dir/server: allow complete Access file Lookup with AnyRight

Closes a discrepancy Dave found when writing the DirCache:
It's possible to do a WhichAccess with only AnyRight and the blocks are
not removed (not marked incomplete), so it's possible to fetch the
blocks and Get the Access file. However, a Lookup would mark the blocks
as incomplete. This makes it so Access and Group files are readable by anyone with
AnyRights, since they're necessary for offline verification of rights.

Change-Id: I39d7cac3ddca37cb30fdcfc36a4c92a14ce10cdc
Reviewed-on: https://upspin-review.googlesource.com/10840
Reviewed-by: David Presotto <[email protected]>
Reviewed-by: Andrew Gerrand <[email protected]>

dir/server/all_test.go

@@ -875,6 +875,25 @@ func TestPermissionDenied(t *testing.T) {
 	}
 }
 
+func TestAccessAndGroupFilesNotIncomplete(t *testing.T) {
+	const userAccess = userName + "/Access"
+	s, userCtx := newDirServerForTesting(t, userName)
+	// Access file permits List rights for otherUser.
+	_, err := putAccessOrGroupFile(t, s, userCtx, userAccess, "l:"+otherUser)
+	if err != nil {
+		t.Fatal(err)
+	}
+	sOther, _ := newDirServerForTesting(t, otherUser)
+
+	entry, err := sOther.Lookup(userAccess)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if entry.IsIncomplete() {
+		t.Fatalf("Got incomplete entry, expected blocks")
+	}
+}
+
 func TestOverwriteFileWithWrongSequence(t *testing.T) {
 	s, userCtx := newDirServerForTesting(t, userName)
 	_, err := putAccessOrGroupFile(t, s, userCtx, userName+"/Access", "*:"+userName)

dir/server/server.go

@@ -239,7 +239,9 @@ func (s *server) lookupWithPermissions(op string, name upspin.PathName, opts ...
 		if !canAny {
 			return nil, s.errPerm(op, p, opts...)
 		}
-		entry.MarkIncomplete()
+		if !access.IsAccessFile(name) && !access.IsGroupFile(name) {
+			entry.MarkIncomplete()
+		}
 	}
 	return entry, nil
 }