[WPT/common/security-features] Introduce downgrade redirection

As preparation for migrating wpt/upgrade-insecure-requests
to the /common/security-features generator framework
in https://chromium-review.googlesource.com/c/chromium/src/+/1788551,
this CL introduces `downgrade` redirection type,
which is to be used to test upgrading on redirects.

Bug: 1001422
Change-Id: I590015cdb48c9814135dbd61a91aa318ddeba2fc
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1787571Reviewed-by: Kenichi Ishibashi <bashi@chromium.org>
Reviewed-by: Hiroki Nakagawa <nhiroki@chromium.org>
Reviewed-by: Mike West <mkwst@chromium.org>
Commit-Queue: Hiroshige Hayashizaki <hiroshige@chromium.org>
Cr-Commit-Position: refs/heads/master@{#695934}

third_party/blink/web_tests/external/wpt/common/security-features/subresource/subresource.py

@@ -32,10 +32,15 @@ def __get_swapped_origin_netloc(netloc, subdomain_prefix = "www1."):
 # current request URL `request.url`, except for:
 # - When `swap_scheme` or `swap_origin` is True, its scheme/origin is changed
 #   to the other one. (http <-> https, ws <-> wss, etc.)
+# - For `downgrade`, we redirect to a URL that would be successfully loaded
+#   if and only if upgrade-insecure-request is applied.
 # - `query_parameter_to_remove` parameter is removed from query part.
 #   Its default is "redirection" to avoid redirect loops.
-def create_url(request, swap_scheme = False, swap_origin = False,
-               query_parameter_to_remove = "redirection"):
+def create_url(request,
+               swap_scheme=False,
+               swap_origin=False,
+               downgrade=False,
+               query_parameter_to_remove="redirection"):
     parsed = urlparse.urlsplit(request.url)
     destination_netloc = parsed.netloc
 
@@ -46,6 +51,24 @@ def create_url(request, swap_scheme = False, swap_origin = False,
         port = request.server.config["ports"][scheme][0]
         destination_netloc = ":".join([hostname, str(port)])
 
+    if downgrade:
+        # These rely on some unintuitive cleverness due to WPT's test setup:
+        # 'Upgrade-Insecure-Requests' does not upgrade the port number,
+        # so we use URLs in the form `http://[domain]:[https-port]`,
+        # which will be upgraded to `https://[domain]:[https-port]`.
+        # If the upgrade fails, the load will fail, as we don't serve HTTP over
+        # the secure port.
+        if parsed.scheme == "https":
+            scheme = "http"
+        elif parsed.scheme == "wss":
+            scheme = "ws"
+        else:
+            raise ValueError("Downgrade redirection: Invalid scheme '%s'" %
+                             parsed.scheme)
+        hostname = parsed.netloc.split(':')[0]
+        port = request.server.config["ports"][parsed.scheme][0]
+        destination_netloc = ":".join([hostname, str(port)])
+
     if swap_origin:
         destination_netloc = __get_swapped_origin_netloc(destination_netloc)
 
@@ -75,6 +98,8 @@ def preprocess_redirection(request, response):
         redirect_url = create_url(request, swap_scheme=False)
     elif redirection == "swap-scheme":
         redirect_url = create_url(request, swap_scheme=True)
+    elif redirection == "downgrade":
+        redirect_url = create_url(request, downgrade=True)
     elif redirection == "keep-origin":
         redirect_url = create_url(request, swap_origin=False)
     elif redirection == "swap-origin":

third_party/blink/web_tests/external/wpt/common/security-features/tools/spec_validator.py

@@ -205,9 +205,11 @@ def validate(spec_json, details):
         test_expansion_schema, 'source_context_list',
         spec_json['source_context_list_schema'].keys())
 
+    # Should be consistent with `preprocess_redirection` in
+    # `/common/security-features/subresource/subresource.py`.
     assert_atom_or_list_items_from(test_expansion_schema, 'redirection', [
         'no-redirect', 'keep-origin', 'swap-origin', 'keep-scheme',
-        'swap-scheme'
+        'swap-scheme', 'downgrade'
     ])
     for subresource in leaf_values(test_expansion_schema['subresource']):
         assert subresource in valid_subresource_names, "Invalid subresource %s" % subresource