[PING] PoC for JDK-4347142: Need method to set Password protection to Zip entries

Xueming Shen xueming.shen at oracle.com
Tue Jan 5 22:10:14 UTC 2016


I'm not convinced that the ZipCryption is a public interface we'd like to expose,
at least for now, given the proprietary nature of the "strong encryption" defined

As I said in my previous email, it might be desired to hide the "passwd/encryption"
support for the "traditional zip encryption" as an implementation detail.

Looking at the existing methods that deal with "entry" in ZipFile, ZipInputStream
and ZipOutputStream,

ZipFile.getInputStream(ZipEntry e);
ZipOutputStream.putNextEntry(ZipEntry e);

it appears that instead of adding "password" specific method to these classes
directly, it might be more appropriate to extend the ZipEntry class for such
"password" functionality. For example, with a pair of new methods

boolean ZipEntry.isTraditionalEncryption().
void ZipEntry.setTraditionalEncryption(String password);

The encryption support should/can be added naturally/smoothly with
ZipFile.getInputStream(e), ZipInputstream and ZipOutputStream.putNextEntry(e),
with no extra new method in these two classes. The implementation checks
the flag (bit0, no bit 6) first and then verifies the password, as an implementation

For ZipFile and ZipInputStream, we can add note to the api doc to force the
invoker to check if the returned ZipEntry indicates it's an encrypted entry. If yes,
it must to set the appropriate password to the returned ZipEntry via
ZipEntry.setTraditionalEncryption(password); before reading any byte from the
input stream.

Again, we should not have any "encryption" related public field/method in
DeflaterOutputStream/InflaterInputStream. Ideally these two classes really should
not be aware of "encryption" at all.


