260 lines
6.6 KiB
C
260 lines
6.6 KiB
C
/* $OpenBSD: ssh-rsa.c,v 1.50 2014/01/09 23:20:00 djm 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 "misc.h"
|
|
#include "ssh.h"
|
|
#include "digest.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)
|
|
{
|
|
int hash_alg;
|
|
u_char digest[SSH_DIGEST_MAX_LENGTH], *sig;
|
|
u_int slen, dlen, len;
|
|
int ok, nid;
|
|
Buffer b;
|
|
|
|
if (key == NULL || key_type_plain(key->type) != KEY_RSA ||
|
|
key->rsa == NULL) {
|
|
error("%s: no RSA key", __func__);
|
|
return -1;
|
|
}
|
|
|
|
/* hash the data */
|
|
hash_alg = SSH_DIGEST_SHA1;
|
|
nid = NID_sha1;
|
|
if ((dlen = ssh_digest_bytes(hash_alg)) == 0) {
|
|
error("%s: bad hash algorithm %d", __func__, hash_alg);
|
|
return -1;
|
|
}
|
|
if (ssh_digest_memory(hash_alg, data, datalen,
|
|
digest, sizeof(digest)) != 0) {
|
|
error("%s: ssh_digest_memory failed", __func__);
|
|
return -1;
|
|
}
|
|
|
|
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("%s: RSA_sign failed: %s", __func__,
|
|
ERR_error_string(ecode, NULL));
|
|
free(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("%s: slen %u slen2 %u", __func__, slen, len);
|
|
free(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);
|
|
free(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;
|
|
int hash_alg;
|
|
char *ktype;
|
|
u_char digest[SSH_DIGEST_MAX_LENGTH], *sigblob;
|
|
u_int len, dlen, modlen;
|
|
int rlen, ret;
|
|
|
|
if (key == NULL || key_type_plain(key->type) != KEY_RSA ||
|
|
key->rsa == NULL) {
|
|
error("%s: no RSA key", __func__);
|
|
return -1;
|
|
}
|
|
|
|
if (BN_num_bits(key->rsa->n) < SSH_RSA_MINIMUM_MODULUS_SIZE) {
|
|
error("%s: RSA modulus too small: %d < minimum %d bits",
|
|
__func__, BN_num_bits(key->rsa->n),
|
|
SSH_RSA_MINIMUM_MODULUS_SIZE);
|
|
return -1;
|
|
}
|
|
buffer_init(&b);
|
|
buffer_append(&b, signature, signaturelen);
|
|
ktype = buffer_get_cstring(&b, NULL);
|
|
if (strcmp("ssh-rsa", ktype) != 0) {
|
|
error("%s: cannot handle type %s", __func__, ktype);
|
|
buffer_free(&b);
|
|
free(ktype);
|
|
return -1;
|
|
}
|
|
free(ktype);
|
|
sigblob = buffer_get_string(&b, &len);
|
|
rlen = buffer_len(&b);
|
|
buffer_free(&b);
|
|
if (rlen != 0) {
|
|
error("%s: remaining bytes in signature %d", __func__, rlen);
|
|
free(sigblob);
|
|
return -1;
|
|
}
|
|
/* RSA_verify expects a signature of RSA_size */
|
|
modlen = RSA_size(key->rsa);
|
|
if (len > modlen) {
|
|
error("%s: len %u > modlen %u", __func__, len, modlen);
|
|
free(sigblob);
|
|
return -1;
|
|
} else if (len < modlen) {
|
|
u_int diff = modlen - len;
|
|
debug("%s: add padding: modlen %u > len %u", __func__,
|
|
modlen, len);
|
|
sigblob = xrealloc(sigblob, 1, modlen);
|
|
memmove(sigblob + diff, sigblob, len);
|
|
memset(sigblob, 0, diff);
|
|
len = modlen;
|
|
}
|
|
/* hash the data */
|
|
hash_alg = SSH_DIGEST_SHA1;
|
|
if ((dlen = ssh_digest_bytes(hash_alg)) == 0) {
|
|
error("%s: bad hash algorithm %d", __func__, hash_alg);
|
|
return -1;
|
|
}
|
|
if (ssh_digest_memory(hash_alg, data, datalen,
|
|
digest, sizeof(digest)) != 0) {
|
|
error("%s: ssh_digest_memory failed", __func__);
|
|
return -1;
|
|
}
|
|
|
|
ret = openssh_RSA_verify(hash_alg, digest, dlen, sigblob, len,
|
|
key->rsa);
|
|
memset(digest, 'd', sizeof(digest));
|
|
memset(sigblob, 's', len);
|
|
free(sigblob);
|
|
debug("%s: signature %scorrect", __func__, (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 */
|
|
};
|
|
|
|
static int
|
|
openssh_RSA_verify(int hash_alg, u_char *hash, u_int hashlen,
|
|
u_char *sigbuf, u_int siglen, RSA *rsa)
|
|
{
|
|
u_int ret, rsasize, oidlen = 0, hlen = 0;
|
|
int len, oidmatch, hashmatch;
|
|
const u_char *oid = NULL;
|
|
u_char *decrypted = NULL;
|
|
|
|
ret = 0;
|
|
switch (hash_alg) {
|
|
case SSH_DIGEST_SHA1:
|
|
oid = id_sha1;
|
|
oidlen = sizeof(id_sha1);
|
|
hlen = 20;
|
|
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;
|
|
}
|
|
oidmatch = timingsafe_bcmp(decrypted, oid, oidlen) == 0;
|
|
hashmatch = timingsafe_bcmp(decrypted + oidlen, hash, hlen) == 0;
|
|
if (!oidmatch) {
|
|
error("oid mismatch");
|
|
goto done;
|
|
}
|
|
if (!hashmatch) {
|
|
error("hash mismatch");
|
|
goto done;
|
|
}
|
|
ret = 1;
|
|
done:
|
|
free(decrypted);
|
|
return ret;
|
|
}
|