Hacks & Cracks/Hacks_and_Cracks.iso/cracking software/john the ripper v1.3, unix password cracker.zip/DOC.ZIP/JOHN.DOC

Text File | 1997-01-12 | 40KB | 943 lines

    John the Ripper v1.3
   ----------------------

==========================
 What is John the Ripper?
==========================

John the Ripper is a UNIX password cracker, currently available for UNIX
(tested with Linux x86, Solaris 2.x SPARC, OSF/1 Alpha), DOS, WinNT/Win95.

I assume that you have already used some UNIX password crackers, so I'll
only describe the things specific to John.

==========
 Overview
==========

John the Ripper is designed to be both powerful and fast. It combines
several cracking modes in one program, and is fully configurable for your
particular needs (you can even code a custom cracking mode using the built
in C compiler). Also, John is available for several different platforms,
which enables you to use the same cracker everywhere (for example even
continue a cracking session that you started on another platform).

John's crypt() routine is highly optimized for faster operation, which
makes John run much faster than other crackers. This applies to both the
x86 assembly version, and the portable pure C one.

John the Ripper supports the following cracking modes:
- wordlist with or without rules;
- "single crack", makes use of the login/GECOS information;
- incremental, tries all character combinations;
- external, allows you to define your own cracking mode.

================
 How to install
================

With binary distributions, just copy all the files to a separate directory.
Then extract there the common files (supplied in a separate archive). You
might also need a 'chmod +x john' depending on the archive type used.

To compile the sources, just enter the directory you extracted them to, and
type 'make'. You'll get a list of systems supported. Select one of those,
or try 'make generic' if your system is not listed. Be sure to use GCC and
GNU make (you might have to type the full path to 'make', since '/bin/make'
is often also present and is not what you need).

============
 How to use
============

I intentionally made John's command line interface be a lot like Cracker
Jack's so that it's easier to start using John for those who have used
Cracker Jack before. Anyway, here's a short description of John's features
including those that are the same as Cracker Jack's.

To use John the Ripper, you need to supply it some password files, and a
cracking mode. Cracked passwords will be printed on the screen and saved
in file called ~/john.pot (in this text '~' means John's "home directory",
i.e. the directory you put John's binary in). This file is also used not
to load the accounts you already cracked if you run John again on the same
password file. To retrieve the cracked passwords from ~/john.pot, use the
'-show' option.

While cracking, you can press the Enter key for status, or Ctrl+C to abort
the session, saving point information to a file (~/restore by default).
By the way, if you press Ctrl+C twice John will abort immediately without
saving. The point information is also saved every 10 minutes in case of a
crash.

 Command line options
----------------------

You can specify some of the following options on John's command line (all
of them are case sensitive, and can be abbreviated):

       -pwfile:<file>[,..]     specify passwd file(s) (wildcards allowed)

This option is used to specify the password files to be cracked (actually,
anything on the command line that is not starting with a dash will be used
as a password file name).

       -wordfile:<file> -stdin wordlist mode, read words from <file> or stdin

These are used to enable the wordlist mode.

       -rules                  enable rules for wordlist mode

Enables rules (like in Crack by Alec Muffett). The rules are stored in
~/john.ini, in section [List.Rules:Wordlist].

       -incremental[:<mode>]   incremental mode [using john.ini entry <mode>]

Enables the incremental mode, using the specified ~/john.ini definition
(section [Incremental:<mode>], where <mode> is what you specify on the
command line, [Incremental:All] by default).

       -single                 single crack mode

Enables the "single crack" mode, using rules from [List.Rules:Single].

       -external:<mode>        external mode, using john.ini entry <mode>

Enables an external mode, using external functions defined in ~/john.ini's
[List.External:<mode>].

       -restore[:<file>]       restore session [from <file>]

Continues an interrupted cracking session, reading point information from
the specified file (~/restore by default).

       -makechars:<file>       make a charset, <file> will be overwritten

Generates a charset file, based on character frequencies from ~/john.pot,
for use with the incremental mode. The entire ~/john.pot will be used for
the charset file unless you specify some password files. You can also use
an external filter() routine with this option.

