Annotation of src/usr.bin/ssh/kexgexs.c, Revision 1.44
1.44 ! djm 1: /* $OpenBSD: kexgexs.c,v 1.43 2021/01/31 22:55:29 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");
1.43 djm 73: ssh_dispatch_set(ssh, SSH2_MSG_KEX_DH_GEX_REQUEST, &kex_protocol_error);
74:
1.25 djm 75: if ((r = sshpkt_get_u32(ssh, &min)) != 0 ||
76: (r = sshpkt_get_u32(ssh, &nbits)) != 0 ||
77: (r = sshpkt_get_u32(ssh, &max)) != 0 ||
78: (r = sshpkt_get_end(ssh)) != 0)
1.21 markus 79: goto out;
1.25 djm 80: kex->nbits = nbits;
81: kex->min = min;
82: kex->max = max;
1.30 deraadt 83: min = MAXIMUM(DH_GRP_MIN, min);
84: max = MINIMUM(DH_GRP_MAX, max);
85: nbits = MAXIMUM(DH_GRP_MIN, nbits);
86: nbits = MINIMUM(DH_GRP_MAX, nbits);
1.29 dtucker 87:
1.21 markus 88: if (kex->max < kex->min || kex->nbits < kex->min ||
1.29 dtucker 89: kex->max < kex->nbits || kex->max < DH_GRP_MIN) {
1.21 markus 90: r = SSH_ERR_DH_GEX_OUT_OF_RANGE;
91: goto out;
92: }
1.1 markus 93:
94: /* Contact privileged parent */
1.29 dtucker 95: kex->dh = PRIVSEP(choose_dh(min, nbits, max));
1.21 markus 96: if (kex->dh == NULL) {
1.29 dtucker 97: sshpkt_disconnect(ssh, "no matching DH grp found");
1.21 markus 98: r = SSH_ERR_ALLOC_FAIL;
99: goto out;
100: }
1.1 markus 101: debug("SSH2_MSG_KEX_DH_GEX_GROUP sent");
1.34 djm 102: DH_get0_pqg(kex->dh, &dh_p, NULL, &dh_g);
1.21 markus 103: if ((r = sshpkt_start(ssh, SSH2_MSG_KEX_DH_GEX_GROUP)) != 0 ||
1.34 djm 104: (r = sshpkt_put_bignum2(ssh, dh_p)) != 0 ||
105: (r = sshpkt_put_bignum2(ssh, dh_g)) != 0 ||
1.21 markus 106: (r = sshpkt_send(ssh)) != 0)
107: goto out;
1.1 markus 108:
1.21 markus 109: /* Compute our exchange value in parallel with the client */
110: if ((r = dh_gen_key(kex->dh, kex->we_need * 8)) != 0)
111: goto out;
1.1 markus 112:
113: debug("expecting SSH2_MSG_KEX_DH_GEX_INIT");
1.21 markus 114: ssh_dispatch_set(ssh, SSH2_MSG_KEX_DH_GEX_INIT, &input_kex_dh_gex_init);
115: r = 0;
116: out:
117: return r;
118: }
119:
120: static int
1.31 markus 121: input_kex_dh_gex_init(int type, u_int32_t seq, struct ssh *ssh)
1.21 markus 122: {
123: struct kex *kex = ssh->kex;
1.40 djm 124: BIGNUM *dh_client_pub = NULL;
1.34 djm 125: const BIGNUM *pub_key, *dh_p, *dh_g;
1.40 djm 126: struct sshbuf *shared_secret = NULL;
1.42 djm 127: struct sshbuf *server_host_key_blob = NULL;
1.21 markus 128: struct sshkey *server_host_public, *server_host_private;
1.42 djm 129: u_char *signature = NULL;
1.21 markus 130: u_char hash[SSH_DIGEST_MAX_LENGTH];
1.42 djm 131: size_t slen, hashlen;
1.40 djm 132: int r;
1.43 djm 133:
134: debug("SSH2_MSG_KEX_DH_GEX_INIT received");
135: ssh_dispatch_set(ssh, SSH2_MSG_KEX_DH_GEX_INIT, &kex_protocol_error);
1.21 markus 136:
1.41 djm 137: if ((r = kex_load_hostkey(ssh, &server_host_private,
