You can not select more than 25 topics
Topics must start with a letter or number, can include dashes ('-') and can be up to 35 characters long.
220 lines
7.1 KiB
220 lines
7.1 KiB
/* $OpenBSD: kexsntrup4591761x25519.c,v 1.3 2019/01/21 10:40:11 djm Exp $ */
|
|
/*
|
|
* Copyright (c) 2019 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"
|
|
|
|
#include <sys/types.h>
|
|
|
|
#include <stdio.h>
|
|
#include <string.h>
|
|
#include <signal.h>
|
|
|
|
#include "sshkey.h"
|
|
#include "kex.h"
|
|
#include "sshbuf.h"
|
|
#include "digest.h"
|
|
#include "ssherr.h"
|
|
|
|
int
|
|
kex_kem_sntrup4591761x25519_keypair(struct kex *kex)
|
|
{
|
|
struct sshbuf *buf = NULL;
|
|
u_char *cp = NULL;
|
|
size_t need;
|
|
int r;
|
|
|
|
if ((buf = sshbuf_new()) == NULL)
|
|
return SSH_ERR_ALLOC_FAIL;
|
|
need = crypto_kem_sntrup4591761_PUBLICKEYBYTES + CURVE25519_SIZE;
|
|
if ((r = sshbuf_reserve(buf, need, &cp)) != 0)
|
|
goto out;
|
|
crypto_kem_sntrup4591761_keypair(cp, kex->sntrup4591761_client_key);
|
|
#ifdef DEBUG_KEXECDH
|
|
dump_digest("client public key sntrup4591761:", cp,
|
|
crypto_kem_sntrup4591761_PUBLICKEYBYTES);
|
|
#endif
|
|
cp += crypto_kem_sntrup4591761_PUBLICKEYBYTES;
|
|
kexc25519_keygen(kex->c25519_client_key, cp);
|
|
#ifdef DEBUG_KEXECDH
|
|
dump_digest("client public key c25519:", cp, CURVE25519_SIZE);
|
|
#endif
|
|
kex->client_pub = buf;
|
|
buf = NULL;
|
|
out:
|
|
sshbuf_free(buf);
|
|
return r;
|
|
}
|
|
|
|
int
|
|
kex_kem_sntrup4591761x25519_enc(struct kex *kex,
|
|
const struct sshbuf *client_blob, struct sshbuf **server_blobp,
|
|
struct sshbuf **shared_secretp)
|
|
{
|
|
struct sshbuf *server_blob = NULL;
|
|
struct sshbuf *buf = NULL;
|
|
const u_char *client_pub;
|
|
u_char *kem_key, *ciphertext, *server_pub;
|
|
u_char server_key[CURVE25519_SIZE];
|
|
u_char hash[SSH_DIGEST_MAX_LENGTH];
|
|
size_t need;
|
|
int r;
|
|
|
|
*server_blobp = NULL;
|
|
*shared_secretp = NULL;
|
|
|
|
/* client_blob contains both KEM and ECDH client pubkeys */
|
|
need = crypto_kem_sntrup4591761_PUBLICKEYBYTES + CURVE25519_SIZE;
|
|
if (sshbuf_len(client_blob) != need) {
|
|
r = SSH_ERR_SIGNATURE_INVALID;
|
|
goto out;
|
|
}
|
|
client_pub = sshbuf_ptr(client_blob);
|
|
#ifdef DEBUG_KEXECDH
|
|
dump_digest("client public key sntrup4591761:", client_pub,
|
|
crypto_kem_sntrup4591761_PUBLICKEYBYTES);
|
|
dump_digest("client public key 25519:",
|
|
client_pub + crypto_kem_sntrup4591761_PUBLICKEYBYTES,
|
|
CURVE25519_SIZE);
|
|
#endif
|
|
/* allocate buffer for concatenation of KEM key and ECDH shared key */
|
|
/* the buffer will be hashed and the result is the shared secret */
|
|
if ((buf = sshbuf_new()) == NULL) {
|
|
r = SSH_ERR_ALLOC_FAIL;
|
|
goto out;
|
|
}
|
|
if ((r = sshbuf_reserve(buf, crypto_kem_sntrup4591761_BYTES,
|
|
&kem_key)) != 0)
|
|
goto out;
|
|
/* allocate space for encrypted KEM key and ECDH pub key */
|
|
if ((server_blob = sshbuf_new()) == NULL) {
|
|
r = SSH_ERR_ALLOC_FAIL;
|
|
goto out;
|
|
}
|
|
need = crypto_kem_sntrup4591761_CIPHERTEXTBYTES + CURVE25519_SIZE;
|
|
if ((r = sshbuf_reserve(server_blob, need, &ciphertext)) != 0)
|
|
goto out;
|
|
/* generate and encrypt KEM key with client key */
|
|
crypto_kem_sntrup4591761_enc(ciphertext, kem_key, client_pub);
|
|
/* generate ECDH key pair, store server pubkey after ciphertext */
|
|
