[ObjC] Enforce bytes and string field size limits.

PiperOrigin-RevId: 509863774

objectivec/GPBCodedInputStream.m

@@ -51,6 +51,10 @@ NSString *const GPBCodedInputStreamErrorDomain =
 //  int CodedInputStream::default_recursion_limit_ = 100;
 static const NSUInteger kDefaultRecursionLimit = 100;
 
+// Bytes and Strings have a max size of 2GB.
+// https://protobuf.dev/programming-guides/encoding/#cheat-sheet
+static const uint32_t kMaxFieldSize = 0x7fffffff;
+
 static void RaiseException(NSInteger code, NSString *reason) {
   NSDictionary *errorInfo = nil;
   if ([reason length]) {
@@ -223,14 +227,20 @@ int32_t GPBCodedInputStreamReadTag(GPBCodedInputStreamState *state) {
 }
 
 NSString *GPBCodedInputStreamReadRetainedString(GPBCodedInputStreamState *state) {
-  int32_t size = ReadRawVarint32(state);
+  uint64_t size = GPBCodedInputStreamReadUInt64(state);
+  if (size > kMaxFieldSize) {
+    // TODO(thomasvl): Maybe a different error code for this, but adding one is a breaking change
+    // so reuse an existing one.
+    RaiseException(GPBCodedInputStreamErrorInvalidSize, nil);
+  }
+  NSUInteger ns_size = (NSUInteger)size;
   NSString *result;
   if (size == 0) {
     result = @"";
   } else {
     CheckSize(state, size);
     result = [[NSString alloc] initWithBytes:&state->bytes[state->bufferPos]
-                                      length:size
+                                      length:ns_size
                                     encoding:NSUTF8StringEncoding];
     state->bufferPos += size;
     if (!result) {
@@ -246,21 +256,31 @@ NSString *GPBCodedInputStreamReadRetainedString(GPBCodedInputStreamState *state)
 }
 
 NSData *GPBCodedInputStreamReadRetainedBytes(GPBCodedInputStreamState *state) {
-  int32_t size = ReadRawVarint32(state);
-  if (size < 0) return nil;
+  uint64_t size = GPBCodedInputStreamReadUInt64(state);
+  if (size > kMaxFieldSize) {
+    // TODO(thomasvl): Maybe a different error code for this, but adding one is a breaking change
+    // so reuse an existing one.
+    RaiseException(GPBCodedInputStreamErrorInvalidSize, nil);
+  }
+  NSUInteger ns_size = (NSUInteger)size;
   CheckSize(state, size);
-  NSData *result = [[NSData alloc] initWithBytes:state->bytes + state->bufferPos length:size];
+  NSData *result = [[NSData alloc] initWithBytes:state->bytes + state->bufferPos length:ns_size];
   state->bufferPos += size;
   return result;
 }
 
 NSData *GPBCodedInputStreamReadRetainedBytesNoCopy(GPBCodedInputStreamState *state) {
-  int32_t size = ReadRawVarint32(state);
-  if (size < 0) return nil;
+  uint64_t size = GPBCodedInputStreamReadUInt64(state);
+  if (size > kMaxFieldSize) {
+    // TODO(thomasvl): Maybe a different error code for this, but adding one is a breaking change
+    // so reuse an existing one.
+    RaiseException(GPBCodedInputStreamErrorInvalidSize, nil);
+  }
+  NSUInteger ns_size = (NSUInteger)size;
   CheckSize(state, size);
   // Cast is safe because freeWhenDone is NO.
   NSData *result = [[NSData alloc] initWithBytesNoCopy:(void *)(state->bytes + state->bufferPos)
-                                                length:size
+                                                length:ns_size
                                           freeWhenDone:NO];
   state->bufferPos += size;
   return result;

objectivec/GPBMessage.m

@@ -2003,9 +2003,6 @@ static GPBUnknownFieldSet *GetOrMakeUnknownFields(GPBMessage *self) {
     return;
   }
   NSData *data = GPBCodedInputStreamReadRetainedBytesNoCopy(state);
-  if (data == nil) {
-    return;
-  }
   [self mergeFromData:data extensionRegistry:extensionRegistry];
   [data release];
 }

objectivec/Tests/GPBCodedInputStreamTests.m

@@ -28,6 +28,7 @@
 // (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
 // OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 
+#import <Foundation/Foundation.h>
 #import "GPBTestUtilities.h"
 
 #import "GPBCodedInputStream.h"
@@ -370,10 +371,23 @@
                                @"should throw a GPBCodedInputStreamException exception ");
 }
 
-- (void)testBytesWithNegativeSize {
-  NSData* data = bytes(0xFF, 0xFF, 0xFF, 0xFF, 0x0F);
+- (void)testBytesOver2GB {
+  NSData* data = bytes(0xFF, 0xFF, 0xFF, 0xFF, 0x0F, 0x01, 0x02, 0x03);  // don't need all the bytes
   GPBCodedInputStream* input = [GPBCodedInputStream streamWithData:data];
-  XCTAssertNil([input readBytes]);
+  @try {
+    __unused NSData* result = [input readBytes];
+    XCTFail(@"Should have thrown");
+  } @catch (NSException* anException) {
+    // Ensure the correct error within the exception.
+    XCTAssertTrue([anException isKindOfClass:[NSException class]]);
+    XCTAssertEqualObjects(anException.name, GPBCodedInputStreamException);
+    NSDictionary* userInfo = anException.userInfo;
+    XCTAssertNotNil(userInfo);
+    NSError* err = userInfo[GPBCodedInputStreamUnderlyingErrorKey];
+    XCTAssertNotNil(err);
+    XCTAssertEqualObjects(err.domain, GPBCodedInputStreamErrorDomain);
+    XCTAssertEqual(err.code, GPBCodedInputStreamErrorInvalidSize);
+  }
 }
 
 // Verifies fix for b/10315336.

objectivec/Tests/GPBMessageTests+Serialization.m

@@ -1266,12 +1266,17 @@
   XCTAssertEqual(error.code, GPBCodedInputStreamErrorRecursionDepthExceeded);
 }
 
-- (void)testParseDelimitedDataWithNegativeSize {
-  NSData *data = DataFromCStr("\xFF\xFF\xFF\xFF\x0F");
+- (void)testParseDelimitedDataOver2GB {
+  NSData *data = DataFromCStr("\xFF\xFF\xFF\xFF\x0F\x01\x02\0x3");  // Don't need all the bytes
   GPBCodedInputStream *input = [GPBCodedInputStream streamWithData:data];
   NSError *error;
-  [GPBMessage parseDelimitedFromCodedInputStream:input extensionRegistry:nil error:&error];
-  XCTAssertNil(error);
+  GPBMessage *result = [GPBMessage parseDelimitedFromCodedInputStream:input
+                                                    extensionRegistry:nil
+                                                                error:&error];
+  XCTAssertNil(result);
+  XCTAssertNotNil(error);
+  XCTAssertEqualObjects(error.domain, GPBCodedInputStreamErrorDomain);
+  XCTAssertEqual(error.code, GPBCodedInputStreamErrorInvalidSize);
 }
 
 #ifdef DEBUG