       -show                   show cracked passwords

Shows the cracked passwords in a convenient form. You should also specify
the password files.

       -test                   perform a benchmark

Benchmarks the performance critical routines and prints a table of estimated
cracking speed values for different number of accounts and salts.

For those unfamiliar with password crackers internals: xform1() and xform2()
are the actual encryption routines, called for each key/salt pair, while
setkey() is called for each word only, meaning that xform1() or xform2()
(depending on the cracking mode used) are the only routines that will affect
cracking speed if there're enough salts loaded. By the way, setkey() is
benchmarked assuming that words differ by 1 character in length, and 1 more
character replaced -- when using with xform2(), and that passwords are 8
characters long and are totally different (no matching characters) -- when
using with xform1().

       -users:<login|uid>[,..] crack this (these) user(s) only

Allows you to filter a few accounts for cracking, or for '-show'.

       -shells:[!]<shell>[,..] crack users with this (these) shell(s) only

This option is useful to crack/show accounts with the required shell only,
or not to crack/show accounts with a bad shell ('!' before a shell name
means 'not'). You can omit the path before a shell name, so '-shells:csh'
will match both '/bin/csh' and '/usr/bin/csh', while '-shells:/bin/csh' will
only match '/bin/csh'.

       -salts:[!]<count>       crack salts with at least <count> accounts only

This feature sometimes allows to achieve better performance. For example
you can crack only some salts using '-salts:2' faster, and then crack the
rest using '-salts:!2'. Total cracking time will be about the same, but
you will get some accounts cracked earlier, and may not need the rest.

       -lamesalts              assume cleartext passwords were used as salts

Don't use this option unless you know what you're doing.

       -timeout:<time>         abort session after a period of <time> minutes

This will cause John to terminate after the specified time has elapsed.

       -list                   list each word

Prints each word being checked on the standard output. This is useful for
checking if your custom cracking mode works correctly.

       -beep -quiet            beep or don't beep when a password is found

The default can be altered in ~/john.ini.

       -noname -nohash         don't use memory for login names or hash tables

You might need these if you don't have enough RAM. Note that '-noname' will
not work with the "single crack" mode, since login names are used while
cracking.

 Additional utilities
----------------------

There're some symlinks to John's binary that might also be useful:

       xtract [source] [> <target>]

Extracts words from a text file (or stdin), to be used as a wordlist. Dupes
are not removed, you'll also need to do a 'sort -u' on the output (in UNIX).

       unshadow <passwd> <shadow> [> <target>]

Combines the passwd and shadow files (when you already have access to both)
for use with John. You might need this since if you only used shadow file,
the GECOS information wouldn't be used by the "single crack" mode, and also
you wouldn't be able to use the '-shells' option.

================
 Cracking modes
================

The mode descriptions here are short, and only cover the basic things.
You should check the "Customizing" section below for more information.

 Wordlist mode
---------------

This is the simplest cracking mode supported by John. All you need 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 RAM, since that would require at least loading the entire
wordlist to memory, 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 accounts at a time).

However, you shouldn't bother about words longer than 8 characters being
effectively the same password if their first 8 characters match. John can
handle this situation (and only try the password once) if such words are
going one immediately after the other (i.e. 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 use the 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 accounts 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. 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 accounts cracked than you would get if you ran it on
the files separately.

It might be a good idea not to run through all the rules, but specify a
timeout, and then go to other modes. The rules should be sorted by the
number for successful cracks for this case.

Cracker Jack users must also note that John's "single crack" mode is
totally different (better) from Jack's. It doesn't require a special
wordlist since the rules support is built into John.

 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 due to the number of combinations being too large
(actually, it will terminate if you set a low password length limit, or let
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 identifier that you assign to the mode (it's the one you'll have to
specify on John's command line). You can use a pre-defined incremental mode
definition, or define a custom one.

Once you have the definition, all you need is specify the incremental mode
option, the mode's identifier and some password files on the command line.

