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zlib: Fix handling of gzip magic bytes mid-file
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Only treat the gzip magic bytes, when encountered within the file
after reading a single block, as the start of a new member when
the previous member has ended.

Add test files that reliably reproduce #5852. The gzipped file
in test/fixtures/pseudo-multimember-gzip.gz contains the gzip
magic bytes exactly at the position that node encounters after having
read a single block, leading it to believe that a new data
member is starting.

Fixes: #5852
PR-URL: #5863
Reviewed-By: Ben Noordhuis <info@bnoordhuis.nl>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Jeremiah Senkpiel <fishrock123@rocketmail.com>
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addaleax authored and Fishrock123 committed Mar 23, 2016
1 parent 7d73e60 commit 0b3936b
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Showing 4 changed files with 24 additions and 1 deletion.
3 changes: 2 additions & 1 deletion src/node_zlib.cc
Original file line number Diff line number Diff line change
Expand Up @@ -258,7 +258,8 @@ class ZCtx : public AsyncWrap {
}
}
while (ctx->strm_.avail_in >= GZIP_MIN_HEADER_SIZE &&
ctx->mode_ == GUNZIP) {
ctx->mode_ == GUNZIP &&
ctx->err_ == Z_STREAM_END) {
// Bytes remain in input buffer. Perhaps this is another compressed
// member in the same archive, or just trailing garbage.
// Check the header to find out.
Expand Down
Binary file added test/fixtures/pseudo-multimember-gzip.gz
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Binary file added test/fixtures/pseudo-multimember-gzip.z
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22 changes: 22 additions & 0 deletions test/parallel/test-zlib-from-concatenated-gzip.js
Original file line number Diff line number Diff line change
Expand Up @@ -4,6 +4,8 @@
const common = require('../common');
const assert = require('assert');
const zlib = require('zlib');
const path = require('path');
const fs = require('fs');

const data = Buffer.concat([
zlib.gzipSync('abc'),
Expand All @@ -16,3 +18,23 @@ zlib.gunzip(data, common.mustCall((err, result) => {
assert.ifError(err);
assert.equal(result, 'abcdef', 'result should match original string');
}));

// files that have the "right" magic bytes for starting a new gzip member
// in the middle of themselves, even if they are part of a single
// regularly compressed member
const pmmFileZlib = path.join(common.fixturesDir, 'pseudo-multimember-gzip.z');
const pmmFileGz = path.join(common.fixturesDir, 'pseudo-multimember-gzip.gz');

const pmmExpected = zlib.inflateSync(fs.readFileSync(pmmFileZlib));
const pmmResultBuffers = [];

fs.createReadStream(pmmFileGz)
.pipe(zlib.createGunzip())
.on('error', (err) => {
assert.ifError(err);
})
.on('data', (data) => pmmResultBuffers.push(data))
.on('finish', common.mustCall(() => {
assert.deepStrictEqual(Buffer.concat(pmmResultBuffers), pmmExpected,
'result should match original random garbage');
}));

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