1 /* $OpenBSD: kexc25519.c,v 1.5 2014/01/31 16:39:19 tedu Exp $ */ 2 /* 3 * Copyright (c) 2001, 2013 Markus Friedl. All rights reserved. 4 * Copyright (c) 2010 Damien Miller. All rights reserved. 5 * Copyright (c) 2013 Aris Adamantiadis. All rights reserved. 6 * 7 * Redistribution and use in source and binary forms, with or without 8 * modification, are permitted provided that the following conditions 9 * are met: 10 * 1. Redistributions of source code must retain the above copyright 11 * notice, this list of conditions and the following disclaimer. 12 * 2. Redistributions in binary form must reproduce the above copyright 13 * notice, this list of conditions and the following disclaimer in the 14 * documentation and/or other materials provided with the distribution. 15 * 16 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR 17 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES 18 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. 19 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, 20 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT 21 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, 22 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY 23 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT 24 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF 25 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 26 */ 27 28 #include "includes.h" 29 30 #include <sys/types.h> 31 32 #include <signal.h> 33 #include <string.h> 34 35 #include <openssl/bn.h> 36 #include <openssl/evp.h> 37 38 #include "buffer.h" 39 #include "ssh2.h" 40 #include "key.h" 41 #include "cipher.h" 42 #include "kex.h" 43 #include "log.h" 44 #include "digest.h" 45 46 extern int crypto_scalarmult_curve25519(u_char a[CURVE25519_SIZE], 47 const u_char b[CURVE25519_SIZE], const u_char c[CURVE25519_SIZE]) 48 __attribute__((__bounded__(__minbytes__, 1, CURVE25519_SIZE))) 49 __attribute__((__bounded__(__minbytes__, 2, CURVE25519_SIZE))) 50 __attribute__((__bounded__(__minbytes__, 3, CURVE25519_SIZE))); 51 52 void 53 kexc25519_keygen(u_char key[CURVE25519_SIZE], u_char pub[CURVE25519_SIZE]) 54 { 55 static const u_char basepoint[CURVE25519_SIZE] = {9}; 56 57 arc4random_buf(key, CURVE25519_SIZE); 58 crypto_scalarmult_curve25519(pub, key, basepoint); 59 } 60 61 void 62 kexc25519_shared_key(const u_char key[CURVE25519_SIZE], 63 const u_char pub[CURVE25519_SIZE], Buffer *out) 64 { 65 u_char shared_key[CURVE25519_SIZE]; 66 67 crypto_scalarmult_curve25519(shared_key, key, pub); 68 #ifdef DEBUG_KEXECDH 69 dump_digest("shared secret", shared_key, CURVE25519_SIZE); 70 #endif 71 buffer_clear(out); 72 buffer_put_bignum2_from_string(out, shared_key, CURVE25519_SIZE); 73 explicit_bzero(shared_key, CURVE25519_SIZE); 74 } 75 76 void 77 kex_c25519_hash( 78 int hash_alg, 79 char *client_version_string, 80 char *server_version_string, 81 char *ckexinit, int ckexinitlen, 82 char *skexinit, int skexinitlen, 83 u_char *serverhostkeyblob, int sbloblen, 84 const u_char client_dh_pub[CURVE25519_SIZE], 85 const u_char server_dh_pub[CURVE25519_SIZE], 86 const u_char *shared_secret, u_int secretlen, 87 u_char **hash, u_int *hashlen) 88 { 89 Buffer b; 90 static u_char digest[SSH_DIGEST_MAX_LENGTH]; 91 92 buffer_init(&b); 93 buffer_put_cstring(&b, client_version_string); 94 buffer_put_cstring(&b, server_version_string); 95 96 /* kexinit messages: fake header: len+SSH2_MSG_KEXINIT */ 97 buffer_put_int(&b, ckexinitlen+1); 98 buffer_put_char(&b, SSH2_MSG_KEXINIT); 99 buffer_append(&b, ckexinit, ckexinitlen); 100 buffer_put_int(&b, skexinitlen+1); 101 buffer_put_char(&b, SSH2_MSG_KEXINIT); 102 buffer_append(&b, skexinit, skexinitlen); 103 104 buffer_put_string(&b, serverhostkeyblob, sbloblen); 105 buffer_put_string(&b, client_dh_pub, CURVE25519_SIZE); 106 buffer_put_string(&b, server_dh_pub, CURVE25519_SIZE); 107 buffer_append(&b, shared_secret, secretlen); 108 109 #ifdef DEBUG_KEX 110 buffer_dump(&b); 111 #endif 112 if (ssh_digest_buffer(hash_alg, &b, digest, sizeof(digest)) != 0) 113 fatal("%s: digest_buffer failed", __func__); 114 115 buffer_free(&b); 116 117 #ifdef DEBUG_KEX 118 dump_digest("hash", digest, ssh_digest_bytes(hash_alg)); 119 #endif 120 *hash = digest; 121 *hashlen = ssh_digest_bytes(hash_alg); 122 } 123