 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 identifier that you assign to the mode. The section should contain some
functions that John will use to generate the words it tries. These 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).

=============
 Customizing
=============

John the Ripper's behavior can be customized by editing its configuration
file, ~/john.ini. You can specify defaults for command line options, some
other John's options that are not accessible from its command line, define
parameters for incremental modes, define rules for wordlist and "single
crack" modes, or even define a new cracking mode.

The configuration file consists of several sections. Each section starts
with a line containing its name, in brackets. Sections consist of either
value assignments to some variables (in form 'variable = value'), or some
other text specific to particular section's type (names of such sections
start with a 'list.'). Section and variable names are not case sensitive.
Lines starting with '#' or ';' and empty lines are ignored, you can use
them for comments, or to comment out lines that you don't want to delete
completely.

 General options
-----------------

Defaults for some command line options can be defined in the [Defaults]
section. You can define the following variables:

Wordfile   Set to your wordlist file name. This will assume the wordlist
           mode by default - no need to use the '-wordfile' command line
           option unless you want to override this default value.

Timeout    Set to the value in minutes. This will enable the timeout for
           all modes by default.

Beep       Set to something starting with 'Y' or 'N' (I hope the meaning
           is clear) to specify whether to beep when a password is found or
           not. This default can be overridden with the '-beep' and '-quiet'
           command line options. If you omit this variable definition, the
           default will be not to beep.

Some other options can be defined in the [Options] section:

Realtime   Set to 'Y' to show elapsed time as D:HH:MM:SS instead of just
           seconds (as Jack does).

Percent    Set to 'Y' to show the progress indicator.

 Incremental mode parameters
-----------------------------

To define the incremental mode parameters you need to create a section
called [Incremental:<mode>], where <mode> is any identifier that you assign
to the mode. There're some pre-defined incremental modes in the default
configuration file supplied with John, you can use them as templates. The
following parameters are supported:

CharCount  Allows you to limit the number of different characters used, to
           make John start trying longer passwords earlier. This can also
           expand the charsets to the specified size when using an external
           charset file which only defines less than CharCount characters.
           By default (when this parameter is not defined) all the defined
           characters will be used.

MinLen     Minimum password length, in characters (1 by default).

MaxLen     Maximum password length, in characters (8 by default).

Wordlike   Set to 'Y' to enable a simple built in word filter (words with
           more than one vowel in a row, or more than two non-vowels in a
           row, will get filtered out).

File       External charset file name (the file is loaded from ~ unless full
           path is specified). Setting this parameter disables the charsets
           defined inside the configuration file.

CharsetNM  (where N and M are digits, 1 <= N <= 8, 1 <= M <= N) Defines a
           charset for password length N, character position M. The order
           of characters is important, more frequent characters should be
           placed first. The charsets don't have to be the same size.

 Wordlist rules
----------------

The rules for wordlist and "single crack" modes are defined in separate
sections called [List.Rules:Wordlist] and [List.Rules:Single] respectively.
I used an extended Crack (by Alec Muffett) syntax, since many of you might
be already familiar with it. I added some more rules, and (most important)
a preprocessor, which generates multiple rules from a single source line.
When defining rules, simply place one rule (which may include preprocessor
commands) per line. Each rule consists of one or more simple commands. The
following commands are supported (most of the descriptions are copied from
Crack's dicts.rules, however the code is my own, and is faster than that
from Crack):

Ordinary commands:
:       no-op - do nothing to the input word
<n      reject word unless it is < n characters long, where n = 0-9
>n      reject word unless it is > n characters long, where n = 0-9
^x      prepend character 'x' to word
$y      append character 'y' to word
l       force word to be lowercase
u       force word to be uppercase
c       force word to be capitalized
r       reverse word: "Fred" -> "derF"
d       duplicate word: "Fred" -> "FredFred"
f       reflect word: "Fred" -> "FredderF"
p       make best attempt to pluralize a lowercase word
onx     overstrike character in position n (start at 0) with character 'x'
inx     insert character 'x' in position n (start at 0) and shift the rest
        of the input string right
        nb: if n > strlen(input), character 'x' will be appended
xnm     extract substring from position n (start at 0) for up to m characters

