Annotation of src/usr.bin/ssh/kexgexs.c, Revision 1.42
1.42 ! djm 1: /* $OpenBSD: kexgexs.c,v 1.41 2019/01/21 10:05:09 djm Exp $ */
1.1 markus 2: /*
3: * Copyright (c) 2000 Niels Provos. All rights reserved.
4: * Copyright (c) 2001 Markus Friedl. All rights reserved.
5: *
6: * Redistribution and use in source and binary forms, with or without
7: * modification, are permitted provided that the following conditions
8: * are met:
9: * 1. Redistributions of source code must retain the above copyright
10: * notice, this list of conditions and the following disclaimer.
11: * 2. Redistributions in binary form must reproduce the above copyright
12: * notice, this list of conditions and the following disclaimer in the
13: * documentation and/or other materials provided with the distribution.
14: *
15: * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
16: * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
17: * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
18: * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
19: * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
20: * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
21: * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
22: * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
23: * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
24: * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
25: */
26:
1.5 stevesk 27:
1.7 stevesk 28: #include <stdio.h>
1.5 stevesk 29: #include <string.h>
1.8 deraadt 30: #include <signal.h>
1.14 djm 31:
32: #include <openssl/dh.h>
1.1 markus 33:
1.21 markus 34: #include "sshkey.h"
1.8 deraadt 35: #include "cipher.h"
1.21 markus 36: #include "digest.h"
1.1 markus 37: #include "kex.h"
38: #include "log.h"
39: #include "packet.h"
40: #include "dh.h"
41: #include "ssh2.h"
42: #include "compat.h"
1.8 deraadt 43: #ifdef GSSAPI
44: #include "ssh-gss.h"
45: #endif
1.1 markus 46: #include "monitor_wrap.h"
1.21 markus 47: #include "dispatch.h"
48: #include "ssherr.h"
49: #include "sshbuf.h"
1.30 deraadt 50: #include "misc.h"
1.1 markus 51:
1.31 markus 52: static int input_kex_dh_gex_request(int, u_int32_t, struct ssh *);
53: static int input_kex_dh_gex_init(int, u_int32_t, struct ssh *);
1.21 markus 54:
55: int
56: kexgex_server(struct ssh *ssh)
1.1 markus 57: {
1.21 markus 58: ssh_dispatch_set(ssh, SSH2_MSG_KEX_DH_GEX_REQUEST,
59: &input_kex_dh_gex_request);
60: debug("expecting SSH2_MSG_KEX_DH_GEX_REQUEST");
61: return 0;
62: }
1.1 markus 63:
1.21 markus 64: static int
1.31 markus 65: input_kex_dh_gex_request(int type, u_int32_t seq, struct ssh *ssh)
1.21 markus 66: {
67: struct kex *kex = ssh->kex;
68: int r;
69: u_int min = 0, max = 0, nbits = 0;
1.34 djm 70: const BIGNUM *dh_p, *dh_g;
1.1 markus 71:
1.25 djm 72: debug("SSH2_MSG_KEX_DH_GEX_REQUEST received");
73: if ((r = sshpkt_get_u32(ssh, &min)) != 0 ||
74: (r = sshpkt_get_u32(ssh, &nbits)) != 0 ||
75: (r = sshpkt_get_u32(ssh, &max)) != 0 ||
76: (r = sshpkt_get_end(ssh)) != 0)
1.21 markus 77: goto out;
1.25 djm 78: kex->nbits = nbits;
79: kex->min = min;
80: kex->max = max;
1.30 deraadt 81: min = MAXIMUM(DH_GRP_MIN, min);
82: max = MINIMUM(DH_GRP_MAX, max);
83: nbits = MAXIMUM(DH_GRP_MIN, nbits);
84: nbits = MINIMUM(DH_GRP_MAX, nbits);
1.29 dtucker 85:
1.21 markus 86: if (kex->max < kex->min || kex->nbits < kex->min ||
1.29 dtucker 87: kex->max < kex->nbits || kex->max < DH_GRP_MIN) {
1.21 markus 88: r = SSH_ERR_DH_GEX_OUT_OF_RANGE;
89: goto out;
90: }
1.1 markus 91:
92: /* Contact privileged parent */
1.29 dtucker 93: kex->dh = PRIVSEP(choose_dh(min, nbits, max));
1.21 markus 94: if (kex->dh == NULL) {
1.29 dtucker 95: sshpkt_disconnect(ssh, "no matching DH grp found");
1.21 markus 96: r = SSH_ERR_ALLOC_FAIL;
97: goto out;
98: }
1.1 markus 99: debug("SSH2_MSG_KEX_DH_GEX_GROUP sent");
