On Wed, 10 Jan 2024 13:39:52 GMT, Eirik Bjørsnøs <[email protected]> wrote:
>> ZipInputStream.readEnd currently assumes a Zip64 data descriptor if the
>> number of compressed or uncompressed bytes read from the inflater is larger
>> than the Zip64 magic value.
>>
>> While the ZIP format mandates that the data descriptor `SHOULD be stored in
>> ZIP64 format (as 8 byte values) when a file's size exceeds 0xFFFFFFFF`, it
>> also states that `ZIP64 format MAY be used regardless of the size of a
>> file`. For such small entries, the above assumption does not hold.
>>
>> This PR augments ZipInputStream.readEnd to also assume 8-byte sizes if the
>> ZipEntry includes a Zip64 extra information field AND the 'compressed size'
>> and 'uncompressed size' have the expected Zip64 "magic" value 0xFFFFFFFF.
>> This brings ZipInputStream into alignment with the APPNOTE format spec:
>>
>>
>> When extracting, if the zip64 extended information extra
>> field is present for the file the compressed and
>> uncompressed sizes will be 8 byte values.
>>
>>
>> While small Zip64 files with 8-byte data descriptors are not commonly found
>> in the wild, it is possible to create one using the Info-ZIP command line
>> `-fd` flag:
>>
>> `echo hello | zip -fd > hello.zip`
>>
>> The PR also adds a test verifying that such a small Zip64 file can be parsed
>> by ZipInputStream.
>
> Eirik Bjørsnøs has updated the pull request incrementally with two additional
> commits since the last revision:
>
> - Remove trailing whitespace
> - Remove trailing whitespace
src/java.base/share/classes/java/util/zip/ZipInputStream.java line 664:
> 662:
> 663: // The LOC's 'compressed size' and 'uncompressed size' must both
> be marked for Zip64
> 664: if (csize != ZIP64_MAGICVAL || size != ZIP64_MAGICVAL) {
The spec for this says different. It says:
>
> 4.4.4 general purpose bit flag:
> ...
> Bit 3: If this bit is set, the fields crc-32, compressed size and
> uncompressed size are set to zero in the local header. The correct values
> are put in the data descriptor immediately following the compressed data.
So it expects the value zero for the compressed/uncompressed sizes in the LOC
when the data descriptor bit is set.
-------------
PR Review Comment: https://git.openjdk.org/jdk/pull/12524#discussion_r1453460177
