Add recursion check when parsing unknown fields in Java.

PiperOrigin-RevId: 675657198

java/core/BUILD.bazel

@@ -608,6 +608,7 @@ junit_tests(
             "src/test/java/com/google/protobuf/DescriptorsTest.java",
             "src/test/java/com/google/protobuf/DebugFormatTest.java",
             "src/test/java/com/google/protobuf/CodedOutputStreamTest.java",
+            "src/test/java/com/google/protobuf/CodedInputStreamTest.java",
             "src/test/java/com/google/protobuf/ProtobufToStringOutputTest.java",
             # Excluded in core_tests
             "src/test/java/com/google/protobuf/DecodeUtf8Test.java",
@@ -656,6 +657,7 @@ junit_tests(
             "src/test/java/com/google/protobuf/DescriptorsTest.java",
             "src/test/java/com/google/protobuf/DebugFormatTest.java",
             "src/test/java/com/google/protobuf/CodedOutputStreamTest.java",
+            "src/test/java/com/google/protobuf/CodedInputStreamTest.java",
             "src/test/java/com/google/protobuf/ProtobufToStringOutputTest.java",
             # Excluded in core_tests
             "src/test/java/com/google/protobuf/DecodeUtf8Test.java",

java/core/src/main/java/com/google/protobuf/ArrayDecoders.java

@@ -23,6 +23,10 @@
  */
 @CheckReturnValue
 final class ArrayDecoders {
+  static final int DEFAULT_RECURSION_LIMIT = 100;
+
+  @SuppressWarnings("NonFinalStaticField")
+  private static volatile int recursionLimit = DEFAULT_RECURSION_LIMIT;
 
   private ArrayDecoders() {}
 
@@ -37,6 +41,7 @@ static final class Registers {
     public long long1;
     public Object object1;
     public final ExtensionRegistryLite extensionRegistry;
+    public int recursionDepth;
 
     Registers() {
       this.extensionRegistry = ExtensionRegistryLite.getEmptyRegistry();
@@ -244,7 +249,10 @@ static int mergeMessageField(
     if (length < 0 || length > limit - position) {
       throw InvalidProtocolBufferException.truncatedMessage();
     }
+    registers.recursionDepth++;
+    checkRecursionLimit(registers.recursionDepth);
     schema.mergeFrom(msg, data, position, position + length, registers);
+    registers.recursionDepth--;
     registers.object1 = msg;
     return position + length;
   }
@@ -262,8 +270,11 @@ static int mergeGroupField(
     // A group field must has a MessageSchema (the only other subclass of Schema is MessageSetSchema
     // and it can't be used in group fields).
     final MessageSchema messageSchema = (MessageSchema) schema;
+    registers.recursionDepth++;
+    checkRecursionLimit(registers.recursionDepth);
     final int endPosition =
         messageSchema.parseMessage(msg, data, position, limit, endGroup, registers);
+    registers.recursionDepth--;
     registers.object1 = msg;
     return endPosition;
   }
@@ -1024,6 +1035,8 @@ static int decodeUnknownField(
         final UnknownFieldSetLite child = UnknownFieldSetLite.newInstance();
         final int endGroup = (tag & ~0x7) | WireFormat.WIRETYPE_END_GROUP;
         int lastTag = 0;
+        registers.recursionDepth++;
+        checkRecursionLimit(registers.recursionDepth);
         while (position < limit) {
           position = decodeVarint32(data, position, registers);
           lastTag = registers.int1;
@@ -1032,6 +1045,7 @@ static int decodeUnknownField(
           }
           position = decodeUnknownField(lastTag, data, position, limit, child, registers);
         }
+        registers.recursionDepth--;
         if (position > limit || lastTag != endGroup) {
           throw InvalidProtocolBufferException.parseFailure();
         }
@@ -1078,4 +1092,18 @@ static int skipField(int tag, byte[] data, int position, int limit, Registers re
         throw InvalidProtocolBufferException.invalidTag();
     }
   }
+
+  /**
+   * Set the maximum recursion limit that ArrayDecoders will allow. An exception will be thrown if
+   * the depth of the message exceeds this limit.
+   */
+  public static void setRecursionLimit(int limit) {
+    recursionLimit = limit;
+  }
+
+  private static void checkRecursionLimit(int depth) throws InvalidProtocolBufferException {
+    if (depth >= recursionLimit) {
+      throw InvalidProtocolBufferException.recursionLimitExceeded();
+    }
+  }
 }

java/core/src/main/java/com/google/protobuf/CodedInputStream.java

@@ -230,7 +230,10 @@ public void skipMessage() throws IOException {
       if (tag == 0) {
         return;
       }
+      checkRecursionLimit();
+      ++recursionDepth;
       boolean fieldSkipped = skipField(tag);
+      --recursionDepth;
       if (!fieldSkipped) {
         return;
       }
@@ -247,7 +250,10 @@ public void skipMessage(CodedOutputStream output) throws IOException {
       if (tag == 0) {
         return;
       }
+      checkRecursionLimit();
+      ++recursionDepth;
       boolean fieldSkipped = skipField(tag, output);
+      --recursionDepth;
       if (!fieldSkipped) {
         return;
       }

