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 <sys/types.h> 27 28 #include <openssl/bn.h> 29 #include <openssl/evp.h> 30 31 #include <string.h> 32 33 #include "sshbuf.h" 34 #include "compat.h" 35 #include "ssherr.h" 36 #include "digest.h" 37 #define SSHKEY_INTERNAL 38 #include "sshkey.h" 39 40 #define INTBLOB_LEN 20 41 #define SIGBLOB_LEN (2*INTBLOB_LEN) 42 43 int 44 ssh_dss_sign(const struct sshkey *key, u_char **sigp, size_t *lenp, 45 const u_char *data, size_t datalen, u_int compat) 46 { 47 DSA_SIG *sig = NULL; 48 u_char digest[SSH_DIGEST_MAX_LENGTH], sigblob[SIGBLOB_LEN]; 49 size_t rlen, slen, len, dlen = ssh_digest_bytes(SSH_DIGEST_SHA1); 50 struct sshbuf *b = NULL; 51 int ret = SSH_ERR_INVALID_ARGUMENT; 52 53 if (lenp != NULL) 54 *lenp = 0; 55 if (sigp != NULL) 56 *sigp = NULL; 57 58 if (key == NULL || key->dsa == NULL || 59 sshkey_type_plain(key->type) != KEY_DSA) 60 return SSH_ERR_INVALID_ARGUMENT; 61 if (dlen == 0) 62 return SSH_ERR_INTERNAL_ERROR; 63 64 if ((ret = ssh_digest_memory(SSH_DIGEST_SHA1, data, datalen, 65 digest, sizeof(digest))) != 0) 66 goto out; 67 68 if ((sig = DSA_do_sign(digest, dlen, key->dsa)) == NULL) { 69 ret = SSH_ERR_LIBCRYPTO_ERROR; 70 goto out; 71 } 72 73 rlen = BN_num_bytes(sig->r); 74 slen = BN_num_bytes(sig->s); 75 if (rlen > INTBLOB_LEN || slen > INTBLOB_LEN) { 76 ret = SSH_ERR_INTERNAL_ERROR; 77 goto out; 78 } 79 explicit_bzero(sigblob, SIGBLOB_LEN); 80 BN_bn2bin(sig->r, sigblob + SIGBLOB_LEN - INTBLOB_LEN - rlen); 81 BN_bn2bin(sig->s, sigblob + SIGBLOB_LEN - slen); 82 83 if (compat & SSH_BUG_SIGBLOB) { 84 if (sigp != NULL) { 85 if ((*sigp = malloc(SIGBLOB_LEN)) == NULL) { 86 ret = SSH_ERR_ALLOC_FAIL; 87 goto out; 88 } 89 memcpy(*sigp, sigblob, SIGBLOB_LEN); 90 } 91 if (lenp != NULL) 92 *lenp = SIGBLOB_LEN; 93 ret = 0; 94 } else { 95 /* ietf-drafts */ 96 if ((b = sshbuf_new()) == NULL) { 97 ret = SSH_ERR_ALLOC_FAIL; 98 goto out; 99 } 100 if ((ret = sshbuf_put_cstring(b, "ssh-dss")) != 0 || 101 (ret = sshbuf_put_string(b, sigblob, SIGBLOB_LEN)) != 0) 102 goto out; 103 len = sshbuf_len(b); 104 if (sigp != NULL) { 105 if ((*sigp = malloc(len)) == NULL) { 106 ret = SSH_ERR_ALLOC_FAIL; 107 goto out; 108 } 109 memcpy(*sigp, sshbuf_ptr(b), len); 110 } 111 if (lenp != NULL) 112 *lenp = len; 113 ret = 0; 114 } 115 out: 116 explicit_bzero(digest, sizeof(digest)); 117 if (sig != NULL) 118 DSA_SIG_free(sig); 119 sshbuf_free(b); 120 return ret; 121 } 122 123 int 124 ssh_dss_verify(const struct sshkey *key, 125 const u_char *signature, size_t signaturelen, 126 const u_char *data, size_t datalen, u_int compat) 127 { 128 DSA_SIG *sig = NULL; 129 u_char digest[SSH_DIGEST_MAX_LENGTH], *sigblob = NULL; 130 size_t len, dlen = ssh_digest_bytes(SSH_DIGEST_SHA1); 131 int ret = SSH_ERR_INTERNAL_ERROR; 132 struct sshbuf *b = NULL; 133 char *ktype = NULL; 134 135 if (key == NULL || key->dsa == NULL || 136 sshkey_type_plain(key->type) != KEY_DSA || 137 signature == NULL || signaturelen == 0) 138 return SSH_ERR_INVALID_ARGUMENT; 139 if (dlen == 0) 140 return SSH_ERR_INTERNAL_ERROR; 141 142 /* fetch signature */ 143 if (compat & SSH_BUG_SIGBLOB) { 144 if ((sigblob = malloc(signaturelen)) == NULL) 145 return SSH_ERR_ALLOC_FAIL; 146 memcpy(sigblob, signature, signaturelen); 147 len = signaturelen; 148 } else { 149 /* ietf-drafts */ 150 if ((b = sshbuf_from(signature, signaturelen)) == NULL) 151 return SSH_ERR_ALLOC_FAIL; 152 if (sshbuf_get_cstring(b, &ktype, NULL) != 0 || 153 sshbuf_get_string(b, &sigblob, &len) != 0) { 154 ret = SSH_ERR_INVALID_FORMAT; 155 goto out; 156 } 157 if (strcmp("ssh-dss", ktype) != 0) { 158 ret = SSH_ERR_KEY_TYPE_MISMATCH; 159 goto out; 160 } 161 if (sshbuf_len(b) != 0) { 162 ret = SSH_ERR_UNEXPECTED_TRAILING_DATA; 163 goto out; 164 } 165 } 166 167 if (len != SIGBLOB_LEN) { 168 ret = SSH_ERR_INVALID_FORMAT; 169 goto out; 170 } 171 172 /* parse signature */ 173 if ((sig = DSA_SIG_new()) == NULL || 174 (sig->r = BN_new()) == NULL || 175 (sig->s = BN_new()) == NULL) { 176 ret = SSH_ERR_ALLOC_FAIL; 177 goto out; 178 } 179 if ((BN_bin2bn(sigblob, INTBLOB_LEN, sig->r) == NULL) || 180 (BN_bin2bn(sigblob+ INTBLOB_LEN, INTBLOB_LEN, sig->s) == NULL)) { 181 ret = SSH_ERR_LIBCRYPTO_ERROR; 182 goto out; 183 } 184 185 /* sha1 the data */ 186 if ((ret = ssh_digest_memory(SSH_DIGEST_SHA1, data, datalen, 187 digest, sizeof(digest))) != 0) 188 goto out; 189 190 switch (DSA_do_verify(digest, dlen, sig, key->dsa)) { 191 case 1: 192 ret = 0; 193 break; 194 case 0: 195 ret = SSH_ERR_SIGNATURE_INVALID; 196 goto out; 197 default: 198 ret = SSH_ERR_LIBCRYPTO_ERROR; 199 goto out; 200 } 201 202 out: 203 explicit_bzero(digest, sizeof(digest)); 204 if (sig != NULL) 205 DSA_SIG_free(sig); 206 sshbuf_free(b); 207 free(ktype); 208 if (sigblob != NULL) { 209 explicit_bzero(sigblob, len); 210 free(sigblob); 211 } 212 return ret; 213 } 214