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1 | /* $OpenBSD: kexdhc.c,v 1.11 2006/11/06 21:25:28 markus 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 <stdio.h> | |
32 | #include <string.h> | |
33 | #include <signal.h> | |
34 | ||
35 | #include "xmalloc.h" | |
36 | #include "buffer.h" | |
37 | #include "key.h" | |
38 | #include "cipher.h" | |
39 | #include "kex.h" | |
40 | #include "log.h" | |
41 | #include "packet.h" | |
42 | #include "dh.h" | |
43 | #include "ssh2.h" | |
44 | ||
45 | void | |
46 | kexdh_client(Kex *kex) | |
47 | { | |
48 | BIGNUM *dh_server_pub = NULL, *shared_secret = NULL; | |
49 | DH *dh; | |
50 | Key *server_host_key; | |
51 | u_char *server_host_key_blob = NULL, *signature = NULL; | |
52 | u_char *kbuf, *hash; | |
53 | u_int klen, slen, sbloblen, hashlen; | |
54 | int kout; | |
55 | ||
56 | /* generate and send 'e', client DH public key */ | |
57 | switch (kex->kex_type) { | |
58 | case KEX_DH_GRP1_SHA1: | |
59 | dh = dh_new_group1(); | |
60 | break; | |
61 | case KEX_DH_GRP14_SHA1: | |
62 | dh = dh_new_group14(); | |
63 | break; | |
64 | default: | |
65 | fatal("%s: Unexpected KEX type %d", __func__, kex->kex_type); | |
66 | } | |
67 | dh_gen_key(dh, kex->we_need * 8); | |
68 | packet_start(SSH2_MSG_KEXDH_INIT); | |
69 | packet_put_bignum2(dh->pub_key); | |
70 | packet_send(); | |
71 | ||
72 | debug("sending SSH2_MSG_KEXDH_INIT"); | |
73 | #ifdef DEBUG_KEXDH | |
74 | DHparams_print_fp(stderr, dh); | |
75 | fprintf(stderr, "pub= "); | |
76 | BN_print_fp(stderr, dh->pub_key); | |
77 | fprintf(stderr, "\n"); | |
78 | #endif | |
79 | ||
80 | debug("expecting SSH2_MSG_KEXDH_REPLY"); | |
81 | packet_read_expect(SSH2_MSG_KEXDH_REPLY); | |
82 | ||
83 | /* key, cert */ | |
84 | server_host_key_blob = packet_get_string(&sbloblen); | |
85 | server_host_key = key_from_blob(server_host_key_blob, sbloblen); | |
86 | if (server_host_key == NULL) | |
87 | fatal("cannot decode server_host_key_blob"); | |
88 | if (server_host_key->type != kex->hostkey_type) | |
89 | fatal("type mismatch for decoded server_host_key_blob"); | |
90 | if (kex->verify_host_key == NULL) | |
91 | fatal("cannot verify server_host_key"); | |
92 | if (kex->verify_host_key(server_host_key) == -1) | |
93 | fatal("server_host_key verification failed"); | |
94 | ||
95 | /* DH parameter f, server public DH key */ | |
96 | if ((dh_server_pub = BN_new()) == NULL) | |
97 | fatal("dh_server_pub == NULL"); | |
98 | packet_get_bignum2(dh_server_pub); | |
99 | ||
100 | #ifdef DEBUG_KEXDH | |
101 | fprintf(stderr, "dh_server_pub= "); | |
102 | BN_print_fp(stderr, dh_server_pub); | |
103 | fprintf(stderr, "\n"); | |
104 | debug("bits %d", BN_num_bits(dh_server_pub)); | |
105 | #endif | |
106 | ||
107 | /* signed H */ | |
108 | signature = packet_get_string(&slen); | |
109 | packet_check_eom(); | |
110 | ||
111 | if (!dh_pub_is_valid(dh, dh_server_pub)) | |
112 | packet_disconnect("bad server public DH value"); | |
113 | ||
114 | klen = DH_size(dh); | |
115 | kbuf = xmalloc(klen); | |
116 | if ((kout = DH_compute_key(kbuf, dh_server_pub, dh)) < 0) | |
117 | fatal("DH_compute_key: failed"); | |
118 | #ifdef DEBUG_KEXDH | |
119 | dump_digest("shared secret", kbuf, kout); | |
120 | #endif | |
121 | if ((shared_secret = BN_new()) == NULL) | |
122 | fatal("kexdh_client: BN_new failed"); | |
123 | if (BN_bin2bn(kbuf, kout, shared_secret) == NULL) | |
124 | fatal("kexdh_client: BN_bin2bn failed"); | |
125 | memset(kbuf, 0, klen); | |
126 | xfree(kbuf); | |
127 | ||
128 | /* calc and verify H */ | |
129 | kex_dh_hash( | |
130 | kex->client_version_string, | |
131 | kex->server_version_string, | |
132 | buffer_ptr(&kex->my), buffer_len(&kex->my), | |
133 | buffer_ptr(&kex->peer), buffer_len(&kex->peer), | |
134 | server_host_key_blob, sbloblen, | |
135 | dh->pub_key, | |
136 | dh_server_pub, | |
137 | shared_secret, | |
138 | &hash, &hashlen | |
139 | ); | |
140 | xfree(server_host_key_blob); | |
141 | BN_clear_free(dh_server_pub); | |
142 | DH_free(dh); | |
143 | ||
144 | if (key_verify(server_host_key, signature, slen, hash, hashlen) != 1) | |
145 | fatal("key_verify failed for server_host_key"); | |
146 | key_free(server_host_key); | |
147 | xfree(signature); | |
148 | ||
149 | /* save session id */ | |
150 | if (kex->session_id == NULL) { | |
151 | kex->session_id_len = hashlen; | |
152 | kex->session_id = xmalloc(kex->session_id_len); | |
153 | memcpy(kex->session_id, hash, kex->session_id_len); | |
154 | } | |
155 | ||
156 | kex_derive_keys(kex, hash, hashlen, shared_secret); | |
157 | BN_clear_free(shared_secret); | |
158 | kex_finish(kex); | |
159 | } |