github.com/krum110487/go-htaccess@v0.0.0-20240316004156-60641c8e7598/tests/data/apache_2_2_34/manual/misc/security_tips.html.en (about) 1 <?xml version="1.0" encoding="ISO-8859-1"?> 2 <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd"> 3 <html xmlns="http://www.w3.org/1999/xhtml" lang="en" xml:lang="en"><head> 4 <meta content="text/html; charset=ISO-8859-1" http-equiv="Content-Type" /> 5 <!-- 6 XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX 7 This file is generated from xml source: DO NOT EDIT 8 XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX 9 --> 10 <title>Security Tips - Apache HTTP Server Version 2.2</title> 11 <link href="../style/css/manual.css" rel="stylesheet" media="all" type="text/css" title="Main stylesheet" /> 12 <link href="../style/css/manual-loose-100pc.css" rel="alternate stylesheet" media="all" type="text/css" title="No Sidebar - Default font size" /> 13 <link href="../style/css/manual-print.css" rel="stylesheet" media="print" type="text/css" /><link rel="stylesheet" type="text/css" href="../style/css/prettify.css" /> 14 <script src="../style/scripts/prettify.min.js" type="text/javascript"> 15 </script> 16 17 <link href="../images/favicon.ico" rel="shortcut icon" /><link href="http://httpd.apache.org/docs/current/misc/security_tips.html" rel="canonical" /></head> 18 <body id="manual-page"><div id="page-header"> 19 <p class="menu"><a href="../mod/">Modules</a> | <a href="../mod/directives.html">Directives</a> | <a href="http://wiki.apache.org/httpd/FAQ">FAQ</a> | <a href="../glossary.html">Glossary</a> | <a href="../sitemap.html">Sitemap</a></p> 20 <p class="apache">Apache HTTP Server Version 2.2</p> 21 <img alt="" src="../images/feather.gif" /></div> 22 <div class="up"><a href="./"><img title="<-" alt="<-" src="../images/left.gif" /></a></div> 23 <div id="path"> 24 <a href="http://www.apache.org/">Apache</a> > <a href="http://httpd.apache.org/">HTTP Server</a> > <a href="http://httpd.apache.org/docs/">Documentation</a> > <a href="../">Version 2.2</a> > <a href="./">Miscellaneous Documentation</a></div><div id="page-content"><div class="retired"><h4>Please note</h4> 25 <p> This document refers to a legacy release (<strong>2.2</strong>) of Apache httpd. The active release (<strong>2.4</strong>) is documented <a href="http://httpd.apache.org/docs/current">here</a>. If you have not already upgraded, please follow <a href="http://httpd.apache.org/docs/current/upgrading.html">this link</a> for more information.</p> 26 <p>You may follow <a href="http://httpd.apache.org/docs/current/misc/security_tips.html">this link</a> to go to the current version of this document.</p></div><div id="preamble"><h1>Security Tips</h1> 27 <div class="toplang"> 28 <p><span>Available Languages: </span><a href="../en/misc/security_tips.html" title="English"> en </a> | 29 <a href="../ko/misc/security_tips.html" hreflang="ko" rel="alternate" title="Korean"> ko </a> | 30 <a href="../tr/misc/security_tips.html" hreflang="tr" rel="alternate" title="Türkçe"> tr </a></p> 31 </div> 32 33 <p>Some hints and tips on security issues in setting up a web server. 34 Some of the suggestions will be general, others specific to Apache.</p> 35 </div> 36 <div id="quickview"><ul id="toc"><li><img alt="" src="../images/down.gif" /> <a href="#uptodate">Keep up to Date</a></li> 37 <li><img alt="" src="../images/down.gif" /> <a href="#serverroot">Permissions on ServerRoot Directories</a></li> 38 <li><img alt="" src="../images/down.gif" /> <a href="#ssi">Server Side Includes</a></li> 39 <li><img alt="" src="../images/down.gif" /> <a href="#cgi">CGI in General</a></li> 40 <li><img alt="" src="../images/down.gif" /> <a href="#nsaliasedcgi">Non Script Aliased CGI</a></li> 41 <li><img alt="" src="../images/down.gif" /> <a href="#saliasedcgi">Script Aliased CGI</a></li> 42 <li><img alt="" src="../images/down.gif" /> <a href="#dynamic">Other sources of dynamic content</a></li> 43 <li><img alt="" src="../images/down.gif" /> <a href="#systemsettings">Protecting System Settings</a></li> 44 <li><img alt="" src="../images/down.gif" /> <a href="#protectserverfiles">Protect Server Files by Default</a></li> 45 <li><img alt="" src="../images/down.gif" /> <a