All you want to know about UNIX passwords

by The Editor [Published on 16 Oct. 2002 / Last Updated on 23 Jan. 2013]

Description of /etc/passwd in different systems. .

INTRODUCTION

  FINALLY! A half-way decent UNIX 'passwd' cracker for the Macintosh. MACCRAC
  is a very well ported version of one of the PC world's best 'passwd'
  Crackers, CRACK V4.1. MACCRAC is great if you know how to use it, AND, more
  importantly, if you know what UNIX password cracking is about in the first
  place. Unfortunatley, the Mac underground have been SO long deprived of a
  decent UNIX passwd cracker, alot of us are quite a bit behind in the
  concept. That's what this tutorial is provided for. Hopefully after reading
  it, not only will you have an understanding of how to use MACCRAC, but also
  an increased understanding of what UNIX hacking is about in the first place.

 PURPOSE OF CRACKING THE passwd

  Traditionally stated, the purpose of hacking a UNIX is: to "get to ROOT."
  This refers to the ROOT account that every UNIX system has as part of it's
  Operating system. The ROOT is a 'Trusted User' account, THE most powerful
  account on a UNIX. If you can hack a ROOT you can utilize or exploit every
  function a UNIX is capable of. But to get to "ROOT" you have to have
  somewhere to start. For the purposes of this file, that somewhere is with
  the 'passwd' file.

 WHAT'S THE passwd?

  'passwd' is the common name of the file in which user account information is
  stored on a UNIX system. You might consider it a comprehensive users list.
  The file contains the information for an accounts USERNAME, PASSWORD, USER
  NUMBER, GROUP, GECOS, HOME DIRECTORY, and SHELL. A single entry of a passwd
  file entry might look like this:

               PASSWORD        GROUP NUMBER    HOME DIRECTORY
              /               /               /
             /               /               /
kbahadur:8d34jSjs73hsb:2162:15:Ken Bahadur:/usr/users/kbahadur:/usr/bin/ksh
 \                      \             \                          \
  \                      \             \                          \
   USERNAME               USER NUMBER   GECOS INFORMATION          SHELL

  Now take a look at the PASSWORD in this entry: 8d34jSjs73hsb. This is, in
  fact, NOT the password. It is, instead, the encrypted equivalent TO the
  password. As part of the UNIX Account Registration process, when a User
  designates a password, the UNIX takes the password, and (*this is
  important*) uses the other information from the account to generate an
  encrypted equivalent to the actual password. Why? Because as part of the
  UNIX operating system, users MUST have access to the 'passwd' file to be
  able to login. But if anyone who has an account can access the 'passwd'
  file, they can also see what everyone else's Password is. So, UNIX's
  security against this is to encrypt the password entry for each users
  account so that noone else will know what anyone elses password is.
  Unfortunaley/fortunatley (depending on who you are) the algorithm UNIX uses
  to perform this encryption has been known to Hackers for sometime. And so if
  you can see this:

           encrypted equivalent of pasword
             /
kbahadur:8d34jSjs73hsb:2162:15:Ken Bahadur:/usr/users/kbahadur:/usr/bin/ksh

  ...you can use MACCRAC or any other of well over 50 'passwd' file crackers
  to "guess" the password to this account entry. "Guess?" You say? "How does
  that work?" It works like this:

 GUESSING THE PASSWORD

  First a UNIX 'passwd' file cracker takes an encrypted password equivalent
  (i.e.: 8d34jSjs73hsb) from an account entry in a UNIX 'passwd' file and
  holds it to be used as a Reference. From whichever account entry the
  encrypted equivalent was pulled, is the particular account the 'passwd' file
  cracker will attempt to crack at that time.

  Next the 'passwd' file cracker goes through a process of "guessing". In this
  process a single word is pulled from a Dictionary file (more on Dictionaries
  later), encrypted utilizing the UNIX encryption algorithm (the one all us
  hackers know about), and compared, checking to see if the derived encrypted
  word matches the encrypted password equivalent used as a Reference.

  If the encrypted word matches the Reference, the 'passwd' file cracker
  considers it an accurate guess, it then logs the information, and moves on
  to the next account. If the two do not match, the 'passwd' file cracker
  pulls another word from the Dictionary file and goes through the guessing
  process again. If the 'passwd' file cracker goes through every word in a
  Dictionary file and never matches the Reference, the entry is skipped, and
  the cracker moves on to the next account.

