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ファイル改竄検知システム導入(SL6)

クラッカーによるLinuxサーバーのファイルの改竄を検知するシステムを導入する。
ここでは、ファイル改竄検知システムにホスト型IDS(IDS=Intrusion Detection System)のTripwireを導入する。

Tripwireインストール

[root@host3 ~]# yum install -y perl  ← 必要なのでインストール

[root@host3 ~]# yum --enablerepo=epel -y install tripwire  ← EPELからインストール
・
・
・
Complete!

[root@host3 ~]# tripwire-setup-keyfiles

# 以下のようにパスフレーズを何度か求められるので入力する
Enter the site keyfile passphrase:  ← 任意のサイトパスフレーズ応答
Verify the site keyfile passphrase:  ← 任意のサイトパスフレーズ応答(確認)

Enter the local keyfile passphrase:  ← 任意のローカルパスフレーズ応答
Verify the local keyfile passphrase:  ← 任意のローカルパスフレーズ応答(確認)

Please enter your site passphrase:  ← サイトパスフレーズ応答

Please enter your site passphrase:  ← サイトパスフレーズ応答

Tripwire設定

Tripwire設定

[root@host3 ~]# vi /etc/tripwire/twcfg.txt  ← Tripwire設定ファイル編集
LOOSEDIRECTORYCHECKING =true  ← ファイル変更時に所属ディレクトリの変更を通知しないようにする

REPORTLEVEL   =4  ← リポートレベルを変更する

[root@host3 ~]# twadmin -m F -c /etc/tripwire/tw.cfg -S /etc/tripwire/site.key /etc/tripwire/twcfg.txt
 ← Tripwire設定ファイル(暗号署名版)作成
Please enter your site passphrase: ← サイトパスフレーズ応答
Wrote configuration file: /etc/tripwire/tw.cfg

[root@host3 ~]# rm -f /etc/tripwire/twcfg.txt ← Tripwire設定ファイル(テキスト版)削除

※Tripwire設定ファイル(テキスト版)を復元する場合
[root@host3 ~]# twadmin -m f -c /etc/tripwire/tw.cfg > /etc/tripwire/twcfg.txt

ポリシーファイル設定

ポリシーファイル最適化スクリプトが配布されてるので使わせていただきます。

[root@host3 ~]# vi /etc/tripwire/twpolmake.pl ← ポリシーファイル最適化スクリプト作成
#!/usr/bin/perl
# Tripwire Policy File customize tool
# ----------------------------------------------------------------
# Copyright (C) 2003 Hiroaki Izumi
# This program is free software; you can redistribute it and/or
# modify it under the terms of the GNU General Public License
# as published by the Free Software Foundation; either version 2
# of the License, or (at your option) any later version.
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
# GNU General Public License for more details.
# You should have received a copy of the GNU General Public License
# along with this program; if not, write to the Free Software
# Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA  02111-1307, USA.
# ----------------------------------------------------------------
# Usage:
#    perl twpolmake.pl {Pol file}
# ----------------------------------------------------------------
#
$POLFILE=$ARGV[0];

open(POL,"$POLFILE") or die "open error: $POLFILE" ;
my($myhost,$thost) ;
my($sharp,$tpath,$cond) ;
my($INRULE) = 0 ;

while (<POL>) {
    chomp;
    if (($thost) = /^HOSTNAME\s*=\s*(.*)\s*;/) {
        $myhost = `hostname` ; chomp($myhost) ;
        if ($thost ne $myhost) {
            $_="HOSTNAME=\"$myhost\";" ;
        }
    }
    elsif ( /^{/ ) {
        $INRULE=1 ;
    }
    elsif ( /^}/ ) {
        $INRULE=0 ;
    }
    elsif ($INRULE == 1 and ($sharp,$tpath,$cond) = /^(\s*\#?\s*)(\/\S+)\b(\s+->\s+.+)$/) {
        $ret = ($sharp =~ s/\#//g) ;
        if ($tpath eq '/sbin/e2fsadm' ) {
            $cond =~ s/;\s+(tune2fs.*)$/; \#$1/ ;
        }
        if (! -s $tpath) {
            $_ = "$sharp#$tpath$cond" if ($ret == 0) ;
        }
        else {
            $_ = "$sharp$tpath$cond" ;
        }
    }
    print "$_\n" ;
}
close(POL) ;

