1 /* $OpenBSD: ssh-dss.c,v 1.35 2016/04/21 06:08:02 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 #ifdef WITH_OPENSSL 29 30 #include <sys/types.h> 31 32 #include <openssl/bn.h> 33 #include <openssl/dsa.h> 34 #include <openssl/evp.h> 35 36 #include <stdarg.h> 37 #include <string.h> 38 39 #include "sshbuf.h" 40 #include "compat.h" 41 #include "ssherr.h" 42 #include "digest.h" 43 #define SSHKEY_INTERNAL 44 #include "sshkey.h" 45 46 #define INTBLOB_LEN 20 47 #define SIGBLOB_LEN (2*INTBLOB_LEN) 48 49 int 50 ssh_dss_sign(const struct sshkey *key, u_char **sigp, size_t *lenp, 51 const u_char *data, size_t datalen, u_int compat) 52 { 53 DSA_SIG *sig = NULL; 54 u_char digest[SSH_DIGEST_MAX_LENGTH], sigblob[SIGBLOB_LEN]; 55 size_t rlen, slen, len, dlen = ssh_digest_bytes(SSH_DIGEST_SHA1); 56 struct sshbuf *b = NULL; 57 int ret = SSH_ERR_INVALID_ARGUMENT; 58 59 if (lenp != NULL) 60 *lenp = 0; 61 if (sigp != NULL) 62 *sigp = NULL; 63 64 if (key == NULL || key->dsa == NULL || 65 sshkey_type_plain(key->type) != KEY_DSA) 66 return SSH_ERR_INVALID_ARGUMENT; 67 if (dlen == 0) 68 return SSH_ERR_INTERNAL_ERROR; 69 70 if ((ret = ssh_digest_memory(SSH_DIGEST_SHA1, data, datalen, 71 digest, sizeof(digest))) != 0) 72 goto out; 73 74 if ((sig = DSA_do_sign(digest, dlen, key->dsa)) == NULL) { 75 ret = SSH_ERR_LIBCRYPTO_ERROR; 76 goto out; 77 } 78 79 rlen = BN_num_bytes(sig->r); 80 slen = BN_num_bytes(sig->s); 81 if (rlen > INTBLOB_LEN || slen > INTBLOB_LEN) { 82 ret = SSH_ERR_INTERNAL_ERROR; 83 goto out; 84 } 85 explicit_bzero(sigblob, SIGBLOB_LEN); 86 BN_bn2bin(sig->r, sigblob + SIGBLOB_LEN - INTBLOB_LEN - rlen); 87 BN_bn2bin(sig->s, sigblob + SIGBLOB_LEN - slen); 88 89 if (compat & SSH_BUG_SIGBLOB) { 90 if (sigp != NULL) { 91 if ((*sigp = malloc(SIGBLOB_LEN)) == NULL) { 92 ret = SSH_ERR_ALLOC_FAIL; 93 goto out; 94 } 95 memcpy(*sigp, sigblob, SIGBLOB_LEN); 96 } 97 if (lenp != NULL) 98 *lenp = SIGBLOB_LEN; 99 ret = 0; 100 } else { 101 /* ietf-drafts */ 102 if ((b = sshbuf_new()) == NULL) { 103 ret = SSH_ERR_ALLOC_FAIL; 104 goto out; 105 } 106 if ((ret = sshbuf_put_cstring(b, "ssh-dss")) != 0 || 107 (ret = sshbuf_put_string(b, sigblob, SIGBLOB_LEN)) != 0) 108 goto out; 109 len = sshbuf_len(b); 110 if (sigp != NULL) { 111 if ((*sigp = malloc(len)) == NULL) { 112 ret = SSH_ERR_ALLOC_FAIL; 113 goto out; 114 } 115 memcpy(*sigp, sshbuf_ptr(b), len); 116 } 117 if (lenp != NULL) 118 *lenp = len; 119 ret = 0; 120 } 121 out: 122 explicit_bzero(digest, sizeof(digest)); 123 if (sig != NULL) 