  Now, as complicated as this may seem, it is all a relativley easy task for a
  computer. As such, UNIX 'passwd' files are cracked on a regular basis. As a
  result of this a number of security and other measures now (potentially)
  exist to prevent unauthorized persons from accessing a UNIXes'passwd' file.
  This is the topic of the next section. To this point you should understand
  why UNIXes are hacked (to get to ROOT) and understand a little about
  'passwd' files and their role in UNIX hacking. Got it?

 GOT IT, NOW WHAT?

  Ok, at this point you should be ready to try and find a UNIX 'passwd' file
  to crack, right? Wrong. You still have a couple of minor, requisite tasks to
  perform. First, (obviously) you'll need to find a UNIX to hack. In most
  cases, you've already got one in mind, but just in case you don't we'll take
  a look at a few. Also, once you've found a UNIX to hack, you'll need an
  account on that UNIX. There's no way to steal the 'passwd' file from a UNIX
  without first having an account on it (not true, you can always get a
  'passwd' file from someone else, but ignore this because I'm contradicting
  myself). Once you've accomplished your requisites you can start trying to
  steal the 'passwd' file.

  Step 1. Finding a UNIX to Hack
  ------------------------------
  Seeing as how you're reading this file you probably already have a UNIX in
  mind. But, for the sake of clarity, heres what a common UNIX login screen
  looks like:

Ultrx v4.3 (rev .44)

login:

  Other UNIX machines are: System V, BSD, Xenix, and AIX. Look for these names
  to be somewhere in the login screen. Knowing what type of UNIX you're using
  will aid you in hacking it.

  Step 2. An account to start with
  --------------------------------
  If you already have a UNIX account go to Step 3. If you do not already have
  an account, you need to get one. Either: trade for one, trash for one, get a
  legitimate one, or hack one out by hand. The first three options are
  probably the easiest. You can trade for UNIX accounts on IRC channels #hack
  or #phreak. You can trash for accounts in dumpsters and trashcans at most
  Colleges or Universities. You can buy legitimate accounts from any one of
  the rapidly increasing number of Internet Service Providers (they almost all
  use UNIX). But, of coure, as well know you're a hacker, and the only hing
  you wanna do is Hack an account. So be it. Here's a list of UNIX defaults.
  *NOTE* These are NON-PASSWORDED accounts. They are common on System V, BSD,
  Xenix, and AiX. "These defaults are included in standard setup on various
  machines so the Sysadmin can log on for the first time." In some instances,
  negligent Admins will forget to change or delete these accounts. If so,
  you've got an account to start with. Remember, these are NON-PASSWORDED so
  if they work you shouldn't be prompted for a password. If a password is
  prompted for, try using the Account name for the password as well.

    [Stolen from CoTNo #01]

    root                 bin                  adm
    makefsys             sysadm               sys
    mountfsys            rje                  sync
    umountfsys           tty                  nobody
    checkfsys            somebody             setup
    lp                   powerdown            ingres
    dptp                 general              guest
    daemon               gsa                  user
    trouble              games                help
    nuucp                public               unix
    uucp                 test                 admin
    student              standard             pub
    field                demo                 batch
    visitor              listen               network
    uuhelp               usenet               sysinfo
    cron                 console              sysbin
    who                  root2                startup
    shutdown             ncrm                 new

  Step 3. Stealing the passwd file
  --------------------------------
  Once you've got your UNIX accpunt you can ATTEMPT to steal the 'passwd' file
  from it. I emphasize ATTEMPT because the 'passwd' file can be protected in a
  number of ways, or located in a number of different places. We will explore
  some common methods of exploiting the 'passwd' file.

  -Common UNIX Hack-

  This is probably THE easiest and most common UNIX hack. ogin in to your
  account and try typing this at the prompt:

 prompt   concatenate           Note on: 'booya>' is the name of the account
  /      /                      prompts   prompt on the machine I'm using in
booya> cat /etc/passwd                    these examples. The prompt on your
            /      \                      machine will be different. Also
      directory    filename               DON'T type 'booya>' with an entry.


