/lib/ld-2.2.4.so

[Sabau Daniel <draven () UBBCluj Ro>]

or:
lrwxrwxrwx    1 root     root           11 Apr 15 12:01 /lib/ld-linux.so.2 
-> ld-2.2.4.so

        This file gives users the ability of running binaries on witch the 
user doesn't have the permission to execute, it is enough to have read 
ability on the file in order to execute it:

-rwxr-xr--    1 root     root        45948 Aug  9  2001 /bin/ls

but using the /lib/ld-2.2.4.so file i can execute the ls command:

[08:51:36][draven@Zero:~]:$/lib/ld-2.2.4.so /bin/ls /
bin   bzImage   bzImage3  bzImage5  dev  home    lib   mnt  proc  sbin  
usr
boot  bzImage2  bzImage4  bzImage6  etc  initrd  misc  opt  root  tmp   
var

i do not have root preveleges on this account:

[08:51:38][draven@Zero:~]:$id
uid=1000(draven) gid=10(wheel) groups=10(wheel),16(trust)

The most interesting part is running binaries on partitions mounted with 
noexec, lets take this partition:

/dev/sda9 on /home/friends type ext2 
(rw,noexec,nosuid,nodev,usrquota,grpquota)

i've created a shell acount with the home directory:

[mjj@Zero mjj]$ pwd
/home/friends/mjj

and wrote this C code in a file test.c

#include <stdio.h>
void main(void)
{
        printf ("Test");
}

i've compiled it & tryed to run:

[mjj@Zero mjj]$ ./a.out
bash: ./a.out: Permission denied

but when i try to run it with /lib/ld-2.2.4.so:

[mjj@Zero mjj]$ /lib/ld-2.2.4.so ./a.out
Test

the important thing is to include a full path in the binary name to be 
able to execute it.
in the same way i've managed to run the ptrace exploit on a nosuid 
partition
i'm running a 2.4.18 kernel with grsecurity-1.9.4 patch on a Red Hat 
Linux 7.2 box, but i've succeded running this file on different linux 
boxes and i've been succesfull, please if anyone know how to eliminate 
this hole in my security give me a replay. If i try to change the mode on 
/lib/ls-2.2.4.so to 700, the users will not be able to login on my linux 
box, so this is not a solution:)

10x,
Dan Sabau


-- 


"From all the things I lost, 
My mind, I miss the most!"

echo '16i[q]sa[ln0=aln100%Pln100/snlbx]sb20293A2058554E494Csnlbxq'|dc