zlib: reject trailing gzip members in web streams

Pass the existing rejectGarbageAfterEnd option through to the native
zlib context and skip gunzip's concatenated-member loop when it is set.
This lets DecompressionStream reject a second gzip member as trailing
input while preserving default zlib gunzip behavior.

Also make the sync zlib path honor rejectGarbageAfterEnd when native
decompression leaves unused input, covering Brotli as well.

Fixes: #58247

Signed-off-by: Filip Skokan <panva.ip@gmail.com>
PR-URL: #64023
Fixes: #58247
Reviewed-By: Anna Henningsen <anna@addaleax.net>

Author: panva

lib/zlib.js

@@ -472,6 +472,11 @@ function processChunkSync(self, chunk, flushFlag) {
     }
   }
 
+  if (availInAfter > 0 && self._rejectGarbageAfterEnd) {
+    _close(self);
+    throw new ERR_TRAILING_JUNK_AFTER_STREAM_END();
+  }
+
   self.bytesWritten = inputRead;
   _close(self);
 
@@ -678,7 +683,8 @@ function Zlib(opts, mode) {
               strategy,
               this._writeState,
               processCallback,
-              dictionary);
+              dictionary,
+              opts?.rejectGarbageAfterEnd === true);
 
   ZlibBase.call(this, opts, mode, handle, zlibDefaultOpts);
 

src/node_zlib.cc

@@ -196,6 +196,7 @@ class ZlibContext final : public MemoryRetainer {
             int window_bits,
             int mem_level,
             int strategy,
+            bool reject_garbage_after_end,
             std::vector<unsigned char>&& dictionary);
   CompressionError SetParams(int level, int strategy);
 
@@ -223,6 +224,7 @@ class ZlibContext final : public MemoryRetainer {
   node_zlib_mode mode_ = NONE;
   int strategy_ = 0;
   int window_bits_ = 0;
+  bool reject_garbage_after_end_ = false;
   unsigned int gzip_id_bytes_read_ = 0;
   std::vector<unsigned char> dictionary_;
 
@@ -753,9 +755,10 @@ class ZlibStream final : public CompressionStream<ZlibContext> {
           "a version of npm (> 5.5.1 or < 5.4.0) or node-tar (> 4.0.1) "
           "that is compatible with Node.js 9 and above.\n");
     }
-    CHECK(args.Length() == 7 &&
-      "init(windowBits, level, memLevel, strategy, writeResult, writeCallback,"
-      " dictionary)");
+    CHECK((args.Length() == 7 || args.Length() == 8) &&
+          "init(windowBits, level, memLevel, strategy, writeResult, "
+          "writeCallback,"
+          " dictionary[, rejectGarbageAfterEnd])");
 
     ZlibStream* wrap;
     ASSIGN_OR_RETURN_UNWRAP(&wrap, args.This());
@@ -795,10 +798,20 @@ class ZlibStream final : public CompressionStream<ZlibContext> {
           data + Buffer::Length(args[6]));
     }
 
+    bool reject_garbage_after_end = false;
+    if (args.Length() == 8) {
+      CHECK(args[7]->IsBoolean());
+      reject_garbage_after_end = args[7]->IsTrue();
+    }
+
     wrap->InitStream(write_result, write_js_callback);
 
     AllocScope alloc_scope(wrap);
-    wrap->context()->Init(level, window_bits, mem_level, strategy,
+    wrap->context()->Init(level,
+                          window_bits,
+                          mem_level,
+                          strategy,
+                          reject_garbage_after_end,
                           std::move(dictionary));
   }
 
@@ -1128,10 +1141,8 @@ void ZlibContext::DoThreadPoolWork() {
         }
       }
 
-      while (strm_.avail_in > 0 &&
-             mode_ == GUNZIP &&
-             err_ == Z_STREAM_END &&
-             strm_.next_in[0] != 0x00) {
+      while (strm_.avail_in > 0 && mode_ == GUNZIP && err_ == Z_STREAM_END &&
+             !reject_garbage_after_end_ && strm_.next_in[0] != 0x00) {
         // Bytes remain in input buffer. Perhaps this is another compressed
         // member in the same archive, or just trailing garbage.
         // Trailing zero bytes are okay, though, since they are frequently
@@ -1230,9 +1241,12 @@ CompressionError ZlibContext::ResetStream() {
   return SetDictionary();
 }
 
