1 /* $NetBSD: ssh-dss.c,v 1.7 2015/04/03 23:58:19 christos Exp $ */ 2 /* $OpenBSD: ssh-dss.c,v 1.32 2014/06/24 01:13:21 djm Exp $ */ 3 /* 4 * Copyright (c) 2000 Markus Friedl. All rights reserved. 5 * 6 * Redistribution and use in source and binary forms, with or without 7 * modification, are permitted provided that the following conditions 8 * are met: 9 * 1. Redistributions of source code must retain the above copyright 10 * notice, this list of conditions and the following disclaimer. 11 * 2. Redistributions in binary form must reproduce the above copyright 12 * notice, this list of conditions and the following disclaimer in the 13 * documentation and/or other materials provided with the distribution. 14 * 15 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR 16 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES 17 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. 18 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, 19 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT 20 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, 21 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY 22 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT 23 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF 24 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 25 */ 26 27 #include "includes.h" 28 __RCSID("$NetBSD: ssh-dss.c,v 1.7 2015/04/03 23:58:19 christos Exp $"); 29 #include <sys/types.h> 30 31 #include <openssl/bn.h> 32 #include <openssl/evp.h> 33 34 #include <string.h> 35 36 #include "sshbuf.h" 37 #include "compat.h" 38 #include "ssherr.h" 39 #include "digest.h" 40 #define SSHKEY_INTERNAL 41 #include "sshkey.h" 42 43 #define INTBLOB_LEN 20 44 #define SIGBLOB_LEN (2*INTBLOB_LEN) 45 46 int 47 ssh_dss_sign(const struct sshkey *key, u_char **sigp, size_t *lenp, 48 const u_char *data, size_t datalen, u_int compat) 49 { 50 DSA_SIG *sig = NULL; 51 u_char digest[SSH_DIGEST_MAX_LENGTH], sigblob[SIGBLOB_LEN]; 52 size_t rlen, slen, len, dlen = ssh_digest_bytes(SSH_DIGEST_SHA1); 53 struct sshbuf *b = NULL; 54 int ret = SSH_ERR_INVALID_ARGUMENT; 55 56 if (lenp != NULL) 57 *lenp = 0; 58 if (sigp != NULL) 59 *sigp = NULL; 60 61 if (key == NULL || key->dsa == NULL || 62 sshkey_type_plain(key->type) != KEY_DSA) 63 return SSH_ERR_INVALID_ARGUMENT; 64 if (dlen == 0) 65 return SSH_ERR_INTERNAL_ERROR; 66 67 if ((ret = ssh_digest_memory(SSH_DIGEST_SHA1, data, datalen, 68 digest, sizeof(digest))) != 0) 69 goto out; 70 71 if ((sig = DSA_do_sign(digest, dlen, key->dsa)) == NULL) { 72 ret = SSH_ERR_LIBCRYPTO_ERROR; 73 goto out; 74 } 75 76 rlen = BN_num_bytes(sig->r); 77 slen = BN_num_bytes(sig->s); 78 if (rlen > INTBLOB_LEN || slen > INTBLOB_LEN) { 79 ret = SSH_ERR_INTERNAL_ERROR; 80 goto out; 81 } 82 explicit_bzero(sigblob, SIGBLOB_LEN); 83 BN_bn2bin(sig->r, sigblob + SIGBLOB_LEN - INTBLOB_LEN - rlen); 84 BN_bn2bin(sig->s, sigblob + SIGBLOB_LEN - slen); 85 86 if (compat & SSH_BUG_SIGBLOB) { 87 if (sigp != NULL) { 88 if ((*sigp = malloc(SIGBLOB_LEN)) == NULL) { 89 ret = SSH_ERR_ALLOC_FAIL; 90 goto out; 91 } 92 memcpy(*sigp, sigblob, SIGBLOB_LEN); 93 } 94 if (lenp != NULL) 95 *lenp = SIGBLOB_LEN; 96 ret = 0; 97 } else { 98 /* ietf-drafts */ 99 if ((b = sshbuf_new()) == NULL) { 100 ret = SSH_ERR_ALLOC_FAIL; 101 goto out; 102 } 103 if ((ret = sshbuf_put_cstring(b, "ssh-dss")) != 0 || 104 (ret = sshbuf_put_string(b, sigblob, SIGBLOB_LEN)) != 0) 105 goto out; 106 len = sshbuf_len(b); 107 if (sigp != NULL) { 108 if ((*sigp = malloc(len)) == NULL) { 109 ret = SSH_ERR_ALLOC_FAIL; 110 goto out; 111 } 112 memcpy(*sigp, sshbuf_ptr(b), len); 113 } 114 if (lenp != NULL) 115 *lenp = len; 116 ret = 0; 117 } 118 out: 119 explicit_bzero(digest, sizeof(digest)); 120 if (sig != NULL) 121 DSA_SIG_free(sig); 122 if (b != NULL) 123 sshbuf_free(b); 124 return ret; 125 } 126 127 int 128 ssh_dss_verify(const struct sshkey *key, 129 const u_char *signature, size_t signaturelen, 130 const u_char *data, size_t datalen, u_int compat) 131 { 132 DSA_SIG *sig = NULL; 133 u_char digest[SSH_DIGEST_MAX_LENGTH], *sigblob = NULL; 134 size_t len, dlen = ssh_digest_bytes(SSH_DIGEST_SHA1); 135 int ret = SSH_ERR_INTERNAL_ERROR; 136 struct sshbuf *b = NULL; 137 char *ktype = NULL; 138 139 if (key == NULL || key->dsa == NULL || 140 sshkey_type_plain(key->type) != KEY_DSA) 141 return SSH_ERR_INVALID_ARGUMENT; 142 if (dlen == 0) 143 return SSH_ERR_INTERNAL_ERROR; 144 145 /* fetch signature */ 146 if (compat & SSH_BUG_SIGBLOB) { 147 if ((sigblob = malloc(signaturelen)) == NULL) 148 return SSH_ERR_ALLOC_FAIL; 149 memcpy(sigblob, signature, signaturelen); 150 len = signaturelen; 151 } else { 152 /* ietf-drafts */ 153 if ((b = sshbuf_from(signature, signaturelen)) == NULL) 154 return SSH_ERR_ALLOC_FAIL; 155 if (sshbuf_get_cstring(b, &ktype, NULL) != 0 || 156 sshbuf_get_string(b, &sigblob, &len) != 0) { 157 ret = SSH_ERR_INVALID_FORMAT; 158 goto out; 159 } 160 if (strcmp("ssh-dss", ktype) != 0) { 161 ret = SSH_ERR_KEY_TYPE_MISMATCH; 162 goto out; 163 } 164 if (sshbuf_len(b) != 0) { 165 ret = SSH_ERR_UNEXPECTED_TRAILING_DATA; 166 goto out; 167 } 168 } 169 170 if (len != SIGBLOB_LEN) { 171 ret = SSH_ERR_INVALID_FORMAT; 172 goto out; 173 } 174 175 /* parse signature */ 176 if ((sig = DSA_SIG_new()) == NULL || 177 (sig->r = BN_new()) == NULL || 178 (sig->s = BN_new()) == NULL) { 179 ret = SSH_ERR_ALLOC_FAIL; 180 goto out; 181 } 182 if ((BN_bin2bn(sigblob, INTBLOB_LEN, sig->r) == NULL) || 183 (BN_bin2bn(sigblob+ INTBLOB_LEN, INTBLOB_LEN, sig->s) == NULL)) { 184 ret = SSH_ERR_LIBCRYPTO_ERROR; 185 goto out; 186 } 187 188 /* sha1 the data */ 189 if ((ret = ssh_digest_memory(SSH_DIGEST_SHA1, data, datalen, 190 digest, sizeof(digest))) != 0) 191 goto out; 192 193 switch (DSA_do_verify(digest, dlen, sig, key->dsa)) { 194 case 1: 195 ret = 0; 196 break; 197 case 0: 198 ret = SSH_ERR_SIGNATURE_INVALID; 199 goto out; 200 default: 201 ret = SSH_ERR_LIBCRYPTO_ERROR; 202 goto out; 203 } 204 205 out: 206 explicit_bzero(digest, sizeof(digest)); 207 if (sig != NULL) 208 DSA_SIG_free(sig); 209 if (b != NULL) 210 sshbuf_free(b); 211 if (ktype != NULL) 212 free(ktype); 213 if (sigblob != NULL) { 214 explicit_bzero(sigblob, len); 215 free(sigblob); 216 } 217 return ret; 218 } 219