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openssh-portable/ssh-dss.c

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/* $OpenBSD: ssh-dss.c,v 1.48 2022/10/28 00:44:44 djm Exp $ */
/*
* Copyright (c) 2000 Markus Friedl. 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"
#ifdef WITH_OPENSSL
#include <sys/types.h>
#include <openssl/bn.h>
#include <openssl/dsa.h>
#include <openssl/evp.h>
#include <stdarg.h>
#include <string.h>
#include "sshbuf.h"
#include "compat.h"
#include "ssherr.h"
#include "digest.h"
#define SSHKEY_INTERNAL
#include "sshkey.h"
#include "openbsd-compat/openssl-compat.h"
#define INTBLOB_LEN 20
#define SIGBLOB_LEN (2*INTBLOB_LEN)
static u_int
ssh_dss_size(const struct sshkey *key)
{
const BIGNUM *dsa_p;
if (key->dsa == NULL)
return 0;
DSA_get0_pqg(key->dsa, &dsa_p, NULL, NULL);
return BN_num_bits(dsa_p);
}
static int
ssh_dss_alloc(struct sshkey *k)
{
if ((k->dsa = DSA_new()) == NULL)
return SSH_ERR_ALLOC_FAIL;
return 0;
}
static void
ssh_dss_cleanup(struct sshkey *k)
{
DSA_free(k->dsa);
k->dsa = NULL;
}
static int
ssh_dss_equal(const struct sshkey *a, const struct sshkey *b)
{
const BIGNUM *dsa_p_a, *dsa_q_a, *dsa_g_a, *dsa_pub_key_a;
const BIGNUM *dsa_p_b, *dsa_q_b, *dsa_g_b, *dsa_pub_key_b;
if (a->dsa == NULL || b->dsa == NULL)
return 0;
DSA_get0_pqg(a->dsa, &dsa_p_a, &dsa_q_a, &dsa_g_a);
DSA_get0_pqg(b->dsa, &dsa_p_b, &dsa_q_b, &dsa_g_b);
DSA_get0_key(a->dsa, &dsa_pub_key_a, NULL);
DSA_get0_key(b->dsa, &dsa_pub_key_b, NULL);
if (dsa_p_a == NULL || dsa_p_b == NULL ||
dsa_q_a == NULL || dsa_q_b == NULL ||
dsa_g_a == NULL || dsa_g_b == NULL ||
dsa_pub_key_a == NULL || dsa_pub_key_b == NULL)
return 0;
if (BN_cmp(dsa_p_a, dsa_p_b) != 0)
return 0;
if (BN_cmp(dsa_q_a, dsa_q_b) != 0)
return 0;
if (BN_cmp(dsa_g_a, dsa_g_b) != 0)
return 0;
if (BN_cmp(dsa_pub_key_a, dsa_pub_key_b) != 0)
return 0;
return 1;
}
static int
ssh_dss_serialize_public(const struct sshkey *key, struct sshbuf *b,
enum sshkey_serialize_rep opts)
{
int r;
const BIGNUM *dsa_p, *dsa_q, *dsa_g, *dsa_pub_key;
if (key->dsa == NULL)
return SSH_ERR_INVALID_ARGUMENT;
DSA_get0_pqg(key->dsa, &dsa_p, &dsa_q, &dsa_g);
DSA_get0_key(key->dsa, &dsa_pub_key, NULL);
if (dsa_p == NULL || dsa_q == NULL ||
dsa_g == NULL || dsa_pub_key == NULL)
return SSH_ERR_INTERNAL_ERROR;
if ((r = sshbuf_put_bignum2(b, dsa_p)) != 0 ||
(r = sshbuf_put_bignum2(b, dsa_q)) != 0 ||
(r = sshbuf_put_bignum2(b, dsa_g)) != 0 ||
(r = sshbuf_put_bignum2(b, dsa_pub_key)) != 0)
return r;
return 0;
}
static int
