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| author | clokep <clokep@users.noreply.github.com> | 2021-09-21 16:33:10 +0000 |
|---|---|---|
| committer | clokep <clokep@users.noreply.github.com> | 2021-09-21 16:33:10 +0000 |
| commit | c0fd778fd47bde855bd9aa9f185afec2c3bc247e (patch) | |
| tree | 7ddf9596f5f3365d4ddec53f2313c322da4b6f2a /develop/url_previews.html | |
| parent | deploy: ba7a91aea5fd624bf048f0fda0dca80da7a1945e (diff) | |
| download | synapse-c0fd778fd47bde855bd9aa9f185afec2c3bc247e.tar.xz | |
deploy: ebd8baf61ff8e00f8de3b63c00531765672000c8
Diffstat (limited to '')
| -rw-r--r-- | develop/url_previews.html | 365 |
1 files changed, 0 insertions, 365 deletions
diff --git a/develop/url_previews.html b/develop/url_previews.html deleted file mode 100644 index 0d6d5ab232..0000000000 --- a/develop/url_previews.html +++ /dev/null @@ -1,365 +0,0 @@ -<!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 ? 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(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/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>Design notes on a URL previewing service for Matrix:</p> -<p>Options are:</p> -<ol> -<li>Have an AS which listens for URLs, downloads them, and inserts an event that describes their metadata.</li> -</ol> -<ul> -<li>Pros: -<ul> -<li>Decouples the implementation entirely from Synapse.</li> -<li>Uses existing Matrix events & content repo to store the metadata.</li> -</ul> -</li> -<li>Cons: -<ul> -<li>Which AS should provide this service for a room, and why should you trust it?</li> -<li>Doesn't work well with E2E; you'd have to cut the AS into every room</li> -<li>the AS would end up subscribing to every room anyway.</li> -</ul> -</li> -</ul> -<ol start="2"> -<li>Have a generic preview API (nothing to do with Matrix) that provides a previewing service:</li> -</ol> -<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 HS provides one of these independently, all the HSes in a room may needlessly DoS the target URI</li> -<li>We need somewhere to store the URL metadata rather than just using Matrix itself</li> -<li>We can't piggyback on matrix to distribute the metadata between HSes.</li> -</ul> -</li> -</ul> -<ol start="3"> -<li>Make the synapse of the sending user responsible for spidering the URL and inserting an event asynchronously which describes the metadata.</li> -</ol> -<ul> -<li>Pros: -<ul> -<li>Works transparently for all clients</li> -<li>Piggy-backs nicely on using Matrix for distributing the metadata.</li> -<li>No confusion as to which AS</li> -</ul> -</li> -<li>Cons: -<ul> -<li>Doesn't work with E2E</li> -<li>We might want to decouple the implementation of the spider from the HS, given spider behaviour can be quite complicated and evolve much more rapidly than the HS. It's more like a bot than a core part of the server.</li> -</ul> -</li> -</ul> -<ol start="4"> -<li>Make the sending client use the preview API and insert the event itself when successful.</li> -</ol> -<ul> -<li>Pros: -<ul> -<li>Works well with E2E</li> -<li>No custom server functionality</li> -<li>Lets the client customise the preview that they send (like on FB)</li> -</ul> -</li> -<li>Cons: -<ul> -<li>Entirely specific to the sending client, whereas it'd be nice if /any/ URL was correctly previewed if clients support it.</li> -</ul> -</li> -</ul> -<ol start="5"> -<li>Have the option of specifying a shared (centralised) previewing service used by a room, to avoid all the different HSes in the room DoSing the target.</li> -</ol> -<p>Best solution is probably a combination of both 2 and 4.</p> -<ul> -<li>Sending clients do their best to create and send a preview at the point of sending the message, perhaps delaying the message until the preview is computed? (This also lets the user validate the preview before sending)</li> -<li>Receiving clients have the option of going and creating their own preview if one doesn't arrive soon enough (or if the original sender didn't create one)</li> -</ul> -<p>This is a bit magical though in that the preview could come from two entirely different sources - the sending HS or your local one. However, this can always be exposed to users: "Generate your own URL previews if none are available?"</p> -<p>This is tantamount also to senders calculating their own thumbnails for sending in advance of the main content - we are trusting the sender not to lie about the content in the thumbnail. Whereas currently thumbnails are calculated by the receiving homeserver to avoid this attack.</p> -<p>However, this kind of phishing attack does exist whether we let senders pick their thumbnails or not, in that a malicious sender can send normal text messages around the attachment claiming it to be legitimate. We could rely on (future) reputation/abuse management to punish users who phish (be it with bogus metadata or bogus descriptions). Bogus metadata is particularly bad though, especially if it's avoidable.</p> -<p>As a first cut, let's do #2 and have the receiver hit the API to calculate its own previews (as it does currently for image thumbnails). We can then extend/optimise this to option 4 as a special extra if needed.</p> -<h2 id="api"><a class="header" href="#api">API</a></h2> -<pre><code>GET /_matrix/media/r0/preview_url?url=http://wherever.com -200 OK -{ - "og:type" : "article" - "og:url" : "https://twitter.com/matrixdotorg/status/684074366691356672" - "og:title" : "Matrix on Twitter" - "og:image" : "https://pbs.twimg.com/profile_images/500400952029888512/yI0qtFi7_400x400.png" - "og:description" : "“Synapse 0.12 is out! Lots of polishing, performance &amp;amp; bugfixes: /sync API, /r0 prefix, fulltext search, 3PID invites https://t.co/5alhXLLEGP”" - "og:site_name" : "Twitter" -} -</code></pre> -<ul> -<li>Downloads the URL -<ul> -<li>If HTML, just stores it in RAM and parses it for OG meta tags -<ul> -<li>Download any media OG meta tags to the media repo, and refer to them in the OG via mxc:// URIs.</li> -</ul> -</li> -<li>If a media filetype we know we can thumbnail: store it on disk, and hand it to the thumbnailer. Generate OG meta tags from the thumbnailer contents.</li> -<li>Otherwise, don't bother downloading further.</li> -</ul> -</li> -</ul> - - </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> \ No newline at end of file |