linux-kernel - Re: [PATCH 08/28] SECURITY: Allow kernel services to override LSM settings for task actions [try #2]

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Date:	Tue, 18 Dec 2007 21:39:33 -0800 (PST)
From:	Casey Schaufler <casey@...aufler-ca.com>
To:	Crispin Cowan <crispin@...spincowan.com>,
	Stephen Smalley <sds@...ho.nsa.gov>
Cc:	David Howells <dhowells@...hat.com>,
	Karl MacMillan <kmacmill@...hat.com>, viro@....linux.org.uk,
	hch@...radead.org, Trond.Myklebust@...app.com,
	casey@...aufler-ca.com, linux-kernel@...r.kernel.org,
	selinux@...ho.nsa.gov, linux-security-module@...r.kernel.org,
	apparmor-dev <apparmor-dev@...ge.novell.com>
Subject: Re: [PATCH 08/28] SECURITY: Allow kernel services to override LSM settings for task actions [try #2]


--- Crispin Cowan <crispin@...spincowan.com> wrote:

> Stephen Smalley wrote:
> >> It is if I have to maintain a special pieces of code for each possible
> LSM.
> >> One piece for SELinux, one piece for AppArmour, one piece for Smack, one
> piece
> >> for Casey's security system.  That sounds like a pain.

It's probably less of a pain if you consider that Casey's
security scheme is Smack.

> > All your code has to do is invoke a function provided by libselinux.  If
> > at some later time a liblsm is introduced that provides a common
> > front-end to a libselinux, libsmack, ..., then you can use that.  But it
> > doesn't exist today.   But it all just becomes a simple function call
> > regardless.
> >   
> libapparmor exists. It only had one API, and now it has 2, but just 2
> versions on the same concept (change_hat and change_profile).
> 
> This is the API for change_hat http://man-wiki.net/index.php/2:change_hat
> 
> What does the corresponding API in SELinux look like?

The POSIX mac_set_proc(mac_t label) might work for this interface.
Sets the current process MAC attribute, if appropriate. The Smack
implementation would be pretty easy:

typedef char * mac_t;

int mac_set_proc(mac_t label)
{
        int fd;
        int rc;

        rc = strlen(label);
        if (rc > SMACK_MAX_LABEL_LEN)
                return -1;
        fd = open("/proc/self/attr/current", O_RDWR);
        if (fd < 0)
                return -1;
        rc = write(fd, label, rc);
        close(fd);
        if (rc < 0)
                return -1;
        return 0;
}


Casey Schaufler
casey@...aufler-ca.com
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