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 1.17 2002/07/04 10:41:47 markus 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(Key *key, u_char **sigp, u_int *lenp, 44 u_char *data, u_int datalen) 45 { 46 DSA_SIG *sig; 47 const EVP_MD *evp_md = EVP_sha1(); 48 EVP_MD_CTX md; 49 u_char digest[EVP_MAX_MD_SIZE], sigblob[SIGBLOB_LEN]; 50 u_int rlen, slen, len, dlen; 51 Buffer b; 52 53 if (key == NULL || key->type != KEY_DSA || key->dsa == NULL) { 54 error("ssh_dss_sign: no DSA key"); 55 return -1; 56 } 57 EVP_DigestInit(&md, evp_md); 58 EVP_DigestUpdate(&md, data, datalen); 59 EVP_DigestFinal(&md, digest, &dlen); 60 61 sig = DSA_do_sign(digest, dlen, key->dsa); 62 memset(digest, 'd', sizeof(digest)); 63 64 if (sig == NULL) { 65 error("ssh_dss_sign: sign failed"); 66 return -1; 67 } 68 69 rlen = BN_num_bytes(sig->r); 70 slen = BN_num_bytes(sig->s); 71 if (rlen > INTBLOB_LEN || slen > INTBLOB_LEN) { 72 error("bad sig size %u %u", rlen, slen); 73 DSA_SIG_free(sig); 74 return -1; 75 } 76 memset(sigblob, 0, SIGBLOB_LEN); 77 BN_bn2bin(sig->r, sigblob+ SIGBLOB_LEN - INTBLOB_LEN - rlen); 78 BN_bn2bin(sig->s, sigblob+ SIGBLOB_LEN - slen); 79 DSA_SIG_free(sig); 80 81 if (datafellows & SSH_BUG_SIGBLOB) { 82 if (lenp != NULL) 83 *lenp = SIGBLOB_LEN; 84 if (sigp != NULL) { 85 *sigp = xmalloc(SIGBLOB_LEN); 86 memcpy(*sigp, sigblob, SIGBLOB_LEN); 87 } 88 } else { 89 /* ietf-drafts */ 90 buffer_init(&b); 91 buffer_put_cstring(&b, "ssh-dss"); 92 buffer_put_string(&b, sigblob, SIGBLOB_LEN); 93 len = buffer_len(&b); 94 if (lenp != NULL) 95 *lenp = len; 96 if (sigp != NULL) { 97 *sigp = xmalloc(len); 98 memcpy(*sigp, buffer_ptr(&b), len); 99 } 100 buffer_free(&b); 101 } 102 return 0; 103 } 104 int 105 ssh_dss_verify(Key *key, u_char *signature, u_int signaturelen, 106 u_char *data, u_int datalen) 107 { 108 DSA_SIG *sig; 109 const EVP_MD *evp_md = EVP_sha1(); 110 EVP_MD_CTX md; 111 u_char digest[EVP_MAX_MD_SIZE], *sigblob; 112 u_int len, dlen; 113 int rlen, ret; 114 Buffer b; 115 116 if (key == NULL || key->type != KEY_DSA || key->dsa == NULL) { 117 error("ssh_dss_verify: no DSA key"); 118 return -1; 119 } 120 121 /* fetch signature */ 122 if (datafellows & SSH_BUG_SIGBLOB) { 123 sigblob = signature; 124 len = signaturelen; 125 } else { 126 /* ietf-drafts */ 127 char *ktype; 128 buffer_init(&b); 129 buffer_append(&b, signature, signaturelen); 130 ktype = buffer_get_string(&b, NULL); 131 if (strcmp("ssh-dss", ktype) != 0) { 132 error("ssh_dss_verify: cannot handle type %s", ktype); 133 buffer_free(&b); 134 xfree(ktype); 135 return -1; 136 } 137 xfree(ktype); 138 sigblob = buffer_get_string(&b, &len); 139 rlen = buffer_len(&b); 140 buffer_free(&b); 141 if (rlen != 0) { 142 error("ssh_dss_verify: " 143 "remaining bytes in signature %d", rlen); 144 xfree(sigblob); 145 return -1; 146 } 147 } 148 149 if (len != SIGBLOB_LEN) { 150 fatal("bad sigbloblen %u != SIGBLOB_LEN", len); 151 } 152 153 /* parse signature */ 154 if ((sig = DSA_SIG_new()) == NULL) 155 fatal("ssh_dss_verify: DSA_SIG_new failed"); 156 if ((sig->r = BN_new()) == NULL) 157 fatal("ssh_dss_verify: BN_new failed"); 158 if ((sig->s = BN_new()) == NULL) 159 fatal("ssh_dss_verify: BN_new failed"); 160 BN_bin2bn(sigblob, INTBLOB_LEN, sig->r); 161 BN_bin2bn(sigblob+ INTBLOB_LEN, INTBLOB_LEN, sig->s); 162 163 if (!(datafellows & SSH_BUG_SIGBLOB)) { 164 memset(sigblob, 0, len); 165 xfree(sigblob); 166 } 167 168 /* sha1 the data */ 169 EVP_DigestInit(&md, evp_md); 170 EVP_DigestUpdate(&md, data, datalen); 171 EVP_DigestFinal(&md, digest, &dlen); 172 173 ret = DSA_do_verify(digest, dlen, sig, key->dsa); 174 memset(digest, 'd', sizeof(digest)); 175 176 DSA_SIG_free(sig); 177 178 debug("ssh_dss_verify: signature %s", 179 ret == 1 ? "correct" : ret == 0 ? "incorrect" : "error"); 180 return ret; 181 } 182