[Lustre-devel] security: MGS connection

Peter Braam Peter.Braam at Sun.COM
Wed Jun 4 11:49:40 PDT 2008

We clearly need to make sure that servers can enforce a level of security
for clients - even if it is ugly to do so.


On 6/4/08 11:38 AM, "Eric Mei" <Eric.Mei at Sun.COM> wrote:

> Eric Barton wrote:
>>> Here is the user interface change according to previous discussion,
>>> please review:
>>> - The security flavor of MGS connection is determined by each node, not
>>>   controllable by MGS.
>> Is this an unavoidable fact of life or a design decision?
> I think it's not completely unavoidable. For example, MGC can do initial
> connect without protect, and tell MGS what kind of security mode it
> support, and MGS replay with its decision, and MGC reconnect with
> choosed flavor.
> This way will be much more complicated. And more importantly, what if
> someone hijack the initial non-protected connection? Things seem not
> getting any better...
>>> - By default there's no protection.
>> See below "XXX"
>>> - Given the GSS/Kerberos env is ready, mount option "mgssec=flavor"
>>> could be supplied. Pre-configured machine credential will be used, so no
>>> need to supply password or whatsoever.
>>> - For MDT/OST, the option "mgssec=flavor" could also be written on disk,
>>> like other parameters, but will be override if mount option supplied.
>>> - The flavor of MGS connection won't change until umount, no matter how
>>> rest of connection flavors change at runtime.
>>> - MGC->MGS connection is one per node, so only one flavor could be used.
>>> For example, suppose 2 OSTs live in a single node, we do:
>>>    # mount -t lustre -o mgssec=krb5p /dev/sda1 /mnt/ost1
>>>    # mount -t lustre -o mgssec=null /dev/sda1 /mnt/ost2
>>> then only 'mgssec=krb5p' will take effect, the second 'mgssec=null' will
>>> be ignored.
>> I don't think it's acceptable to allow a previous mount to compromise
>> the security of a later mount.
> Indeed it looks not so good. But the fact of per-node shared MGS
> connection means only one flavor could be used. To avoid the confusion,
> to me the only way is don't allow the choice via mount option, instead
> to choose a "proper" one automatically somehow.
>> XXX
>> This raises the interesting question of whether servers (MGS included) can
>> demand a minimim level of security from clients connecting to them.  Is this
>> normally part of configuring security on a given node (e.g. to set the
>> machine credentials you mentioned above)?
> This is the root problem I guess: we can't assume there's security
> environment ready on each nodes.
> The procedure of setup gss/kerberos is not extremely easy: configure
> KDC, installing keytabs, configure gssapi, keyring, etc. And for most
> Luster clusters, strong security are not needed at all, so people most
> likely choose to skip that.

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