[openssh.git] / ssh-rsa.c

/* $OpenBSD: ssh-rsa.c,v 1.39 2006/08/03 03:34:42 deraadt Exp $ */
/*
 * Copyright (c) 2000, 2003 Markus Friedl <markus@openbsd.org>
 *
 * Permission to use, copy, modify, and distribute this software for any
 * purpose with or without fee is hereby granted, provided that the above
 * copyright notice and this permission notice appear in all copies.
 *
 * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
 * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
 * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
 * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
 * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
 * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
 * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
 */

#include "includes.h"

#include <sys/types.h>

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

#include <stdarg.h>
#include <string.h>

#include "xmalloc.h"
#include "log.h"
#include "buffer.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(const Key *key, u_char **sigp, u_int *lenp,
    const 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(const Key *key, const u_char *signature, u_int signaturelen,
    const 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, 1, 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;
	}
	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 < 0 || (u_int)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
31652869	1	/* $OpenBSD: ssh-rsa.c,v 1.39 2006/08/03 03:34:42 deraadt Exp $ */
fa08c86b	2	/*
c1ffd4bd	3	* Copyright (c) 2000, 2003 Markus Friedl <markus@openbsd.org>
fa08c86b	4	*
c1ffd4bd	5	* Permission to use, copy, modify, and distribute this software for any
	6	* purpose with or without fee is hereby granted, provided that the above
	7	* copyright notice and this permission notice appear in all copies.
fa08c86b	8	*
c1ffd4bd	9	* THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
	10	* WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
	11	* MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
	12	* ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
	13	* WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
	14	* ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
	15	* OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
fa08c86b	16	*/
31652869	17
fa08c86b	18	#include "includes.h"
fa08c86b	19
31652869	20	#include <sys/types.h>
31652869	21
fa08c86b	22	#include <openssl/evp.h>
fa08c86b	23	#include <openssl/err.h>
fa08c86b	24
24436b92	25	#include <stdarg.h>
00146caa	26	#include <string.h>
00146caa	27
42f11eb2	28	#include "xmalloc.h"
	29	#include "log.h"
	30	#include "buffer.h"
fa08c86b	31	#include "key.h"
a4da628b	32	#include "compat.h"
82b00264	33	#include "ssh.h"
fa08c86b	34
b77a87e5	35	static int openssh_RSA_verify(int, u_char , u_int, u_char , u_int, RSA *);
0caf874a	36
fa08c86b	37	/* RSASSA-PKCS1-v1_5 (PKCS #1 v2.0 signature) with SHA1 */
fa08c86b	38	int
b6c7b7b7	39	ssh_rsa_sign(const Key key, u_char sigp, u_int lenp,
b6c7b7b7	40	const u_char *data, u_int datalen)
fa08c86b	41	{
1a92bd7e	42	const EVP_MD *evp_md;
fa08c86b	43	EVP_MD_CTX md;
eb9f2fab	44	u_char digest[EVP_MAX_MD_SIZE], *sig;
1e3b8b07	45	u_int slen, dlen, len;
1a92bd7e	46	int ok, nid;
fa08c86b	47	Buffer b;
	48
	49	if (key == NULL \|\| key->type != KEY_RSA \|\| key->rsa == NULL) {
	50	error("ssh_rsa_sign: no RSA key");
	51	return -1;
	52	}
