[bug] Handle 410 on webfinger properly (#1601)

When we receive an HTTP 410 on webfinger it means the resource we asked
for (the account) is gone, but the endpoint itself responded. In such
cases we want to treat the request as successful from a cache (renewal)
point of view, while still returning an error from Finger.

Follow-up for #1588

1 files changed, 17 insertions, 5 deletions

diff --git a/internal/transport/finger.go b/internal/transport/finger.go
index 6631ff8f1..f1d93c0f9 100644
--- a/internal/transport/finger.go
+++ b/internal/transport/finger.go
@@ -82,14 +82,19 @@ func (t *transport) Finger(ctx context.Context, targetUsername string, targetDom
 	}
 	defer rsp.Body.Close()
 
-	// Check if the request succeeded so we can bail out early
-	if rsp.StatusCode == http.StatusOK {
+	// Check if the request succeeded so we can bail out early or if we explicitly
+	// got a "this resource is gone" response which will happen when a user has
+	// deleted the account
+	if rsp.StatusCode == http.StatusOK || rsp.StatusCode == http.StatusGone {
 		if cached {
-			// If we got a success on a cached URL, i.e one set by us later on when
-			// a host-meta based webfinger request succeeded, set it again here to
-			// renew the TTL
+			// If we got a response we consider successful on a cached URL, i.e one set
+			// by us later on when a host-meta based webfinger request succeeded, set it
+			// again here to renew the TTL
 			t.controller.state.Caches.GTS.Webfinger().Set(targetDomain, url)
 		}
+		if rsp.StatusCode == http.StatusGone {
+			return nil, fmt.Errorf("account has been deleted/is gone")
+		}
 		return io.ReadAll(rsp.Body)
 	}
 
@@ -135,6 +140,13 @@ func (t *transport) Finger(ctx context.Context, targetUsername string, targetDom
 	defer rsp.Body.Close()
 
 	if rsp.StatusCode != http.StatusOK {
+		// A HTTP 410 indicates we got a response to our webfinger query, but the resource
+		// we asked for is gone. This means the endpoint itself is valid and we should
+		// cache it for future queries to the same domain
+		if rsp.StatusCode == http.StatusGone {
+			t.controller.state.Caches.GTS.Webfinger().Set(targetDomain, host)
+			return nil, fmt.Errorf("account has been deleted/is gone")
+		}
 		// We've reached the end of the line here, both the original request
 		// and our attempt to resolve it through the fallback have failed
 		return nil, fmt.Errorf("GET request to %s failed: %s", req.URL.String(), rsp.Status)