Chapter 16. Building Your SMB Vocabulary

...they have weapons of mass confusion and aren't afraid to use them.

iomud on Slashdot

Looking back over our shoulders, we see that we have performed only two SMB exchanges so far: the NEGOTIATE PROTOCOL and the SESSION SETUP . There may be a TREE CONNECT shoved into the packet with the SESSION SETUP as an AndX, but we haven't really described the TREE CONNECT in detail.

So, although we have covered a tremendous amount of material, our progress seems rather pathetic doesn't it? What if the rest of SMB is just as tedious , verbose, and difficult?

Relax. It's not.

Certainly there are other difficulties lying in wait, but the biggest ones have already been identified and we are carefully avoiding them. If you pursue your dream of creating a complete and competitive CIFS implementation then you may, some day, need to know how things like MS-RPC and Extended Security really work inside. Fortunately, you can do without them for now.

Let's just be clear on this before we move along:

There is a lot you can do with CIFS without implementing any of the extended sub-protocols that SMB supports, but if you want to build a complete and competitive CIFS client/server implementation you will need to go well beyond the SMB protocol itself.

That's why it has taken the Samba Team (with help from hundreds if not thousands of people across the Internet) more than ten years to make Samba the industrial-strength server system it is today. Tridge worked out the basics of NBT and SMB in a couple of weeks back in 1991, but new things keep getting tacked on to the system.

When implementing CIFS, the rule of thumb is this: Implement as little as possible to do the job you need to do.

The minute you cross the border into uncharted territory, you open up a whole new world to explore and discover. Sometimes, you just don't want to go there. Other times, you must.

Anyway, in the spirit of keeping things simple we will cover only a few more SMB messages, and those in much less depth than we have done so far. There really is no need to study every message, longword, bit, and string. If you've come this far, you should know how to read packet captures and interpret the message definitions in the SNIA doc. It is time to take the training wheels off and learn to ride .