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Date: Wed, 23 Mar 2011 01:35:11 +0300
From: Solar Designer <solar@...nwall.com>
To: john-users@...ts.openwall.com
Subject: Re: single mode
On Tue, Mar 22, 2011 at 08:25:16PM +0100, magnum wrote:
> I did that fprintf hack so I can answer most of this myself.
I'm sorry I was not quick enough. Thank you for posting the answers!
> * All words from the GECOS field that starts with a letter and consists
> of alphanumeric only (anything else is scrapped)
Not exactly. loader.c uses these separator characters:
/*
* Word separator characters for ldr_split_words(), used on GECOS fields.
*/
#define issep \
"!\"#$%&'()*+,-./:;<=>?@[\\]^_`{|}~\177"
And then there's this check in single.c:
c = (unsigned int)first->data[0] | 0x20;
if (c < 'a' || c > 'z') continue;
> [...] all possible pairs of these words (concatenated with no
> delimiter) are tried. Also, another similar set of pairs is tried with
> *first* word truncated to one character.
It is worth noting that the "first" word here is actually any word with
number below SINGLE_WORDS_PAIR_MAX (which is 4). That is, by default
the first 3 words from the GECOS field will be additionally tested in
their truncated form (as initials).
> jdoe <- truncated pairs
> djohn
Right, that's what I meant above.
> However, only the first four words are allowed as the first half of a
> pair. If there are five words, the fifth will only ever be the second
> half of a pair.
Not exactly. The fifth (and on) won't be "paired" at all. Here's what
happens (excluding combinations with the username, home directory name,
and initials):
w1
w1w2
w1w3
w1w4
w2
w2w1
w2w3
w2w4
w3
w3w1
w3w2
w3w4
w4
w5
w6
As you can see, w5 and w6 were not part of any pair.
> This is to limit the number of combinations and this
> limit can be changed by altering SINGLE_WORDS_PAIR_MAX in params.h and
> recompiling.
Exactly.
> >Would I ever need to swap 1 and 2 in rules? I mean, if I have this rule:
> >
> >-p 1 $@ 2
> >
> >is there any reason to also have:
> >
> >-p 2 $@ 1
> >
> >or will that be tried anyway?
>
> It will be tried anyway
Yes, except for the special case mentioned below.
> unless one of the words is word #5 or higher on the input line.
Yes, but in that case "-p 1 $@ 2" won't be trying the combination as well.
The special case, with default settings, is with word #4, which is never
tried as the first word in a pair (it's only tried as the second).
> There may be a little more to this that I haven't noticed but this is
> the gist of it.
Right. Thanks again!
Alexander
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