[openssh.git] / ssh-dss.c

/*
 * Copyright (c) 2000 Markus Friedl.  All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */

#include "includes.h"
RCSID("$OpenBSD: ssh-dss.c,v 1.6 2001/02/08 19:30:52 itojun Exp $");

#include <openssl/bn.h>
#include <openssl/evp.h>

#include "xmalloc.h"
#include "buffer.h"
#include "bufaux.h"
#include "compat.h"
#include "log.h"
#include "key.h"
#include "ssh-dss.h"

#define INTBLOB_LEN	20
#define SIGBLOB_LEN	(2*INTBLOB_LEN)

int
ssh_dss_sign(
    Key *key,
    u_char **sigp, int *lenp,
    u_char *data, int datalen)
{
	u_char *digest;
	u_char *ret;
	DSA_SIG *sig;
	EVP_MD *evp_md = EVP_sha1();
	EVP_MD_CTX md;
	u_int rlen;
	u_int slen;
	u_int len, dlen;
	u_char sigblob[SIGBLOB_LEN];
	Buffer b;

	if (key == NULL || key->type != KEY_DSA || key->dsa == NULL) {
		error("ssh_dss_sign: no DSA key");
		return -1;
	}
	dlen = evp_md->md_size;
	digest = xmalloc(dlen);
	EVP_DigestInit(&md, evp_md);
	EVP_DigestUpdate(&md, data, datalen);
	EVP_DigestFinal(&md, digest, NULL);

	sig = DSA_do_sign(digest, dlen, key->dsa);
	if (sig == NULL) {
		fatal("ssh_dss_sign: cannot sign");
	}
	memset(digest, 0, dlen);
	xfree(digest);

	rlen = BN_num_bytes(sig->r);
	slen = BN_num_bytes(sig->s);
	if (rlen > INTBLOB_LEN || slen > INTBLOB_LEN) {
		error("bad sig size %d %d", rlen, slen);
		DSA_SIG_free(sig);
		return -1;
	}
	debug("sig size %d %d", rlen, slen);

	memset(sigblob, 0, SIGBLOB_LEN);
	BN_bn2bin(sig->r, sigblob+ SIGBLOB_LEN - INTBLOB_LEN - rlen);
	BN_bn2bin(sig->s, sigblob+ SIGBLOB_LEN - slen);
	DSA_SIG_free(sig);

	if (datafellows & SSH_BUG_SIGBLOB) {
		debug("datafellows");
		ret = xmalloc(SIGBLOB_LEN);
		memcpy(ret, sigblob, SIGBLOB_LEN);
		if (lenp != NULL)
			*lenp = SIGBLOB_LEN;
		if (sigp != NULL)
			*sigp = ret;
	} else {
		/* ietf-drafts */
		buffer_init(&b);
		buffer_put_cstring(&b, "ssh-dss");
		buffer_put_string(&b, sigblob, SIGBLOB_LEN);
		len = buffer_len(&b);
		ret = xmalloc(len);
		memcpy(ret, buffer_ptr(&b), len);
		buffer_free(&b);
		if (lenp != NULL)
			*lenp = len;
		if (sigp != NULL)
			*sigp = ret;
	}
	return 0;
}
int
ssh_dss_verify(
    Key *key,
    u_char *signature, int signaturelen,
    u_char *data, int datalen)
{
	Buffer b;
	u_char *digest;
	DSA_SIG *sig;
	EVP_MD *evp_md = EVP_sha1();
	EVP_MD_CTX md;
	u_char *sigblob;
	char *txt;
	u_int len, dlen;
	int rlen;
	int ret;

	if (key == NULL || key->type != KEY_DSA || key->dsa == NULL) {
		error("ssh_dss_verify: no DSA key");
		return -1;
	}

	if (!(datafellows & SSH_BUG_SIGBLOB) &&
	    signaturelen == SIGBLOB_LEN) {
		datafellows |= ~SSH_BUG_SIGBLOB;
		log("autodetect SSH_BUG_SIGBLOB");
	} else if ((datafellows & SSH_BUG_SIGBLOB) &&
	    signaturelen != SIGBLOB_LEN) {
		log("autoremove SSH_BUG_SIGBLOB");
		datafellows &= ~SSH_BUG_SIGBLOB;
	}

	debug("len %d datafellows %d", signaturelen, datafellows);

	/* fetch signature */
	if (datafellows & SSH_BUG_SIGBLOB) {
		sigblob = signature;
		len = signaturelen;
	} else {
		/* ietf-drafts */
		char *ktype;
		buffer_init(&b);
		buffer_append(&b, (char *) signature, signaturelen);
		ktype = buffer_get_string(&b, NULL);
		if (strcmp("ssh-dss", ktype) != 0) {
			error("ssh_dss_verify: cannot handle type %s", ktype);
			buffer_free(&b);
			return -1;
		}
		sigblob = (u_char *)buffer_get_string(&b, &len);
		rlen = buffer_len(&b);
		if(rlen != 0) {
			error("remaining bytes in signature %d", rlen);
			buffer_free(&b);
			return -1;
		}
		buffer_free(&b);
		xfree(ktype);
	}

	if (len != SIGBLOB_LEN) {
		fatal("bad sigbloblen %d != SIGBLOB_LEN", len);
	}

	/* parse signature */
	sig = DSA_SIG_new();
	sig->r = BN_new();
	sig->s = BN_new();
	BN_bin2bn(sigblob, INTBLOB_LEN, sig->r);
	BN_bin2bn(sigblob+ INTBLOB_LEN, INTBLOB_LEN, sig->s);

	if (!(datafellows & SSH_BUG_SIGBLOB)) {
		memset(sigblob, 0, len);
		xfree(sigblob);
	}

