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31652869 | 1 | /* $OpenBSD: kexdhc.c,v 1.9 2006/08/03 03:34:42 deraadt Exp $ */ |
98a58eda | 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" | |
98a58eda | 27 | |
31652869 | 28 | #include <sys/types.h> |
29 | ||
cf851879 | 30 | #include <stdio.h> |
00146caa | 31 | #include <string.h> |
31652869 | 32 | #include <signal.h> |
00146caa | 33 | |
98a58eda | 34 | #include "xmalloc.h" |
31652869 | 35 | #include "buffer.h" |
98a58eda | 36 | #include "key.h" |
31652869 | 37 | #include "cipher.h" |
98a58eda | 38 | #include "kex.h" |
39 | #include "log.h" | |
40 | #include "packet.h" | |
41 | #include "dh.h" | |
42 | #include "ssh2.h" | |
43 | ||
44 | void | |
45 | kexdh_client(Kex *kex) | |
46 | { | |
47 | BIGNUM *dh_server_pub = NULL, *shared_secret = NULL; | |
48 | DH *dh; | |
49 | Key *server_host_key; | |
50 | u_char *server_host_key_blob = NULL, *signature = NULL; | |
51 | u_char *kbuf, *hash; | |
47e5dc72 | 52 | u_int klen, kout, slen, sbloblen, hashlen; |
98a58eda | 53 | |
54 | /* generate and send 'e', client DH public key */ | |
41e5bd9a | 55 | switch (kex->kex_type) { |
56 | case KEX_DH_GRP1_SHA1: | |
57 | dh = dh_new_group1(); | |
58 | break; | |
59 | case KEX_DH_GRP14_SHA1: | |
60 | dh = dh_new_group14(); | |
61 | break; | |
62 | default: | |
63 | fatal("%s: Unexpected KEX type %d", __func__, kex->kex_type); | |
64 | } | |
98a58eda | 65 | dh_gen_key(dh, kex->we_need * 8); |
66 | packet_start(SSH2_MSG_KEXDH_INIT); | |
67 | packet_put_bignum2(dh->pub_key); | |
68 | packet_send(); | |
69 | ||
70 | debug("sending SSH2_MSG_KEXDH_INIT"); | |
71 | #ifdef DEBUG_KEXDH | |
72 | DHparams_print_fp(stderr, dh); | |
73 | fprintf(stderr, "pub= "); | |
74 | BN_print_fp(stderr, dh->pub_key); | |
75 | fprintf(stderr, "\n"); | |
76 | #endif | |
77 | ||
78 | debug("expecting SSH2_MSG_KEXDH_REPLY"); | |
79 | packet_read_expect(SSH2_MSG_KEXDH_REPLY); | |
80 | ||
81 | /* key, cert */ | |
82 | server_host_key_blob = packet_get_string(&sbloblen); | |
83 | server_host_key = key_from_blob(server_host_key_blob, sbloblen); | |
84 | if (server_host_key == NULL) | |
85 | fatal("cannot decode server_host_key_blob"); | |
86 | if (server_host_key->type != kex->hostkey_type) | |
87 | fatal("type mismatch for decoded server_host_key_blob"); | |
88 | if (kex->verify_host_key == NULL) | |
89 | fatal("cannot verify server_host_key"); | |
90 | if (kex->verify_host_key(server_host_key) == -1) | |
91 | fatal("server_host_key verification failed"); | |
92 | ||
18c60a0b | 93 | /* DH parameter f, server public DH key */ |
98a58eda | 94 | if ((dh_server_pub = BN_new()) == NULL) |
95 | fatal("dh_server_pub == NULL"); | |
96 | packet_get_bignum2(dh_server_pub); | |
97 | ||
98 | #ifdef DEBUG_KEXDH | |
99 | fprintf(stderr, "dh_server_pub= "); | |
100 | BN_print_fp(stderr, dh_server_pub); | |
101 | fprintf(stderr, "\n"); | |
102 | debug("bits %d", BN_num_bits(dh_server_pub)); | |
103 | #endif | |
104 | ||
105 | /* signed H */ | |
106 | signature = packet_get_string(&slen); | |
107 | packet_check_eom(); | |
108 | ||
109 | if (!dh_pub_is_valid(dh, dh_server_pub)) | |
110 | packet_disconnect("bad server public DH value"); | |
111 | ||
112 | klen = DH_size(dh); | |
113 | kbuf = xmalloc(klen); | |
114 | kout = DH_compute_key(kbuf, dh_server_pub, dh); | |
115 | #ifdef DEBUG_KEXDH | |
116 | dump_digest("shared secret", kbuf, kout); | |
117 | #endif | |
118 | if ((shared_secret = BN_new()) == NULL) | |
119 | fatal("kexdh_client: BN_new failed"); | |
120 | BN_bin2bn(kbuf, kout, shared_secret); | |
121 | memset(kbuf, 0, klen); | |
122 | xfree(kbuf); | |
123 | ||
124 | /* calc and verify H */ | |
47e5dc72 | 125 | kex_dh_hash( |
98a58eda | 126 | kex->client_version_string, |
127 | kex->server_version_string, | |
128 | buffer_ptr(&kex->my), buffer_len(&kex->my), | |
129 | buffer_ptr(&kex->peer), buffer_len(&kex->peer), | |
130 | server_host_key_blob, sbloblen, | |
131 | dh->pub_key, | |
132 | dh_server_pub, | |
47e5dc72 | 133 | shared_secret, |
134 | &hash, &hashlen | |
98a58eda | 135 | ); |
136 | xfree(server_host_key_blob); | |
137 | BN_clear_free(dh_server_pub); | |
138 | DH_free(dh); | |
139 | ||
47e5dc72 | 140 | if (key_verify(server_host_key, signature, slen, hash, hashlen) != 1) |
98a58eda | 141 | fatal("key_verify failed for server_host_key"); |
142 | key_free(server_host_key); | |
143 | xfree(signature); | |
144 | ||
145 | /* save session id */ | |
146 | if (kex->session_id == NULL) { | |
47e5dc72 | 147 | kex->session_id_len = hashlen; |
98a58eda | 148 | kex->session_id = xmalloc(kex->session_id_len); |
149 | memcpy(kex->session_id, hash, kex->session_id_len); | |
150 | } | |
151 | ||
47e5dc72 | 152 | kex_derive_keys(kex, hash, hashlen, shared_secret); |
98a58eda | 153 | BN_clear_free(shared_secret); |
154 | kex_finish(kex); | |
155 | } |