Annotation of src/usr.bin/ssh/kexdhc.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:
35: void
36: kexdh_client(Kex *kex)
37: {
38: BIGNUM *dh_server_pub = NULL, *shared_secret = NULL;
39: DH *dh;
40: Key *server_host_key;
41: u_char *server_host_key_blob = NULL, *signature = NULL;
42: u_char *kbuf, *hash;
1.3 djm 43: u_int klen, kout, slen, sbloblen, hashlen;
1.1 markus 44:
45: /* generate and send 'e', client DH public key */
1.2 djm 46: switch (kex->kex_type) {
47: case KEX_DH_GRP1_SHA1:
48: dh = dh_new_group1();
49: break;
50: case KEX_DH_GRP14_SHA1:
51: dh = dh_new_group14();
52: break;
53: default:
54: fatal("%s: Unexpected KEX type %d", __func__, kex->kex_type);
55: }
1.1 markus 56: dh_gen_key(dh, kex->we_need * 8);
57: packet_start(SSH2_MSG_KEXDH_INIT);
58: packet_put_bignum2(dh->pub_key);
59: packet_send();
60:
61: debug("sending SSH2_MSG_KEXDH_INIT");
62: #ifdef DEBUG_KEXDH
63: DHparams_print_fp(stderr, dh);
64: fprintf(stderr, "pub= ");
65: BN_print_fp(stderr, dh->pub_key);
66: fprintf(stderr, "\n");
67: #endif
68:
69: debug("expecting SSH2_MSG_KEXDH_REPLY");
70: packet_read_expect(SSH2_MSG_KEXDH_REPLY);
71:
72: /* key, cert */
73: server_host_key_blob = packet_get_string(&sbloblen);
74: server_host_key = key_from_blob(server_host_key_blob, sbloblen);
75: if (server_host_key == NULL)
76: fatal("cannot decode server_host_key_blob");
77: if (server_host_key->type != kex->hostkey_type)
78: fatal("type mismatch for decoded server_host_key_blob");
79: if (kex->verify_host_key == NULL)
80: fatal("cannot verify server_host_key");
81: if (kex->verify_host_key(server_host_key) == -1)
82: fatal("server_host_key verification failed");
83:
84: /* DH paramter f, server public DH key */
85: if ((dh_server_pub = BN_new()) == NULL)
86: fatal("dh_server_pub == NULL");
87: packet_get_bignum2(dh_server_pub);
88:
89: #ifdef DEBUG_KEXDH
90: fprintf(stderr, "dh_server_pub= ");
91: BN_print_fp(stderr, dh_server_pub);
92: fprintf(stderr, "\n");
93: debug("bits %d", BN_num_bits(dh_server_pub));
94: #endif
95:
96: /* signed H */
97: signature = packet_get_string(&slen);
98: packet_check_eom();
99:
100: if (!dh_pub_is_valid(dh, dh_server_pub))
101: packet_disconnect("bad server public DH value");
102:
103: klen = DH_size(dh);
104: kbuf = xmalloc(klen);
105: kout = DH_compute_key(kbuf, dh_server_pub, dh);
106: #ifdef DEBUG_KEXDH
107: dump_digest("shared secret", kbuf, kout);
108: #endif
109: if ((shared_secret = BN_new()) == NULL)
110: fatal("kexdh_client: BN_new failed");
111: BN_bin2bn(kbuf, kout, shared_secret);
112: memset(kbuf, 0, klen);
113: xfree(kbuf);
114:
115: /* calc and verify H */
1.3 djm 116: kex_dh_hash(
1.1 markus 117: kex->client_version_string,
118: kex->server_version_string,
119: buffer_ptr(&kex->my), buffer_len(&kex->my),
120: buffer_ptr(&kex->peer), buffer_len(&kex->peer),
121: server_host_key_blob, sbloblen,
122: dh->pub_key,
123: dh_server_pub,
1.3 djm 124: shared_secret,
125: &hash, &hashlen
1.1 markus 126: );
127: xfree(server_host_key_blob);
128: BN_clear_free(dh_server_pub);
129: DH_free(dh);
130:
1.3 djm 131: if (key_verify(server_host_key, signature, slen, hash, hashlen) != 1)
1.1 markus 132: fatal("key_verify failed for server_host_key");
133: key_free(server_host_key);
134: xfree(signature);
135:
136: /* save session id */
137: if (kex->session_id == NULL) {
1.3 djm 138: kex->session_id_len = hashlen;
1.1 markus 139: kex->session_id = xmalloc(kex->session_id_len);
140: memcpy(kex->session_id, hash, kex->session_id_len);
141: }
142:
1.3 djm 143: kex_derive_keys(kex, hash, hashlen, shared_secret);
1.1 markus 144: BN_clear_free(shared_secret);
145: kex_finish(kex);
146: }
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