Adding HTTP Method Overrides

Some HTTP proxies do not support arbitrary HTTP methods or newer HTTP methods (such as PATCH). In that case it’s possible to « proxy » HTTP methods through another HTTP method in total violation of the protocol.

The way this works is by letting the client do an HTTP POST request and set the X-HTTP-Method-Override header. Then the method is replaced with the header value before being passed to Flask.

This can be accomplished with an HTTP middleware:

class HTTPMethodOverrideMiddleware(object):
    allowed_methods = frozenset([
    bodyless_methods = frozenset(['GET', 'HEAD', 'OPTIONS', 'DELETE'])

    def __init__(self, app): = app

    def __call__(self, environ, start_response):
        method = environ.get('HTTP_X_HTTP_METHOD_OVERRIDE', '').upper()
        if method in self.allowed_methods:
            environ['REQUEST_METHOD'] = method
        if method in self.bodyless_methods:
            environ['CONTENT_LENGTH'] = '0'
        return, start_response)

To use this with Flask, wrap the app object with the middleware:

from flask import Flask

app = Flask(__name__)
app.wsgi_app = HTTPMethodOverrideMiddleware(app.wsgi_app)