489 lines
12 KiB
C
489 lines
12 KiB
C
/*
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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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RCSID("$OpenBSD: auth2.c,v 1.14 2000/09/07 20:27:49 deraadt Exp $");
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#include <openssl/dsa.h>
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#include <openssl/rsa.h>
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#include <openssl/evp.h>
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#include "xmalloc.h"
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#include "rsa.h"
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#include "ssh.h"
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#include "pty.h"
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#include "packet.h"
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#include "buffer.h"
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#include "cipher.h"
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#include "servconf.h"
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#include "compat.h"
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#include "channels.h"
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#include "bufaux.h"
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#include "ssh2.h"
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#include "auth.h"
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#include "session.h"
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#include "dispatch.h"
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#include "auth.h"
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#include "key.h"
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#include "kex.h"
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#include "dsa.h"
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#include "uidswap.h"
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#include "auth-options.h"
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/* import */
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extern ServerOptions options;
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extern unsigned char *session_id2;
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extern int session_id2_len;
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/* protocol */
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void input_service_request(int type, int plen);
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void input_userauth_request(int type, int plen);
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void protocol_error(int type, int plen);
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/* auth */
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int ssh2_auth_none(struct passwd *pw);
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int ssh2_auth_password(struct passwd *pw);
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int ssh2_auth_pubkey(struct passwd *pw, char *service);
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/* helper */
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struct passwd* auth_set_user(char *u, char *s);
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int user_dsa_key_allowed(struct passwd *pw, Key *key);
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typedef struct Authctxt Authctxt;
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struct Authctxt {
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char *user;
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char *service;
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struct passwd pw;
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int valid;
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};
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static Authctxt *authctxt = NULL;
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static int userauth_success = 0;
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/*
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* loop until userauth_success == TRUE
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*/
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void
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do_authentication2()
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{
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/* turn off skey/kerberos, not supported by SSH2 */
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#ifdef SKEY
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options.skey_authentication = 0;
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#endif
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#ifdef KRB4
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options.kerberos_authentication = 0;
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#endif
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dispatch_init(&protocol_error);
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dispatch_set(SSH2_MSG_SERVICE_REQUEST, &input_service_request);
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dispatch_run(DISPATCH_BLOCK, &userauth_success);
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do_authenticated2();
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}
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void
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protocol_error(int type, int plen)
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{
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log("auth: protocol error: type %d plen %d", type, plen);
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packet_start(SSH2_MSG_UNIMPLEMENTED);
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packet_put_int(0);
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packet_send();
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packet_write_wait();
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}
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void
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input_service_request(int type, int plen)
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{
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unsigned int len;
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int accept = 0;
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char *service = packet_get_string(&len);
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packet_done();
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if (strcmp(service, "ssh-userauth") == 0) {
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if (!userauth_success) {
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accept = 1;
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/* now we can handle user-auth requests */
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dispatch_set(SSH2_MSG_USERAUTH_REQUEST, &input_userauth_request);
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}
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}
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/* XXX all other service requests are denied */
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if (accept) {
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packet_start(SSH2_MSG_SERVICE_ACCEPT);
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packet_put_cstring(service);
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packet_send();
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packet_write_wait();
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} else {
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debug("bad service request %s", service);
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packet_disconnect("bad service request %s", service);
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}
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xfree(service);
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}
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void
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input_userauth_request(int type, int plen)
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{
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static void (*authlog) (const char *fmt,...) = verbose;
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static int attempt = 0;
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unsigned int len;
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int authenticated = 0;
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char *user, *service, *method, *authmsg = NULL;
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struct passwd *pw;
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if (++attempt == AUTH_FAIL_MAX)
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packet_disconnect("too many failed userauth_requests");
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user = packet_get_string(&len);
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service = packet_get_string(&len);
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method = packet_get_string(&len);
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debug("userauth-request for user %s service %s method %s", user, service, method);
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/* XXX we only allow the ssh-connection service */
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pw = auth_set_user(user, service);
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if (pw && strcmp(service, "ssh-connection")==0) {
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if (strcmp(method, "none") == 0) {
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authenticated = ssh2_auth_none(pw);
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} else if (strcmp(method, "password") == 0) {
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authenticated = ssh2_auth_password(pw);
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} else if (strcmp(method, "publickey") == 0) {
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authenticated = ssh2_auth_pubkey(pw, service);
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}
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}
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if (authenticated && pw && pw->pw_uid == 0 && !options.permit_root_login) {
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authenticated = 0;
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log("ROOT LOGIN REFUSED FROM %.200s",
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get_canonical_hostname());
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}
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/* Raise logging level */
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if (authenticated == 1 ||
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attempt == AUTH_FAIL_LOG ||
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strcmp(method, "password") == 0)
