Annotation of src/usr.bin/ssh/kexdhs.c, Revision 1.4
1.1 markus 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: #include "monitor_wrap.h"
35:
36: void
37: kexdh_server(Kex *kex)
38: {
39: BIGNUM *shared_secret = NULL, *dh_client_pub = NULL;
40: DH *dh;
41: Key *server_host_key;
42: u_char *kbuf, *hash, *signature = NULL, *server_host_key_blob = NULL;
1.3 djm 43: u_int sbloblen, klen, kout, hashlen;
1.1 markus 44: u_int slen;
45:
46: /* generate server DH public key */
1.2 djm 47: switch (kex->kex_type) {
48: case KEX_DH_GRP1_SHA1:
49: dh = dh_new_group1();
50: break;
51: case KEX_DH_GRP14_SHA1:
52: dh = dh_new_group14();
53: break;
54: default:
55: fatal("%s: Unexpected KEX type %d", __func__, kex->kex_type);
56: }
1.1 markus 57: dh_gen_key(dh, kex->we_need * 8);
58:
59: debug("expecting SSH2_MSG_KEXDH_INIT");
60: packet_read_expect(SSH2_MSG_KEXDH_INIT);
61:
62: if (kex->load_host_key == NULL)
63: fatal("Cannot load hostkey");
64: server_host_key = kex->load_host_key(kex->hostkey_type);
65: if (server_host_key == NULL)
66: fatal("Unsupported hostkey type %d", kex->hostkey_type);
67:
68: /* key, cert */
69: if ((dh_client_pub = BN_new()) == NULL)
70: fatal("dh_client_pub == NULL");
71: packet_get_bignum2(dh_client_pub);
72: packet_check_eom();
73:
74: #ifdef DEBUG_KEXDH
75: fprintf(stderr, "dh_client_pub= ");
76: BN_print_fp(stderr, dh_client_pub);
77: fprintf(stderr, "\n");
78: debug("bits %d", BN_num_bits(dh_client_pub));
79: #endif
80:
81: #ifdef DEBUG_KEXDH
82: DHparams_print_fp(stderr, dh);
83: fprintf(stderr, "pub= ");
84: BN_print_fp(stderr, dh->pub_key);
85: fprintf(stderr, "\n");
86: #endif
87: if (!dh_pub_is_valid(dh, dh_client_pub))
88: packet_disconnect("bad client public DH value");
89:
90: klen = DH_size(dh);
91: kbuf = xmalloc(klen);
92: kout = DH_compute_key(kbuf, dh_client_pub, dh);
93: #ifdef DEBUG_KEXDH
94: dump_digest("shared secret", kbuf, kout);
95: #endif
96: if ((shared_secret = BN_new()) == NULL)
97: fatal("kexdh_server: BN_new failed");
98: BN_bin2bn(kbuf, kout, shared_secret);
99: memset(kbuf, 0, klen);
100: xfree(kbuf);
101:
102: key_to_blob(server_host_key, &server_host_key_blob, &sbloblen);
103:
104: /* calc H */
1.3 djm 105: kex_dh_hash(
1.1 markus 106: kex->client_version_string,
107: kex->server_version_string,
108: buffer_ptr(&kex->peer), buffer_len(&kex->peer),
109: buffer_ptr(&kex->my), buffer_len(&kex->my),
110: server_host_key_blob, sbloblen,
111: dh_client_pub,
112: dh->pub_key,
1.3 djm 113: shared_secret,
114: &hash, &hashlen
1.1 markus 115: );
116: BN_clear_free(dh_client_pub);
117:
118: /* save session id := H */
119: if (kex->session_id == NULL) {
1.3 djm 120: kex->session_id_len = hashlen;
1.1 markus 121: kex->session_id = xmalloc(kex->session_id_len);
122: memcpy(kex->session_id, hash, kex->session_id_len);
123: }
124:
125: /* sign H */
1.3 djm 126: PRIVSEP(key_sign(server_host_key, &signature, &slen, hash, hashlen));
1.1 markus 127:
128: /* destroy_sensitive_data(); */
129:
130: /* send server hostkey, DH pubkey 'f' and singed H */
131: packet_start(SSH2_MSG_KEXDH_REPLY);
132: packet_put_string(server_host_key_blob, sbloblen);
133: packet_put_bignum2(dh->pub_key); /* f */
134: packet_put_string(signature, slen);
135: packet_send();
136:
137: xfree(signature);
138: xfree(server_host_key_blob);
139: /* have keys, free DH */
140: DH_free(dh);
141:
1.3 djm 142: kex_derive_keys(kex, hash, hashlen, shared_secret);
1.1 markus 143: BN_clear_free(shared_secret);
144: kex_finish(kex);
145: }
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