Add relax-rsa-key-usage feature to restore historical RSA keyUsage #512
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johnhurt wants to merge 1 commit into
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Add relax-rsa-key-usage feature to restore historical RSA keyUsage #512johnhurt wants to merge 1 commit into
relax-rsa-key-usage feature to restore historical RSA keyUsage #512johnhurt wants to merge 1 commit into
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…default BoringSSL 5.x changed SSL_CONFIG::enforce_rsa_key_usage to default to true, making client-side RSA leaf keyUsage mismatches a fatal handshake error (KEY_USAGE_BIT_INCORRECT). Many real-world origins serve certificates whose keyUsage does not include the bit required by the negotiated cipher suite; OpenSSL and prior BoringSSL pins accepted them. This adds a new `relax-rsa-key-usage` Cargo feature that applies a build-time patch restoring the historical default (false). When the feature is not enabled, the BoringSSL 5.x strict behaviour is preserved. Non-RSA keyUsage enforcement is unaffected in either case.
cjpatton
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Jun 24, 2026
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Looks good. Can you update CI to make sure the patch is tested? Also consider adding a unit test with a cert that would validate with and without this feature.
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| # Restores the historical BoringSSL default of not enforcing RSA keyUsage | ||
| # during TLS handshakes. BoringSSL 5.x changed `enforce_rsa_key_usage` to |
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The version number refers to the boring crate, not BoringSSL, correct? It might be more helpful to refer to the value of BORINGSSL_API_VERSION in the BoringSSL repo itself (include/openssl/base.h).
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Likewise for the commit message for the new patch.
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Good call. I'll take care of both. |
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BoringSSL 5.x includes an update to openssl that changed SSL_CONFIG::enforce_rsa_key_usage to default to true, making client-side RSA leaf keyUsage mismatches a fatal handshake error (KEY_USAGE_BIT_INCORRECT). Many real-world origins serve certificates whose keyUsage does not include the bit required by the negotiated cipher suite; OpenSSL and prior BoringSSL pins accepted them.
This adds a new
relax-rsa-key-usageCargo feature that applies a build-time patch restoring the historical default (false). When the feature is not enabled, the BoringSSL 5.x strict behaviour is preserved. Non-RSA keyUsage enforcement is unaffected in either case.