Commands which may use character classes:
sxy     replace (swap) all characters 'x' in the word with 'y'
s?cy    replace all characters of class 'c' in the word with 'y'
@x      purge all characters 'x' from the word
@?c     purge all characters of class 'c' from the word
!y      reject word if it contains character 'y'
!?c     reject word if it contains a character in class 'c'
/x      reject word unless it contains character 'x'
/?c     reject word unless it contains a character in class 'c'
=nx     reject word unless character at position n is equal to 'x'
=n?c    reject word unless character at position n is in class 'c'
        nb: the word always starts at position 0

Character classes for use in the above commands:
??      matches '?'
?v      matches vowels: "aeiouAEIOU"
?c      matches consonants: "bcdfghjklmnpqrstvwxyzBCDFGHJKLMNPQRSTVWXYZ"
?w      matches whitespace: " \t"
?p      matches punctuation: ".,:;'\"?!`"
?s      matches symbols "$%^&*()-_+=|\\<>[]{}#@/~"
?l      matches lowercase letters ('a' to 'z')
?u      matches uppercase letters ('A' to 'Z')
?d      matches digits ('0' to '9')
?a      matches letters ('a' to 'z' and 'A' to 'Z')
?x      matches letters and digits ('a' to 'z', 'A' to 'Z' and '0' to '9')
The complement of a class may be matched by the uppercase of its letter,
i.e.: where ?d == DIGITS, ?D == NON-DIGITS, and so on.

All the commands described above are the same as in Crack v4.1, while the
following ones are added in John (not very useful, I admit, most of the
required stuff was already implemented in Crack v4.1):

{       shift word left: "jsmith" -> "smithj", etc
}       shift word right: "smithj" -> "jsmith", etc
Dn      delete character in position n (start at 0) and shift the rest of
        the input string left
P       "crack" -> "cracked", etc (lowercase only)
G       "crack" -> "cracking", etc (lowercase only)
~i      invert case, by keyboard: "Crack96" -> "cRACK(^", etc
~I      invert case: "Crack96" -> "cRACK96", etc
~v      lowercase vowels: "Crack96" -> "CRaCK96", etc
~>      shift each character right, by keyboard: "Crack96" -> "Vtsvl07", etc
~<      shift each character left, by keyboard: "Crack96" -> "Xeaxj85", etc

Extra "single crack" mode commands for word pairs support, to control if
other commands are applied to the first, second, or both words:

1       first word only
2       second word only
+       the concatenation of both (should only be used after a '1' or '2')

If you use some of the above commands in a rule, it will only process word
pairs (full names, from the GECOS information), and reject single words.
A '+' is assumed at the end of any rule that uses some of these commands,
unless you specify it manually. For example, '1l2u' will convert the first
word to lowercase, the second one to uppercase, and use the concatenation
of both. The use for a '+' might be to apply some more commands: '1l2u+r'
will reverse the concatenation of both words, after applying some commands
to them separately.

[ Crack v5.0 wasn't out by the time I was coding rule support for John, so
I extended the syntax my own way. Actually, the new Crack v5.0's rules seem
redundant, or match with what I already added to John ([ == D0, ] == rD0r,
C == c~I, t == ~I, (x == =0x, )x == r=0xr, 'n == x0n). The only rule left
is %nx, or %n?c (rejects the word unless it contains at least n instances
of character 'x', or of members of class 'c'). Anyway, I added all these to
John, for compatibility reasons. Be sure to prefix '[' and ']' with a '\'
if you use them, since they're control characters for the preprocessor. ]

If a rule (line of commands) doesn't change a word, it is rejected, unless
the entire rule was a plain ':'. This assumes you have a ':' somewhere in
your rules list.

The preprocessor is used to combine similar rules into one source line. For
example, if you need to make John try lowercased words with digits appended,
you could write a rule for each digit, 10 rules total. Now imagine appending
two-digit numbers -- the configuration file would get large and ugly.

