320 lines
22 KiB
HTML
320 lines
22 KiB
HTML
|
<!DOCTYPE HTML>
|
||
|
|
<html lang="en" class="sidebar-visible no-js light">
|
||
|
|
<head>
|
||
|
|
<!-- Book generated using mdBook -->
|
||
|
|
<meta charset="UTF-8">
|
||
|
|
<title>URL Previews - Synapse</title>
|
||
|
|
|
||
|
|
|
||
|
|
|
||
|
|
|
||
|
|
<!-- Custom HTML head -->
|
||
|
|
|
||
|
|
|
||
|
|
|
||
|
|
<meta content="text/html; charset=utf-8" http-equiv="Content-Type">
|
||
|
|
<meta name="description" content="">
|
||
|
|
<meta name="viewport" content="width=device-width, initial-scale=1">
|
||
|
|
<meta name="theme-color" content="#ffffff" />
|
||
|
|
|
||
|
|
|
||
|
|
<link rel="icon" href="../favicon.svg">
|
||
|
|
|
||
|
|
|
||
|
|
<link rel="shortcut icon" href="../favicon.png">
|
||
|
|
|
||
|
|
<link rel="stylesheet" href="../css/variables.css">
|
||
|
|
<link rel="stylesheet" href="../css/general.css">
|
||
|
|
<link rel="stylesheet" href="../css/chrome.css">
|
||
|
|
|
||
|
|
<link rel="stylesheet" href="../css/print.css" media="print">
|
||
|
|
|
||
|
|
|
||
|
|
<!-- Fonts -->
|
||
|
|
<link rel="stylesheet" href="../FontAwesome/css/font-awesome.css">
|
||
|
|
|
||
|
|
<link rel="stylesheet" href="../fonts/fonts.css">
|
||
|
|
|
||
|
|
|
||
|
|
<!-- Highlight.js Stylesheets -->
|
||
|
|
<link rel="stylesheet" href="../highlight.css">
|
||
|
|
<link rel="stylesheet" href="../tomorrow-night.css">
|
||
|
|
<link rel="stylesheet" href="../ayu-highlight.css">
|
||
|
|
|
||
|
|
<!-- Custom theme stylesheets -->
|
||
|
|
|
||
|
|
<link rel="stylesheet" href="../docs/website_files/table-of-contents.css">
|
||
|
|
|
||
|
|
<link rel="stylesheet" href="../docs/website_files/remove-nav-buttons.css">
|
||
|
|
|
||
|
|
<link rel="stylesheet" href="../docs/website_files/indent-section-headers.css">
|
||
|
|
|
||
|
|
|
||
|
|
|
||
|
|
</head>
|
||
|
|
<body>
|
||
|
|
<!-- Provide site root to javascript -->
|
||
|
|
<script type="text/javascript">
|
||
|
|
var path_to_root = "../";
|
||
|
|
var default_theme = window.matchMedia("(prefers-color-scheme: dark)").matches ? "navy" : "light";
|
||
|
|
</script>
|
||
|
|
|
||
|
|
<!-- Work around some values being stored in localStorage wrapped in quotes -->
|
||
|
|
<script type="text/javascript">
|
||
|
|
try {
|
||
|
|
var theme = localStorage.getItem('mdbook-theme');
|
||
|
|
var sidebar = localStorage.getItem('mdbook-sidebar');
|
||
|
|
if (theme.startsWith('"') && theme.endsWith('"')) {
|
||
|
|
localStorage.setItem('mdbook-theme', theme.slice(1, theme.length - 1));
|
||
|
|
}
|
||
|
|
if (sidebar.startsWith('"') && sidebar.endsWith('"')) {
|
||
|
|
localStorage.setItem('mdbook-sidebar', sidebar.slice(1, sidebar.length - 1));
|
||
|
|
}
|
||
|
|
} catch (e) { }
|
||
|
|
</script>
|
||
|
|
|
||
|
|
<!-- Set the theme before any content is loaded, prevents flash -->
|
||
|
|
<script type="text/javascript">
|
||
|
|
var theme;
|
||
|
|
try { theme = localStorage.getItem('mdbook-theme'); } catch(e) { }
|
||
|
|
if (theme === null || theme === undefined) { theme = default_theme; }
|
||
|
|
var html = document.querySelector('html');
|
||
|
|
html.classList.remove('no-js')
|
||
|
|
html.classList.remove('light')
|
||
|
|
html.classList.add(theme);
|
||
|
|
html.classList.add('js');
|
||
|
|
</script>
|
||
|
|
|
||
|
|
<!-- Hide / unhide sidebar before it is displayed -->
|
||
|
|
<script type="text/javascript">
|
||
|
|
var html = document.querySelector('html');
|
||
|
|
var sidebar = 'hidden';
