Re: [NSE] Several changes to mssql.lua and SQL Server scripts

[Chris Woodbury <woodbusy () gmail com>]

On Sat, Feb 12, 2011 at 6:43 AM, Patrik Karlsson <patrik () cqure net> wrote:
> * To me, it was not obvious that the ms-sql-discover script needs to be run in order to get any result from the 
> ms-sql-info script.
>  As the dependencies are not "forced", and there's currently no way of achieving this, it requires the user to 
> specify both scripts each time which isn't very clear.
>  I would personally prefer being able to run just ms-sql-info to be able to retrieve the version information from the 
> instances.

Seeing your changes, I agree that it seems cumbersome to have to run a
separate script just to do discovery. As I see it now, I think it
would make the most sense to implement all of the discovery
functionality in mssql.lua instead of in ms-sql-discover, and to have
discovery be done on a per-host basis, within mssql.lua, and be
triggered by whichever ms-sql-* script runs first. The main changes
would be that discovery_performed would have to be tracked per-host,
and Helper.GetInstanceByName() would check to see if discovery had
been performed already (right now, if you run multiple scripts, each
one does SSRP discovery). While we're on that subject, how about
renaming GetInstanceByName() to something like GetTargetInstances()?
Depending on the circumstances and script arguments, it might be
getting the instance by name, by port, by pipe name, or all that are
available.

> In my personal opinion, I think that may be a little bit too complicated and I'm leaning more towards a instance 
> oriented approach rather than a port oriented.

I agree; this makes a lot of sense.

> Taking ms-sql-query as an example I see the following use cases:
> 1. I want to run a query against a default instance running on port 1433
> This currently isn't a problem at all as the portrule will match port 1433 and run the query.
>
> 2. I want to run a query against an instance registered with the browser called INST1 running on port 1435
> This is problematic as the portrule won't match unless port 1435 is detected as ms-sql-s which currently requires a 
> version scan running with a version intensity of 8.
> A quick test running this against a system here takes 64 seconds which is kind of a pain to do each time you want to 
> run a query against that instance.
> Using the combination of ms-sql-discover and ms-sql-query this could be achieved through the following command:
> sudo ./nmap -sT -sU -p T:1435,U:1434 10.0.200.111 --script ms-sql-discover,ms-sql-query 
> --script-args=mssql.scanned-ports-only
>
> 3. I want to run a query against an instance on port 1435, that isn't registered with the browser
> This case has the same problem with service detection as described in the second case.
> The ms-sql-discover script fails to detect the port as sql server as it's running on a non default port and the 
> browsers not responding.
> If I'm not totally off here there's currently no other way to query an instance on this port other than going through 
> the tedious service scan.
>
> While this port oriented approach gives the user good control over what Nmap is doing I think it requires the user to 
> know quite a lot of how instances work and are resolved.

Good point. I was focusing too much on use case #4, where I want to do
versioning and run, say, ms-sql-empty-password against all of the SQL
Servers in a Class B.

> Another potential problem would be limiting the execution of a script to a single instance in the case of named pipes 
> as they would be accessed over the same port. I haven't been able to verify this yet though.

Yeah, specifying by port won't work here, since we could have multiple
instances available via named pipes. It's awkward, but we might just
need to have a mssql.instance-pipename script argument.

> Taking a instance oriented approach, where it's up to Nmap (or the script really) to determine the correct ports to 
> use, the commands for the above use cases would end up like this instead:
>
> 1. No change
> 2. ./nmap -p 1435 --script ms-sql-query 10.0.200.111 --script-args mssql.instance-name='SQLEXPRESS'
> 3. ./nmap -p 1435 --script ms-sql-query 10.0.200.111 --script-args mssql.instance-port=1435
>
> I realize that the port argument in the 3rd example is redundant/misleading/strange, but unfortunately necessary as 
> we're running as a host rule at this point.
> I guess that use case 3 could also be achieved through Martin Swende's proposed force patch [3] that would force the 
> script to run against the port supplied using -p.

I'm not completely convinced one way or the other, but I think I might
prefer having an argument like mssql.force (we'd need a better name,
though). It does seem a little goofy/redundant to be putting the port
number in twice, and I can't think of a situation where you would be
running an Nmap scan against several ports, but only want the SQL
Server scripts to target one of them. But, on the other hand, maybe
it's clearer and more consistent to use instance-port to specify it.
Either way, I think the plumbing in mssql will be the same, so it's
just a matter of the user interface.

Our problem would go away, of course, if Martin Swende's patch were
applied. That would be the easiest approach for us :)

> The patch also allows the instance-name to be "all", which will result in all instance being processed by the script.

This is good. The default behavior is conservative, but it's not
cumbersome to get it to run against everything, so we're still in good
shape for use case #4.

I think we would also want to allow a list of instance names to be
given, for added flexibility.

> To me, and perhaps only me?, this approach is clearer even though it will connect to ports outside of the given -p 
> scope. Comments, ideas and suggestions are most welcome.
>
> [1] ms-sql-tcp-port.patch
> [2] http://seclists.org/nmap-dev/2011/q1/325
> [3] http://seclists.org/nmap-dev/2010/q4/543
> [4] ms-sql-connect-by-instance-name.patch
>
> //Patrik

While I'm at it, there are a few other ideas that I wanted to throw out there:
* It seems to me that we're going to end up with 2 or 3 classes of SQL
Server scripts (e.g. discovery, per-instance), each of which will have
the same criteria for when they run. I think it would make sense,
then, to put some functions in mssql.Helper that would generate the
hostrules and portrules, and have the scripts just call those (e.g.
hostrule = mssql.Helper.get_standard_hostrule() ).
* At some point, I think we ought to put some top-level documentation
into mssql.lua that gives an overview of the SQL Server scripts and
lays out the different classes and how the mssql arguments affect them
(e.g. ms-sql-info runs against all instances by default, doesn't use
mssql.username).
* Am I wrong, or is it unnecessary to have 1433 in the portrule? Is it
possible to have a situation in which there is a SQL Server available
on 1433 and to have Nmap not classify it as "ms-sql-s"?


Anyway, I think we're headed in the right direction. Let me know your
thoughts. In the meantime, I'll start working on some of this.

-chris
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