ssh-dss.c revision 255767
1275970Scy/* $OpenBSD: ssh-dss.c,v 1.28 2013/05/17 00:13:14 djm Exp $ */ 2275970Scy/* 3275970Scy * Copyright (c) 2000 Markus Friedl. All rights reserved. 4275970Scy * 5275970Scy * Redistribution and use in source and binary forms, with or without 6275970Scy * modification, are permitted provided that the following conditions 7275970Scy * are met: 8275970Scy * 1. Redistributions of source code must retain the above copyright 9275970Scy * notice, this list of conditions and the following disclaimer. 10275970Scy * 2. Redistributions in binary form must reproduce the above copyright 11275970Scy * notice, this list of conditions and the following disclaimer in the 12275970Scy * documentation and/or other materials provided with the distribution. 13275970Scy * 14275970Scy * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR 15275970Scy * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES 16275970Scy * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. 17275970Scy * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, 18275970Scy * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT 19275970Scy * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, 20275970Scy * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY 21275970Scy * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT 22275970Scy * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF 23275970Scy * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 24275970Scy */ 25275970Scy 26275970Scy#include "includes.h" 27275970Scy 28275970Scy#include <sys/types.h> 29275970Scy 30275970Scy#include <openssl/bn.h> 31275970Scy#include <openssl/evp.h> 32275970Scy 33275970Scy#include <stdarg.h> 34275970Scy#include <string.h> 35275970Scy 36275970Scy#include "xmalloc.h" 37275970Scy#include "buffer.h" 38275970Scy#include "compat.h" 39275970Scy#include "log.h" 40275970Scy#include "key.h" 41275970Scy 42275970Scy#define INTBLOB_LEN 20 43275970Scy#define SIGBLOB_LEN (2*INTBLOB_LEN) 44275970Scy 45275970Scyint 46275970Scyssh_dss_sign(const Key *key, u_char **sigp, u_int *lenp, 47275970Scy const u_char *data, u_int datalen) 48275970Scy{ 49275970Scy DSA_SIG *sig; 50275970Scy const EVP_MD *evp_md = EVP_sha1(); 51275970Scy EVP_MD_CTX md; 52275970Scy u_char digest[EVP_MAX_MD_SIZE], sigblob[SIGBLOB_LEN]; 53275970Scy u_int rlen, slen, len, dlen; 54275970Scy Buffer b; 55275970Scy 56275970Scy if (key == NULL || key->dsa == NULL || (key->type != KEY_DSA && 57275970Scy key->type != KEY_DSA_CERT && key->type != KEY_DSA_CERT_V00)) { 58275970Scy error("ssh_dss_sign: no DSA key"); 59275970Scy return -1; 60275970Scy } 61275970Scy EVP_DigestInit(&md, evp_md); 62275970Scy EVP_DigestUpdate(&md, data, datalen); 63275970Scy EVP_DigestFinal(&md, digest, &dlen); 64275970Scy 65275970Scy sig = DSA_do_sign(digest, dlen, key->dsa); 66275970Scy memset(digest, 'd', sizeof(digest)); 67275970Scy 68275970Scy if (sig == NULL) { 69275970Scy error("ssh_dss_sign: sign failed"); 70275970Scy return -1; 71275970Scy } 72275970Scy 73275970Scy rlen = BN_num_bytes(sig->r); 74275970Scy slen = BN_num_bytes(sig->s); 75275970Scy if (rlen > INTBLOB_LEN || slen > INTBLOB_LEN) { 76275970Scy error("bad sig size %u %u", rlen, slen); 77275970Scy DSA_SIG_free(sig); 78275970Scy return -1; 79275970Scy } 80275970Scy memset(sigblob, 