/* $OpenBSD: mac.c,v 1.34 2017/05/08 22:57:38 djm Exp $ */
/*
* Copyright (c) 2001 Markus Friedl. All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
*
* THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
* IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
* OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
* IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
* NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
* DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
* THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
* THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/
#include "includes.h"
#include <sys/types.h>
#include <string.h>
#include <stdio.h>
#include "digest.h"
#include "hmac.h"
#include "umac.h"
#include "mac.h"
#include "misc.h"
#include "ssherr.h"
#include "sshbuf.h"
#include "openbsd-compat/openssl-compat.h"
#define SSH_DIGEST 1 /* SSH_DIGEST_XXX */
#define SSH_UMAC 2 /* UMAC (not integrated with OpenSSL) */
#define SSH_UMAC128 3
struct macalg {
char *name;
int type;
int alg;
int truncatebits; /* truncate digest if != 0 */
int key_len; /* just for UMAC */
int len; /* just for UMAC */
int etm; /* Encrypt-then-MAC */
};
static const struct macalg macs[] = {
/* Encrypt-and-MAC (encrypt-and-authenticate) variants */
{ "hmac-sha1", SSH_DIGEST, SSH_DIGEST_SHA1, 0, 0, 0, 0 },
{ "hmac-sha1-96", SSH_DIGEST, SSH_DIGEST_SHA1, 96, 0, 0, 0 },
#ifdef HAVE_EVP_SHA256
{ "hmac-sha2-256", SSH_DIGEST, SSH_DIGEST_SHA256, 0, 0, 0, 0 },
{ "hmac-sha2-512", SSH_DIGEST, SSH_DIGEST_SHA512, 0, 0, 0, 0 },
#endif
{ "hmac-md5", SSH_DIGEST, SSH_DIGEST_MD5, 0, 0, 0, 0 },
{ "hmac-md5-96", SSH_DIGEST, SSH_DIGEST_MD5, 96, 0, 0, 0 },
{ "umac-64@openssh.com", SSH_UMAC, 0, 0, 128, 64, 0 },
{ "umac-128@openssh.com", SSH_UMAC128, 0, 0, 128, 128, 0 },
/* Encrypt-then-MAC variants */
{ "hmac-sha1-etm@openssh.com", SSH_DIGEST, SSH_DIGEST_SHA1, 0, 0, 0, 1 },
{ "hmac-sha1-96-etm@openssh.com", SSH_DIGEST, SSH_DIGEST_SHA1, 96, 0, 0, 1 },
#ifdef HAVE_EVP_SHA256
{ "hmac-sha2-256-etm@openssh.com", SSH_DIGEST, SSH_DIGEST_SHA256, 0, 0, 0, 1 },
{ "hmac-sha2-512-etm@openssh.com", SSH_DIGEST, SSH_DIGEST_SHA512, 0, 0, 0, 1 },
#endif
{ "hmac-md5-etm@openssh.com", SSH_DIGEST, SSH_DIGEST_MD5, 0, 0, 0, 1 },
{ "hmac-md5-96-etm@openssh.com", SSH_DIGEST, SSH_DIGEST_MD5, 96, 0, 0, 1 },
{ "umac-64-etm@openssh.com", SSH_UMAC, 0, 0, 128, 64, 1 },
{ "umac-128-etm@openssh.com", SSH_UMAC128, 0, 0, 128, 128, 1 },
{ NULL, 0, 0, 0, 0, 0, 0 }
};
/* Returns a list of supported MACs separated by the specified char. */
char *
mac_alg_list(char sep)
{
char *ret = NULL, *tmp;
size_t nlen, rlen = 0;
const struct macalg *m;
for (m = macs; m->name != NULL; m++) {
if (ret != NULL)
ret[rlen++] = sep;
nlen = strlen(m->name);
if ((tmp = realloc(ret, rlen + nlen + 2)) == NULL) {
free(ret);
return NULL;
}
ret = tmp;
memcpy(ret + rlen, m->name, nlen + 1);
rlen += nlen;
}
return ret;
}
static int
mac_setup_by_alg(struct sshmac *mac, const struct macalg *macalg)
{
mac->type = macalg->type;
if (mac->type == SSH_DIGEST) {
if ((mac->hmac_ctx = ssh_hmac_start(macalg->alg)) == NULL)
return SSH_ERR_ALLOC_FAIL;
mac->key_len = mac->mac_len = ssh_hmac_bytes(macalg->alg);
