Re: [Openvpn-devel] OpenVPN 2.1_rc19 released

2009-07-29 Thread David Balazic 
Hi!


As this discussion has not much to do with the rc19 release, would
you please change the subject ?
Like "OpenVPN and SELinux" or "Securing the OpenVPN process" ...

Thanks,
David


> -Original Message-
> From: Karl O. Pinc [mailto:k...@meme.com] 
> Sent: Wednesday, July 29, 2009 6:17 PM
> To: Alon Bar-Lev
> Cc: openvpn-devel@lists.sourceforge.net
> Subject: Re: [Openvpn-devel] OpenVPN 2.1_rc19 released
> 
> On 07/28/2009 11:47:57 PM, Alon Bar-Lev wrote:
> > Well,
> > I do not understand you guys.
> > 
> > If you think SELinux is so great, why do you need chroot?
> > It is like you put some money in safe, and then put the safe into
> > another safe, it never ends... Why only two safe, let's put another
> > safe...
> > I know that this is the approach many of security advisors 
> use, but I
> > never could have found the logic.
> > If you want to keep your money safe use a single safe and select the
> > strongest one.
> 
> The idea is more like selecting the strongest safe, then putting
> it behind a moat inside a ring of fire.  That way the thief not
> only has to be a good safe cracker, he must also be
> a fire walker and a swimmer, with experience wrestling
> alligators a decided advantage.  Multiple layers of _different_
> security raises the bar considerably.
> 
> 
> 
> Karl <k...@meme.com>
> Free Software:  "You don't pay back, you pay forward."
>  -- Robert A. Heinlein
> 
> 
> --
> 
> Let Crystal Reports handle the reporting - Free Crystal 
> Reports 2008 30-Day 
> trial. Simplify your report design, integration and 
> deployment - and focus on 
> what you do best, core application coding. Discover what's new with 
> Crystal Reports now.  http://p.sf.net/sfu/bobj-july
> ___
> Openvpn-devel mailing list
> Openvpn-devel@lists.sourceforge.net
> https://lists.sourceforge.net/lists/listinfo/openvpn-devel
>

Re: [Openvpn-devel] OpenVPN 2.1_rc19 released

2009-07-29 Thread Karl O. Pinc 
On 07/28/2009 11:47:57 PM, Alon Bar-Lev wrote:
> Well,
> I do not understand you guys.
> 
> If you think SELinux is so great, why do you need chroot?
> It is like you put some money in safe, and then put the safe into
> another safe, it never ends... Why only two safe, let's put another
> safe...
> I know that this is the approach many of security advisors use, but I
> never could have found the logic.
> If you want to keep your money safe use a single safe and select the
> strongest one.

The idea is more like selecting the strongest safe, then putting
it behind a moat inside a ring of fire.  That way the thief not
only has to be a good safe cracker, he must also be
a fire walker and a swimmer, with experience wrestling
alligators a decided advantage.  Multiple layers of _different_
security raises the bar considerably.



Karl 
Free Software:  "You don't pay back, you pay forward."
 -- Robert A. Heinlein

Re: [Openvpn-devel] OpenVPN 2.1_rc19 released

2009-07-29 Thread Michael H. Warfield 
On Wed, 2009-07-29 at 07:47 +0300, Alon Bar-Lev wrote:
> Well,
> I do not understand you guys.

> If you think SELinux is so great, why do you need chroot?
> It is like you put some money in safe, and then put the safe into
> another safe, it never ends... Why only two safe, let's put another
> safe...
> I know that this is the approach many of security advisors use, but I
> never could have found the logic.
> If you want to keep your money safe use a single safe and select the
> strongest one.

Security professionals refer to is as "defense in depth".  Look it up.
The opposite of which is "all your eggs in one basket".  Not good.

With defense in depth, if an attacker finds a hole in one defensive
layer, he should get caught in another.  That way, he has to be perfect
and get through all your defenses without getting caught while you only
have to stop him at one.  The other way (single defense), your defense
must always be perfect and reliable while he only needs a single hole
through that single layer.

Your choice.

