Annotation of src/usr.bin/ssh/kexdhs.c, Revision 1.1.8.1
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"
1.1.8.1 ! brad 26: RCSID("$OpenBSD: kexdhs.c,v 1.2 2004/06/13 12:53:24 djm 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 */
1.1.8.1 ! brad 48: switch (kex->kex_type) {
! 49: case KEX_DH_GRP1_SHA1:
! 50: dh = dh_new_group1();
! 51: break;
! 52: case KEX_DH_GRP14_SHA1:
! 53: dh = dh_new_group14();
! 54: break;
! 55: default:
! 56: fatal("%s: Unexpected KEX type %d", __func__, kex->kex_type);
! 57: }
1.1 markus 58: dh_gen_key(dh, kex->we_need * 8);
59:
60: debug("expecting SSH2_MSG_KEXDH_INIT");
61: packet_read_expect(SSH2_MSG_KEXDH_INIT);
62:
63: if (kex->load_host_key == NULL)
64: fatal("Cannot load hostkey");
65: server_host_key = kex->load_host_key(kex->hostkey_type);
66: if (server_host_key == NULL)
67: fatal("Unsupported hostkey type %d", kex->hostkey_type);
68:
69: /* key, cert */
70: if ((dh_client_pub = BN_new()) == NULL)
71: fatal("dh_client_pub == NULL");
72: packet_get_bignum2(dh_client_pub);
73: packet_check_eom();
74:
75: #ifdef DEBUG_KEXDH
76: fprintf(stderr, "dh_client_pub= ");
77: BN_print_fp(stderr, dh_client_pub);
78: fprintf(stderr, "\n");
79: debug("bits %d", BN_num_bits(dh_client_pub));
80: #endif
81:
82: #ifdef DEBUG_KEXDH
83: DHparams_print_fp(stderr, dh);
84: fprintf(stderr, "pub= ");
85: BN_print_fp(stderr, dh->pub_key);
86: fprintf(stderr, "\n");
87: #endif
88: if (!dh_pub_is_valid(dh, dh_client_pub))
89: packet_disconnect("bad client public DH value");
90:
91: klen = DH_size(dh);
92: kbuf = xmalloc(klen);
93: kout = DH_compute_key(kbuf, dh_client_pub, dh);
94: #ifdef DEBUG_KEXDH
95: dump_digest("shared secret", kbuf, kout);
96: #endif
97: if ((shared_secret = BN_new()) == NULL)
98: fatal("kexdh_server: BN_new failed");
99: BN_bin2bn(kbuf, kout, shared_secret);
100: memset(kbuf, 0, klen);
101: xfree(kbuf);
102:
103: key_to_blob(server_host_key, &server_host_key_blob, &sbloblen);
104:
105: /* calc H */
106: hash = kex_dh_hash(
107: kex->client_version_string,
108: kex->server_version_string,
109: buffer_ptr(&kex->peer), buffer_len(&kex->peer),
110: buffer_ptr(&kex->my), buffer_len(&kex->my),
111: server_host_key_blob, sbloblen,
112: dh_client_pub,
113: dh->pub_key,
114: shared_secret
115: );
116: BN_clear_free(dh_client_pub);
117:
118: /* save session id := H */
119: /* XXX hashlen depends on KEX */
120: if (kex->session_id == NULL) {
121: kex->session_id_len = 20;
122: kex->session_id = xmalloc(kex->session_id_len);
123: memcpy(kex->session_id, hash, kex->session_id_len);
124: }
125:
126: /* sign H */
127: /* XXX hashlen depends on KEX */
128: PRIVSEP(key_sign(server_host_key, &signature, &slen, hash, 20));
129:
130: /* destroy_sensitive_data(); */
131:
132: /* send server hostkey, DH pubkey 'f' and singed H */
133: packet_start(SSH2_MSG_KEXDH_REPLY);
134: packet_put_string(server_host_key_blob, sbloblen);
135: packet_put_bignum2(dh->pub_key); /* f */
136: packet_put_string(signature, slen);
137: packet_send();
138:
139: xfree(signature);
140: xfree(server_host_key_blob);
141: /* have keys, free DH */
142: DH_free(dh);
143:
144: kex_derive_keys(kex, hash, shared_secret);
145: BN_clear_free(shared_secret);
146: kex_finish(kex);
147: }
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