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zlib: fix windowBits validation to allow 0 for decompression mode #19686

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anandsuresh wants to merge 2 commits into from
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zlib: fix windowBits validation to allow 0 for decompression mode #19686

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zlib: fix windowBits validation to allow 0 for decompression mode
anandsuresh Mar 29, 2018
fda4044
zlib: code-review fixes
anandsuresh Mar 29, 2018
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17 changes: 14 additions & 3 deletions lib/zlib.js
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Original file line number Diff line number Diff line change
Expand Up @@ -251,9 +251,20 @@ function Zlib(opts, mode) {
opts.finishFlush, 'options.finishFlush',
Z_NO_FLUSH, Z_BLOCK, Z_FINISH);

windowBits = checkRangesOrGetDefault(
opts.windowBits, 'options.windowBits',
Z_MIN_WINDOWBITS, Z_MAX_WINDOWBITS, Z_DEFAULT_WINDOWBITS);
// windowBits is special. On the compression side, 0 is an invalid value.
// But on the decompression side, a value of 0 for windowBits tells zlib
// to extract the value from the headers of the compressed stream.
if (opts.windowBits === 0 &&

@addaleax addaleax Mar 29, 2018

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We may actually want to also capture undefined here, so that when decompressing we always go with the header-provided value (instead of the safe maximum) for lower memory usage.

@anandsuresh anandsuresh Mar 29, 2018

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excellent idea! How about opts.windowBits == null || opts.windowBits === 0?

@addaleax addaleax Mar 29, 2018

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@anandsuresh Sounds reasonable to me!

(mode === INFLATE ||
mode === GUNZIP ||
mode === INFLATERAW ||

@addaleax addaleax Mar 29, 2018

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INFLATERAW means that there is no header, so I think we'd want to drop that case?

@anandsuresh anandsuresh Mar 29, 2018

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Sure. I picked the list from

node/src/node_zlib.cc

Lines 541 to 544 in 22f4a35

case INFLATE:
case GUNZIP:
case INFLATERAW:
case UNZIP:
, since they all end up calling inflateInit2(). Will remove it from the list.

mode === UNZIP)) {
windowBits = 0

@addaleax addaleax Mar 29, 2018

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Can you run make lint? It should complain about the lack of a semicolon here ;)

@anandsuresh anandsuresh Mar 29, 2018

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whoops. I'm spoiled by standardjs! Will fix.

} else {
windowBits = checkRangesOrGetDefault(
opts.windowBits, 'options.windowBits',
Z_MIN_WINDOWBITS, Z_MAX_WINDOWBITS, Z_DEFAULT_WINDOWBITS);
}

level = checkRangesOrGetDefault(
opts.level, 'options.level',
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