root: backport s3 storage changes (#11181)

re-add _strip_signing_parameters
removed in https://github.com/jschneier/django-storages/pull/1402
could probably be re-factored to use the same approach that PR uses

Signed-off-by: Jens Langhammer <jens@goauthentik.io>

authentik/root/storages.py

@@ -1,6 +1,7 @@
 """authentik storage backends"""
 
 import os
+from urllib.parse import parse_qsl, urlsplit
 
 from django.conf import settings
 from django.core.exceptions import SuspiciousOperation
@@ -110,3 +111,34 @@ class S3Storage(BaseS3Storage):
         if self.querystring_auth:
             return url
         return self._strip_signing_parameters(url)
+
+    def _strip_signing_parameters(self, url):
+        # Boto3 does not currently support generating URLs that are unsigned. Instead
+        # we take the signed URLs and strip any querystring params related to signing
+        # and expiration.
+        # Note that this may end up with URLs that are still invalid, especially if
+        # params are passed in that only work with signed URLs, e.g. response header
+        # params.
+        # The code attempts to strip all query parameters that match names of known
+        # parameters from v2 and v4 signatures, regardless of the actual signature
+        # version used.
+        split_url = urlsplit(url)
+        qs = parse_qsl(split_url.query, keep_blank_values=True)
+        blacklist = {
+            "x-amz-algorithm",
+            "x-amz-credential",
+            "x-amz-date",
+            "x-amz-expires",
+            "x-amz-signedheaders",
+            "x-amz-signature",
+            "x-amz-security-token",
+            "awsaccesskeyid",
+            "expires",
+            "signature",
+        }
+        filtered_qs = ((key, val) for key, val in qs if key.lower() not in blacklist)
+        # Note: Parameters that did not have a value in the original query string will
+        # have an '=' sign appended to it, e.g ?foo&bar becomes ?foo=&bar=
+        joined_qs = ("=".join(keyval) for keyval in filtered_qs)
+        split_url = split_url._replace(query="&".join(joined_qs))
+        return split_url.geturl()