ssh-audit

ssh-audit is a tool for ssh server & client configuration auditing.

jtesta/ssh-audit (v2.0+) is the updated and maintained version of ssh-audit forked from arthepsy/ssh-audit (v1.x) due to inactivity.

Features

• 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

v2.4.0-dev (???)

• Added version check for OpenSSH user enumeration (CVE-2018-15473).
• Fixed crash when receiving unexpected response during host key test.
• Fixed hang against older Cisco devices during host key test & gex test.
• Dropped support for Python 3.5 (which reached EOL in Sept. 2020).

v2.3.1 (2020-10-28)

• Now parses public key sizes for rsa-sha2-256-cert-v01@openssh.com and rsa-sha2-512-cert-v01@openssh.com host key types.
• Flag ssh-rsa-cert-v01@openssh.com as a failure due to SHA-1 hash.
• Fixed bug in recommendation output which suppressed some algorithms inappropriately.
• Built-in policies now include CA key requirements (if certificates are in use).
• Lookup function (--lookup) now performs case-insensitive lookups of similar algorithms; credit Adam Russell.
• 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