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261 lines
6.3 KiB
C
261 lines
6.3 KiB
C
/* $OpenBSD: ssh-keysign.c,v 1.36 2011/02/16 00:31:14 djm Exp $ */
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/*
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* Copyright (c) 2002 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 <fcntl.h>
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#ifdef HAVE_PATHS_H
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#include <paths.h>
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#endif
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#include <pwd.h>
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#include <stdarg.h>
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#include <stdlib.h>
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#include <string.h>
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#include <unistd.h>
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#include <openssl/evp.h>
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#include <openssl/rand.h>
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#include <openssl/rsa.h>
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#include "xmalloc.h"
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#include "log.h"
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#include "key.h"
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#include "ssh.h"
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#include "ssh2.h"
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#include "misc.h"
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#include "buffer.h"
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#include "authfile.h"
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#include "msg.h"
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#include "canohost.h"
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#include "pathnames.h"
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#include "readconf.h"
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#include "uidswap.h"
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/* XXX readconf.c needs these */
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uid_t original_real_uid;
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extern char *__progname;
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static int
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valid_request(struct passwd *pw, char *host, Key **ret, u_char *data,
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u_int datalen)
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{
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Buffer b;
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Key *key = NULL;
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u_char *pkblob;
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u_int blen, len;
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char *pkalg, *p;
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int pktype, fail;
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fail = 0;
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buffer_init(&b);
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buffer_append(&b, data, datalen);
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/* session id, currently limited to SHA1 (20 bytes) or SHA256 (32) */
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p = buffer_get_string(&b, &len);
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if (len != 20 && len != 32)
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fail++;
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xfree(p);
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if (buffer_get_char(&b) != SSH2_MSG_USERAUTH_REQUEST)
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fail++;
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/* server user */
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buffer_skip_string(&b);
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/* service */
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p = buffer_get_string(&b, NULL);
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if (strcmp("ssh-connection", p) != 0)
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fail++;
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xfree(p);
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/* method */
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p = buffer_get_string(&b, NULL);
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if (strcmp("hostbased", p) != 0)
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fail++;
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xfree(p);
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/* pubkey */
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pkalg = buffer_get_string(&b, NULL);
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pkblob = buffer_get_string(&b, &blen);
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pktype = key_type_from_name(pkalg);
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if (pktype == KEY_UNSPEC)
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fail++;
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else if ((key = key_from_blob(pkblob, blen)) == NULL)
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fail++;
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else if (key->type != pktype)
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fail++;
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xfree(pkalg);
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xfree(pkblob);
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/* client host name, handle trailing dot */
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p = buffer_get_string(&b, &len);
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debug2("valid_request: check expect chost %s got %s", host, p);
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if (strlen(host) != len - 1)
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fail++;
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else if (p[len - 1] != '.')
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fail++;
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else if (strncasecmp(host, p, len - 1) != 0)
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fail++;
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xfree(p);
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/* local user */
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p = buffer_get_string(&b, NULL);
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if (strcmp(pw->pw_name, p) != 0)
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fail++;
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xfree(p);
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/* end of message */
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if (buffer_len(&b) != 0)
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fail++;
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buffer_free(&b);
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debug3("valid_request: fail %d", fail);
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if (fail && key != NULL)
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key_free(key);
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else
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*ret = key;
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return (fail ? -1 : 0);
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}
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int
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main(int argc, char **argv)
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{
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Buffer b;
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Options options;
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#define NUM_KEYTYPES 3
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Key *keys[NUM_KEYTYPES], *key = NULL;
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struct passwd *pw;
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int key_fd[NUM_KEYTYPES], i, found, version = 2, fd;
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u_char *signature, *data;
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char *host;
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u_int slen, dlen;
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u_int32_t rnd[256];
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/* Ensure that stdin and stdout are connected */
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if ((fd = open(_PATH_DEVNULL, O_RDWR)) < 2)
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exit(1);
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/* Leave /dev/null fd iff it is attached to stderr */
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if (fd > 2)
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close(fd);
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i = 0;
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key_fd[i++] = open(_PATH_HOST_DSA_KEY_FILE, O_RDONLY);
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key_fd[i++] = open(_PATH_HOST_ECDSA_KEY_FILE, O_RDONLY);
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key_fd[i++] = open(_PATH_HOST_RSA_KEY_FILE, O_RDONLY);
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original_real_uid = getuid(); /* XXX readconf.c needs this */
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if ((pw = getpwuid(original_real_uid)) == NULL)
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fatal("getpwuid failed");
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pw = pwcopy(pw);
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permanently_set_uid(pw);
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seed_rng();
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arc4random_stir();
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#ifdef DEBUG_SSH_KEYSIGN
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log_init("ssh-keysign", SYSLOG_LEVEL_DEBUG3, SYSLOG_FACILITY_AUTH, 0);
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#endif
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/* verify that ssh-keysign is enabled by the admin */
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initialize_options(&options);
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(void)read_config_file(_PATH_HOST_CONFIG_FILE, "", &options, 0);
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fill_default_options(&options);
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if (options.enable_ssh_keysign != 1)
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fatal("ssh-keysign not enabled in %s",
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_PATH_HOST_CONFIG_FILE);
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for (i = found = 0; i < NUM_KEYTYPES; i++) {
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if (key_fd[i] != -1)
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found = 1;
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}
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if (found == 0)
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fatal("could not open any host key");
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OpenSSL_add_all_algorithms();
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for (i = 0; i < 256; i++)
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rnd[i] = arc4random();
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RAND_seed(rnd, sizeof(rnd));
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found = 0;
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for (i = 0; i < NUM_KEYTYPES; i++) {
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keys[i] = NULL;
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if (key_fd[i] == -1)
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continue;
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keys[i] = key_load_private_pem(key_fd[i], KEY_UNSPEC,
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NULL, NULL);
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close(key_fd[i]);
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if (keys[i] != NULL)
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found = 1;
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}
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if (!found)
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fatal("no hostkey found");
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buffer_init(&b);
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if (ssh_msg_recv(STDIN_FILENO, &b) < 0)
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fatal("ssh_msg_recv failed");
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if (buffer_get_char(&b) != version)
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fatal("bad version");
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fd = buffer_get_int(&b);
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if ((fd == STDIN_FILENO) || (fd == STDOUT_FILENO))
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fatal("bad fd");
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if ((host = get_local_name(fd)) == NULL)
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fatal("cannot get local name for fd");
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data = buffer_get_string(&b, &dlen);
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if (valid_request(pw, host, &key, data, dlen) < 0)
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fatal("not a valid request");
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xfree(host);
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found = 0;
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for (i = 0; i < NUM_KEYTYPES; i++) {
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if (keys[i] != NULL &&
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key_equal_public(key, keys[i])) {
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found = 1;
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break;
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}
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}
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if (!found)
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fatal("no matching hostkey found");
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if (key_sign(keys[i], &signature, &slen, data, dlen) != 0)
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fatal("key_sign failed");
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xfree(data);
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/* send reply */
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buffer_clear(&b);
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buffer_put_string(&b, signature, slen);
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if (ssh_msg_send(STDOUT_FILENO, version, &b) == -1)
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fatal("ssh_msg_send failed");
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return (0);
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}
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