Add support for gzipped request body previews (#54963)

Summary:
Pull Request resolved: #54963

**Context**

Follows D89659683, addressing a coverage gap in processing network request body previews when the payload is gzipped.

**This diff**

- Updates `convertRequestBodyToStringTruncated` to attempt gzip decompression based on `"Content-Encoding"` header.
- Adds new `RCTDecompressGzipData` util in `RCTUtils`.
- Also reduce the maximum size of request body previews from 1MB to 512KB.

Changelog: [Internal]

Changelog (0.83.x): [iOS][Fixed] - React Native DevTools: Add support for gzipped request body previews.

Reviewed By: cipolleschi

Differential Revision: D89659684

fbshipit-source-id: 513143cc683d003ae6f1fde69f75e9ca51181771

Author: huntie

packages/react-native/Libraries/Network/RCTInspectorNetworkReporter.mm

@@ -10,6 +10,7 @@
 #import "RCTNetworkConversions.h"
 
 #import <React/RCTLog.h>
+#import <React/RCTUtils.h>
 #import <react/networking/NetworkReporter.h>
 
 using namespace facebook::react;
@@ -28,13 +29,22 @@ Headers convertNSDictionaryToHeaders(const NSDictionary<NSString *, NSString *>
 
 std::string convertRequestBodyToStringTruncated(NSURLRequest *request)
 {
-  const NSUInteger maxBodySize = 1024 * 1024; // 1MB
+  const NSUInteger maxBodySize = 512 * 1024; // 512KB
   NSData *bodyData = request.HTTPBody;
 
   if (bodyData == nil || bodyData.length == 0) {
     return "";
   }
 
+  // Decompress if gzip-encoded (up to maxBodySize)
+  NSString *contentEncoding = [request valueForHTTPHeaderField:@"Content-Encoding"];
+  if ([contentEncoding isEqualToString:@"gzip"]) {
+    NSData *decompressedData = RCTDecompressGzipData(bodyData, maxBodySize);
+    if (decompressedData != nil) {
+      bodyData = decompressedData;
+    }
+  }
+
   auto bodyLength = bodyData.length;
   auto bytesToRead = std::min(bodyLength, maxBodySize);
   NSData *truncatedData = [bodyData subdataWithRange:NSMakeRange(0, bytesToRead)];

packages/react-native/React/Base/RCTUtils.h

@@ -132,6 +132,10 @@ RCT_EXTERN NSURL *RCTDataURL(NSString *mimeType, NSData *data);
 // Gzip functionality - compression level in range 0 - 1 (-1 for default)
 RCT_EXTERN NSData *__nullable RCTGzipData(NSData *__nullable data, float level);
 
+// Gzip decompression - maxDecompressedSize of 0 means no limit, returns nil if
+// limit exceeded or decompression fails
+RCT_EXTERN NSData *__nullable RCTDecompressGzipData(NSData *__nullable data, NSUInteger maxDecompressedSize);
+
 // Returns the relative path within the main bundle for an absolute URL
 // (or nil, if the URL does not specify a path within the main bundle)
 RCT_EXTERN NSString *__nullable RCTBundlePathForURL(NSURL *__nullable URL);

packages/react-native/React/Base/RCTUtils.mm

@@ -713,6 +713,8 @@ BOOL RCTIsGzippedData(NSData *__nullable data)
   return (data.length >= 2 && bytes[0] == 0x1f && bytes[1] == 0x8b);
 }
 
+static const NSUInteger RCTGZipChunkSize = 16384;
+
 NSData *__nullable RCTGzipData(NSData *__nullable input, float level)
 {
   if (input.length == 0 || RCTIsGzippedData(input)) {
@@ -739,8 +741,6 @@ BOOL RCTIsGzippedData(NSData *__nullable data)
   stream.total_out = 0;
   stream.avail_out = 0;
 
-  static const NSUInteger RCTGZipChunkSize = 16384;
-
   NSMutableData *output = nil;
   int compression = (level < 0.0f) ? Z_DEFAULT_COMPRESSION : (int)(roundf(level * 9));
   if (deflateInit2(&stream, compression, Z_DEFLATED, 31, 8, Z_DEFAULT_STRATEGY) == Z_OK) {
@@ -762,6 +762,63 @@ BOOL RCTIsGzippedData(NSData *__nullable data)
   return output;
 }
 
+NSData *__nullable RCTDecompressGzipData(NSData *__nullable data, NSUInteger maxDecompressedSize)
+{
+  if (data.length == 0 || !RCTIsGzippedData(data)) {
+    return data;
+  }
+
+  void *libz = dlopen("/usr/lib/libz.dylib", RTLD_LAZY);
+
+  using InflateInit2_ = int (*)(z_streamp, int, const char *, int);
+  InflateInit2_ inflateInit2_ = (InflateInit2_)dlsym(libz, "inflateInit2_");
+
+  using Inflate = int (*)(z_streamp, int);
+  Inflate inflate = (Inflate)dlsym(libz, "inflate");
+
+  using InflateEnd = int (*)(z_streamp);
+  InflateEnd inflateEnd = (InflateEnd)dlsym(libz, "inflateEnd");
+
+  z_stream stream;
+  stream.zalloc = Z_NULL;
+  stream.zfree = Z_NULL;
+  stream.opaque = Z_NULL;
+  stream.avail_in = (uint)data.length;
+  stream.next_in = (Bytef *)data.bytes;
+  stream.total_out = 0;
+  stream.avail_out = 0;
+
+  NSMutableData *output = nil;
+  // Use 31 for windowBits to enable gzip decoding (15 + 16)
+  if (inflateInit2(&stream, 31) == Z_OK) {
+    output = [NSMutableData dataWithLength:RCTGZipChunkSize];
+    int status = Z_OK;
+    while (status == Z_OK) {
+      if (stream.total_out >= output.length) {
+        output.length += RCTGZipChunkSize;
+      }
+      if (maxDecompressedSize > 0 && stream.total_out >= maxDecompressedSize) {
+        inflateEnd(&stream);
+        dlclose(libz);
+        return nil;
+      }
+      stream.next_out = (uint8_t *)output.mutableBytes + stream.total_out;
+      stream.avail_out = (uInt)(output.length - stream.total_out);
+      status = inflate(&stream, Z_SYNC_FLUSH);
+    }
+    inflateEnd(&stream);
+    if (status != Z_STREAM_END) {
+      dlclose(libz);
+      return nil;
+    }
+    output.length = stream.total_out;
+  }
+
+  dlclose(libz);
+
+  return output;
+}
+
 static NSString *RCTRelativePathForURL(NSString *basePath, NSURL *__nullable URL)
 {
   if (!URL.fileURL) {