| /* $OpenBSD: kexc25519.c,v 1.12 2019/01/21 09:49:37 djm Exp $ */ |
| /* |
| * Copyright (c) 2001, 2013 Markus Friedl. All rights reserved. |
| * Copyright (c) 2010 Damien Miller. All rights reserved. |
| * Copyright (c) 2013 Aris Adamantiadis. 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 <signal.h> |
| #include <string.h> |
| |
| #include <openssl/bn.h> |
| #include <openssl/evp.h> |
| |
| #include "sshbuf.h" |
| #include "ssh2.h" |
| #include "sshkey.h" |
| #include "cipher.h" |
| #include "kex.h" |
| #include "log.h" |
| #include "digest.h" |
| #include "ssherr.h" |
| |
| extern int crypto_scalarmult_curve25519(u_char a[CURVE25519_SIZE], |
| const u_char b[CURVE25519_SIZE], const u_char c[CURVE25519_SIZE]) |
| __attribute__((__bounded__(__minbytes__, 1, CURVE25519_SIZE))) |
| __attribute__((__bounded__(__minbytes__, 2, CURVE25519_SIZE))) |
| __attribute__((__bounded__(__minbytes__, 3, CURVE25519_SIZE))); |
| |
| void |
| kexc25519_keygen(u_char key[CURVE25519_SIZE], u_char pub[CURVE25519_SIZE]) |
| { |
| static const u_char basepoint[CURVE25519_SIZE] = {9}; |
| |
| arc4random_buf(key, CURVE25519_SIZE); |
| crypto_scalarmult_curve25519(pub, key, basepoint); |
| } |
| |
| int |
| kexc25519_shared_key(const u_char key[CURVE25519_SIZE], |
| const u_char pub[CURVE25519_SIZE], struct sshbuf *out) |
| { |
| u_char shared_key[CURVE25519_SIZE]; |
| u_char zero[CURVE25519_SIZE]; |
| int r; |
| |
| crypto_scalarmult_curve25519(shared_key, key, pub); |
| |
| /* Check for all-zero shared secret */ |
| explicit_bzero(zero, CURVE25519_SIZE); |
| if (timingsafe_bcmp(zero, shared_key, CURVE25519_SIZE) == 0) |
| return SSH_ERR_KEY_INVALID_EC_VALUE; |
| |
| #ifdef DEBUG_KEXECDH |
| dump_digest("shared secret", shared_key, CURVE25519_SIZE); |
| #endif |
| sshbuf_reset(out); |
| r = sshbuf_put_bignum2_bytes(out, shared_key, CURVE25519_SIZE); |
| explicit_bzero(shared_key, CURVE25519_SIZE); |
| return r; |
| } |
| |
| int |
| kex_c25519_hash( |
| int hash_alg, |
| const struct sshbuf *client_version, |
| const struct sshbuf *server_version, |
| const u_char *ckexinit, size_t ckexinitlen, |
| const u_char *skexinit, size_t skexinitlen, |
| const u_char *serverhostkeyblob, size_t sbloblen, |
| const u_char client_dh_pub[CURVE25519_SIZE], |
| const u_char server_dh_pub[CURVE25519_SIZE], |
| const u_char *shared_secret, size_t secretlen, |
| u_char *hash, size_t *hashlen) |
| { |
| struct sshbuf *b; |
| int r; |
| |
| if (*hashlen < ssh_digest_bytes(hash_alg)) |
| return SSH_ERR_INVALID_ARGUMENT; |
| if ((b = sshbuf_new()) == NULL) |
| return SSH_ERR_ALLOC_FAIL; |
| if ((r = sshbuf_put_stringb(b, client_version)) < 0 || |
| (r = sshbuf_put_stringb(b, server_version)) < 0 || |
| /* kexinit messages: fake header: len+SSH2_MSG_KEXINIT */ |
| (r = sshbuf_put_u32(b, ckexinitlen+1)) < 0 || |
| (r = sshbuf_put_u8(b, SSH2_MSG_KEXINIT)) < 0 || |
| (r = sshbuf_put(b, ckexinit, ckexinitlen)) < 0 || |
| (r = sshbuf_put_u32(b, skexinitlen+1)) < 0 || |
| (r = sshbuf_put_u8(b, SSH2_MSG_KEXINIT)) < 0 || |
| (r = sshbuf_put(b, skexinit, skexinitlen)) < 0 || |
| (r = sshbuf_put_string(b, serverhostkeyblob, sbloblen)) < 0 || |
| (r = sshbuf_put_string(b, client_dh_pub, CURVE25519_SIZE)) < 0 || |
| (r = sshbuf_put_string(b, server_dh_pub, CURVE25519_SIZE)) < 0 || |
| (r = sshbuf_put(b, shared_secret, secretlen)) < 0) { |
| sshbuf_free(b); |
| return r; |
| } |
| #ifdef DEBUG_KEX |
| sshbuf_dump(b, stderr); |
| #endif |
| if (ssh_digest_buffer(hash_alg, b, hash, *hashlen) != 0) { |
| sshbuf_free(b); |
| return SSH_ERR_LIBCRYPTO_ERROR; |
| } |
| sshbuf_free(b); |
| *hashlen = ssh_digest_bytes(hash_alg); |
| #ifdef DEBUG_KEX |
| dump_digest("hash", hash, *hashlen); |
| #endif |
| return 0; |
| } |