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 <sys/types.h> 29 30 #include <signal.h> 31 #include <string.h> 32 33 #include <openssl/bn.h> 34 #include <openssl/evp.h> 35 36 #include "buffer.h" 37 #include "ssh2.h" 38 #include "key.h" 39 #include "cipher.h" 40 #include "kex.h" 41 #include "log.h" 42 #include "digest.h" 43 44 extern int crypto_scalarmult_curve25519(u_char a[CURVE25519_SIZE], 45 const u_char b[CURVE25519_SIZE], const u_char c[CURVE25519_SIZE]) 46 __attribute__((__bounded__(__minbytes__, 1, CURVE25519_SIZE))) 47 __attribute__((__bounded__(__minbytes__, 2, CURVE25519_SIZE))) 48 __attribute__((__bounded__(__minbytes__, 3, CURVE25519_SIZE))); 49 50 void 51 kexc25519_keygen(u_char key[CURVE25519_SIZE], u_char pub[CURVE25519_SIZE]) 52 { 53 static const u_char basepoint[CURVE25519_SIZE] = {9}; 54 55 arc4random_buf(key, CURVE25519_SIZE); 56 crypto_scalarmult_curve25519(pub, key, basepoint); 57 } 58 59 void 60 kexc25519_shared_key(const u_char key[CURVE25519_SIZE], 61 const u_char pub[CURVE25519_SIZE], Buffer *out) 62 { 63 u_char shared_key[CURVE25519_SIZE]; 64 65 crypto_scalarmult_curve25519(shared_key, key, pub); 66 #ifdef DEBUG_KEXECDH 67 dump_digest("shared secret", shared_key, CURVE25519_SIZE); 68 #endif 69 buffer_clear(out); 70 buffer_put_bignum2_from_string(out, shared_key, CURVE25519_SIZE); 71 explicit_bzero(shared_key, CURVE25519_SIZE); 72 } 73 74 void 75 kex_c25519_hash( 76 int hash_alg, 77 char *client_version_string, 78 char *server_version_string, 79 char *ckexinit, int ckexinitlen, 80 char *skexinit, int skexinitlen, 81 u_char *serverhostkeyblob, int sbloblen, 82 const u_char client_dh_pub[CURVE25519_SIZE], 83 const u_char server_dh_pub[CURVE25519_SIZE], 84 const u_char *shared_secret, u_int secretlen, 85 u_char **hash, u_int *hashlen) 86 { 87 Buffer b; 88 static u_char digest[SSH_DIGEST_MAX_LENGTH]; 89 90 buffer_init(&b); 91 buffer_put_cstring(&b, client_version_string); 92 buffer_put_cstring(&b, server_version_string); 93 94 /* kexinit messages: fake header: len+SSH2_MSG_KEXINIT */ 95 buffer_put_int(&b, ckexinitlen+1); 96 buffer_put_char(&b, SSH2_MSG_KEXINIT); 97 buffer_append(&b, ckexinit, ckexinitlen); 98 buffer_put_int(&b, skexinitlen+1); 99 buffer_put_char(&b, SSH2_MSG_KEXINIT); 100 buffer_append(&b, skexinit, skexinitlen); 101 102 buffer_put_string(&b, serverhostkeyblob, sbloblen); 103 buffer_put_string(&b, client_dh_pub, CURVE25519_SIZE); 104 buffer_put_string(&b, server_dh_pub, CURVE25519_SIZE); 105 buffer_append(&b, shared_secret, secretlen); 106 107 #ifdef DEBUG_KEX 108 buffer_dump(&b); 109 #endif 110 if (ssh_digest_buffer(hash_alg, &b, digest, sizeof(digest)) != 0) 111 fatal("%s: digest_buffer failed", __func__); 112 113 buffer_free(&b); 114 115 #ifdef DEBUG_KEX 116 dump_digest("hash", digest, ssh_digest_bytes(hash_alg)); 117 #endif 118 *hash = digest; 119 *hashlen = ssh_digest_bytes(hash_alg); 120 } 121