|
||
|
|
if (document.body.clientWidth >= 1080) {
|
||
|
|
try { sidebar = localStorage.getItem('mdbook-sidebar'); } catch(e) { }
|
||
|
|
sidebar = sidebar || 'visible';
|
||
|
|
}
|
||
|
|
html.classList.remove('sidebar-visible');
|
||
|
|
html.classList.add("sidebar-" + sidebar);
|
||
|
|
</script>
|
||
|
|
|
||
|
|
<nav id="sidebar" class="sidebar" aria-label="Table of contents">
|
||
|
|
<div class="sidebar-scrollbox">
|
||
|
|
<ol class="chapter"><li class="chapter-item expanded affix "><li class="part-title">Introduction</li><li class="chapter-item expanded "><a href="../welcome_and_overview.html">Welcome and Overview</a></li><li class="chapter-item expanded affix "><li class="part-title">Setup</li><li class="chapter-item expanded "><a href="../setup/installation.html">Installation</a></li><li class="chapter-item expanded "><a href="../postgres.html">Using Postgres</a></li><li class="chapter-item expanded "><a href="../reverse_proxy.html">Configuring a Reverse Proxy</a></li><li class="chapter-item expanded "><a href="../setup/forward_proxy.html">Configuring a Forward/Outbound Proxy</a></li><li class="chapter-item expanded "><a href="../turn-howto.html">Configuring a Turn Server</a></li><li class="chapter-item expanded "><a href="../delegate.html">Delegation</a></li><li class="chapter-item expanded affix "><li class="part-title">Upgrading</li><li class="chapter-item expanded "><a href="../upgrade.html">Upgrading between Synapse Versions</a></li><li class="chapter-item expanded "><a href="../MSC1711_certificates_FAQ.html">Upgrading from pre-Synapse 1.0</a></li><li class="chapter-item expanded affix "><li class="part-title">Usage</li><li class="chapter-item expanded "><a href="../federate.html">Federation</a></li><li class="chapter-item expanded "><a href="../usage/configuration/index.html">Configuration</a></li><li><ol class="section"><li class="chapter-item expanded "><a href="../usage/configuration/homeserver_sample_config.html">Homeserver Sample Config File</a></li><li class="chapter-item expanded "><a href="../usage/configuration/logging_sample_config.html">Logging Sample Config File</a></li><li class="chapter-item expanded "><a href="../structured_logging.html">Structured Logging</a></li><li class="chapter-item expanded "><a href="../templates.html">Templates</a></li><li class="chapter-item expanded "><a href="../usage/configuration/user_authentication/index.html">User Authentication</a></li><li><ol class="section"><li class="chapter-item expanded "><div>Single-Sign On</div></li><li><ol class="section"><li class="chapter-item expanded "><a href="../openid.html">OpenID Connect</a></li><li class="chapter-item expanded "><div>SAML</div></li><li class="chapter-item expanded "><div>CAS</div></li><li class="chapter-item expanded "><a href="../sso_mapping_providers.html">SSO Mapping Providers</a></li></ol></li><li class="chapter-item expanded "><a href="../password_auth_providers.html">Password Auth Providers</a></li><li class="chapter-item expanded "><a href="../jwt.html">JSON Web Tokens</a></li></ol></li><li class="chapter-item expanded "><a href="../CAPTCHA_SETUP.html">Registration Captcha</a></li><li class="chapter-item expanded "><a href="../application_services.html">Application Services</a></li><li class="chapter-item expanded "><a href="../server_notices.html">Server Notices</a></li><li class="chapter-item expanded "><a href="../consent_tracking.html">Consent Tracking</a></li><li