  'cat' is short for concatenate, a command used for reading and displaying
  files in standard output. '/etc' is the common directory for the password
  file on older UNIXes. 'passwd' is the common password filename on UNIXes. If
  you entered: cat /etc/passwd and got a listing that looks like this
  (abbreviated):

kbahadur:IS3fhZdWX3JGU:2162:15:Ken Bahadur:/usr/users/kbahadur:/usr/bin/ksh
             \
            password intact

  ...then congrats! You've succesfully listed out (stolen) your first 'passwd'
  file. *Buffer* the entire contents to a text file, save it and jump down to
  the section: MACCRAC-ING.

  If you got a listing that looks like this:

         password tokenized
          /
intruder:x:263:200:Jack Harmon:/usr/users/intruder:/bin/csh

  or:

esvogt:PASSWORD HERE:2183:129:Novel,,,:/usr/users/advisor/esvogt:/usr/bin/ksh
           \
       password removed

  or you got:

cat: cannot open /etc/passwd

  Then the UNIX you are on is utilizing some other form of protection or may
  be using a different 'passwd'-ing process. Keep reading.

  -AIX-

  On AIX systems, an UNIX variation, the 'passwd' file is in a different
  place. On an AIX type:

booya> cat /etc/security/passwd

  If this lists out a 'passwd' file with the (encrypted) password intact, then
  you've succesfully listed out (stolen) your first 'passwd' file. *Buffer*
  the entire contents to a text file and save it, and jump down to MACCRAC-
  ING. If not, keep reading.

  -NIS/yp-

  Some UNIXes use a system called Yellow Pages [taken from #hack/alt.2600 FAQ
  beta .013]:

    "NIS (Network Information System) is the current name for what was once
    known as yp (Yellow Pages).  The purpose for NIS is to allow many
    machines on a network to share configuration information, including
    password data.  NIS IS NOT DESIGNED TO PROMOTE SYSTEM SECURITY.  If
    your system uses NIS you will have a very short /etc/passwd file that
    includes a line that looks like this:

+::0:0:::

    "To view the real password type this command:"

booya> ypcat passwd

  If 'ypcat' lists a password file with the (encrypted) password still intact,
  *buffer* the entire contents and go on to MACCRAC-ING, if not, keep reading.

  -Password Shadowing-

  Some systems use what is called password shadowing [again, taken from
  #hack/alt.2600 FAQ beta .013]:

    "Password shadowing is a security system where the encrypted password
    field of /etc/passwd is replaced with a special token and the
    encrypted password is stored in a separate file which is not readable
    by normal system users.

    "To defeat password shadowing on many (but not all) systems, write a
    program that uses successive calls to getpwent() to obtain the
    password file.

    "Example:

    -------------------------------------------------------------CUT HERE
    #include
    main()
    {
    struct passwd *p;
    while(p=getpwent())
    printf("%s:%s:%d:%d:%s:%s:%s\n", p->pw_name, p->pw_passwd,
    p->pw_uid, p->pw_gid, p->pw_gecos, p->pw_dir, p->pw_shell);
    }
    -------------------------------------------------------------CUT HERE

  Now then, for those you who are unfamiliar with UNIX scripts and/or their
  implementation, follow these directions:

  First Copy the above script (not including the CUT HEREs) into a Text
  file and save it as 'getp.c'. Next Login to your UNIX account and create a
  directory called 'executables'. (At the prompt) Type:

 prompt       directory name
  /              /
booya> mkdir executables
        /
   make directory

  Now, use Fetch or some other FTP client to FTP into your account and
  Upload 'getp.c' into the directory 'executables'. Once you've done this,
  login to your account, and goto the 'executables' directory:

       change directory
        /
booya> cd executables

  Type 'ls' to List the directory to make sure the file is there. If it is
  you can attempt to compile the 'getp.c' script. Almost all UNIX boxes
  have Compilers, it's just a matter of whether or not you have acces TO
  the Compiler. Typically you do. at the UNIX prompt Type:

prompt   compiler      executable
  \     /             /
booya> cc -o getp.c getfile
          /     \
    output      filename
    option

  If you don't get an error you should be left with a file named 'a.out'.
  Type:

booya> a.out

  If you get a listing with the (encrypted) password intact, *buffer* the
  contents to a text file and go on to MACCRAC-ING. if not, keep readin'.

