john-users - Magic Escape Sequences in Rules

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Date: Sat, 16 Jun 2012 22:52:58 -0700 (PDT)
From: NeonFlash <psykosonik_frequenz@...oo.com>
To: "john-users@...ts.openwall.com" <john-users@...ts.openwall.com>
Subject: Magic Escape Sequences in Rules

Hi,

I need some help in understanding the magic escape sequences used in JTR rules such as, \p, \r, \p0, \p1 to \p9.

I have read the rules documentation here: http://www.openwall.com/john/doc/RULES.shtml

However, unlike other rule flags and options, the magic escape sequences are a little hard to understand, at least for me. It would be great if someone could break down the rules and help understand it better.

I have the following rules which I would like to modify and in order to do that, first I need to get a grasp of how they work:

-[c:] >4 <- \p[c:] i[0-5][!$@...^&()_+\-={}|[\]\\;'":,/<>?`~*]

This will add the special characters everywhere in the string. Here is what I have understood:

-[c:] - reject the rule if the hash type is not case sensitive.
>4 - reject the candidate password if its length is less than 4
<- the length of the candidate password should be less than max_length-1 (max_length is maximum length supported for that hash type)
\p[c:] - \p is the magic escape sequence. 

According to documentation: \p before a range to have that range processed "in
parallel" with preceding ranges.

However in our rule, [c:] is not a range. So, does it allow parallel processing for the following two rules:

[c] - capitalize
[:] - no operation?

i[0-5][!$@...^&()_+\-={}|[\]\\;'":,/<>?`~*] - This will pick a special character from the list and place it in different positions, 0 to 5.

Similarly, I would like to understand the meaning of the magic escape sequences, \p1 and \p2 in the following rule:

-[c:] >[5-8] <- \p1[c:] i\p2[6-9][!$@...^&()_+\-={}|[\]\\;'":,/<>?`~*]

Thanks.

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