[openssh.git] / ssh-rsa.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-rsa.c,v 1.29 2003/06/16 08:22:35 markus Exp $");

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

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

static int openssh_RSA_verify(int, u_char *, u_int, u_char *, u_int, RSA *);

/* RSASSA-PKCS1-v1_5 (PKCS #1 v2.0 signature) with SHA1 */
int
ssh_rsa_sign(Key *key, u_char **sigp, u_int *lenp,
    u_char *data, u_int datalen)
{
	const EVP_MD *evp_md;
	EVP_MD_CTX md;
	u_char digest[EVP_MAX_MD_SIZE], *sig;
	u_int slen, dlen, len;
	int ok, nid;
	Buffer b;

	if (key == NULL || key->type != KEY_RSA || key->rsa == NULL) {
		error("ssh_rsa_sign: no RSA key");
		return -1;
	}
	nid = (datafellows & SSH_BUG_RSASIGMD5) ? NID_md5 : NID_sha1;
	if ((evp_md = EVP_get_digestbynid(nid)) == NULL) {
		error("ssh_rsa_sign: EVP_get_digestbynid %d failed", nid);
		return -1;
	}
	EVP_DigestInit(&md, evp_md);
	EVP_DigestUpdate(&md, data, datalen);
	EVP_DigestFinal(&md, digest, &dlen);

	slen = RSA_size(key->rsa);
	sig = xmalloc(slen);

	ok = RSA_sign(nid, digest, dlen, sig, &len, key->rsa);
	memset(digest, 'd', sizeof(digest));

	if (ok != 1) {
		int ecode = ERR_get_error();
		error("ssh_rsa_sign: RSA_sign failed: %s",
		    ERR_error_string(ecode, NULL));
		xfree(sig);
		return -1;
	}
	if (len < slen) {
		u_int diff = slen - len;
		debug("slen %u > len %u", slen, len);
		memmove(sig + diff, sig, len);
		memset(sig, 0, diff);
	} else if (len > slen) {
		error("ssh_rsa_sign: slen %u slen2 %u", slen, len);
		xfree(sig);
		return -1;
	}
	/* encode signature */
	buffer_init(&b);
	buffer_put_cstring(&b, "ssh-rsa");
	buffer_put_string(&b, sig, slen);
	len = buffer_len(&b);
	if (lenp != NULL)
		*lenp = len;
	if (sigp != NULL) {
		*sigp = xmalloc(len);
		memcpy(*sigp, buffer_ptr(&b), len);
	}
	buffer_free(&b);
	memset(sig, 's', slen);
	xfree(sig);

	return 0;
}

int
ssh_rsa_verify(Key *key, u_char *signature, u_int signaturelen,
    u_char *data, u_int datalen)
{
	Buffer b;
	const EVP_MD *evp_md;
	EVP_MD_CTX md;
	char *ktype;
	u_char digest[EVP_MAX_MD_SIZE], *sigblob;
	u_int len, dlen, modlen;
	int rlen, ret, nid;

	if (key == NULL || key->type != KEY_RSA || key->rsa == NULL) {
		error("ssh_rsa_verify: no RSA key");
		return -1;
	}
	if (BN_num_bits(key->rsa->n) < SSH_RSA_MINIMUM_MODULUS_SIZE) {
		error("ssh_rsa_verify: RSA modulus too small: %d < minimum %d bits",
		    BN_num_bits(key->rsa->n), SSH_RSA_MINIMUM_MODULUS_SIZE);
		return -1;
	}
	buffer_init(&b);
	buffer_append(&b, signature, signaturelen);
	ktype = buffer_get_string(&b, NULL);
	if (strcmp("ssh-rsa", ktype) != 0) {
		error("ssh_rsa_verify: cannot handle type %s", ktype);
		buffer_free(&b);
		xfree(ktype);
		return -1;
	}
	xfree(ktype);
	sigblob = buffer_get_string(&b, &len);
	rlen = buffer_len(&b);
	buffer_free(&b);
	if (rlen != 0) {
		error("ssh_rsa_verify: remaining bytes in signature %d", rlen);
		xfree(sigblob);
		return -1;
	}
	/* RSA_verify expects a signature of RSA_size */
	modlen = RSA_size(key->rsa);
	if (len > modlen) {
		error("ssh_rsa_verify: len %u > modlen %u", len, modlen);
		xfree(sigblob);
		return -1;
	} else if (len < modlen) {
		u_int diff = modlen - len;
		debug("ssh_rsa_verify: add padding: modlen %u > len %u",
		    modlen, len);
		sigblob = xrealloc(sigblob, modlen);
		memmove(sigblob + diff, sigblob, len);
		memset(sigblob, 0, diff);
		len = modlen;
	}
	nid = (datafellows & SSH_BUG_RSASIGMD5) ? NID_md5 : NID_sha1;
	if ((evp_md = EVP_get_digestbynid(nid)) == NULL) {
		error("ssh_rsa_verify: EVP_get_digestbynid %d failed", nid);
		xfree(sigblob);
		return -1;
	}
	EVP_DigestInit(&md, evp_md);
	EVP_DigestUpdate(&md, data, datalen);
	EVP_DigestFinal(&md, digest, &dlen);

