252 lines
7.3 KiB
C
252 lines
7.3 KiB
C
/* $OpenBSD: auth2-hostbased.c,v 1.26 2016/03/07 19:02:43 djm Exp $ */
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/*
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* Copyright (c) 2000 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 <pwd.h>
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#include <string.h>
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#include <stdarg.h>
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#include "xmalloc.h"
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#include "ssh2.h"
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#include "packet.h"
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#include "buffer.h"
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#include "log.h"
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#include "misc.h"
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#include "servconf.h"
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#include "compat.h"
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#include "key.h"
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#include "hostfile.h"
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#include "auth.h"
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#include "canohost.h"
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#ifdef GSSAPI
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#include "ssh-gss.h"
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#endif
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#include "monitor_wrap.h"
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#include "pathnames.h"
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#include "match.h"
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/* import */
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extern ServerOptions options;
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extern u_char *session_id2;
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extern u_int session_id2_len;
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static int
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userauth_hostbased(Authctxt *authctxt)
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{
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Buffer b;
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Key *key = NULL;
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char *pkalg, *cuser, *chost, *service;
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u_char *pkblob, *sig;
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u_int alen, blen, slen;
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int pktype;
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int authenticated = 0;
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if (!authctxt->valid) {
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debug2("userauth_hostbased: disabled because of invalid user");
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return 0;
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}
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pkalg = packet_get_string(&alen);
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pkblob = packet_get_string(&blen);
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chost = packet_get_string(NULL);
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cuser = packet_get_string(NULL);
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sig = packet_get_string(&slen);
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debug("userauth_hostbased: cuser %s chost %s pkalg %s slen %d",
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cuser, chost, pkalg, slen);
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#ifdef DEBUG_PK
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debug("signature:");
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buffer_init(&b);
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buffer_append(&b, sig, slen);
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buffer_dump(&b);
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buffer_free(&b);
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#endif
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pktype = key_type_from_name(pkalg);
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if (pktype == KEY_UNSPEC) {
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/* this is perfectly legal */
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logit("userauth_hostbased: unsupported "
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"public key algorithm: %s", pkalg);
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goto done;
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}
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key = key_from_blob(pkblob, blen);
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if (key == NULL) {
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error("userauth_hostbased: cannot decode key: %s", pkalg);
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goto done;
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}
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if (key->type != pktype) {
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error("userauth_hostbased: type mismatch for decoded key "
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"(received %d, expected %d)", key->type, pktype);
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goto done;
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}
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if (key_type_plain(key->type) == KEY_RSA &&
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(datafellows & SSH_BUG_RSASIGMD5) != 0) {
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error("Refusing RSA key because peer uses unsafe "
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"signature format");
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goto done;
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}
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if (match_pattern_list(sshkey_ssh_name(key),
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options.hostbased_key_types, 0) != 1) {
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logit("%s: key type %s not in HostbasedAcceptedKeyTypes",
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__func__, sshkey_type(key));
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goto done;
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}
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service = datafellows & SSH_BUG_HBSERVICE ? "ssh-userauth" :
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authctxt->service;
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buffer_init(&b);
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buffer_put_string(&b, session_id2, session_id2_len);
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/* reconstruct packet */
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buffer_put_char(&b, SSH2_MSG_USERAUTH_REQUEST);
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buffer_put_cstring(&b, authctxt->user);
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buffer_put_cstring(&b, service);
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buffer_put_cstring(&b, "hostbased");
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buffer_put_string(&b, pkalg, alen);
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buffer_put_string(&b, pkblob, blen);
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buffer_put_cstring(&b, chost);
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buffer_put_cstring(&b, cuser);
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#ifdef DEBUG_PK
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buffer_dump(&b);
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#endif
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pubkey_auth_info(authctxt, key,
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"client user \"%.100s\", client host \"%.100s\"", cuser, chost);
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/* test for allowed key and correct signature */
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authenticated = 0;
