Annotation of src/usr.bin/ssh/kexgexs.c, Revision 1.47
1.47 ! djm 1: /* $OpenBSD: kexgexs.c,v 1.46 2023/03/29 01:07:48 dtucker 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"
1.8 deraadt 42: #ifdef GSSAPI
43: #include "ssh-gss.h"
44: #endif
1.1 markus 45: #include "monitor_wrap.h"
1.21 markus 46: #include "dispatch.h"
47: #include "ssherr.h"
48: #include "sshbuf.h"
1.30 deraadt 49: #include "misc.h"
1.1 markus 50:
1.31 markus 51: static int input_kex_dh_gex_request(int, u_int32_t, struct ssh *);
52: static int input_kex_dh_gex_init(int, u_int32_t, struct ssh *);
1.21 markus 53:
54: int
55: kexgex_server(struct ssh *ssh)
1.1 markus 56: {
1.21 markus 57: ssh_dispatch_set(ssh, SSH2_MSG_KEX_DH_GEX_REQUEST,
58: &input_kex_dh_gex_request);
59: debug("expecting SSH2_MSG_KEX_DH_GEX_REQUEST");
60: return 0;
61: }
1.1 markus 62:
1.21 markus 63: static int
1.31 markus 64: input_kex_dh_gex_request(int type, u_int32_t seq, struct ssh *ssh)
1.21 markus 65: {
66: struct kex *kex = ssh->kex;
67: int r;
68: u_int min = 0, max = 0, nbits = 0;
1.34 djm 69: const BIGNUM *dh_p, *dh_g;
1.1 markus 70:
1.25 djm 71: debug("SSH2_MSG_KEX_DH_GEX_REQUEST received");
1.43 djm 72: ssh_dispatch_set(ssh, SSH2_MSG_KEX_DH_GEX_REQUEST, &kex_protocol_error);
73:
1.25 djm 74: if ((r = sshpkt_get_u32(ssh, &min)) != 0 ||
75: (r = sshpkt_get_u32(ssh, &nbits)) != 0 ||
76: (r = sshpkt_get_u32(ssh, &max)) != 0 ||
77: (r = sshpkt_get_end(ssh)) != 0)
1.21 markus 78: goto out;
1.25 djm 79: kex->nbits = nbits;
80: kex->min = min;
81: kex->max = max;
1.30 deraadt 82: min = MAXIMUM(DH_GRP_MIN, min);
83: max = MINIMUM(DH_GRP_MAX, max);
84: nbits = MAXIMUM(DH_GRP_MIN, nbits);
85: nbits = MINIMUM(DH_GRP_MAX, nbits);
1.29 dtucker 86:
1.21 markus 87: if (kex->max < kex->min || kex->nbits < kex->min ||
1.29 dtucker 88: kex->max < kex->nbits || kex->max < DH_GRP_MIN) {
1.21 markus 89: r = SSH_ERR_DH_GEX_OUT_OF_RANGE;
90: goto out;
91: }
1.1 markus 92:
93: /* Contact privileged parent */
1.47 ! djm 94: kex->dh = mm_choose_dh(min, nbits, max);
1.21 markus 95: if (kex->dh == NULL) {
1.46 dtucker 96: (void)sshpkt_disconnect(ssh, "no matching DH grp found");
1.21 markus 97: r = SSH_ERR_ALLOC_FAIL;
98: goto out;
99: }
1.1 markus 100: debug("SSH2_MSG_KEX_DH_GEX_GROUP sent");
1.34 djm 101: DH_get0_pqg(kex->dh, &dh_p, NULL, &dh_g);
1.21 markus 102: if ((r = sshpkt_start(ssh, SSH2_MSG_KEX_DH_GEX_GROUP)) != 0 ||
1.34 djm 103: (r = sshpkt_put_bignum2(ssh, dh_p)) != 0 ||
104: (r = sshpkt_put_bignum2(ssh, dh_g)) != 0 ||
1.21 markus 105: (r = sshpkt_send(ssh)) != 0)
106: goto out;
1.1 markus 107:
1.21 markus 108: /* Compute our exchange value in parallel with the client */
109: if ((r = dh_gen_key(kex->dh, kex->we_need * 8)) != 0)
110: goto out;
1.1 markus 111:
112: debug("expecting SSH2_MSG_KEX_DH_GEX_INIT");
1.21 markus 113: ssh_dispatch_set(ssh, SSH2_MSG_KEX_DH_GEX_INIT, &input_kex_dh_gex_init);
114: r = 0;
115: out:
116: return r;
117: }
118:
119: static int
1.31 markus 120: input_kex_dh_gex_init(int type, u_int32_t seq, struct ssh *ssh)
1.21 markus 121: {
122: struct kex *kex = ssh->kex;
1.40 djm 123: BIGNUM *dh_client_pub = NULL;
1.34 djm 124: const BIGNUM *pub_key, *dh_p, *dh_g;
1.40 djm 125: struct sshbuf *shared_secret = NULL;