	ret = openssh_RSA_verify(nid, digest, dlen, sigblob, len, key->rsa);
	memset(digest, 'd', sizeof(digest));
	memset(sigblob, 's', len);
	xfree(sigblob);
	debug("ssh_rsa_verify: signature %scorrect", (ret==0) ? "in" : "");
	return ret;
}

/*
 * See:
 * http://www.rsasecurity.com/rsalabs/pkcs/pkcs-1/
 * ftp://ftp.rsasecurity.com/pub/pkcs/pkcs-1/pkcs-1v2-1.asn
 */
/*
 * id-sha1 OBJECT IDENTIFIER ::= { iso(1) identified-organization(3)
 *	oiw(14) secsig(3) algorithms(2) 26 }
 */
static const u_char id_sha1[] = {
	0x30, 0x21, /* type Sequence, length 0x21 (33) */
	0x30, 0x09, /* type Sequence, length 0x09 */
	0x06, 0x05, /* type OID, length 0x05 */
	0x2b, 0x0e, 0x03, 0x02, 0x1a, /* id-sha1 OID */
	0x05, 0x00, /* NULL */
	0x04, 0x14  /* Octet string, length 0x14 (20), followed by sha1 hash */
};
/*
 * id-md5 OBJECT IDENTIFIER ::= { iso(1) member-body(2) us(840)
 *	rsadsi(113549) digestAlgorithm(2) 5 }
 */
static const u_char id_md5[] = {
	0x30, 0x20, /* type Sequence, length 0x20 (32) */
	0x30, 0x0c, /* type Sequence, length 0x09 */
	0x06, 0x08, /* type OID, length 0x05 */
	0x2a, 0x86, 0x48, 0x86, 0xF7, 0x0D, 0x02, 0x05, /* id-md5 */
	0x05, 0x00, /* NULL */
	0x04, 0x10  /* Octet string, length 0x10 (16), followed by md5 hash */
};

static int
openssh_RSA_verify(int type, u_char *hash, u_int hashlen,
    u_char *sigbuf, u_int siglen, RSA *rsa)
{
	u_int ret, rsasize, oidlen = 0, hlen = 0;
	int len;
	const u_char *oid = NULL;
	u_char *decrypted = NULL;