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if (PRIVSEP(hostbased_key_allowed(authctxt->pw, cuser, chost, key)) &&
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PRIVSEP(key_verify(key, sig, slen, buffer_ptr(&b),
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buffer_len(&b))) == 1)
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authenticated = 1;
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buffer_free(&b);
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done:
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debug2("userauth_hostbased: authenticated %d", authenticated);
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if (key != NULL)
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key_free(key);
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free(pkalg);
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free(pkblob);
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free(cuser);
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free(chost);
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free(sig);
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return authenticated;
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}
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/* return 1 if given hostkey is allowed */
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int
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hostbased_key_allowed(struct passwd *pw, const char *cuser, char *chost,
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Key *key)
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{
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struct ssh *ssh = active_state; /* XXX */
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const char *resolvedname, *ipaddr, *lookup, *reason;
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HostStatus host_status;
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int len;
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char *fp;
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if (auth_key_is_revoked(key))
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return 0;
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resolvedname = auth_get_canonical_hostname(ssh, options.use_dns);
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ipaddr = ssh_remote_ipaddr(ssh);
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debug2("%s: chost %s resolvedname %s ipaddr %s", __func__,
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chost, resolvedname, ipaddr);
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if (((len = strlen(chost)) > 0) && chost[len - 1] == '.') {
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debug2("stripping trailing dot from chost %s", chost);
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chost[len - 1] = '\0';
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}
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if (options.hostbased_uses_name_from_packet_only) {
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if (auth_rhosts2(pw, cuser, chost, chost) == 0) {
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debug2("%s: auth_rhosts2 refused "
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"user \"%.100s\" host \"%.100s\" (from packet)",
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__func__, cuser, chost);
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return 0;
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}
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lookup = chost;
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} else {
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if (strcasecmp(resolvedname, chost) != 0)
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logit("userauth_hostbased mismatch: "
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"client sends %s, but we resolve %s to %s",
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chost, ipaddr, resolvedname);
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if (auth_rhosts2(pw, cuser, resolvedname, ipaddr) == 0) {
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debug2("%s: auth_rhosts2 refused "
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"user \"%.100s\" host \"%.100s\" addr \"%.100s\"",
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__func__, cuser, resolvedname, ipaddr);
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return 0;
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}
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lookup = resolvedname;
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}
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debug2("%s: access allowed by auth_rhosts2", __func__);
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if (key_is_cert(key) &&
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key_cert_check_authority(key, 1, 0, lookup, &reason)) {
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error("%s", reason);
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auth_debug_add("%s", reason);
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return 0;
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}
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host_status = check_key_in_hostfiles(pw, key, lookup,
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_PATH_SSH_SYSTEM_HOSTFILE,
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options.ignore_user_known_hosts ? NULL : _PATH_SSH_USER_HOSTFILE);
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/* backward compat if no key has been found. */
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if (host_status == HOST_NEW) {
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host_status = check_key_in_hostfiles(pw, key, lookup,
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_PATH_SSH_SYSTEM_HOSTFILE2,
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options.ignore_user_known_hosts ? NULL :
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_PATH_SSH_USER_HOSTFILE2);
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}
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if (host_status == HOST_OK) {
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if (key_is_cert(key)) {
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if ((fp = sshkey_fingerprint(key->cert->signature_key,
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options.fingerprint_hash, SSH_FP_DEFAULT)) == NULL)
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fatal("%s: sshkey_fingerprint fail", __func__);
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verbose("Accepted certificate ID \"%s\" signed by "
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"%s CA %s from %s@%s", key->cert->key_id,
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key_type(key->cert->signature_key), fp,
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cuser, lookup);
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} else {
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if ((fp = sshkey_fingerprint(key,
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options.fingerprint_hash, SSH_FP_DEFAULT)) == NULL)
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fatal("%s: sshkey_fingerprint fail", __func__);
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verbose("Accepted %s public key %s from %s@%s",
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key_type(key), fp, cuser, lookup);
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}
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free(fp);
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}
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return (host_status == HOST_OK);
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}
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Authmethod method_hostbased = {
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"hostbased",
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userauth_hostbased,
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&options.hostbased_authentication
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};
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