Samba under Coherant and Macintosh

Andrew Tridgell tridge at
Fri Dec 17 04:39:55 GMT 1999

> you're looking for reasons not to support nmb-agent, and those same
> reasons apply to nmbd [invalid requests, overflows, go-slow-attacks],
> therefore they don't apply.

As I explained to Luke on the phone this morning, there is a critical
difference - nmbd uses SOCK_DGRAM whereas nmb-agent uses
SOCK_STREAM. By using SOCK_STREAM you open yourself up to lots of
these nasties. and, in case you wonder, just changing it to SOCK_DGRAM
doesn't solve all your problems, it just adds different ones.

also, nmbd has a pile of code to be paranoid about the format of
packets. It carefully checks packets to make sure they are
valid. nmb-agent doesn't do that.

I think I've finally convinced Luke to drop nmb-agent. The next step
is for me to get moving on the database stuff so we have something to
replace it with.

> andrew, you just don't get it.
> do you really, really want an anomymous user to run an msprc service as
> root?  the answer, is a most definite, absolute no way.

I do get it Luke. I hope my conversation with you this morning
clarified things for you. If not then I'm pretty close to giving up
with explaining it. 

Your reason for running it as non-root is so you can launch new
services as an anonymous user. I won't allow that anyway - we are not
going to have Samba turn into a rexec replacement. "magic script" was
a mistake that I've regretted, I'm not going to repeat it.

The only other reason you seem to have is some mythical deep-seated
notion that things run as non-root are magically secure. They

> i just can't bring myself to not put in become_user() calls.  i really
> can't.

get over it. Doing become_user() calls in this case will _lower_ our

It is a common security misconception that running as non-root is
always better - it is only better in some cases and this isn't one of
them. I particularly want you to code this for running as root as it
will hopefully make you more paranoid when writing the code. Your
conviction that running as root is dangerous can be turned into an
advantage that way.

> why is it that you think that msrpc services don't need to do file access?
> what about access to private/smbpasswd from samrd?

we do become_root() before those anyway, so thats totally
irrelevant. (the smbpasswd can _only_ be accessed as root).

> do you want anonymous users to be able to read the SAM database,
> just like NT allows?

of course not, but doing become_user() won't stop that. It will just
give you a false sense of security.

> i'm into expanding the possibilities, and at the moment it looks like
> you're into closing them all because they sound, to you, really crazy.

don't add features without good reasons. Keep the code simple. Don't
use sham security measures that end up adding complexity and lowering
real security. Above all, think of the maintainability of code before
writing it.

Cheers, Tridge

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