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

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

- [Features](#features)
- [Usage](#usage)
- [Screenshots](#screenshots)
    - [Server Standard Audit Example](#server-standard-audit-example)
    - [Server Policy Audit Example](#server-policy-audit-example)
    - [Client Standard Audit Example](#client-standard-audit-example)
- [Hardening Guides](#hardening-guides)
- [Pre-Built Packages](#pre-built-packages)
- [Web Front-End](#web-front-end)
- [ChangeLog](#changelog)

## 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;
- supports Python 3.8 - 3.12;
- 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)
        --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.
   -d,  --debug            Enable debug output.
        --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).
   -g,  --gex-test=<x[,y,...]>  dh gex modulus size test
                   <min1:pref1:max1[,min2:pref2:max2,...]>
                   <x-y[:step]>
   -j,  --json             JSON output (use -jj to enable indents)
   -l,  --level=<level>    minimum output level (info|warn|fail)
   -L,  --list-policies    list all the official, built-in policies. Use with -v
                               to view policy change logs.
        --lookup=<alg1,alg2,...>    looks up an algorithm(s) without
                                    connecting to a server
   -m,  --manual           print the man page (Docker, PyPI, Snap, and Windows
                                    builds only)
   -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
        --skip-rate-test   skip the connection rate test during standard audits
                               (used to safely infer whether the DHEat attack
                               is viable)
   -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])
        --threads=<threads>    number of threads to use when scanning multiple
                                   targets (-T/--targets) (default: 32)
   -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 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](https://nvd.nist.gov/vuln/detail/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:
![screenshot](https://user-images.githubusercontent.com/2982011/64388792-317e6f80-d00e-11e9-826e-a4934769bb07.png)

### 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`):
![screenshot](https://user-images.githubusercontent.com/2982011/94370881-95178700-00c0-11eb-8705-3157a4669dc0.png)

After applying the steps in the hardening guide (see below), the output changes to the following:
![screenshot](https://user-images.githubusercontent.com/2982011/94370873-87620180-00c0-11eb-9a59-469f61a56ce1.png)

### Client Standard Audit Example
Below is a screen shot of the client-auditing output when an unhardened OpenSSH v7.2 client connects:
![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)

