[FIPS - Cherry-pick] Support allowing specific unknown critical extensions (#2377) #2473
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As of today, AWS-LC returns an error as part of verification if there are any critical extensions present in the certificate being validated. There have been asks to set a custom OID on the issued certificates to ensure that additional validation is performed by customers after or during the handshake. The intention is to prevent accidental mis-use of these certificates without that extra validation. To support this, we've decided to add two new APIs for this use case. 1. `X509_STORE_CTX_add_custom_crit_oid` adds an oid as an `ASN1_OBJECT` to the list of "known" critical extension OIDs in `ctx`. Typical OpenSSL/AWS-LC behavior returns an error if there are any unknown critical extensions present within the certificates being validated. This function lets users specify custom OIDs of any critical extensions that are within the certificates being validated, that they wish to allow. The callback mechanism enabled with `X509_STORE_CTX_set_verify_crit_oids` must be set for this feature to enabled. 2. `X509_STORE_CTX_set_verify_crit_oids` enables the `X509_STORE_CTX_verify_crit_oids_cb` with `X509_STORE_CTX`. Consumers should be performing additional validation against the custom extension oids after or during the handshake. This callback forces users to validate their custom OIDs when processing unknown custom critical extensions. The `X509_STORE_CTX_verify_crit_oids_cb` callback function gives the user the current certificate being validated as `x509` and a stack of `ASN1_OBJECT`s representing unknown critical extension OIDs that were found in `x509` and match those previously registered via`|X509_STORE_CTX_add_custom_crit_oid` as `oids`. This should not effect any existing consumers of `X509_verify_cert`. Any existence of an unknown critical extension will still cause the entire verification to be aborted. Only consumers that have enabled the callback and set specific OIDs with `ASN1_OBJECT` can circumvent the check and trigger the verification to pass. ### Testing: Test certs were generated by the team asking for this feature. By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license and the ISC license.
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Additional details and impacted files@@ Coverage Diff @@
## fips-2024-09-27 #2473 +/- ##
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+ Coverage 78.59% 78.61% +0.02%
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Files 585 585
Lines 100608 100723 +115
Branches 14263 14271 +8
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+ Hits 79070 79188 +118
+ Misses 20903 20898 -5
- Partials 635 637 +2 ☔ View full report in Codecov by Sentry. 🚀 New features to boost your workflow:
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darylmartin100
approved these changes
Jun 9, 2025
samuel40791765
approved these changes
Jun 10, 2025
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This change is outside of the FIPS module and does not affect its hash.
Commit was cherry-picked from mainline PR #2377. Original description is below.
As of today, AWS-LC returns an error as part of verification if there are any critical extensions present in the certificate being validated. There have been asks to set a custom OID on the issued certificates to ensure that additional validation is performed by customers after or during the handshake. The intention is to prevent accidental mis-use of these certificates without that extra validation.
To support this, we've decided to add two new APIs for this use case.
X509_STORE_CTX_add_custom_crit_oidadds an oid as anASN1_OBJECTto the list of "known" critical extension OIDs inctx. Typical OpenSSL/AWS-LC behavior returns an error if there are any unknown critical extensions present within the certificates being validated. This function lets users specify custom OIDs of any critical extensions that are within the certificates being validated, that they wish to allow. The callback mechanism enabled withX509_STORE_CTX_set_verify_crit_oidsmust be set for this feature to enabled.X509_STORE_CTX_set_verify_crit_oidsenables theX509_STORE_CTX_verify_crit_oids_cbwithX509_STORE_CTX. Consumers should be performing additional validation against the custom extension oids after or during the handshake. This callback forces users to validate their custom OIDs when processing unknown custom critical extensions. TheX509_STORE_CTX_verify_crit_oids_cbcallback function gives the user the current certificate being validated asx509and a stack ofASN1_OBJECTs representing unknown critical extension OIDs that were found inx509and match those previously registered via|X509_STORE_CTX_add_custom_crit_oidasoids.This should not effect any existing consumers of
X509_verify_cert. Any existence of an unknown critical extension will still cause the entire verification to be aborted. Only consumers that have enabled the callback and set specific OIDs withASN1_OBJECTcan circumvent the check and trigger the verification to pass.Testing:
Test certs were generated by the team asking for this feature.
By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license and the ISC license.