	/* sha1 the data */
	dlen = evp_md->md_size;
	digest = xmalloc(dlen);
	EVP_DigestInit(&md, evp_md);
	EVP_DigestUpdate(&md, data, datalen);
	EVP_DigestFinal(&md, digest, NULL);

	ret = DSA_do_verify(digest, dlen, sig, key->dsa);

	memset(digest, 0, dlen);
	xfree(digest);
	DSA_SIG_free(sig);

	switch (ret) {
	case 1:
		txt = "correct";
		break;
	case 0:
		txt = "incorrect";
		break;
	case -1:
	default:
		txt = "error";
		break;
	}
	debug("ssh_dss_verify: signature %s", txt);
	return ret;
}
Commit	Line	Data
4f8c6159	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.
4f8c6159	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"
5ca51e19	26	RCSID("$OpenBSD: ssh-dss.c,v 1.6 2001/02/08 19:30:52 itojun Exp $");
42f11eb2	27
	28	#include <openssl/bn.h>
	29	#include <openssl/evp.h>
4f8c6159	30
4f8c6159	31	#include "xmalloc.h"
	32	#include "buffer.h"
	33	#include "bufaux.h"
	34	#include "compat.h"
42f11eb2	35	#include "log.h"
4f8c6159	36	#include "key.h"
5ca51e19	37	#include "ssh-dss.h"
4f8c6159	38
	39	#define INTBLOB_LEN 20
	40	#define SIGBLOB_LEN (2*INTBLOB_LEN)
	41
4f8c6159	42	int
fa08c86b	43	ssh_dss_sign(
4f8c6159	44	Key *key,
1e3b8b07	45	u_char *sigp, int lenp,
1e3b8b07	46	u_char *data, int datalen)
4f8c6159	47	{
1e3b8b07	48	u_char *digest;
1e3b8b07	49	u_char *ret;
4f8c6159	50	DSA_SIG *sig;
	51	EVP_MD *evp_md = EVP_sha1();
	52	EVP_MD_CTX md;
1e3b8b07	53	u_int rlen;
1e3b8b07	54	u_int slen;
42f11eb2	55	u_int len, dlen;
1e3b8b07	56	u_char sigblob[SIGBLOB_LEN];
4f8c6159	57	Buffer b;
	58
	59	if (key == NULL \|\| key->type != KEY_DSA \|\| key->dsa == NULL) {
fa08c86b	60	error("ssh_dss_sign: no DSA key");
4f8c6159	61	return -1;
4f8c6159	62	}
42f11eb2	63	dlen = evp_md->md_size;
42f11eb2	64	digest = xmalloc(dlen);
4f8c6159	65	EVP_DigestInit(&md, evp_md);
a306f2dd	66	EVP_DigestUpdate(&md, data, datalen);
4f8c6159	67	EVP_DigestFinal(&md, digest, NULL);
4f8c6159	68
42f11eb2	69	sig = DSA_do_sign(digest, dlen, key->dsa);
a306f2dd	70	if (sig == NULL) {
fa08c86b	71	fatal("ssh_dss_sign: cannot sign");
a306f2dd	72	}
42f11eb2	73	memset(digest, 0, dlen);
42f11eb2	74	xfree(digest);
4f8c6159	75
	76	rlen = BN_num_bytes(sig->r);
	77	slen = BN_num_bytes(sig->s);
	78	if (rlen > INTBLOB_LEN \|\| slen > INTBLOB_LEN) {
	79	error("bad sig size %d %d", rlen, slen);
	80	DSA_SIG_free(sig);
	81	return -1;
	82	}
	83	debug("sig size %d %d", rlen, slen);
	84
	85	memset(sigblob, 0, SIGBLOB_LEN);
	86	BN_bn2bin(sig->r, sigblob+ SIGBLOB_LEN - INTBLOB_LEN - rlen);
	87	BN_bn2bin(sig->s, sigblob+ SIGBLOB_LEN - slen);
	88	DSA_SIG_free(sig);
	89
d0c832f3	90	if (datafellows & SSH_BUG_SIGBLOB) {
4f8c6159	91	debug("datafellows");
	92	ret = xmalloc(SIGBLOB_LEN);
	93	memcpy(ret, sigblob, SIGBLOB_LEN);
	94	if (lenp != NULL)
	95	*lenp = SIGBLOB_LEN;
	96	if (sigp != NULL)
	97	*sigp = ret;
	98	} else {
	99	/* ietf-drafts */
	100	buffer_init(&b);
fa08c86b	101	buffer_put_cstring(&b, "ssh-dss");
4f8c6159	102	buffer_put_string(&b, sigblob, SIGBLOB_LEN);
	103	len = buffer_len(&b);
	104	ret = xmalloc(len);
	105	memcpy(ret, buffer_ptr(&b), len);
	106	buffer_free(&b);
	107	if (lenp != NULL)
