ssh-dss.c revision 164146
1/* $OpenBSD: ssh-dss.c,v 1.24 2006/11/06 21:25:28 markus Exp $ */ 2/* 3 * Copyright (c) 2000 Markus Friedl. All rights reserved. 4 * 5 * Redistribution and use in source and binary forms, with or without 6 * modification, are permitted provided that the following conditions 7 * are met: 8 * 1. Redistributions of source code must retain the above copyright 9 * notice, this list of conditions and the following disclaimer. 10 * 2. Redistributions in binary form must reproduce the above copyright 11 * notice, this list of conditions and the following disclaimer in the 12 * documentation and/or other materials provided with the distribution. 13 * 14 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR 15 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES 16 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. 17 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, 18 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT 19 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, 20 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY 21 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT 22 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF 23 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 24 */ 25 26#include "includes.h" 27 28#include <sys/types.h> 29 30#include <openssl/bn.h> 31#include <openssl/evp.h> 32 33#include <stdarg.h> 34#include <string.h> 35 36#include "xmalloc.h" 37#include "buffer.h" 38#include "compat.h" 39#include "log.h" 40#include "key.h" 41 42#define INTBLOB_LEN 20 43#define SIGBLOB_LEN (2*INTBLOB_LEN) 44 45int 46ssh_dss_sign(const Key *key, u_char **sigp, u_int *lenp, 47 const u_char *data, u_int datalen) 48{ 49 DSA_SIG *sig; 50 const EVP_MD *evp_md = EVP_sha1(); 51 EVP_MD_CTX md; 52 u_char digest[EVP_MAX_MD_SIZE], sigblob[SIGBLOB_LEN]; 53 u_int rlen, slen, len, dlen; 54 Buffer b; 55 56 if (key == NULL || key->type != KEY_DSA || key->dsa == NULL) { 57 error("ssh_dss_sign: no DSA key"); 58 return -1; 59 } 60 EVP_DigestInit(&md, evp_md); 61 EVP_DigestUpdate(&md, data, datalen); 62 EVP_DigestFinal(&md, digest, &dlen); 63 64 sig = DSA_do_sign(digest, dlen, key->dsa); 65 memset(digest, 'd', sizeof(digest)); 66 67 if (sig == NULL) { 68 error("ssh_dss_sign: sign failed"); 69 return -1; 70 } 71 72 rlen = BN_num_bytes(sig->r); 73 slen = BN_num_bytes(sig->s); 74 if (rlen > INTBLOB_LEN || slen > INTBLOB_LEN) { 75 error("bad sig size %u %u", rlen, slen); 76 DSA_SIG_free(sig); 77 return -1; 78 } 79 memset(sigblob, 0, SIGBLOB_LEN); 80 BN_bn2bin(sig->r, sigblob+ SIGBLOB_LEN - INTBLOB_LEN - rlen); 81 BN_bn2bin(sig->s, sigblob+ SIGBLOB_LEN - slen); 82 DSA_SIG_free(sig); 83 84 if (datafellows & SSH_BUG_SIGBLOB) { 85 if (lenp != NULL) 86 *lenp = SIGBLOB_LEN; 87 if (sigp != NULL) { 88 *sigp = xmalloc(SIGBLOB_LEN); 89 memcpy(*sigp, sigblob, SIGBLOB_LEN); 90 } 91 } else { 92 /* ietf-drafts */ 93 buffer_init(&b); 94 buffer_put_cstring(&b, "ssh-dss"); 95 buffer_put_string(&b, sigblob, SIGBLOB_LEN); 96 len = buffer_len(&b); 97 if (lenp != NULL) 98 *lenp = len; 99 if (sigp != NULL) { 100 *sigp = xmalloc(len); 101 memcpy(*sigp, buffer_ptr(&b), len); 102 } 103 buffer_free(&b); 104 } 105 return 0; 106} 107int 108ssh_dss_verify(const Key *key, const u_char *signature, u_int signaturelen, 109 const u_char *data, u_int datalen) 110{ 111 DSA_SIG *sig; 112 const EVP_MD *evp_md = EVP_sha1(); 113 EVP_MD_CTX md; 114 u_char digest[EVP_MAX_MD_SIZE], *sigblob; 115 u_int len, dlen; 116 int rlen, ret; 117 Buffer b; 118 119 if (key == NULL || key->type != KEY_DSA || key->dsa == NULL) { 120 error("ssh_dss_verify: no DSA key"); 121 return -1; 122 } 123 124 /* fetch signature */ 125 if (datafellows & SSH_BUG_SIGBLOB) { 126 sigblob = xmalloc(signaturelen); 127 memcpy(sigblob, signature, signaturelen); 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 %u != 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 if ((BN_bin2bn(sigblob, INTBLOB_LEN, sig->r) == NULL) || 165 (BN_bin2bn(sigblob+ INTBLOB_LEN, INTBLOB_LEN, sig->s) == NULL)) 166 fatal("ssh_dss_verify: BN_bin2bn failed"); 167 168 /* clean up */ 169 memset(sigblob, 0, len); 170 xfree(sigblob); 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