[openssh.git] / ssh-rsa.c

/*
 * 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"
RCSID("$OpenBSD: ssh-rsa.c,v 1.31 2003/11/10 16:23:41 jakob 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(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, 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	/*
c1ffd4bd	2	* Copyright (c) 2000, 2003 Markus Friedl <markus@openbsd.org>
fa08c86b	3	*
c1ffd4bd	4	* Permission to use, copy, modify, and distribute this software for any
	5	* purpose with or without fee is hereby granted, provided that the above
	6	* copyright notice and this permission notice appear in all copies.
fa08c86b	7	*
c1ffd4bd	8	* THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
	9	* WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
	10	* MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
	11	* ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
	12	* WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
	13	* ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
	14	* OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
fa08c86b	15	*/
fa08c86b	16	#include "includes.h"
b6c7b7b7	17	RCSID("$OpenBSD: ssh-rsa.c,v 1.31 2003/11/10 16:23:41 jakob Exp $");
fa08c86b	18
fa08c86b	19	#include <openssl/evp.h>
fa08c86b	20	#include <openssl/err.h>
fa08c86b	21
42f11eb2	22	#include "xmalloc.h"
	23	#include "log.h"
	24	#include "buffer.h"
	25	#include "bufaux.h"
fa08c86b	26	#include "key.h"
a4da628b	27	#include "compat.h"
82b00264	28	#include "ssh.h"
fa08c86b	29
b77a87e5	30	static int openssh_RSA_verify(int, u_char , u_int, u_char , u_int, RSA *);
0caf874a	31
fa08c86b	32	/* RSASSA-PKCS1-v1_5 (PKCS #1 v2.0 signature) with SHA1 */
fa08c86b	33	int
b6c7b7b7	34	ssh_rsa_sign(const Key key, u_char sigp, u_int lenp,
b6c7b7b7	35	const u_char *data, u_int datalen)
fa08c86b	36	{
1a92bd7e	37	const EVP_MD *evp_md;
fa08c86b	38	EVP_MD_CTX md;
eb9f2fab	39	u_char digest[EVP_MAX_MD_SIZE], *sig;
1e3b8b07	40	u_int slen, dlen, len;
1a92bd7e	41	int ok, nid;
fa08c86b	42	Buffer b;
	43
	44	if (key == NULL \|\| key->type != KEY_RSA \|\| key->rsa == NULL) {
	45	error("ssh_rsa_sign: no RSA key");
	46	return -1;
	47	}
a4da628b	48	nid = (datafellows & SSH_BUG_RSASIGMD5) ? NID_md5 : NID_sha1;
1a92bd7e	49	if ((evp_md = EVP_get_digestbynid(nid)) == NULL) {
	50	error("ssh_rsa_sign: EVP_get_digestbynid %d failed", nid);
	51	return -1;
	52	}
fa08c86b	53	EVP_DigestInit(&md, evp_md);
fa08c86b	54	EVP_DigestUpdate(&md, data, datalen);
087dea86	55	EVP_DigestFinal(&md, digest, &dlen);
fa08c86b	56
1a92bd7e	57	slen = RSA_size(key->rsa);
	58	sig = xmalloc(slen);
	59
	60	ok = RSA_sign(nid, digest, dlen, sig, &len, key->rsa);
087dea86	61	memset(digest, 'd', sizeof(digest));
fa08c86b	62
	63	if (ok != 1) {
	64	int ecode = ERR_get_error();
d6133f43	65	error("ssh_rsa_sign: RSA_sign failed: %s",
d6133f43	66	ERR_error_string(ecode, NULL));
fa08c86b	67	xfree(sig);
	68	return -1;
	69	}
	70	if (len < slen) {
4004c2ac	71	u_int diff = slen - len;