class="chapter-item expanded "><a href="../development/url_previews.html" class="active">URL Previews</a></li><li class="chapter-item expanded "><a href="../user_directory.html">User Directory</a></li><li class="chapter-item expanded "><a href="../message_retention_policies.html">Message Retention Policies</a></li><li class="chapter-item expanded "><a href="../modules/index.html">Pluggable Modules</a></li><li><ol class="section"><li class="chapter-item expanded "><a href="../modules/writing_a_module.html">Writing a module</a></li><li><ol class="section"><li class="chapter-item expanded "><a href="../modules/spam_checker_callbacks.html">Spam checker callbacks</a></li><li class="chapter-item expanded "><a href="../modules/third_party_rules_callbacks.html">Third-party rules callbacks</a></li><li class="chapter-item expanded "><a href="../modules/presence_router_callbacks.html">Presence router callbacks</a></li><li class="chapter-item expanded "><a href="../modules/account_validity_callbacks.html">Account validity callbacks</a></li><li class="chapter
|
||
|
|
</div>
|
||
|
|
<div id="sidebar-resize-handle" class="sidebar-resize-handle"></div>
|
||
|
|
</nav>
|
||
|
|
|
||
|
|
<div id="page-wrapper" class="page-wrapper">
|
||
|
|
|
||
|
|
<div class="page">
|
||
|
|
|
||
|
|
<div id="menu-bar-hover-placeholder"></div>
|
||
|
|
<div id="menu-bar" class="menu-bar sticky bordered">
|
||
|
|
<div class="left-buttons">
|
||
|
|
<button id="sidebar-toggle" class="icon-button" type="button" title="Toggle Table of Contents" aria-label="Toggle Table of Contents" aria-controls="sidebar">
|
||
|
|
<i class="fa fa-bars"></i>
|
||
|
|
</button>
|
||
|
|
<button id="theme-toggle" class="icon-button" type="button" title="Change theme" aria-label="Change theme" aria-haspopup="true" aria-expanded="false" aria-controls="theme-list">
|
||
|
|
<i class="fa fa-paint-brush"></i>
|
||
|
|
</button>
|
||
|
|
<ul id="theme-list" class="theme-popup" aria-label="Themes" role="menu">
|
||
|
|
<li role="none"><button role="menuitem" class="theme" id="light">Light (default)</button></li>
|
||
|
|
<li role="none"><button role="menuitem" class="theme" id="rust">Rust</button></li>
|
||
|
|
<li role="none"><button role="menuitem" class="theme" id="coal">Coal</button></li>
|
||
|
|
<li role="none"><button role="menuitem" class="theme" id="navy">Navy</button></li>
|
||
|
|
<li role="none"><button role="menuitem" class="theme" id="ayu">Ayu</button></li>
|
||
|
|
</ul>
|
||
|
|
|
||
|
|
<button id="search-toggle" class="icon-button" type="button" title="Search. (Shortkey: s)" aria-label="Toggle Searchbar" aria-expanded="false" aria-keyshortcuts="S" aria-controls="searchbar">
|
||
|
|
<i class="fa fa-search"></i>
|
||
|
|
</button>
|
||
|
|
|
||
|
|
</div>
|
||
|
|
|
||
|
|
<h1 class="menu-title">Synapse</h1>
|
||
|
|
|
||
|
|
<div class="right-buttons">
|
||
|
|
|
||
|
|
<a href="../print.html" title="Print this book" aria-label="Print this book">
|
||
|
|
<i id="print-button" class="fa fa-print"></i>
|
||
|
|
</a>
|
||
|
|
|
||
|
|
|
||
|
|
<a href="https://github.com/matrix-org/synapse" title="Git repository" aria-label="Git repository">
|
||
|
|
<i id="git-repository-button" class="fa fa-github"></i>
|
||
|
|
</a>
|
||
|
|
|
||
|
|
|
||
|
|
<a href="https://github.com/matrix-org/synapse/edit/develop/docs/development/url_previews.md" title="Suggest an edit" aria-label="Suggest an edit">
|
||
|
|
<i id="git-edit-button" class="fa fa-edit"></i>
