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At the EVP level, for AEADs EVP_Cipher(ctx, out, NULL, 0) performs finalization. For consistency across AEADs (GCM, etc.), on decrypt it must check the tag. OCB and ChaCha20-Poly1305 took an early exit on the empty message (with or without AAD) and returned success without checking, so a forged tag (with or without AAD) was accepted before this change. Follow-up to openssl#31555 Assisted-by: Claude:claude-opus-4-8
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The SIV change is mostly unrelated, but I rolled it in since I was mucking with that test anyway. Hope it's OK. |
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minor nit, changes looks good!
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Merged to master. Thank you Billy! |
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At the EVP level, for AEADs EVP_Cipher(ctx, out, NULL, 0) performs finalization. For consistency across AEADs (GCM, etc.), on decrypt it must check the tag. OCB and ChaCha20-Poly1305 took an early exit on the empty message (with or without AAD) and returned success without checking, so a forged tag (with or without AAD) was accepted before this change. Follow-up to #31555 Assisted-by: Claude:claude-opus-4-8 Reviewed-by: Frederik Wedel-Heinen <[email protected]> Reviewed-by: Dmitry Belyavskiy <[email protected]> MergeDate: Fri Aug 7 13:34:35 2026 (Merged from #32173)
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Invalid tags can be accepted for empty ChaCha20-Poly1305 and OCB ciphertexts via EVP_Cipher()
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At the EVP level, for AEADs EVP_Cipher(ctx, out, NULL, 0) performs finalization. For consistency across AEADs (GCM, etc.), on decrypt it must check the tag. OCB and ChaCha20-Poly1305 took an early exit on the empty message (with or without AAD) and returned success without checking, so a forged tag (with or without AAD) was accepted before this change. Follow-up to openssl#31555 Assisted-by: Claude:claude-opus-4-8 Reviewed-by: Frederik Wedel-Heinen <[email protected]> Reviewed-by: Dmitry Belyavskiy <[email protected]> MergeDate: Fri Aug 7 13:34:35 2026 (Merged from openssl#32173)
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At the EVP level, for AEADs
EVP_Cipher(ctx, out, NULL, 0)performs finalization. For consistency across AEADs (GCM, etc.), on decrypt it must check the tag. OCB and ChaCha20-Poly1305 took an early exit on the empty message (with or without AAD) and returned success without checking, so a forged tag (with or without AAD) was accepted before this change.Follow-up to #31555
Assisted-by: Claude:claude-opus-4-8
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