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fix(kms-keyring): validate content algorithm matches selected suite on decrypt - #527
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…crypt The KMS+Context and RSA-OAEP decrypt paths selected the content algorithm suite from the object's content metadata without checking it against the algorithm this data key was bound to. A mismatch (for example a GCM-sealed object whose content-algorithm metadata reads CBC) was accepted, so the object could be processed under a different suite than it was written with. KmsKeyring now rejects a stored aws:x-amz-cek-alg that does not match the selected suite before calling KMS Decrypt. RsaKeyring now accepts only GCM-family selected suites for the RSA-OAEP pseudo-data-key binding. Both preserve the GCM->CTR equivalence used by ranged gets.
RSA-OAEP data keys record AES/GCM/NoPadding for every non-committing suite, including CBC objects rewrapped by reEncryptInstructionFile, so the wrapped value cannot identify the content algorithm. Revert the RsaKeyring check and its tests; keep the KMS+Context check, where the stored aws:x-amz-cek-alg records the actual content algorithm.
kessplas
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kessplas
marked this pull request as ready for review
October 26, 2026 22:53
akareddy04
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Oct 27, 2026
Contributor
|
Fix looks right for |
Move the Kms+Context content algorithm check into KmsContentAlgorithm and call it from both KmsKeyring and KmsDiscoveryKeyring. Include the stored content algorithm and the selected suite in the error message.
Contributor
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LGTM |
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Nov 4, 2026
## [4.0.4](v4.0.3...v4.0.4) (2026-11-04) ### Fixes * **kms-keyring:** validate content algorithm matches selected suite on decrypt ([#527](#527)) ([96b1c2d](96b1c2d))
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Issue #, if available: n/a
Description of changes:
The KMS+Context and RSA-OAEP decrypt paths selected the content algorithm suite from the object's content metadata without checking it against the algorithm this data key was bound to.
KmsKeyring now rejects a stored aws:x-amz-cek-alg that does not match the selected suite before calling KMS Decrypt. RsaKeyring now accepts only GCM-family selected suites for the RSA-OAEP pseudo-data-key binding. Both preserve the GCM->CTR equivalence used by ranged gets.
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