href="#watchyourlogs">Watching Your Logs</a></li> 46 </ul><ul class="seealso"><li><a href="#comments_section">Comments</a></li></ul></div> 47 <div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div> 48 <div class="section"> 49 <h2><a name="uptodate" id="uptodate">Keep up to Date</a></h2> 50 51 <p>The Apache HTTP Server has a good record for security and a 52 developer community highly concerned about security issues. But 53 it is inevitable that some problems -- small or large -- will be 54 discovered in software after it is released. For this reason, it 55 is crucial to keep aware of updates to the software. If you have 56 obtained your version of the HTTP Server directly from Apache, we 57 highly recommend you subscribe to the <a href="http://httpd.apache.org/lists.html#http-announce">Apache 58 HTTP Server Announcements List</a> where you can keep informed of 59 new releases and security updates. Similar services are available 60 from most third-party distributors of Apache software.</p> 61 62 <p>Of course, most times that a web server is compromised, it is 63 not because of problems in the HTTP Server code. Rather, it comes 64 from problems in add-on code, CGI scripts, or the underlying 65 Operating System. You must therefore stay aware of problems and 66 updates with all the software on your system.</p> 67 68 </div><div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div> 69 <div class="section"> 70 <h2><a name="serverroot" id="serverroot">Permissions on ServerRoot Directories</a></h2> 71 72 73 74 <p>In typical operation, Apache is started by the root user, and it 75 switches to the user defined by the <code class="directive"><a href="../mod/mpm_common.html#user">User</a></code> directive to serve hits. As is the 76 case with any command that root executes, you must take care that it is 77 protected from modification by non-root users. Not only must the files 78 themselves be writeable only by root, but so must the directories, and 79 parents of all directories. For example, if you choose to place 80 ServerRoot in <code>/usr/local/apache</code> then it is suggested that 81 you create that directory as root, with commands like these:</p> 82 83 <div class="example"><p><code> 84 mkdir /usr/local/apache <br /> 85 cd /usr/local/apache <br /> 86 mkdir bin conf logs <br /> 87 chown 0 . bin conf logs <br /> 88 chgrp 0 . bin conf logs <br /> 89 chmod 755 . bin conf logs 90 </code></p></div> 91 92 <p>It is assumed that <code>/</code>, <code>/usr</code>, and 93 <code>/usr/local</code> are only modifiable by root. When you install the 94 <code class="program"><a href="../programs/httpd.html">httpd</a></code> executable, you should ensure that it is 95 similarly protected:</p> 96 97 <div class="example"><p><code> 98 cp httpd /usr/local/apache/bin <br /> 99 chown 0 /usr/local/apache/bin/httpd <br /> 100 chgrp 0 /usr/local/apache/bin/httpd <br /> 101 chmod 511 /usr/local/apache/bin/httpd 102 </code></p></div> 103 104 <p>You can create an htdocs subdirectory which is modifiable by other 105 users -- since root never executes any files out of there, and shouldn't 106 be creating files in there.</p> 107 108 <p>If you allow non-root users to modify any files that root either 109 executes or writes on then you open your system to root compromises. 110 For example, someone could replace the <code class="program"><a href="../programs/httpd.html">httpd</a></code> binary so 111 that the next time you start it, it will execute some arbitrary code. If 112 the logs directory is writeable (by a non-root user), someone could replace 113 a log file with a symlink to some other system file, and then root 114 might overwrite that file with arbitrary data. If the log files 115 themselves are writeable (by a non-root user), then someone may be 116 able to overwrite the log itself with bogus data.</p> 117 118 </div><div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div> 119 <div class="section"> 120 <h2><a name="ssi" id="ssi">Server Side Includes</a></h2> 121 122 123 124 <p>Server Side Includes (SSI) present a server administrator with 125 several potential security risks.