From e08cbb29d8374118d1e5d3f1666d038b4bc86369 Mon Sep 17 00:00:00 2001 From: Dirkjan Bussink Date: Fri, 8 Feb 2019 19:37:35 +0000 Subject: [PATCH 3/6] Refactor ssh_packet_hmac_verify to allow for direct buffer 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. Reviewed-by: Jon Simons --- include/libssh/packet.h | 2 +- src/packet.c | 3 ++- src/packet_crypt.c | 18 ++++++++++-------- 3 files changed, 13 insertions(+), 10 deletions(-) diff --git a/include/libssh/packet.h b/include/libssh/packet.h index 2328cc5b..8fc7ce42 100644 --- a/include/libssh/packet.h +++ b/include/libssh/packet.h @@ -81,7 +81,7 @@ int ssh_packet_decrypt(ssh_session session, uint8_t *destination, uint8_t *sourc unsigned char *ssh_packet_encrypt(ssh_session session, void *packet, unsigned int len); -int ssh_packet_hmac_verify(ssh_session session,ssh_buffer buffer, +int ssh_packet_hmac_verify(ssh_session session, const void *data, size_t len, unsigned char *mac, enum ssh_hmac_e type); int ssh_packet_set_newkeys(ssh_session session, enum ssh_crypto_direction_e direction); diff --git a/src/packet.c b/src/packet.c index 1181ca7d..d0c5d60b 100644 --- a/src/packet.c +++ b/src/packet.c @@ -1186,7 +1186,8 @@ int ssh_packet_socket_callback(const void *data, size_t receivedlen, void *user) mac = packet_second_block + packet_remaining; rc = ssh_packet_hmac_verify(session, - session->in_buffer, + ssh_buffer_get(session->in_buffer), + ssh_buffer_get_len(session->in_buffer), mac, crypto->in_hmac); if (rc < 0) { diff --git a/src/packet_crypt.c b/src/packet_crypt.c index 59a6dcc5..d146c634 100644 --- a/src/packet_crypt.c +++ b/src/packet_crypt.c @@ -204,21 +204,23 @@ 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 buffer to verify the hmac from. + * @param len The length of the given buffer. * @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 */ @@ -236,15 +238,15 @@ 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; } -- 2.11.0