Fail framing stage if length field is less than 0 #22367

akka-stream-tests/src/test/scala/akka/stream/scaladsl/FramingSpec.scala

@@ -10,13 +10,13 @@ import akka.stream._
 import akka.stream.scaladsl.Framing.FramingException
 import akka.stream.stage.{ GraphStage, _ }
 import akka.stream.testkit.{ StreamSpec, TestPublisher, TestSubscriber }
+import akka.testkit.LongRunningTest
 import akka.util.{ ByteString, ByteStringBuilder }
 import org.scalatest.concurrent.PatienceConfiguration.Timeout
 
 import scala.collection.immutable
 import scala.concurrent.duration._
 import scala.util.Random
-import akka.testkit.LongRunningTest
 
 class FramingSpec extends StreamSpec {
 
@@ -265,6 +265,41 @@ class FramingSpec extends StreamSpec {
         .futureValue should ===(testMessages)
     }
 
+    "fail the stage on negative length field values (#22367)" in {
+      implicit val bo = java.nio.ByteOrder.LITTLE_ENDIAN
+
+      // A 4-byte message containing only an Int specifying the length of the payload
+      // The issue shows itself if length in message is less than or equal
+      // to -4 (if expected length field is length 4)
+      val bs = ByteString.newBuilder.putInt(-4).result()
+
+      val res =
+        Source
+          .single(bs)
+          .via(Flow[ByteString].via(Framing.lengthField(4, 0, 1000)))
+          .runWith(Sink.seq)
+
+      val ex = res.failed.futureValue
+      ex shouldBe a[FramingException]
+      ex.getMessage should ===("Decoded frame header reported negative size -4")
+    }
+
+    "let zero length field values pass through (#22367)" in {
+      implicit val bo = java.nio.ByteOrder.LITTLE_ENDIAN
+
+      // Interleave empty frames with a frame with data
+      val encodedPayload = encode(ByteString(42), 0, 4, bo)
+      val emptyFrame = encode(ByteString(), 0, 4, bo)
+      val bs = Vector(emptyFrame, encodedPayload, emptyFrame)
+
+      val res =
+        Source(bs)
+          .via(Flow[ByteString].via(Framing.lengthField(4, 0, 1000)))
+          .runWith(Sink.seq)
+
+      res.futureValue should equal(Seq(emptyFrame, encodedPayload, emptyFrame))
+
+    }
   }
 
 }

akka-stream/src/main/scala/akka/stream/scaladsl/Framing.scala

@@ -266,6 +266,8 @@ object Framing {
           frameSize = parsedLength + minimumChunkSize
           if (frameSize > maximumFrameLength) {
             failStage(new FramingException(s"Maximum allowed frame size is $maximumFrameLength but decoded frame header reported size $frameSize"))
+          } else if (parsedLength < 0) {
+            failStage(new FramingException(s"Decoded frame header reported negative size $parsedLength"))
           } else if (buffSize >= frameSize) {
             pushFrame()
           } else tryPull()