Edit
IABSD.fr/src/usr.bin/ssh/mac.c
djm
- usr.bin/ssh/mac.c
-
/* $OpenBSD: mac.c,v 1.39 2026/05/13 05:58:58 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 <sys/types.h> #include <stdio.h> #include <stdlib.h> #include <string.h> #include "digest.h" #include "hmac.h" #include "umac.h" #include "mac.h" #include "misc.h" #include "ssherr.h" #include "sshbuf.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 }, { "hmac-sha2-256", SSH_DIGEST, SSH_DIGEST_SHA256, 0, 0, 0, 0 }, { "hmac-sha2-512", SSH_DIGEST, SSH_DIGEST_SHA512, 0, 0, 0, 0 }, { "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 }, { "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 }, { "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; const struct macalg *m; char sep_str[2] = {sep, '\0'}; for (m = macs; m->name != NULL; m++) xextendf(&ret, sep_str, "%s", m->name); 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, uint32_t seqno, const u_char *data, int datalen, u_char *digest, size_t dlen) { static union { u_char m[SSH_DIGEST_MAX_LENGTH]; uint64_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, uint32_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; int found = 0; 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; } else found = 1; } free(maclist); return found; }