Process arguments

[Robert Watson]

On Mon, 30 Oct 2006, Dave Clausen wrote:

> I'm a n00b to the FreeBSD kernel and I'm trying to log all commands run on 
> the command line from within the kernel for security purposes by loading a 
> kernel module which redefines execve().  I've successfully created the KLD 
> and have it working, but am having problems saving the command's arguments. 
> Could anyone point me to where in the kernel I should be looking for the 
> arguments sent to the process?  p->p_args gives me the parent process's 
> cmdname only (sh, in this case), and uap->argv is just the relative pathname 
> of uap->fname.  Ideally, I'd like the user, full command line, and cwd 
> logged for each command entered.

As of FreeBSD 6.2, you can use our security audit subsystem to do this. 
There's a FreeBSD handbook chapter with the details, but the short version is:

- Enable options AUDIT in your kernel.  This enables kernel audit support.

- Add auditd_enable="YES" to /etc/rc.conf.  This turns on the audit daemon.

- Modify the flags and naflags entries in /etc/security/audit_control to be
   lo,+ex -- the +ex means "log successful executions".

- Add ,argv to the policy line in /etc/security/audit_control.  This causes
   auditing of the full command line, not just the program run.

- Reboot.

You can then extract complete command lines (among other things) from trails 
in /var/audit, or watch them live by running praudit on /dev/auditpipe.

FYI: Audit support is considered experimental in 6.2, as there are some areas 
that need testing and/or are not complete.  However, it works quite well in 
practice, and any feedback would be most welcome.

Robert N M Watson
Computer Laboratory
University of Cambridge

>
> Here's an example of what I've been working away on:
>
> int
> new_execve (struct thread *td, struct execve_args *uap)
> {
>      char *user;
>      struct proc *p = td->td_proc;
>
>      user = p->p_pgrp->pg_session->s_login;
>      if (p->p_ucred->cr_ruid == 1001) {
>              printf("%s %d %s\n", user, p->p_pid, uap->fname);
>      }
>      return (execve(td,uap));
> }
>
> Running 'ls -al' with the above, I get the username, pid, and absolute 
> filename printed such as, but can't find the actual arguments:
> dave 6689 /bin/ls
>
> Any help would be appreciated.
>
>
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