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Date: Wed, 1 Apr 2020 15:38:40 +0200
From: magnum <john.magnum@...hmail.com>
To: john-users@...ts.openwall.com
Subject: Re: Some 7Zip hashes can't be cracked?
On 2020-03-24 20:20, magnum wrote:
> On 2020-03-17 19:13, magnum wrote:
>> On 2020-03-17 08:25, Jonathan A wrote:
>>> I have a sample of an encrypted 7Zip file (I know the password). When
>>> I use
>>> 7z2john.pl on it, I get *a long hash (492 kb)*. Then when I try using
>>> john
>>> with the known password (i.e. through stdin or wordlist) - it finishes
>>> unsuccessfully.
>>
>> So it does accept it? We hate false negatives :-(
>>
>>> The only difference I could see myself between the two is that 7Zip says
>>> the first file is encrypted with *LZMA2:768k BCJ 7zAES*.
>>
>>> (I can share the first sample, but it has malware in it (I'm a malware
>>> researcher), so it can't go in this email).
>>
>> I guess we don't support BCJ. I should be able to fix that. Please
>> mail med the sample!
>
> This was indeed the case. This is now an issue with upstream 7z2hashcat.
> It has to be fixed first, then John (and hashcat) need to be fixed as well.
>
> https://github.com/magnumripper/JohnTheRipper/issues/4234
This is now completely fixed in bleeding-Jumbo on GitHub. After
upgrading, you also need to re-run 7z2john.pl on all files to be sure
you're not bitten by the bug.
Beware: I opened an issue with hashcat and also sent a PR to upstream
7z2hashcat but until they are fixed, hashcat will still give false
negatives with no warning.
magnum
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