[webid] Allow idp_endpoint to be a relative URL

The idp_endpoint property today of the .well-known/webid response is now
taken as an absolute URL, which makes it inconvenient for deployment.

In this CL we resolve the idp_endpoint URL as a relative URL to the file
that it is contained in, allowing both absolute URLs and relative URLs
to co-exist.

Bug: 1141125
Change-Id: I224274634e5eaf7f7d66d044931fe5823f346829
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2631295
Auto-Submit: Sam Goto <goto@chromium.org>
Reviewed-by: Ken Buchanan <kenrb@chromium.org>
Commit-Queue: Ken Buchanan <kenrb@chromium.org>
Cr-Commit-Position: refs/heads/master@{#844993}

content/browser/webid/federated_auth_request_impl.cc

@@ -128,7 +128,11 @@ void FederatedAuthRequestImpl::OnWellKnownFetched(
     }
   }
 
-  idp_endpoint_url_ = GURL(base::StringPiece(idp_endpoint));
+  const url::Origin& idp_origin = url::Origin::Create(provider_);
+  GURL well_known_url =
+      idp_origin.GetURL().Resolve(IdpNetworkRequestManager::kWellKnownFilePath);
+  idp_endpoint_url_ = well_known_url.Resolve(idp_endpoint);
+
   // TODO(kenrb): This has to be same-origin with the provider.
   // https://crbug.com/1141125
   if (!IdpUrlIsValid(idp_endpoint_url_)) {

content/browser/webid/idp_network_request_manager.cc

@@ -22,7 +22,6 @@ namespace content {
 namespace {
 // TODO(kenrb): These need to be defined in the explainer or draft spec and
 // referenced here.
-constexpr char kWellKnownFilePath[] = ".well-known/webid";
 
 // Well-known configuration keys.
 constexpr char kIdpEndpointKey[] = "idp_endpoint";
@@ -80,6 +79,9 @@ scoped_refptr<network::SharedURLLoaderFactory> GetUrlLoaderFactory(
 
 }  // namespace
 
+// static
+constexpr char IdpNetworkRequestManager::kWellKnownFilePath[];
+
 // static
 std::unique_ptr<IdpNetworkRequestManager> IdpNetworkRequestManager::Create(
     const GURL& provider,
@@ -105,7 +107,8 @@ void IdpNetworkRequestManager::FetchIDPWellKnown(
   idp_well_known_callback_ = std::move(callback);
 
   const url::Origin& idp_origin = url::Origin::Create(provider_);
-  GURL target_url = idp_origin.GetURL().Resolve(kWellKnownFilePath);
+  GURL target_url =
+      idp_origin.GetURL().Resolve(IdpNetworkRequestManager::kWellKnownFilePath);
 
   net::NetworkTrafficAnnotationTag traffic_annotation =
       CreateTrafficAnnotation();

content/browser/webid/idp_network_request_manager.h

@@ -64,6 +64,8 @@ class IdpNetworkRequestManager {
     kInvalidResponseError,
   };
 
+  static constexpr char kWellKnownFilePath[] = ".well-known/webid";
+
   using FetchWellKnownCallback =
       base::OnceCallback<void(FetchStatus, const std::string&)>;
   using SigninRequestCallback =