1 /* $OpenBSD: kexdhs.c,v 1.12 2010/11/10 01:33:07 djm Exp $ */ 2 /* 3 * Copyright (c) 2001 Markus Friedl. All rights reserved. 4 * 5 * Redistribution and use in source and binary forms, with or without 6 * modification, are permitted provided that the following conditions 7 * are met: 8 * 1. Redistributions of source code must retain the above copyright 9 * notice, this list of conditions and the following disclaimer. 10 * 2. Redistributions in binary form must reproduce the above copyright 11 * notice, this list of conditions and the following disclaimer in the 12 * documentation and/or other materials provided with the distribution. 13 * 14 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR 15 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES 16 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. 17 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, 18 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT 19 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, 20 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY 21 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT 22 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF 23 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 24 */ 25 26 #include "includes.h" 27 28 #include <sys/types.h> 29 30 #include <stdarg.h> 31 #include <string.h> 32 #include <signal.h> 33 34 #include <openssl/dh.h> 35 36 #include "xmalloc.h" 37 #include "buffer.h" 38 #include "key.h" 39 #include "cipher.h" 40 #include "kex.h" 41 #include "log.h" 42 #include "packet.h" 43 #include "dh.h" 44 #include "ssh2.h" 45 #ifdef GSSAPI 46 #include "ssh-gss.h" 47 #endif 48 #include "monitor_wrap.h" 49 50 void 51 kexdh_server(Kex *kex) 52 { 53 BIGNUM *shared_secret = NULL, *dh_client_pub = NULL; 54 DH *dh; 55 Key *server_host_public, *server_host_private; 56 u_char *kbuf, *hash, *signature = NULL, *server_host_key_blob = NULL; 57 u_int sbloblen, klen, hashlen, slen; 58 int kout; 59 60 /* generate server DH public key */ 61 switch (kex->kex_type) { 62 case KEX_DH_GRP1_SHA1: 63 dh = dh_new_group1(); 64 break; 65 case KEX_DH_GRP14_SHA1: 66 dh = dh_new_group14(); 67 break; 68 default: 69 fatal("%s: Unexpected KEX type %d", __func__, kex->kex_type); 70 } 71 dh_gen_key(dh, kex->we_need * 8); 72 73 debug("expecting SSH2_MSG_KEXDH_INIT"); 74 packet_read_expect(SSH2_MSG_KEXDH_INIT); 75 76 if (kex->load_host_public_key == NULL || 77 kex->load_host_private_key == NULL) 78 fatal("Cannot load hostkey"); 79 server_host_public = kex->load_host_public_key(kex->hostkey_type); 80 if (server_host_public == NULL) 81 fatal("Unsupported hostkey type %d", kex->hostkey_type); 82 server_host_private = kex->load_host_private_key(kex->hostkey_type); 83 if (server_host_private == NULL) 84 fatal("Missing private key for hostkey type %d", 85 kex->hostkey_type); 86 87 /* key, cert */ 88 if ((dh_client_pub = BN_new()) == NULL) 89 fatal("dh_client_pub == NULL"); 90 packet_get_bignum2(dh_client_pub); 91 packet_check_eom(); 92 93 #ifdef DEBUG_KEXDH 94 fprintf(stderr, "dh_client_pub= "); 95 BN_print_fp(stderr, dh_client_pub); 96 fprintf(stderr, "\n"); 97 debug("bits %d", BN_num_bits(dh_client_pub)); 98 #endif 99 100 #ifdef DEBUG_KEXDH 101 DHparams_print_fp(stderr, dh); 102 fprintf(stderr, "pub= "); 103 BN_print_fp(stderr, dh->pub_key); 104 fprintf(stderr, "\n"); 105 #endif 106 if (!dh_pub_is_valid(dh, dh_client_pub)) 107 packet_disconnect("bad client public DH value"); 108 109 klen = DH_size(dh); 110 kbuf = xmalloc(klen); 111 if ((kout = DH_compute_key(kbuf, dh_client_pub, dh)) < 0) 112 fatal("DH_compute_key: failed"); 113 #ifdef DEBUG_KEXDH 114 dump_digest("shared secret", kbuf, kout); 115 #endif 116 if ((shared_secret = BN_new()) == NULL) 117 fatal("kexdh_server: BN_new failed"); 118 if (BN_bin2bn(kbuf, kout, shared_secret) == NULL) 119 fatal("kexdh_server: BN_bin2bn failed"); 120 memset(kbuf, 0, klen); 121 xfree(kbuf); 122 123 key_to_blob(server_host_public, &server_host_key_blob, &sbloblen); 124 125 /* calc H */ 126 kex_dh_hash( 127 kex->client_version_string, 128 kex->server_version_string, 129 buffer_ptr(&kex->peer), buffer_len(&kex->peer), 130 buffer_ptr(&kex->my), buffer_len(&kex->my), 131 server_host_key_blob, sbloblen, 132 dh_client_pub, 133 dh->pub_key, 134 shared_secret, 135 &hash, &hashlen 136 ); 137 BN_clear_free(dh_client_pub); 138 139 /* save session id := H */ 140 if (kex->session_id == NULL) { 141 kex->session_id_len = hashlen; 142 kex->session_id = xmalloc(kex->session_id_len); 143 memcpy(kex->session_id, hash, kex->session_id_len); 144 } 145 146 /* sign H */ 147 if (PRIVSEP(key_sign(server_host_private, &signature, &slen, hash, 148 hashlen)) < 0) 149 fatal("kexdh_server: key_sign failed"); 150 151 /* destroy_sensitive_data(); */ 152 153 /* send server hostkey, DH pubkey 'f' and singed H */ 154 packet_start(SSH2_MSG_KEXDH_REPLY); 155 packet_put_string(server_host_key_blob, sbloblen); 156 packet_put_bignum2(dh->pub_key); /* f */ 157 packet_put_string(signature, slen); 158 packet_send(); 159 160 xfree(signature); 161 xfree(server_host_key_blob); 162 /* have keys, free DH */ 163 DH_free(dh); 164 165 kex_derive_keys(kex, hash, hashlen, shared_secret); 166 BN_clear_free(shared_secret); 167 kex_finish(kex); 168 } 169