  If you got an error when you tried to compile the 'getp.c' script: 'cc:
  Command not found' then you either don't have that compiler or you don't
  have access to it. In either case, try compiling with the GNU C Compiler:

         gnu c compiler
         /
booya> gcc getp.c
              \
             filename

  Again, you should be left with a file named 'a.out'. At the UNIX prompt
  type: a.out. If you get a password file with the (encrypted) password file
  intact, *buffer* the entire contents and go on to MACCRAC-ING. If not, keep
  reading.

  -Last Resorts-

  In some cases none of the above listed attacks may work. It might be because
  you're running a newer version of UNIX like SunOS v5.4. Also it, may just be
  that you don't have permissions to access the 'passwd' file for whatever
  reason.  In the case of SunOs v5.4, v5.4 doesn't have those helpful v4.1.x
  bugs so well documented in the CERT Advicories. In this case your best bet
  may be to go pick up a book on UNIX (so you can know what you're doing), and
  then goto the Bugtraq Archives:

  http://www.eecs.nwu.edu/~jmyers/bugtraq/search.html

  ...and do a search for 'SunOS 5.4'. Any vulnerabilities in 5.4 (or any other
  system for that matter) may be found there.

  In cases where you just don't have access to the 'passwd' file for whatever
  reason, you might try the 'Dumb User' Hack: Login to a UNIX using whatever
  account you have. Once you're logged in, at the prompt type:

      change directory up 1
           /
booya> cd ..
         ^
         Note space ' ' between 'cd' and '..'

booya> ls
        \
     lists contents of directory     accounts
                                     /     \
1031exch        dianafcr        jetski91    \   mikesotto       sanders
aa7bq           diane           jgroff       \  milton          saucy
aacker          digna           jhill         \ mjwright        sawgal
aardvark        dillon          jillk           mkansgen        sbarnes
acarr         / ditomaso        jimfinly        mmadison        sbray
     \       /
     accounts                    [ALL of these are accounts]

[etc...]

  What this process does is give you the names of all the common accounts on
  the UNIX you're on. Buffer this list and print it out. Exit the UNIX (type:
  exit) and try to Hack back using these accounts with the Account name as the
  password. i.e.:

UNIX(r) System V Release 4.0 (arthur)

login: jetski91
Password: jetski91 -- would not be shown
Login incorrect     /
login: mkansgen    /
Password: mkansgen
Last login: Sat Jan 27 12:34:31 from slip212m.vinue.net
Sun Microsystems Inc.   SunOS 5.4       Generic July 1994
You have new mail.
Sat Jan 27 12:41:04 MST 1996
/usr/users/mkansgen
arthur{mkansgen}/usr/users/mkansgen%

  This is the 'Dumb User' Hack. Because a user was 'dumb' enough use his
  account name for his password, it was easily hacked, and now that dummy's
   account is your's. If the Dumb User's account has more privileges than
  yours (i.e. Permission to read the 'passwd' file), go back through the
  previously described methods and attempt to get the 'passwd' file. If the
  account has no greater privileges, keep the account for later trading on
  #hack and try and hack another account with more privileges.

  If you've tried everything and you still haven't succeed in stealing a
  'passwd' file, goto bed and thank God you don't have more troubles in life.

 MACCRAC-ING

  At this point you should have a processable 'passwd' file. This file should
  contain account entries with the encrypted password intact, and it should be
  saved as a plain text file. If these are completed you can proceed with
  using MACCRAC.

  Now to use MACCRAC there a couple of operating mechanics to go over.
  Remember MACCRAC is a ported version of an IBM program, and since this is a
  BETA, its still a little buggy, and frills free. Basically, there are four
  main components of MACCRAC:

  MacCrac.FAT--This is the main MacCrac application which processes
               and crack's UNIX 'passwd' files.

  MacCrac.Log--This is the file where all information generated during the
               process off cracking a UNIX 'passwd' file is stored.

  DICTIONARY--This is a dictionary file containing words MACCRAC will use
              to try and crack a 'passwd' file.

  passwd--This the file that contains the UNIX account information.

  Important notes on the above:

  MacCrac.FAT
  -----------
  MACCRAC REQUIRES that ALL FILENAMES MUST BE AS THEY ARE LISTED ABOVE! There
  will be no dialogs to ask you which DICTIONARY or 'passwd' file you wish to
  use. MACCRAC Will look ONLY for a Dictionary file called DICTIONARY and a
  UNIX 'passwd' called passwd, AND it will only look for them in the immediate
  folder it is in, so make sure these files are in the same folder with
  MACCRAC.

