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2e437378 | 1 | /* $OpenBSD: kexdhs.c,v 1.9 2006/11/06 21:25:28 markus Exp $ */ |
1c14df9e | 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" | |
2e437378 | 27 | |
28 | #include <sys/types.h> | |
29 | ||
30 | #include <stdarg.h> | |
31 | #include <string.h> | |
32 | #include <signal.h> | |
1c14df9e | 33 | |
34 | #include "xmalloc.h" | |
2e437378 | 35 | #include "buffer.h" |
1c14df9e | 36 | #include "key.h" |
2e437378 | 37 | #include "cipher.h" |
1c14df9e | 38 | #include "kex.h" |
39 | #include "log.h" | |
40 | #include "packet.h" | |
41 | #include "dh.h" | |
42 | #include "ssh2.h" | |
2e437378 | 43 | #ifdef GSSAPI |
44 | #include "ssh-gss.h" | |
45 | #endif | |
1c14df9e | 46 | #include "monitor_wrap.h" |
47 | ||
48 | void | |
49 | kexdh_server(Kex *kex) | |
50 | { | |
51 | BIGNUM *shared_secret = NULL, *dh_client_pub = NULL; | |
52 | DH *dh; | |
53 | Key *server_host_key; | |
54 | u_char *kbuf, *hash, *signature = NULL, *server_host_key_blob = NULL; | |
2e437378 | 55 | u_int sbloblen, klen, hashlen, slen; |
56 | int kout; | |
1c14df9e | 57 | |
58 | /* generate server DH public key */ | |
1b56ff3d | 59 | switch (kex->kex_type) { |
60 | case KEX_DH_GRP1_SHA1: | |
61 | dh = dh_new_group1(); | |
62 | break; | |
63 | case KEX_DH_GRP14_SHA1: | |
64 | dh = dh_new_group14(); | |
65 | break; | |
66 | default: | |
67 | fatal("%s: Unexpected KEX type %d", __func__, kex->kex_type); | |
68 | } | |
1c14df9e | 69 | dh_gen_key(dh, kex->we_need * 8); |
70 | ||
71 | debug("expecting SSH2_MSG_KEXDH_INIT"); | |
72 | packet_read_expect(SSH2_MSG_KEXDH_INIT); | |
73 | ||
74 | if (kex->load_host_key == NULL) | |
75 | fatal("Cannot load hostkey"); | |
76 | server_host_key = kex->load_host_key(kex->hostkey_type); | |
77 | if (server_host_key == NULL) | |
78 | fatal("Unsupported hostkey type %d", kex->hostkey_type); | |
79 | ||
80 | /* key, cert */ | |
81 | if ((dh_client_pub = BN_new()) == NULL) | |
82 | fatal("dh_client_pub == NULL"); | |
83 | packet_get_bignum2(dh_client_pub); | |
84 | packet_check_eom(); | |
85 | ||
86 | #ifdef DEBUG_KEXDH | |
87 | fprintf(stderr, "dh_client_pub= "); | |
88 | BN_print_fp(stderr, dh_client_pub); | |
89 | fprintf(stderr, "\n"); | |
90 | debug("bits %d", BN_num_bits(dh_client_pub)); | |
91 | #endif | |
92 | ||
93 | #ifdef DEBUG_KEXDH | |
94 | DHparams_print_fp(stderr, dh); | |
95 | fprintf(stderr, "pub= "); | |
96 | BN_print_fp(stderr, dh->pub_key); | |
97 | fprintf(stderr, "\n"); | |
98 | #endif | |
99 | if (!dh_pub_is_valid(dh, dh_client_pub)) | |
100 | packet_disconnect("bad client public DH value"); | |
101 | ||
102 | klen = DH_size(dh); | |
103 | kbuf = xmalloc(klen); | |
2e437378 | 104 | if ((kout = DH_compute_key(kbuf, dh_client_pub, dh)) < 0) |
105 | fatal("DH_compute_key: failed"); | |
1c14df9e | 106 | #ifdef DEBUG_KEXDH |
107 | dump_digest("shared secret", kbuf, kout); | |
108 | #endif | |
109 | if ((shared_secret = BN_new()) == NULL) | |
110 | fatal("kexdh_server: BN_new failed"); | |
2e437378 | 111 | if (BN_bin2bn(kbuf, kout, shared_secret) == NULL) |
112 | fatal("kexdh_server: BN_bin2bn failed"); | |
1c14df9e | 113 | memset(kbuf, 0, klen); |
114 | xfree(kbuf); | |
115 | ||
116 | key_to_blob(server_host_key, &server_host_key_blob, &sbloblen); | |
117 | ||
118 | /* calc H */ | |
e00da40d | 119 | kex_dh_hash( |
1c14df9e | 120 | kex->client_version_string, |
121 | kex->server_version_string, | |
122 | buffer_ptr(&kex->peer), buffer_len(&kex->peer), | |
123 | buffer_ptr(&kex->my), buffer_len(&kex->my), | |
124 | server_host_key_blob, sbloblen, | |
125 | dh_client_pub, | |
126 | dh->pub_key, | |
e00da40d | 127 | shared_secret, |
128 | &hash, &hashlen | |
1c14df9e | 129 | ); |
130 | BN_clear_free(dh_client_pub); | |
131 | ||
132 | /* save session id := H */ | |
1c14df9e | 133 | if (kex->session_id == NULL) { |
e00da40d | 134 | kex->session_id_len = hashlen; |
1c14df9e | 135 | kex->session_id = xmalloc(kex->session_id_len); |
136 | memcpy(kex->session_id, hash, kex->session_id_len); | |
137 | } | |
138 | ||
139 | /* sign H */ | |
e00da40d | 140 | PRIVSEP(key_sign(server_host_key, &signature, &slen, hash, hashlen)); |
1c14df9e | 141 | |
142 | /* destroy_sensitive_data(); */ | |
143 | ||
144 | /* send server hostkey, DH pubkey 'f' and singed H */ | |
145 | packet_start(SSH2_MSG_KEXDH_REPLY); | |
146 | packet_put_string(server_host_key_blob, sbloblen); | |
147 | packet_put_bignum2(dh->pub_key); /* f */ | |
148 | packet_put_string(signature, slen); | |
149 | packet_send(); | |
150 | ||
151 | xfree(signature); | |
152 | xfree(server_host_key_blob); | |
153 | /* have keys, free DH */ | |
154 | DH_free(dh); | |
155 | ||
e00da40d | 156 | kex_derive_keys(kex, hash, hashlen, shared_secret); |
1c14df9e | 157 | BN_clear_free(shared_secret); |
158 | kex_finish(kex); | |
159 | } |