1 /* 2 * Copyright (c) 2000 Markus Friedl. All rights reserved. 3 * 4 * Redistribution and use in source and binary forms, with or without 5 * modification, are permitted provided that the following conditions 6 * are met: 7 * 1. Redistributions of source code must retain the above copyright 8 * notice, this list of conditions and the following disclaimer. 9 * 2. Redistributions in binary form must reproduce the above copyright 10 * notice, this list of conditions and the following disclaimer in the 11 * documentation and/or other materials provided with the distribution. 12 * 13 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR 14 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES 15 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. 16 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, 17 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT 18 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, 19 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY 20 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT 21 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF 22 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 23 */ 24 25 #include "includes.h" 26 RCSID("$OpenBSD: ssh-dss.c,v 1.8 2001/09/17 19:27:15 stevesk Exp $"); 27 28 #include <openssl/bn.h> 29 #include <openssl/evp.h> 30 31 #include "xmalloc.h" 32 #include "buffer.h" 33 #include "bufaux.h" 34 #include "compat.h" 35 #include "log.h" 36 #include "key.h" 37 #include "ssh-dss.h" 38 39 #define INTBLOB_LEN 20 40 #define SIGBLOB_LEN (2*INTBLOB_LEN) 41 42 int 43 ssh_dss_sign( 44 Key *key, 45 u_char **sigp, int *lenp, 46 u_char *data, int datalen) 47 { 48 DSA_SIG *sig; 49 EVP_MD *evp_md = EVP_sha1(); 50 EVP_MD_CTX md; 51 u_char *digest, *ret, sigblob[SIGBLOB_LEN]; 52 u_int rlen, slen, len, dlen; 53 Buffer b; 54 55 if (key == NULL || key->type != KEY_DSA || key->dsa == NULL) { 56 error("ssh_dss_sign: no DSA key"); 57 return -1; 58 } 59 dlen = evp_md->md_size; 60 digest = xmalloc(dlen); 61 EVP_DigestInit(&md, evp_md); 62 EVP_DigestUpdate(&md, data, datalen); 63 EVP_DigestFinal(&md, digest, NULL); 64 65 sig = DSA_do_sign(digest, dlen, key->dsa); 66 67 memset(digest, 0, dlen); 68 xfree(digest); 69 if (sig == NULL) { 70 error("ssh_dss_sign: sign failed"); 71 return -1; 72 } 73 74 rlen = BN_num_bytes(sig->r); 75 slen = BN_num_bytes(sig->s); 76 if (rlen > INTBLOB_LEN || slen > INTBLOB_LEN) { 77 error("bad sig size %d %d", rlen, slen); 78 DSA_SIG_free(sig); 79 return -1; 80 } 81 memset(sigblob, 0, SIGBLOB_LEN); 82 BN_bn2bin(sig->r, sigblob+ SIGBLOB_LEN - INTBLOB_LEN - rlen); 83 BN_bn2bin(sig->s, sigblob+ SIGBLOB_LEN - slen); 84 DSA_SIG_free(sig); 85 86 if (datafellows & SSH_BUG_SIGBLOB) { 87 ret = xmalloc(SIGBLOB_LEN); 88 memcpy(ret, sigblob, SIGBLOB_LEN); 89 if (lenp != NULL) 90 *lenp = SIGBLOB_LEN; 91 if (sigp != NULL) 92 *sigp = ret; 93 } else { 94 /* ietf-drafts */ 95 buffer_init(&b); 96 buffer_put_cstring(&b, "ssh-dss"); 97 buffer_put_string(&b, sigblob, SIGBLOB_LEN); 98 len = buffer_len(&b); 99 ret = xmalloc(len); 100 memcpy(ret, buffer_ptr(&b), len); 101 buffer_free(&b); 102 if (lenp != NULL) 103 *lenp = len; 104 if (sigp != NULL) 105 *sigp = ret; 106 } 107 return 0; 108 } 109 int 110 ssh_dss_verify( 111 Key *key, 112 u_char *signature, int signaturelen, 113 u_char *data, int datalen) 114 { 115 DSA_SIG *sig; 116 EVP_MD *evp_md = EVP_sha1(); 117 EVP_MD_CTX md; 118 u_char *digest, *sigblob; 119 u_int len, dlen; 120 int rlen, ret; 121 Buffer b; 122 123 if (key == NULL || key->type != KEY_DSA || key->dsa == NULL) { 124 error("ssh_dss_verify: no DSA key"); 125 return -1; 126 } 127 128 /* fetch signature */ 129 if (datafellows & SSH_BUG_SIGBLOB) { 130 sigblob = signature; 131 len = signaturelen; 132 } else { 133 /* ietf-drafts */ 134 char *ktype; 135 buffer_init(&b); 136 buffer_append(&b, signature, signaturelen); 137 ktype = buffer_get_string(&b, NULL); 138 if (strcmp("ssh-dss", ktype) != 0) { 139 error("ssh_dss_verify: cannot handle type %s", ktype); 140 buffer_free(&b); 141 return -1; 142 } 143 sigblob = buffer_get_string(&b, &len); 144 rlen = buffer_len(&b); 145 if(rlen != 0) { 146 error("remaining bytes in signature %d", rlen); 147 buffer_free(&b); 148 return -1; 149 } 150 buffer_free(&b); 151 xfree(ktype); 152 } 153 154 if (len != SIGBLOB_LEN) { 155 fatal("bad sigbloblen %d != SIGBLOB_LEN", len); 156 } 157 158 /* parse signature */ 159 sig = DSA_SIG_new(); 160 sig->r = BN_new(); 161 sig->s = BN_new(); 162 BN_bin2bn(sigblob, INTBLOB_LEN, sig->r); 163 BN_bin2bn(sigblob+ INTBLOB_LEN, INTBLOB_LEN, sig->s); 164 165 if (!(datafellows & SSH_BUG_SIGBLOB)) { 166 memset(sigblob, 0, len); 167 xfree(sigblob); 168 } 169 170 /* sha1 the data */ 171 dlen = evp_md->md_size; 172 digest = xmalloc(dlen); 173 EVP_DigestInit(&md, evp_md); 174 EVP_DigestUpdate(&md, data, datalen); 175 EVP_DigestFinal(&md, digest, NULL); 176 177 ret = DSA_do_verify(digest, dlen, sig, key->dsa); 178 179 memset(digest, 0, dlen); 180 xfree(digest); 181 DSA_SIG_free(sig); 182 183 debug("ssh_dss_verify: signature %s", 184 ret == 1 ? "correct" : ret == 0 ? "incorrect" : "error"); 185 return ret; 186 } 187