> And final note regarding the iproute wrapper.
> It is a *WRAPPER*, if I needed top secured implementation I would have
> created a daemon listening to network change requests using unix
> domain sockets, wrap this up in SELinux profile, and implementing a
> logic that allows only changes to tap/tun interface with specific
> attributes, and allowing routing table update with specific details.
> Then add a wrapper that uses the unix domain socket in order to access
> the daemon. OpenVPN will use the wrapper so it needs no special
> privilege. The daemon validates what SELinux or any other security
> product cannot validate: Network configuration changes. All done
> within a valid and separate context.
> 
> As I wrote earlier, most of OpenVPN configurations need to execute
> iproute also during session. For example, if you like to connect two
> sites, your super SELinux secured solution will work only at one site.
> 
> No need to discuss this further. I get your point.
> 
> Alon.
> 
> --
> Let Crystal Reports handle the reporting - Free Crystal Reports 2008 30-Day 
> trial. Simplify your report design, integration and deployment - and focus on 
> what you do best, core application coding. Discover what's new with 
> Crystal Reports now.  http://p.sf.net/sfu/bobj-july
> ___
> Openvpn-devel mailing list
> Openvpn-devel@lists.sourceforge.net
> https://lists.sourceforge.net/lists/listinfo/openvpn-devel

-- 
Michael H. Warfield (AI4NB) | (770) 985-6132 |  m...@wittsend.com
   /\/\|=mhw=|\/\/  | (678) 463-0932 |  http://www.wittsend.com/mhw/
   NIC whois: MHW9  | An optimist believes we live in the best of all
 PGP Key: 0xDF1DD471| possible worlds.  A pessimist is sure of it!



signature.asc
Description: This is a digitally signed message part

Re: [Openvpn-devel] OpenVPN 2.1_rc19 released

2009-07-29 Thread David Sommerseth 
On 29/07/09 03:49, Karl O. Pinc wrote:
> On 07/28/2009 04:22:09 PM, Sebastien Raveau wrote:
> 
> 
>> If I understand you correctly, that is, if you are suggesting that
>> OpenVPN should automatically apply a SELinux context if setcon() is
>> available... I'll have to disagree with you. Not that I reject the
>> idea of enforcing security measures by default, but because when you
>> google for "selinux howto", half of the first-page results are on how
>> to *disable* SELinux. Apparently not everybody likes it, and they 
>> have
>> a right to, so I believe we should not force it upon them :-)
> 
> SELinux is a great idea, in theory.  In practice I find the
> cost/benefit such that I wind up turning it off.  I'd love
> to have it available and working in "stock" situations,
> and have the (easy to do) option of turning it off if
> desired.   If nothing else it gets in the way of development/
> deployment.  After something's working then it's possible to go back
> and figure out which permissions need enabling.

I've been running Fedora with SELinux enabled for over a year, without
having any issues at all.  I've even been testing a lot of different
software setups on Fedora and Red Hat Enterprise Linux, without having
issues.

> Because of the complication it would also be highly
> desirable, except for a possible "off/monitor mode/on"
> switch, if it would integrate with the rest of SELinux
> so there's not yet more configuration.  I assume that
> this is the natural approach to take, but figured I'd
> mention it anyway.

In Fedora/RHEL you have the getenforce and setenforce programs, which
changes between "Permissive" and "Enforced" modes.  This is a
system-wide configuration change, and is effective immediately without
reboot.  With a properly designed SELinux profile for OpenVPN, usually
from a distribution, but it would be good if it also followed the
OpenVPN source code, it would not be more configuration.  It would be to
register this profile on your system.  Normally, these profiles can be
quite static, no matter which system it is setup on.  On a brand new
installation, it might be needed to label some files on the file system,
but again, this could be done via a little script.  New configuration
files for OpenVPN and certificates would need to be labelled too, but
that's usually just to either copy them into the desired directory and
to run restorecon or chcon.

http://danwalsh.livejournal.com/4208.html

In fact, Fedora and RHEL do ship OpenVPN 2.1_rc15 with SELinux profiles,
labelling files and directories for OpenVPN.  But there is no security
context shift inside the binary, AFAIK, which would be even more
beneficial, as not everything is covered by just file labelling.


kind regards,

David Sommerseth

Re: [Openvpn-devel] OpenVPN 2.1_rc19 released

2009-07-29 Thread Sebastien Raveau 
On Wed, Jul 29, 2009 at 6:47 AM, Alon Bar-Lev wrote:
> Well,
> I do not understand you guys.
>
> If you think SELinux is so great, why do you need chroot?
> It is like you put some money in safe, and then put the safe into
> another safe, it never ends... Why only two safe, let's put another
> safe...
> I know that this is the approach many of security advisors use, but I
> never could have found the logic.
> If you want to keep your money safe use a single safe and select the
> strongest one.