0, SIGBLOB_LEN); 81275970Scy BN_bn2bin(sig->r, sigblob+ SIGBLOB_LEN - INTBLOB_LEN - rlen); 82275970Scy BN_bn2bin(sig->s, sigblob+ SIGBLOB_LEN - slen); 83275970Scy DSA_SIG_free(sig); 84275970Scy 85275970Scy if (datafellows & SSH_BUG_SIGBLOB) { 86275970Scy if (lenp != NULL) 87275970Scy *lenp = SIGBLOB_LEN; 88275970Scy if (sigp != NULL) { 89275970Scy *sigp = xmalloc(SIGBLOB_LEN); 90275970Scy memcpy(*sigp, sigblob, SIGBLOB_LEN); 91275970Scy } 92275970Scy } else { 93275970Scy /* ietf-drafts */ 94275970Scy buffer_init(&b); 95275970Scy buffer_put_cstring(&b, "ssh-dss"); 96275970Scy buffer_put_string(&b, sigblob, SIGBLOB_LEN); 97275970Scy len = buffer_len(&b); 98275970Scy if (lenp != NULL) 99275970Scy *lenp = len; 100275970Scy if (sigp != NULL) { 101275970Scy *sigp = xmalloc(len); 102275970Scy memcpy(*sigp, buffer_ptr(&b), len); 103275970Scy } 104275970Scy buffer_free(&b); 105275970Scy } 106275970Scy return 0; 107275970Scy} 108275970Scyint 109275970Scyssh_dss_verify(const Key *key, const u_char *signature, u_int signaturelen, 110275970Scy const u_char *data, u_int datalen) 111275970Scy{ 112275970Scy DSA_SIG *sig; 113275970Scy const EVP_MD *evp_md = EVP_sha1(); 114275970Scy EVP_MD_CTX md; 115275970Scy u_char digest[EVP_MAX_MD_SIZE], *sigblob; 116275970Scy u_int len, dlen; 117275970Scy int rlen, ret; 118 Buffer b; 119 120 if (key == NULL || key->dsa == NULL || (key->type != KEY_DSA && 121 key->type != KEY_DSA_CERT && key->type != KEY_DSA_CERT_V00)) { 122 error("ssh_dss_verify: no DSA key"); 123 return -1; 124 } 125 126 /* fetch signature */ 127 if (datafellows & SSH_BUG_SIGBLOB) { 128 sigblob = xmalloc(signaturelen); 129 memcpy(sigblob, signature, signaturelen); 130 len = signaturelen; 131 } else { 132 /* ietf-drafts */ 133 char *ktype; 134 buffer_init(&b); 135 buffer_append(&b, signature, signaturelen); 136 ktype = buffer_get_cstring(&b, NULL); 137 if (strcmp("ssh-dss", ktype) != 0) { 138 error("ssh_dss_verify: cannot handle type %s", ktype); 139 buffer_free(&b); 140 free(ktype); 141 return -1; 142 } 143 free(ktype); 144 sigblob = buffer_get_string(&b, &len); 145 rlen = buffer_len(&b); 146 buffer_free(&b); 147 if (rlen != 0) { 148 error("ssh_dss_verify: " 149 "remaining bytes in signature %d", rlen); 150 free(sigblob); 151 return -1; 152 } 153 } 154 155 if (len != SIGBLOB_LEN) { 156 fatal("bad sigbloblen %u != SIGBLOB_LEN", len); 157 } 158 159 /* parse signature */ 160 if ((sig = DSA_SIG_new()) == NULL) 161 fatal("ssh_dss_verify: DSA_SIG_new failed"); 162 if ((sig->r = BN_new()) == NULL) 163 fatal("ssh_dss_verify: BN_new failed"); 164 if ((sig->s = BN_new()) == NULL) 165 fatal("ssh_dss_verify: BN_new failed"); 166 if ((BN_bin2bn(sigblob, INTBLOB_LEN, sig->r) == NULL) || 167 (BN_bin2bn(sigblob+ INTBLOB_LEN, INTBLOB_LEN, sig->s) == NULL)) 168 fatal("ssh_dss_verify: BN_bin2bn failed"); 169 170 /* clean up */ 171 memset(sigblob, 0, len); 172 free(sigblob); 173 174 /* sha1 the data */ 175 EVP_DigestInit(&md, evp_md); 176 EVP_DigestUpdate(&md, data, datalen); 177 EVP_DigestFinal(&md, digest, &dlen); 178 179 ret = DSA_do_verify(digest, dlen, sig, key->dsa); 180 memset(digest, 'd', sizeof(digest)); 181 182 DSA_SIG_free(sig); 183 184 debug("ssh_dss_verify: signature %s", 185 ret == 1 ? "correct" : ret == 0 ? "incorrect" : "error"); 186 return ret; 187} 188