} else {
mac->mac_len = macalg->len / 8;
mac->key_len = macalg->key_len / 8;
mac->umac_ctx = NULL;
}
if (macalg->truncatebits != 0)
mac->mac_len = macalg->truncatebits / 8;
mac->etm = macalg->etm;
return 0;
}
int
mac_setup(struct sshmac *mac, char *name)
{
const struct macalg *m;
for (m = macs; m->name != NULL; m++) {
if (strcmp(name, m->name) != 0)
continue;
if (mac != NULL)
return mac_setup_by_alg(mac, m);
return 0;
}
return SSH_ERR_INVALID_ARGUMENT;
}
int
mac_init(struct sshmac *mac)
{
if (mac->key == NULL)
return SSH_ERR_INVALID_ARGUMENT;
switch (mac->type) {
case SSH_DIGEST:
if (mac->hmac_ctx == NULL ||
ssh_hmac_init(mac->hmac_ctx, mac->key, mac->key_len) < 0)
return SSH_ERR_INVALID_ARGUMENT;
return 0;
case SSH_UMAC:
if ((mac->umac_ctx = umac_new(mac->key)) == NULL)
return SSH_ERR_ALLOC_FAIL;
return 0;
case SSH_UMAC128:
if ((mac->umac_ctx = umac128_new(mac->key)) == NULL)
return SSH_ERR_ALLOC_FAIL;
return 0;
default:
return SSH_ERR_INVALID_ARGUMENT;
}
}
int
mac_compute(struct sshmac *mac, u_int32_t seqno,
const u_char *data, int datalen,
u_char *digest, size_t dlen)
{
static union {
u_char m[SSH_DIGEST_MAX_LENGTH];
u_int64_t for_align;
} u;
u_char b[4];
u_char nonce[8];
if (mac->mac_len > sizeof(u))
return SSH_ERR_INTERNAL_ERROR;
switch (mac->type) {
case SSH_DIGEST:
put_u32(b, seqno);
/* reset HMAC context */
if (ssh_hmac_init(mac->hmac_ctx, NULL, 0) < 0 ||
ssh_hmac_update(mac->hmac_ctx, b, sizeof(b)) < 0 ||
ssh_hmac_update(mac->hmac_ctx, data, datalen) < 0 ||
ssh_hmac_final(mac->hmac_ctx, u.m, sizeof(u.m)) < 0)
return SSH_ERR_LIBCRYPTO_ERROR;
break;
case SSH_UMAC:
POKE_U64(nonce, seqno);
umac_update(mac->umac_ctx, data, datalen);
umac_final(mac->umac_ctx, u.m, nonce);
break;
case SSH_UMAC128:
put_u64(nonce, seqno);
umac128_update(mac->umac_ctx, data, datalen);
umac128_final(mac->umac_ctx, u.m, nonce);
break;
default:
return SSH_ERR_INVALID_ARGUMENT;
}
if (digest != NULL) {
if (dlen > mac->mac_len)
dlen = mac->mac_len;
memcpy(digest, u.m, dlen);
}
return 0;
}
int
mac_check(struct sshmac *mac, u_int32_t seqno,
const u_char *data, size_t dlen,
const u_char *theirmac, size_t mlen)
{
u_char ourmac[SSH_DIGEST_MAX_LENGTH];
int r;
if (mac->mac_len > mlen)
return SSH_ERR_INVALID_ARGUMENT;
if ((r = mac_compute(mac, seqno, data, dlen,
ourmac, sizeof(ourmac))) != 0)
return r;
if (timingsafe_bcmp(ourmac, theirmac, mac->mac_len) != 0)
return SSH_ERR_MAC_INVALID;
return 0;
}
void
mac_clear(struct sshmac *mac)
{
if (mac->type == SSH_UMAC) {
if (mac->umac_ctx != NULL)
umac_delete(mac->umac_ctx);
} else if (mac->type == SSH_UMAC128) {
if (mac->umac_ctx != NULL)
umac128_delete(mac->umac_ctx);
} else if (mac->hmac_ctx != NULL)
ssh_hmac_free(mac->hmac_ctx);
mac->hmac_ctx = NULL;
mac->umac_ctx = NULL;
}
/* XXX copied from ciphers_valid */
#define MAC_SEP ","
int
mac_valid(const char *names)
{
char *maclist, *cp, *p;
if (names == NULL || strcmp(names, "") == 0)
return 0;
if ((maclist = cp = strdup(names)) == NULL)
return 0;
for ((p = strsep(&cp, MAC_SEP)); p && *p != '\0';
(p = strsep(&cp, MAC_SEP))) {
if (mac_setup(NULL, p) < 0) {
free(maclist);
return 0;
}
}
free(maclist);
return 1;
}
