Re: In-kernel Authentication Tokens (PAGs)

[Chris Wright <chrisw@osdl.org>]

* Kyle Moffett (mrmacman_g4@mac.com) wrote:
> On Jun 12, 2004, at 17:44, Chris Wright wrote:
> > Typically, objects that LSM cares about include a pointer to opaque
> > data (security blob) which describes the security domain for the 
> > object.
> > See task->security as an example.  It's not clear to me if 
> > task->security
> > is sufficient and you only need a back pointer to the task or if each
> > PAG needs it's own security blob.
> 
> Ahh, ok.  In this case, a PAG is an independent object, not directly
> associated with any specific task or other PAG, so therefore it will 
> likely
> need its own security blob.  Currently, in the creation of my PAG I just
> copy over the UID from the calling task.  If I was to convert it to use 
> LSM,
> I guess I should just leave out the UID entirely, and just have a 
> pointer
> to a security blob.  What is the best way to portray the security blob 
> to
> user-space, in terms of sys-calls?  I need a way for user-space apps to
> change the security context in a similar way as it is changed for a task
> or process.  Do you have a link to some documentation on the kernel
> API for LSM?  I basically need to copy the current task's security blob
> into a new one and be able to compare two contexts to see if one
> can affect the other.  Thanks!

I don't have a good feel for the PAG data structure, perhaps the
above would turn out as overkill.  The security api is commented in
include/linux/security.h, take a gander there.  The blobs are specific
to the security model, and I don't yet see a need to display them to
userspace for each PAG.  

> > Sounds like an extension to rlimits.  The counters could be stored in
> > ->user to limit the userwide number of tokens.
> 
> Ok, thank you very much, that's exactly what I need.  I am somewhat
> new to kernel development, so finding my way around the structs is
> somewhat difficult.  Is there a good guide somewhere on the net that
> you can point me to?

Hmm, not really.  The source is best.

thanks,
-chris
-- 
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