138: &server_host_public)) != 0)
1.21 markus 139: goto out;
1.1 markus 140:
141: /* key, cert */
1.38 djm 142: if ((r = sshpkt_get_bignum2(ssh, &dh_client_pub)) != 0 ||
1.21 markus 143: (r = sshpkt_get_end(ssh)) != 0)
144: goto out;
1.40 djm 145: if ((shared_secret = sshbuf_new()) == NULL) {
1.21 markus 146: r = SSH_ERR_ALLOC_FAIL;
147: goto out;
148: }
1.40 djm 149: if ((r = kex_dh_compute_key(kex, dh_client_pub, shared_secret)) != 0)
1.21 markus 150: goto out;
1.42 djm 151: if ((server_host_key_blob = sshbuf_new()) == NULL) {
152: r = SSH_ERR_ALLOC_FAIL;
153: goto out;
154: }
155: if ((r = sshkey_putb(server_host_public, server_host_key_blob)) != 0)
1.21 markus 156: goto out;
1.40 djm 157:
1.2 djm 158: /* calc H */
1.40 djm 159: DH_get0_key(kex->dh, &pub_key, NULL);
160: DH_get0_pqg(kex->dh, &dh_p, NULL, &dh_g);
1.21 markus 161: hashlen = sizeof(hash);
162: if ((r = kexgex_hash(
1.17 djm 163: kex->hash_alg,
1.36 djm 164: kex->client_version,
165: kex->server_version,
1.42 djm 166: kex->peer,
167: kex->my,
168: server_host_key_blob,
1.21 markus 169: kex->min, kex->nbits, kex->max,
1.34 djm 170: dh_p, dh_g,
1.1 markus 171: dh_client_pub,
1.34 djm 172: pub_key,
1.40 djm 173: sshbuf_ptr(shared_secret), sshbuf_len(shared_secret),
1.21 markus 174: hash, &hashlen)) != 0)
175: goto out;
1.1 markus 176:
177: /* sign H */
1.37 djm 178: if ((r = kex->sign(ssh, server_host_private, server_host_public,
179: &signature, &slen, hash, hashlen, kex->hostkey_alg)) < 0)
1.21 markus 180: goto out;
1.1 markus 181:
1.33 djm 182: /* send server hostkey, DH pubkey 'f' and signed H */
1.21 markus 183: if ((r = sshpkt_start(ssh, SSH2_MSG_KEX_DH_GEX_REPLY)) != 0 ||
1.42 djm 184: (r = sshpkt_put_stringb(ssh, server_host_key_blob)) != 0 ||
1.34 djm 185: (r = sshpkt_put_bignum2(ssh, pub_key)) != 0 || /* f */
1.21 markus 186: (r = sshpkt_put_string(ssh, signature, slen)) != 0 ||
187: (r = sshpkt_send(ssh)) != 0)
188: goto out;
189:
1.44 ! djm 190: if ((r = kex_derive_keys(ssh, hash, hashlen, shared_secret)) != 0 ||
! 191: (r = kex_send_newkeys(ssh)) != 0)
! 192: goto out;
! 193:
! 194: /* retain copy of hostkey used at initial KEX */
! 195: if (kex->initial_hostkey == NULL &&
! 196: (r = sshkey_from_private(server_host_public,
! 197: &kex->initial_hostkey)) != 0)
! 198: goto out;
! 199: /* success */
1.21 markus 200: out:
1.35 djm 201: explicit_bzero(hash, sizeof(hash));
1.21 markus 202: DH_free(kex->dh);
203: kex->dh = NULL;
1.32 jsing 204: BN_clear_free(dh_client_pub);
1.40 djm 205: sshbuf_free(shared_secret);
1.42 djm 206: sshbuf_free(server_host_key_blob);
1.15 djm 207: free(signature);
1.21 markus 208: return r;
1.1 markus 209: }
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