1.42 djm 126: struct sshbuf *server_host_key_blob = NULL;
1.21 markus 127: struct sshkey *server_host_public, *server_host_private;
1.42 djm 128: u_char *signature = NULL;
1.21 markus 129: u_char hash[SSH_DIGEST_MAX_LENGTH];
1.42 djm 130: size_t slen, hashlen;
1.40 djm 131: int r;
1.43 djm 132:
133: debug("SSH2_MSG_KEX_DH_GEX_INIT received");
134: ssh_dispatch_set(ssh, SSH2_MSG_KEX_DH_GEX_INIT, &kex_protocol_error);
1.21 markus 135:
1.41 djm 136: if ((r = kex_load_hostkey(ssh, &server_host_private,
137: &server_host_public)) != 0)
1.21 markus 138: goto out;
1.1 markus 139:
140: /* key, cert */
1.38 djm 141: if ((r = sshpkt_get_bignum2(ssh, &dh_client_pub)) != 0 ||
1.21 markus 142: (r = sshpkt_get_end(ssh)) != 0)
143: goto out;
1.40 djm 144: if ((shared_secret = sshbuf_new()) == NULL) {
1.21 markus 145: r = SSH_ERR_ALLOC_FAIL;
146: goto out;
147: }
1.40 djm 148: if ((r = kex_dh_compute_key(kex, dh_client_pub, shared_secret)) != 0)
1.21 markus 149: goto out;
1.42 djm 150: if ((server_host_key_blob = sshbuf_new()) == NULL) {
151: r = SSH_ERR_ALLOC_FAIL;
152: goto out;
153: }
154: if ((r = sshkey_putb(server_host_public, server_host_key_blob)) != 0)
1.21 markus 155: goto out;
1.40 djm 156:
1.2 djm 157: /* calc H */
1.40 djm 158: DH_get0_key(kex->dh, &pub_key, NULL);
159: DH_get0_pqg(kex->dh, &dh_p, NULL, &dh_g);
1.21 markus 160: hashlen = sizeof(hash);
161: if ((r = kexgex_hash(
1.17 djm 162: kex->hash_alg,
1.36 djm 163: kex->client_version,
164: kex->server_version,
1.42 djm 165: kex->peer,
166: kex->my,
167: server_host_key_blob,
1.21 markus 168: kex->min, kex->nbits, kex->max,
1.34 djm 169: dh_p, dh_g,
1.1 markus 170: dh_client_pub,
1.34 djm 171: pub_key,
1.40 djm 172: sshbuf_ptr(shared_secret), sshbuf_len(shared_secret),
1.21 markus 173: hash, &hashlen)) != 0)
174: goto out;
1.1 markus 175:
176: /* sign H */
1.37 djm 177: if ((r = kex->sign(ssh, server_host_private, server_host_public,
178: &signature, &slen, hash, hashlen, kex->hostkey_alg)) < 0)
1.21 markus 179: goto out;
1.1 markus 180:
1.33 djm 181: /* send server hostkey, DH pubkey 'f' and signed H */
1.21 markus 182: if ((r = sshpkt_start(ssh, SSH2_MSG_KEX_DH_GEX_REPLY)) != 0 ||
1.42 djm 183: (r = sshpkt_put_stringb(ssh, server_host_key_blob)) != 0 ||
1.34 djm 184: (r = sshpkt_put_bignum2(ssh, pub_key)) != 0 || /* f */
1.21 markus 185: (r = sshpkt_put_string(ssh, signature, slen)) != 0 ||
186: (r = sshpkt_send(ssh)) != 0)
187: goto out;
188:
1.44 djm 189: if ((r = kex_derive_keys(ssh, hash, hashlen, shared_secret)) != 0 ||
190: (r = kex_send_newkeys(ssh)) != 0)
191: goto out;
192:
193: /* retain copy of hostkey used at initial KEX */
194: if (kex->initial_hostkey == NULL &&
195: (r = sshkey_from_private(server_host_public,
196: &kex->initial_hostkey)) != 0)
197: goto out;
198: /* success */
1.21 markus 199: out:
1.35 djm 200: explicit_bzero(hash, sizeof(hash));
1.21 markus 201: DH_free(kex->dh);
202: kex->dh = NULL;
1.32 jsing 203: BN_clear_free(dh_client_pub);
1.40 djm 204: sshbuf_free(shared_secret);
1.42 djm 205: sshbuf_free(server_host_key_blob);
1.15 djm 206: free(signature);
1.21 markus 207: return r;
1.1 markus 208: }
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