1323124Sdes/* $OpenBSD: kexc25519.c,v 1.10 2016/05/02 08:49:03 djm Exp $ */ 2261287Sdes/* 3261287Sdes * Copyright (c) 2001, 2013 Markus Friedl. All rights reserved. 4261287Sdes * Copyright (c) 2010 Damien Miller. All rights reserved. 5261287Sdes * Copyright (c) 2013 Aris Adamantiadis. All rights reserved. 6261287Sdes * 7261287Sdes * Redistribution and use in source and binary forms, with or without 8261287Sdes * modification, are permitted provided that the following conditions 9261287Sdes * are met: 10261287Sdes * 1. Redistributions of source code must retain the above copyright 11261287Sdes * notice, this list of conditions and the following disclaimer. 12261287Sdes * 2. Redistributions in binary form must reproduce the above copyright 13261287Sdes * notice, this list of conditions and the following disclaimer in the 14261287Sdes * documentation and/or other materials provided with the distribution. 15261287Sdes * 16261287Sdes * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR 17261287Sdes * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES 18261287Sdes * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. 19261287Sdes * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, 20261287Sdes * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT 21261287Sdes * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, 22261287Sdes * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY 23261287Sdes * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT 24261287Sdes * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF 25261287Sdes * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 26261287Sdes */ 27261287Sdes 28261287Sdes#include "includes.h" 29261287Sdes 30261287Sdes#include <sys/types.h> 31261287Sdes 32261287Sdes#include <signal.h> 33261287Sdes#include <string.h> 34261287Sdes 35261287Sdes#include <openssl/bn.h> 36261287Sdes#include <openssl/evp.h> 37261287Sdes 38295367Sdes#include "sshbuf.h" 39261287Sdes#include "ssh2.h" 40295367Sdes#include "sshkey.h" 41261287Sdes#include "cipher.h" 42261287Sdes#include "kex.h" 43261287Sdes#include "log.h" 44261287Sdes#include "digest.h" 45295367Sdes#include "ssherr.h" 46261287Sdes 47261287Sdesextern int crypto_scalarmult_curve25519(u_char a[CURVE25519_SIZE], 48261287Sdes const u_char b[CURVE25519_SIZE], const u_char c[CURVE25519_SIZE]) 49261287Sdes __attribute__((__bounded__(__minbytes__, 1, CURVE25519_SIZE))) 50261287Sdes __attribute__((__bounded__(__minbytes__, 2, CURVE25519_SIZE))) 51261287Sdes __attribute__((__bounded__(__minbytes__, 3, CURVE25519_SIZE))); 52261287Sdes 53261287Sdesvoid 54261287Sdeskexc25519_keygen(u_char key[CURVE25519_SIZE], u_char pub[CURVE25519_SIZE]) 55261287Sdes{ 56261287Sdes static const u_char basepoint[CURVE25519_SIZE] = {9}; 57261287Sdes 58261287Sdes arc4random_buf(key, CURVE25519_SIZE); 59261287Sdes crypto_scalarmult_curve25519(pub, key, basepoint); 60261287Sdes} 61261287Sdes 62295367Sdesint 63261287Sdeskexc25519_shared_key(const u_char key[CURVE25519_SIZE], 64295367Sdes const u_char pub[CURVE25519_SIZE], struct sshbuf *out) 65261287Sdes{ 66261287Sdes u_char shared_key[CURVE25519_SIZE]; 67295367Sdes int r; 68261287Sdes 69295367Sdes /* Check for all-zero public key */ 70295367Sdes explicit_bzero(shared_key, CURVE25519_SIZE); 71295367Sdes if (timingsafe_bcmp(pub, shared_key, CURVE25519_SIZE) == 0) 72295367Sdes return SSH_ERR_KEY_INVALID_EC_VALUE; 73295367Sdes 74261287Sdes crypto_scalarmult_curve25519(shared_key, key, pub); 75261287Sdes#ifdef DEBUG_KEXECDH 76261287Sdes dump_digest("shared secret", shared_key, CURVE25519_SIZE); 77261287Sdes#endif 78295367Sdes sshbuf_reset(out); 79295367Sdes r = sshbuf_put_bignum2_bytes(out, shared_key, CURVE25519_SIZE); 80264377Sdes explicit_bzero(shared_key, CURVE25519_SIZE); 81295367Sdes return r; 82261287Sdes} 83261287Sdes 84295367Sdesint 85261287Sdeskex_c25519_hash( 86261287Sdes int hash_alg, 87295367Sdes const char *client_version_string, 88295367Sdes const char *server_version_string, 89323124Sdes const u_char *ckexinit, size_t ckexinitlen, 90323124Sdes const u_char *skexinit, size_t skexinitlen, 91295367Sdes const u_char *serverhostkeyblob, size_t sbloblen, 92261287Sdes const u_char client_dh_pub[CURVE25519_SIZE], 93261287Sdes const u_char server_dh_pub[CURVE25519_SIZE], 94295367Sdes const u_char *shared_secret, size_t secretlen, 95295367Sdes u_char *hash, size_t *hashlen) 96261287Sdes{ 97295367Sdes struct sshbuf *b; 98295367Sdes int r; 99261287Sdes 100295367Sdes if (*hashlen < ssh_digest_bytes(hash_alg)) 101295367Sdes return SSH_ERR_INVALID_ARGUMENT; 102295367Sdes if ((b = sshbuf_new()) == NULL) 103295367Sdes return SSH_ERR_ALLOC_FAIL; 104295367Sdes if ((r = sshbuf_put_cstring(b, client_version_string)) < 0 || 105295367Sdes (r = sshbuf_put_cstring(b, server_version_string)) < 0 || 106295367Sdes /* kexinit messages: fake header: len+SSH2_MSG_KEXINIT */ 107295367Sdes (r = sshbuf_put_u32(b, ckexinitlen+1)) < 0 || 108295367Sdes (r = sshbuf_put_u8(b, SSH2_MSG_KEXINIT)) < 0 || 109295367Sdes (r = sshbuf_put(b, ckexinit, ckexinitlen)) < 0 || 110295367Sdes (r = sshbuf_put_u32(b, skexinitlen+1)) < 0 || 111295367Sdes (r = sshbuf_put_u8(b, SSH2_MSG_KEXINIT)) < 0 || 112295367Sdes (r = sshbuf_put(b, skexinit, skexinitlen)) < 0 || 113295367Sdes (r = sshbuf_put_string(b, serverhostkeyblob, sbloblen)) < 0 || 114295367Sdes (r = sshbuf_put_string(b, client_dh_pub, CURVE25519_SIZE)) < 0 || 115295367Sdes (r = sshbuf_put_string(b, server_dh_pub, CURVE25519_SIZE)) < 0 || 116295367Sdes (r = sshbuf_put(b, shared_secret, secretlen)) < 0) { 117295367Sdes sshbuf_free(b); 118295367Sdes return r; 119295367Sdes } 120261287Sdes#ifdef DEBUG_KEX 121295367Sdes sshbuf_dump(b, stderr); 122261287Sdes#endif 123295367Sdes if (ssh_digest_buffer(hash_alg, b, hash, *hashlen) != 0) { 124295367Sdes sshbuf_free(b); 125295367Sdes return SSH_ERR_LIBCRYPTO_ERROR; 126295367Sdes } 127295367Sdes sshbuf_free(b); 128295367Sdes *hashlen = ssh_digest_bytes(hash_alg); 129261287Sdes#ifdef DEBUG_KEX 130295367Sdes dump_digest("hash", hash, *hashlen); 131261287Sdes#endif 132295367Sdes return 0; 133261287Sdes} 134