Tolerate missing CRLs - #642
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Post-handshake CRL verification used X509_V_FLAG_CRL_CHECK_ALL alone, which makes OpenSSL require a CRL for every certificate in the peer's chain. Publishing a CRL is optional for a CA, so this rejected common deployments, most notably an offline root CA that never publishes one and intermediate certificates carrying no CRL distribution point at all. Such a chain failed with "unable to get certificate CRL" as soon as a single CRL was downloaded, while a chain with no CRLs at all was accepted. Keep checking the whole chain, but add a verification callback that reports a certificate with no CRL available as unchecked instead of failing the verification. Revocation is still enforced for every certificate a CRL was obtained for. A peer certificate left unchecked is warned about, a CA certificate is only logged verbosely, since publishing a CRL is optional for a CA and such a warning would repeat on every handshake. The MbedTLS backend already behaved this way, so both backends now agree. Refs #604
michalvasko
approved these changes
Sep 21, 2026
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Refs #604 (comment)