a4da628b	53	nid = (datafellows & SSH_BUG_RSASIGMD5) ? NID_md5 : NID_sha1;
1a92bd7e	54	if ((evp_md = EVP_get_digestbynid(nid)) == NULL) {
	55	error("ssh_rsa_sign: EVP_get_digestbynid %d failed", nid);
	56	return -1;
	57	}
fa08c86b	58	EVP_DigestInit(&md, evp_md);
fa08c86b	59	EVP_DigestUpdate(&md, data, datalen);
087dea86	60	EVP_DigestFinal(&md, digest, &dlen);
fa08c86b	61
1a92bd7e	62	slen = RSA_size(key->rsa);
	63	sig = xmalloc(slen);
	64
	65	ok = RSA_sign(nid, digest, dlen, sig, &len, key->rsa);
087dea86	66	memset(digest, 'd', sizeof(digest));
fa08c86b	67
	68	if (ok != 1) {
	69	int ecode = ERR_get_error();
32596c7b	70
d6133f43	71	error("ssh_rsa_sign: RSA_sign failed: %s",
d6133f43	72	ERR_error_string(ecode, NULL));
fa08c86b	73	xfree(sig);
	74	return -1;
	75	}
	76	if (len < slen) {
4004c2ac	77	u_int diff = slen - len;
d6133f43	78	debug("slen %u > len %u", slen, len);
fa08c86b	79	memmove(sig + diff, sig, len);
	80	memset(sig, 0, diff);
	81	} else if (len > slen) {
d6133f43	82	error("ssh_rsa_sign: slen %u slen2 %u", slen, len);
fa08c86b	83	xfree(sig);
	84	return -1;
	85	}
	86	/* encode signature */
	87	buffer_init(&b);
	88	buffer_put_cstring(&b, "ssh-rsa");
	89	buffer_put_string(&b, sig, slen);
	90	len = buffer_len(&b);
eb9f2fab	91	if (lenp != NULL)
	92	*lenp = len;
	93	if (sigp != NULL) {
	94	*sigp = xmalloc(len);
	95	memcpy(*sigp, buffer_ptr(&b), len);
	96	}
fa08c86b	97	buffer_free(&b);
	98	memset(sig, 's', slen);
	99	xfree(sig);
	100
fa08c86b	101	return 0;
	102	}
	103
	104	int
b6c7b7b7	105	ssh_rsa_verify(const Key key, const u_char signature, u_int signaturelen,
b6c7b7b7	106	const u_char *data, u_int datalen)
fa08c86b	107	{
fa08c86b	108	Buffer b;
1a92bd7e	109	const EVP_MD *evp_md;
fa08c86b	110	EVP_MD_CTX md;
fa08c86b	111	char *ktype;
087dea86	112	u_char digest[EVP_MAX_MD_SIZE], *sigblob;
88f24e9d	113	u_int len, dlen, modlen;
1a92bd7e	114	int rlen, ret, nid;
fa08c86b	115
	116	if (key == NULL \|\| key->type != KEY_RSA \|\| key->rsa == NULL) {
	117	error("ssh_rsa_verify: no RSA key");
	118	return -1;
	119	}
82b00264	120	if (BN_num_bits(key->rsa->n) < SSH_RSA_MINIMUM_MODULUS_SIZE) {
b7ced7d1	121	error("ssh_rsa_verify: RSA modulus too small: %d < minimum %d bits",
b7ced7d1	122	BN_num_bits(key->rsa->n), SSH_RSA_MINIMUM_MODULUS_SIZE);
b5c334cc	123	return -1;
b5c334cc	124	}
fa08c86b	125	buffer_init(&b);
cf54363d	126	buffer_append(&b, signature, signaturelen);
fa08c86b	127	ktype = buffer_get_string(&b, NULL);
	128	if (strcmp("ssh-rsa", ktype) != 0) {
	129	error("ssh_rsa_verify: cannot handle type %s", ktype);
	130	buffer_free(&b);
	131	xfree(ktype);
	132	return -1;
	133	}
	134	xfree(ktype);
cf54363d	135	sigblob = buffer_get_string(&b, &len);
fa08c86b	136	rlen = buffer_len(&b);
fa08c86b	137	buffer_free(&b);
6aacefa7	138	if (rlen != 0) {
fa08c86b	139	error("ssh_rsa_verify: remaining bytes in signature %d", rlen);
abc4e9a7	140	xfree(sigblob);
fa08c86b	141	return -1;
fa08c86b	142	}
88f24e9d	143	/* RSA_verify expects a signature of RSA_size */
	144	modlen = RSA_size(key->rsa);
	145	if (len > modlen) {
d6133f43	146	error("ssh_rsa_verify: len %u > modlen %u", len, modlen);
88f24e9d	147	xfree(sigblob);
	148	return -1;
	149	} else if (len < modlen) {
4004c2ac	150	u_int diff = modlen - len;
d6133f43	151	debug("ssh_rsa_verify: add padding: modlen %u > len %u",
88f24e9d	152	modlen, len);
c5d10563	153	sigblob = xrealloc(sigblob, 1, modlen);
88f24e9d	154	memmove(sigblob + diff, sigblob, len);