[root@host3 ~]# perl /etc/tripwire/twpolmake.pl /etc/tripwire/twpol.txt > /etc/tripwire/twpol.txt.new
 ← ポリシーファイル最適化

[root@hostt3 ~]# twadmin -m P -c /etc/tripwire/tw.cfg -p /etc/tripwire/tw.pol -S /etc/tripwire/site.key /etc/tripwiretwpol.txt.new
 ← 最適化済ポリシーファイルを元にポリシーファイル(暗号署名版)作成
Please enter your site passphrase:  ← サイトパスフレーズ応答
Wrote policy file: /etc/tripwire/tw.pol

[root@host3 ~]# rm -f /etc/tripwire/twpol.txt* ← ポリシーファイル(テキスト版)削除

※ポリシーファイル(テキスト版)を復元する場合
[root@host3 ~]# twadmin -m p -c /etc/tripwire/tw.cfg -p /etc/tripwire/tw.pol -S /etc/tripwire/site.key > /etc/tripwire/twpol.txt

データベース作成

[root@host3 ~]# tripwire -m i -s -c /etc/tripwire/tw.cfg ← Tripwireデータベース作成
Please enter your local passphrase: ← ローカルパスフレーズ応答

Tripwire確認

[root@host3 ~]# tripwire -m c -s -c /etc/tripwire/tw.cfg
Open Source Tripwire(R) 2.4.1 Integrity Check Report

Report generated by:          root
Report created on:            2011年06月19日 08時56分55秒
Database last updated on:     Never

===============================================================================
Report Summary:
===============================================================================

Host name:                    host3.sudachi.jp
Host IP address:              Unknown IP
Host ID:                      None
Policy file used:             /etc/tripwire/tw.pol
Configuration file used:      /etc/tripwire/tw.cfg
Database file used:           /var/lib/tripwire/host3.sudachi.jp.twd
Command line used:            tripwire -m c -s -c /etc/tripwire/tw.cfg 

===============================================================================
Rule Summary: 
===============================================================================

-------------------------------------------------------------------------------
  Section: Unix File System
-------------------------------------------------------------------------------

  Rule Name                       Severity Level    Added    Removed  Modified 
  ---------                       --------------    -----    -------  -------- 
  Invariant Directories           66                0        0        0        
  Temporary directories           33                0        0        0        
* Tripwire Data Files             100               1        0        0        
  Critical devices                100               0        0        0        
  (/proc/kcore)
  User binaries                   66                0        0        0        
  Tripwire Binaries               100               0        0        0        
  Libraries                       66                0        0        0        
  File System and Disk Administraton Programs
                                  100               0        0        0        
  Kernel Administration Programs  100               0        0        0        
  Networking Programs             100               0        0        0        
  System Administration Programs  100               0        0        0        
  Hardware and Device Control Programs
                                  100               0        0        0        
  System Information Programs     100               0        0        0        
  Application Information Programs
                                  100               0        0        0        
  (/sbin/rtmon)
  Shell Related Programs          100               0        0        0        
  (/sbin/getkey)
  Operating System Utilities      100               0        0        0        
  Critical Utility Sym-Links      100               0        0        0        
  Shell Binaries                  100               0        0        0        
  Critical system boot files      100               0        0        0        
  System boot changes             100               0        0        0        
  OS executables and libraries    100               0        0        0        
  Critical configuration files    100               0        0        0        
  Security Control                100               0        0        0        
  Login Scripts                   100               0        0        0        
  Root config files               100               0        0        0        

Total objects scanned:  9972
Total violations found:  1

===============================================================================
Object Summary: 
===============================================================================

-------------------------------------------------------------------------------
# Section: Unix File System
-------------------------------------------------------------------------------

-------------------------------------------------------------------------------
Rule Name: Tripwire Data Files (/var/lib/tripwire)
Severity Level: 100
-------------------------------------------------------------------------------

Added:
"/var/lib/tripwire/host3.sudachi.jp.twd"

===============================================================================
Error Report: 
===============================================================================

No Errors

-------------------------------------------------------------------------------
*** End of report ***

Open Source Tripwire 2.4 Portions copyright 2000 Tripwire, Inc. Tripwire is a registered
trademark of Tripwire, Inc. This software comes with ABSOLUTELY NO WARRANTY;
for details use --version. This is free software which may be redistributed
or modified only under certain conditions; see COPYING for details.
All rights reserved.

Tripwire定期自動実行設定