</p> 126 127 <p>The first risk is the increased load on the server. All 128 SSI-enabled files have to be parsed by Apache, whether or not 129 there are any SSI directives included within the files. While this 130 load increase is minor, in a shared server environment it can become 131 significant.</p> 132 133 <p>SSI files also pose the same risks that are associated with CGI 134 scripts in general. Using the <code>exec cmd</code> element, SSI-enabled 135 files can execute any CGI script or program under the permissions of the 136 user and group Apache runs as, as configured in <code>httpd.conf</code>. 137 </p> 138 139 <p>There are ways to enhance the security of SSI files while still 140 taking advantage of the benefits they provide.</p> 141 142 <p>To isolate the damage a wayward SSI file can cause, a server 143 administrator can enable <a href="../suexec.html">suexec</a> as 144 described in the <a href="#cgi">CGI in General</a> section.</p> 145 146 <p>Enabling SSI for files with <code>.html</code> or <code>.htm</code> 147 extensions can be dangerous. This is especially true in a shared, or high 148 traffic, server environment. SSI-enabled files should have a separate 149 extension, such as the conventional <code>.shtml.</code> This helps keep 150 server load at a minimum and allows for easier management of risk.</p> 151 152 <p>Another solution is to disable the ability to run scripts and 153 programs from SSI pages. To do this replace <code>Includes</code> 154 with <code>IncludesNOEXEC</code> in the <code class="directive"><a href="../mod/core.html#options">Options</a></code> directive. Note that users may 155 still use <code><--#include virtual="..." --></code> to execute CGI 156 scripts if these scripts are in directories designated by a <code class="directive"><a href="../mod/mod_alias.html#scriptalias">ScriptAlias</a></code> directive.</p> 157 158 </div><div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div> 159 <div class="section"> 160 <h2><a name="cgi" id="cgi">CGI in General</a></h2> 161 162 163 164 <p>First of all, you always have to remember that you must trust the 165 writers of the CGI scripts/programs or your ability to spot potential 166 security holes in CGI, whether they were deliberate or accidental. CGI 167 scripts can run essentially arbitrary commands on your system with the 168 permissions of the web server user and can therefore be extremely 169 dangerous if they are not carefully checked.</p> 170 171 <p>All the CGI scripts will run as the same user, so they have potential 172 to conflict (accidentally or deliberately) with other scripts e.g. User 173 A hates User B, so he writes a script to trash User B's CGI database. One 174 program which can be used to allow scripts to run as different users is 175 <a href="../suexec.html">suEXEC</a> which is included with Apache as of 176 1.2 and is called from special hooks in the Apache server code. Another 177 popular way of doing this is with 178 <a href="http://cgiwrap.sourceforge.net/">CGIWrap</a>.</p> 179 180 </div><div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div> 181 <div class="section"> 182 <h2><a name="nsaliasedcgi" id="nsaliasedcgi">Non Script Aliased CGI</a></h2> 183 184 185 186 <p>Allowing users to execute CGI scripts in any directory should only be 187 considered if:</p> 188 189 <ul> 190 <li>You trust your users not to write scripts which will deliberately 191 or accidentally expose your system to an attack.</li> 192 <li>You consider security at your site to be so feeble in other areas, 193 as to make one more potential hole irrelevant.</li> 194 <li>You have no users, and nobody ever visits your server.</li> 195 </ul> 196 197 </div><div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div> 198 <div class="section"> 199 <h2><a name="saliasedcgi" id="saliasedcgi">Script Aliased CGI</a></h2> 200 201 202 203 <p>Limiting CGI to special directories gives the admin control over what 204 goes into those directories. This is inevitably more secure than non 205 script aliased CGI, but only if users with write access to the 206 directories are trusted or the admin is willing to test each 207 new CGI script/program for potential security holes.