pqcprobe

A small command-line TLS probing utility that uses pyOpenSSL to inspect an HTTPS server's TLS configuration, with a focus on post-quantum readiness.

Features:

• Reports negotiated TLS version, cipher, ALPN and certificate summary
• Reports the negotiated key-exchange group and flags whether it is post-quantum (e.g. X25519MLKEM768) or classical
• Assesses post-quantum posture: enumerates which key-exchange groups the server accepts and flags "harvest-now, decrypt-later" (HNDL) risk when no post-quantum key exchange is offered
• Verifies the certificate matches the requested hostname (SAN/CN, wildcard and IP aware)
• Probes server support for TLS 1.3 and TLS 1.2
• Samples which TLS 1.2 ciphers the server accepts (and attempts TLS 1.3 ciphersuites where supported by OpenSSL)
• Can fetch raw PEM for the server certificate (--raw-cert)
• Concurrency option for probing (--concurrency)
• Human-friendly summary (--pretty) or JSON output (--json)
• Meaningful exit codes for scripting (see below)

Requirements:

• Python 3.9.2+
• pyOpenSSL, cryptography (installed automatically)
• OpenSSL 3.x recommended (3.5+ for post-quantum group support). On macOS the system openssl is LibreSSL and cannot test the ML-KEM hybrid groups; install OpenSSL 3.5+ (e.g. via Homebrew) for full functionality.

Install

pip install pqcprobe

This installs a pqcprobe command. To run from a source checkout instead:

python3 -m venv .venv
source .venv/bin/activate
python3 -m pip install -e .

Usage

pqcprobe https://example.com --pretty
pqcprobe example.com:443 --json
pqcprobe example.com:443 --raw-cert

# Post-quantum audit: fail (exit 3) if the server offers no PQC key exchange
pqcprobe https://example.com --fail-on-classical-only
# Skip group probing entirely (e.g. when the openssl CLI is unavailable)
pqcprobe https://example.com --no-groups

(From a source checkout without installing, use python3 pqcprobe.py ....)

Post-quantum key-exchange probing:

• Enumerating group support forces individual groups via the native openssl CLI, since pyOpenSSL does not expose a way to set the group list. OpenSSL 3.5+ is required for the ML-KEM hybrid groups (X25519MLKEM768, etc.). Groups the local openssl doesn't recognize are reported as "not testable" rather than "unsupported" (relevant on macOS, whose system openssl is LibreSSL).
• Reading the negotiated group uses pyOpenSSL's Connection.get_group_name() and needs no external tools.

Exit codes:

• 0 success
• 1 handshake failed
• 2 certificate hostname mismatch (when verifying)
• 3 no post-quantum key exchange offered (only with --fail-on-classical-only)

Notes:

• Programmatic overriding of TLS 1.3 ciphersuites requires a recent OpenSSL + pyOpenSSL exposing set_ciphersuites.
• Cipher probing may produce handshake failures for many ciphers — the tool records successes and errors.
• Only use pqcprobe against systems you own or are authorized to test.

Contributing

Contributions are welcome — see CONTRIBUTING.md. Security issues should be reported privately per SECURITY.md.

License

MIT © Andre Van Klaveren