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
• Usage
• Screenshots
  • Server Standard Audit Example
  • Server Policy Audit Example
  • Client Standard Audit Example
• Hardening Guides
• Pre-Built Packages
• Web Front-End
• ChangeLog

Features

• analyze SSH both server and 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 security information (available since, removed/disabled, unsafe/weak/legacy, etc);
• output algorithm recommendations (append or remove based on recognized software version);
• 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;
• supports Python 3.10 - 3.14;
• 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] [-M custom_policy.txt]
                    [-m] [-n] [-P "Built-In Policy Name" / custom_policy.txt]
                    [-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]
                    [--socks5 host:port] [--threads N]
                    [host]

# ssh-audit.py v3.4.1-dev, https://github.com/jtesta/ssh-audit

positional arguments:
  host                  target hostname or IPv4/IPv6 address

optional arguments:
  -h, --help            show this help message and exit
  -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)
  -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, preferred, and
                        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
  -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 configuration that other
                        servers should adhere to), and stores it in the file
                        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 filesystem path
                        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]'; for UNIX socket servers,
                        use 'unix:///path/socket'). Use -p/--port to set the
                        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 the DHEat vuln).
                        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 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).
  --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.
  --skip-rate-test      skip the connection rate test during standard audits
                        (used to safely infer whether the DHEat attack is
                        viable)
  --socks5 host:port    connect via a SOCKS5 proxy (implies --skip-rate-test)
  --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).
• 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
ssh-audit unix:///run/ssh-unix-local/socket

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/tcp by default; connect using ssh -p 2222 anything@localhost):

ssh-audit -c

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

ssh-audit -c -p 4567

To list all official built-in policies (hint: use resulting policy names 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):

ssh-audit -M new_policy.txt targetserver

To run the DHEat CPU exhaustion DoS attack (CVE-2002-20001) against a target using 10 concurrent sockets:

ssh-audit --dheat=10 targetserver

To run the DHEat attack using the diffie-hellman-group-exchange-sha256 key exchange algorithm:

ssh-audit --dheat=10:diffie-hellman-group-exchange-sha256 targetserver

To run the DHEat attack using the diffie-hellman-group-exchange-sha256 key exchange algorithm along with very small but non-standard packet lengths (this may result in the same CPU exhaustion, but with many less bytes per second being sent):

ssh-audit --dheat=10:diffie-hellman-group-exchange-sha256:4 targetserver

Screenshots

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 (hint: use -L/--list-policies to see names of built-in policies to use with -P/--policy):

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 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

Pre-Built Packages

Pre-built packages are available for Windows (see the Releases page), PyPI, Snap, and Docker:

To install from PyPI:

$ pip3 install ssh-audit

To install the Snap package:

$ snap install ssh-audit

To install from Dockerhub:

$ docker pull docker.io/positronsecurity/ssh-audit

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

The status of various other platform packages can be found below (via Repology):

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

v3.9.1-dev

• Fixed a perhaps rare crash when performing connection rate tests during standard audits.

v3.9.0 (2026-07-04)

• BIG THANKS to realmiwi for being the project's very first sponsor!!
• Added support for Python 3.14.
• Dropped support for Python 3.8, as it reached end-of-life in October 2024.
• Dropped support for Python 3.9, as it reached end-of-life in October 2025.
• 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.
• 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.
• 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 flag.

v3.3.0 (2024-10-15)

