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CORS preflight support for TiddlyWeb

Project description

A plugin for TiddlyWeb to support CORS pre-flight checks.

This is an experiment, with limited functionality. As test cases increase, functionality will increase.

To use add ‘tiddlywebplugins.cors’ to ‘system_plugins’ in

There are a few optional config settings:

If ‘cors.match_origin’ is True, then the value of the Origin header will be the value of the Access-Control-Allow-Origin header, on simple requests. On non-simple request, it always matches. If False the value is ‘*’ (on simple requests).

If ‘cors.allow_creds’ is True, then the Access-Control-Allow-Credentials header will be sent with a value of ‘true’, otherwise it will not be sent.

If ‘cors.exposed_headers’ is set, its should be a list of strings representing header names which are appended to the default Access-Control-Expose-Headers: ETag. This same list is used to set the default of Access-Control-Allow-Headers.

If ‘cors.enable_non_simple’ is True, preflight OPTIONS requests are handled. This defaults to False to avoid accidental exposure.

For authenticated cross-domain PUTs of resources the following config appears to be required:

‘cors.enable_non_simple’: True, ‘cors.allow_creds’: True, ‘cors.match_origin’: True,

The match_origin setting is required for the OPTIONS preflight requests to be handled effectively.


  • Blacklist/Whitelist processing of Access-Control-Request-Headers.

  • Auditing with someone else to confirm that this stuff is “correct”.

  • Refactoring of the two middlewares. There’s a fair bit of overlap. It could become just one that operates on both sides of the internal application, but I find that can be confusing.

Copyright 2012, Chris Dent <>

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