206 lines
5.9 KiB
C
206 lines
5.9 KiB
C
/* $OpenBSD: kexgexc.c,v 1.11 2006/11/06 21:25:28 markus Exp $ */
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/*
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* Copyright (c) 2000 Niels Provos. All rights reserved.
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* Copyright (c) 2001 Markus Friedl. All rights reserved.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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*
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* THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
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* IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
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* OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
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* IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
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* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
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* NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
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* DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
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* THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
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* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
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* THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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*/
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#include "includes.h"
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#include <sys/types.h>
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#include <stdarg.h>
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#include <stdio.h>
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#include <string.h>
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#include <signal.h>
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#include "xmalloc.h"
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#include "buffer.h"
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#include "key.h"
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#include "cipher.h"
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#include "kex.h"
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#include "log.h"
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#include "packet.h"
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#include "dh.h"
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#include "ssh2.h"
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#include "compat.h"
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void
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kexgex_client(Kex *kex)
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{
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BIGNUM *dh_server_pub = NULL, *shared_secret = NULL;
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BIGNUM *p = NULL, *g = NULL;
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Key *server_host_key;
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u_char *kbuf, *hash, *signature = NULL, *server_host_key_blob = NULL;
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u_int klen, slen, sbloblen, hashlen;
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int kout;
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int min, max, nbits;
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DH *dh;
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nbits = dh_estimate(kex->we_need * 8);
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if (datafellows & SSH_OLD_DHGEX) {
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/* Old GEX request */
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packet_start(SSH2_MSG_KEX_DH_GEX_REQUEST_OLD);
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packet_put_int(nbits);
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min = DH_GRP_MIN;
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max = DH_GRP_MAX;
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debug("SSH2_MSG_KEX_DH_GEX_REQUEST_OLD(%u) sent", nbits);
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} else {
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/* New GEX request */
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min = DH_GRP_MIN;
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max = DH_GRP_MAX;
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packet_start(SSH2_MSG_KEX_DH_GEX_REQUEST);
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packet_put_int(min);
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packet_put_int(nbits);
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packet_put_int(max);
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debug("SSH2_MSG_KEX_DH_GEX_REQUEST(%u<%u<%u) sent",
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min, nbits, max);
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}
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#ifdef DEBUG_KEXDH
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fprintf(stderr, "\nmin = %d, nbits = %d, max = %d\n",
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min, nbits, max);
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#endif
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packet_send();
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debug("expecting SSH2_MSG_KEX_DH_GEX_GROUP");
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packet_read_expect(SSH2_MSG_KEX_DH_GEX_GROUP);
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if ((p = BN_new()) == NULL)
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fatal("BN_new");
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packet_get_bignum2(p);
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if ((g = BN_new()) == NULL)
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fatal("BN_new");
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packet_get_bignum2(g);
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packet_check_eom();
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if (BN_num_bits(p) < min || BN_num_bits(p) > max)
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fatal("DH_GEX group out of range: %d !< %d !< %d",
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min, BN_num_bits(p), max);
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dh = dh_new_group(g, p);
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dh_gen_key(dh, kex->we_need * 8);
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#ifdef DEBUG_KEXDH
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DHparams_print_fp(stderr, dh);
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fprintf(stderr, "pub= ");
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BN_print_fp(stderr, dh->pub_key);
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fprintf(stderr, "\n");
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#endif
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debug("SSH2_MSG_KEX_DH_GEX_INIT sent");
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/* generate and send 'e', client DH public key */
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packet_start(SSH2_MSG_KEX_DH_GEX_INIT);
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packet_put_bignum2(dh->pub_key);
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packet_send();
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debug("expecting SSH2_MSG_KEX_DH_GEX_REPLY");
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packet_read_expect(SSH2_MSG_KEX_DH_GEX_REPLY);
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/* key, cert */
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server_host_key_blob = packet_get_string(&sbloblen);
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server_host_key = key_from_blob(server_host_key_blob, sbloblen);
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if (server_host_key == NULL)
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fatal("cannot decode server_host_key_blob");
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if (server_host_key->type != kex->hostkey_type)
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fatal("type mismatch for decoded server_host_key_blob");
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if (kex->verify_host_key == NULL)
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fatal("cannot verify server_host_key");
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if (kex->verify_host_key(server_host_key) == -1)
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fatal("server_host_key verification failed");
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/* DH parameter f, server public DH key */
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if ((dh_server_pub = BN_new()) == NULL)
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fatal("dh_server_pub == NULL");
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packet_get_bignum2(dh_server_pub);
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#ifdef DEBUG_KEXDH
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fprintf(stderr, "dh_server_pub= ");
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BN_print_fp(stderr, dh_server_pub);
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fprintf(stderr, "\n");
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debug("bits %d", BN_num_bits(dh_server_pub));
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#endif
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/* signed H */
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signature = packet_get_string(&slen);
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packet_check_eom();
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if (!dh_pub_is_valid(dh, dh_server_pub))
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packet_disconnect("bad server public DH value");
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klen = DH_size(dh);
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kbuf = xmalloc(klen);
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if ((kout = DH_compute_key(kbuf, dh_server_pub, dh)) < 0)
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fatal("DH_compute_key: failed");
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#ifdef DEBUG_KEXDH
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dump_digest("shared secret", kbuf, kout);
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#endif
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if ((shared_secret = BN_new()) == NULL)
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fatal("kexgex_client: BN_new failed");
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if (BN_bin2bn(kbuf, kout, shared_secret) == NULL)
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fatal("kexgex_client: BN_bin2bn failed");
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memset(kbuf, 0, klen);
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xfree(kbuf);
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if (datafellows & SSH_OLD_DHGEX)
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min = max = -1;
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/* calc and verify H */
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kexgex_hash(
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kex->evp_md,
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kex->client_version_string,
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kex->server_version_string,
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buffer_ptr(&kex->my), buffer_len(&kex->my),
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buffer_ptr(&kex->peer), buffer_len(&kex->peer),
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server_host_key_blob, sbloblen,
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min, nbits, max,
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dh->p, dh->g,
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dh->pub_key,
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dh_server_pub,
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shared_secret,
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&hash, &hashlen
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);
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/* have keys, free DH */
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DH_free(dh);
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xfree(server_host_key_blob);
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BN_clear_free(dh_server_pub);
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if (key_verify(server_host_key, signature, slen, hash, hashlen) != 1)
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fatal("key_verify failed for server_host_key");
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key_free(server_host_key);
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xfree(signature);
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/* save session id */
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if (kex->session_id == NULL) {
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kex->session_id_len = hashlen;
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kex->session_id = xmalloc(kex->session_id_len);
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memcpy(kex->session_id, hash, kex->session_id_len);
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}
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kex_derive_keys(kex, hash, hashlen, shared_secret);
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BN_clear_free(shared_secret);
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kex_finish(kex);
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}
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