1 /* $OpenBSD: ssh-dss.c,v 1.32 2014/06/24 01:13:21 djm Exp $ */ 2 /* 3 * Copyright (c) 2000 Markus Friedl. All rights reserved. 4 * 5 * Redistribution and use in source and binary forms, with or without 6 * modification, are permitted provided that the following conditions 7 * are met: 8 * 1. Redistributions of source code must retain the above copyright 9 * notice, this list of conditions and the following disclaimer. 10 * 2. Redistributions in binary form must reproduce the above copyright 11 * notice, this list of conditions and the following disclaimer in the 12 * documentation and/or other materials provided with the distribution. 13 * 14 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR 15 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES 16 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. 17 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, 18 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT 19 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, 20 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY 21 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT 22 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF 23 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 24 */ 25 26 #include "includes.h" 27 28 #include <sys/types.h> 29 30 #include <openssl/bn.h> 31 #include <openssl/dsa.h> 32 #include <openssl/evp.h> 33 34 #include <stdarg.h> 35 #include <string.h> 36 37 #include "sshbuf.h" 38 #include "compat.h" 39 #include "ssherr.h" 40 #include "digest.h" 41 #define SSHKEY_INTERNAL 42 #include "sshkey.h" 43 44 #define INTBLOB_LEN 20 45 #define SIGBLOB_LEN (2*INTBLOB_LEN) 46 47 int 48 ssh_dss_sign(const struct sshkey *key, u_char **sigp, size_t *lenp, 49 const u_char *data, size_t datalen, u_int compat) 50 { 51 DSA_SIG *sig = NULL; 52 u_char digest[SSH_DIGEST_MAX_LENGTH], sigblob[SIGBLOB_LEN]; 53 size_t rlen, slen, len, dlen = ssh_digest_bytes(SSH_DIGEST_SHA1); 54 struct sshbuf *b = NULL; 55 int ret = SSH_ERR_INVALID_ARGUMENT; 56 57 if (lenp != NULL) 58 *lenp = 0; 59 if (sigp != NULL) 60 *sigp = NULL; 61 62 if (key == NULL || key->dsa == NULL || 63 sshkey_type_plain(key->type) != KEY_DSA) 64 return SSH_ERR_INVALID_ARGUMENT; 65 if (dlen == 0) 66 return SSH_ERR_INTERNAL_ERROR; 67 68 if ((ret = ssh_digest_memory(SSH_DIGEST_SHA1, data, datalen, 69 digest, sizeof(digest))) != 0) 70 goto out; 71 72 if ((sig = DSA_do_sign(digest, dlen, key->dsa)) == NULL) { 73 ret = SSH_ERR_LIBCRYPTO_ERROR; 74 goto out; 75 } 76 77 rlen = BN_num_bytes(sig->r); 78 slen = BN_num_bytes(sig->s); 79 if (rlen > INTBLOB_LEN || slen > INTBLOB_LEN) { 80 ret = SSH_ERR_INTERNAL_ERROR; 81 goto out; 82 } 83 explicit_bzero(sigblob, SIGBLOB_LEN); 84 BN_bn2bin(sig->r, sigblob + SIGBLOB_LEN - INTBLOB_LEN - rlen); 85 BN_bn2bin(sig->s, sigblob + SIGBLOB_LEN - slen); 86 87 if (compat & SSH_BUG_SIGBLOB) { 88 if (sigp != NULL) { 89 if ((*sigp = malloc(SIGBLOB_LEN)) == NULL) { 90 ret = SSH_ERR_ALLOC_FAIL; 91 goto out; 92 } 93 memcpy(*sigp, sigblob, SIGBLOB_LEN); 94 } 95 if (lenp != NULL) 96 *lenp = SIGBLOB_LEN; 97 ret = 0; 98 } else { 99 /* ietf-drafts */ 100 if ((b = sshbuf_new()) == NULL) { 101 ret = SSH_ERR_ALLOC_FAIL; 102 goto out; 103 } 104 if ((ret = sshbuf_put_cstring(b, "ssh-dss")) != 0 || 105 (ret = sshbuf_put_string(b, sigblob, SIGBLOB_LEN)) != 0) 106 goto out; 107 len = sshbuf_len(b); 108 if (sigp != NULL) { 109 if ((*sigp = malloc(len)) == NULL) { 110 ret = SSH_ERR_ALLOC_FAIL; 111 goto out; 112 } 113 memcpy(*sigp, sshbuf_ptr(b), len); 114 } 115 if (lenp != NULL) 116 *lenp = len; 117 ret = 0; 118 } 119 out: 120 explicit_bzero(digest, sizeof(digest)); 121 if (sig != NULL) 122 DSA_SIG_free(sig); 123 if (b != NULL) 124 sshbuf_free(b); 125 return ret; 126 } 127 128 int 129 ssh_dss_verify(const struct sshkey *key, 130 const u_char *signature, size_t signaturelen, 131 const u_char *data, size_t datalen, u_int compat) 132 { 133 DSA_SIG *sig = NULL; 134 u_char digest[SSH_DIGEST_MAX_LENGTH], *sigblob = NULL; 135 size_t len, dlen = ssh_digest_bytes(SSH_DIGEST_SHA1); 136 int ret = SSH_ERR_INTERNAL_ERROR; 137 struct sshbuf *b = NULL; 138 char *ktype = NULL; 139 140 if (key == NULL || key->dsa == NULL || 141 sshkey_type_plain(key->type) != KEY_DSA) 142 return SSH_ERR_INVALID_ARGUMENT; 143 if (dlen == 0) 144 return SSH_ERR_INTERNAL_ERROR; 145 146 /* fetch signature */ 147 if (compat & SSH_BUG_SIGBLOB) { 148 if ((sigblob = malloc(signaturelen)) == NULL) 149 return SSH_ERR_ALLOC_FAIL; 150 memcpy(sigblob, signature, signaturelen); 151 len = signaturelen; 152 } else { 153 /* ietf-drafts */ 154 if ((b = sshbuf_from(signature, signaturelen)) == NULL) 155 return SSH_ERR_ALLOC_FAIL; 156 if (sshbuf_get_cstring(b, &ktype, NULL) != 0 || 157 sshbuf_get_string(b, &sigblob, &len) != 0) { 158 ret = SSH_ERR_INVALID_FORMAT; 159 goto out; 160 } 161 if (strcmp("ssh-dss", ktype) != 0) { 162 ret = SSH_ERR_KEY_TYPE_MISMATCH; 163 goto out; 164 } 165 if (sshbuf_len(b) != 0) { 166 ret = SSH_ERR_UNEXPECTED_TRAILING_DATA; 167 goto out; 168 } 169 } 170 171 if (len != SIGBLOB_LEN) { 172 ret = SSH_ERR_INVALID_FORMAT; 173 goto out; 174 } 175 176 /* parse signature */ 177 if ((sig = DSA_SIG_new()) == NULL || 178 (sig->r = BN_new()) == NULL || 179 (sig->s = BN_new()) == NULL) { 180 ret = SSH_ERR_ALLOC_FAIL; 181 goto out; 182 } 183 if ((BN_bin2bn(sigblob, INTBLOB_LEN, sig->r) == NULL) || 184 (BN_bin2bn(sigblob+ INTBLOB_LEN, INTBLOB_LEN, sig->s) == NULL)) { 185 ret = SSH_ERR_LIBCRYPTO_ERROR; 186 goto out; 187 } 188 189 /* sha1 the data */ 190 if ((ret = ssh_digest_memory(SSH_DIGEST_SHA1, data, datalen, 191 digest, sizeof(digest))) != 0) 192 goto out; 193 194 switch (DSA_do_verify(digest, dlen, sig, key->dsa)) { 195 case 1: 196 ret = 0; 197 break; 198 case 0: 199 ret = SSH_ERR_SIGNATURE_INVALID; 200 goto out; 201 default: 202 ret = SSH_ERR_LIBCRYPTO_ERROR; 203 goto out; 204 } 205 206 out: 207 explicit_bzero(digest, sizeof(digest)); 208 if (sig != NULL) 209 DSA_SIG_free(sig); 210 if (b != NULL) 211 sshbuf_free(b); 212 if (ktype != NULL) 213 free(ktype); 214 if (sigblob != NULL) { 215 explicit_bzero(sigblob, len); 216 free(sigblob); 217 } 218 return ret; 219 } 220