-void ZlibContext::Init(
-    int level, int window_bits, int mem_level, int strategy,
-    std::vector<unsigned char>&& dictionary) {
+void ZlibContext::Init(int level,
+                       int window_bits,
+                       int mem_level,
+                       int strategy,
+                       bool reject_garbage_after_end,
+                       std::vector<unsigned char>&& dictionary) {
   // Set allocation functions
   strm_.zalloc = CompressionStreamMemoryOwner::AllocForZlib;
   strm_.zfree = CompressionStreamMemoryOwner::FreeForZlib;
@@ -1263,6 +1277,7 @@ void ZlibContext::Init(
   window_bits_ = window_bits;
   mem_level_ = mem_level;
   strategy_ = strategy;
+  reject_garbage_after_end_ = reject_garbage_after_end;
 
   flush_ = Z_NO_FLUSH;
 

test/parallel/test-zlib-type-error.js

@@ -2,36 +2,67 @@
 require('../common');
 const assert = require('assert');
 const test = require('node:test');
+const zlib = require('zlib');
 const { DecompressionStream } = require('stream/web');
 
-test('DecompressStream deflat emits error on trailing data', async () => {
+async function assertDecompressionStreamRejects(format, chunks) {
+  await assert.rejects(
+    Array.fromAsync(
+      new Blob(chunks).stream().pipeThrough(new DecompressionStream(format))
+    ),
+    { name: 'TypeError' },
+  );
+}
+
+test('DecompressionStream deflate emits TypeError on trailing data', async () => {
   const valid = new Uint8Array([120, 156, 75, 4, 0, 0, 98, 0, 98]); // deflate('a')
   const empty = new Uint8Array(1);
   const invalid = new Uint8Array([...valid, ...empty]);
   const double = new Uint8Array([...valid, ...valid]);
 
-  for (const chunk of [[invalid], [valid, empty], [valid, valid], [valid, double]]) {
-    await assert.rejects(
-      Array.fromAsync(
-        new Blob([chunk]).stream().pipeThrough(new DecompressionStream('deflate'))
-      ),
-      { name: 'TypeError' },
-    );
+  for (const chunks of [[invalid], [valid, empty], [valid, valid], [double]]) {
+    await assertDecompressionStreamRejects('deflate', chunks);
   }
 });
 
-test('DecompressStream gzip emits error on trailing data', async () => {
+test('DecompressionStream gzip emits TypeError on trailing data', async () => {
   const valid = new Uint8Array([31, 139, 8, 0, 0, 0, 0, 0, 0, 19, 75, 4,
                                 0, 67, 190, 183, 232, 1, 0, 0, 0]); // gzip('a')
   const empty = new Uint8Array(1);
   const invalid = new Uint8Array([...valid, ...empty]);
   const double = new Uint8Array([...valid, ...valid]);
-  for (const chunk of [[invalid], [valid, empty], [valid, valid], [double]]) {
-    await assert.rejects(
-      Array.fromAsync(
-        new Blob([chunk]).stream().pipeThrough(new DecompressionStream('gzip'))
-      ),
-      { name: 'TypeError' },
-    );
+  for (const chunks of [[invalid], [valid, empty], [valid, valid], [double]]) {
+    await assertDecompressionStreamRejects('gzip', chunks);
+  }
+});
+
+test('DecompressionStream brotli emits TypeError on trailing data', async () => {
+  const valid = zlib.brotliCompressSync(Buffer.from('a'));
+  const empty = new Uint8Array(1);
+  const invalid = new Uint8Array([...valid, ...empty]);
+  const double = new Uint8Array([...valid, ...valid]);
+  for (const chunks of [[invalid], [valid, empty], [valid, valid], [double]]) {
+    await assertDecompressionStreamRejects('brotli', chunks);
   }
 });
+
+test('zlib sync decompression honors rejectGarbageAfterEnd', () => {
+  const valid = new Uint8Array([31, 139, 8, 0, 0, 0, 0, 0, 0, 19, 75, 4,
+                                0, 67, 190, 183, 232, 1, 0, 0, 0]); // gzip('a')
+  const double = new Uint8Array([...valid, ...valid]);
+
+  assert.deepStrictEqual(zlib.gunzipSync(double), Buffer.from('aa'));
+  assert.throws(
+    () => zlib.gunzipSync(double, { rejectGarbageAfterEnd: true }),
+    { code: 'ERR_TRAILING_JUNK_AFTER_STREAM_END', name: 'TypeError' },
+  );
+
+  const brotli = zlib.brotliCompressSync(Buffer.from('a'));
+  const brotliDouble = Buffer.concat([brotli, brotli]);
+
+  assert.deepStrictEqual(zlib.brotliDecompressSync(brotliDouble), Buffer.from('a'));
+  assert.throws(
+    () => zlib.brotliDecompressSync(brotliDouble, { rejectGarbageAfterEnd: true }),
+    { code: 'ERR_TRAILING_JUNK_AFTER_STREAM_END', name: 'TypeError' },
+  );
+});