• Added Python 3.13 support.
• Added built-in policies for Ubuntu 24.04 LTS server & client, OpenSSH 9.8, and OpenSSH 9.9.
• Added IPv6 support for DHEat and connection rate tests.
• Added TCP port information to JSON policy scan results; credit Fabian Malte Kopp.
• Added LANcom LCOS server recognition and Ed448 key extraction; credit Daniel Lenski.
• Now reports ECDSA and DSS fingerprints when in verbose mode; partial credit Daniel Lenski.
• Removed CVE information based on server/client version numbers, as this was wildly inaccurate (see this thread for the full discussion, as well as the results of the community vote on this matter).
• Fixed crash when running with -P and -T options simultaneously.
• Fixed host key tests from only reporting a key type at most once despite multiple hosts supporting it; credit Daniel Lenski.
• Fixed DHEat connection rate testing on MacOS X and BSD platforms; credit Drew Noel and Michael Osipov.
• Fixed invalid JSON output when a socket error occurs while performing a client audit.
• Fixed --conn-rate-test feature on Windows.
• When scanning multiple targets (using -T/--targets), the -p/--port option will now be used as the default port (set to 22 if / is not given). Hosts specified in the file can override this default with an explicit port number (i.e.: "host1:1234"). For example, when using , all hosts in that do not explicitly include a port number will default to 222; when using (without ), all hosts will use a default of 22.

v3.2.0 (2024-04-22)

• Added implementation of the DHEat denial-of-service attack (see --dheat option; CVE-2002-20001).
• Expanded filter of CBC ciphers to flag for the Terrapin vulnerability. It now includes more rarely found ciphers.
• Fixed parsing of ecdsa-sha2-nistp* CA signatures on host keys. Additionally, they are now flagged as potentially back-doored, just as standard host keys are.
• Gracefully handle rare exceptions (i.e.: crashes) while performing GEX tests.
• The built-in man page (-m, --manual) is now available on Docker, PyPI, and Snap builds, in addition to the Windows build.
• Snap builds are now architecture-independent.
• Changed Docker base image from python:3-slim to python:3-alpine, resulting in a 59% reduction in image size; credit Daniel Thamdrup.
• Added built-in policies for Amazon Linux 2023, Debian 12, OpenSSH 9.7, and Rocky Linux 9.
• Built-in policies now include a change log (use -L -v to view them).
• Custom policies now support the allow_algorithm_subset_and_reordering directive to allow targets to pass with a subset and/or re-ordered list of host keys, kex, ciphers, and MACs. This allows for the creation of a baseline policy where targets can optionally implement stricter controls; partial credit .

v3.1.0 (2023-12-20)

• Added test for the Terrapin message prefix truncation vulnerability (CVE-2023-48795).
• Dropped support for Python 3.7 (EOL was reached in June 2023).
• Added Python 3.12 support.
• In server policies, reduced expected DH modulus sizes from 4096 to 3072 to match the online hardening guides (note that 3072-bit moduli provide the equivalent of 128-bit symmetric security).
• In Ubuntu 22.04 client policy, moved host key types [email protected] and ssh-ed25519 to the end of all certificate types.
• Updated Ubuntu Server & Client policies for 20.04 and 22.04 to account for key exchange list changes due to Terrapin vulnerability patches.
• Re-organized option host key types for OpenSSH 9.2 server policy to correspond with updated Debian 12 hardening guide.
• Added built-in policies for OpenSSH 9.5 and 9.6.
• Added an additional_notes field to the JSON output.

v3.0.0 (2023-09-07)

• Results from concurrent scans against multiple hosts are no longer improperly combined; bug discovered by Adam Russell.
• Hostname resolution failure no longer causes scans against multiple hosts to terminate unexpectedly; credit Dani Cuesta.
• Algorithm recommendations resulting from warnings are now printed in yellow instead of red; credit Adam Russell.
• Added failure, warning, and info notes to JSON output (note that this results in a breaking change to the banner protocol, "enc", and "mac" fields); credit Bareq Al-Azzawi.
• Docker Makefile now creates multi-arch builds for amd64, arm64, and armv7; credit Sebastian Cohnen.
• Fixed crash during GEX tests.
• Refined GEX testing against OpenSSH servers: when the fallback mechanism is suspected of being triggered, perform an additional test to obtain more accurate results.
• The color of all notes will be printed in green when the related algorithm is rated good.
• Prioritized host key certificate algorithms for Ubuntu 22.04 LTS client policy.
• Marked all NIST K-, B-, and T-curves as unproven since they are so rarely used.
• Added built-in policy for OpenSSH 9.4.
• Added 12 new host keys: ecdsa-sha2-curve25519, ecdsa-sha2-nistb233, ecdsa-sha2-nistb409, ecdsa-sha2-nistk163, ecdsa-sha2-nistk233, ecdsa-sha2-nistk283, , , , , , .

