1 2 3 4 5 <!DOCTYPE html> 6 <html lang="en"> 7 <head> 8 <title>ImageMagick: Security Policy</title> 9 <meta charset="utf-8" /> 10 <meta http-equiv="X-UA-Compatible" content="IE=edge" /> 11 <meta name="viewport" content="width=device-width, initial-scale=1" /> 12 <meta http-equiv="content-type" content="text/html; charset=utf-8"/> 13 <meta name="application-name" content="ImageMagick"/> 14 <meta name="description" content="ImageMagick is a software suite to create, edit, compose, or convert bitmap images. It can read and write images in a variety of formats (over 200) including PNG, JPEG, JPEG-2000, GIF, WebP, Postscript, PDF, and SVG. 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It is useful for limiting the resources consumed by ImageMagick and can help prevent a denial-of-service or other exploits.</p> 60 61 <p>As an example, suppose you download an image from the internet and unbeknownst to you its been crafted to generate a 20000 by 20000 pixel image. ImageMagick attempts to allocate enough resources (memory, disk) and your system will likely deny the resource request and exit. However, its also possible that your computer might be temporarily sluggish or unavailable or ImageMagick may abort. To prevent such a scenario, you can set limits in the <code>policy.xml</code> configuration file. You may ask why ImageMagick does not already include reasonable limits? Simply because what is reasonable in your environment, might not be reasonable to someone else. We, for example, have access to a host with 1TB of memory whereas you may be running ImageMagick on an iPhone. If you utilize ImageMagick from a public website, you may want to increase security by preventing usage of the MVG or HTTPS coders. Only you can decide what are reasonable limits taking in consideration your environment. We provide this policy with reasonable limits and encourage you to use as a template for your own policy:</p> 62 63 <pre class="pre-scrollable"> 64 <policymap> 65 <policy domain="resource" name="temporary-path" value="/tmp"/> 66 <policy domain="resource" name="memory" value="256MiB"/> 67 <policy domain="resource" name="map" value="512MiB"/> 68 <policy domain="resource" name="width" value="8KP"/> 69 <policy domain="resource" name="height" value="8KP"/> 70 <policy domain="resource" name="area" value="128MB"/> 71 <policy domain="resource" name="disk" value="1GiB"/> 72 <policy domain="resource" name="file" value="768"/> 73 <policy domain="resource" name="thread" value="2"/> 74 <policy domain="resource" name="throttle" value="0"/> 75 <policy domain="resource" name="time" value="120"/> 76 <policy domain="system" name="precision" value="6"/> 77 <policy domain="cache" name="shared-secret" stealth="true" value="replace with your secret phrase"/> 78 <policy domain="coder" rights="none" pattern="MVG" /> 79 <policy domain="delegate" rights="none" pattern="HTTPS" /> <!-- prevent 'curl' program from reading HTTPS URL's --> 80 <policy domain="path" rights="none" pattern="@*"/> <!-- indirect reads not permitted --> 81 </policymap> 82 </pre> 83 84 <p>Since we process multiple simultaneous sessions, we do not want any one session consuming all the available memory.With this policy, large images are cached to disk. If the image is too large and exceeds the pixel cache disk limit, the program exits. In addition, we place a time limit to prevent any run-away processing tasks. If any one image has a width or height that exceeds 8192 pixels, an exception is thrown and processing stops. As of ImageMagick 7.0.1-8 and 6.9.4-6, you can prevent the use of any delegate or all delegates (set the pattern to "*"). Note, prior to these releases, use a domain of <code>coder</code> to prevent delegate usage (e.g. <code>domain="coder" rights="none" pattern="HTTPS"</code>). The policy also prevents indirect reads. If you want to, for example, read text from a file (e.g. <code>caption:@myCaption.txt</code>), you'll need to remove this policy.</p> 85 86 <p>Here is what you can expect when you restrict the HTTPS coder, for example:</p> 87 88 <pre> 89 $ convert https://www.imagemagick.org/images/wizard.png wizard.jpg 90 convert: not authorized `HTTPS' 91 convert: unable to open file: No such file or directory 92 convert: no images defined `wizard.jpg' 93 </pre> 94 95 <p>You can verify your policy changes are in effect with this command:</p> 96 97 <pre class="pre-scrollable"> 98 -> identify -list policy 99 Path: ImageMagick/policy.xml 100 Policy: Resource 101 name: time 102 value: 120 103 Policy: Resource 104 name: throttle 105 value: 0 106 Policy: Resource 107 name: thread 108 value: 2 109 Policy: Resource 110 name: file 111 value: 768 112 Policy: Resource 113 name: disk 114 value: 1GiB 115 Policy: Resource 116 name: map 117 value: 512MiB 118 Policy: Resource 119 name: memory 120 value: 256MiB 121 Policy: Resource 122 name: area 123 value: 128MB 124 Policy: Resource 125 name: height 126 value: 8KP 127 Policy: Resource 128 name: width 129 value: 8KP 130 Policy: Resource 131 name: temporary-path 132 value: /tmp 133 Policy: System 134 name: precision 135 value: 6 136 Policy: Cache 137 name: shared-secret 138 value: My voice is my passport. Verify me. 139 Policy: Path 140 rights: None 141 pattern: @* 142 143 Path: [built-in] 144 Policy: Undefined 145 rights: None 146 </pre> 147 148 <p>For additional details about resource limits and the policy configuration file, read <a href="resources.html">Resources</a> and <a href="architecture.html">Architecture</a>.</p> 149 </div> 150 <footer class="magick-footer"> 151 <p><a href="support.html">Donate</a> 152 <a href="sitemap.html">Sitemap</a> 153 <a href="links.html">Related</a> 154 <a href="security-policy.html">Security</a> 155 <a href="architecture.html">Architecture</a> 156 </p> 157 <p><a href="security-policy.html#">Back to top</a> 158 <a href="http://pgp.mit.edu:11371/pks/lookup?op=get&search=0x89AB63D48277377A">Public Key</a> 159 <a href="http://www.imagemagick.org/script/contact.php">Contact Us</a></p> 160 <p><small> 1999-2016 ImageMagick Studio LLC</small></p> 161 </footer> 162 </div><!-- /.container --> 163 164 <script src="https://localhost/ajax/libs/jquery/1.11.3/jquery.min.js"></script> 165 <script src="../js/magick.html"></script> 166 </div> 167 </body> 168 </html> 169
