[FIX] direct get APIs can contain duplicate Nats-* headers, because…

… it simply appends JSON bytes to existing headers. If the message was onboarded on a republish, this will contain system headers. Since headers are not ordered and can contain multiple values for the same header, this can break KV clients as well as create ambiguity on the stream that yielded the message.

Fix #4573

server/jetstream_test.go

@@ -21931,3 +21931,52 @@ func TestJetStreamFilteredSubjectUsesNewConsumerCreateSubject(t *testing.T) {
 		},
 	})
 }
+
+func TestJetStreamNoDuplicateHeadersOnDirectGet(t *testing.T) {
+	s := RunBasicJetStreamServer(t)
+	defer s.Shutdown()
+
+	nc, _ := jsClientConnect(t, s)
+	defer nc.Close()
+
+	name := nuid.Next()
+
+	req := StreamConfig{
+		Name:     name,
+		Storage:  MemoryStorage,
+		Subjects: []string{fmt.Sprintf("%s.>", name)},
+		RePublish: &RePublish{
+			Source:      ">",
+			Destination: fmt.Sprintf("X%s.>", name),
+		},
+	}
+	reqJson, err := json.Marshal(req)
+	require_NoError(t, err)
+	_, err = nc.Request(fmt.Sprintf(JSApiStreamCreateT, name), reqJson, time.Second)
+	require_NoError(t, err)
+
+	targetStream := fmt.Sprintf("%s-2", name)
+	req = StreamConfig{
+		Name:        targetStream,
+		Storage:     MemoryStorage,
+		Subjects:    []string{fmt.Sprintf("X%s.>", name)},
+		AllowDirect: true,
+	}
+	reqJson, err = json.Marshal(req)
+	require_NoError(t, err)
+	_, err = nc.Request(fmt.Sprintf(JSApiStreamCreateT, req.Name), reqJson, time.Second)
+	require_NoError(t, err)
+
+	// Now publish a message to the source stream.
+	sendStreamMsg(t, nc, fmt.Sprintf("%s.data", name), "data")
+
+	getSubj := fmt.Sprintf(JSDirectMsgGetT, targetStream)
+
+	r, err := nc.Request(getSubj, []byte("{\"seq\":1}"), time.Second)
+	require_NoError(t, err)
+
+	require_Equal(t, len(r.Header.Values(JSStream)), 1)
+	require_Equal(t, len(r.Header.Values(JSSubject)), 1)
+	require_Equal(t, len(r.Header.Values(JSSequence)), 1)
+	require_Equal(t, len(r.Header.Values(JSTimeStamp)), 1)
+}

server/stream.go

@@ -4051,9 +4051,13 @@ func (mset *stream) getDirectRequest(req *JSApiMsgGetRequest, reply string) {
 		hdr = []byte(fmt.Sprintf(ht, name, sm.subj, sm.seq, ts.Format(time.RFC3339Nano)))
 	} else {
 		hdr = copyBytes(hdr)
+		hdr = removeHeaderIfPresent(hdr, JSStream)
 		hdr = genHeader(hdr, JSStream, name)
+		hdr = removeHeaderIfPresent(hdr, JSSubject)
 		hdr = genHeader(hdr, JSSubject, sm.subj)
+		hdr = removeHeaderIfPresent(hdr, JSSequence)
 		hdr = genHeader(hdr, JSSequence, strconv.FormatUint(sm.seq, 10))
+		hdr = removeHeaderIfPresent(hdr, JSTimeStamp)
 		hdr = genHeader(hdr, JSTimeStamp, ts.Format(time.RFC3339Nano))
 	}
 	mset.outq.send(newJSPubMsg(reply, _EMPTY_, _EMPTY_, hdr, sm.msg, nil, 0))