john-users - LM and halves, length limit, does john "attack" halves together?

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Message-ID: <20150702204054.GA12483@openwall.com>
Date: Thu, 2 Jul 2015 23:40:54 +0300
From: Aleksey Cherepanov <lyosha@...nwall.com>
To: john-users@...ts.openwall.com
Subject: LM and halves, length limit, does john "attack" halves together?

I'd like to know how john handles candidates in relation to halves of
LMs?

Let's consider "Password1" password. There will be 2 LMs with
passwords: PASSWOR and D1 . Does john know that first 7 chars should
be cut off? I don't see that in code.

But I see a rule for that:

# Used for loopback. This rule will produce candidates "PASSWOR" and "D" for
# an input of "PASSWORD" (assuming LM, which has halves of length 7).
[List.Rules:Split]
:
-s x**

I find "Used for loopback" misleading because john (jumbo) stores
truncated passwords in .pot. The rule is for original attack and it
should be combined with other rules. Would not it be more convenient
to do that in format itself?

Thanks!

-- 
Regards,
Aleksey Cherepanov

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