handle error 0xC0000203 in SMB_COM_SESSION_SETUP_ANDX

[thomasleveil]

We sometimes hit a ProtocolError exception with :

Unknown status value (0xC0000203) in SMB_COM_SESSION_SETUP_ANDX (with extended security)
==================== SMB Message ====================
Command: 0x01 (SMB2_COM_SESSION_SETUP) 
Status: 0xC0000203 
Flags: 0x01 
PID: 10 
MID: 2 
TID: 0 
Data: 9 bytes 
b'090000000000000000' 
==================== SMB Data Packet (hex) ====================
b'fe534d4240000000030200c001000100010000000000000002000000000000000a000000000000000100008800fc020000000000000000000000000000000000090000000000000000'

looking at the code here, it seems the 0xC0000203 could be handled and call self.onAuthFailed().

---

From Microsoft doc :

NT status value	Description
0xC0000203 STATUS_USER_SESSION_DELETED	The user session specified by the client has been deleted on the server. This error is returned by the server if the client sends an incorrect UID.

session: In Server Message Block (SMB), a persistent-state association between an SMB client and SMB server. A session is tied to the lifetime of the underlying NetBIOS or TCP connection.

[miketeo]

You are correct in your assessment. That status code looks like it can be handled in a more user-friendly manner.
But I'm interested to learn what can lead to this status code. After all, it does not appear to a common scenario when the remote service will simply delete the user session. If an incorrect UID is sent, then there could be a bug lurking somewhere in the code.

[thomasleveil]

well, I don't really know. I found this error in our newly installed Sentry. I can't tell yet how frequently this happens. I'll remember to update here if it is the case.

My best guess is that it could be a restart of the service.

[thomasleveil]

This error occurred again today. Unfortunately, I cannot reproduce it consistently and can't figure out why it occurs

[thomasleveil]

it happened again today

[miketeo]

@thomasleveil : Can you provide a few details about your task?

1. Are you using one pysmb session to perform multiple file uploads/downloads?
2. Does the error occur on the first file upload/download? If it happens like after a dozen operations, I suspect there could be some form of connection throttling.
3. If possible, can you log some info of each file operation in terms of file size and duration of each upload/download? When the error occurs next time, is there any abnormal trends in that current upload/download operation? For instance, larger file size, prolonged duration, etc.

[thomasleveil]

Thanks @miketeo for the attention. Next time it happens I'll will take a closer look at operations the code is trying to run.

Would you recommend opening a new connection for each individual operation ?

[thomasleveil]

@miketeo, I've got another occurrence this morning. Looking at the code, we can have up to 5 calls triggered at the same time, in different threads.
Each call will :

1. connect & auth to smb
2. for path in [<list of 4 dir paths>]: recursive call to conn.listPath(...)

One of the calls is failing at connection time

[miketeo]

I suspect that you might be opening "too many" connections at one time. I had similar occurrences when I run the full regression test suites against a Windows 10 workstation.

I'm assuming each pysmb connection is running in its own thread.
A possible workaround could be to catch the exception and introduce a couple of seconds delay before reconnecting again in your step 1.