit localhost
ssh-audit 127.0.0.1
ssh-audit 127.0.0.1:222
ssh-audit ::1
ssh-audit [::1]:222

To run a standard audit against many servers (place targets into servers.txt, one on each line in the format of HOST[:PORT]):

ssh-audit -T servers.txt

To audit a client configuration (listens on port 2222 by default; connect using ssh -p 2222 anything@localhost):

ssh-audit -c

To audit a client configuration, with a listener on port 4567:

ssh-audit -c -p 4567

To list all official built-in policies (hint: use resulting file paths with -P/--policy):

ssh-audit -L

To run a policy audit against a server:

ssh-audit -P ["policy name" | path/to/server_policy.txt] targetserver

To run a policy audit against a client:

ssh-audit -c -P ["policy name" | path/to/client_policy.txt]

To run a policy audit against many servers:

ssh-audit -T servers.txt -P ["policy name" | path/to/server_policy.txt]

To create a policy based on a target server (which can be manually edited; see official built-in policies for syntax examples):

ssh-audit -M new_policy.txt targetserver

Server Standard Audit Example

Below is a screen shot of the standard server-auditing output when connecting to an unhardened OpenSSH v5.3 service:

Server Policy Audit Example

Below is a screen shot of the policy auditing output when connecting to an un-hardened Ubuntu Server 20.04 machine:

After applying the steps in the hardening guide (see below), the output changes to the following:

Client Standard Audit Example

Below is a screen shot of the client-auditing output when an unhardened OpenSSH v7.2 client connects:

Hardening Guides

Guides to harden server & client configuration can be found here: https://www.ssh-audit.com/hardening_guides.html

Pre-Built Packages

Pre-built packages are available for Windows (see the releases page), on PyPI, Snap, and Homebrew.

To install from PyPI:

$ pip3 install ssh-audit

To install the Snap package:

$ snap install ssh-audit

To install on Homebrew:

$ brew install ssh-audit

To install from Dockerhub:

$ docker pull positronsecurity/ssh-audit

(Then run with: docker run -it -p 2222:2222 positronsecurity/ssh-audit 10.1.1.1)

Web Front-End

For convenience, a web front-end on top of the command-line tool is available at https://www.ssh-audit.com/.

ChangeLog

v2.3.1-dev (???)

Fixed bug in recommendation output which suppressed some algorithms inappropriately.
Flag ssh-rsa-cert-v01@openssh.com as a failure due to SHA-1 hash.
Now parses public key sizes for rsa-sha2-256-cert-v01@openssh.com and rsa-sha2-512-cert-v01@openssh.com host key types.
Built-in policies now include CA key requirements (if certificates are in use).
Migrated pre-made policies from external files to internal database.
Split single 3,500 line script into many files (by class).
Added setup.py support; credit Ganden Schaffner.
Added 1 new cipher: des-cbc@ssh.com.

v2.3.0 (2020-09-27)

Added new policy auditing functionality to test adherence to a hardening guide/standard configuration (see -L/--list-policies, -M/--make-policy and -P/--policy). For an in-depth tutorial, see https://www.positronsecurity.com/blog/2020-09-27-ssh-policy-configuration-checks-with-ssh-audit/.
Created new man page (see ssh-audit.1 file).
1024-bit moduli upgraded from warnings to failures.
Many Python 2 code clean-ups, testing framework improvements, pylint & flake8 fixes, and mypy type comments; credit Jürgen Gmach.
Added feature to look up algorithms in internal database (see --lookup); credit Adam Russell.
Suppress recommendation of token host key types.
Added check for use-after-free vulnerability in PuTTY v0.73.
Added 11 new host key types: ssh-rsa1, ssh-dss-sha256@ssh.com, ssh-gost2001, ssh-gost2012-256, ssh-gost2012-512, spki-sign-rsa, ssh-ed448, x509v3-ecdsa-sha2-nistp256, x509v3-ecdsa-sha2-nistp384, x509v3-ecdsa-sha2-nistp521, x509v3-rsa2048-sha256.
Added 8 new key exchanges: diffie-hellman-group1-sha256, kexAlgoCurve25519SHA256, Curve25519SHA256, gss-group14-sha256-, gss-group15-sha512-, gss-group16-sha512-, gss-nistp256-sha256-, gss-curve25519-sha256-.
Added 5 new ciphers: blowfish, AEAD_AES_128_GCM, AEAD_AES_256_GCM, crypticore128@ssh.com, seed-cbc@ssh.com.
Added 3 new MACs: chacha20-poly1305@openssh.com, hmac-sha3-224, crypticore-mac@ssh.com.

v2.2.0 (2020-03-11)

Marked host key type ssh-rsa as weak due to practical SHA-1 collisions.
Added Windows builds.
Added 10 new host key types: ecdsa-sha2-1.3.132.0.10, x509v3-sign-dss, x509v3-sign-rsa, x509v3-sign-rsa-sha256@ssh.com, x509v3-ssh-dss, x509v3-ssh-rsa, sk-ecdsa-sha2-nistp256-cert-v01@openssh.com, sk-ecdsa-sha2-nistp256@openssh.com, sk-ssh-ed25519-cert-v01@openssh.com, and sk-ssh-ed25519@openssh.com.
Added 18 new key exchanges: diffie-hellman-group14-sha256@ssh.com, diffie-hellman-group15-sha256@ssh.com, diffie-hellman-group15-sha384@ssh.com, diffie-hellman-group16-sha384@ssh.com, diffie-hellman-group16-sha512@ssh.com, diffie-hellman-group18-sha512@ssh.com, ecdh-sha2-curve25519, ecdh-sha2-nistb233, ecdh-sha2-nistb409, ecdh-sha2-nistk163, ecdh-sha2-nistk233, ecdh-sha2-nistk283, ecdh-sha2-nistk409, ecdh-sha2-nistp192, ecdh-sha2-nistp224, ecdh-sha2-nistt571, gss-gex-sha1-, and gss-group1-sha1-.
Added 9 new ciphers: camellia128-cbc, camellia128-ctr, camellia192-cbc, camellia192-ctr, camellia256-cbc, camellia256-ctr, aes128-gcm, aes256-gcm, and chacha20-poly1305.
Added 2 new MACs: aes128-gcm and aes256-gcm.

