~ubuntu-branches/ubuntu/lucid/openssh/lucid

/* $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;

}