kern/68189 and kern/169751: what jails are allowed to see in a routing socket

[Bjoern A. Zeeb]

On Wed, 2 Jan 2013, Jamie Gritton wrote:

> I've been looking at PR kern/169751, which was noting that routing sockets 
> don't work inside a jail.  It made the point that setting 
> security.jail.socket_unixiproute_only or security.jail.allow_raw_sockets 
> didn't help things.  It would seem kind of a given from the "unixiproute" 
> name that a route socket ought to work.  And indeed, such a socket is 
> permitted to be created in such a jail.  It's just using it that doesn't 
> work.
>
> I narrowed this failure down to line 816 of sys/net/rtsock.c, which 
> explicitly denies jails from reading routes, regardless of the setting of the 
> above two sysctls (or the jail allow.* bits they work with).  And that bit of 
> code came about in response to PR kern/68189, which noted that jails could 
> see interfaces that aren't theirs (i.e. their address doesn't live on it).
>
> So we have two PRs that are kind of at cross purposes.  It would be nice to 
> keep hiding non-jail interfaces from a jail, but it would also be nice to let

jails have no notion of interfaces, only addresses, so by defintiion
there cannot be "non-jail interfaces".


> a jailed process know the route to somewhere - at least sometimes.  One 
> solution would be to add a much finer layer of control to the jail test in 
> rtsock.c, looking at interfaces and seeing if they're somehow connected with 
> one of the jail's IP addresses.  But that just seems like a lot of messy 
> corner-case code.
>
> Another way around this, and what I'd like to go with if there are no 
> objections, is to allow the route sockets to be used by jails that have 
> raw_sockets permission.  I know that's kind of a semantic leap, but it seems 
> that a jail that has the power of using raw sockets would be able to do 
> pretty much as it pleases with routes anyway if it tried hard enough.  Also, 
> it would be consistent to allow such operations on jails that aren't 
> IP-restricted, or in VIMAGE jails.

I have not further looked at the code but the answer is that we should
not further complicate jails after 14 years when we have a perfect
good solution for the problem;  vnets are there for exactly this.
Someone with enough interest and time should just finish things (tm) ;-)

Meanwhile your suggestion might be ok given simple enough, but I wonder
if a different flag would be helpful still.  I would not be able to
"trust" (the little that is possible anyway) raw_sockets anymore if they
suddently could fiddle with the routing table - even read-only, should
that really be enough.
I would explicitly advertise it as 'do not use - will go away again'
feature and it should the moment vnets are declared non-experimental.

Just my 2cts.

/bz

-- 
Bjoern A. Zeeb                                 You have to have visions!
          Stop bit received. Insert coin for new address family.