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zlib: add support for concatenated members
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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: #4306
PR-URL: #5120
Reviewed-By: Ben Noordhuis <info@bnoordhuis.nl>
Reviewed-By: James M Snell <jasnell@gmail.com>
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kthelgason authored and bnoordhuis committed Mar 15, 2016
1 parent 3b20941 commit f380db2
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18 changes: 18 additions & 0 deletions src/node_zlib.cc
Original file line number Diff line number Diff line change
Expand Up @@ -41,6 +41,9 @@ enum node_zlib_mode {
UNZIP
};

#define GZIP_HEADER_ID1 0x1f
#define GZIP_HEADER_ID2 0x8b
#define GZIP_MIN_HEADER_SIZE 10

void InitZlib(v8::Local<v8::Object> target);

Expand Down Expand Up @@ -254,6 +257,19 @@ class ZCtx : public AsyncWrap {
ctx->err_ = Z_NEED_DICT;
}
}
while (ctx->strm_.avail_in >= GZIP_MIN_HEADER_SIZE &&
ctx->mode_ == GUNZIP) {
// 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.
if (ctx->strm_.next_in[0] != GZIP_HEADER_ID1 ||
ctx->strm_.next_in[1] != GZIP_HEADER_ID2) {
// Not a valid gzip member
break;
}
Reset(ctx);
ctx->err_ = inflate(&ctx->strm_, ctx->flush_);
}
break;
default:
CHECK(0 && "wtf?");
Expand Down Expand Up @@ -524,10 +540,12 @@ class ZCtx : public AsyncWrap {
switch (ctx->mode_) {
case DEFLATE:
case DEFLATERAW:
case GZIP:
ctx->err_ = deflateReset(&ctx->strm_);
break;
case INFLATE:
case INFLATERAW:
case GUNZIP:
ctx->err_ = inflateReset(&ctx->strm_);
break;
default:
Expand Down
18 changes: 18 additions & 0 deletions test/parallel/test-zlib-from-concatenated-gzip.js
Original file line number Diff line number Diff line change
@@ -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');
}));
50 changes: 50 additions & 0 deletions test/parallel/test-zlib-from-gzip-with-trailing-garbage.js
Original file line number Diff line number Diff line change
@@ -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');
}));

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