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 1.14 2002/02/28 15:46:33 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( 44 Key *key, 45 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 *ret, 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 %d %d", 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 ret = xmalloc(SIGBLOB_LEN); 85 memcpy(ret, sigblob, SIGBLOB_LEN); 86 if (lenp != NULL) 87 *lenp = SIGBLOB_LEN; 88 if (sigp != NULL) 89 *sigp = ret; 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 ret = xmalloc(len); 97 memcpy(ret, buffer_ptr(&b), len); 98 buffer_free(&b); 99 if (lenp != NULL) 100 *lenp = len; 101 if (sigp != NULL) 102 *sigp = ret; 103 } 104 return 0; 105 } 106 int 107 ssh_dss_verify( 108 Key *key, 109 u_char *signature, u_int signaturelen, 110 u_char *data, u_int datalen) 111 { 112 DSA_SIG *sig; 113 const EVP_MD *evp_md = EVP_sha1(); 114 EVP_MD_CTX md; 115 u_char digest[EVP_MAX_MD_SIZE], *sigblob; 116 u_int len, dlen; 117 int rlen, ret; 118 Buffer b; 119 120 if (key == NULL || key->type != KEY_DSA || key->dsa == NULL) { 121 error("ssh_dss_verify: no DSA key"); 122 return -1; 123 } 124 125 /* fetch signature */ 126 if (datafellows & SSH_BUG_SIGBLOB) { 127 sigblob = signature; 128 len = signaturelen; 129 } else { 130 /* ietf-drafts */ 131 char *ktype; 132 buffer_init(&b); 133 buffer_append(&b, signature, signaturelen); 134 ktype = buffer_get_string(&b, NULL); 135 if (strcmp("ssh-dss", ktype) != 0) { 136 error("ssh_dss_verify: cannot handle type %s", ktype); 137 buffer_free(&b); 138 xfree(ktype); 139 return -1; 140 } 141 xfree(ktype); 142 sigblob = buffer_get_string(&b, &len); 143 rlen = buffer_len(&b); 144 buffer_free(&b); 145 if (rlen != 0) { 146 error("ssh_dss_verify: " 147 "remaining bytes in signature %d", rlen); 148 xfree(sigblob); 149 return -1; 150 } 151 } 152 153 if (len != SIGBLOB_LEN) { 154 fatal("bad sigbloblen %d != SIGBLOB_LEN", len); 155 } 156 157 /* parse signature */ 158 if ((sig = DSA_SIG_new()) == NULL) 159 fatal("ssh_dss_verify: DSA_SIG_new failed"); 160 if ((sig->r = BN_new()) == NULL) 161 fatal("ssh_dss_verify: BN_new failed"); 162 if ((sig->s = BN_new()) == NULL) 163 fatal("ssh_dss_verify: BN_new failed"); 164 BN_bin2bn(sigblob, INTBLOB_LEN, sig->r); 165 BN_bin2bn(sigblob+ INTBLOB_LEN, INTBLOB_LEN, sig->s); 166 167 if (!(datafellows & SSH_BUG_SIGBLOB)) { 168 memset(sigblob, 0, len); 169 xfree(sigblob); 170 } 171 172 /* sha1 the data */ 173 EVP_DigestInit(&md, evp_md); 174 EVP_DigestUpdate(&md, data, datalen); 175 EVP_DigestFinal(&md, digest, &dlen); 176 177 ret = DSA_do_verify(digest, dlen, sig, key->dsa); 178 memset(digest, 'd', sizeof(digest)); 179 180 DSA_SIG_free(sig); 181 182 debug("ssh_dss_verify: signature %s", 183 ret == 1 ? "correct" : ret == 0 ? "incorrect" : "error"); 184 return ret; 185 } 186