UPSTREAM PR #30945: Fix CRL issuer lookup for partial chains

[loci-dev]

Note

Source pull request: openssl/openssl#30945

Fixes #30932

When X509_V_FLAG_PARTIAL_CHAIN is used with X509_V_FLAG_CRL_CHECK_ALL, chain construction can stop at a trusted intermediate. In that case, checking the trusted intermediate's revocation status may require a CRL whose issuer certificate is available from the trust store but is not present in the constructed chain.

Previously, CRL issuer selection could accept the truncated chain anchor as the CRL issuer when the CRL had no AKID, because the adjacent-candidate path checked only the CRL AKID result. Since X509_check_akid(cert, NULL) succeeds, this could select a certificate whose subject did not match the CRL issuer name. CRL signature verification was then attempted with the wrong public key, producing the misleading error X509_V_ERR_CRL_SIGNATURE_FAILURE.

This change:

• requires candidate CRL issuer certificate subjects to match the CRL issuer name before accepting an AKID match
• for direct CRLs on the last certificate of a partial chain, looks up matching CRL issuer certificates through the configured certificate lookup method
• accepts a looked-up CRL issuer only if check_issued(x, candidate) holds and the candidate matches the CRL issuer name and AKID
• keeps looked-up CRL issuer certificates alive for the lifetime of the X509_STORE_CTX
• restricts the additional lookup to the partial-chain anchor case
• adds regression coverage for PARTIAL_CHAIN | CRL_CHECK | CRL_CHECK_ALL

Backport status:

• openssl-4.0: applies cleanly
• openssl-3.6: applies cleanly
• openssl-3.5: applies cleanly
• openssl-3.4: library changes apply cleanly. test/crltest.c needs a small manual conflict resolution due to test layout differences

[loci-review]

Base version:

Target version:

Base version dominated by lightweight X509_NAME_cmp (43 µs) and X509_check_akid (43 µs). Target version introduces expensive certificate operations: X509_add_cert (9.5 ms, 62%), X509_cmp (5.2 ms, 34%), X509_self_signed (4.3 ms, 28%), and ossl_x509v3_cache_extensions (2.6 ms, 17%), explaining the 35x slowdown.

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