server_pub = ciphertext + crypto_kem_sntrup4591761_CIPHERTEXTBYTES;
|
|
kexc25519_keygen(server_key, server_pub);
|
|
/* append ECDH shared key */
|
|
client_pub += crypto_kem_sntrup4591761_PUBLICKEYBYTES;
|
|
if ((r = kexc25519_shared_key_ext(server_key, client_pub, buf, 1)) < 0)
|
|
goto out;
|
|
if ((r = ssh_digest_buffer(kex->hash_alg, buf, hash, sizeof(hash))) != 0)
|
|
goto out;
|
|
#ifdef DEBUG_KEXECDH
|
|
dump_digest("server public key 25519:", server_pub, CURVE25519_SIZE);
|
|
dump_digest("server cipher text:", ciphertext,
|
|
crypto_kem_sntrup4591761_CIPHERTEXTBYTES);
|
|
dump_digest("server kem key:", kem_key, sizeof(kem_key));
|
|
dump_digest("concatenation of KEM key and ECDH shared key:",
|
|
sshbuf_ptr(buf), sshbuf_len(buf));
|
|
#endif
|
|
/* string-encoded hash is resulting shared secret */
|
|
sshbuf_reset(buf);
|
|
if ((r = sshbuf_put_string(buf, hash,
|
|
ssh_digest_bytes(kex->hash_alg))) != 0)
|
|
goto out;
|
|
#ifdef DEBUG_KEXECDH
|
|
dump_digest("encoded shared secret:", sshbuf_ptr(buf), sshbuf_len(buf));
|
|
#endif
|
|
*server_blobp = server_blob;
|
|
*shared_secretp = buf;
|
|
server_blob = NULL;
|
|
buf = NULL;
|
|
out:
|
|
explicit_bzero(hash, sizeof(hash));
|
|
explicit_bzero(server_key, sizeof(server_key));
|
|
sshbuf_free(server_blob);
|
|
sshbuf_free(buf);
|
|
return r;
|
|
}
|
|
|
|
int
|
|
kex_kem_sntrup4591761x25519_dec(struct kex *kex,
|
|
const struct sshbuf *server_blob, struct sshbuf **shared_secretp)
|
|
{
|
|
struct sshbuf *buf = NULL;
|
|
u_char *kem_key = NULL;
|
|
const u_char *ciphertext, *server_pub;
|
|
u_char hash[SSH_DIGEST_MAX_LENGTH];
|
|
size_t need;
|
|
int r, decoded;
|
|
|
|
*shared_secretp = NULL;
|
|
|
|
need = crypto_kem_sntrup4591761_CIPHERTEXTBYTES + CURVE25519_SIZE;
|
|
if (sshbuf_len(server_blob) != need) {
|
|
r = SSH_ERR_SIGNATURE_INVALID;
|
|
goto out;
|
|
}
|
|
ciphertext = sshbuf_ptr(server_blob);
|
|
server_pub = ciphertext + crypto_kem_sntrup4591761_CIPHERTEXTBYTES;
|
|
#ifdef DEBUG_KEXECDH
|
|
dump_digest("server cipher text:", ciphertext,
|
|
crypto_kem_sntrup4591761_CIPHERTEXTBYTES);
|
|
dump_digest("server public key c25519:", server_pub, CURVE25519_SIZE);
|
|
#endif
|
|
/* hash concatenation of KEM key and ECDH shared key */
|
|
if ((buf = sshbuf_new()) == NULL) {
|
|
r = SSH_ERR_ALLOC_FAIL;
|
|
goto out;
|
|
}
|
|
if ((r = sshbuf_reserve(buf, crypto_kem_sntrup4591761_BYTES,
|
|
&kem_key)) != 0)
|
|
goto out;
|
|
decoded = crypto_kem_sntrup4591761_dec(kem_key, ciphertext,
|
|
kex->sntrup4591761_client_key);
|
|
if ((r = kexc25519_shared_key_ext(kex->c25519_client_key, server_pub,
|
|
buf, 1)) < 0)
|
|
goto out;
|
|
if ((r = ssh_digest_buffer(kex->hash_alg, buf, hash, sizeof(hash))) != 0)
|
|
goto out;
|
|
#ifdef DEBUG_KEXECDH
|
|
dump_digest("client kem key:", kem_key, sizeof(kem_key));
|
|
dump_digest("concatenation of KEM key and ECDH shared key:",
|
|
sshbuf_ptr(buf), sshbuf_len(buf));
|
|
#endif
|
|
sshbuf_reset(buf);
|
|
if ((r = sshbuf_put_string(buf, hash,
|
|
ssh_digest_bytes(kex->hash_alg))) != 0)
|
|
goto out;
|
|
#ifdef DEBUG_KEXECDH
|
|
dump_digest("encoded shared secret:", sshbuf_ptr(buf), sshbuf_len(buf));
|
|
#endif
|
|
if (decoded != 0) {
|
|
r = SSH_ERR_SIGNATURE_INVALID;
|
|
goto out;
|
|
}
|
|
*shared_secretp = buf;
|
|
buf = NULL;
|
|
out:
|
|
explicit_bzero(hash, sizeof(hash));
|
|
sshbuf_free(buf);
|
|
return r;
|
|
}
|