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