	ret = 0;
	switch (type) {
	case NID_sha1:
		oid = id_sha1;
		oidlen = sizeof(id_sha1);
		hlen = 20;
		break;
	case NID_md5:
		oid = id_md5;
		oidlen = sizeof(id_md5);
		hlen = 16;
		break;
	default:
		goto done;
		break;
	}
	if (hashlen != hlen) {
		error("bad hashlen");
		goto done;
	}
	rsasize = RSA_size(rsa);
	if (siglen == 0 || siglen > rsasize) {
		error("bad siglen");
		goto done;
	}
	decrypted = xmalloc(rsasize);
	if ((len = RSA_public_decrypt(siglen, sigbuf, decrypted, rsa,
	    RSA_PKCS1_PADDING)) < 0) {
		error("RSA_public_decrypt failed: %s",
		    ERR_error_string(ERR_get_error(), NULL));
		goto done;
	}
	if (len < hlen + oidlen) {
		error("bad decrypted len: %d < %d + %d", len, hlen, oidlen);
		goto done;
	}
	if (memcmp(decrypted, oid, oidlen) != 0) {
		error("oid mismatch");
		goto done;
	}
	if (memcmp(decrypted + oidlen, hash, hlen) != 0) {
		error("hash mismatch");
		goto done;
	}
	ret = 1;
done:
	if (decrypted)
		xfree(decrypted);
	return ret;
}
Commit	Line	Data
fa08c86b	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"
9250058a	26	RCSID("$OpenBSD: ssh-rsa.c,v 1.29 2003/06/16 08:22:35 markus Exp $");
fa08c86b	27
fa08c86b	28	#include <openssl/evp.h>
fa08c86b	29	#include <openssl/err.h>
fa08c86b	30
42f11eb2	31	#include "xmalloc.h"
	32	#include "log.h"
	33	#include "buffer.h"
	34	#include "bufaux.h"
fa08c86b	35	#include "key.h"
a4da628b	36	#include "compat.h"
82b00264	37	#include "ssh.h"
fa08c86b	38
b77a87e5	39	static int openssh_RSA_verify(int, u_char , u_int, u_char , u_int, RSA *);
0caf874a	40
fa08c86b	41	/* RSASSA-PKCS1-v1_5 (PKCS #1 v2.0 signature) with SHA1 */
fa08c86b	42	int
d6133f43	43	ssh_rsa_sign(Key key, u_char sigp, u_int lenp,
c66f9d0e	44	u_char *data, u_int datalen)
fa08c86b	45	{
1a92bd7e	46	const EVP_MD *evp_md;
fa08c86b	47	EVP_MD_CTX md;
eb9f2fab	48	u_char digest[EVP_MAX_MD_SIZE], *sig;
1e3b8b07	49	u_int slen, dlen, len;
1a92bd7e	50	int ok, nid;
fa08c86b	51	Buffer b;
	52
	53	if (key == NULL \|\| key->type != KEY_RSA \|\| key->rsa == NULL) {
	54	error("ssh_rsa_sign: no RSA key");
	55	return -1;
	56	}
a4da628b	57	nid = (datafellows & SSH_BUG_RSASIGMD5) ? NID_md5 : NID_sha1;
1a92bd7e	58	if ((evp_md = EVP_get_digestbynid(nid)) == NULL) {
	59	error("ssh_rsa_sign: EVP_get_digestbynid %d failed", nid);
	60	return -1;
	61	}
fa08c86b	62	EVP_DigestInit(&md, evp_md);
fa08c86b	63	EVP_DigestUpdate(&md, data, datalen);
087dea86	64	EVP_DigestFinal(&md, digest, &dlen);
fa08c86b	65
1a92bd7e	66	slen = RSA_size(key->rsa);
	67	sig = xmalloc(slen);
	68
	69	ok = RSA_sign(nid, digest, dlen, sig, &len, key->rsa);
087dea86	70	memset(digest, 'd', sizeof(digest));
fa08c86b	71
	72	if (ok != 1) {
	73	int ecode = ERR_get_error();
d6133f43	74	error("ssh_rsa_sign: RSA_sign failed: %s",
d6133f43	75	ERR_error_string(ecode, NULL));
fa08c86b	76	xfree(sig);
	77	return -1;
	78	}
	79	if (len < slen) {
4004c2ac	80	u_int diff = slen - len;
d6133f43	81	debug("slen %u > len %u", slen, len);