v2.1.1 (2019-11-26)

Added 2 new host key types: rsa-sha2-256-cert-v01@openssh.com, rsa-sha2-512-cert-v01@openssh.com.
Added 2 new ciphers: des, 3des.
Added 3 new PuTTY vulnerabilities.
During client testing, client IP address is now listed in output.

v2.1.0 (2019-11-14)

Added client software auditing functionality (see -c / --client-audit option).
Added JSON output option (see -j / --json option; credit Andreas Jaggi).
Fixed crash while scanning Solaris Sun_SSH.
Added 9 new key exchanges: gss-group1-sha1-toWM5Slw5Ew8Mqkay+al2g==, gss-gex-sha1-toWM5Slw5Ew8Mqkay+al2g==, gss-group14-sha1-, gss-group14-sha1-toWM5Slw5Ew8Mqkay+al2g==, gss-group14-sha256-toWM5Slw5Ew8Mqkay+al2g==, gss-group15-sha512-toWM5Slw5Ew8Mqkay+al2g==, diffie-hellman-group15-sha256, ecdh-sha2-1.3.132.0.10, curve448-sha512.
Added 1 new host key type: ecdsa-sha2-1.3.132.0.10.
Added 4 new ciphers: idea-cbc, serpent128-cbc, serpent192-cbc, serpent256-cbc.
Added 6 new MACs: hmac-sha2-256-96-etm@openssh.com, hmac-sha2-512-96-etm@openssh.com, hmac-ripemd, hmac-sha256-96@ssh.com, umac-32@openssh.com, umac-96@openssh.com.

v2.0.0 (2019-08-29)

Forked from https://github.com/arthepsy/ssh-audit (development was stalled, and developer went MIA).
Added RSA host key length test.
Added RSA certificate key length test.
Added Diffie-Hellman modulus size test.
Now outputs host key fingerprints for RSA and ED25519.
Added 5 new key exchanges: sntrup4591761x25519-sha512@tinyssh.org, diffie-hellman-group-exchange-sha256@ssh.com, diffie-hellman-group-exchange-sha512@ssh.com, diffie-hellman-group16-sha256, diffie-hellman-group17-sha512.
Added 3 new encryption algorithms: des-cbc-ssh1, blowfish-ctr, twofish-ctr.
Added 10 new MACs: hmac-sha2-56, hmac-sha2-224, hmac-sha2-384, hmac-sha3-256, hmac-sha3-384, hmac-sha3-512, hmac-sha256, hmac-sha256@ssh.com, hmac-sha512, hmac-512@ssh.com.
Added command line argument (-t / --timeout) for connection & reading timeouts.
Updated CVEs for libssh & Dropbear.

v1.7.0 (2016-10-26)

implement options to allow specify IPv4/IPv6 usage and order of precedence
implement option to specify remote port (old behavior kept for compatibility)
add colors support for Microsoft Windows via optional colorama dependency
fix encoding and decoding issues, add tests, do not crash on encoding errors
use mypy-lang for static type checking and verify all code

v1.6.0 (2016-10-14)

implement algorithm recommendations section (based on recognized software)
implement full libssh support (version history, algorithms, security, etc)
fix SSH-1.99 banner recognition and version comparison functionality
do not output empty algorithms (happens for misconfigured servers)
make consistent output for Python 3.x versions
add a lot more tests (conf, banner, software, SSH1/SSH2, output, etc)
use Travis CI to test for multiple Python versions (2.6-3.5, pypy, pypy3)

v1.5.0 (2016-09-20)

create security section for related security information
match and output assigned CVE list and security issues for Dropbear SSH
implement full SSH1 support with fingerprint information
automatically fallback to SSH1 on protocol mismatch
add new options to force SSH1 or SSH2 (both allowed by default)
parse banner information and convert it to specific software and OS version
do not use padding in batch mode
several fixes (Cisco sshd, rare hangs, error handling, etc)

v1.0.20160902

implement batch output option
implement minimum output level option
fix compatibility with Python 2.6

v1.0.20160812

implement SSH version compatibility feature
fix wrong mac algorithm warning
fix Dropbear SSH version typo
parse pre-banner header
better errors handling

v1.0.20160803

use OpenSSH 7.3 banner
add new key-exchange algorithms

v1.0.20160207

use OpenSSH 7.2 banner
additional warnings for OpenSSH 7.2
fix OpenSSH 7.0 failure messages
add rijndael-cbc failure message from OpenSSH 6.7

v1.0.20160105

multiple additional warnings
support for none algorithm
better compression handling
ensure reading enough data (fixes few Linux SSH)

v1.0.20151230

Dropbear SSH support

v1.0.20151223

initial version

Languages

Python 90.8%

Shell 6.5%

Roff 1.9%

Batchfile 0.6%

Dockerfile 0.2%