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From:   Ard Biesheuvel <ardb@kernel.org>
To:     linux-crypto@vger.kernel.org
Cc:     Ard Biesheuvel <ardb@kernel.org>,
        Eric Biggers <ebiggers@kernel.org>,
        Herbert Xu <herbert@gondor.apana.org.au>
Subject: [PATCH v2 4/4] crypto: aead - fix inaccurate documentation
Date:   Wed, 14 Dec 2022 18:19:57 +0100
Message-Id: <20221214171957.2833419-5-ardb@kernel.org>
In-Reply-To: <20221214171957.2833419-1-ardb@kernel.org>
References: <20221214171957.2833419-1-ardb@kernel.org>
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The AEAD documentation conflates associated data and authentication
tags: the former (along with the ciphertext) is authenticated by the
latter. Fix the doc accordingly.

Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
---
 include/crypto/aead.h | 20 ++++++++++----------
 1 file changed, 10 insertions(+), 10 deletions(-)

diff --git a/include/crypto/aead.h b/include/crypto/aead.h
index 14db3bee0519ee85..4a2b7e6e0c1fa7cd 100644
--- a/include/crypto/aead.h
+++ b/include/crypto/aead.h
@@ -27,15 +27,12 @@
  *
  * For example: authenc(hmac(sha256), cbc(aes))
  *
- * The example code provided for the symmetric key cipher operation
- * applies here as well. Naturally all *skcipher* symbols must be exchanged
- * the *aead* pendants discussed in the following. In addition, for the AEAD
- * operation, the aead_request_set_ad function must be used to set the
- * pointer to the associated data memory location before performing the
- * encryption or decryption operation. In case of an encryption, the associated
- * data memory is filled during the encryption operation. For decryption, the
- * associated data memory must contain data that is used to verify the integrity
- * of the decrypted data. Another deviation from the asynchronous block cipher
+ * The example code provided for the symmetric key cipher operation applies
+ * here as well. Naturally all *skcipher* symbols must be exchanged the *aead*
+ * pendants discussed in the following. In addition, for the AEAD operation,
+ * the aead_request_set_ad function must be used to set the pointer to the
+ * associated data memory location before performing the encryption or
+ * decryption operation. Another deviation from the asynchronous block cipher
  * operation is that the caller should explicitly check for -EBADMSG of the
  * crypto_aead_decrypt. That error indicates an authentication error, i.e.
  * a breach in the integrity of the message. In essence, that -EBADMSG error
@@ -49,7 +46,10 @@
  *
  * The destination scatterlist has the same layout, except that the plaintext
  * (resp. ciphertext) will grow (resp. shrink) by the authentication tag size
- * during encryption (resp. decryption).
+ * during encryption (resp. decryption). The authentication tag is generated
+ * during the encryption operation and appended to the ciphertext. During
+ * decryption, the authentication tag is consumed along with the ciphertext and
+ * used to verify the integrity of the plaintext and the associated data.
  *
  * In-place encryption/decryption is enabled by using the same scatterlist
  * pointer for both the source and destination.
-- 
2.35.1