From 30243ad73957a2e1cc4aedc3f23be66cdf399f00 Mon Sep 17 00:00:00 2001 From: Michael Brown Date: Fri, 28 Oct 2022 16:27:10 +0100 Subject: [crypto] Add concept of cipher alignment size The GCM cipher mode of operation (in common with other counter-based modes of operation) has a notion of blocksize that does not neatly fall into our current abstraction: it does operate in 16-byte blocks but allows for an arbitrary overall data length (i.e. the final block may be incomplete). Model this by adding a concept of alignment size. Each call to encrypt() or decrypt() must begin at a multiple of the alignment size from the start of the data stream. This allows us to model GCM by using a block size of 1 byte and an alignment size of 16 bytes. As a side benefit, this same concept allows us to neatly model the fact that raw AES can encrypt only a single 16-byte block, by specifying an alignment size of zero on this cipher. Signed-off-by: Michael Brown --- src/crypto/aes.c | 1 + src/crypto/arc4.c | 1 + src/crypto/crypto_null.c | 1 + 3 files changed, 3 insertions(+) (limited to 'src/crypto') diff --git a/src/crypto/aes.c b/src/crypto/aes.c index aeeaa1d2c..5200e7760 100644 --- a/src/crypto/aes.c +++ b/src/crypto/aes.c @@ -784,6 +784,7 @@ struct cipher_algorithm aes_algorithm = { .name = "aes", .ctxsize = sizeof ( struct aes_context ), .blocksize = AES_BLOCKSIZE, + .alignsize = 0, .authsize = 0, .setkey = aes_setkey, .setiv = cipher_null_setiv, diff --git a/src/crypto/arc4.c b/src/crypto/arc4.c index 4d98abead..3b6adec19 100644 --- a/src/crypto/arc4.c +++ b/src/crypto/arc4.c @@ -119,6 +119,7 @@ struct cipher_algorithm arc4_algorithm = { .name = "ARC4", .ctxsize = ARC4_CTX_SIZE, .blocksize = 1, + .alignsize = 1, .authsize = 0, .setkey = arc4_setkey, .setiv = cipher_null_setiv, diff --git a/src/crypto/crypto_null.c b/src/crypto/crypto_null.c index 26cfbfc4e..0ad463c3e 100644 --- a/src/crypto/crypto_null.c +++ b/src/crypto/crypto_null.c @@ -84,6 +84,7 @@ struct cipher_algorithm cipher_null = { .name = "null", .ctxsize = 0, .blocksize = 1, + .alignsize = 1, .authsize = 0, .setkey = cipher_null_setkey, .setiv = cipher_null_setiv, -- cgit v1.2.3-55-g7522