Reject zero-length AEAD authentication tags (GH #1364) - #1365
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GCM, EAX, CCM, ChaCha20-Poly1305, and XChaCha20-Poly1305 accepted zero-length authentication tags through EncryptAndAuthenticate, DecryptAndVerify, and the authenticated filters. Verification with a zero-length tag could report tampered ciphertext as authentic. Reject a zero tag size in AuthenticatedSymmetricCipherBase::TruncatedFinal, which all five algorithms and both filter paths reach during finalisation.
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Fixes #1364.
GCM, EAX, CCM, ChaCha20-Poly1305, and XChaCha20-Poly1305 accepted zero-length authentication tags through the one-shot APIs and authenticated filters.
EncryptAndAuthenticateproduced no tag, andDecryptAndVerifycould report tampered ciphertext as authentic. Reject a zero tag size inAuthenticatedSymmetricCipherBase::TruncatedFinal, which every affected path reaches during finalisation.The one-shot APIs process the message before finalisation, so output buffers may already contain data when the exception is thrown. Callers must discard that output.
The reporter's reproducer finds both affected cases before this change and none after it. Valid-tag controls still pass.