1/* $OpenBSD: ssh-dss.c,v 1.37 2018/02/07 02:06:51 jsing 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#include "openbsd-compat/openssl-compat.h" 47 48#define INTBLOB_LEN 20 49#define SIGBLOB_LEN (2*INTBLOB_LEN) 50 51int 52ssh_dss_sign(const struct sshkey *key, u_char **sigp, size_t *lenp, 53 const u_char *data, size_t datalen, u_int compat) 54{ 55 DSA_SIG *sig = NULL; 56 const BIGNUM *sig_r, *sig_s; 57 u_char digest[SSH_DIGEST_MAX_LENGTH], sigblob[SIGBLOB_LEN]; 58 size_t rlen, slen, len, dlen = ssh_digest_bytes(SSH_DIGEST_SHA1); 59 struct sshbuf *b = NULL; 60 int ret = SSH_ERR_INVALID_ARGUMENT; 61 62 if (lenp != NULL) 63 *lenp = 0; 64 if (sigp != NULL) 65 *sigp = NULL; 66 67 if (key == NULL || key->dsa == NULL || 68 sshkey_type_plain(key->type) != KEY_DSA) 69 return SSH_ERR_INVALID_ARGUMENT; 70 if (dlen == 0) 71 return SSH_ERR_INTERNAL_ERROR; 72 73 if ((ret = ssh_digest_memory(SSH_DIGEST_SHA1, data, datalen, 74 digest, sizeof(digest))) != 0) 75 goto out; 76 77 if ((sig = DSA_do_sign(digest, dlen, key->dsa)) == NULL) { 78 ret = SSH_ERR_LIBCRYPTO_ERROR; 79 goto out; 80 } 81 82 DSA_SIG_get0(sig, &sig_r, &sig_s); 83 rlen = BN_num_bytes(sig_r); 84 slen = BN_num_bytes(sig_s); 85 if (rlen > INTBLOB_LEN || slen > INTBLOB_LEN) { 86 ret = SSH_ERR_INTERNAL_ERROR; 87 goto out; 88 } 89 explicit_bzero(sigblob, SIGBLOB_LEN); 90 BN_bn2bin(sig_r, sigblob + SIGBLOB_LEN - INTBLOB_LEN - rlen); 91 BN_bn2bin(sig_s, sigblob + SIGBLOB_LEN - slen); 92 93 if ((b = sshbuf_new()) == NULL) { 94 ret = SSH_ERR_ALLOC_FAIL; 95 goto out; 96 } 97 if ((ret = sshbuf_put_cstring(b, "ssh-dss")) != 0 || 98 (ret = sshbuf_put_string(b, sigblob, SIGBLOB_LEN)) != 0) 99 goto out; 100 101 len = sshbuf_len(b); 102 if (sigp != NULL) { 103 if ((*sigp = malloc(len)) == NULL) { 104 ret = SSH_ERR_ALLOC_FAIL; 105 goto out; 106 } 107 memcpy(*sigp, sshbuf_ptr(b), len); 108 } 109 if (lenp != NULL) 110 *lenp = len; 111 ret = 0; 112 out: 113 explicit_bzero(digest, sizeof(digest)); 114 DSA_SIG_free(sig); 115 sshbuf_free(b); 116 return ret; 117} 118 119int 120ssh_dss_verify(const struct sshkey *key, 121 const u_char *signature, size_t signaturelen, 122 const u_char *data, size_t datalen, u_int compat) 123{ 124 DSA_SIG *sig = NULL; 125 BIGNUM *sig_r = NULL, *sig_s = NULL; 126 u_char digest[SSH_DIGEST_MAX_LENGTH], *sigblob = NULL; 127 size_t len, dlen = ssh_digest_bytes(SSH_DIGEST_SHA1); 128 int ret = SSH_ERR_INTERNAL_ERROR; 129 struct sshbuf *b = NULL; 130 char *ktype = NULL; 131 132 if (key == NULL || key->dsa == NULL || 133 sshkey_type_plain(key->type) != KEY_DSA || 134 signature == NULL || signaturelen == 0) 135 return SSH_ERR_INVALID_ARGUMENT; 136 if (dlen == 0) 137 return SSH_ERR_INTERNAL_ERROR; 138 139 /* fetch signature */ 140 if ((b = sshbuf_from(signature, signaturelen)) == NULL) 141 return SSH_ERR_ALLOC_FAIL; 142 if (sshbuf_get_cstring(b, &ktype, NULL) != 0 || 143 sshbuf_get_string(b, &sigblob, &len) != 0) { 144 ret = SSH_ERR_INVALID_FORMAT; 145 goto out; 146 } 147 if (strcmp("ssh-dss", ktype) != 0) { 148 ret = SSH_ERR_KEY_TYPE_MISMATCH; 149 goto out; 150 } 151 if (sshbuf_len(b) != 0) { 152 ret = SSH_ERR_UNEXPECTED_TRAILING_DATA; 153 goto out; 154 } 155 156 if (len != SIGBLOB_LEN) { 157 ret = SSH_ERR_INVALID_FORMAT; 158 goto out; 159 } 160 161 /* parse signature */ 162 if ((sig = DSA_SIG_new()) == NULL || 163 (sig_r = BN_new()) == NULL || 164 (sig_s = BN_new()) == NULL) { 165 ret = SSH_ERR_ALLOC_FAIL; 166 goto out; 167 } 168 if ((BN_bin2bn(sigblob, INTBLOB_LEN, sig_r) == NULL) || 169 (BN_bin2bn(sigblob + INTBLOB_LEN, INTBLOB_LEN, sig_s) == NULL)) { 170 ret = SSH_ERR_LIBCRYPTO_ERROR; 171 goto out; 172 } 173 if (!DSA_SIG_set0(sig, sig_r, sig_s)) { 174 ret = SSH_ERR_LIBCRYPTO_ERROR; 175 goto out; 176 } 177 sig_r = sig_s = NULL; /* transferred */ 178 179 /* sha1 the data */ 180 if ((ret = ssh_digest_memory(SSH_DIGEST_SHA1, data, datalen, 181 digest, sizeof(digest))) != 0) 182 goto out; 183 184 switch (DSA_do_verify(digest, dlen, sig, key->dsa)) { 185 case 1: 186 ret = 0; 187 break; 188 case 0: 189 ret = SSH_ERR_SIGNATURE_INVALID; 190 goto out; 191 default: 192 ret = SSH_ERR_LIBCRYPTO_ERROR; 193 goto out; 194 } 195 196 out: 197 explicit_bzero(digest, sizeof(digest)); 198 DSA_SIG_free(sig); 199 BN_clear_free(sig_r); 200 BN_clear_free(sig_s); 201 sshbuf_free(b); 202 free(ktype); 203 if (sigblob != NULL) { 204 explicit_bzero(sigblob, len); 205 free(sigblob); 206 } 207 return ret; 208} 209#endif /* WITH_OPENSSL */ 210