SELinux+chroot is indeed redundant, but as they do not conflict, why
not use them both?
To re-use your safe example: in your bank your belongings could be
protected by a smart safe, security guards and/or policemen... However
redundant that might be, I feel more comfortable knowing that more
means are used to protect my belongings :-)

> The daemon validates what SELinux or any other security
> product cannot validate: Network configuration changes. All done
> within a valid and separate context.

Indeed, indeed :-)

> As I wrote earlier, most of OpenVPN configurations need to execute
> iproute also during session. For example, if you like to connect two
> sites, your super SELinux secured solution will work only at one site.

Maybe so... I did not pretend SELinux was the ultimate solution to
every problem, and I straightforwardly recognize not knowing all
OpenVPN use cases. My will is only to offer more possibilities so that
everybody can find a combination that suits their needs: not everybody
uses the "user" or "chroot" option, probably even less people will use
the "setcon" option and who knows, maybe somebody will submit support
for doing the same with alternatives to SELinux (such as GRSecurity
and RSBAC).

> No need to discuss this further. I get your point.

Ok :-)

-- 
Sebastien Raveau

Re: [Openvpn-devel] OpenVPN 2.1_rc19 released

2009-07-29 Thread David Sommerseth 
On 29/07/09 06:47, Alon Bar-Lev wrote:
> Well,
> I do not understand you guys.
> 
> If you think SELinux is so great, why do you need chroot?
> It is like you put some money in safe, and then put the safe into
> another safe, it never ends... Why only two safe, let's put another
> safe...
> I know that this is the approach many of security advisors use, but I
> never could have found the logic.
> If you want to keep your money safe use a single safe and select the
> strongest one.

I understand partly your logic.  But unfortunately, this is what most
security crackers hope for.  They look for every possibility to get an
opening into a network or server, to gain root access and enable the box
they got access to for further usage.  To defend yourself from a
possibility of a break in, you need to take all possibilities available
in use.  If not, you are weaker than other solutions, and your setup
will be more attractive to those trying to crack into your server.
This is nothing new, this is how the daily life is.

Sooner or later, OpenVPN will be more attractive in general for being
cracked, when other solutions gets more and more secured.  Sooner or
later, OpenVPN will get the storm.  If we are ahead of that storm by
promoting and recommending all possible security features available,
implementing them, the damage after such a storm might not be as big as
it can be without taking advantage of all security measures available.

And another thing you do not take into consideration, is that in your
argument you take it for granted that OpenVPN do not have any security
related bugs, e.g. a buffer overflow which can be misused by carefully
hand crafted network packages, which is unexpected.  It can even be a
flaw inside OpenSSL (which is also not that uncommon).  With SELinux you
limit much more than what chroot() + setuid() can do alone.  But as I
said earlier, non of these calls exclude any other.

> And final note regarding the iproute wrapper.
> It is a *WRAPPER*, if I needed top secured implementation I would have
> created a daemon listening to network change requests using unix
> domain sockets, wrap this up in SELinux profile, and implementing a
> logic that allows only changes to tap/tun interface with specific
> attributes, and allowing routing table update with specific details.
> Then add a wrapper that uses the unix domain socket in order to access
> the daemon. OpenVPN will use the wrapper so it needs no special
> privilege. The daemon validates what SELinux or any other security
> product cannot validate: Network configuration changes. All done
> within a valid and separate context.

This is actually even a much better idea than a wrapper, seriously!
Wrappers, and especially wrappers with sudo access (or even worse, the
setsuid bit set on the file) are prune to be cracked and misused.

As the matter of fact, I've gotten a flaw demonstrated which managed,
through a overflow bug, to write a nicely crafted crontab entry which
then caused the crond to core dump on execution of that entry.  But when
that happened, you had a setsuid binary in /tmp ... which actually was a
copy of a shell.  But it required SELinux to be either to be disabled or
be in Permissive mode (logging only).

> As I wrote earlier, most of OpenVPN configurations need to execute
> iproute also during session. For example, if you like to connect two
> sites, your super SELinux secured solution will work only at one site.

Yes!  And WITH SELinux, it will still be able to run iproute or whatever
else the configuration requires - in a safer and more controlled regime.
 But it will not only work on one site.  It will work wherever SELinux
is properly configured and implemented.  In fact, it will not even break
the OpenVPN functionality if you run a SELinux enabled OpenVPN on a
kernel without SELinux enabled, you will just miss that extra layer of
security.

