/* $OpenBSD: kexc25519.c,v 1.10 2016/05/02 08:49:03 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 <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]; int r; /* Check for all-zero public key */ explicit_bzero(shared_key, CURVE25519_SIZE); if (timingsafe_bcmp(pub, shared_key, CURVE25519_SIZE) == 0) return SSH_ERR_KEY_INVALID_EC_VALUE; crypto_scalarmult_curve25519(shared_key, key, pub); #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 char *client_version_string, const char *server_version_string, 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_cstring(b, client_version_string)) < 0 || (r = sshbuf_put_cstring(b, server_version_string)) < 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; }