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 #pragma ident "%Z%%M% %I% %E% SMI" 29 30 #include <openssl/bn.h> 31 #include <openssl/evp.h> 32 33 #include "xmalloc.h" 34 #include "buffer.h" 35 #include "bufaux.h" 36 #include "compat.h" 37 #include "log.h" 38 #include "key.h" 39 #include "ssh-dss.h" 40 41 #define INTBLOB_LEN 20 42 #define SIGBLOB_LEN (2*INTBLOB_LEN) 43 44 int 45 ssh_dss_sign(Key *key, u_char **sigp, u_int *lenp, 46 u_char *data, u_int datalen) 47 { 48 DSA_SIG *sig; 49 const EVP_MD *evp_md = EVP_sha1(); 50 EVP_MD_CTX md; 51 u_char digest[EVP_MAX_MD_SIZE], 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 EVP_DigestInit(&md, evp_md); 60 EVP_DigestUpdate(&md, data, datalen); 61 EVP_DigestFinal(&md, digest, &dlen); 62 63 sig = DSA_do_sign(digest, dlen, key->dsa); 64 memset(digest, 'd', sizeof(digest)); 65 66 if (sig == NULL) { 67 error("ssh_dss_sign: sign failed"); 68 return -1; 69 } 70 71 rlen = BN_num_bytes(sig->r); 72 slen = BN_num_bytes(sig->s); 73 if (rlen > INTBLOB_LEN || slen > INTBLOB_LEN) { 74 error("bad sig size %u %u", rlen, slen); 75 DSA_SIG_free(sig); 76 return -1; 77 } 78 memset(sigblob, 0, SIGBLOB_LEN); 79 BN_bn2bin(sig->r, sigblob+ SIGBLOB_LEN - INTBLOB_LEN - rlen); 80 BN_bn2bin(sig->s, sigblob+ SIGBLOB_LEN - slen); 81 DSA_SIG_free(sig); 82 83 if (datafellows & SSH_BUG_SIGBLOB) { 84 if (lenp != NULL) 85 *lenp = SIGBLOB_LEN; 86 if (sigp != NULL) { 87 *sigp = xmalloc(SIGBLOB_LEN); 88 memcpy(*sigp, sigblob, SIGBLOB_LEN); 89 } 90 } else { 91 /* ietf-drafts */ 92 buffer_init(&b); 93 buffer_put_cstring(&b, "ssh-dss"); 94 buffer_put_string(&b, sigblob, SIGBLOB_LEN); 95 len = buffer_len(&b); 96 if (lenp != NULL) 97 *lenp = len; 98 if (sigp != NULL) { 99 *sigp = xmalloc(len); 100 memcpy(*sigp, buffer_ptr(&b), len); 101 } 102 buffer_free(&b); 103 } 104 return 0; 105 } 106 int 107 ssh_dss_verify(Key *key, u_char *signature, u_int signaturelen, 108 u_char *data, u_int datalen) 109 { 110 DSA_SIG *sig; 111 const EVP_MD *evp_md = EVP_sha1(); 112 EVP_MD_CTX md; 113 u_char digest[EVP_MAX_MD_SIZE], *sigblob; 114 u_int len, dlen; 115 int rlen, ret; 116 Buffer b; 117 118 if (key == NULL || key->type != KEY_DSA || key->dsa == NULL) { 119 error("ssh_dss_verify: no DSA key"); 120 return -1; 121 } 122 123 /* fetch signature */ 124 if (datafellows & SSH_BUG_SIGBLOB) { 125 sigblob = signature; 126 len = signaturelen; 127 } else { 128 /* ietf-drafts */ 129 char *ktype; 130 buffer_init(&b); 131 buffer_append(&b, signature, signaturelen); 132 ktype = buffer_get_string(&b, NULL); 133 if (strcmp("ssh-dss", ktype) != 0) { 134 error("ssh_dss_verify: cannot handle type %s", ktype); 135 buffer_free(&b); 136 xfree(ktype); 137 return -1; 138 } 139 xfree(ktype); 140 sigblob = buffer_get_string(&b, &len); 141 rlen = buffer_len(&b); 142 buffer_free(&b); 143 if (rlen != 0) { 144 error("ssh_dss_verify: " 145 "remaining bytes in signature %d", rlen); 146 xfree(sigblob); 147 return -1; 148 } 149 } 150 151 if (len != SIGBLOB_LEN) { 152 fatal("bad sigbloblen %u != SIGBLOB_LEN", len); 153 } 154 155 /* parse signature */ 156 if ((sig = DSA_SIG_new()) == NULL) 157 fatal("ssh_dss_verify: DSA_SIG_new failed"); 158 if ((sig->r = BN_new()) == NULL) 159 fatal("ssh_dss_verify: BN_new failed"); 160 if ((sig->s = BN_new()) == NULL) 161 fatal("ssh_dss_verify: BN_new failed"); 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 EVP_DigestInit(&md, evp_md); 172 EVP_DigestUpdate(&md, data, datalen); 173 EVP_DigestFinal(&md, digest, &dlen); 174 175 ret = DSA_do_verify(digest, dlen, sig, key->dsa); 176 memset(digest, 'd', sizeof(digest)); 177 178 DSA_SIG_free(sig); 179 180 debug("ssh_dss_verify: signature %s", 181 ret == 1 ? "correct" : ret == 0 ? "incorrect" : "error"); 182 return ret; 183 } 184