With the preprocessor you can do these things easier. Simply write one
source line containing the common part of these rules, and the list of
characters you would have put into separate rules, in brackets (the way
you would do in a regular expression). The preprocessor will then generate
the rules for you (at John's startup). For the examples above, the source
lines will be 'l$[0-9]' (lowercase and append a digit) and 'l$[0-9]$[0-9]'
(lowercase and append two digits). These source lines will be expanded to
10 and 100 rules respectively. By the way, the preprocessor's commands are
processed right-to-left, and the characters are processed left-to-right,
which gets a normal order of numbers in such cases as in the example with
appending two-digit numbers. Note that I only used character ranges in these
examples, however you can combine them with character lists, like '[aeiou]'
will use vowels, and '[aeiou0-9]' will use vowels and digits.

There're some control characters in rules ('[' starts a preprocessor's
character list, '-' marks a range inside the list, etc). You should prefix
them with a '\' if you want to put them inside a rule without using their
special meaning. Of course, the same applies to '\' itself. Also, if you
need to start a preprocessor's character list at the very beginning of a
line, you'll have to prefix it with a ':', or it would be treated as a new
section start.

 Defining an external mode
---------------------------

To define an external cracking mode you need to create a section called
[List.External:<mode>], where <mode> is any identifier that you assign to
the mode. The section should contain some functions that are coded in a
subset of the C language. John will compile and use them if you enable the
mode on its command line. The compiler produces virtual machine code which
is then either interpreted or converted into machine executable code (this
is currently done for x86 hardware only).

The following functions are currently used by John:

init()     called at startup, should initialize global variables
filter()   called for each word to be tried, can filter some words out
generate() called to generate words, when no other cracking modes used
restore()  called when restoring an interrupted session

All of them are of type 'void', with no arguments, and should use global
variable 'word' (which is pre-defined as 'int word[9]'), except for init()
which is called before 'word' is initialized. The 'word' variable contains
current word to be tried, in ASCIIZ. filter() can modify it, or zero out
'word[0]' to skip it. generate() shouldn't assume any particular value of
'word' when it gets called, but should put there the next word to be tried,
or zero out 'word[0]' when cracking is complete (this will cause John to
terminate). restore() should set global variables to continue from the
supplied 'word'.

You can either use an external mode separately, or with some other cracking
mode, in which case only init() and filter() will be used (and only filter()
will be required). Using an external filter is compatible with all the other
cracking modes and '-makechars' command line option.

It is recommended that you don't use filter(), or at least don't filter too
many words out when using an external mode with your own generate(). Better
modify generate() not to generate words that would get filtered out.

As I already mentioned above, the compiler supports a subset of C. John is
a cracker, not a compiler, so I don't think it needs anything else. Here's
a list of C features that are missing in John's compiler:

- only standard functions supported, you can't define your own ones;
- only 'while' loops are supported;
- only 'int' and 'void' data types supported;
- only single dimensional arrays supported;
- structs/unions are not supported;
- pointers are not supported (right, more about arrays below);
- probably something else...

Some of the supported features differ from those of C:

- array name alone refers to its first element (the one with zero index),
  not the array's address;
- '++' and '--' operations are performed while the expression is being
  calculated, not pre/post-calculated; this will give the same result as in
  C in most cases (like 'i = j++;' is equal to 'i = j; j = j + 1;' in both
  C and John's compiler), but if the variable these operations are applied
  to is used more than once in one expression, the result will differ from
  that of C (like 'i = j++ - j++;' is equal to 'i = j - (j + 1); j = j + 2;'
  in John's compiler, but 'i = j - j; j = j + 2;' in C);
- I hope nothing else differs...

However, the powerful C expression syntax (all the integer operations),
'if'/'else' and 'while' are still available for use. It should be enough
for coding almost anything. You can use the external mode example in the
configuration file supplied with John as a template.

================
 Usage examples
================

These examples are to give you some tips on what John's features can be
used for. Some of them may not be obvious, I'm sorry if others are, but
anyway, I just got tired of answering questions.

