Annotation of src/usr.bin/ssh/kexdhc.c, Revision 1.5
1.5 ! djm 1: /* $OpenBSD$ */
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:
26: #include "includes.h"
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:
36: void
37: kexdh_client(Kex *kex)
38: {
39: BIGNUM *dh_server_pub = NULL, *shared_secret = NULL;
40: DH *dh;
41: Key *server_host_key;
42: u_char *server_host_key_blob = NULL, *signature = NULL;
43: u_char *kbuf, *hash;
1.3 djm 44: u_int klen, kout, slen, sbloblen, hashlen;
1.1 markus 45:
46: /* generate and send 'e', client DH public key */
1.2 djm 47: switch (kex->kex_type) {
48: case KEX_DH_GRP1_SHA1:
49: dh = dh_new_group1();
50: break;
51: case KEX_DH_GRP14_SHA1:
52: dh = dh_new_group14();
53: break;
54: default:
55: fatal("%s: Unexpected KEX type %d", __func__, kex->kex_type);
56: }
1.1 markus 57: dh_gen_key(dh, kex->we_need * 8);
58: packet_start(SSH2_MSG_KEXDH_INIT);
59: packet_put_bignum2(dh->pub_key);
60: packet_send();
61:
62: debug("sending SSH2_MSG_KEXDH_INIT");
63: #ifdef DEBUG_KEXDH
64: DHparams_print_fp(stderr, dh);
65: fprintf(stderr, "pub= ");
66: BN_print_fp(stderr, dh->pub_key);
67: fprintf(stderr, "\n");
68: #endif
69:
70: debug("expecting SSH2_MSG_KEXDH_REPLY");
71: packet_read_expect(SSH2_MSG_KEXDH_REPLY);
72:
73: /* key, cert */
74: server_host_key_blob = packet_get_string(&sbloblen);
75: server_host_key = key_from_blob(server_host_key_blob, sbloblen);
76: if (server_host_key == NULL)
77: fatal("cannot decode server_host_key_blob");
78: if (server_host_key->type != kex->hostkey_type)
79: fatal("type mismatch for decoded server_host_key_blob");
80: if (kex->verify_host_key == NULL)
81: fatal("cannot verify server_host_key");
82: if (kex->verify_host_key(server_host_key) == -1)
83: fatal("server_host_key verification failed");
84:
85: /* DH paramter f, server public DH key */
86: if ((dh_server_pub = BN_new()) == NULL)
87: fatal("dh_server_pub == NULL");
88: packet_get_bignum2(dh_server_pub);
89:
90: #ifdef DEBUG_KEXDH
91: fprintf(stderr, "dh_server_pub= ");
92: BN_print_fp(stderr, dh_server_pub);
93: fprintf(stderr, "\n");
94: debug("bits %d", BN_num_bits(dh_server_pub));
95: #endif
96:
97: /* signed H */
98: signature = packet_get_string(&slen);
99: packet_check_eom();
100:
101: if (!dh_pub_is_valid(dh, dh_server_pub))
102: packet_disconnect("bad server public DH value");
103:
104: klen = DH_size(dh);
105: kbuf = xmalloc(klen);
106: kout = DH_compute_key(kbuf, dh_server_pub, dh);
107: #ifdef DEBUG_KEXDH
108: dump_digest("shared secret", kbuf, kout);
109: #endif
110: if ((shared_secret = BN_new()) == NULL)
111: fatal("kexdh_client: BN_new failed");
112: BN_bin2bn(kbuf, kout, shared_secret);
113: memset(kbuf, 0, klen);
114: xfree(kbuf);
115:
116: /* calc and verify H */
1.3 djm 117: kex_dh_hash(
1.1 markus 118: kex->client_version_string,
119: kex->server_version_string,
120: buffer_ptr(&kex->my), buffer_len(&kex->my),
121: buffer_ptr(&kex->peer), buffer_len(&kex->peer),
122: server_host_key_blob, sbloblen,
123: dh->pub_key,
124: dh_server_pub,
1.3 djm 125: shared_secret,
126: &hash, &hashlen
1.1 markus 127: );
128: xfree(server_host_key_blob);
129: BN_clear_free(dh_server_pub);
130: DH_free(dh);
131:
1.3 djm 132: if (key_verify(server_host_key, signature, slen, hash, hashlen) != 1)
1.1 markus 133: fatal("key_verify failed for server_host_key");
134: key_free(server_host_key);
135: xfree(signature);
136:
137: /* save session id */
138: if (kex->session_id == NULL) {
1.3 djm 139: kex->session_id_len = hashlen;
1.1 markus 140: kex->session_id = xmalloc(kex->session_id_len);
141: memcpy(kex->session_id, hash, kex->session_id_len);
142: }
143:
1.3 djm 144: kex_derive_keys(kex, hash, hashlen, shared_secret);
1.1 markus 145: BN_clear_free(shared_secret);
146: kex_finish(kex);
147: }
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