124 DSA_SIG_free(sig); 125 sshbuf_free(b); 126 return ret; 127 } 128 129 int 130 ssh_dss_verify(const struct sshkey *key, 131 const u_char *signature, size_t signaturelen, 132 const u_char *data, size_t datalen, u_int compat) 133 { 134 DSA_SIG *sig = NULL; 135 u_char digest[SSH_DIGEST_MAX_LENGTH], *sigblob = NULL; 136 size_t len, dlen = ssh_digest_bytes(SSH_DIGEST_SHA1); 137 int ret = SSH_ERR_INTERNAL_ERROR; 138 struct sshbuf *b = NULL; 139 char *ktype = NULL; 140 141 if (key == NULL || key->dsa == NULL || 142 sshkey_type_plain(key->type) != KEY_DSA || 143 signature == NULL || signaturelen == 0) 144 return SSH_ERR_INVALID_ARGUMENT; 145 if (dlen == 0) 146 return SSH_ERR_INTERNAL_ERROR; 147 148 /* fetch signature */ 149 if (compat & SSH_BUG_SIGBLOB) { 150 if ((sigblob = malloc(signaturelen)) == NULL) 151 return SSH_ERR_ALLOC_FAIL; 152 memcpy(sigblob, signature, signaturelen); 153 len = signaturelen; 154 } else { 155 /* ietf-drafts */ 156 if ((b = sshbuf_from(signature, signaturelen)) == NULL) 157 return SSH_ERR_ALLOC_FAIL; 158 if (sshbuf_get_cstring(b, &ktype, NULL) != 0 || 159 sshbuf_get_string(b, &sigblob, &len) != 0) { 160 ret = SSH_ERR_INVALID_FORMAT; 161 goto out; 162 } 163 if (strcmp("ssh-dss", ktype) != 0) { 164 ret = SSH_ERR_KEY_TYPE_MISMATCH; 165 goto out; 166 } 167 if (sshbuf_len(b) != 0) { 168 ret = SSH_ERR_UNEXPECTED_TRAILING_DATA; 169 goto out; 170 } 171 } 172 173 if (len != SIGBLOB_LEN) { 174 ret = SSH_ERR_INVALID_FORMAT; 175 goto out; 176 } 177 178 /* parse signature */ 179 if ((sig = DSA_SIG_new()) == NULL || 180 (sig->r = BN_new()) == NULL || 181 (sig->s = BN_new()) == NULL) { 182 ret = SSH_ERR_ALLOC_FAIL; 183 goto out; 184 } 185 if ((BN_bin2bn(sigblob, INTBLOB_LEN, sig->r) == NULL) || 186 (BN_bin2bn(sigblob+ INTBLOB_LEN, INTBLOB_LEN, sig->s) == NULL)) { 187 ret = SSH_ERR_LIBCRYPTO_ERROR; 188 goto out; 189 } 190 191 /* sha1 the data */ 192 if ((ret = ssh_digest_memory(SSH_DIGEST_SHA1, data, datalen, 193 digest, sizeof(digest))) != 0) 194 goto out; 195 196 switch (DSA_do_verify(digest, dlen, sig, key->dsa)) { 197 case 1: 198 ret = 0; 199 break; 200 case 0: 201 ret = SSH_ERR_SIGNATURE_INVALID; 202 goto out; 203 default: 204 ret = SSH_ERR_LIBCRYPTO_ERROR; 205 goto out; 206 } 207 208 out: 209 explicit_bzero(digest, sizeof(digest)); 210 if (sig != NULL) 211 DSA_SIG_free(sig); 212 sshbuf_free(b); 213 free(ktype); 214 if (sigblob != NULL) { 215 explicit_bzero(sigblob, len); 216 free(sigblob); 217 } 218 return ret; 219 } 220 #endif /* WITH_OPENSSL */ 221