ssh_dss_serialize_private(const struct sshkey *key, struct sshbuf *b,
enum sshkey_serialize_rep opts)
{
int r;
const BIGNUM *dsa_priv_key;
DSA_get0_key(key->dsa, NULL, &dsa_priv_key);
if (!sshkey_is_cert(key)) {
if ((r = ssh_dss_serialize_public(key, b, opts)) != 0)
return r;
}
if ((r = sshbuf_put_bignum2(b, dsa_priv_key)) != 0)
return r;
return 0;
}
static int
ssh_dss_generate(struct sshkey *k, int bits)
{
DSA *private;
if (bits != 1024)
return SSH_ERR_KEY_LENGTH;
if ((private = DSA_new()) == NULL)
return SSH_ERR_ALLOC_FAIL;
if (!DSA_generate_parameters_ex(private, bits, NULL, 0, NULL,
NULL, NULL) || !DSA_generate_key(private)) {
DSA_free(private);
return SSH_ERR_LIBCRYPTO_ERROR;
}
k->dsa = private;
return 0;
}
static int
ssh_dss_copy_public(const struct sshkey *from, struct sshkey *to)
{
const BIGNUM *dsa_p, *dsa_q, *dsa_g, *dsa_pub_key;
BIGNUM *dsa_p_dup = NULL, *dsa_q_dup = NULL, *dsa_g_dup = NULL;
BIGNUM *dsa_pub_key_dup = NULL;
int r = SSH_ERR_INTERNAL_ERROR;
DSA_get0_pqg(from->dsa, &dsa_p, &dsa_q, &dsa_g);
DSA_get0_key(from->dsa, &dsa_pub_key, NULL);
if ((dsa_p_dup = BN_dup(dsa_p)) == NULL ||
(dsa_q_dup = BN_dup(dsa_q)) == NULL ||
(dsa_g_dup = BN_dup(dsa_g)) == NULL ||
(dsa_pub_key_dup = BN_dup(dsa_pub_key)) == NULL) {
r = SSH_ERR_ALLOC_FAIL;
goto out;
}
if (!DSA_set0_pqg(to->dsa, dsa_p_dup, dsa_q_dup, dsa_g_dup)) {
r = SSH_ERR_LIBCRYPTO_ERROR;
goto out;
}
dsa_p_dup = dsa_q_dup = dsa_g_dup = NULL; /* transferred */
if (!DSA_set0_key(to->dsa, dsa_pub_key_dup, NULL)) {
r = SSH_ERR_LIBCRYPTO_ERROR;
goto out;
}
dsa_pub_key_dup = NULL; /* transferred */
/* success */
r = 0;
out:
BN_clear_free(dsa_p_dup);
BN_clear_free(dsa_q_dup);
BN_clear_free(dsa_g_dup);
BN_clear_free(dsa_pub_key_dup);
return r;
}
static int
ssh_dss_deserialize_public(const char *ktype, struct sshbuf *b,
struct sshkey *key)
{
int ret = SSH_ERR_INTERNAL_ERROR;
BIGNUM *dsa_p = NULL, *dsa_q = NULL, *dsa_g = NULL, *dsa_pub_key = NULL;
if (sshbuf_get_bignum2(b, &dsa_p) != 0 ||
sshbuf_get_bignum2(b, &dsa_q) != 0 ||
sshbuf_get_bignum2(b, &dsa_g) != 0 ||
sshbuf_get_bignum2(b, &dsa_pub_key) != 0) {
ret = SSH_ERR_INVALID_FORMAT;
goto out;
}
if (!DSA_set0_pqg(key->dsa, dsa_p, dsa_q, dsa_g)) {
ret = SSH_ERR_LIBCRYPTO_ERROR;
goto out;
}
dsa_p = dsa_q = dsa_g = NULL; /* transferred */
if (!DSA_set0_key(key->dsa, dsa_pub_key, NULL)) {
ret = SSH_ERR_LIBCRYPTO_ERROR;
goto out;
}
dsa_pub_key = NULL; /* transferred */
#ifdef DEBUG_PK
DSA_print_fp(stderr, key->dsa, 8);
#endif
/* success */
ret = 0;
out:
BN_clear_free(dsa_p);
BN_clear_free(dsa_q);
