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 1.19 2003/11/10 16:23:41 jakob 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 38 #define INTBLOB_LEN 20 39 #define SIGBLOB_LEN (2*INTBLOB_LEN) 40 41 int 42 ssh_dss_sign(const Key *key, u_char **sigp, u_int *lenp, 43 const u_char *data, u_int datalen) 44 { 45 DSA_SIG *sig; 46 const EVP_MD *evp_md = EVP_sha1(); 47 EVP_MD_CTX md; 48 u_char digest[EVP_MAX_MD_SIZE], sigblob[SIGBLOB_LEN]; 49 u_int rlen, slen, len, dlen; 50 Buffer b; 51 52 if (key == NULL || key->type != KEY_DSA || key->dsa == NULL) { 53 error("ssh_dss_sign: no DSA key"); 54 return -1; 55 } 56 EVP_DigestInit(&md, evp_md); 57 EVP_DigestUpdate(&md, data, datalen); 58 EVP_DigestFinal(&md, digest, &dlen); 59 60 sig = DSA_do_sign(digest, dlen, key->dsa); 61 memset(digest, 'd', sizeof(digest)); 62 63 if (sig == NULL) { 64 error("ssh_dss_sign: sign failed"); 65 return -1; 66 } 67 68 rlen = BN_num_bytes(sig->r); 69 slen = BN_num_bytes(sig->s); 70 if (rlen > INTBLOB_LEN || slen > INTBLOB_LEN) { 71 error("bad sig size %u %u", rlen, slen); 72 DSA_SIG_free(sig); 73 return -1; 74 } 75 memset(sigblob, 0, SIGBLOB_LEN); 76 BN_bn2bin(sig->r, sigblob+ SIGBLOB_LEN - INTBLOB_LEN - rlen); 77 BN_bn2bin(sig->s, sigblob+ SIGBLOB_LEN - slen); 78 DSA_SIG_free(sig); 79 80 if (datafellows & SSH_BUG_SIGBLOB) { 81 if (lenp != NULL) 82 *lenp = SIGBLOB_LEN; 83 if (sigp != NULL) { 84 *sigp = xmalloc(SIGBLOB_LEN); 85 memcpy(*sigp, sigblob, SIGBLOB_LEN); 86 } 87 } else { 88 /* ietf-drafts */ 89 buffer_init(&b); 90 buffer_put_cstring(&b, "ssh-dss"); 91 buffer_put_string(&b, sigblob, SIGBLOB_LEN); 92 len = buffer_len(&b); 93 if (lenp != NULL) 94 *lenp = len; 95 if (sigp != NULL) { 96 *sigp = xmalloc(len); 97 memcpy(*sigp, buffer_ptr(&b), len); 98 } 99 buffer_free(&b); 100 } 101 return 0; 102 } 103 int 104 ssh_dss_verify(const Key *key, const u_char *signature, u_int signaturelen, 105 const u_char *data, u_int datalen) 106 { 107 DSA_SIG *sig; 108 const EVP_MD *evp_md = EVP_sha1(); 109 EVP_MD_CTX md; 110 u_char digest[EVP_MAX_MD_SIZE], *sigblob; 111 u_int len, dlen; 112 int rlen, ret; 113 Buffer b; 114 115 if (key == NULL || key->type != KEY_DSA || key->dsa == NULL) { 116 error("ssh_dss_verify: no DSA key"); 117 return -1; 118 } 119 120 /* fetch signature */ 121 if (datafellows & SSH_BUG_SIGBLOB) { 122 sigblob = xmalloc(signaturelen); 123 memcpy(sigblob, signature, signaturelen); 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 /* clean up */ 164 memset(sigblob, 0, len); 165 xfree(sigblob); 166 167 /* sha1 the data */ 168 EVP_DigestInit(&md, evp_md); 169 EVP_DigestUpdate(&md, data, datalen); 170 EVP_DigestFinal(&md, digest, &dlen); 171 172 ret = DSA_do_verify(digest, dlen, sig, key->dsa); 173 memset(digest, 'd', sizeof(digest)); 174 175 DSA_SIG_free(sig); 176 177 debug("ssh_dss_verify: signature %s", 178 ret == 1 ? "correct" : ret == 0 ? "incorrect" : "error"); 179 return ret; 180 } 181