java/core/src/main/java/com/google/protobuf/MessageSchema.java

@@ -3006,8 +3006,8 @@ private <UT, UB, ET extends FieldDescriptorLite<ET>> void mergeFromHelper(
               unknownFields = unknownFieldSchema.getBuilderFromMessage(message);
             }
             // Unknown field.
-
-            if (unknownFieldSchema.mergeOneFieldFrom(unknownFields, reader)) {
+            if (unknownFieldSchema.mergeOneFieldFrom(
+                unknownFields, reader, /* currentDepth= */ 0)) {
               continue;
             }
           }
@@ -3382,8 +3382,8 @@ private <UT, UB, ET extends FieldDescriptorLite<ET>> void mergeFromHelper(
               if (unknownFields == null) {
                 unknownFields = unknownFieldSchema.getBuilderFromMessage(message);
               }
-
-              if (!unknownFieldSchema.mergeOneFieldFrom(unknownFields, reader)) {
+              if (!unknownFieldSchema.mergeOneFieldFrom(
+                  unknownFields, reader, /* currentDepth= */ 0)) {
                 return;
               }
               break;
@@ -3399,8 +3399,8 @@ private <UT, UB, ET extends FieldDescriptorLite<ET>> void mergeFromHelper(
             if (unknownFields == null) {
               unknownFields = unknownFieldSchema.getBuilderFromMessage(message);
             }
-
-            if (!unknownFieldSchema.mergeOneFieldFrom(unknownFields, reader)) {
+            if (!unknownFieldSchema.mergeOneFieldFrom(
+                unknownFields, reader, /* currentDepth= */ 0)) {
               return;
             }
           }

java/core/src/main/java/com/google/protobuf/MessageSetSchema.java

@@ -278,8 +278,7 @@ boolean parseMessageSetItemOrUnknownField(
               reader, extension, extensionRegistry, extensions);
           return true;
         } else {
-
-          return unknownFieldSchema.mergeOneFieldFrom(unknownFields, reader);
+          return unknownFieldSchema.mergeOneFieldFrom(unknownFields, reader, /* currentDepth= */ 0);
         }
       } else {
         return reader.skipField();

java/core/src/main/java/com/google/protobuf/UnknownFieldSchema.java

@@ -13,6 +13,11 @@
 @CheckReturnValue
 abstract class UnknownFieldSchema<T, B> {
 
+  static final int DEFAULT_RECURSION_LIMIT = 100;
+
+  @SuppressWarnings("NonFinalStaticField")
+  private static volatile int recursionLimit = DEFAULT_RECURSION_LIMIT;
+
   /** Whether unknown fields should be dropped. */
   abstract boolean shouldDiscardUnknownFields(Reader reader);
 
@@ -55,7 +60,9 @@ abstract class UnknownFieldSchema<T, B> {
   /** Marks unknown fields as immutable. */
   abstract void makeImmutable(Object message);
 
-  final boolean mergeOneFieldFrom(B unknownFields, Reader reader) throws IOException {
+  /** Merges one field into the unknown fields. */
+  final boolean mergeOneFieldFrom(B unknownFields, Reader reader, int currentDepth)
+      throws IOException {
     int tag = reader.getTag();
     int fieldNumber = WireFormat.getTagFieldNumber(tag);
     switch (WireFormat.getTagWireType(tag)) {
@@ -74,7 +81,12 @@ final boolean mergeOneFieldFrom(B unknownFields, Reader reader) throws IOExcepti
       case WireFormat.WIRETYPE_START_GROUP:
         final B subFields = newBuilder();
         int endGroupTag = WireFormat.makeTag(fieldNumber, WireFormat.WIRETYPE_END_GROUP);
-        mergeFrom(subFields, reader);
+        currentDepth++;
+        if (currentDepth >= recursionLimit) {
+          throw InvalidProtocolBufferException.recursionLimitExceeded();
+        }
+        mergeFrom(subFields, reader, currentDepth);
+        currentDepth--;
         if (endGroupTag != reader.getTag()) {
           throw InvalidProtocolBufferException.invalidEndTag();
         }
@@ -87,10 +99,11 @@ final boolean mergeOneFieldFrom(B unknownFields, Reader reader) throws IOExcepti
     }
   }
 
-  private final void mergeFrom(B unknownFields, Reader reader) throws IOException {
+  private final void mergeFrom(B unknownFields, Reader reader, int currentDepth)
+      throws IOException {
     while (true) {
       if (reader.getFieldNumber() == Reader.READ_DONE
-          || !mergeOneFieldFrom(unknownFields, reader)) {
+          || !mergeOneFieldFrom(unknownFields, reader, currentDepth)) {
         break;
       }
     }
@@ -107,4 +120,12 @@ private final void mergeFrom(B unknownFields, Reader reader) throws IOException
   abstract int getSerializedSizeAsMessageSet(T message);
 
   abstract int getSerializedSize(T unknowns);
+
+  /**
+   * Set the maximum recursion limit that ArrayDecoders will allow. An exception will be thrown if
+   * the depth of the message exceeds this limit.
+   */
+  public void setRecursionLimit(int limit) {
+    recursionLimit = limit;
+  }
 }