From 34b5a11e20baa36c71b95597f88cbcac73a9c1eb Mon Sep 17 00:00:00 2001
From: "R.I.Pienaar" <rip@devco.net>
Date: Mon, 20 Sep 2021 17:34:48 +0200
Subject: [PATCH] protect against negative dupe window via negative max age

Signed-off-by: R.I.Pienaar <rip@devco.net>
---
 server/jetstream_test.go | 33 +++++++++++++++++++++++++++++++++
 server/stream.go         |  3 ++-
 2 files changed, 35 insertions(+), 1 deletion(-)

diff --git a/server/jetstream_test.go b/server/jetstream_test.go
index 7645e230..469acce3 100644
--- a/server/jetstream_test.go
+++ b/server/jetstream_test.go
@@ -13094,6 +13094,39 @@ func TestJetStreamPullLargeBatchExpired(t *testing.T) {
 	}
 }
 
+func TestNegativeDupeWindow(t *testing.T) {
+	s := RunBasicJetStreamServer()
+	defer s.Shutdown()
+
+	config := s.JetStreamConfig()
+	if config != nil {
+		defer removeDir(t, config.StoreDir)
+	}
+
+	nc, js := jsClientConnect(t, s)
+	defer nc.Close()
+
+	// we incorrectly set MaxAge to -1 which then as a side effect sets dupe window to -1 which should fail
+	_, err := js.AddStream(&nats.StreamConfig{
+		Name:              "TEST",
+		Subjects:          nil,
+		Retention:         nats.WorkQueuePolicy,
+		MaxConsumers:      1,
+		MaxMsgs:           -1,
+		MaxBytes:          -1,
+		Discard:           nats.DiscardNew,
+		MaxAge:            -1,
+		MaxMsgsPerSubject: -1,
+		MaxMsgSize:        -1,
+		Storage:           nats.FileStorage,
+		Replicas:          1,
+		NoAck:             false,
+	})
+	if err == nil || err.Error() != "duplicates window can not be negative" {
+		t.Fatalf("Expected dupe window error got: %v", err)
+	}
+}
+
 ///////////////////////////////////////////////////////////////////////////
 // Simple JetStream Benchmarks
 ///////////////////////////////////////////////////////////////////////////
diff --git a/server/stream.go b/server/stream.go
index 15671ab0..62c76a59 100644
--- a/server/stream.go
+++ b/server/stream.go
@@ -796,7 +796,8 @@ func checkStreamCfg(config *StreamConfig) (StreamConfig, error) {
 		} else {
 			cfg.Duplicates = StreamDefaultDuplicatesWindow
 		}
-	} else if cfg.Duplicates < 0 {
+	}
+	if cfg.Duplicates < 0 {
 		return StreamConfig{}, fmt.Errorf("duplicates window can not be negative")
 	}
 	// Check that duplicates is not larger then age if set.