d6133f43	72	debug("slen %u > len %u", slen, len);
fa08c86b	73	memmove(sig + diff, sig, len);
	74	memset(sig, 0, diff);
	75	} else if (len > slen) {
d6133f43	76	error("ssh_rsa_sign: slen %u slen2 %u", slen, len);
fa08c86b	77	xfree(sig);
	78	return -1;
	79	}
	80	/* encode signature */
	81	buffer_init(&b);
	82	buffer_put_cstring(&b, "ssh-rsa");
	83	buffer_put_string(&b, sig, slen);
	84	len = buffer_len(&b);
eb9f2fab	85	if (lenp != NULL)
	86	*lenp = len;
	87	if (sigp != NULL) {
	88	*sigp = xmalloc(len);
	89	memcpy(*sigp, buffer_ptr(&b), len);
	90	}
fa08c86b	91	buffer_free(&b);
	92	memset(sig, 's', slen);
	93	xfree(sig);
	94
fa08c86b	95	return 0;
	96	}
	97
	98	int
b6c7b7b7	99	ssh_rsa_verify(const Key key, const u_char signature, u_int signaturelen,
b6c7b7b7	100	const u_char *data, u_int datalen)
fa08c86b	101	{
fa08c86b	102	Buffer b;
1a92bd7e	103	const EVP_MD *evp_md;
fa08c86b	104	EVP_MD_CTX md;
fa08c86b	105	char *ktype;
087dea86	106	u_char digest[EVP_MAX_MD_SIZE], *sigblob;
88f24e9d	107	u_int len, dlen, modlen;
1a92bd7e	108	int rlen, ret, nid;
fa08c86b	109
	110	if (key == NULL \|\| key->type != KEY_RSA \|\| key->rsa == NULL) {
	111	error("ssh_rsa_verify: no RSA key");
	112	return -1;
	113	}
82b00264	114	if (BN_num_bits(key->rsa->n) < SSH_RSA_MINIMUM_MODULUS_SIZE) {
b7ced7d1	115	error("ssh_rsa_verify: RSA modulus too small: %d < minimum %d bits",
b7ced7d1	116	BN_num_bits(key->rsa->n), SSH_RSA_MINIMUM_MODULUS_SIZE);
b5c334cc	117	return -1;
b5c334cc	118	}
fa08c86b	119	buffer_init(&b);
cf54363d	120	buffer_append(&b, signature, signaturelen);
fa08c86b	121	ktype = buffer_get_string(&b, NULL);
	122	if (strcmp("ssh-rsa", ktype) != 0) {
	123	error("ssh_rsa_verify: cannot handle type %s", ktype);
	124	buffer_free(&b);
	125	xfree(ktype);
	126	return -1;
	127	}
	128	xfree(ktype);
cf54363d	129	sigblob = buffer_get_string(&b, &len);
fa08c86b	130	rlen = buffer_len(&b);
fa08c86b	131	buffer_free(&b);
6aacefa7	132	if (rlen != 0) {
fa08c86b	133	error("ssh_rsa_verify: remaining bytes in signature %d", rlen);
abc4e9a7	134	xfree(sigblob);
fa08c86b	135	return -1;
fa08c86b	136	}
88f24e9d	137	/* RSA_verify expects a signature of RSA_size */
	138	modlen = RSA_size(key->rsa);
	139	if (len > modlen) {
d6133f43	140	error("ssh_rsa_verify: len %u > modlen %u", len, modlen);
88f24e9d	141	xfree(sigblob);
	142	return -1;
	143	} else if (len < modlen) {
4004c2ac	144	u_int diff = modlen - len;
d6133f43	145	debug("ssh_rsa_verify: add padding: modlen %u > len %u",
88f24e9d	146	modlen, len);
	147	sigblob = xrealloc(sigblob, modlen);
	148	memmove(sigblob + diff, sigblob, len);
	149	memset(sigblob, 0, diff);
	150	len = modlen;
	151	}
a4da628b	152	nid = (datafellows & SSH_BUG_RSASIGMD5) ? NID_md5 : NID_sha1;
1a92bd7e	153	if ((evp_md = EVP_get_digestbynid(nid)) == NULL) {
1a92bd7e	154	error("ssh_rsa_verify: EVP_get_digestbynid %d failed", nid);
abc4e9a7	155	xfree(sigblob);
1a92bd7e	156	return -1;
1a92bd7e	157	}
fa08c86b	158	EVP_DigestInit(&md, evp_md);
fa08c86b	159	EVP_DigestUpdate(&md, data, datalen);