v2.9.0 (2023-04-29)

• Dropped support for Python 3.6, as it reached EOL at the end of 2021.
• Added Ubuntu Server & Client 22.04 hardening policies.
• Removed experimental warning tag from [email protected].
• Updated CVE database; credit Alexandre Zanni.
• Added -g and --gex-test for granular GEX modulus size tests; credit Adam Russell.
• Snap packages now print more user-friendly error messages when permission errors are encountered.
• JSON 'target' field now always includes port number; credit tomatohater1337.
• JSON output now includes recommendations and CVE data.
• Mixed host key/CA key types (i.e.: RSA host keys signed with ED25519 CAs, etc.) are now properly handled.
• Warnings are now printed for 2048-bit moduli; partial credit Adam Russell.
• SHA-1 algorithms now cause failures.
• CBC mode ciphers are now warnings instead of failures.
• Generic failure/warning messages replaced with more specific reasons (i.e.: 'using weak cipher' => 'using broken RC4 cipher').
• Updated built-in policies to include missing host key size information.
• Added built-in policies for OpenSSH 8.8, 8.9, 9.0, 9.1, 9.2, and 9.3.
• Added 33 new host keys: [email protected], [email protected], [email protected], [email protected], , , , , , , , , , , , , , , , , , , , , , , , , , , , , .

v2.5.0 (2021-08-26)

• Fixed crash when running host key tests.
• Handles server connection failures more gracefully.
• Now prints JSON with indents when -jj is used (useful for debugging).
• Added MD5 fingerprints to verbose output.
• Added -d/--debug option for getting debugging output; credit Adam Russell.
• Updated JSON output to include MD5 fingerprints. Note that this results in a breaking change in the 'fingerprints' dictionary format.
• Updated OpenSSH 8.1 (and earlier) policies to include rsa-sha2-512 and rsa-sha2-256.
• Added OpenSSH v8.6 & v8.7 policies.
• Added 3 new key exchanges: gss-gex-sha1-eipGX3TCiQSrx573bT1o1Q==, gss-group1-sha1-eipGX3TCiQSrx573bT1o1Q==, and gss-group14-sha1-eipGX3TCiQSrx573bT1o1Q==.
• Added 3 new MACs: hmac-ripemd160-96, AEAD_AES_128_GCM, and AEAD_AES_256_GCM.

v2.4.0 (2021-02-23)

• Added multi-threaded scanning support.
• Added built-in Windows manual page (see -m/--manual); credit Adam Russell.
• Added version check for OpenSSH user enumeration (CVE-2018-15473).
• Added deprecation note to host key types based on SHA-1.
• Added extra warnings for SSHv1.
• Added built-in hardened OpenSSH v8.5 policy.
• Upgraded warnings to failures for host key types based on SHA-1.
• Fixed crash when receiving unexpected response during host key test.
• Fixed hang against older Cisco devices during host key test & gex test.
• Fixed improper termination while scanning multiple targets when one target returns an error.
• Dropped support for Python 3.5 (which reached EOL in Sept. 2020).
• Added 1 new key exchange: [email protected].

v2.3.1 (2020-10-28)

• Now parses public key sizes for [email protected] and [email protected] host key types.
• Flag [email protected] 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: [email protected].

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, [email protected], , , , , , , , , .

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, [email protected], x509v3-ssh-dss, x509v3-ssh-rsa, [email protected], [email protected], [email protected], and [email protected].
• Added 18 new key exchanges: [email protected], , , , , , , , , , , , , , , , , and .

v2.1.1 (2019-11-26)

• Added 2 new host key types: [email protected], [email protected].
• 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, .

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: [email protected], [email protected], [email protected], 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, , , , , , , .

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