</p> 208 209 <p>Most sites choose this option over the non script aliased CGI 210 approach.</p> 211 212 </div><div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div> 213 <div class="section"> 214 <h2><a name="dynamic" id="dynamic">Other sources of dynamic content</a></h2> 215 216 217 218 <p> 219 Embedded scripting options which run as part of the server itself, 220 such as <code>mod_php</code>, <code>mod_perl</code>, <code>mod_tcl</code>, 221 and <code>mod_python</code>, run under the identity of the server itself 222 (see the <code class="directive"><a href="../mod/mpm_common.html#user">User</a></code> directive), and 223 therefore scripts executed by these engines potentially can access anything 224 the server user can. Some scripting engines may provide restrictions, but 225 it is better to be safe and assume not.</p> 226 227 </div><div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div> 228 <div class="section"> 229 <h2><a name="systemsettings" id="systemsettings">Protecting System Settings</a></h2> 230 231 232 233 <p>To run a really tight ship, you'll want to stop users from setting 234 up <code>.htaccess</code> files which can override security features 235 you've configured. Here's one way to do it.</p> 236 237 <p>In the server configuration file, put</p> 238 239 <div class="example"><p><code> 240 <Directory /> <br /> 241 AllowOverride None <br /> 242 </Directory> 243 </code></p></div> 244 245 <p>This prevents the use of <code>.htaccess</code> files in all 246 directories apart from those specifically enabled.</p> 247 248 </div><div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div> 249 <div class="section"> 250 <h2><a name="protectserverfiles" id="protectserverfiles">Protect Server Files by Default</a></h2> 251 252 253 254 <p>One aspect of Apache which is occasionally misunderstood is the 255 feature of default access. That is, unless you take steps to change it, 256 if the server can find its way to a file through normal URL mapping 257 rules, it can serve it to clients.</p> 258 259 <p>For instance, consider the following example:</p> 260 261 <div class="example"><p><code> 262 # cd /; ln -s / public_html <br /> 263 Accessing <code>http://localhost/~root/</code> 264 </code></p></div> 265 266 <p>This would allow clients to walk through the entire filesystem. To 267 work around this, add the following block to your server's 268 configuration:</p> 269 270 <div class="example"><p><code> 271 <Directory /> <br /> 272 Order Deny,Allow <br /> 273 Deny from all <br /> 274 </Directory> 275 </code></p></div> 276 277 <p>This will forbid default access to filesystem locations. Add 278 appropriate <code class="directive"><a href="../mod/core.html#directory">Directory</a></code> blocks to 279 allow access only in those areas you wish. For example,</p> 280 281 <div class="example"><p><code> 282 <Directory /usr/users/*/public_html> <br /> 283 Order Deny,Allow <br /> 284 Allow from all <br /> 285 </Directory> <br /> 286 <Directory /usr/local/httpd> <br /> 287 Order Deny,Allow <br /> 288 Allow from all <br /> 289 </Directory> 290 </code></p></div> 291 292 <p>Pay particular attention to the interactions of <code class="directive"><a href="../mod/core.html#location">Location</a></code> and <code class="directive"><a href="../mod/core.html#directory">Directory</a></code> directives; for instance, even 293 if <code><Directory /></code> denies access, a <code> 294 <Location /></code> directive might overturn it.</p> 295 296 <p>Also be wary of playing games with the <code class="directive"><a href="../mod/mod_userdir.html#userdir">UserDir</a></code> directive; setting it to 297 something like <code>./</code> would have the same effect, for root, as 298 the first example above. If you are using Apache 1.3 or above, we strongly 299 recommend that you include the following line in your server 300 configuration files:</p> 301 302 <div class="example"><p><code> 303 UserDir disabled root 304 </code></p></div> 305 306 </div><div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div> 307 <div class="section"> 308 <h2><a name="watchyourlogs" id="watchyourlogs">Watching Your Logs</a></h2> 309 310 311 312 <p>To keep up-to-date with what is actually going on against your server 313 you have to check the <a href="../logs.html">Log Files</a>. Even though 314 the log files only reports what has already happened, they will give you 315 some understanding of what attacks is thrown against the server and 316 allow you to check if the necessary level of security is present.