OSPRH-28892: Harden Apache SSL config for PQC compliance

[mcgonago]

Summary

• Add !kRSA to SSLCipherSuite to block quantum-vulnerable RSA key exchange suites and remove MEDIUM-strength ciphers
• Switch SSLProtocol from blacklist (all -SSLv2 -SSLv3 -TLSv1) to whitelist (-all +TLSv1.3 +TLSv1.2), removing implicit TLS 1.1 support

These changes harden the Horizon Apache reverse proxy against the Harvest Now, Decrypt Later (HNDL) threat model by preventing negotiation of quantum-vulnerable cipher suites and legacy protocol versions.

Jira

• Related: OSPRH-28891 (SSLCipherSuite hardening)
• Closes: OSPRH-28892 (SSLProtocol hardening)
• Epic: OSPRH-27427 (Horizon PQC compliance)

Changes

templates/horizon/config/ssl.conf

Directive	Before	After
SSLCipherSuite	HIGH:MEDIUM:!aNULL:!MD5:!RC4:!3DES	HIGH:!aNULL:!MD5:!RC4:!3DES:!kRSA
SSLProtocol	all -SSLv2 -SSLv3 -TLSv1	-all +TLSv1.3 +TLSv1.2

Why these changes

• !kRSA: RSA key exchange is vulnerable to Shor's algorithm (quantum attack) and lacks forward secrecy. Blocking it ensures Apache only uses (EC)DHE-based key exchanges
• MEDIUM removed: Only HIGH-strength ciphers should be offered
• SSLProtocol whitelist: Explicit allowlist is safer than a denylist; TLS 1.1 was implicitly still allowed in the old config

Test plan

• go build ./... passes
• make test passes (36/36 functional specs, 75.4% coverage)
• Post-merge: verify TLS 1.3 negotiation with openssl s_client -connect <route>:443 -tls1_3
• Post-merge: verify kRSA blocked with openssl s_client -connect <route>:443 -cipher "AES256-SHA" (expect handshake failure)

Co-Authored-By: Claude Opus 4.6 noreply@anthropic.com

[openshift-ci]

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[openshift-ci-robot]

@mcgonago: This pull request references OSPRH-28892 which is a valid jira issue.

Warning: The referenced jira issue has an invalid target version for the target branch this PR targets: expected the story to target the "5.0.0" version, but no target version was set.

Details

In response to this:

Summary

• Add !kRSA to SSLCipherSuite to block quantum-vulnerable RSA key exchange suites and remove MEDIUM-strength ciphers
• Switch SSLProtocol from blacklist (all -SSLv2 -SSLv3 -TLSv1) to whitelist (-all +TLSv1.3 +TLSv1.2), removing implicit TLS 1.1 support

These changes harden the Horizon Apache reverse proxy against the Harvest Now, Decrypt Later (HNDL) threat model by preventing negotiation of quantum-vulnerable cipher suites and legacy protocol versions.

Jira

• Related: OSPRH-28891 (SSLCipherSuite hardening)
• Closes: OSPRH-28892 (SSLProtocol hardening)
• Epic: OSPRH-27427 (Horizon PQC compliance)

Changes

templates/horizon/config/ssl.conf

Directive	Before	After
SSLCipherSuite	HIGH:MEDIUM:!aNULL:!MD5:!RC4:!3DES	HIGH:!aNULL:!MD5:!RC4:!3DES:!kRSA
SSLProtocol	all -SSLv2 -SSLv3 -TLSv1	-all +TLSv1.3 +TLSv1.2

Why these changes

• !kRSA: RSA key exchange is vulnerable to Shor's algorithm (quantum attack) and lacks forward secrecy. Blocking it ensures Apache only uses (EC)DHE-based key exchanges
• MEDIUM removed: Only HIGH-strength ciphers should be offered
• SSLProtocol whitelist: Explicit allowlist is safer than a denylist; TLS 1.1 was implicitly still allowed in the old config

Test plan

• go build ./... passes
• make test passes (36/36 functional specs, 75.4% coverage)
• Post-merge: verify TLS 1.3 negotiation with openssl s_client -connect <route>:443 -tls1_3
• Post-merge: verify kRSA blocked with openssl s_client -connect <route>:443 -cipher "AES256-SHA" (expect handshake failure)

Co-Authored-By: Claude Opus 4.6 noreply@anthropic.com

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[openshift-ci]

PR needs rebase.

Details

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[mcgonago]

Related to ssl.conf centralized to lib-common (OSPRH-30239). PQC TLS defaults will most likely follow a change in lib-common PR-697. See OSPRH-28889 for details.