SSHScan

SSHScan is a remote auditing tool that enumerates SSH server cryptographic algorithms. It helps identify insecure and not recommended ciphers, key exchange algorithms, MACs, and host key algorithms.

Requirements

SSHScan requires Python 3.8 or newer and has no dependency on third-party packages. It uses only the Python standard library.

Installation

git clone https://github.com/farrokhi/SSHScan
cd SSHScan

Usage

Basic usage:

./sshscan.py host.example.com

Specify a custom port:

./sshscan.py host.example.com:2222

IPv6 addresses must be enclosed in brackets and quoted:

./sshscan.py '[2001:db8::1]:22'
./sshscan.py '[::1]'

Display help:

./sshscan.py -h

Sample output:

% ./sshscan.py sdf.org

[*] Initiating scan for sdf.org on port 22
[*] Connected to sdf.org on port 22...
    [+] Target SSH version is: SSH-2.0-OpenSSH_10.0
    [+] Retrieving algorithm information...
    [+] Detected ciphers:
          chacha20-poly1305@openssh.com        aes128-ctr
          aes128-gcm@openssh.com               aes192-ctr
          aes256-gcm@openssh.com               aes256-ctr
    [+] Detected KEX algorithms:
          mlkem768x25519-sha256                ecdh-sha2-nistp256
          sntrup761x25519-sha512               ecdh-sha2-nistp384
          sntrup761x25519-sha512@openssh.com   ecdh-sha2-nistp521
          curve25519-sha256                    ext-info-s
          curve25519-sha256@libssh.org         kex-strict-s-v00@openssh.com
    [+] Detected MACs:
          umac-64-etm@openssh.com              umac-64@openssh.com
          umac-128-etm@openssh.com             umac-128@openssh.com
          hmac-sha2-256-etm@openssh.com        hmac-sha2-256
          hmac-sha2-512-etm@openssh.com        hmac-sha2-512
          hmac-sha1-etm@openssh.com            hmac-sha1
    [+] Detected HostKey algorithms:
          rsa-sha2-512                         ssh-ed25519
          rsa-sha2-256
    [-] No not recommended ciphers detected!
    [+] Detected not recommended KEX algorithms:
          ecdh-sha2-nistp256                   ecdh-sha2-nistp521
          ecdh-sha2-nistp384
    [+] Detected not recommended MACs:
          umac-64-etm@openssh.com              umac-64@openssh.com
          hmac-sha1-etm@openssh.com            hmac-sha1
    [-] No not recommended HostKey algorithms detected!
    [+] Compression is enabled

Algorithm Classifications

SSHScan categorizes algorithms as either recommended or not recommended based on current cryptographic research and security best practices.

Algorithms flagged as "not recommended" include:

• Cryptographically broken algorithms such as RC4 (bias attacks), 64-bit block ciphers like 3DES and Blowfish (Sweet32 birthday attack), AES-CBC without Encrypt-then-MAC (padding oracle attacks), and algorithms using SHA-1 signatures like ssh-rsa (vulnerable to chosen-prefix collisions)

• Algorithms deprecated due to reduced security margins such as HMAC-SHA1 (theoretically secure but phased out) and UMAC-64 (insufficient birthday security)

• Algorithms not recommended for policy or trust reasons such as NIST P-curves (ecdh-sha2-nistp256/384/521) which are not cryptographically broken but have concerns about their standardization process

For detailed rationale and academic references for each algorithm classification, see ALGORITHM_GUIDANCE.md.

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This is originally based on https://github.com/evict/SSHScan