087dea86	160	EVP_DigestFinal(&md, digest, &dlen);
fa08c86b	161
0caf874a	162	ret = openssh_RSA_verify(nid, digest, dlen, sigblob, len, key->rsa);
087dea86	163	memset(digest, 'd', sizeof(digest));
fa08c86b	164	memset(sigblob, 's', len);
fa08c86b	165	xfree(sigblob);
fa08c86b	166	debug("ssh_rsa_verify: signature %scorrect", (ret==0) ? "in" : "");
	167	return ret;
	168	}
0caf874a	169
	170	/*
	171	* See:
	172	* http://www.rsasecurity.com/rsalabs/pkcs/pkcs-1/
	173	* ftp://ftp.rsasecurity.com/pub/pkcs/pkcs-1/pkcs-1v2-1.asn
	174	*/
	175	/*
	176	* id-sha1 OBJECT IDENTIFIER ::= { iso(1) identified-organization(3)
	177	* oiw(14) secsig(3) algorithms(2) 26 }
	178	*/
	179	static const u_char id_sha1[] = {
	180	0x30, 0x21, /* type Sequence, length 0x21 (33) */
	181	0x30, 0x09, /* type Sequence, length 0x09 */
	182	0x06, 0x05, /* type OID, length 0x05 */
	183	0x2b, 0x0e, 0x03, 0x02, 0x1a, /* id-sha1 OID */
	184	0x05, 0x00, /* NULL */
	185	0x04, 0x14 /* Octet string, length 0x14 (20), followed by sha1 hash */
	186	};
	187	/*
	188	* id-md5 OBJECT IDENTIFIER ::= { iso(1) member-body(2) us(840)
	189	* rsadsi(113549) digestAlgorithm(2) 5 }
	190	*/
	191	static const u_char id_md5[] = {
	192	0x30, 0x20, /* type Sequence, length 0x20 (32) */
	193	0x30, 0x0c, /* type Sequence, length 0x09 */
	194	0x06, 0x08, /* type OID, length 0x05 */
	195	0x2a, 0x86, 0x48, 0x86, 0xF7, 0x0D, 0x02, 0x05, /* id-md5 */
	196	0x05, 0x00, /* NULL */
	197	0x04, 0x10 /* Octet string, length 0x10 (16), followed by md5 hash */
	198	};
	199
	200	static int
	201	openssh_RSA_verify(int type, u_char *hash, u_int hashlen,
	202	u_char sigbuf, u_int siglen, RSA rsa)
	203	{
b41baf4d	204	u_int ret, rsasize, oidlen = 0, hlen = 0;
b41baf4d	205	int len;
0caf874a	206	const u_char *oid = NULL;
	207	u_char *decrypted = NULL;
	208
	209	ret = 0;
	210	switch (type) {
	211	case NID_sha1:
	212	oid = id_sha1;
	213	oidlen = sizeof(id_sha1);
	214	hlen = 20;
	215	break;
	216	case NID_md5:
	217	oid = id_md5;
	218	oidlen = sizeof(id_md5);
	219	hlen = 16;
	220	break;
	221	default:
	222	goto done;
	223	break;
	224	}
	225	if (hashlen != hlen) {
	226	error("bad hashlen");
	227	goto done;
	228	}
	229	rsasize = RSA_size(rsa);
	230	if (siglen == 0 \|\| siglen > rsasize) {
	231	error("bad siglen");
	232	goto done;
	233	}
	234	decrypted = xmalloc(rsasize);
	235	if ((len = RSA_public_decrypt(siglen, sigbuf, decrypted, rsa,
	236	RSA_PKCS1_PADDING)) < 0) {
	237	error("RSA_public_decrypt failed: %s",
	238	ERR_error_string(ERR_get_error(), NULL));
	239	goto done;
	240	}
c1ffd4bd	241	if (len != hlen + oidlen) {
c1ffd4bd	242	error("bad decrypted len: %d != %d + %d", len, hlen, oidlen);
0caf874a	243	goto done;
	244	}
	245	if (memcmp(decrypted, oid, oidlen) != 0) {
	246	error("oid mismatch");
	247	goto done;
	248	}
	249	if (memcmp(decrypted + oidlen, hash, hlen) != 0) {
	250	error("hash mismatch");
	251	goto done;
	252	}
	253	ret = 1;
	254	done:
	255	if (decrypted)
	256	xfree(decrypted);
	257	return ret;
	258	}