## 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:

To install from PyPI:
```
$ pip3 install ssh-audit
```

To install the Snap package:
```
$ snap 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`)

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

<a href="https://repology.org/project/ssh-audit/versions"><img src="https://repology.org/badge/vertical-allrepos/ssh-audit.svg?columns=4" alt="Packaging status" align="center"></a>

## Web Front-End
For convenience, a web front-end on top of the command-line tool is available at [https://www.ssh-audit.com/](https://www.ssh-audit.com/).

## ChangeLog

### v3.2.0 (2024-04-22)
 - Added implementation of the DHEat denial-of-service attack (see `--dheat` option; [CVE-2002-20001](https://nvd.nist.gov/vuln/detail/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](https://github.com/dallemon).
 - 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 [yannik1015](https://github.com/yannik1015).
 - Custom policies now support the `allow_larger_keys` directive to allow targets to pass with larger host keys, CA keys, and Diffie-Hellman keys.  This allows for the creation of a baseline policy where targets can optionally implement stricter controls; partial credit [Damian Szuberski](https://github.com/szubersk).
 - Color output is disabled if the `NO_COLOR` environment variable is set (see https://no-color.org/).
 - Added 1 new key exchange algorithm: `gss-nistp384-sha384-*`.
 - Added 1 new cipher: `aes128-ocb@libassh.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).
 - Added Python 3.12 support.
 - In server policies, reduced expected DH modulus sizes from 4096 to 3072 to match the [online hardening guides](https://ssh-audit.com/hardening_guides.html) (note that 3072-bit moduli provide the equivalent of 128-bit symmetric security).
 - In Ubuntu 22.04 client policy, moved host key types `sk-ssh-ed25519@openssh.com` 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](https://github.com/thecliguy).
 - Hostname resolution failure no longer causes scans against multiple hosts to terminate unexpectedly; credit [Dani Cuesta](https://github.com/daniel-cues).
 - Algorithm recommendations resulting from warnings are now printed in yellow instead of red; credit [Adam Russell](https://github.com/thecliguy).
 - 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](https://github.com/BareqAZ).
 - Docker Makefile now creates multi-arch builds for amd64, arm64, and armv7; credit [Sebastian Cohnen](https://github.com/tisba).
 - 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`, `ecdsa-sha2-nistk409`, `ecdsa-sha2-nistp224`, `ecdsa-sha2-nistp192`, `ecdsa-sha2-nistt571`, `ssh-dsa`, `x509v3-sign-rsa-sha256`.
 - Added 15 new key exchanges: `curve448-sha512@libssh.org`, `ecdh-nistp256-kyber-512r3-sha256-d00@openquantumsafe.org`, `ecdh-nistp384-kyber-768r3-sha384-d00@openquantumsafe.org`, `ecdh-nistp521-kyber-1024r3-sha512-d00@openquantumsafe.org`, `ecdh-sha2-brainpoolp256r1@genua.de`, `ecdh-sha2-brainpoolp384r1@genua.de`, `ecdh-sha2-brainpoolp521r1@genua.de`, `kexAlgoDH14SHA1`, `kexAlgoDH1SHA1`, `kexAlgoECDH256`, `kexAlgoECDH384`, `kexAlgoECDH521`, `sm2kep-sha2-nistp256`, `x25519-kyber-512r3-sha256-d00@amazon.com`, `x25519-kyber512-sha512@aws.amazon.com`.
 - Added 8 new ciphers: `aes192-gcm@openssh.com`, `cast128-12-cbc`, `cast128-12-cfb`, `cast128-12-ecb`, `cast128-12-ofb`, `des-cfb`, `des-ecb`, `des-ofb`.
 - Added 14 new MACs: `cbcmac-3des`, `cbcmac-aes`, `cbcmac-blowfish`, `cbcmac-des`, `cbcmac-rijndael`, `cbcmac-twofish`, `hmac-sha256-96`, `md5`, `md5-8`, `ripemd160`, `ripemd160-8`, `sha1`, `sha1-8`, `umac-128`.

### 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 `sntrup761x25519-sha512@openssh.com`.
 - Updated CVE database; credit [Alexandre Zanni](https://github.com/noraj).
 - Added `-g` and `--gex-test` for granular GEX modulus size tests; credit [Adam Russell](https://github.com/thecliguy).
 - Snap packages now print more user-friendly error messages when permission errors are encountered.
 - JSON 'target' field now always includes port number; credit [tomatohater1337](https://github.com/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](https://github.com/thecliguy).
