docs: add separate page for cors-settings to mention cors settings for both regular replayweb.page usage and embedding, link from embedding guide (#205)

addresses #74, #168, #202
2023-08-11 18:23:10 -07:00
parent 79e4c2a77e
commit 2dd82345bd
5 changed files with 131 additions and 36 deletions
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+---
+layout: default
+title: Configuring Server CORS
+nav_order: 4
+permalink: /docs/cors-settings
+---
+
+ReplayWeb.page doesn't require any specific server side settings, just the ability to server file and respond to `Range` requests,
+loading parts of files. It can load files from any web server. However, a common obstacle is configuring CORS settings to give
+ReplayWeb.page access to the data.
+
+# Configuring CORS
+
+Browsers restrict access to files hosted on a different domain than the websites that is trying to load them for security reasons.
+
+If you are loading web archives hosted on a different domain (for example, S3 or other cloud storage) and your site is hosted on a different domain,
+the site hosting the file needs to 'allow' the website to load the file using special CORS (Cross-Origin Resource Sharing) headers.
+
+These settings apply whenever the archive is hosted on a different domain than the viewer, so if you are loading via our main ReplayWeb.page site, you need to grant access to *https://replayweb.page* to load these archives.
+
+The minimum requirement is to return an `Access-Control-Allow-Origin: https://replayweb.page` and most CORS settings include at least this option.
+
+## Differences between Chrome and Firefox and Safari
+
+Unfortunately, different browsers have diverged in how they handle in enforcing the CORS policy.
+
+At the moment, it seems Firefox and Safari sometimes send a [pre-flight OPTIONS request](https://developer.mozilla.org/en-US/docs/Glossary/Preflight_request) when handling ReplayWeb.page requests, because the ReplayWeb.page uses the `Range` header.
+
+Chrome currently considers it a 'safe' header, but the other browsers have not yet made this change.
+
+To be compatible with all browsers, we recommend including all headers as 'allowed headers' for use with ReplayWeb.page, eg.
+by setting `Access-Control-Allow-Headers: '*'` as part of the CORS response in addition to `Access-Control-Allow-Origin`.
+
+The following provides different ways of configuring CORS for different hosting environments.
+
+
+## S3 and Compatible Configurations
+
+If you are hosting from S3 or S3-compatible service, here are a few CORS bucket configurations that should work.
+
+Amazon S3 and other services now support a JSON based bucket policy, as well as an older XML-based policy.
+
+The below examples provide access to `https://replayweb.page` to load your archive.
+If you are instead [embedding replayweb.page](./embedding), replace that with the server (origin) of the URL where the `<replay-web-page>` embed is hosted.
+
+Both JSON and XML options provide a way to specify multiple origins via the JSON list or multiple `<AllowedOrigin>` tags
+
+### JSON-Based Configuration
+
+The JSON-based configuration will look as follows:
+
+```json
+[
+  {
+    "AllowedOrigins": [
+      "https://replayweb.page"
+    ],
+    "AllowedMethods": [
+      "GET",
+      "HEAD"
+    ],
+    "AllowedHeaders": [
+      "*"
+    ]
+  }
+]
+```
+
+### XML-Based Configuration
+
+
+```xml
+<CORSConfiguration
+xmlns="http://s3.amazonaws.com/doc/2006-03-01/">
+<CORSRule>
+  <AllowedMethod>GET</AllowedMethod>
+  <AllowedMethod>HEAD</AllowedMethod>
+  <AllowedOrigin>https://replayweb.page</AllowedOrigin>
+  <AllowedHeader>*</AllowedHeader>
+  <ExposeHeader>Content-Range</ExposeHeader>
+  <ExposeHeader>Content-Encoding</ExposeHeader>
+  <ExposeHeader>Content-Length</ExposeHeader>
+</CORSRule>
+</CORSConfiguration>
+```
+
+One way to set this policy is to use the popular [s3cmd](https://s3tools.org/usage) command-line tool:
+
+1) Paste the above snippet into a file, eg. `cors.xml`
+2) Be sure to set the 'Allowed Origin' to the site hosting the embed. You can add as many of these as necessary.
+3) Run `s3cmd setcors ./cors.xml s3://<your-bucket>`
+
+See the s3cmd docs for how to configure it s3cmd to work with your setup.
+
+See [S3 Docs](https://docs.aws.amazon.com/AmazonS3/latest/userguide/ManageCorsUsing.html) for more info on how to set this policy.
+
+Other cloud providers may have a similar settings for configuring CORS.
+
+## Manual Setup / Nginx
+
+The recommended setup for nginx is to include the following CORS settings.
+As above, you can replay `https://replayweb.page` with your domain:
+
+```nginx
+location / {
+     if ($request_method = 'OPTIONS') {
+        add_header 'Access-Control-Allow-Origin' 'https://replayweb.page';
+        add_header 'Access-Control-Allow-Methods' 'GET, HEAD, OPTIONS' always;
+        add_header 'Access-Control-Allow-Headers' '*'
+        return 204;
+     }
+
+     if ($request_method = 'GET') {
+        add_header 'Access-Control-Allow-Origin' 'https://replayweb.page' always;
+        add_header 'Access-Control-Allow-Methods' 'GET, POST, OPTIONS' always;
+        add_header 'Access-Control-Allow-Headers' '*' always;
+        add_header 'Access-Control-Expose-Headers' 'Content-Length,Content-Range' always;
+     }
+}
+```
+
+For more examples of CORS configurations for different servers, see: [https://enable-cors.org/](https://enable-cors.org/)
+
+