|
||
|
|
</a>
|
||
|
|
|
||
|
|
|
||
|
|
</div>
|
||
|
|
</div>
|
||
|
|
|
||
|
|
|
||
|
|
<div id="search-wrapper" class="hidden">
|
||
|
|
<form id="searchbar-outer" class="searchbar-outer">
|
||
|
|
<input type="search" id="searchbar" name="searchbar" placeholder="Search this book ..." aria-controls="searchresults-outer" aria-describedby="searchresults-header">
|
||
|
|
</form>
|
||
|
|
<div id="searchresults-outer" class="searchresults-outer hidden">
|
||
|
|
<div id="searchresults-header" class="searchresults-header"></div>
|
||
|
|
<ul id="searchresults">
|
||
|
|
</ul>
|
||
|
|
</div>
|
||
|
|
</div>
|
||
|
|
|
||
|
|
|
||
|
|
<!-- Apply ARIA attributes after the sidebar and the sidebar toggle button are added to the DOM -->
|
||
|
|
<script type="text/javascript">
|
||
|
|
document.getElementById('sidebar-toggle').setAttribute('aria-expanded', sidebar === 'visible');
|
||
|
|
document.getElementById('sidebar').setAttribute('aria-hidden', sidebar !== 'visible');
|
||
|
|
Array.from(document.querySelectorAll('#sidebar a')).forEach(function(link) {
|
||
|
|
link.setAttribute('tabIndex', sidebar === 'visible' ? 0 : -1);
|
||
|
|
});
|
||
|
|
</script>
|
||
|
|
|
||
|
|
<div id="content" class="content">
|
||
|
|
<main>
|
||
|
|
<!-- Page table of contents -->
|
||
|
|
<div class="sidetoc">
|
||
|
|
<nav class="pagetoc"></nav>
|
||
|
|
</div>
|
||
|
|
|
||
|
|
<h1 id="url-previews"><a class="header" href="#url-previews">URL Previews</a></h1>
|
||
|
|
<p>The <code>GET /_matrix/media/r0/preview_url</code> endpoint provides a generic preview API
|
||
|
|
for URLs which outputs <a href="https://ogp.me/">Open Graph</a> responses (with some Matrix
|
||
|
|
specific additions).</p>
|
||
|
|
<p>This does have trade-offs compared to other designs:</p>
|
||
|
|
<ul>
|
||
|
|
<li>Pros:
|
||
|
|
<ul>
|
||
|
|
<li>Simple and flexible; can be used by any clients at any point</li>
|
||
|
|
</ul>
|
||
|
|
</li>
|
||
|
|
<li>Cons:
|
||
|
|
<ul>
|
||
|
|
<li>If each homeserver provides one of these independently, all the HSes in a
|
||
|
|
room may needlessly DoS the target URI</li>
|
||
|
|
<li>The URL metadata must be stored somewhere, rather than just using Matrix
|
||
|
|
itself to store the media.</li>
|
||
|
|
<li>Matrix cannot be used to distribute the metadata between homeservers.</li>
|
||
|
|
</ul>
|
||
|
|
</li>
|
||
|
|
</ul>
|
||
|
|
<p>When Synapse is asked to preview a URL it does the following:</p>
|
||
|
|
<ol>
|
||
|
|
<li>Checks against a URL blacklist (defined as <code>url_preview_url_blacklist</code> in the
|
||
|
|
config).</li>
|
||
|
|
<li>Checks the in-memory cache by URLs and returns the result if it exists. (This
|
||
|
|
is also used to de-duplicate processing of multiple in-flight requests at once.)</li>
|
||
|
|
<li>Kicks off a background process to generate a preview:
|
||
|
|
<ol>
|
||
|
|
<li>Checks the database cache by URL and timestamp and returns the result if it
|
||
|
|
has not expired and was successful (a 2xx return code).</li>
|
||
|
|
<li>Checks if the URL matches an oEmbed pattern. If it does, fetch the oEmbed
|
||
|
|
response. If this is an image, replace the URL to fetch and continue. If
|
||
|
|
if it is HTML content, use the HTML as the document and continue.</li>
|
||
|
|
<li>If it doesn't match an oEmbed pattern, downloads the URL and stores it
|
||
|
|
into a file via the media storage provider and saves the local media
|
||
|
|
metadata.</li>
|
||