 Command line
--------------

1. Assume you just got a password file, 'passwd.1', and want to crack it.
It is wise to start with the "single crack" mode:

   john -single passwd.1

or, since options can be abbreviated (however, I'll be using full names for
most options in these examples):

   john -si passwd.1

If you have more files to crack, better to load them at the same time:

   john -single passwd.1 passwd.2

or even:

   john -single passwd.*

2. Now, you got some passwords cracked, they are saved in ~/john.pot. You
want to retrieve them:

   john -show passwd.1

If the account list gets large and doesn't fit on the screen, you can of
course use output redirection, like:

   john -show passwd.1 | more

Now, you may notice that many accounts have a disabled shell, you can make
John ignore these (assume that shell is called '/etc/expired'):

   john -show -shells:!/etc/expired passwd.1

or, shorter, but will also match '/any/path/expired':

   john -show -shells:!expired passwd.1

or, if you also want to ignore some other shell, say '/etc/newuser':

   john -show -shells:!expired,!newuser passwd.1

To check if any root (uid 0) accounts cracked:

   john -show -users:0 passwd.1

or, to check for cracked root (uid 0) accounts in all the files:

   john -show -users:0 passwd.*

To display the root (login 'root') account only:

   john -show -users:root passwd.1

3. When the "single crack" mode doesn't give enough accounts, you can use
more powerful cracking modes, like the wordlist one. Assume your wordlist
file is called 'words.lst':

   john -w:words.lst passwd.1

or, with rules enabled (slower, but more powerful):

   john -w:words.lst -rules passwd.1

To only crack accounts with a good shell (in general, both the '-shells'
and '-users' filters described above work for all the cracking modes also):

   john -w:words.lst -rules -shells:sh,csh,tcsh,bash passwd.1

Like with all the other cracking modes, faster to crack all the files you
need cracked simultaneously:

   john -w:words.lst -rules passwd.*

You can crack some accounts only. This will try cracking all root (uid 0)
accounts in all the password files:

   john -w:words.lst -rules -users:0 passwd.*

However, I don't recommend cracking root passwords only, since it usually
takes longer to crack the password (often impossible within a reasonable
time) than to hack root using security holes. If you are cracking your own
password file to ensure the passwords are uncrackable, better select a good
root password, and only crack the rest.

Sometimes it is useful to split your password files into two parts which
you crack separately, like:

   john -w:words.lst -rules -salts:2 passwd.*
   john -w:words.lst -rules -salts:!2 passwd.*

This will make John try salts with two or more accounts faster, and then
try the rest. Total cracking time will be about the same, but you will get
some accounts cracked earlier, and may not need the rest. Also, you might
want to try all the accounts with a small wordlist, and only those that you
can try faster (with '-salts:2') with a larger one. Often it is better to
use a larger value than 2 for '-salts' (sometimes even as high as 1000 will
do), adjust it for your particular case.

Note that the default wordlist rules include ':' (which means 'try words
as they are in the list') as the first line. If you already ran through a
wordlist without using rules, and then decided to try the same wordlist
with rules also, you'd better comment this line out.

4. The most powerful cracking mode in John is incremental. You can simply
run:

   john -i passwd.1

This will use the default incremental mode parameters, which are defined in
~/john.ini's [Incremental:All] section. In the configuration file supplied
with John these parameters are to use the full 95 character charset, and to
try all possible password lengths, from 1 to 8 characters. Don't expect this
to terminate in a reasonable time (unless all the passwords were weak and
got cracked).

In many cases it is faster to use some other pre-defined incremental mode
parameters and only crack simpler passwords, from a limited charset. The
following command will try 26 different characters only, passwords from
'a' to 'zzzzzzzz':

   john -i:alpha passwd.1

Again, you can crack root accounts only and use some other John's features
with the incremental mode. This command will try cracking all root (uid 0)
accounts in all the password files, and only those of them that produce
matching salts, so you get at least twice the performance -- if you have a
lot of password files (like 1000 of them, named '*.pwd'), otherwise there
will be no roots with matching salts:

   john -i -users:0 -salts:2 *.pwd

5. If you got a password file and already have a lot of accounts cracked
and/or sniffed (but need some more), and the passwords are unusual, then
you might want to generate a new charset file, based on characters from
that password file only:

   john -makechars:custom.chr passwd.1

Then use that new file for the incremental mode.

