Hi,
On Mon, Nov 24, 2008 at 12:56, Les Mikesell <lesmikesell@gmail.com> wrote:
> Microsoft has updated PPTP since the only paper I know about was written.
> Does anyone know if there are still problems with it or if the linux
> version is updated to match?
From http://pptpclient.sourceforge.net/protocol-security.phtml:
"PPTP on Linux, and Microsoft's PPTP, both implement fixes for vulnerabilities that were detected years ago in Microsoft's PPTP. But there remain the design vulnerabilities that cannot be fixed without changing the design. The changes needed would break interoperability. We can't change the Linux PPTP design, because it would stop working with Microsoft PPTP. They can't change their design, because it would stop working with all the other components out there, such as Nortel and Cisco, embedded routers, ADSL modems and their own Windows installed base."
And POPTOP (http://poptop.sourceforge.net/dox/qna.html#12):
In conclusion: Poptop suffers the same security vulnerabilities as the NT sever (this is because it operates with Windows clients).
Update: MSCHAPv2 has been released and addresses some of the security issues. Poptop works with MSCHAPv2, which is implemented in pppd.
Wikipedia (http://en.wikipedia.org/wiki/PPTP):
PPTP has been made obsolete by Layer 2 Tunneling Protocol (L2TP) and IPSec.
From these sources, I can't tell for sure if the protocol has vulnerabilities by design or not, but in any case it seems to be agreement that other VPN protocols such as IPSec are much more secure and reliable than PPTP. I would not recommend starting a VPN implementation using PPTP.
L2TP/IPSec seems to be the best alternative regarding client support (built-in support on Windows XP, Mac and the iPhone), only it is very hard to implement on a Linux server, and there are issues with NAT traversal. OpenVPN is easy to implement and seems to work very well with NAT, but clients must be downloaded and installed for most platforms, and are not available, for instance, for the iPhone.
HTH,
Filipe