1 /* $OpenBSD: ssh-dss.c,v 1.31 2014/02/02 03:44:31 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/evp.h> 32 33 #include <stdarg.h> 34 #include <string.h> 35 36 #include "xmalloc.h" 37 #include "buffer.h" 38 #include "compat.h" 39 #include "log.h" 40 #include "key.h" 41 #include "digest.h" 42 43 #define INTBLOB_LEN 20 44 #define SIGBLOB_LEN (2*INTBLOB_LEN) 45 46 int 47 ssh_dss_sign(const Key *key, u_char **sigp, u_int *lenp, 48 const u_char *data, u_int datalen) 49 { 50 DSA_SIG *sig; 51 u_char digest[SSH_DIGEST_MAX_LENGTH], sigblob[SIGBLOB_LEN]; 52 u_int rlen, slen, len, dlen = ssh_digest_bytes(SSH_DIGEST_SHA1); 53 Buffer b; 54 55 if (key == NULL || key_type_plain(key->type) != KEY_DSA || 56 key->dsa == NULL) { 57 error("%s: no DSA key", __func__); 58 return -1; 59 } 60 61 if (ssh_digest_memory(SSH_DIGEST_SHA1, data, datalen, 62 digest, sizeof(digest)) != 0) { 63 error("%s: ssh_digest_memory failed", __func__); 64 return -1; 65 } 66 67 sig = DSA_do_sign(digest, dlen, key->dsa); 68 explicit_bzero(digest, sizeof(digest)); 69 70 if (sig == NULL) { 71 error("ssh_dss_sign: sign failed"); 72 return -1; 73 } 74 75 rlen = BN_num_bytes(sig->r); 76 slen = BN_num_bytes(sig->s); 77 if (rlen > INTBLOB_LEN || slen > INTBLOB_LEN) { 78 error("bad sig size %u %u", rlen, slen); 79 DSA_SIG_free(sig); 80 return -1; 81 } 82 explicit_bzero(sigblob, SIGBLOB_LEN); 83 BN_bn2bin(sig->r, sigblob+ SIGBLOB_LEN - INTBLOB_LEN - rlen); 84 BN_bn2bin(sig->s, sigblob+ SIGBLOB_LEN - slen); 85 DSA_SIG_free(sig); 86 87 if (datafellows & SSH_BUG_SIGBLOB) { 88 if (lenp != NULL) 89 *lenp = SIGBLOB_LEN; 90 if (sigp != NULL) { 91 *sigp = xmalloc(SIGBLOB_LEN); 92 memcpy(*sigp, sigblob, SIGBLOB_LEN); 93 } 94 } else { 95 /* ietf-drafts */ 96 buffer_init(&b); 97 buffer_put_cstring(&b, "ssh-dss"); 98 buffer_put_string(&b, sigblob, SIGBLOB_LEN); 99 len = buffer_len(&b); 100 if (lenp != NULL) 101 *lenp = len; 102 if (sigp != NULL) { 103 *sigp = xmalloc(len); 104 memcpy(*sigp, buffer_ptr(&b), len); 105 } 106 buffer_free(&b); 107 } 108 return 0; 109 } 110 int 111 ssh_dss_verify(const Key *key, const u_char *signature, u_int signaturelen, 112 const u_char *data, u_int datalen) 113 { 114 DSA_SIG *sig; 115 u_char digest[SSH_DIGEST_MAX_LENGTH], *sigblob; 116 u_int len, dlen = ssh_digest_bytes(SSH_DIGEST_SHA1); 117 int rlen, ret; 118 Buffer b; 119 120 if (key == NULL || key_type_plain(key->type) != KEY_DSA || 121 key->dsa == NULL) { 122 error("%s: no DSA key", __func__); 123 return -1; 124 } 125 126 /* fetch signature */ 127 if (datafellows & SSH_BUG_SIGBLOB) { 128 sigblob = xmalloc(signaturelen); 129 memcpy(sigblob, signature, signaturelen); 130 len = signaturelen; 131 } else { 132 /* ietf-drafts */ 133 char *ktype; 134 buffer_init(&b); 135 buffer_append(&b, signature, signaturelen); 136 ktype = buffer_get_cstring(&b, NULL); 137 if (strcmp("ssh-dss", ktype) != 0) { 138 error("%s: cannot handle type %s", __func__, ktype); 139 buffer_free(&b); 140 free(ktype); 141 return -1; 142 } 143 free(ktype); 144 sigblob = buffer_get_string(&b, &len); 145 rlen = buffer_len(&b); 146 buffer_free(&b); 147 if (rlen != 0) { 148 error("%s: remaining bytes in signature %d", 149 __func__, rlen); 150 free(sigblob); 151 return -1; 152 } 153 } 154 155 if (len != SIGBLOB_LEN) { 156 fatal("bad sigbloblen %u != SIGBLOB_LEN", len); 157 } 158 159 /* parse signature */ 160 if ((sig = DSA_SIG_new()) == NULL) 161 fatal("%s: DSA_SIG_new failed", __func__); 162 if ((sig->r = BN_new()) == NULL) 163 fatal("%s: BN_new failed", __func__); 164 if ((sig->s = BN_new()) == NULL) 165 fatal("ssh_dss_verify: BN_new failed"); 166 if ((BN_bin2bn(sigblob, INTBLOB_LEN, sig->r) == NULL) || 167 (BN_bin2bn(sigblob+ INTBLOB_LEN, INTBLOB_LEN, sig->s) == NULL)) 168 fatal("%s: BN_bin2bn failed", __func__); 169 170 /* clean up */ 171 explicit_bzero(sigblob, len); 172 free(sigblob); 173 174 /* sha1 the data */ 175 if (ssh_digest_memory(SSH_DIGEST_SHA1, data, datalen, 176 digest, sizeof(digest)) != 0) { 177 error("%s: digest_memory failed", __func__); 178 return -1; 179 } 180 181 ret = DSA_do_verify(digest, dlen, sig, key->dsa); 182 explicit_bzero(digest, sizeof(digest)); 183 184 DSA_SIG_free(sig); 185 186 debug("%s: signature %s", __func__, 187 ret == 1 ? "correct" : ret == 0 ? "incorrect" : "error"); 188 return ret; 189 } 190