Security is not about picking the best solution of several options.
Security is about combining the best of all solutions together.


kind regards,

David Sommerseth

Re: [Openvpn-devel] OpenVPN 2.1_rc19 released

2009-07-29 Thread Alon Bar-Lev 
Well,
I do not understand you guys.

If you think SELinux is so great, why do you need chroot?
It is like you put some money in safe, and then put the safe into
another safe, it never ends... Why only two safe, let's put another
safe...
I know that this is the approach many of security advisors use, but I
never could have found the logic.
If you want to keep your money safe use a single safe and select the
strongest one.

And final note regarding the iproute wrapper.
It is a *WRAPPER*, if I needed top secured implementation I would have
created a daemon listening to network change requests using unix
domain sockets, wrap this up in SELinux profile, and implementing a
logic that allows only changes to tap/tun interface with specific
attributes, and allowing routing table update with specific details.
Then add a wrapper that uses the unix domain socket in order to access
the daemon. OpenVPN will use the wrapper so it needs no special
privilege. The daemon validates what SELinux or any other security
product cannot validate: Network configuration changes. All done
within a valid and separate context.

As I wrote earlier, most of OpenVPN configurations need to execute
iproute also during session. For example, if you like to connect two
sites, your super SELinux secured solution will work only at one site.

No need to discuss this further. I get your point.

Alon.

Re: [Openvpn-devel] OpenVPN 2.1_rc19 released

2009-07-29 Thread Karl O. Pinc 
On 07/28/2009 04:22:09 PM, Sebastien Raveau wrote:


> If I understand you correctly, that is, if you are suggesting that
> OpenVPN should automatically apply a SELinux context if setcon() is
> available... I'll have to disagree with you. Not that I reject the
> idea of enforcing security measures by default, but because when you
> google for "selinux howto", half of the first-page results are on how
> to *disable* SELinux. Apparently not everybody likes it, and they 
> have
> a right to, so I believe we should not force it upon them :-)

SELinux is a great idea, in theory.  In practice I find the
cost/benefit such that I wind up turning it off.  I'd love
to have it available and working in "stock" situations,
and have the (easy to do) option of turning it off if
desired.   If nothing else it gets in the way of development/
deployment.  After something's working then it's possible to go back
and figure out which permissions need enabling.

Because of the complication it would also be highly
desirable, except for a possible "off/monitor mode/on"
switch, if it would integrate with the rest of SELinux
so there's not yet more configuration.  I assume that
this is the natural approach to take, but figured I'd
mention it anyway.


Karl 
Free Software:  "You don't pay back, you pay forward."
 -- Robert A. Heinlein

Re: [Openvpn-devel] OpenVPN 2.1_rc19 released

2009-07-28 Thread David Sommerseth 
On 28/07/09 20:29, Sebastien Raveau wrote:
> (Hi again)
> 
> Alon: with all due respect to you and your work - which I am sure is
> the best way to go in some situations - I believe that you are wrong
> on the topic of maximum security...

+1

> First of all, what you're proposing is running OpenVPN as a
> not-exactly-unprivileged user (let's call it "least privileged user"),
> meaning that your user doesn't have 0 right but "only the right to
> modify the routing table". The problem is: in your configuration, this
> least privileged user has this write *permanently*, as opposed to
> starting OpenVPN as root, letting it use privileges during
> initialization and as soon as possible drop to a really-unprivileged
> user thanks to setgid/setgroups/setuid (which is what OpenVPN does
> when you specify the "user" option).

If I understood Alon correctly, he also executes OpenVPN as a less
privileged user, meaning that it is impossible to escape out of that
user, as the saved UID/GID will be a unprivileged user.  But!  Chroot
will in this setting be impossible, because only root can do chroot().

> As a matter of fact, I'm afraid I would even strongly recommend
> _against_ your suggestion, because if some company were to use OpenVPN
> on an Internet gateway with your configuration, a hacker would be able
> to alter the routing table for the whole company, and hence
> transparently redirect employees to phishing websites, just because
> your "unprivileged OpenVPN" is allowed to run /sbin/ip with any
> parameters at any time (which is a HUGE privilege).

+1 ... It is of course possible to tighten this even more, but it will
require even more complex efforts to do this right, and it will still
not cover all those gaps which SELinux can fill.  The user account which
openvpn will run as, will still need to run the wrapped ip/iproute
commands.  Thus you still will have an attack vector.

