Skip to content

zlib: fix decompression of empty data streams #17042

New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Closed
addaleax wants to merge 1 commit into from
Closed

zlib: fix decompression of empty data streams #17042

Show file tree
Hide file tree
Changes from all commits
Commits
Show all changes
1 commit
Select commit
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
zlib: fix decompression of empty data streams 
add4b0a made the assumption that compressed data
would never lead to an empty decompressed stream.

Fix that by explicitly checking the number of read bytes.

Fixes: #17041
Refs: #13322
  • Loading branch information
@addaleax
addaleax committed Nov 15, 2017
commit 74afe5cfea875863862368f6af0e85a031e78890
5 changes: 5 additions & 0 deletions lib/zlib.js
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -95,6 +95,8 @@ function zlibBufferOnEnd() {
var err;
if (this.nread >= kMaxLength) {
err = new errors.RangeError('ERR_BUFFER_TOO_LARGE');
} else if (this.nread === 0) {
buf = Buffer.alloc(0);
Copy link
Copy Markdown
Member

@mcollina mcollina Nov 16, 2017

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

I don't know if there is any performance penalty to use Buffer.alloc(0) vs Buffer.allocUnsafe(0). However, as it's 0 I would use allocUnsafe.

Copy link
Copy Markdown
Member Author

@addaleax addaleax Nov 16, 2017

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

alloc() has what is essentially a fast path for 0, allocUnsafe() doesn’t.

Copy link
Copy Markdown
Member

@mcollina mcollina Nov 16, 2017

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

This is very interesting. thanks!

Copy link
Copy Markdown
Member Author

@addaleax addaleax Nov 16, 2017

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

I mean, I don’t think it’s that way on purpose. :) It just happens to align nicely with how we can use basically new Uint8Array(n) for the Buffer.alloc() fast path, whereas Buffer.allocUnsafe() needs a bit of setup.

} else {
var bufs = this.buffers;
buf = (bufs.length === 1 ? bufs[0] : Buffer.concat(bufs, this.nread));
Expand Down Expand Up @@ -485,6 +487,9 @@ function processChunkSync(self, chunk, flushFlag) {

_close(self);

if (nread === 0)
return Buffer.alloc(0);

return (buffers.length === 1 ? buffers[0] : Buffer.concat(buffers, nread));
}

Expand Down
26 changes: 26 additions & 0 deletions test/parallel/test-zlib-empty-buffer.js
View file
Open in desktop
Original file line number Diff line number Diff line change
@@ -0,0 +1,26 @@
'use strict';
const common = require('../common');
const zlib = require('zlib');
const { inspect, promisify } = require('util');
const assert = require('assert');
const emptyBuffer = new Buffer(0);

common.crashOnUnhandledRejection();

(async function() {
for (const [ compress, decompress, method ] of [
[ zlib.deflateRawSync, zlib.inflateRawSync, 'raw sync' ],
[ zlib.deflateSync, zlib.inflateSync, 'deflate sync' ],
[ zlib.gzipSync, zlib.gunzipSync, 'gzip sync' ],
[ promisify(zlib.deflateRaw), promisify(zlib.inflateRaw), 'raw' ],
[ promisify(zlib.deflate), promisify(zlib.inflate), 'deflate' ],
[ promisify(zlib.gzip), promisify(zlib.gunzip), 'gzip' ]
]) {
const compressed = await compress(emptyBuffer);
const decompressed = await decompress(compressed);
assert.deepStrictEqual(
emptyBuffer, decompressed,
`Expected ${inspect(compressed)} to match ${inspect(decompressed)} ` +
`to match for ${method}`);
}
})();