[pptp-server] RE: [SLUG] PPPD and C source -Tracking that External IP....

[George Vieira]

I've done a little more research and found that there is no link between
PPTP and PPPD which is traceable.. The only thing I can now think of is to
make PPTP to pass the ipparam parameter to PPPD then it can be tracked
back..eg.

1) VPN client connects from address 141.x.x.x
2) PPTPD accepts the connection
3) PPTPD creates a /var/run/pptpd-link0 and stores the external IP into it 
     (more client connections become -link1, -link2, etc)
4) PPTPD forks PPPD using: pppd blah blah blah ipparam ${ipparam}-link0
     (Note: Incase the user already uses ipparam it is passed and "-link0"
is added to it.ie. mypptp-link0)
5) PPPD starts up and uses the ipparam passed by PPTP and possibly anything
else the user sent ( ${ipparam} ).

PPPD ip-up.local can then determine from the ipparam parameter what the IP
address is from the file containing the true IP address of the client
(/var/run/pptp-link0) ...

#  ip-up.local  (example)

#!/bin/sh
LINK=`echo "$6" | cut -f 2 -d "-"`
REALIP=`cat /var/run/pptpd-$LINK`

This sounds like it'll work without modifying the PPPD source code but has
created alot more tweaking on the PPTPD source side... Worst thing is I have
not coded C in 10 years and it's changed alot to me..

Now for the hard part......

thanks,
George Vieira
Systems Manager
Citadel Computer Systems P/L
http://www.citadelcomputer.com.au