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* Copyright (c) 2000 Markus Friedl. All rights reserved.
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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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* 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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* 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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RCSID("$OpenBSD: auth2-hostbased.c,v 1.6 2004/01/19 21:25:15 markus Exp $");
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#include "monitor_wrap.h"
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#include "pathnames.h"
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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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userauth_hostbased(Authctxt *authctxt)
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char *pkalg, *cuser, *chost, *service;
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u_int alen, blen, slen;
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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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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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buffer_append(&b, sig, slen);
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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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key = key_from_blob(pkblob, blen);
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error("userauth_hostbased: cannot decode key: %s", pkalg);
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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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service = datafellows & SSH_BUG_HBSERVICE ? "ssh-userauth" :
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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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/* test for allowed key and correct signature */
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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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debug2("userauth_hostbased: authenticated %d", authenticated);
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return authenticated;
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/* return 1 if given hostkey is allowed */
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hostbased_key_allowed(struct passwd *pw, const char *cuser, char *chost,
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const char *resolvedname, *ipaddr, *lookup;
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HostStatus host_status;
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resolvedname = get_canonical_hostname(options.use_dns);
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ipaddr = get_remote_ipaddr();
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debug2("userauth_hostbased: chost %s resolvedname %s ipaddr %s",
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chost, resolvedname, ipaddr);
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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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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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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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lookup = resolvedname;
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debug2("userauth_hostbased: access allowed by auth_rhosts2");
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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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return (host_status == HOST_OK);
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Authmethod method_hostbased = {
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&options.hostbased_authentication