|author||Eric Biggers <firstname.lastname@example.org>||2020-03-04 14:44:05 -0800|
|committer||Herbert Xu <email@example.com>||2020-03-12 23:00:13 +1100|
|parent||crypto: testmgr - do comparison tests before inauthentic input tests (diff)|
crypto: aead - improve documentation for scatterlist layout
Properly document the scatterlist layout for AEAD ciphers. Reported-by: Gilad Ben-Yossef <firstname.lastname@example.org> Cc: Stephan Mueller <email@example.com> Signed-off-by: Eric Biggers <firstname.lastname@example.org> Signed-off-by: Herbert Xu <email@example.com>
Diffstat (limited to 'include/crypto')
1 files changed, 27 insertions, 21 deletions
diff --git a/include/crypto/aead.h b/include/crypto/aead.h
index 1b3ebe8593c0..62c68550aab6 100644
@@ -43,27 +43,33 @@
* Memory Structure:
- * To support the needs of the most prominent user of AEAD ciphers, namely
- * IPSEC, the AEAD ciphers have a special memory layout the caller must adhere
- * to.
- * The scatter list pointing to the input data must contain:
- * * for RFC4106 ciphers, the concatenation of
- * associated authentication data || IV || plaintext or ciphertext. Note, the
- * same IV (buffer) is also set with the aead_request_set_crypt call. Note,
- * the API call of aead_request_set_ad must provide the length of the AAD and
- * the IV. The API call of aead_request_set_crypt only points to the size of
- * the input plaintext or ciphertext.
- * * for "normal" AEAD ciphers, the concatenation of
- * associated authentication data || plaintext or ciphertext.
- * It is important to note that if multiple scatter gather list entries form
- * the input data mentioned above, the first entry must not point to a NULL
- * buffer. If there is any potential where the AAD buffer can be NULL, the
- * calling code must contain a precaution to ensure that this does not result
- * in the first scatter gather list entry pointing to a NULL buffer.
+ * The source scatterlist must contain the concatenation of
+ * associated data || plaintext or ciphertext.
+ * 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).
+ * In-place encryption/decryption is enabled by using the same scatterlist
+ * pointer for both the source and destination.
+ * Even in the out-of-place case, space must be reserved in the destination for
+ * the associated data, even though it won't be written to. This makes the
+ * in-place and out-of-place cases more consistent. It is permissible for the
+ * "destination" associated data to alias the "source" associated data.
+ * As with the other scatterlist crypto APIs, zero-length scatterlist elements
+ * are not allowed in the used part of the scatterlist. Thus, if there is no
+ * associated data, the first element must point to the plaintext/ciphertext.
+ * To meet the needs of IPsec, a special quirk applies to rfc4106, rfc4309,
+ * rfc4543, and rfc7539esp ciphers. For these ciphers, the final 'ivsize' bytes
+ * of the associated data buffer must contain a second copy of the IV. This is
+ * in addition to the copy passed to aead_request_set_crypt(). These two IV
+ * copies must not differ; different implementations of the same algorithm may
+ * behave differently in that case. Note that the algorithm might not actually
+ * treat the IV as associated data; nevertheless the length passed to
+ * aead_request_set_ad() must include it.