zlib: prevent uncaught exception in zlibBuffer

If the accumulation of data for the final Buffer is greater than
kMaxLength it will throw an un-catchable RangeError. Instead now pass
the generated error to the callback.

PR-URL: #1811
Reviewed-By: Fedor Indutny <[email protected]>
Reviewed-By: Trevor Norris <[email protected]>

Author: targos

lib/zlib.js

@@ -5,6 +5,9 @@ const Transform = require('_stream_transform');
 const binding = process.binding('zlib');
 const util = require('util');
 const assert = require('assert').ok;
+const kMaxLength = process.binding('smalloc').kMaxLength;
+const kRangeErrorMessage = 'Cannot create final Buffer. ' +
+    'It would be larger than 0x' + kMaxLength.toString(16) + ' bytes.';
 
 // zlib doesn't provide these, so kludge them in following the same
 // const naming scheme zlib uses.
@@ -210,10 +213,18 @@ function zlibBuffer(engine, buffer, callback) {
   }
 
   function onEnd() {
-    var buf = Buffer.concat(buffers, nread);
+    var buf;
+    var err = null;
+
+    if (nread >= kMaxLength) {
+      err = new RangeError(kRangeErrorMessage);
+    } else {
+      buf = Buffer.concat(buffers, nread);
+    }
+
     buffers = [];
-    callback(null, buf);
     engine.close();
+    callback(err, buf);
   }
 }
 
@@ -524,6 +535,11 @@ Zlib.prototype._processChunk = function(chunk, flushFlag, cb) {
       throw error;
     }
 
+    if (nread >= kMaxLength) {
+      this.close();
+      throw new RangeError(kRangeErrorMessage);
+    }
+
     var buf = Buffer.concat(buffers, nread);
     this.close();
 

test/parallel/test-regress-GH-io-1811.js

@@ -0,0 +1,22 @@
+'use strict';
+
+const assert = require('assert');
+
+// Change kMaxLength for zlib to trigger the error
+// without having to allocate 1GB of buffers
+const smalloc = process.binding('smalloc');
+smalloc.kMaxLength = 128;
+const zlib = require('zlib');
+smalloc.kMaxLength = 0x3fffffff;
+
+const encoded = new Buffer('H4sIAAAAAAAAA0tMHFgAAIw2K/GAAAAA', 'base64');
+
+// Async
+zlib.gunzip(encoded, function(err) {
+  assert.ok(err instanceof RangeError);
+});
+
+// Sync
+assert.throws(function() {
+  zlib.gunzipSync(encoded);
+}, RangeError);