core (fix): Fix MessageUnpacker.unpackValue to check the custom stringSizeLimit (#753)

* core (fix): Fix MessageUnpacker.unpackValue to check the custom stringSizeLimit

* Cover unpackVariable(var)

Author: xerial

msgpack-core/src/main/java/org/msgpack/core/MessageUnpacker.java

@@ -624,6 +624,9 @@ public ImmutableValue unpackValue()
                 return ValueFactory.newFloat(unpackDouble());
             case STRING: {
                 int length = unpackRawStringHeader();
+                if (length > stringSizeLimit) {
+                    throw new MessageSizeException(String.format("cannot unpack a String of size larger than %,d: %,d", stringSizeLimit, length), length);
+                }
                 return ValueFactory.newString(readPayload(length), true);
             }
             case BINARY: {
@@ -689,6 +692,9 @@ public Variable unpackValue(Variable var)
                 return var;
             case STRING: {
                 int length = unpackRawStringHeader();
+                if (length > stringSizeLimit) {
+                    throw new MessageSizeException(String.format("cannot unpack a String of size larger than %,d: %,d", stringSizeLimit, length), length);
+                }
                 var.setStringValue(readPayload(length));
                 return var;
             }

msgpack-core/src/test/scala/org/msgpack/core/StringLimitTest.scala

@@ -0,0 +1,37 @@
+package org.msgpack.core
+
+import org.msgpack.core.MessagePack.UnpackerConfig
+import org.msgpack.value.Variable
+import wvlet.airspec.AirSpec
+
+class StringLimitTest extends AirSpec {
+
+  test("throws an exception when the string size exceeds a limit") {
+    val customLimit = 100
+    val packer      = MessagePack.newDefaultBufferPacker()
+    packer.packString("a" * (customLimit + 1))
+    val msgpack = packer.toByteArray
+
+    test("unpackString") {
+      val unpacker = new UnpackerConfig().withStringSizeLimit(customLimit).newUnpacker(msgpack)
+      intercept[MessageSizeException] {
+        unpacker.unpackString()
+      }
+    }
+
+    test("unpackValue") {
+      val unpacker = new UnpackerConfig().withStringSizeLimit(customLimit).newUnpacker(msgpack)
+      intercept[MessageSizeException] {
+        unpacker.unpackValue()
+      }
+    }
+
+    test("unpackValue(var)") {
+      val unpacker = new UnpackerConfig().withStringSizeLimit(customLimit).newUnpacker(msgpack)
+      intercept[MessageSizeException] {
+        val v = new Variable()
+        unpacker.unpackValue(v)
+      }
+    }
+  }
+}