Annotation of src/usr.bin/ssh/kexdhs.c, Revision 1.1.4.2
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"
1.1.4.1 margarid 26: RCSID("$OpenBSD: kexdhs.c,v 1.1 2003/02/16 17:09:57 markus Exp $");
1.1 markus 27:
28: #include "xmalloc.h"
29: #include "key.h"
30: #include "kex.h"
31: #include "log.h"
32: #include "packet.h"
33: #include "dh.h"
34: #include "ssh2.h"
35: #include "monitor_wrap.h"
36:
37: void
38: kexdh_server(Kex *kex)
39: {
40: BIGNUM *shared_secret = NULL, *dh_client_pub = NULL;
41: DH *dh;
42: Key *server_host_key;
43: u_char *kbuf, *hash, *signature = NULL, *server_host_key_blob = NULL;
44: u_int sbloblen, klen, kout;
45: u_int slen;
46:
47: /* generate server DH public key */
48: dh = dh_new_group1();
49: dh_gen_key(dh, kex->we_need * 8);
50:
51: debug("expecting SSH2_MSG_KEXDH_INIT");
52: packet_read_expect(SSH2_MSG_KEXDH_INIT);
53:
54: if (kex->load_host_key == NULL)
55: fatal("Cannot load hostkey");
56: server_host_key = kex->load_host_key(kex->hostkey_type);
57: if (server_host_key == NULL)
58: fatal("Unsupported hostkey type %d", kex->hostkey_type);
59:
60: /* key, cert */
61: if ((dh_client_pub = BN_new()) == NULL)
62: fatal("dh_client_pub == NULL");
63: packet_get_bignum2(dh_client_pub);
64: packet_check_eom();
65:
66: #ifdef DEBUG_KEXDH
67: fprintf(stderr, "dh_client_pub= ");
68: BN_print_fp(stderr, dh_client_pub);
69: fprintf(stderr, "\n");
70: debug("bits %d", BN_num_bits(dh_client_pub));
71: #endif
72:
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: if (!dh_pub_is_valid(dh, dh_client_pub))
80: packet_disconnect("bad client public DH value");
81:
82: klen = DH_size(dh);
83: kbuf = xmalloc(klen);
84: kout = DH_compute_key(kbuf, dh_client_pub, dh);
85: #ifdef DEBUG_KEXDH
86: dump_digest("shared secret", kbuf, kout);
87: #endif
88: if ((shared_secret = BN_new()) == NULL)
89: fatal("kexdh_server: BN_new failed");
90: BN_bin2bn(kbuf, kout, shared_secret);
91: memset(kbuf, 0, klen);
92: xfree(kbuf);
93:
94: key_to_blob(server_host_key, &server_host_key_blob, &sbloblen);
95:
96: /* calc H */
97: hash = kex_dh_hash(
98: kex->client_version_string,
99: kex->server_version_string,
100: buffer_ptr(&kex->peer), buffer_len(&kex->peer),
101: buffer_ptr(&kex->my), buffer_len(&kex->my),
102: server_host_key_blob, sbloblen,
103: dh_client_pub,
104: dh->pub_key,
105: shared_secret
106: );
107: BN_clear_free(dh_client_pub);
108:
109: /* save session id := H */
110: /* XXX hashlen depends on KEX */
111: if (kex->session_id == NULL) {
112: kex->session_id_len = 20;
113: kex->session_id = xmalloc(kex->session_id_len);
114: memcpy(kex->session_id, hash, kex->session_id_len);
115: }
116:
117: /* sign H */
118: /* XXX hashlen depends on KEX */
119: PRIVSEP(key_sign(server_host_key, &signature, &slen, hash, 20));
120:
121: /* destroy_sensitive_data(); */
122:
123: /* send server hostkey, DH pubkey 'f' and singed H */
124: packet_start(SSH2_MSG_KEXDH_REPLY);
125: packet_put_string(server_host_key_blob, sbloblen);
126: packet_put_bignum2(dh->pub_key); /* f */
127: packet_put_string(signature, slen);
128: packet_send();
129:
130: xfree(signature);
131: xfree(server_host_key_blob);
132: /* have keys, free DH */
133: DH_free(dh);
134:
135: kex_derive_keys(kex, hash, shared_secret);
136: BN_clear_free(shared_secret);
137: kex_finish(kex);
138: }
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