Annotation of src/usr.bin/ssh/kexdhs.c, Revision 1.8
1.8 ! markus 1: /* $OpenBSD: kexdhs.c,v 1.7 2006/08/03 03:34:42 deraadt Exp $ */
1.1 markus 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:
1.6 stevesk 26:
1.7 deraadt 27: #include <sys/types.h>
1.6 stevesk 28: #include <string.h>
1.7 deraadt 29: #include <signal.h>
1.1 markus 30:
31: #include "xmalloc.h"
1.7 deraadt 32: #include "buffer.h"
1.1 markus 33: #include "key.h"
1.7 deraadt 34: #include "cipher.h"
1.1 markus 35: #include "kex.h"
36: #include "log.h"
37: #include "packet.h"
38: #include "dh.h"
39: #include "ssh2.h"
1.7 deraadt 40: #ifdef GSSAPI
41: #include "ssh-gss.h"
42: #endif
1.1 markus 43: #include "monitor_wrap.h"
44:
45: void
46: kexdh_server(Kex *kex)
47: {
48: BIGNUM *shared_secret = NULL, *dh_client_pub = NULL;
49: DH *dh;
50: Key *server_host_key;
51: u_char *kbuf, *hash, *signature = NULL, *server_host_key_blob = NULL;
1.8 ! markus 52: u_int sbloblen, klen, hashlen, slen;
! 53: int kout;
1.1 markus 54:
55: /* generate server DH public key */
1.2 djm 56: switch (kex->kex_type) {
57: case KEX_DH_GRP1_SHA1:
58: dh = dh_new_group1();
59: break;
60: case KEX_DH_GRP14_SHA1:
61: dh = dh_new_group14();
62: break;
63: default:
64: fatal("%s: Unexpected KEX type %d", __func__, kex->kex_type);
65: }
1.1 markus 66: dh_gen_key(dh, kex->we_need * 8);
67:
68: debug("expecting SSH2_MSG_KEXDH_INIT");
69: packet_read_expect(SSH2_MSG_KEXDH_INIT);
70:
71: if (kex->load_host_key == NULL)
72: fatal("Cannot load hostkey");
73: server_host_key = kex->load_host_key(kex->hostkey_type);
74: if (server_host_key == NULL)
75: fatal("Unsupported hostkey type %d", kex->hostkey_type);
76:
77: /* key, cert */
78: if ((dh_client_pub = BN_new()) == NULL)
79: fatal("dh_client_pub == NULL");
80: packet_get_bignum2(dh_client_pub);
81: packet_check_eom();
82:
83: #ifdef DEBUG_KEXDH
84: fprintf(stderr, "dh_client_pub= ");
85: BN_print_fp(stderr, dh_client_pub);
86: fprintf(stderr, "\n");
87: debug("bits %d", BN_num_bits(dh_client_pub));
88: #endif
89:
90: #ifdef DEBUG_KEXDH
91: DHparams_print_fp(stderr, dh);
92: fprintf(stderr, "pub= ");
93: BN_print_fp(stderr, dh->pub_key);
94: fprintf(stderr, "\n");
95: #endif
96: if (!dh_pub_is_valid(dh, dh_client_pub))
97: packet_disconnect("bad client public DH value");
98:
99: klen = DH_size(dh);
100: kbuf = xmalloc(klen);
1.8 ! markus 101: if ((kout = DH_compute_key(kbuf, dh_client_pub, dh)) < 0)
! 102: fatal("DH_compute_key: failed");
1.1 markus 103: #ifdef DEBUG_KEXDH
104: dump_digest("shared secret", kbuf, kout);
105: #endif
106: if ((shared_secret = BN_new()) == NULL)
107: fatal("kexdh_server: BN_new failed");
108: BN_bin2bn(kbuf, kout, shared_secret);
109: memset(kbuf, 0, klen);
110: xfree(kbuf);
111:
112: key_to_blob(server_host_key, &server_host_key_blob, &sbloblen);
113:
114: /* calc H */
1.3 djm 115: kex_dh_hash(
1.1 markus 116: kex->client_version_string,
117: kex->server_version_string,
118: buffer_ptr(&kex->peer), buffer_len(&kex->peer),
119: buffer_ptr(&kex->my), buffer_len(&kex->my),
120: server_host_key_blob, sbloblen,
121: dh_client_pub,
122: dh->pub_key,
1.3 djm 123: shared_secret,
124: &hash, &hashlen
1.1 markus 125: );
126: BN_clear_free(dh_client_pub);
127:
128: /* save session id := H */
129: if (kex->session_id == NULL) {
1.3 djm 130: kex->session_id_len = hashlen;
1.1 markus 131: kex->session_id = xmalloc(kex->session_id_len);
132: memcpy(kex->session_id, hash, kex->session_id_len);
133: }
134:
135: /* sign H */
1.3 djm 136: PRIVSEP(key_sign(server_host_key, &signature, &slen, hash, hashlen));
1.1 markus 137:
138: /* destroy_sensitive_data(); */
139:
140: /* send server hostkey, DH pubkey 'f' and singed H */
141: packet_start(SSH2_MSG_KEXDH_REPLY);
142: packet_put_string(server_host_key_blob, sbloblen);
143: packet_put_bignum2(dh->pub_key); /* f */
144: packet_put_string(signature, slen);
145: packet_send();
146:
147: xfree(signature);
148: xfree(server_host_key_blob);
149: /* have keys, free DH */
150: DH_free(dh);
151:
1.3 djm 152: kex_derive_keys(kex, hash, hashlen, shared_secret);
1.1 markus 153: BN_clear_free(shared_secret);
154: kex_finish(kex);
155: }
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