BN_clear_free(dsa_g);
BN_clear_free(dsa_pub_key);
return ret;
}
static int
ssh_dss_deserialize_private(const char *ktype, struct sshbuf *b,
struct sshkey *key)
{
int r;
BIGNUM *dsa_priv_key = NULL;
if (!sshkey_is_cert(key)) {
if ((r = ssh_dss_deserialize_public(ktype, b, key)) != 0)
return r;
}
if ((r = sshbuf_get_bignum2(b, &dsa_priv_key)) != 0)
return r;
if (!DSA_set0_key(key->dsa, NULL, dsa_priv_key)) {
BN_clear_free(dsa_priv_key);
return SSH_ERR_LIBCRYPTO_ERROR;
}
return 0;
}
static int
ssh_dss_sign(struct sshkey *key,
u_char **sigp, size_t *lenp,
const u_char *data, size_t datalen,
const char *alg, const char *sk_provider, const char *sk_pin, u_int compat)
{
DSA_SIG *sig = NULL;
const BIGNUM *sig_r, *sig_s;
u_char digest[SSH_DIGEST_MAX_LENGTH], sigblob[SIGBLOB_LEN];
size_t rlen, slen, len, dlen = ssh_digest_bytes(SSH_DIGEST_SHA1);
struct sshbuf *b = NULL;
int ret = SSH_ERR_INVALID_ARGUMENT;
if (lenp != NULL)
*lenp = 0;
if (sigp != NULL)
*sigp = NULL;
if (key == NULL || key->dsa == NULL ||
sshkey_type_plain(key->type) != KEY_DSA)
return SSH_ERR_INVALID_ARGUMENT;
if (dlen == 0)
return SSH_ERR_INTERNAL_ERROR;
if ((ret = ssh_digest_memory(SSH_DIGEST_SHA1, data, datalen,
digest, sizeof(digest))) != 0)
goto out;
if ((sig = DSA_do_sign(digest, dlen, key->dsa)) == NULL) {
ret = SSH_ERR_LIBCRYPTO_ERROR;
goto out;
}
DSA_SIG_get0(sig, &sig_r, &sig_s);
rlen = BN_num_bytes(sig_r);
slen = BN_num_bytes(sig_s);
if (rlen > INTBLOB_LEN || slen > INTBLOB_LEN) {
ret = SSH_ERR_INTERNAL_ERROR;
goto out;
}
explicit_bzero(sigblob, SIGBLOB_LEN);
BN_bn2bin(sig_r, sigblob + SIGBLOB_LEN - INTBLOB_LEN - rlen);
BN_bn2bin(sig_s, sigblob + SIGBLOB_LEN - slen);
if ((b = sshbuf_new()) == NULL) {
ret = SSH_ERR_ALLOC_FAIL;
goto out;
}
if ((ret = sshbuf_put_cstring(b, "ssh-dss")) != 0 ||
(ret = sshbuf_put_string(b, sigblob, SIGBLOB_LEN)) != 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));
DSA_SIG_free(sig);
sshbuf_free(b);
return ret;
}
static int
ssh_dss_verify(const struct sshkey *key,
const u_char *sig, size_t siglen,
const u_char *data, size_t dlen, const char *alg, u_int compat,
struct sshkey_sig_details **detailsp)
{
DSA_SIG *dsig = NULL;
BIGNUM *sig_r = NULL, *sig_s = NULL;
u_char digest[SSH_DIGEST_MAX_LENGTH], *sigblob = NULL;
size_t len, hlen = ssh_digest_bytes(SSH_DIGEST_SHA1);
int ret = SSH_ERR_INTERNAL_ERROR;
struct sshbuf *b = NULL;
char *ktype = NULL;
if (key == NULL || key->dsa == NULL ||
sshkey_type_plain(key->type) != KEY_DSA ||
sig == NULL || siglen == 0)
return SSH_ERR_INVALID_ARGUMENT;
