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zlib: fix decompression of empty data streams
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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.

PR-URL: #17042
Fixes: #17041
Refs: #13322
Reviewed-By: Ben Noordhuis <info@bnoordhuis.nl>
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Evan Lucas <evanlucas@me.com>
Reviewed-By: Matteo Collina <matteo.collina@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>
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addaleax authored and MylesBorins committed Dec 11, 2017
1 parent 035a24e commit fa01fe6
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5 changes: 5 additions & 0 deletions lib/zlib.js
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);
} 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
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}`);
}
})();

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