fa08c86b	82	memmove(sig + diff, sig, len);
	83	memset(sig, 0, diff);
	84	} else if (len > slen) {
d6133f43	85	error("ssh_rsa_sign: slen %u slen2 %u", slen, len);
fa08c86b	86	xfree(sig);
	87	return -1;
	88	}
	89	/* encode signature */
	90	buffer_init(&b);
	91	buffer_put_cstring(&b, "ssh-rsa");
	92	buffer_put_string(&b, sig, slen);
	93	len = buffer_len(&b);
eb9f2fab	94	if (lenp != NULL)
	95	*lenp = len;
	96	if (sigp != NULL) {
	97	*sigp = xmalloc(len);
	98	memcpy(*sigp, buffer_ptr(&b), len);
	99	}
fa08c86b	100	buffer_free(&b);
	101	memset(sig, 's', slen);
	102	xfree(sig);
	103
fa08c86b	104	return 0;
	105	}
	106
	107	int
d6133f43	108	ssh_rsa_verify(Key key, u_char signature, u_int signaturelen,
c66f9d0e	109	u_char *data, u_int datalen)
fa08c86b	110	{
fa08c86b	111	Buffer b;
1a92bd7e	112	const EVP_MD *evp_md;
fa08c86b	113	EVP_MD_CTX md;
fa08c86b	114	char *ktype;
087dea86	115	u_char digest[EVP_MAX_MD_SIZE], *sigblob;
88f24e9d	116	u_int len, dlen, modlen;
1a92bd7e	117	int rlen, ret, nid;
fa08c86b	118
	119	if (key == NULL \|\| key->type != KEY_RSA \|\| key->rsa == NULL) {
	120	error("ssh_rsa_verify: no RSA key");
	121	return -1;
	122	}
82b00264	123	if (BN_num_bits(key->rsa->n) < SSH_RSA_MINIMUM_MODULUS_SIZE) {
b7ced7d1	124	error("ssh_rsa_verify: RSA modulus too small: %d < minimum %d bits",
b7ced7d1	125	BN_num_bits(key->rsa->n), SSH_RSA_MINIMUM_MODULUS_SIZE);
b5c334cc	126	return -1;
b5c334cc	127	}
fa08c86b	128	buffer_init(&b);
cf54363d	129	buffer_append(&b, signature, signaturelen);
fa08c86b	130	ktype = buffer_get_string(&b, NULL);
	131	if (strcmp("ssh-rsa", ktype) != 0) {
	132	error("ssh_rsa_verify: cannot handle type %s", ktype);
	133	buffer_free(&b);
	134	xfree(ktype);
	135	return -1;
	136	}
	137	xfree(ktype);
cf54363d	138	sigblob = buffer_get_string(&b, &len);
fa08c86b	139	rlen = buffer_len(&b);
fa08c86b	140	buffer_free(&b);
6aacefa7	141	if (rlen != 0) {
fa08c86b	142	error("ssh_rsa_verify: remaining bytes in signature %d", rlen);
abc4e9a7	143	xfree(sigblob);
fa08c86b	144	return -1;
fa08c86b	145	}
88f24e9d	146	/* RSA_verify expects a signature of RSA_size */
	147	modlen = RSA_size(key->rsa);
	148	if (len > modlen) {
d6133f43	149	error("ssh_rsa_verify: len %u > modlen %u", len, modlen);
88f24e9d	150	xfree(sigblob);
	151	return -1;
	152	} else if (len < modlen) {
4004c2ac	153	u_int diff = modlen - len;
d6133f43	154	debug("ssh_rsa_verify: add padding: modlen %u > len %u",
88f24e9d	155	modlen, len);
	156	sigblob = xrealloc(sigblob, modlen);
	157	memmove(sigblob + diff, sigblob, len);
	158	memset(sigblob, 0, diff);
	159	len = modlen;
	160	}
a4da628b	161	nid = (datafellows & SSH_BUG_RSASIGMD5) ? NID_md5 : NID_sha1;
1a92bd7e	162	if ((evp_md = EVP_get_digestbynid(nid)) == NULL) {
1a92bd7e	163	error("ssh_rsa_verify: EVP_get_digestbynid %d failed", nid);
abc4e9a7	164	xfree(sigblob);
1a92bd7e	165	return -1;
1a92bd7e	166	}
fa08c86b	167	EVP_DigestInit(&md, evp_md);
fa08c86b	168	EVP_DigestUpdate(&md, data, datalen);