  Dictionary
  ----------
  The DICTIONARY is a standard Word Processing Dictionary as used by say,
  Microsoft Word. MACCRAC's Dictionary is somewhat larger than most Word
  Processoing Dictionaries with a size 2,431k. But other than it's size, it's
  no different.  Dictionary files consist of alphabetized words with one word
  per line (carriage return) and no spaces. Heres a short sample of a
  DICTIONARY file:

  A
  a
  aa
  aal
  aalii
  aam
  Aani
  aardvark
  aardwolf

  Now, at 2,413k, MACCRAC's Dictionary is fairly large...although certainly
  not the largest. I personally have seen Dictionary files as large as 4
  gigabytes! But normally you won't need a Dictionary that big. In fact the
  DICTIONARY file that comes with MACCRAC should be more than adequate. But if
  you would like to use a larger Dictionary or would like to use a Dictionary
  of say, Foreign Words, or Star Trek Terms, or Dog Names, then you can either
  make them or, find them on the internet.

  In using these Dictionary files, it's important to remember that what ever
  name they're called when you find them, they MUST be RENAMED to DICTIONARY,
  and placed in the same Folder as MACCRAC in order to be used. If the
  Dictionary file is not called DICTIONARY, or is not in the same Folder as
  MACCRAC, it will not/cannot be used.

  As a final note on Dictionaries, there is a program called 'Word List
  Maker'. This is a Drag&Drop program which allows you to Drag two or more
  Dictionary files on to it, and it will combine them into a single Dictionary
  AND delete all duplicate entries. This is great for making custom, or more
  extensive DICTIONARY files for MACCRAC to use. Keep in mind though, that the
  larger the Dictionary, the slower the process.

  passwd
  ------
  Well the 'passwd' file is what we spent the majority of this Tutorial
  discussing, so I shouldn't need to go into it much here. The most important
  thing to say about the 'passwd' file at THIS point is that included with
  MACCRAC is a file called 'passwd'; DELETE IT! This is just a sample file
  included with MACCRAC probably for Development or Testing purposes. It will
  do you no good. Replace it with your newly acquired 'passwd' file, and make
  sure this newly acquired file is called: passwd. Also make sure it's in the
  same Folder with MACCRAC

 LET'S DO IT

  Well, f you have your 'passwd' file, and you have whatever Dictionay file
  you're going to use, and all of the files are correctly named and placed in
  the same Folder with MACCRAC, then I guess you're ready, so lets do it!

  For the sake of speed, and because you won't be able to use your computer
  anyway, I suggest Restarting your Mac with Exensions Off (even if you have
  RamCharger or RamDoubler). Once you've restarted, Double click on the
  MACCRAC icon. If this is your first time running MACCRAC, just go up to
  'Crack' in the menubar and select: Start Cracking!. The first thing you'll
  probably notice is that once you've started a Cracking Session you can't do
  anything else. Thats because MACCRAC hogs the processor. I would suggest
  starting a session around 11:00 pm and letting it run all night. By morning,
  it should have cracked at least 40-50 accounts.

  If for some reason you want or need to stop a session before an entire
  'passwd' file is cracked, the only way to do it is with COMMAND-OPTION-ESC.
  Don't worry, any cracks MACCRAC has cracked to that point will be saved.

  If you've already started Cracking a 'passwd' file but had to quit, you can
  pickup where you left off by going up to the 'CRACK' menubar and dragging
  down to Settings. Once in Settings select 'Recover session from "Point
  File"'. Now you can 'Start Cracking!' where ever you let off.

 OUTRO

  If you've let it run long enough, you should have passwords. At this point
  you're on your way to geting to "ROOT". The topic of Hacking "root" on UNIX
  has been addressed by any of a number of well written, informative and
  readily available T-Philes on UNIX Hacking. At this point I suggest you
  pursue them as this file will not address that topic (remember, this is a
  Tutorial on MACCRAC)

  I'd like to thank Disorder, Voyager and the rest of TNo Crew for their
  incite and assistance. That's it for this one. Look for more oleBuzzard's T-
  Philes on the World's Greatest Underground Mac Board...


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