Re: Auditing the "chattr" command (ioctl syscall?)
On Wednesday, August 24, 2011 09:57:13 AM Max Williams wrote:
Hi,
I would like to be able to audit the syscalls that the chattr command uses
but I'm not having much luck. In an effort to see the syscalls used, I
created a rule to log all syscalls, like this: # auditctl -a exit,always
-F path=/root/file
Then run this:
# chattr +i /root/file
This produces series of two syscalls in the logs, 6 (sys_newlstat) and 2
(sys_open): node=localhost.localdomain type=SYSCALL
msg=audit(1314189320.335:53158): arch=c000003e syscall=6 success=yes
exit=0 a0=7ffff0f8886c a1=7ffff0f88250 a2=7ffff0f88250 a3=1 items=1
ppid=15560 pid=15745 auid=0 uid=0 gid=0 euid=0 suid=0 fsuid=0 egid=0
sgid=0 fsgid=0 tty=pts0 ses=1198 comm="chattr" exe="/usr/bin/chattr"
key=(null) node=localhost.localdomain type=SYSCALL
msg=audit(1314189320.335:53160): arch=c000003e syscall=2 success=yes
exit=3 a0=7ffff0f8886c a1=800 a2=7ffff0f88170 a3=1 items=1 ppid=15560
pid=15745 auid=0 uid=0 gid=0 euid=0 suid=0 fsuid=0 egid=0 sgid=0 fsgid=0
tty=pts0 ses=1198 comm="chattr" exe="/usr/bin/chattr" key=(null)
I don't think these are the syscalls I want to audit,
nope. You can use the autrace program also and get a strace like list of syscalls made
by the process.
they would be far too
frequent. I also noticed when I run a strace on the chattr command it
looks like it uses ioctl, eg: ioctl(3, EXT2_IOC_SETFLAGS, 0x7fff0314cf3c)
What audit rule could I use to achieve this?
It starts off like this:
-a always,exit -F arch=b64 -S ioctl
Then you need to look at the man page for ioctl. The first argument is the FD, so you
will not have a a0 since that could be different from program to program. Then you
need to look in the header files for the definition of EXT2_IOC_SETFLAGS.
/usr/include/linux/ext2_fs.h
#define EXT2_IOC_SETFLAGS FS_IOC_SETFLAGS
/usr/include/linux/fs.h
#define FS_IOC_SETFLAGS _IOW('f', 2, long)
/usr/include/asm-generic/ioctl.h
#define _IOW(type,nr,size) _IOC(_IOC_WRITE,(type),(nr),(_IOC_TYPECHECK(size)))
#define _IOC(dir,type,nr,size) \
(((dir) << _IOC_DIRSHIFT) | \
((type) << _IOC_TYPESHIFT) | \
((nr) << _IOC_NRSHIFT) | \
((size) << _IOC_SIZESHIFT))
# define _IOC_WRITE 1U
Looks hard to figure out? Let's make a program:
#include <stdio.h>
#include <linux/fs.h>
#include <linux/ext2_fs.h>
int main(void)
{
printf("%0lX\n", EXT2_IOC_SETFLAGS);
return 0;
}
It returns this: 40086602
So, the rule is:
-a always,exit -F arch=b64 -S ioctl -F a1=40086602
I don't know if the syscall requires more arguments. You would have to look at the
chattr program for more. Also note that you might want a matching b32 rule also. If
you wanted to limit this to a file, then put a -F path= on that also. Adding a key field
helps in searching later.
-Steve