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[Freeipmi-users] IPMI-DCMI Q

From: dan farmer
Subject: [Freeipmi-users] IPMI-DCMI Q
Date: Tue, 19 Jul 2016 23:01:03 -0700

Hi folks -

I recently came across something that is implemented and documented in 
freeipmi, but I had a question or two about it nonetheless.

It appears that the Get DCMI Capabilities Info Command (from the DCMI spec) is 
intended to be similar to the get auth of IPMI; indeed the spec says "The 
command is session-less and can be called similar to the Get Authentication 
Capability command.” Session-ess being the key here… and again in the platform 
command table (chapter 6 in v1.1 & 1.5) they specifically call it out as being 
session-less and "Command can be executed at any privilege level and is 
available before and after establishing a session.”

Does anyone ask if this un-authenticated call is generally implemented that way 
or not?  It certainly works fine with authentication. Or does anyone know of a 
tool or example that does this in an unauthenticated fashion?

The reason I’m asking is because I *think* I’m sending the correct packet out 
RE: the spec, but I’m not getting a response… and it could be my packets suck 
and there’s a byte transposed or something, but I’m finding it difficult to 
tell because (a) I can’t find a sniffer who understands the protocol to see if 
I’m sending it correctly, (b) I can’t (easily, and in general) get onto the BMC 
that is receiving the packet and see what’s going on there, and (c) 
freeipmi/ipmi-dcmi doesn’t appear to allow you to send packets without starting 
up a session first (please add unauthenticated packet sending, and I’m not 
talking auth type NONE!), so while I see the packets from the tool they’re 
authenticated and hence different.

The difference in the packets is in two places; the auth info, sequence #, and 
the checksum at the end (all one stream with some spacing to hopefully help 

Working authenticated ipmi-dcmi payload:

        0600ff07 02ce808500510000000ca9369cb60f13a2c4a7ece6dcb5d6ce0 
                 ^^^     this is the authtype and auth info     ^^^^

My lame payload:

        0600ff07                0000000000000000000                  

Anyway, in the hopes that someone sees something obvious or knows more about 
it… I only have a server or two to test this with as some just don’t support 
the protocol.

Thanks and hope all is well in ipmi-land -


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