If you got several password files from the same country, it might be useful
to use all of them for the charset file that you then use to crack more
accounts in these files or some other password files from that country:

   john -makechars:custom.chr passwd.1 passwd.2
   <add your custom incremental mode definition to ~/john.ini>
   john -i:custom passwd.3

In the example above, I assume that 'passwd.1' and 'passwd.2' are password
files from the same country that you already have a lot of accounts for,
and 'passwd.3' is the password file you need cracked.

You can use some pre-defined or custom word filters when generating the
charset file, to make it only try some simpler words:

   john -makechars:my_alpha.chr -external:filter_alpha passwd.1

If your ~/john.pot file got large enough (or if you don't have any charset
files at all), you might want to use it for the new charset files:

   john -makechars:all.chr
   john -makechars:alpha.chr -external:filter_alpha
   john -makechars:digits.chr -external:filter_digits

In the example above, John will overwrite the charset files (if they already
exist) with the ones based on your entire ~/john.pot (John uses the entire
file if you don't specify any password files). Note that the word filters
used are pre-defined in ~/john.ini supplied with John for your convenience.

 Configuration file
--------------------

1. Assume you notice that in some password file a lot of users have their
passwords set to login names with '?!' appended. Then you just make a new
"single crack" mode rule, and place it somewhere in the beginning:

   [List.Rules:Single]
   $?$!

Hint: if you want to temporary comment out all the default rules, you can
simply rename the section to something John doesn't use, and define a new
one with its old name, but be sure to leave the 'list.' part of the name,
so you don't get a parse error.

All the same applies to the wordlist rules also.

2. If you generate a custom charset file (described above) you will also
need to define a ~/john.ini section with the incremental mode parameters.
In the simplest case it will be like this (where 'Custom' can be replaced
with any name you like):

   [Incremental:Custom]
   File = custom.chr

This will make John use characters that were in passwords used to generate
the charset file only. If you want to use all the 95 characters, you will
also need to add:

   CharCount = 95

Adding this line will tell John to expand the charsets if some of the 95
characters (ASCII codes 32 to 126) didn't occur while generating the file.
The characters are added in that order: a-z, A-Z, 1-9, 0, the rest.

You can also use CharCount to limit the number of different characters that
John tries:

   CharCount = 25

If you didn't use any filters when generating the charset file, setting
CharCount that low will most likely disable some rare characters, and make
John try complicated long passwords earlier.

To make John try passwords of some lengths only, use the following lines:

   MinLen = 6
   MaxLen = 8

Setting 'MinLen' high, as in the example above, is reasonable if shorter
passwords weren't allowed to set on the machine you got the password file
from (however, note that root can usually set any password for any user).

On the contrary, you might want to set 'MaxLen' low if you think there are
enough short passwords.

When using alphabetical characters only, it may be useful to enable the
simple built in word filter, if many passwords are simple enough:

   [Incremental:Wordlike]
   CharCount = 26
   MinLen = 3
   Wordlike = Yeah
   File = alpha.chr

3. When using John on machines with only 4Mb (or less) of RAM installed, you
may need to use smaller charsets, since the ones generated with '-makechars'
require a lot of memory when expanded (for faster operation). You might also
need this if you load a lot of password files, and don't have enough memory
left, or to make John run a little faster when cracking only a few (or one)
salt. This happens because John can take the advantage of each word it tries
being like the previous one, with only some characters changed. When it uses
large external charset files, the words are tried in a different order than
when using smaller charsets inside of ~/john.ini, and are too different from
each other. However, note that a little increase of comparisons/second does
not always mean you get your passwords cracked faster, the better order of
tries when using the larger external charsets is also important. So it is
wise to only use the smaller charsets if there's no other choice, or if you
will be trying all the character combinations anyway.

