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Refactor ssh_packet_hmac_verify to allow for direct buffer

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This will make it easier to do Encrypt-then-MAC checks as those will be
on the direct encrypted data received before decrypting which means they
are not allocated in an ssh buffer at that point yet.

Signed-off-by: Dirkjan Bussink <d.bussink@gmail.com>
Reviewed-by: Jon Simons <jon@jonsimons.org>
Reviewed-by: Jakub Jelen <jjelen@redhat.com>
This commit is contained in:
Dirkjan Bussink
2019-02-08 19:37:35 +00:00
committed by Andreas Schneider
parent f055319efe
commit c6608c9211
3 changed files with 13 additions and 10 deletions
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18
src/packet_crypt.c
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@@ -205,21 +205,23 @@ static int secure_memcmp(const void *s1, const void *s2, size_t n)
* @brief Verify the hmac of a packet
*
* @param session The session to use.
* @param buffer The buffer to verify the hmac from.
* @param data The pointer to the data to verify the hmac from.
* @param len The length of the given data.
* @param mac The mac to compare with the hmac.
*
* @return 0 if hmac and mac are equal, < 0 if not or an error
* occurred.
*/
int ssh_packet_hmac_verify(ssh_session session,
ssh_buffer buffer,
const void *data,
size_t len,
uint8_t *mac,
enum ssh_hmac_e type)
{
struct ssh_crypto_struct *crypto = NULL;
unsigned char hmacbuf[DIGEST_MAX_LEN] = {0};
HMACCTX ctx;
unsigned int len;
unsigned int hmaclen;
uint32_t seq;
/* AEAD types have no mac checking */
@@ -237,15 +239,15 @@ int ssh_packet_hmac_verify(ssh_session session,
seq = htonl(session->recv_seq);
hmac_update(ctx, (unsigned char *) &seq, sizeof(uint32_t));
hmac_update(ctx, ssh_buffer_get(buffer), ssh_buffer_get_len(buffer));
hmac_final(ctx, hmacbuf, &len);
hmac_update(ctx, data, len);
hmac_final(ctx, hmacbuf, &hmaclen);
#ifdef DEBUG_CRYPTO
ssh_print_hexa("received mac",mac,len);
ssh_print_hexa("Computed mac",hmacbuf,len);
ssh_print_hexa("received mac",mac,hmaclen);
ssh_print_hexa("Computed mac",hmacbuf,hmaclen);
ssh_print_hexa("seq",(unsigned char *)&seq,sizeof(uint32_t));
#endif
if (secure_memcmp(mac, hmacbuf, len) == 0) {
if (secure_memcmp(mac, hmacbuf, hmaclen) == 0) {
return 0;
}