1.34 djm 100: DH_get0_pqg(kex->dh, &dh_p, NULL, &dh_g);
1.21 markus 101: if ((r = sshpkt_start(ssh, SSH2_MSG_KEX_DH_GEX_GROUP)) != 0 ||
1.34 djm 102: (r = sshpkt_put_bignum2(ssh, dh_p)) != 0 ||
103: (r = sshpkt_put_bignum2(ssh, dh_g)) != 0 ||
1.21 markus 104: (r = sshpkt_send(ssh)) != 0)
105: goto out;
1.1 markus 106:
1.21 markus 107: /* Compute our exchange value in parallel with the client */
108: if ((r = dh_gen_key(kex->dh, kex->we_need * 8)) != 0)
109: goto out;
1.1 markus 110:
111: debug("expecting SSH2_MSG_KEX_DH_GEX_INIT");
1.21 markus 112: ssh_dispatch_set(ssh, SSH2_MSG_KEX_DH_GEX_INIT, &input_kex_dh_gex_init);
113: r = 0;
114: out:
115: return r;
116: }
117:
118: static int
1.31 markus 119: input_kex_dh_gex_init(int type, u_int32_t seq, struct ssh *ssh)
1.21 markus 120: {
121: struct kex *kex = ssh->kex;
1.40 djm 122: BIGNUM *dh_client_pub = NULL;
1.34 djm 123: const BIGNUM *pub_key, *dh_p, *dh_g;
1.40 djm 124: struct sshbuf *shared_secret = NULL;
1.42 ! djm 125: struct sshbuf *server_host_key_blob = NULL;
1.21 markus 126: struct sshkey *server_host_public, *server_host_private;
1.42 ! djm 127: u_char *signature = NULL;
1.21 markus 128: u_char hash[SSH_DIGEST_MAX_LENGTH];
1.42 ! djm 129: size_t slen, hashlen;
1.40 djm 130: int r;
1.21 markus 131:
1.41 djm 132: if ((r = kex_load_hostkey(ssh, &server_host_private,
133: &server_host_public)) != 0)
1.21 markus 134: goto out;
1.1 markus 135:
136: /* key, cert */
1.38 djm 137: if ((r = sshpkt_get_bignum2(ssh, &dh_client_pub)) != 0 ||
1.21 markus 138: (r = sshpkt_get_end(ssh)) != 0)
139: goto out;
1.40 djm 140: if ((shared_secret = sshbuf_new()) == NULL) {
1.21 markus 141: r = SSH_ERR_ALLOC_FAIL;
142: goto out;
143: }
1.40 djm 144: if ((r = kex_dh_compute_key(kex, dh_client_pub, shared_secret)) != 0)
1.21 markus 145: goto out;
1.42 ! djm 146: if ((server_host_key_blob = sshbuf_new()) == NULL) {
! 147: r = SSH_ERR_ALLOC_FAIL;
! 148: goto out;
! 149: }
! 150: if ((r = sshkey_putb(server_host_public, server_host_key_blob)) != 0)
1.21 markus 151: goto out;
1.40 djm 152:
1.2 djm 153: /* calc H */
1.40 djm 154: DH_get0_key(kex->dh, &pub_key, NULL);
155: DH_get0_pqg(kex->dh, &dh_p, NULL, &dh_g);
1.21 markus 156: hashlen = sizeof(hash);
157: if ((r = kexgex_hash(
1.17 djm 158: kex->hash_alg,
1.36 djm 159: kex->client_version,
160: kex->server_version,
1.42 ! djm 161: kex->peer,
! 162: kex->my,
! 163: server_host_key_blob,
1.21 markus 164: kex->min, kex->nbits, kex->max,
1.34 djm 165: dh_p, dh_g,
1.1 markus 166: dh_client_pub,
1.34 djm 167: pub_key,
1.40 djm 168: sshbuf_ptr(shared_secret), sshbuf_len(shared_secret),
1.21 markus 169: hash, &hashlen)) != 0)
170: goto out;
1.1 markus 171:
172: /* sign H */
1.37 djm 173: if ((r = kex->sign(ssh, server_host_private, server_host_public,
174: &signature, &slen, hash, hashlen, kex->hostkey_alg)) < 0)
1.21 markus 175: goto out;
1.1 markus 176:
1.33 djm 177: /* send server hostkey, DH pubkey 'f' and signed H */
1.21 markus 178: if ((r = sshpkt_start(ssh, SSH2_MSG_KEX_DH_GEX_REPLY)) != 0 ||
1.42 ! djm 179: (r = sshpkt_put_stringb(ssh, server_host_key_blob)) != 0 ||
1.34 djm 180: (r = sshpkt_put_bignum2(ssh, pub_key)) != 0 || /* f */
1.21 markus 181: (r = sshpkt_put_string(ssh, signature, slen)) != 0 ||
182: (r = sshpkt_send(ssh)) != 0)
183: goto out;
184:
1.40 djm 185: if ((r = kex_derive_keys(ssh, hash, hashlen, shared_secret)) == 0)
1.21 markus 186: r = kex_send_newkeys(ssh);
187: out:
1.35 djm 188: explicit_bzero(hash, sizeof(hash));
1.21 markus 189: DH_free(kex->dh);
190: kex->dh = NULL;
1.32 jsing 191: BN_clear_free(dh_client_pub);
1.40 djm 192: sshbuf_free(shared_secret);
1.42 ! djm 193: sshbuf_free(server_host_key_blob);
1.15 djm 194: free(signature);
1.21 markus 195: return r;
1.1 markus 196: }
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