[issue34546] Add encryption support to zipfile

[大野隆弘]

大野隆弘  added the comment:

My original reason of this is supporting Windows Explore decryption.
That doesn't support AES but support only this traditional PKWARE
encryption.
In my work, some recipients who received the zip file cannot install 3rd
party tools on their Windows
https://blogs.msdn.microsoft.com/oldnewthing/20180515-00/?p=98755

But as Christian explained for me in below thread, I understand we should
use 3rd party module for this purpose
https://mail.python.org/pipermail/python-dev/2018-September/155091.html

Thanks and Regards,
---
Takahiro Ono

2018年9月8日(土) 6:34 Serhiy Storchaka :

>
> Change by Serhiy Storchaka :
>
>
> --
> resolution:  -> rejected
> stage: patch review -> resolved
> status: open -> closed
>
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[issue34546] Add encryption support to zipfile

[Serhiy Storchaka]

Change by Serhiy Storchaka :


--
resolution:  -> rejected
stage: patch review -> resolved
status: open -> closed

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[issue34546] Add encryption support to zipfile

[Christian Heimes]

Christian Heimes  added the comment:

-1 from me, too.

Serhiy already made a valid point and suggested a better alternative.

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[issue34546] Add encryption support to zipfile

[Serhiy Storchaka]

Serhiy Storchaka  added the comment:

What is the reason of using such weak encryption? It looks to me that creating 
a non-encrypted ZIP file and encrypting it with third-party tools is the right 
way if you need an encryption.

--
nosy: +christian.heimes

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[issue34546] Add encryption support to zipfile

[Roundup Robot]

Change by Roundup Robot :


--
keywords: +patch
pull_requests: +8520
stage:  -> patch review

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[issue34546] Add encryption support to zipfile

[大野隆弘]

大野隆弘  added the comment:

Agree, we should not enhance weak encryption to the world.
But unfortunately, MS Windows supports only this type of encryption as far as I 
researched.
https://blogs.msdn.microsoft.com/oldnewthing/20180515-00/?p=98755

That is the my first motivation of Traditional PKWARE encryption(a.k.a  
ZipCrypto/Standard Zip 2.0 encryption) support.
If this big platform supports AES, we don't have any reason to support. But 
unfortunately not.


On the other hand, encryption algorithm compromising happens forever.
I believe python developers must have ability to make decision of suitable 
algorithm because "We are all (consenting) adults here".(I love this phrase)

Also implementing other algo (including AES) support must affect to decryption 
of zipfile module. 
As we can imagine it should be big task and should be divided.

These are the background of my suggestion.

In summary, 
 1. We don't have to support "weak" encryption like DES/RC2 although they are 
on the document.
 2. But Traditional PKWare Encryption is special enough to support because of 
the circumstances.
 3. Other algo support in both decrypt/encrypt should be implemented sooner or 
later.

Any feedback is welcome.


FYI  : All candidate of Zip encryption
-
(Traditional PKWARE encryption)
+
0x6601 - DES
0x6602 - RC2 (version needed to extract < 5.2)
0x6603 - 3DES 168
0x6609 - 3DES 112
0x660E - AES 128 
0x660F - AES 192 
0x6610 - AES 256 
0x6702 - RC2 (version needed to extract >= 5.2)
0x6720 - Blowfish
0x6721 - Twofish
0x6801 - RC4

https://pkware.cachefly.net/webdocs/casestudies/APPNOTE.TXT
7.2.3.2 AlgId

-

FYI 2. Other languages/tools support

Perl : "Support Encryption" is in TODO 
https://metacpan.org/pod/Archive::Zip

Go : Both (AES/Traditional) encryption is going to be integrated( discussion 
was suspended?)
https://github.com/golang/go/issues/12081

Ruby : Supports as experimental
https://github.com/rubyzip/rubyzip/blob/master/README.md


WinZip : Supports but not recommended.
http://kb.winzip.com/help/help_encryption.htm

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[issue34546] Add encryption support to zipfile

[Serhiy Storchaka]

Serhiy Storchaka  added the comment:

>From the official ZIP files specification:

This form of encryption is considered weak by today's standards
and its use is recommended only for situations with
low security needs or for compatibility with older .ZIP
applications.

I think that the support of encrypting ZIP files using the traditional PKWARE 
encryption was intentionally omitted in the zipfile module, because we don't 
want to encourage using such weak encryption method. If you need to add 
encrypted data in the ZIP file, use third-party tools for encrypting it before 
adding to the ZIP file or encrypting the whole ZIP file after creating.

I'm -1 for adding support of weak encrypting.

Of course, adding support for the strong (AES) encryption in ZIP files would be 
nice. But this task is much more difficult.

--
nosy: +alanmcintyre, serhiy.storchaka, twouters

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[issue34546] Add encryption support to zipfile

[Brett Cannon]

Change by Brett Cannon :


--
title: Zipfile encryption function -> Add encryption support to zipfile

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