	108	*lenp = len;
	109	if (sigp != NULL)
	110	*sigp = ret;
	111	}
	112	return 0;
	113	}
	114	int
fa08c86b	115	ssh_dss_verify(
4f8c6159	116	Key *key,
1e3b8b07	117	u_char *signature, int signaturelen,
1e3b8b07	118	u_char *data, int datalen)
4f8c6159	119	{
4f8c6159	120	Buffer b;
1e3b8b07	121	u_char *digest;
4f8c6159	122	DSA_SIG *sig;
	123	EVP_MD *evp_md = EVP_sha1();
	124	EVP_MD_CTX md;
1e3b8b07	125	u_char *sigblob;
4f8c6159	126	char *txt;
1e3b8b07	127	u_int len, dlen;
4f8c6159	128	int rlen;
	129	int ret;
	130
	131	if (key == NULL \|\| key->type != KEY_DSA \|\| key->dsa == NULL) {
fa08c86b	132	error("ssh_dss_verify: no DSA key");
4f8c6159	133	return -1;
	134	}
	135
d0c832f3	136	if (!(datafellows & SSH_BUG_SIGBLOB) &&
	137	signaturelen == SIGBLOB_LEN) {
	138	datafellows \|= ~SSH_BUG_SIGBLOB;
	139	log("autodetect SSH_BUG_SIGBLOB");
	140	} else if ((datafellows & SSH_BUG_SIGBLOB) &&
	141	signaturelen != SIGBLOB_LEN) {
	142	log("autoremove SSH_BUG_SIGBLOB");
	143	datafellows &= ~SSH_BUG_SIGBLOB;
4f8c6159	144	}
	145
	146	debug("len %d datafellows %d", signaturelen, datafellows);
	147
	148	/* fetch signature */
d0c832f3	149	if (datafellows & SSH_BUG_SIGBLOB) {
4f8c6159	150	sigblob = signature;
	151	len = signaturelen;
	152	} else {
	153	/* ietf-drafts */
74fc9186	154	char *ktype;
4f8c6159	155	buffer_init(&b);
	156	buffer_append(&b, (char *) signature, signaturelen);
	157	ktype = buffer_get_string(&b, NULL);
fa08c86b	158	if (strcmp("ssh-dss", ktype) != 0) {
fa08c86b	159	error("ssh_dss_verify: cannot handle type %s", ktype);
74fc9186	160	buffer_free(&b);
	161	return -1;
	162	}
1e3b8b07	163	sigblob = (u_char *)buffer_get_string(&b, &len);
4f8c6159	164	rlen = buffer_len(&b);
74fc9186	165	if(rlen != 0) {
4f8c6159	166	error("remaining bytes in signature %d", rlen);
74fc9186	167	buffer_free(&b);
	168	return -1;
	169	}
4f8c6159	170	buffer_free(&b);
74fc9186	171	xfree(ktype);
4f8c6159	172	}
	173
	174	if (len != SIGBLOB_LEN) {
	175	fatal("bad sigbloblen %d != SIGBLOB_LEN", len);
	176	}
	177
	178	/* parse signature */
	179	sig = DSA_SIG_new();
	180	sig->r = BN_new();
	181	sig->s = BN_new();
	182	BN_bin2bn(sigblob, INTBLOB_LEN, sig->r);
	183	BN_bin2bn(sigblob+ INTBLOB_LEN, INTBLOB_LEN, sig->s);
d0c832f3	184
d0c832f3	185	if (!(datafellows & SSH_BUG_SIGBLOB)) {
4f8c6159	186	memset(sigblob, 0, len);
	187	xfree(sigblob);
	188	}
2b87da3b	189
a306f2dd	190	/* sha1 the data */
fa08c86b	191	dlen = evp_md->md_size;
fa08c86b	192	digest = xmalloc(dlen);
4f8c6159	193	EVP_DigestInit(&md, evp_md);
a306f2dd	194	EVP_DigestUpdate(&md, data, datalen);
4f8c6159	195	EVP_DigestFinal(&md, digest, NULL);
4f8c6159	196
fa08c86b	197	ret = DSA_do_verify(digest, dlen, sig, key->dsa);
4f8c6159	198
fa08c86b	199	memset(digest, 0, dlen);
4f8c6159	200	xfree(digest);
	201	DSA_SIG_free(sig);
	202
	203	switch (ret) {
	204	case 1:
	205	txt = "correct";
	206	break;
	207	case 0:
	208	txt = "incorrect";
	209	break;
	210	case -1:
	211	default:
	212	txt = "error";
	213	break;
	214	}
fa08c86b	215	debug("ssh_dss_verify: signature %s", txt);
4f8c6159	216	return ret;
4f8c6159	217	}