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mptcp: use HMAC-SHA256 library instead of open-coded HMAC 

Now that there are easy-to-use HMAC-SHA256 library functions, use these
in net/mptcp/crypto.c instead of open-coding the HMAC algorithm.

Remove the WARN_ON_ONCE() for messages longer than SHA256_DIGEST_SIZE.
The new implementation handles all message lengths correctly.

The mptcp-crypto KUnit test still passes after this change.

Signed-off-by: Eric Biggers <ebiggers@kernel.org>
Reviewed-by: Matthieu Baerts (NGI0) <matttbe@kernel.org>
Signed-off-by: Matthieu Baerts (NGI0) <matttbe@kernel.org>
Link: https://patch.msgid.link/20250902-net-next-mptcp-misc-feat-6-18-v2-1-fa02bb3188b1@kernel.org
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
This commit is contained in:
Eric Biggers 2025-09-02 23:11:33 +02:00 committed by Jakub Kicinski
parent 0e2a5208cc
commit 2d5be5629c
1 changed files with 2 additions and 33 deletions
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35
net/mptcp/crypto.c
View File

@ -22,7 +22,6 @@
#include <linux/kernel.h>
#include <crypto/sha2.h>
#include <linux/unaligned.h>
#include "protocol.h"
@ -43,39 +42,9 @@ void mptcp_crypto_key_sha(u64 key, u32 *token, u64 *idsn)
void mptcp_crypto_hmac_sha(u64 key1, u64 key2, u8 *msg, int len, void *hmac)
{
u8 input[SHA256_BLOCK_SIZE + SHA256_DIGEST_SIZE];
u8 key1be[8];
u8 key2be[8];
int i;
__be64 key[2] = { cpu_to_be64(key1), cpu_to_be64(key2) };
if (WARN_ON_ONCE(len > SHA256_DIGEST_SIZE))
len = SHA256_DIGEST_SIZE;
put_unaligned_be64(key1, key1be);
put_unaligned_be64(key2, key2be);
/* Generate key xored with ipad */
memset(input, 0x36, SHA256_BLOCK_SIZE);
for (i = 0; i < 8; i++)
input[i] ^= key1be[i];
for (i = 0; i < 8; i++)
input[i + 8] ^= key2be[i];
memcpy(&input[SHA256_BLOCK_SIZE], msg, len);
/* emit sha256(K1 || msg) on the second input block, so we can
* reuse 'input' for the last hashing
*/
sha256(input, SHA256_BLOCK_SIZE + len, &input[SHA256_BLOCK_SIZE]);
/* Prepare second part of hmac */
memset(input, 0x5C, SHA256_BLOCK_SIZE);
for (i = 0; i < 8; i++)
input[i] ^= key1be[i];
for (i = 0; i < 8; i++)
input[i + 8] ^= key2be[i];
sha256(input, SHA256_BLOCK_SIZE + SHA256_DIGEST_SIZE, hmac);
hmac_sha256_usingrawkey((const u8 *)key, sizeof(key), msg, len, hmac);
}
#if IS_MODULE(CONFIG_MPTCP_KUNIT_TEST)