	155	memset(sigblob, 0, diff);
	156	len = modlen;
	157	}
a4da628b	158	nid = (datafellows & SSH_BUG_RSASIGMD5) ? NID_md5 : NID_sha1;
1a92bd7e	159	if ((evp_md = EVP_get_digestbynid(nid)) == NULL) {
1a92bd7e	160	error("ssh_rsa_verify: EVP_get_digestbynid %d failed", nid);
abc4e9a7	161	xfree(sigblob);
1a92bd7e	162	return -1;
1a92bd7e	163	}
fa08c86b	164	EVP_DigestInit(&md, evp_md);
fa08c86b	165	EVP_DigestUpdate(&md, data, datalen);
087dea86	166	EVP_DigestFinal(&md, digest, &dlen);
fa08c86b	167
0caf874a	168	ret = openssh_RSA_verify(nid, digest, dlen, sigblob, len, key->rsa);
087dea86	169	memset(digest, 'd', sizeof(digest));
fa08c86b	170	memset(sigblob, 's', len);
fa08c86b	171	xfree(sigblob);
fa08c86b	172	debug("ssh_rsa_verify: signature %scorrect", (ret==0) ? "in" : "");
	173	return ret;
	174	}
0caf874a	175
	176	/*
	177	* See:
	178	* http://www.rsasecurity.com/rsalabs/pkcs/pkcs-1/
	179	* ftp://ftp.rsasecurity.com/pub/pkcs/pkcs-1/pkcs-1v2-1.asn
	180	*/
	181	/*
	182	* id-sha1 OBJECT IDENTIFIER ::= { iso(1) identified-organization(3)
	183	* oiw(14) secsig(3) algorithms(2) 26 }
	184	*/
	185	static const u_char id_sha1[] = {
	186	0x30, 0x21, /* type Sequence, length 0x21 (33) */
	187	0x30, 0x09, /* type Sequence, length 0x09 */
	188	0x06, 0x05, /* type OID, length 0x05 */
	189	0x2b, 0x0e, 0x03, 0x02, 0x1a, /* id-sha1 OID */
	190	0x05, 0x00, /* NULL */
	191	0x04, 0x14 /* Octet string, length 0x14 (20), followed by sha1 hash */
	192	};
	193	/*
	194	* id-md5 OBJECT IDENTIFIER ::= { iso(1) member-body(2) us(840)
	195	* rsadsi(113549) digestAlgorithm(2) 5 }
	196	*/
	197	static const u_char id_md5[] = {
	198	0x30, 0x20, /* type Sequence, length 0x20 (32) */
	199	0x30, 0x0c, /* type Sequence, length 0x09 */
	200	0x06, 0x08, /* type OID, length 0x05 */
	201	0x2a, 0x86, 0x48, 0x86, 0xF7, 0x0D, 0x02, 0x05, /* id-md5 */
	202	0x05, 0x00, /* NULL */
	203	0x04, 0x10 /* Octet string, length 0x10 (16), followed by md5 hash */
	204	};
	205
	206	static int
	207	openssh_RSA_verify(int type, u_char *hash, u_int hashlen,
	208	u_char sigbuf, u_int siglen, RSA rsa)
	209	{
b41baf4d	210	u_int ret, rsasize, oidlen = 0, hlen = 0;
b41baf4d	211	int len;
0caf874a	212	const u_char *oid = NULL;
	213	u_char *decrypted = NULL;
	214
	215	ret = 0;
	216	switch (type) {
	217	case NID_sha1:
	218	oid = id_sha1;
	219	oidlen = sizeof(id_sha1);
	220	hlen = 20;
	221	break;
	222	case NID_md5:
	223	oid = id_md5;
	224	oidlen = sizeof(id_md5);
	225	hlen = 16;
	226	break;
	227	default:
	228	goto done;
0caf874a	229	}
	230	if (hashlen != hlen) {
	231	error("bad hashlen");
	232	goto done;
	233	}
	234	rsasize = RSA_size(rsa);
	235	if (siglen == 0 \|\| siglen > rsasize) {
	236	error("bad siglen");
	237	goto done;
	238	}
	239	decrypted = xmalloc(rsasize);
	240	if ((len = RSA_public_decrypt(siglen, sigbuf, decrypted, rsa,
	241	RSA_PKCS1_PADDING)) < 0) {
	242	error("RSA_public_decrypt failed: %s",
	243	ERR_error_string(ERR_get_error(), NULL));
	244	goto done;
	245	}
2ceb8101	246	if (len < 0 \|\| (u_int)len != hlen + oidlen) {
c1ffd4bd	247	error("bad decrypted len: %d != %d + %d", len, hlen, oidlen);
0caf874a	248	goto done;
	249	}
	250	if (memcmp(decrypted, oid, oidlen) != 0) {
	251	error("oid mismatch");
	252	goto done;
	253	}
	254	if (memcmp(decrypted + oidlen, hash, hlen) != 0) {
	255	error("hash mismatch");
	256	goto done;
	257	}
	258	ret = 1;
	259	done:
	260	if (decrypted)
	261	xfree(decrypted);
	262	return ret;
	263	}