zlib: add support for concatenated members

According to the spec gzipped archives can contain more than one
compressed member. Previously Node's gzip implementation would only
unzip the first member and throw away the rest of the compressed data.
Issue #4306 is an example of this occurring in daily use.

Fixes: https://github.com/nodejs/node/issues/4306
PR-URL: https://github.com/nodejs/node/pull/5120
Reviewed-By: Ben Noordhuis <info@bnoordhuis.nl>
Reviewed-By: James M Snell <jasnell@gmail.com>

2 files changed, 68 insertions, 0 deletions

diff --git a/test/parallel/test-zlib-from-concatenated-gzip.js b/test/parallel/test-zlib-from-concatenated-gzip.js
new file mode 100644
index 0000000000..9bee905b33
--- /dev/null
+++ b/test/parallel/test-zlib-from-concatenated-gzip.js
@@ -0,0 +1,18 @@
+'use strict';
+// Test unzipping a gzip file that contains multiple concatenated "members"
+
+const common = require('../common');
+const assert = require('assert');
+const zlib = require('zlib');
+
+const data = Buffer.concat([
+  zlib.gzipSync('abc'),
+  zlib.gzipSync('def')
+]);
+
+assert.equal(zlib.gunzipSync(data).toString(), 'abcdef');
+
+zlib.gunzip(data, common.mustCall((err, result) => {
+  assert.ifError(err);
+  assert.equal(result, 'abcdef', 'result should match original string');
+}));
diff --git a/test/parallel/test-zlib-from-gzip-with-trailing-garbage.js b/test/parallel/test-zlib-from-gzip-with-trailing-garbage.js
new file mode 100644
index 0000000000..e5ec42544a
--- /dev/null
+++ b/test/parallel/test-zlib-from-gzip-with-trailing-garbage.js
@@ -0,0 +1,50 @@
+'use strict';
+// test unzipping a gzip file that has trailing garbage
+
+const common = require('../common');
+const assert = require('assert');
+const zlib = require('zlib');
+
+// should ignore trailing null-bytes
+let data = Buffer.concat([
+  zlib.gzipSync('abc'),
+  zlib.gzipSync('def'),
+  Buffer(10).fill(0)
+]);
+
+assert.equal(zlib.gunzipSync(data).toString(), 'abcdef');
+
+zlib.gunzip(data, common.mustCall((err, result) => {
+  assert.ifError(err);
+  assert.equal(result, 'abcdef', 'result should match original string');
+}));
+
+// if the trailing garbage happens to look like a gzip header, it should
+// throw an error.
+data = Buffer.concat([
+  zlib.gzipSync('abc'),
+  zlib.gzipSync('def'),
+  Buffer([0x1f, 0x8b, 0xff, 0xff]),
+  Buffer(10).fill(0)
+]);
+
+assert.throws(() => zlib.gunzipSync(data));
+
+zlib.gunzip(data, common.mustCall((err, result) => {
+  assert(err);
+}));
+
+// In this case the trailing junk is too short to be a gzip segment
+// So we ignore it and decompression succeeds.
+data = Buffer.concat([
+  zlib.gzipSync('abc'),
+  zlib.gzipSync('def'),
+  Buffer([0x1f, 0x8b, 0xff, 0xff])
+]);
+
+assert.equal(zlib.gunzipSync(data).toString(), 'abcdef');
+
+zlib.gunzip(data, common.mustCall((err, result) => {
+  assert.ifError(err);
+  assert.equal(result, 'abcdef', 'result should match original string');
+}));