087dea86	169	EVP_DigestFinal(&md, digest, &dlen);
fa08c86b	170
0caf874a	171	ret = openssh_RSA_verify(nid, digest, dlen, sigblob, len, key->rsa);
087dea86	172	memset(digest, 'd', sizeof(digest));
fa08c86b	173	memset(sigblob, 's', len);
fa08c86b	174	xfree(sigblob);
fa08c86b	175	debug("ssh_rsa_verify: signature %scorrect", (ret==0) ? "in" : "");
	176	return ret;
	177	}
0caf874a	178
	179	/*
	180	* See:
	181	* http://www.rsasecurity.com/rsalabs/pkcs/pkcs-1/
	182	* ftp://ftp.rsasecurity.com/pub/pkcs/pkcs-1/pkcs-1v2-1.asn
	183	*/
	184	/*
	185	* id-sha1 OBJECT IDENTIFIER ::= { iso(1) identified-organization(3)
	186	* oiw(14) secsig(3) algorithms(2) 26 }
	187	*/
	188	static const u_char id_sha1[] = {
	189	0x30, 0x21, /* type Sequence, length 0x21 (33) */
	190	0x30, 0x09, /* type Sequence, length 0x09 */
	191	0x06, 0x05, /* type OID, length 0x05 */
	192	0x2b, 0x0e, 0x03, 0x02, 0x1a, /* id-sha1 OID */
	193	0x05, 0x00, /* NULL */
	194	0x04, 0x14 /* Octet string, length 0x14 (20), followed by sha1 hash */
	195	};
	196	/*
	197	* id-md5 OBJECT IDENTIFIER ::= { iso(1) member-body(2) us(840)
	198	* rsadsi(113549) digestAlgorithm(2) 5 }
	199	*/
	200	static const u_char id_md5[] = {
	201	0x30, 0x20, /* type Sequence, length 0x20 (32) */
	202	0x30, 0x0c, /* type Sequence, length 0x09 */
	203	0x06, 0x08, /* type OID, length 0x05 */
	204	0x2a, 0x86, 0x48, 0x86, 0xF7, 0x0D, 0x02, 0x05, /* id-md5 */
	205	0x05, 0x00, /* NULL */
	206	0x04, 0x10 /* Octet string, length 0x10 (16), followed by md5 hash */
	207	};
	208
	209	static int
	210	openssh_RSA_verify(int type, u_char *hash, u_int hashlen,
	211	u_char sigbuf, u_int siglen, RSA rsa)
	212	{
b41baf4d	213	u_int ret, rsasize, oidlen = 0, hlen = 0;
b41baf4d	214	int len;
0caf874a	215	const u_char *oid = NULL;
	216	u_char *decrypted = NULL;
	217
	218	ret = 0;
	219	switch (type) {
	220	case NID_sha1:
	221	oid = id_sha1;
	222	oidlen = sizeof(id_sha1);
	223	hlen = 20;
	224	break;
	225	case NID_md5:
	226	oid = id_md5;
	227	oidlen = sizeof(id_md5);
	228	hlen = 16;
	229	break;
	230	default:
	231	goto done;
	232	break;
	233	}
	234	if (hashlen != hlen) {
	235	error("bad hashlen");
	236	goto done;
	237	}
	238	rsasize = RSA_size(rsa);
	239	if (siglen == 0 \|\| siglen > rsasize) {
	240	error("bad siglen");
	241	goto done;
	242	}
	243	decrypted = xmalloc(rsasize);
	244	if ((len = RSA_public_decrypt(siglen, sigbuf, decrypted, rsa,
	245	RSA_PKCS1_PADDING)) < 0) {
	246	error("RSA_public_decrypt failed: %s",
	247	ERR_error_string(ERR_get_error(), NULL));
	248	goto done;
	249	}
9250058a	250	if (len < hlen + oidlen) {
9250058a	251	error("bad decrypted len: %d < %d + %d", len, hlen, oidlen);
0caf874a	252	goto done;
	253	}
	254	if (memcmp(decrypted, oid, oidlen) != 0) {
	255	error("oid mismatch");
	256	goto done;
	257	}
	258	if (memcmp(decrypted + oidlen, hash, hlen) != 0) {
	259	error("hash mismatch");
	260	goto done;
	261	}
	262	ret = 1;
	263	done:
	264	if (decrypted)
	265	xfree(decrypted);
	266	return ret;
	267	}