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AES: Extend key wrap implementation to support longer data

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This extends the "XOR t" operation in aes_wrap() and aes_unwrap() to
handle up to four octets of the n*h+i value instead of just the least
significant octet. This allows the plaintext be longer than 336 octets
which was the previous limit.

Signed-off-by: Jouni Malinen <j@w1.fi>
This commit is contained in:
Jouni Malinen 2014-10-07 14:45:22 +03:00
parent eefec1e40b
commit a256506ddc
2 changed files with 12 additions and 2 deletions
Show stats Download patch file Download diff file Expand all files Collapse all files

7
src/crypto/aes-unwrap.c
View file

@ -29,6 +29,7 @@ int aes_unwrap(const u8 *kek, size_t kek_len, int n, const u8 *cipher,
u8 a[8], *r, b[AES_BLOCK_SIZE];
int i, j;
void *ctx;
unsigned int t;
/* 1) Initialize variables. */
os_memcpy(a, cipher, 8);
@ -50,7 +51,11 @@ int aes_unwrap(const u8 *kek, size_t kek_len, int n, const u8 *cipher,
r = plain + (n - 1) * 8;
for (i = n; i >= 1; i--) {
os_memcpy(b, a, 8);
b[7] ^= n * j + i;
t = n * j + i;
b[7] ^= t;
b[6] ^= t >> 8;
b[5] ^= t >> 16;
b[4] ^= t >> 24;
os_memcpy(b + 8, r, 8);
aes_decrypt(ctx, b, b);

7
src/crypto/aes-wrap.c
View file

@ -28,6 +28,7 @@ int aes_wrap(const u8 *kek, size_t kek_len, int n, const u8 *plain, u8 *cipher)
u8 *a, *r, b[AES_BLOCK_SIZE];
int i, j;
void *ctx;
unsigned int t;
a = cipher;
r = cipher + 8;
@ -54,7 +55,11 @@ int aes_wrap(const u8 *kek, size_t kek_len, int n, const u8 *plain, u8 *cipher)
os_memcpy(b + 8, r, 8);
aes_encrypt(ctx, b, b);
os_memcpy(a, b, 8);
a[7] ^= n * j + i;
t = n * j + i;
a[7] ^= t;
a[6] ^= t >> 8;
a[5] ^= t >> 16;
a[4] ^= t >> 24;
os_memcpy(r, b + 8, 8);
r += 8;
}