 - 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: `dsa2048-sha224@libassh.org`, `dsa2048-sha256@libassh.org`, `dsa3072-sha256@libassh.org`, `ecdsa-sha2-1.3.132.0.10-cert-v01@openssh.com`, `eddsa-e382-shake256@libassh.org`, `eddsa-e521-shake256@libassh.org`, `null`, `pgp-sign-dss`, `pgp-sign-rsa`, `spki-sign-dss`, `spki-sign-rsa`, `ssh-dss-sha224@ssh.com`, `ssh-dss-sha384@ssh.com`, `ssh-dss-sha512@ssh.com`, `ssh-ed448-cert-v01@openssh.com`, `ssh-rsa-sha224@ssh.com`, `ssh-rsa-sha2-256`, `ssh-rsa-sha2-512`, `ssh-rsa-sha384@ssh.com`, `ssh-rsa-sha512@ssh.com`, `ssh-xmss-cert-v01@openssh.com`, `ssh-xmss@openssh.com`, `webauthn-sk-ecdsa-sha2-nistp256@openssh.com`, `x509v3-ecdsa-sha2-1.3.132.0.10`, `x509v3-sign-dss-sha1`, `x509v3-sign-dss-sha224@ssh.com`, `x509v3-sign-dss-sha256@ssh.com`, `x509v3-sign-dss-sha384@ssh.com`, `x509v3-sign-dss-sha512@ssh.com`, `x509v3-sign-rsa-sha1`, `x509v3-sign-rsa-sha224@ssh.com`, `x509v3-sign-rsa-sha384@ssh.com`, `x509v3-sign-rsa-sha512@ssh.com`.
 - Added 46 new key exchanges: `diffie-hellman-group14-sha224@ssh.com`, `diffie-hellman_group17-sha512`, `diffie-hellman-group-exchange-sha224@ssh.com`, `diffie-hellman-group-exchange-sha384@ssh.com`, `ecdh-sha2-1.2.840.10045.3.1.1`, `ecdh-sha2-1.2.840.10045.3.1.7`, `ecdh-sha2-1.3.132.0.1`, `ecdh-sha2-1.3.132.0.16`, `ecdh-sha2-1.3.132.0.26`, `ecdh-sha2-1.3.132.0.27`, `ecdh-sha2-1.3.132.0.33`, `ecdh-sha2-1.3.132.0.34`, `ecdh-sha2-1.3.132.0.35`, `ecdh-sha2-1.3.132.0.36`, `ecdh-sha2-1.3.132.0.37`, `ecdh-sha2-1.3.132.0.38`, `ecdh-sha2-4MHB+NBt3AlaSRQ7MnB4cg==`, `ecdh-sha2-5pPrSUQtIaTjUSt5VZNBjg==`, `ecdh-sha2-9UzNcgwTlEnSCECZa7V1mw==`, `ecdh-sha2-D3FefCjYoJ/kfXgAyLddYA==`, `ecdh-sha2-h/SsxnLCtRBh7I9ATyeB3A==`, `ecdh-sha2-m/FtSAmrV4j/Wy6RVUaK7A==`, `ecdh-sha2-mNVwCXAoS1HGmHpLvBC94w==`, `ecdh-sha2-qCbG5Cn/jjsZ7nBeR7EnOA==`, `ecdh-sha2-qcFQaMAMGhTziMT0z+Tuzw==`, `ecdh-sha2-VqBg4QRPjxx1EXZdV0GdWQ==`, `ecdh-sha2-wiRIU8TKjMZ418sMqlqtvQ==`, `ecdh-sha2-zD/b3hu/71952ArpUG4OjQ==`, `ecmqv-sha2`, `gss-13.3.132.0.10-sha256-*`, `gss-curve25519-sha256-*`, `gss-curve448-sha512-*`, `gss-gex-sha1-*`, `gss-gex-sha256-*`, `gss-group14-sha1-*`, `gss-group14-sha256-*`, `gss-group15-sha512-*`, `gss-group16-sha512-*`, `gss-group17-sha512-*`, `gss-group18-sha512-*`, `gss-group1-sha1-*`, `gss-nistp256-sha256-*`, `gss-nistp384-sha256-*`, `gss-nistp521-sha512-*`, `m383-sha384@libassh.org`, `m511-sha512@libassh.org`.
 - Added 28 new ciphers: `3des-cfb`, `3des-ecb`, `3des-ofb`, `blowfish-cfb`, `blowfish-ecb`, `blowfish-ofb`, `camellia128-cbc@openssh.org`, `camellia128-ctr@openssh.org`, `camellia192-cbc@openssh.org`, `camellia192-ctr@openssh.org`, `camellia256-cbc@openssh.org`, `camellia256-ctr@openssh.org`, `cast128-cfb`, `cast128-ecb`, `cast128-ofb`, `cast128-12-cbc@ssh.com`, `idea-cfb`, `idea-ecb`, `idea-ofb`, `rijndael-cbc@ssh.com`, `seed-ctr@ssh.com`, `serpent128-gcm@libassh.org`, `serpent256-gcm@libassh.org`, `twofish128-gcm@libassh.org`, `twofish256-gcm@libassh.org`, `twofish-cfb`, `twofish-ecb`, `twofish-ofb`
 - Added 5 new MACs: `hmac-sha1-96@openssh.com`, `hmac-sha224@ssh.com`, `hmac-sha256-2@ssh.com`, `hmac-sha384@ssh.com`, `hmac-whirlpool`.

### 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](https://github.com/thecliguy).
 - 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](https://github.com/thecliguy).
 - 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: `sntrup761x25519-sha512@openssh.com`.

### 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](https://github.com/thecliguy).
 - 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](https://github.com/gschaffner).
 - 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](https://github.com/jugmac00).
 - Added feature to look up algorithms in internal database (see `--lookup`); credit [Adam Russell](https://github.com/thecliguy).
 - 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](https://eprint.iacr.org/2020/014.pdf).
 - 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](https://github.com/x-way)).
 - 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
