modes

unix密码破解软件John the Ripper

 John the Ripper's Cracking Modes
==================================

Mode descriptions here are short, and only cover the basic things. Check
other documentation files for information on customizing the modes.

 Wordlist Mode
---------------

This is the simplest cracking mode supported by John. All you need to do
is specify a wordlist (text file containing one word per line), and some
password files. You can enable rules (which are used to modify words) if
desired, they will then be applied to every word in the list.

The wordlist should not contain dupes. John doesn't sort the words not to
use too much memory, since that would require at least loading the entire
wordlist to memory or temporary space, while now it's read from disk while
cracking. Also, leaving the words order as it is allows you to put frequent
words first. However, if you don't place words in a reasonable order, it is
better if you sort the wordlist alphabetically: John runs a bit faster if
each word it tries only differs from the previous one by a few characters,
this is especially noticable when cracking only a few passwords at a time.
Most wordlists that you may find on the net are already sorted anyway.

However, you shouldn't bother about words longer than 8 (or whatever limit
your current password hashing algorithm has) characters being effectively
the same password if their first 8 characters match. John can handle this
situation (and only try the password once) when such words are going one
immediately after the other (that is, when the wordlist is sorted). You'd
better not truncate words to 8 characters in your wordlist, since the rest
may be needed when you enable the rules.

The recommended way to sort a wordlist for use with default wordlist rule
set is:

	tr A-Z a-z < SOURCE | sort -u > TARGET

See doc/RULES for information on writing your own wordlist rules.

 "Single Crack" Mode
---------------------

This is the mode you should start cracking with. It will try using the
login/GECOS information as passwords. Since the information is only used
on the account it was taken from (and on passwords with the same salt,
which takes almost no extra time), "single crack" mode is much faster than
the wordlist mode, which allows using a lot of rules (they are always
enabled for this mode) in a reasonable time. Guessed passwords are also
tried on the entire password list, just in case more users have the same
password. Of course, this will only get those passwords that are based on
the information used.

Note that running this mode on many password files at the same time may
sometimes get more passwords cracked than you would get if you ran it on
the files separately.

 Incremental Mode
------------------

This is the most powerful cracking mode, it can try all possible character
combinations as passwords. However, it is assumed that cracking with this
mode will never terminate because of the number of combinations being too
large (actually, it will terminate if you set a low password length limit,
or make it use a small charset), and you'll have to interrupt it earlier.

That's why this mode deals with character frequency tables, to get as many
passwords as possible within a limited time.

To use the mode you need a specific definition for the mode's parameters
(including password length limits and the charsets). These parameters are
defined in ~/john.ini's sections called [Incremental:MODE], where MODE is
any name that you assign to the mode (it's the name you'll need to specify
on John's command line). You can either use a pre-defined incremental mode
definition ('All', 'Alpha', or 'Digits'), or define a custom one.

See doc/CONFIG and doc/EXAMPLES for information on defining custom modes.

 External Mode
---------------

You can define an external cracking mode for use with John. This is done
with ~/john.ini's sections called [List.External:MODE], where MODE is any
name that you assign to the mode. The section should contain some functions
that John will use to generate the words it tries. The functions are coded
in a subset of the C language, and are compiled by John at startup (if you
enable the mode on John's command line). See doc/EXTERNAL.

 What Modes Should I Use?
--------------------------

See doc/EXAMPLES for a reasonable order of cracking modes to use.