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/* $OpenBSD: ssh-ecdsa.c,v 1.14 2018/02/07 02:06:51 jsing Exp $ */
/*
* Copyright (c) 2000 Markus Friedl. All rights reserved.
* Copyright (c) 2010 Damien Miller. 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"
#if defined(WITH_OPENSSL) && defined(OPENSSL_HAS_ECC)
#include <sys/types.h>
#include <openssl/bn.h>
#include <openssl/ec.h>
#include <openssl/ecdsa.h>
#include <openssl/evp.h>
#include <string.h>
#include "sshbuf.h"
#include "ssherr.h"
#include "digest.h"
#define SSHKEY_INTERNAL
#include "sshkey.h"
#include "openbsd-compat/openssl-compat.h"
/* ARGSUSED */
int
ssh_ecdsa_sign(const struct sshkey *key, u_char **sigp, size_t *lenp,
const u_char *data, size_t datalen, u_int compat)
{
ECDSA_SIG *sig = NULL;
const BIGNUM *sig_r, *sig_s;
int hash_alg;
u_char digest[SSH_DIGEST_MAX_LENGTH];
size_t len, dlen;
struct sshbuf *b = NULL, *bb = NULL;
int ret = SSH_ERR_INTERNAL_ERROR;
if (lenp != NULL)
*lenp = 0;
if (sigp != NULL)
*sigp = NULL;
if (key == NULL || key->ecdsa == NULL ||
sshkey_type_plain(key->type) != KEY_ECDSA)
return SSH_ERR_INVALID_ARGUMENT;
if ((hash_alg = sshkey_ec_nid_to_hash_alg(key->ecdsa_nid)) == -1 ||
(dlen = ssh_digest_bytes(hash_alg)) == 0)
return SSH_ERR_INTERNAL_ERROR;
if ((ret = ssh_digest_memory(hash_alg, data, datalen,
digest, sizeof(digest))) != 0)
goto out;
if ((sig = ECDSA_do_sign(digest, dlen, key->ecdsa)) == NULL) {
ret = SSH_ERR_LIBCRYPTO_ERROR;
goto out;
}
if ((bb = sshbuf_new()) == NULL || (b = sshbuf_new()) == NULL) {
ret = SSH_ERR_ALLOC_FAIL;
goto out;
}
ECDSA_SIG_get0(sig, &sig_r, &sig_s);
if ((ret = sshbuf_put_bignum2(bb, sig_r)) != 0 ||
(ret = sshbuf_put_bignum2(bb, sig_s)) != 0)
goto out;
if ((ret = sshbuf_put_cstring(b, sshkey_ssh_name_plain(key))) != 0 ||
(ret = sshbuf_put_stringb(b, bb)) != 0)
goto out;
len = sshbuf_len(b);
if (sigp != NULL) {
if ((*sigp = malloc(len)) == NULL) {
ret = SSH_ERR_ALLOC_FAIL;
goto out;
}
memcpy(*sigp, sshbuf_ptr(b), len);
}
if (lenp != NULL)
*lenp = len;
ret = 0;
out:
explicit_bzero(digest, sizeof(digest));
sshbuf_free(b);
sshbuf_free(bb);
ECDSA_SIG_free(sig);
return ret;
}
/* ARGSUSED */
int
ssh_ecdsa_verify(const struct sshkey *key,
const u_char *signature, size_t signaturelen,
const u_char *data, size_t datalen, u_int compat)
{
ECDSA_SIG *sig = NULL;
BIGNUM *sig_r = NULL, *sig_s = NULL;
int hash_alg;
u_char digest[SSH_DIGEST_MAX_LENGTH];
size_t dlen;
int ret = SSH_ERR_INTERNAL_ERROR;
struct sshbuf *b = NULL, *sigbuf = NULL;
char *ktype = NULL;
if (key == NULL || key->ecdsa == NULL ||
sshkey_type_plain(key->type) != KEY_ECDSA ||
signature == NULL || signaturelen == 0)
return SSH_ERR_INVALID_ARGUMENT;
if ((hash_alg = sshkey_ec_nid_to_hash_alg(key->ecdsa_nid)) == -1 ||
(dlen = ssh_digest_bytes(hash_alg)) == 0)
return SSH_ERR_INTERNAL_ERROR;
/* fetch signature */
if ((b = sshbuf_from(signature, signaturelen)) == NULL)
return SSH_ERR_ALLOC_FAIL;
if (sshbuf_get_cstring(b, &ktype, NULL) != 0 ||
sshbuf_froms(b, &sigbuf) != 0) {
ret = SSH_ERR_INVALID_FORMAT;
goto out;
}
if (strcmp(sshkey_ssh_name_plain(key), ktype) != 0) {
ret = SSH_ERR_KEY_TYPE_MISMATCH;
goto out;
}
if (sshbuf_len(b) != 0) {
ret = SSH_ERR_UNEXPECTED_TRAILING_DATA;
goto out;
}
/* parse signature */
if ((sig = ECDSA_SIG_new()) == NULL ||
(sig_r = BN_new()) == NULL ||
(sig_s = BN_new()) == NULL) {
ret = SSH_ERR_ALLOC_FAIL;
goto out;
}
if (sshbuf_get_bignum2(sigbuf, sig_r) != 0 ||
sshbuf_get_bignum2(sigbuf, sig_s) != 0) {
ret = SSH_ERR_INVALID_FORMAT;
goto out;
}
if (!ECDSA_SIG_set0(sig, sig_r, sig_s)) {
ret = SSH_ERR_LIBCRYPTO_ERROR;
goto out;
}
sig_r = sig_s = NULL; /* transferred */
if (sshbuf_len(sigbuf) != 0) {
ret = SSH_ERR_UNEXPECTED_TRAILING_DATA;
goto out;
}
if ((ret = ssh_digest_memory(hash_alg, data, datalen,
digest, sizeof(digest))) != 0)
goto out;
switch (ECDSA_do_verify(digest, dlen, sig, key->ecdsa)) {
case 1:
ret = 0;
break;
case 0:
ret = SSH_ERR_SIGNATURE_INVALID;
goto out;
default:
ret = SSH_ERR_LIBCRYPTO_ERROR;
goto out;
}
out:
explicit_bzero(digest, sizeof(digest));
sshbuf_free(sigbuf);
sshbuf_free(b);
ECDSA_SIG_free(sig);
BN_clear_free(sig_r);
BN_clear_free(sig_s);
free(ktype);
return ret;
}
#endif /* WITH_OPENSSL && OPENSSL_HAS_ECC */
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