Add support for no_proxy and case insensitive env variables (#9372)

### Changes proposed in this PR

- Add support for the `no_proxy` and `NO_PROXY` environment variables
  - Internally rely on urllib's [`proxy_bypass_environment`](https://github.com/python/cpython/blob/bdb941be423bde8b02a5695ccf51c303d6204bed/Lib/urllib/request.py#L2519)
- Extract env variables using urllib's `getproxies`/[`getproxies_environment`](https://github.com/python/cpython/blob/bdb941be423bde8b02a5695ccf51c303d6204bed/Lib/urllib/request.py#L2488) which supports lowercase + uppercase, preferring lowercase, except for `HTTP_PROXY` in a CGI environment

This does contain behaviour changes for consumers so making sure these are called out:
- `no_proxy`/`NO_PROXY` is now respected
- lowercase `https_proxy` is now allowed and taken over `HTTPS_PROXY`

Related to #9306 which also uses `ProxyAgent`

Signed-off-by: Timothy Leung tim95@hotmail.co.uk

1 files changed, 2 insertions, 8 deletions

diff --git a/synapse/server.py b/synapse/server.py

index 4b9ec7f0ae..1d4370e0ba 100644
--- a/synapse/server.py
+++ b/synapse/server.py
@@ -24,7 +24,6 @@
 import abc
 import functools
 import logging
-import os
 from typing import (
     TYPE_CHECKING,
     Any,
@@ -370,11 +369,7 @@ class HomeServer(metaclass=abc.ABCMeta):
         """
         An HTTP client that uses configured HTTP(S) proxies.
         """
-        return SimpleHttpClient(
-            self,
-            http_proxy=os.getenvb(b"http_proxy"),
-            https_proxy=os.getenvb(b"HTTPS_PROXY"),
-        )
+        return SimpleHttpClient(self, use_proxy=True)
 
     @cache_in_self
     def get_proxied_blacklisted_http_client(self) -> SimpleHttpClient:
@@ -386,8 +381,7 @@ class HomeServer(metaclass=abc.ABCMeta):
             self,
             ip_whitelist=self.config.ip_range_whitelist,
             ip_blacklist=self.config.ip_range_blacklist,
-            http_proxy=os.getenvb(b"http_proxy"),
-            https_proxy=os.getenvb(b"HTTPS_PROXY"),
+            use_proxy=True,
         )
 
     @cache_in_self