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Diffstat (limited to 'mac.c')
| -rw-r--r-- | mac.c | 265 |
1 files changed, 265 insertions, 0 deletions
@@ -0,0 +1,265 @@ +/* $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; +} |