Document and test Post-Quantum TLS with OpenSSL 3.5+ (X25519MLKEM768) #15625

France's ANSSI will stop certifying non-PQC products from 2027. The US Executive Order 14409 mandates PQC for all federal systems, with key establishment by 2030 and digital signatures by 2031. Australia's ASD/ACSC has published post-quantum vendor guidance urging organizations to assess PQC readiness across their supply chain.

Context

Redis delegates TLS to OpenSSL. When linked against OpenSSL 3.5+, hybrid post-quantum key exchange (X25519MLKEM768, FIPS 203) works automatically via OpenSSL's default group negotiation. However:

• There is no mainline documentation on PQC TLS configuration or verification
• No CI testing with OpenSSL 3.5 to confirm PQC key exchange negotiates correctly
• No guidance for operators needing to verify PQC compliance
• The tls-ciphers and tls-ciphersuites config options exist, but there is no tls-groups option to explicitly configure key exchange groups

Redis is widely deployed in government, finance, and healthcare, all sectors directly impacted by PQC mandates.

Proposal

1. Documentation: Add a PQC TLS section covering OpenSSL 3.5+ requirements, how to verify X25519MLKEM768 negotiation, and performance considerations
2. CI testing: Add an OpenSSL 3.5 build variant to CI verifying PQC key exchange works
3. Configuration: Consider adding a tls-groups config option for explicit control over TLS key exchange groups (similar to PostgreSQL 18's ssl_groups)

References

• NIST FIPS 203 (ML-KEM)
• US Executive Order 14409
• Australia ASD PQC Vendor Guidance