ssh-dss.c revision 162852
1162852Sdes/* $OpenBSD: ssh-dss.c,v 1.23 2006/08/03 03:34:42 deraadt Exp $ */ 276259Sgreen/* 376259Sgreen * Copyright (c) 2000 Markus Friedl. All rights reserved. 476259Sgreen * 576259Sgreen * Redistribution and use in source and binary forms, with or without 676259Sgreen * modification, are permitted provided that the following conditions 776259Sgreen * are met: 876259Sgreen * 1. Redistributions of source code must retain the above copyright 976259Sgreen * notice, this list of conditions and the following disclaimer. 1076259Sgreen * 2. Redistributions in binary form must reproduce the above copyright 1176259Sgreen * notice, this list of conditions and the following disclaimer in the 1276259Sgreen * documentation and/or other materials provided with the distribution. 1376259Sgreen * 1476259Sgreen * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR 1576259Sgreen * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES 1676259Sgreen * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. 1776259Sgreen * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, 1876259Sgreen * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT 1976259Sgreen * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, 2076259Sgreen * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY 2176259Sgreen * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT 2276259Sgreen * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF 2376259Sgreen * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 2476259Sgreen */ 2576259Sgreen 2676259Sgreen#include "includes.h" 2776259Sgreen 28162852Sdes#include <sys/types.h> 29162852Sdes 3076259Sgreen#include <openssl/bn.h> 3176259Sgreen#include <openssl/evp.h> 3276259Sgreen 33162852Sdes#include <stdarg.h> 34162852Sdes#include <string.h> 35162852Sdes 3676259Sgreen#include "xmalloc.h" 3776259Sgreen#include "buffer.h" 3876259Sgreen#include "compat.h" 3976259Sgreen#include "log.h" 4076259Sgreen#include "key.h" 4176259Sgreen 4276259Sgreen#define INTBLOB_LEN 20 4376259Sgreen#define SIGBLOB_LEN (2*INTBLOB_LEN) 4476259Sgreen 4576259Sgreenint 46126274Sdesssh_dss_sign(const Key *key, u_char **sigp, u_int *lenp, 47126274Sdes const u_char *data, u_int datalen) 4876259Sgreen{ 4976259Sgreen DSA_SIG *sig; 5092555Sdes const EVP_MD *evp_md = EVP_sha1(); 5176259Sgreen EVP_MD_CTX md; 52106121Sdes u_char digest[EVP_MAX_MD_SIZE], sigblob[SIGBLOB_LEN]; 5392555Sdes u_int rlen, slen, len, dlen; 5476259Sgreen Buffer b; 5576259Sgreen 5676259Sgreen if (key == NULL || key->type != KEY_DSA || key->dsa == NULL) { 5776259Sgreen error("ssh_dss_sign: no DSA key"); 5876259Sgreen return -1; 5976259Sgreen } 6076259Sgreen EVP_DigestInit(&md, evp_md); 6176259Sgreen EVP_DigestUpdate(&md, data, datalen); 6292555Sdes EVP_DigestFinal(&md, digest, &dlen); 6376259Sgreen 6476259Sgreen sig = DSA_do_sign(digest, dlen, key->dsa); 6592555Sdes memset(digest, 'd', sizeof(digest)); 6692555Sdes 6776259Sgreen if (sig == NULL) { 6892555Sdes error("ssh_dss_sign: sign failed"); 6992555Sdes return -1; 7076259Sgreen } 7176259Sgreen 7276259Sgreen rlen = BN_num_bytes(sig->r); 7376259Sgreen slen = BN_num_bytes(sig->s); 7476259Sgreen if (rlen > INTBLOB_LEN || slen > INTBLOB_LEN) { 7599060Sdes error("bad sig size %u %u", rlen, slen); 7676259Sgreen DSA_SIG_free(sig); 7776259Sgreen return -1; 7876259Sgreen } 7976259Sgreen memset(sigblob, 0, SIGBLOB_LEN); 8076259Sgreen BN_bn2bin(sig->r, sigblob+ SIGBLOB_LEN - INTBLOB_LEN - rlen); 8176259Sgreen BN_bn2bin(sig->s, sigblob+ SIGBLOB_LEN - slen); 8276259Sgreen DSA_SIG_free(sig); 8376259Sgreen 8476259Sgreen if (datafellows & SSH_BUG_SIGBLOB) { 8576259Sgreen if (lenp != NULL) 8676259Sgreen *lenp = SIGBLOB_LEN; 87106121Sdes if (sigp != NULL) { 88106121Sdes *sigp = xmalloc(SIGBLOB_LEN); 89106121Sdes memcpy(*sigp, sigblob, SIGBLOB_LEN); 90106121Sdes } 9176259Sgreen } else { 9276259Sgreen /* ietf-drafts */ 9376259Sgreen buffer_init(&b); 9476259Sgreen buffer_put_cstring(&b, "ssh-dss"); 9576259Sgreen buffer_put_string(&b, sigblob, SIGBLOB_LEN); 9676259Sgreen len = buffer_len(&b); 9776259Sgreen if (lenp != NULL) 9876259Sgreen *lenp = len; 99106121Sdes if (sigp != NULL) { 100106121Sdes *sigp = xmalloc(len); 101106121Sdes memcpy(*sigp, buffer_ptr(&b), len); 102106121Sdes } 103106121Sdes buffer_free(&b); 10476259Sgreen } 10576259Sgreen return 0; 10676259Sgreen} 10776259Sgreenint 108126274Sdesssh_dss_verify(const Key *key, const u_char *signature, u_int signaturelen, 109126274Sdes const u_char *data, u_int datalen) 11076259Sgreen{ 11176259Sgreen DSA_SIG *sig; 11292555Sdes const EVP_MD *evp_md = EVP_sha1(); 11376259Sgreen EVP_MD_CTX md; 11492555Sdes u_char digest[EVP_MAX_MD_SIZE], *sigblob; 11576259Sgreen u_int len, dlen; 11692555Sdes int rlen, ret; 11792555Sdes Buffer b; 11876259Sgreen 11976259Sgreen if (key == NULL || key->type != KEY_DSA || key->dsa == NULL) { 12076259Sgreen error("ssh_dss_verify: no DSA key"); 12176259Sgreen return -1; 12276259Sgreen } 12376259Sgreen 12476259Sgreen /* fetch signature */ 12576259Sgreen if (datafellows & SSH_BUG_SIGBLOB) { 126126274Sdes sigblob = xmalloc(signaturelen); 127126274Sdes memcpy(sigblob, signature, signaturelen); 12876259Sgreen len = signaturelen; 12976259Sgreen } else { 13076259Sgreen /* ietf-drafts */ 13176259Sgreen char *ktype; 13276259Sgreen buffer_init(&b); 13392555Sdes buffer_append(&b, signature, signaturelen); 13476259Sgreen ktype = buffer_get_string(&b, NULL); 13576259Sgreen if (strcmp("ssh-dss", ktype) != 0) { 13676259Sgreen error("ssh_dss_verify: cannot handle type %s", ktype); 13776259Sgreen buffer_free(&b); 13892555Sdes xfree(ktype); 13976259Sgreen return -1; 14076259Sgreen } 14192555Sdes xfree(ktype); 14292555Sdes sigblob = buffer_get_string(&b, &len); 14376259Sgreen rlen = buffer_len(&b); 14492555Sdes buffer_free(&b); 14592555Sdes if (rlen != 0) { 14692555Sdes error("ssh_dss_verify: " 14792555Sdes "remaining bytes in signature %d", rlen); 14892555Sdes xfree(sigblob); 14976259Sgreen return -1; 15076259Sgreen } 15176259Sgreen } 15276259Sgreen 15376259Sgreen if (len != SIGBLOB_LEN) { 15499060Sdes fatal("bad sigbloblen %u != SIGBLOB_LEN", len); 15576259Sgreen } 15676259Sgreen 15776259Sgreen /* parse signature */ 15892555Sdes if ((sig = DSA_SIG_new()) == NULL) 15992555Sdes fatal("ssh_dss_verify: DSA_SIG_new failed"); 16092555Sdes if ((sig->r = BN_new()) == NULL) 16192555Sdes fatal("ssh_dss_verify: BN_new failed"); 16292555Sdes if ((sig->s = BN_new()) == NULL) 16392555Sdes fatal("ssh_dss_verify: BN_new failed"); 16476259Sgreen BN_bin2bn(sigblob, INTBLOB_LEN, sig->r); 16576259Sgreen BN_bin2bn(sigblob+ INTBLOB_LEN, INTBLOB_LEN, sig->s); 16676259Sgreen 167126274Sdes /* clean up */ 168126274Sdes memset(sigblob, 0, len); 169126274Sdes xfree(sigblob); 17076259Sgreen 17176259Sgreen /* sha1 the data */ 17276259Sgreen EVP_DigestInit(&md, evp_md); 17376259Sgreen EVP_DigestUpdate(&md, data, datalen); 17492555Sdes EVP_DigestFinal(&md, digest, &dlen); 17576259Sgreen 17676259Sgreen ret = DSA_do_verify(digest, dlen, sig, key->dsa); 17792555Sdes memset(digest, 'd', sizeof(digest)); 17876259Sgreen 17976259Sgreen DSA_SIG_free(sig); 18076259Sgreen 18192555Sdes debug("ssh_dss_verify: signature %s", 18292555Sdes ret == 1 ? "correct" : ret == 0 ? "incorrect" : "error"); 18376259Sgreen return ret; 18476259Sgreen} 185