I intentionally left the smaller charsets inside of ~/john.ini supplied with
John so you can just comment out the 'File =' lines, and they will be used
instead of the large external ones.

4. Another use of the smaller charsets may be to define them manually for
some special cases. For example, if you know a place where users often
suffix their passwords with '1':

   [Incremental:Suffix1]
   MinLen = 6
   MaxLen = 6
   Charset61 = abcdefghijklmnopqrstuvwxyz
   Charset62 = abcdefghijklmnopqrstuvwxyz
   Charset63 = abcdefghijklmnopqrstuvwxyz
   Charset64 = abcdefghijklmnopqrstuvwxyz
   Charset65 = abcdefghijklmnopqrstuvwxyz
   Charset66 = 1

Of course, you can do the same for other lengths. It is also wise to sort
the characters by their frequencies. If you're too lazy to actually do that,
you can simply take the charsets from a pre-defined incremental mode. For
example, if you take Charset61 to 65 in the example above from the default
[Incremental:Alpha] definition's Charset51 to 55, you will get almost what
you would get if calculating the frequencies for 6 character long passwords
with first 5 characters being alphabetical, and '1' at the end.

5. You can do the same thing as in the example above by coding an external
word filter:

   [List.External:Filter1]
   void filter() {
     int i;

     i = 0;
     while (word[i] && word[i] >= 'a' && word[i] <= 'z') i++;
     if (word[i] != '1' || word[i + 1]) word = 0;
   }

This filter will only leave words with some alphabetical characters and '1'
at the end. You can now use it with some other cracking modes, but this will
most likely be slow, since most words will get filtered out. Better to use
it for generating the charsets, and use them (if you have enough passwords
cracked that will pass the filter).

If you can't use the frequency tables for some reason, you can do the same
by coding a totally new external mode:

   [List.External:Suffix1]
   int len, current[9];

   void init() {
     int i;

     current[len = 6] = 0; current[i = len - 1] = '1';
     while (i--) current[i] = 'a';
   }

   void generate() {
     int i;

     i = len + 1;
     while (i--) word[i] = current[i];

     i = len - 2;
     while (++current[i] > 'z')
     if (i) current[i--] = 'a'; else current = -1;
   }

   void restore() {
     int i;

     i = len + 1;
     while (i--) current[i] = word[i];
   }

=========
 Credits
=========

While developing John, I used some ideas from other password crackers:

- Crack by Alec Muffett --
    wordlist rules syntax;
- Cracker Jack by Jackal --
    user interface;
- Star Cracker by The SOrCErEr --
    thanks for proving the large charset files are worth implementing.

The crypt() routine is based on the old one by Alec Muffett, that came
with Crack v4.1. Only some initialization routines (which are not time
critical) remained almost unchanged now, the rest is re-coded using my
own ideas and some from other crypt() implementations (actually, there
are now several different algorithms supported with #ifdef's to better
match your architecture).

I'd like to thank Roman Rusakov for the x86 assembly version of crypt()
that my implementation is based on. His optimization hints are great.

The DOS version is compiled with DJGPP v2 by DJ Delorie with GCC 2.7.2
(http://www.delorie.com), the DPMI server is by Charles W Sandmann
([e-mail]; 1206 Braelinn, Sugar Land, TX 77479), its source
code is at ftp://ftp.simtel.net/pub/simtelnet/gnu/djgpp/v2misc/csdpmi3s.zip.

Cygnus Developer's Kit (http://www.cygnus.com/gnu-win32) was used to compile
the Win32 version.

========================
 How can I contact you?
========================

Send your mail to [e-mail] or 2:5020/398.9, or catch me on EFnet IRC,
my nick is Solar_Diz.

Please, don't ask me questions until you read this entire file (and some
FAQs on password cracking in general, if you're unfamiliar with it). Also,
do not send me password files, I'm not a cracking service.

Signed,
Solar Designer