On 01/04/2016 06:26 AM, KUBOTA Yuji wrote:
> Hi Sherman and all,
> Happy new year to everyone!
> Please let know your feedback about this proposal. :-)
> Thanks,
> Yuji
> 2015-12-21 22:38 GMT+09:00 KUBOTA Yuji<kubota.yuji at gmail.com>:
>> Hi Sherman,
>> 2015-12-20 16:35 GMT+09:00 Xueming Shen<xueming.shen at oracle.com>:
>>> It is no longer necessary to touch the native code (zip_util.c/h) after the
>>> native ZipFile implementation has been moved up to the java level. Those
>>> native code are for vm access only now, which I dont think care about the
>>> password support at all.
>> Thanks for your information. We do not take care the native.
>> I discussed with Yasumasa, and our thought is as below.
>>> (1) what's the benefit of exposing the public interface ZipCryption? the real
>>> question is whether or not this interface is good enough for other encryption
>>> implementation to plugin their implementation to support the ZipFile/Input/
>>> OutputStream to their encryption spec.
>> We aimed that the public interface ZipCryption supports the
>> extensibillity for other encrypt engine. The JDK core libs developers
>> have to implementation ZipyCryption only. If not provide, the JDK
>> developers must implement ZipStream/Entry by JDK API to design the
>> data structure of entry.
>> If you want to use binary key data such as PKI, you can implement new
>> encrypt/decrypt engine by ZipCryption interface.
>> So we think we should provide this interface to be clearly how to
>> implement a new engine, e.g., cipher algorithm, cipher strength and
>> converting the header, etc.
>>> (2) it seems like it might be possible to hide most of the implementation
>>> and only expose the "String password" (instead of the ZipCryption) as the
>>> public interface to support the "traditional" encryption. This depends on the
>>> result of (1) though.
>> Thanks for your clues. We think the string password at first. However,
>> we should also create a new binary interface given we support PKI in
>> the future.
>>> (3) I'm concerned of pushing ZipCryption into InflaterInputStream/DeflaterOutputStream.
>>> It might be worth considering to replace the ZipCryption implementation with
>>> a pair of FilterOutput/InputStream. It would be easy and reasonable to use
>>> the FilterOutputStream for the ZipOutputStream and the FilterInputStream for the
>>> ZipFile. The PushbackInputStream in ZipInputStream might be an issue ...
>> Thanks for your clues, too. Honestly speaking, we think the current
>> zip implementation may break the data when used PushbackInputStream
>> for the following reasons.
>> * PushbackInputStream uses an unique internal buffer for re-read operation.
>> * But, InflaterInputStream provide date to Inflater per reads and
>> buffer by JNI (zlib).
>> * So we think PushbackInputStream is poor compatibility with
>> InflaterInputStream.
>> We generally use InputStream through ZipEntry#getInputStream(). We do
>> not touch FileInputStream for reading ZIP data. If we call unread()
>> when we use PushbackInputStream as reading ZIP archive, we guess that
>> it will break the reading data.
>> So, our approach do not affect the PushbackInputStream.
>> What do you think about this?
>>> (4) It seems the ZipOutputStream only supports the "stream based" password, while
>>> the ZipInputStream  supports the "entry based" password. Do we really need
>>> "entry based" support here?
>> As your suggestion, we should support "entry based". We will start to
>> implement "entry based" after this discussion is closed.
>> Thanks,
>> Yuji
>>> On 12/17/15, 9:45 PM, Yasumasa Suenaga wrote:
>>>> Hi Jason,
>>>> Thank you for your comment.
>>>> I've fixed it in new webrev:
>>>>    http://cr.openjdk.java.net/~ysuenaga/JDK-4347142/webrev.03/
>>>> Thanks,
>>>> Yasumasa
>>>> On 2015/12/17 0:33, Jason Mehrens wrote:
>>>>> The null check of 'entry' at line 351 of ZipFile.getInputStream  is in
>>>>> conflict with line 350 and 348.
>>>>> ________________________________________
>>>>> From: core-libs-dev<core-libs-dev-bounces at openjdk.java.net>  on behalf of
>>>>> Yasumasa Suenaga<yasuenag at gmail.com>
>>>>> Sent: Wednesday, December 16, 2015 8:47 AM
>>>>> To: Sergey Bylokhov; Xueming Shen
>>>>> Cc: core-libs-dev at openjdk.java.net
>>>>> Subject: Re: [PING] PoC for JDK-4347142: Need method to set Password
>>>>> protection to Zip entries
>>>>> Hi Sergey,
>>>>> Thank you for your comment.
>>>>> I added that description in new webrev:
>>>>>      http://cr.openjdk.java.net/~ysuenaga/JDK-4347142/webrev.02/
>>>>> Thanks,
>>>>> Yasumasa
>>>>> On 2015/12/16 22:19, Sergey Bylokhov wrote:
>>>>>> Should the new methods describe how they will work in case of null
>>>>>> params?
>>>>>> On 16/12/15 16:04, Yasumasa Suenaga wrote:
>>>>>>> I adapted this enhancement after JDK-8145260:
>>>>>>>      http://cr.openjdk.java.net/~ysuenaga/JDK-4347142/webrev.01/
>>>>>>> Could you review it?
>>>>>>> Thanks,
>>>>>>> Yasumasa
>>>>>>> On 2015/12/12 21:23, Yasumasa Suenaga wrote:
>>>>>>>> Hi Sherman,
>>>>>>>> Our proposal is affected by JDK-8142508.
>>>>>>>> We have to change ZipFile.java and and ZipFile.c .
>>>>>>>> Thus we will create a new webrev for current (after 8142508) jdk9/dev
>>>>>>>> repos.
>>>>>>>> Do you have any comments about current webrev?
>>>>>>>>      http://cr.openjdk.java.net/~ysuenaga/JDK-4347142/webrev.00/
>>>>>>>> If you have comments, we will fix them in new webrev.
>>>>>>>> Thanks,
>>>>>>>> Yasumasa
>>>>>>>> On 2015/12/03 16:51, KUBOTA Yuji wrote:
>>>>>>>>> Hi Sherman,
>>>>>>>>> Thanks for your quick response :)
>>>>>>>>> I aimed to implement the "traditional" at this proposal by the below
>>>>>>>>> reasons.
>>>>>>>>>     * We want to prepare API for encrypted zip files at first.
>>>>>>>>>       * Many people use the "traditional" in problem-free scope like a
>>>>>>>>> temporary file.
>>>>>>>>>     * We do not know which implementation of the "stronger" is best
>>>>>>>>> for
>>>>>>>>> openjdk.
>>>>>>>>>       * PKWare claims that they have patents about the "stronger" on
>>>>>>>>> Zip[1].
>>>>>>>>>       * OTOH, WinZip have the alternative implementation of the
>>>>>>>>> "stronger" [2][3].
>>>>>>>>>     * Instead, we prepared the extensibility by ZipCryption interface
>>>>>>>>> to
>>>>>>>>> implement other encrypt engine, such as the AES based.
>>>>>>>>> Thus, I think this PoC should support the "traditional" only.
>>>>>>>>> In the future, anyone who want to implement the "stronger" can easily
>>>>>>>>> add their code by virtue of this proposal.
>>>>>>>>> [1] https://pkware.cachefly.net/webdocs/APPNOTE/APPNOTE-6.3.3.TXT
>>>>>>>>>        (1.4 Permitted Use&  7.0 Strong Encryption Specification)
>>>>>>>>> [2]
>>>>>>>>> https://en.wikipedia.org/wiki/Zip_(file_format)#Strong_encryption_controversy
>>>>>>>>> [3] http://www.winzip.com/aes_info.htm
>>>>>>>>> Thanks,
>>>>>>>>> Yuji
>>>>>>>>> 2015-12-03 12:29 GMT+09:00 Xueming Shen<xueming.shen at oracle.com>:
>>>>>>>>>> Hi Yuji,
>>>>>>>>>> I will take a look at your PoC.  Might need some time and even bring
>>>>>>>>>> in the
>>>>>>>>>> security guy
>>>>>>>>>> to evaluate the proposal. It seems like you are only interested in
>>>>>>>>>> the
>>>>>>>>>> "traditional PKWare
>>>>>>>>>> decryption", which is, based on the wiki, "known to be seriously
>>>>>>>>>> flawed, and
>>>>>>>>>> in particular
>>>>>>>>>> is vulnerable to known-plaintext attacks":-) Any request to support
>>>>>>>>>> "stronger" encryption
>>>>>>>>>> mechanism, such as the AES based?
>>>>>>>>>> Regards,
>>>>>>>>>> Sherman
>>>>>>>>>> On 12/2/15 6:48 PM, KUBOTA Yuji wrote:
>>>>>>>>>>> Hi all,
>>>>>>>>>>> We need reviewer(s) for this PoC.
>>>>>>>>>>> Could you please review this proposal and PoC ?
>>>>>>>>>>> Thanks,
>>>>>>>>>>> Yuji
>>>>>>>>>>> 2015-11-26 13:22 GMT+09:00 KUBOTA Yuji<kubota.yuji at gmail.com>:
>>>>>>>>>>>> Hi all,
>>>>>>>>>>>> * Sorry for my mistake. I re-post this mail because I sent before
>>>>>>>>>>>> get
>>>>>>>>>>>> a response of subscription confirmation of core-libs-dev.
>>>>>>>>>>>> Our customers have to handle password-protected zip files.
>>>>>>>>>>>> However,
>>>>>>>>>>>> Java SE does not provide the APIs to handle it yet, so we must use
>>>>>>>>>>>> third party library so far.
>>>>>>>>>>>> Recently, we found JDK-4347142: "Need method to set Password
>>>>>>>>>>>> protection to Zip entries", and we tried to implement it.
>>>>>>>>>>>> The current zlib in JDK is completely unaffected by this proposal.
>>>>>>>>>>>> The
>>>>>>>>>>>> traditional zip encryption encrypts a data after it is has been
>>>>>>>>>>>> compressed by zlib.[1] So we do NOT need to change existing zlib
>>>>>>>>>>>> implementation.
>>>>>>>>>>>> We've created PoC and uploaded it as webrev:
>>>>>>>>>>>>         http://cr.openjdk.java.net/~ysuenaga/JDK-4347142/webrev.00/
>>>>>>>>>>>>         Test code is as below. This code will let you know how this
>>>>>>>>>>>> PoC
>>>>>>>>>>>> works.
>>>>>>>>>>>> http://cr.openjdk.java.net/~ysuenaga/JDK-4347142/webrev.00/Test.java
>>>>>>>>>>>> In NTT, a Japanese telecommunications company. We are providing
>>>>>>>>>>>> many
>>>>>>>>>>>> enterprise systems to customers. Some of them, we need to
>>>>>>>>>>>> implement to
>>>>>>>>>>>> handle password-protected zip file. I guess that this proposal is
>>>>>>>>>>>> desired for many developers and users.
>>>>>>>>>>>> I'm working together with Yasumasa Suenaga, jdk9 committer
>>>>>>>>>>>> (ysuenaga).
>>>>>>>>>>>> We want to implement it if this proposal accepted.
>>>>>>>>>>>> [1]: https://pkware.cachefly.net/webdocs/APPNOTE/APPNOTE-6.3.3.TXT
>>>>>>>>>>>> (6.0  Traditional PKWARE Encryption)
>>>>>>>>>>>> Thanks,
>>>>>>>>>>>> Yuji

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