|
|
<li>If the media is an image:
|
||
|
|
<ol>
|
||
|
|
<li>Generates thumbnails.</li>
|
||
|
|
<li>Generates an Open Graph response based on image properties.</li>
|
||
|
|
</ol>
|
||
|
|
</li>
|
||
|
|
<li>If the media is HTML:
|
||
|
|
<ol>
|
||
|
|
<li>Decodes the HTML via the stored file.</li>
|
||
|
|
<li>Generates an Open Graph response from the HTML.</li>
|
||
|
|
<li>If an image exists in the Open Graph response:
|
||
|
|
<ol>
|
||
|
|
<li>Downloads the URL and stores it into a file via the media storage
|
||
|
|
provider and saves the local media metadata.</li>
|
||
|
|
<li>Generates thumbnails.</li>
|
||
|
|
<li>Updates the Open Graph response based on image properties.</li>
|
||
|
|
</ol>
|
||
|
|
</li>
|
||
|
|
</ol>
|
||
|
|
</li>
|
||
|
|
<li>Stores the result in the database cache.</li>
|
||
|
|
</ol>
|
||
|
|
</li>
|
||
|
|
<li>Returns the result.</li>
|
||
|
|
</ol>
|
||
|
|
<p>The in-memory cache expires after 1 hour.</p>
|
||
|
|
<p>Expired entries in the database cache (and their associated media files) are
|
||
|
|
deleted every 10 seconds. The default expiration time is 1 hour from download.</p>
|
||
|
|
|
||
|
|
</main>
|
||
|
|
|
||
|
|
<nav class="nav-wrapper" aria-label="Page navigation">
|
||
|
|
<!-- Mobile navigation buttons -->
|
||
|
|
|
||
|
|
<a rel="prev" href="../consent_tracking.html" class="mobile-nav-chapters previous" title="Previous chapter" aria-label="Previous chapter" aria-keyshortcuts="Left">
|
||
|
|
<i class="fa fa-angle-left"></i>
|
||
|
|
</a>
|
||
|
|
|
||
|
|
|
||
|
|
|
||
|
|
<a rel="next" href="../user_directory.html" class="mobile-nav-chapters next" title="Next chapter" aria-label="Next chapter" aria-keyshortcuts="Right">
|
||
|
|
<i class="fa fa-angle-right"></i>
|
||
|
|
</a>
|
||
|
|
|
||
|
|
|
||
|
|
<div style="clear: both"></div>
|
||
|
|
</nav>
|
||
|
|
</div>
|
||
|
|
</div>
|
||
|
|
|
||
|
|
<nav class="nav-wide-wrapper" aria-label="Page navigation">
|
||
|
|
|
||
|
|
<a rel="prev" href="../consent_tracking.html" class="nav-chapters previous" title="Previous chapter" aria-label="Previous chapter" aria-keyshortcuts="Left">
|
||
|
|
<i class="fa fa-angle-left"></i>
|
||
|
|
</a>
|
||
|
|
|
||
|
|
|
||
|
|
|
||
|
|
<a rel="next" href="../user_directory.html" class="nav-chapters next" title="Next chapter" aria-label="Next chapter" aria-keyshortcuts="Right">
|
||
|
|
<i class="fa fa-angle-right"></i>
|
||
|
|
</a>
|
||
|
|
|
||
|
|
</nav>
|
||
|
|
|
||
|
|
</div>
|
||
|
|
|
||
|
|
|
||
|
|
|
||
|
|
|
||
|
|
|
||
|
|
|
||
|
|
|
||
|
|
|
||
|
|
<script type="text/javascript">
|
||
|
|
window.playground_copyable = true;
|
||
|
|
</script>
|
||
|
|
|
||
|
|
|
||
|
|
|
||
|
|
|
||
|
|
|
||
|
|
<script src="../elasticlunr.min.js" type="text/javascript" charset="utf-8"></script>
|
||
|
|
<script src="../mark.min.js" type="text/javascript" charset="utf-8"></script>
|
||
|
|
<script src="../searcher.js" type="text/javascript" charset="utf-8"></script>
|
||
|
|
|
||
|
|
|
||
|
|
<script src="../clipboard.min.js" type="text/javascript" charset="utf-8"></script>
|
||
|
|
<script src="../highlight.js" type="text/javascript" charset="utf-8"></script>
|
||
|
|
<script src="../book.js" type="text/javascript" charset="utf-8"></script>
|
||
|
|
|
||
|
|
<!-- Custom JS scripts -->
|
||
|
|
|
||
|
|
<script type="text/javascript" src="../docs/website_files/table-of-contents.js"></script>
|
||
|
|
|
||
|
|
|
||
|
|
|
||
|
|
|
||
|
|
</body>
|
||
|
|
</html>
|