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authlog = log;
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/* Log before sending the reply */
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if (authenticated == 1) {
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authmsg = "Accepted";
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} else if (authenticated == 0) {
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authmsg = "Failed";
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} else {
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authmsg = "Postponed";
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}
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authlog("%s %s for %.200s from %.200s port %d ssh2",
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authmsg,
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method,
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pw && pw->pw_uid == 0 ? "ROOT" : user,
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get_remote_ipaddr(),
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get_remote_port());
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/* XXX todo: check if multiple auth methods are needed */
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if (authenticated == 1) {
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/* turn off userauth */
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dispatch_set(SSH2_MSG_USERAUTH_REQUEST, &protocol_error);
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packet_start(SSH2_MSG_USERAUTH_SUCCESS);
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packet_send();
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packet_write_wait();
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/* now we can break out */
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userauth_success = 1;
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} else if (authenticated == 0) {
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packet_start(SSH2_MSG_USERAUTH_FAILURE);
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packet_put_cstring("publickey,password"); /* XXX dynamic */
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packet_put_char(0); /* XXX partial success, unused */
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packet_send();
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packet_write_wait();
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}
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xfree(service);
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xfree(user);
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xfree(method);
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}
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int
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ssh2_auth_none(struct passwd *pw)
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{
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packet_done();
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return auth_password(pw, "");
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}
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int
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ssh2_auth_password(struct passwd *pw)
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{
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char *password;
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int authenticated = 0;
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int change;
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unsigned int len;
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change = packet_get_char();
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if (change)
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log("password change not supported");
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password = packet_get_string(&len);
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packet_done();
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if (options.password_authentication &&
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auth_password(pw, password) == 1)
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authenticated = 1;
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memset(password, 0, len);
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xfree(password);
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return authenticated;
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}
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int
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ssh2_auth_pubkey(struct passwd *pw, char *service)
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{
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Buffer b;
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Key *key;
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char *pkalg, *pkblob, *sig;
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unsigned int alen, blen, slen;
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int have_sig;
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int authenticated = 0;
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if (options.dsa_authentication == 0) {
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debug("pubkey auth disabled");
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return 0;
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}
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have_sig = packet_get_char();
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pkalg = packet_get_string(&alen);
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if (strcmp(pkalg, KEX_DSS) != 0) {
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xfree(pkalg);
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log("bad pkalg %s", pkalg); /*XXX*/
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return 0;
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}
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pkblob = packet_get_string(&blen);
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key = dsa_key_from_blob(pkblob, blen);
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if (key != NULL) {
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if (have_sig) {
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sig = packet_get_string(&slen);
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packet_done();
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buffer_init(&b);
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if (datafellows & SSH_COMPAT_SESSIONID_ENCODING) {
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buffer_put_string(&b, session_id2, session_id2_len);
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} else {
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buffer_append(&b, session_id2, session_id2_len);
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}
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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, pw->pw_name);
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buffer_put_cstring(&b,
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datafellows & SSH_BUG_PUBKEYAUTH ?
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"ssh-userauth" :
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service);
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buffer_put_cstring(&b, "publickey");
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buffer_put_char(&b, have_sig);
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buffer_put_cstring(&b, KEX_DSS);
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buffer_put_string(&b, pkblob, blen);
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#ifdef DEBUG_DSS
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buffer_dump(&b);
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#endif
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/* test for correct signature */
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if (user_dsa_key_allowed(pw, key) &&
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dsa_verify(key, sig, slen, buffer_ptr(&b), buffer_len(&b)) == 1)
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authenticated = 1;
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buffer_clear(&b);
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xfree(sig);
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} else {
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packet_done();
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debug("test key...");
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/* test whether pkalg/pkblob are acceptable */
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/* XXX fake reply and always send PK_OK ? */
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/*
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* XXX this allows testing whether a user is allowed
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* to login: if you happen to have a valid pubkey this
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* message is sent. the message is NEVER sent at all
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* if a user is not allowed to login. is this an
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* issue? -markus
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*/
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if (user_dsa_key_allowed(pw, key)) {
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packet_start(SSH2_MSG_USERAUTH_PK_OK);
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packet_put_string(pkalg, alen);
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packet_put_string(pkblob, blen);
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packet_send();
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packet_write_wait();
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authenticated = -1;
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}
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}
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key_free(key);
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}
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xfree(pkalg);
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xfree(pkblob);
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return authenticated;
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}
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/* set and get current user */
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struct passwd*
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auth_get_user(void)
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{
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return (authctxt != NULL && authctxt->valid) ? &authctxt->pw : NULL;
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}
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struct passwd*