if (hlen == 0)
return SSH_ERR_INTERNAL_ERROR;
/* fetch signature */
if ((b = sshbuf_from(sig, siglen)) == NULL)
return SSH_ERR_ALLOC_FAIL;
if (sshbuf_get_cstring(b, &ktype, NULL) != 0 ||
sshbuf_get_string(b, &sigblob, &len) != 0) {
ret = SSH_ERR_INVALID_FORMAT;
goto out;
}
if (strcmp("ssh-dss", ktype) != 0) {
ret = SSH_ERR_KEY_TYPE_MISMATCH;
goto out;
}
if (sshbuf_len(b) != 0) {
ret = SSH_ERR_UNEXPECTED_TRAILING_DATA;
goto out;
}
if (len != SIGBLOB_LEN) {
ret = SSH_ERR_INVALID_FORMAT;
goto out;
}
/* parse signature */
if ((dsig = DSA_SIG_new()) == NULL ||
(sig_r = BN_new()) == NULL ||
(sig_s = BN_new()) == NULL) {
ret = SSH_ERR_ALLOC_FAIL;
goto out;
}
if ((BN_bin2bn(sigblob, INTBLOB_LEN, sig_r) == NULL) ||
(BN_bin2bn(sigblob + INTBLOB_LEN, INTBLOB_LEN, sig_s) == NULL)) {
ret = SSH_ERR_LIBCRYPTO_ERROR;
goto out;
}
if (!DSA_SIG_set0(dsig, sig_r, sig_s)) {
ret = SSH_ERR_LIBCRYPTO_ERROR;
goto out;
}
sig_r = sig_s = NULL; /* transferred */
/* sha1 the data */
if ((ret = ssh_digest_memory(SSH_DIGEST_SHA1, data, dlen,
digest, sizeof(digest))) != 0)
goto out;
switch (DSA_do_verify(digest, hlen, dsig, key->dsa)) {
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));
DSA_SIG_free(dsig);
BN_clear_free(sig_r);
BN_clear_free(sig_s);
sshbuf_free(b);
free(ktype);
if (sigblob != NULL)
freezero(sigblob, len);
return ret;
}
static const struct sshkey_impl_funcs sshkey_dss_funcs = {
/* .size = */ ssh_dss_size,
/* .alloc = */ ssh_dss_alloc,
/* .cleanup = */ ssh_dss_cleanup,
/* .equal = */ ssh_dss_equal,
/* .ssh_serialize_public = */ ssh_dss_serialize_public,
/* .ssh_deserialize_public = */ ssh_dss_deserialize_public,
/* .ssh_serialize_private = */ ssh_dss_serialize_private,
/* .ssh_deserialize_private = */ ssh_dss_deserialize_private,
/* .generate = */ ssh_dss_generate,
/* .copy_public = */ ssh_dss_copy_public,
/* .sign = */ ssh_dss_sign,
/* .verify = */ ssh_dss_verify,
};
const struct sshkey_impl sshkey_dss_impl = {
/* .name = */ "ssh-dss",
/* .shortname = */ "DSA",
/* .sigalg = */ NULL,
/* .type = */ KEY_DSA,
/* .nid = */ 0,
/* .cert = */ 0,
/* .sigonly = */ 0,
/* .keybits = */ 0,
/* .funcs = */ &sshkey_dss_funcs,
};
const struct sshkey_impl sshkey_dsa_cert_impl = {
/* .name = */ "ssh-dss-cert-v01@openssh.com",
/* .shortname = */ "DSA-CERT",
/* .sigalg = */ NULL,
/* .type = */ KEY_DSA_CERT,
/* .nid = */ 0,
/* .cert = */ 1,
/* .sigonly = */ 0,
/* .keybits = */ 0,
/* .funcs = */ &sshkey_dss_funcs,
};
#endif /* WITH_OPENSSL */
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