fix: handle opaque attachment references

server/store/file_test.go

@@ -0,0 +1,30 @@
+package store
+
+import (
+	"testing"
+
+	"github.com/tinode/chat/server/store/types"
+)
+
+func TestFileLinkUserIDAllowsOpaqueTopicReferences(t *testing.T) {
+	tests := []struct {
+		name    string
+		topic   string
+		isUser  bool
+		wantUID types.Uid
+	}{
+		{name: "cultivate reference", topic: "cvpbzxw1aio4ni8x0"},
+		{name: "short opaque reference", topic: "x"},
+		{name: "empty reference", topic: ""},
+		{name: "user reference", topic: types.Uid(42).UserId(), isUser: true, wantUID: types.Uid(42)},
+	}
+
+	for _, test := range tests {
+		t.Run(test.name, func(t *testing.T) {
+			gotUID, gotIsUser := fileLinkUserID(test.topic)
+			if gotIsUser != test.isUser || gotUID != test.wantUID {
+				t.Fatalf("fileLinkUserID(%q) = (%v, %v), want (%v, %v)", test.topic, gotUID, gotIsUser, test.wantUID, test.isUser)
+			}
+		})
+	}
+}

server/store/store.go

@@ -4684,8 +4684,8 @@ func (fileMapper) LinkAttachments(tenantID types.TenantID, topic string, msgId t
 			return err
 		}
 		userId := types.ZeroUid
-		if topic != "" && types.GetTopicCat(topic) == types.TopicCatMe {
-			userId = types.ParseUserId(topic)
+		if parsedUserID, ok := fileLinkUserID(topic); ok {
+			userId = parsedUserID
 			topic = ""
 		}
 		return tenantAdp.TenantFileLinkAttachments(tenantID, topic, userId, msgId, fids)
@@ -4693,6 +4693,14 @@ func (fileMapper) LinkAttachments(tenantID types.TenantID, topic string, msgId t
 	return nil
 }
 
+// File link topics may also be opaque retention keys, such as cultivate's cvp prefix.
+func fileLinkUserID(topic string) (types.Uid, bool) {
+	if !strings.HasPrefix(topic, "usr") {
+		return types.ZeroUid, false
+	}
+	return types.ParseUserId(topic), true
+}
+
 func (fileMapper) UserHasAccess(tenantID types.TenantID, fid string, uid types.Uid) (bool, error) {
 	if fid == "" || uid.IsZero() {
 		return false, types.ErrMalformed