1 /* $NetBSD: ssh-dss.c,v 1.14 2018/04/06 18:59:00 christos Exp $ */ 2 /* $OpenBSD: ssh-dss.c,v 1.37 2018/02/07 02:06:51 jsing 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 1.14 2018/04/06 18:59:00 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 const BIGNUM *r, *s; 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 DSA_SIG_get0(sig, &r, &s); 78 rlen = BN_num_bytes(r); 79 slen = BN_num_bytes(s); 80 if (rlen > INTBLOB_LEN || slen > INTBLOB_LEN) { 81 ret = SSH_ERR_INTERNAL_ERROR; 82 goto out; 83 } 84 explicit_bzero(sigblob, SIGBLOB_LEN); 85 BN_bn2bin(r, sigblob + SIGBLOB_LEN - INTBLOB_LEN - rlen); 86 BN_bn2bin(s, sigblob + SIGBLOB_LEN - slen); 87 88 if ((b = sshbuf_new()) == NULL) { 89 ret = SSH_ERR_ALLOC_FAIL; 90 goto out; 91 } 92 if ((ret = sshbuf_put_cstring(b, "ssh-dss")) != 0 || 93 (ret = sshbuf_put_string(b, sigblob, SIGBLOB_LEN)) != 0) 94 goto out; 95 96 len = sshbuf_len(b); 97 if (sigp != NULL) { 98 if ((*sigp = malloc(len)) == NULL) { 99 ret = SSH_ERR_ALLOC_FAIL; 100 goto out; 101 } 102 memcpy(*sigp, sshbuf_ptr(b), len); 103 } 104 if (lenp != NULL) 105 *lenp = len; 106 ret = 0; 107 out: 108 explicit_bzero(digest, sizeof(digest)); 109 DSA_SIG_free(sig); 110 sshbuf_free(b); 111 return ret; 112 } 113 114 int 115 ssh_dss_verify(const struct sshkey *key, 116 const u_char *signature, size_t signaturelen, 117 const u_char *data, size_t datalen, u_int compat) 118 { 119 DSA_SIG *sig = NULL; 120 u_char digest[SSH_DIGEST_MAX_LENGTH], *sigblob = NULL; 121 size_t len, dlen = ssh_digest_bytes(SSH_DIGEST_SHA1); 122 int ret = SSH_ERR_INTERNAL_ERROR; 123 struct sshbuf *b = NULL; 124 char *ktype = NULL; 125 126 if (key == NULL || key->dsa == NULL || 127 sshkey_type_plain(key->type) != KEY_DSA || 128 signature == NULL || signaturelen == 0) 129 return SSH_ERR_INVALID_ARGUMENT; 130 if (dlen == 0) 131 return SSH_ERR_INTERNAL_ERROR; 132 133 /* fetch signature */ 134 if ((b = sshbuf_from(signature, signaturelen)) == NULL) 135 return SSH_ERR_ALLOC_FAIL; 136 if (sshbuf_get_cstring(b, &ktype, NULL) != 0 || 137 sshbuf_get_string(b, &sigblob, &len) != 0) { 138 ret = SSH_ERR_INVALID_FORMAT; 139 goto out; 140 } 141 if (strcmp("ssh-dss", ktype) != 0) { 142 ret = SSH_ERR_KEY_TYPE_MISMATCH; 143 goto out; 144 } 145 if (sshbuf_len(b) != 0) { 146 ret = SSH_ERR_UNEXPECTED_TRAILING_DATA; 147 goto out; 148 } 149 150 if (len != SIGBLOB_LEN) { 151 ret = SSH_ERR_INVALID_FORMAT; 152 goto out; 153 } 154 155 /* parse signature */ 156 BIGNUM *r=NULL, *s=NULL; 157 if ((sig = DSA_SIG_new()) == NULL || 158 (r = BN_new()) == NULL || 159 (s = BN_new()) == NULL) { 160 ret = SSH_ERR_ALLOC_FAIL; 161 BN_free(r); 162 BN_free(s); 163 goto out; 164 } 165 if ((BN_bin2bn(sigblob, INTBLOB_LEN, r) == NULL) || 166 (BN_bin2bn(sigblob+ INTBLOB_LEN, INTBLOB_LEN, s) == NULL)) { 167 ret = SSH_ERR_LIBCRYPTO_ERROR; 168 BN_free(r); 169 BN_free(s); 170 goto out; 171 } 172 DSA_SIG_set0(sig, r, s); 173 r = s = NULL; 174 175 /* sha1 the data */ 176 if ((ret = ssh_digest_memory(SSH_DIGEST_SHA1, data, datalen, 177 digest, sizeof(digest))) != 0) 178 goto out; 179 180 switch (DSA_do_verify(digest, dlen, sig, key->dsa)) { 181 case 1: 182 ret = 0; 183 break; 184 case 0: 185 ret = SSH_ERR_SIGNATURE_INVALID; 186 goto out; 187 default: 188 ret = SSH_ERR_LIBCRYPTO_ERROR; 189 goto out; 190 } 191 192 out: 193 explicit_bzero(digest, sizeof(digest)); 194 DSA_SIG_free(sig); 195 sshbuf_free(b); 196 free(ktype); 197 if (sigblob != NULL) { 198 explicit_bzero(sigblob, len); 199 free(sigblob); 200 } 201 return ret; 202 } 203