</p> 317 318 <p>A couple of examples:</p> 319 320 <div class="example"><p><code> 321 grep -c "/jsp/source.jsp?/jsp/ /jsp/source.jsp??" access_log <br /> 322 grep "client denied" error_log | tail -n 10 323 </code></p></div> 324 325 <p>The first example will list the number of attacks trying to exploit the 326 <a href="http://online.securityfocus.com/bid/4876/info/">Apache Tomcat 327 Source.JSP Malformed Request Information Disclosure Vulnerability</a>, 328 the second example will list the ten last denied clients, for example:</p> 329 330 <div class="example"><p><code> 331 [Thu Jul 11 17:18:39 2002] [error] [client foo.example.com] client denied 332 by server configuration: /usr/local/apache/htdocs/.htpasswd 333 </code></p></div> 334 335 <p>As you can see, the log files only report what already has happened, so 336 if the client had been able to access the <code>.htpasswd</code> file you 337 would have seen something similar to:</p> 338 339 <div class="example"><p><code> 340 foo.example.com - - [12/Jul/2002:01:59:13 +0200] "GET /.htpasswd HTTP/1.1" 341 </code></p></div> 342 343 <p>in your <a href="../logs.html#accesslog">Access Log</a>. This means 344 you probably commented out the following in your server configuration 345 file:</p> 346 347 <div class="example"><p><code> 348 <Files ~ "^\.ht"> <br /> 349 Order allow,deny <br /> 350 Deny from all <br /> 351 </Files> 352 </code></p></div> 353 354 </div></div> 355 <div class="bottomlang"> 356 <p><span>Available Languages: </span><a href="../en/misc/security_tips.html" title="English"> en </a> | 357 <a href="../ko/misc/security_tips.html" hreflang="ko" rel="alternate" title="Korean"> ko </a> | 358 <a href="../tr/misc/security_tips.html" hreflang="tr" rel="alternate" title="Türkçe"> tr </a></p> 359 </div><div class="top"><a href="#page-header"><img src="../images/up.gif" alt="top" /></a></div><div class="section"><h2><a id="comments_section" name="comments_section">Comments</a></h2><div class="warning"><strong>Notice:</strong><br />This is not a Q&A section. Comments placed here should be pointed towards suggestions on improving the documentation or server, and may be removed again by our moderators if they are either implemented or considered invalid/off-topic. Questions on how to manage the Apache HTTP Server should be directed at either our IRC channel, #httpd, on Freenode, or sent to our <a href="http://httpd.apache.org/lists.html">mailing lists</a>.</div> 360 <script type="text/javascript"><!--//--><![CDATA[//><!-- 361 var comments_shortname = 'httpd'; 362 var comments_identifier = 'http://httpd.apache.org/docs/2.2/misc/security_tips.html'; 363 (function(w, d) { 364 if (w.location.hostname.toLowerCase() == "httpd.apache.org") { 365 d.write('<div id="comments_thread"><\/div>'); 366 var s = d.createElement('script'); 367 s.type = 'text/javascript'; 368 s.async = true; 369 s.src = 'https://comments.apache.org/show_comments.lua?site=' + comments_shortname + '&page=' + comments_identifier; 370 (d.getElementsByTagName('head')[0] || d.getElementsByTagName('body')[0]).appendChild(s); 371 } 372 else { 373 d.write('<div id="comments_thread">Comments are disabled for this page at the moment.<\/div>'); 374 } 375 })(window, document); 376 //--><!]]></script></div><div id="footer"> 377 <p class="apache">Copyright 2017 The Apache Software Foundation.<br />Licensed under the <a href="http://www.apache.org/licenses/LICENSE-2.0">Apache License, Version 2.0</a>.</p> 378 <p class="menu"><a href="../mod/">Modules</a> | <a href="../mod/directives.html">Directives</a> | <a href="http://wiki.apache.org/httpd/FAQ">FAQ</a> | <a href="../glossary.html">Glossary</a> | <a href="../sitemap.html">Sitemap</a></p></div><script type="text/javascript"><!--//--><![CDATA[//><!-- 379 if (typeof(prettyPrint) !== 'undefined') { 380 prettyPrint(); 381 } 382 //--><!]]></script> 383 </body></html>