Annotation of src/usr.bin/ssh/kexgexs.c, Revision 1.1.4.1
1.1 markus 1: /*
2: * Copyright (c) 2000 Niels Provos. All rights reserved.
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"
1.1.4.1 ! margarid 27: RCSID("$OpenBSD: kexgexs.c,v 1.1 2003/02/16 17:09:57 markus Exp $");
1.1 markus 28:
29: #include "xmalloc.h"
30: #include "key.h"
31: #include "kex.h"
32: #include "log.h"
33: #include "packet.h"
34: #include "dh.h"
35: #include "ssh2.h"
36: #include "compat.h"
37: #include "monitor_wrap.h"
38:
39: void
40: kexgex_server(Kex *kex)
41: {
42: BIGNUM *shared_secret = NULL, *dh_client_pub = NULL;
43: Key *server_host_key;
44: DH *dh;
45: u_char *kbuf, *hash, *signature = NULL, *server_host_key_blob = NULL;
46: u_int sbloblen, klen, kout, slen;
47: int min = -1, max = -1, nbits = -1, type;
48:
49: if (kex->load_host_key == NULL)
50: fatal("Cannot load hostkey");
51: server_host_key = kex->load_host_key(kex->hostkey_type);
52: if (server_host_key == NULL)
53: fatal("Unsupported hostkey type %d", kex->hostkey_type);
54:
55: type = packet_read();
56: switch (type) {
57: case SSH2_MSG_KEX_DH_GEX_REQUEST:
58: debug("SSH2_MSG_KEX_DH_GEX_REQUEST received");
59: min = packet_get_int();
60: nbits = packet_get_int();
61: max = packet_get_int();
62: min = MAX(DH_GRP_MIN, min);
63: max = MIN(DH_GRP_MAX, max);
64: break;
65: case SSH2_MSG_KEX_DH_GEX_REQUEST_OLD:
66: debug("SSH2_MSG_KEX_DH_GEX_REQUEST_OLD received");
67: nbits = packet_get_int();
68: min = DH_GRP_MIN;
69: max = DH_GRP_MAX;
70: /* unused for old GEX */
71: break;
72: default:
73: fatal("protocol error during kex, no DH_GEX_REQUEST: %d", type);
74: }
75: packet_check_eom();
76:
77: if (max < min || nbits < min || max < nbits)
78: fatal("DH_GEX_REQUEST, bad parameters: %d !< %d !< %d",
79: min, nbits, max);
80:
81: /* Contact privileged parent */
82: dh = PRIVSEP(choose_dh(min, nbits, max));
83: if (dh == NULL)
84: packet_disconnect("Protocol error: no matching DH grp found");
85:
86: debug("SSH2_MSG_KEX_DH_GEX_GROUP sent");
87: packet_start(SSH2_MSG_KEX_DH_GEX_GROUP);
88: packet_put_bignum2(dh->p);
89: packet_put_bignum2(dh->g);
90: packet_send();
91:
92: /* flush */
93: packet_write_wait();
94:
95: /* Compute our exchange value in parallel with the client */
96: dh_gen_key(dh, kex->we_need * 8);
97:
98: debug("expecting SSH2_MSG_KEX_DH_GEX_INIT");
99: packet_read_expect(SSH2_MSG_KEX_DH_GEX_INIT);
100:
101: /* key, cert */
102: if ((dh_client_pub = BN_new()) == NULL)
103: fatal("dh_client_pub == NULL");
104: packet_get_bignum2(dh_client_pub);
105: packet_check_eom();
106:
107: #ifdef DEBUG_KEXDH
108: fprintf(stderr, "dh_client_pub= ");
109: BN_print_fp(stderr, dh_client_pub);
110: fprintf(stderr, "\n");
111: debug("bits %d", BN_num_bits(dh_client_pub));
112: #endif
113:
114: #ifdef DEBUG_KEXDH
115: DHparams_print_fp(stderr, dh);
116: fprintf(stderr, "pub= ");
117: BN_print_fp(stderr, dh->pub_key);
118: fprintf(stderr, "\n");
119: #endif
120: if (!dh_pub_is_valid(dh, dh_client_pub))
121: packet_disconnect("bad client public DH value");
122:
123: klen = DH_size(dh);
124: kbuf = xmalloc(klen);
125: kout = DH_compute_key(kbuf, dh_client_pub, dh);
126: #ifdef DEBUG_KEXDH
127: dump_digest("shared secret", kbuf, kout);
128: #endif
129: if ((shared_secret = BN_new()) == NULL)
130: fatal("kexgex_server: BN_new failed");
131: BN_bin2bn(kbuf, kout, shared_secret);
132: memset(kbuf, 0, klen);
133: xfree(kbuf);
134:
135: key_to_blob(server_host_key, &server_host_key_blob, &sbloblen);
136:
137: if (type == SSH2_MSG_KEX_DH_GEX_REQUEST_OLD)
138: min = max = -1;
139:
140: /* calc H */ /* XXX depends on 'kex' */
141: hash = kexgex_hash(
142: kex->client_version_string,
143: kex->server_version_string,
144: buffer_ptr(&kex->peer), buffer_len(&kex->peer),
145: buffer_ptr(&kex->my), buffer_len(&kex->my),
146: server_host_key_blob, sbloblen,
147: min, nbits, max,
148: dh->p, dh->g,
149: dh_client_pub,
150: dh->pub_key,
151: shared_secret
152: );
153: BN_clear_free(dh_client_pub);
154:
155: /* save session id := H */
156: /* XXX hashlen depends on KEX */
157: if (kex->session_id == NULL) {
158: kex->session_id_len = 20;
159: kex->session_id = xmalloc(kex->session_id_len);
160: memcpy(kex->session_id, hash, kex->session_id_len);
161: }
162:
163: /* sign H */
164: /* XXX hashlen depends on KEX */
165: PRIVSEP(key_sign(server_host_key, &signature, &slen, hash, 20));
166:
167: /* destroy_sensitive_data(); */
168:
169: /* send server hostkey, DH pubkey 'f' and singed H */
170: debug("SSH2_MSG_KEX_DH_GEX_REPLY sent");
171: packet_start(SSH2_MSG_KEX_DH_GEX_REPLY);
172: packet_put_string(server_host_key_blob, sbloblen);
173: packet_put_bignum2(dh->pub_key); /* f */
174: packet_put_string(signature, slen);
175: packet_send();
176:
177: xfree(signature);
178: xfree(server_host_key_blob);
179: /* have keys, free DH */
180: DH_free(dh);
181:
182: kex_derive_keys(kex, hash, shared_secret);
183: BN_clear_free(shared_secret);
184:
185: kex_finish(kex);
186: }
![[BACK]](/icons/back.gif){kind=icon}
Return to kexgexs.c CVS log ![[TXT]](/icons/text.gif){kind=icon}
![[DIR]](/icons/dir.gif){kind=icon}
Up to [local] / src / usr.bin / ssh