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RE: selinux_socket_bind hook



Stephen Smalley wrote:
> On Thu, 2005-04-28 at 12:32 -0400, Steve Brueckner wrote:
>> In trying to segment networking into two domains I seem to have
>> overlooked that name_bind doesn't get enforced for ports within the
>> machine's local port range (i.e. ports assigned by the kernel).  I
>> suppose I could try to hack the LSM selinux_socket_bind hook to
>> enforce name_bind for all ports; would that be possible?  I'd rather
>> not, though, since I've never ventured deeper than SELinux policy,
>> and delving into the mechanism scares me.  Is it possible to somehow
>> implement a boolean that would toggle whether name_bind was enforced
>> for all ports or just for ports outside the local port range?
> 
> That hook is only applied for explicit bind(2) calls by applications.
> auto-binding of unbound sockets by the kernel (e.g. when sending on
> an unbound socket) will never hit that hook at all.  You would need
> to modify udp_v4_get_port and tcp_v4_get_port to check permission and
> keep scanning for another available port until one is allowed.  Not
> likely to make much headway upstream.     

Darn.  But thank you for the clarification.

 - Steve Brueckner, ATC-NY


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