[Freeipmi-devel] adding md2/md5 support

[Albert Chu]

Hey everyone, 

The current API is not perfect for md2/md5 checksum support.  The reason
is that in order to calculate md2/md5 checksums, we need the
lan_msg_hdr, command, and packet checksums to be filled in *first*. 
Then, the md2/md5 authcode is calculated *last*.  This won't work in the
current API b/c we call fill_hdr_session() before calling
assemble_lan_packet().

I see several ways to add md2/md5 support:

1) Pass authtype and password to assemble_lan_packet instead of 
   fill_hdr_session():
   Pro: Easiest
   Con: Messes up nice API

2) fill_hdr_session() copies "password" into the authcode buffer.  
   Within assemble_lan_packet(), recalculate the authentication code if 
   the authtype is md2 or md5.  You can think of this as a "hidden" way 
   to pass the password from fill_hdr_session to assemble_lan_packet.
   Pro: Keeps API nice
   Con: A "work around" solution.  Doesn't sit well with me.  But in
        some respects it is still "clean".  I might feel better if
        someone else feels this is ok.

3) Add a "lan_msg_hdr" and "obj_cmd" parameters to fill_hdr_session().
   Pro: Easy and keeps API relatively clean
   Con: Requires user to call fill_lan_msg_hdr and fill_X_cmd before 
   fill_hdr_session.

Al

P.S. There are a number of subtle authtype checks that need to be put
into fill_hdr_sessino() and assemble_lan_packet() to handle this and
pre-msg-authentication.  I will add that whenever i do this ... Also I
think assemble_lan_packet() should return the length of the buffer
written into the packet buffer.  The length will vary depending on the
authentication type.

--
Albert Chu
address@hidden
Lawrence Livermore National Laboratory