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auth_set_user(char *u, char *s)
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{
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struct passwd *pw, *copy;
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if (authctxt == NULL) {
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authctxt = xmalloc(sizeof(*authctxt));
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authctxt->valid = 0;
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authctxt->user = xstrdup(u);
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authctxt->service = xstrdup(s);
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setproctitle("%s", u);
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pw = getpwnam(u);
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if (!pw || !allowed_user(pw)) {
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log("auth_set_user: illegal user %s", u);
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return NULL;
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}
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copy = &authctxt->pw;
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memset(copy, 0, sizeof(*copy));
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copy->pw_name = xstrdup(pw->pw_name);
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copy->pw_passwd = xstrdup(pw->pw_passwd);
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copy->pw_uid = pw->pw_uid;
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copy->pw_gid = pw->pw_gid;
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copy->pw_class = xstrdup(pw->pw_class);
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copy->pw_dir = xstrdup(pw->pw_dir);
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copy->pw_shell = xstrdup(pw->pw_shell);
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authctxt->valid = 1;
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} else {
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if (strcmp(u, authctxt->user) != 0 ||
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strcmp(s, authctxt->service) != 0) {
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log("auth_set_user: missmatch: (%s,%s)!=(%s,%s)",
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u, s, authctxt->user, authctxt->service);
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return NULL;
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}
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}
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return auth_get_user();
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}
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/* return 1 if user allows given key */
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int
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user_dsa_key_allowed(struct passwd *pw, Key *key)
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{
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char line[8192], file[1024];
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int found_key = 0;
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unsigned int bits = -1;
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FILE *f;
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unsigned long linenum = 0;
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struct stat st;
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Key *found;
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/* Temporarily use the user's uid. */
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temporarily_use_uid(pw->pw_uid);
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/* The authorized keys. */
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snprintf(file, sizeof file, "%.500s/%.100s", pw->pw_dir,
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SSH_USER_PERMITTED_KEYS2);
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/* Fail quietly if file does not exist */
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if (stat(file, &st) < 0) {
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/* Restore the privileged uid. */
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restore_uid();
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return 0;
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}
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/* Open the file containing the authorized keys. */
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f = fopen(file, "r");
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if (!f) {
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/* Restore the privileged uid. */
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restore_uid();
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return 0;
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}
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if (options.strict_modes) {
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int fail = 0;
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char buf[1024];
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/* Check open file in order to avoid open/stat races */
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if (fstat(fileno(f), &st) < 0 ||
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(st.st_uid != 0 && st.st_uid != pw->pw_uid) ||
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(st.st_mode & 022) != 0) {
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snprintf(buf, sizeof buf, "DSA authentication refused for %.100s: "
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"bad ownership or modes for '%s'.", pw->pw_name, file);
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fail = 1;
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} else {
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/* Check path to SSH_USER_PERMITTED_KEYS */
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int i;
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static const char *check[] = {
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"", SSH_USER_DIR, NULL
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};
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for (i = 0; check[i]; i++) {
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snprintf(line, sizeof line, "%.500s/%.100s",
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pw->pw_dir, check[i]);
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if (stat(line, &st) < 0 ||
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(st.st_uid != 0 && st.st_uid != pw->pw_uid) ||
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(st.st_mode & 022) != 0) {
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snprintf(buf, sizeof buf,
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"DSA authentication refused for %.100s: "
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"bad ownership or modes for '%s'.",
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pw->pw_name, line);
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fail = 1;
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break;
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}
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}
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}
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if (fail) {
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fclose(f);
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log("%s",buf);
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restore_uid();
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return 0;
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}
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}
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found_key = 0;
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found = key_new(KEY_DSA);
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while (fgets(line, sizeof(line), f)) {
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char *cp, *options = NULL;
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linenum++;
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/* Skip leading whitespace, empty and comment lines. */
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for (cp = line; *cp == ' ' || *cp == '\t'; cp++)
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;
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if (!*cp || *cp == '\n' || *cp == '#')
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continue;
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bits = key_read(found, &cp);
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if (bits == 0) {
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/* no key? check if there are options for this key */
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int quoted = 0;
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options = cp;
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for (; *cp && (quoted || (*cp != ' ' && *cp != '\t')); cp++) {
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if (*cp == '\\' && cp[1] == '"')
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cp++; /* Skip both */
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else if (*cp == '"')
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quoted = !quoted;
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}
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/* Skip remaining whitespace. */
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for (; *cp == ' ' || *cp == '\t'; cp++)
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;
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bits = key_read(found, &cp);
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if (bits == 0) {
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/* still no key? advance to next line*/
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continue;
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}
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}
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if (key_equal(found, key) &&
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auth_parse_options(pw, options, linenum) == 1) {
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found_key = 1;
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debug("matching key found: file %s, line %ld",
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file, linenum);
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break;
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}
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}
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restore_uid();
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fclose(f);
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key_free(found);
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return found_key;
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}
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