If in addition you have cleverly composed arguments to this wrapper, you
might even manage to escape the ip/iproute command and start another
program as root, say /bin/sh f.ex. ... or even change the root password
to a known password by editing /etc/shadow with a little /usr/bin/sed
command.  And if openvpn is not started as root, you cannot chroot this
process (at least not without having another startup wrapper around
openvpn).  And this attack vector, only SELinux can cover best, as the
security context would be different from what the openvpn process runs
with and the permissions needed to run /bin/sh, /usr/bin/sed, or another
non-openvpn approved binary.

> Now, to transpose that back to SELinux, if the setcon code could be
> added inside OpenVPN (next to the setuid and chroot code which have
> already been accepted as clearly benefiting) it would be possible to
> reduce the SELinux policy for OpenVPN from ~100 lines (
> http://oss.tresys.com/projects/clip/browser/trunk/refpolicy/src/selinux-policy-clip/policy/modules/services/openvpn.te?rev=13
> ) to ~10 !!  (basically just the lines allowing network I/O)

I still would say that these ~100 lines you link to her, Sebastien,
would still be needed.  Still not sure how plug-ins would like it with
this config.  But having a setcon() call inside OpenVPN, is just as
beneficial as having setuid(), setgid() and chroot() inside openvpn.
And none of these calls makes the other calls less needed.

Having that said, most of the policy Sebastian linked to here, covers
many of my concerns earlier.  Even though how code in plug-ins would be
executed (in which context) is more uncertain for me right now.

> I totally agree with you however on the "Keep It Simple, Stupid
> (KISS)" principle applied to security. I hope that this /10 cut in the
> oh-so-complex writing of a SELinux policy proves to you the benefit of
> my patch :-)

Even though SELinux itself is complex, it doesn't mean that using it is
too difficult.  Using it properly is more challenging though, compared
to not using it.  But we don't stop using firewalls because we find it
difficult, do we?  And nowadays, not many people find firewalling as
difficult as 10 years ago.

And Alon, to your 3 bullet points ...

> As far as I learned, when security is concerned:
> 1. Make your solution as simple as possible.
> 2. Make the simple solution secure enough.
> 3. Enhance the security using security products.

I completely agree to you on these points.  The thing is that I (and
probably also Sebastien) already consider the two first points to be
covered pretty well, they are done.  Now we just want number 3 closed as
well, as this is not implemented at all.

Sebastien, back to your patch.  There is one thing I've been thinking
about today, regarding the --setcon parameter you introduce to the
openvpn binary.  Why does this need to be a runtime parameter?  I cannot
imagine you want to run openvpn with different security context on the
same box, or even the same Linux distro.  In my eyes, this would be a
static value.  The SELinux context

Re: [Openvpn-devel] OpenVPN 2.1_rc19 released

2009-07-28 Thread Sebastien Raveau 
(Hi again)

David: you did not "interrupt badly", on the contrary I am glad that
the discussion continued while I was away :-)

Alon: with all due respect to you and your work - which I am sure is
the best way to go in some situations - I believe that you are wrong
on the topic of maximum security...

First of all, what you're proposing is running OpenVPN as a
not-exactly-unprivileged user (let's call it "least privileged user"),
meaning that your user doesn't have 0 right but "only the right to
modify the routing table". The problem is: in your configuration, this
least privileged user has this write *permanently*, as opposed to
starting OpenVPN as root, letting it use privileges during
initialization and as soon as possible drop to a really-unprivileged
user thanks to setgid/setgroups/setuid (which is what OpenVPN does
when you specify the "user" option).

I hope you understand that, paradoxically perhaps, the latter is
really more secure than the former.

As a matter of fact, I'm afraid I would even strongly recommend
_against_ your suggestion, because if some company were to use OpenVPN
on an Internet gateway with your configuration, a hacker would be able
to alter the routing table for the whole company, and hence
transparently redirect employees to phishing websites, just because
your "unprivileged OpenVPN" is allowed to run /sbin/ip with any
parameters at any time (which is a HUGE privilege).

Also, speaking of complexity and ease of use, let's pretend we're
debating over pre-initialization chroot vs post-initialization,
instead of setcon (the SELinux context switch). It is really the same
with setuid, but the difference is easier to understand in the case of
chroot.

Pre-initialization chroot (from the outside of OpenVPN if you will)
would require reproducing the filesystem environment OpenVPN will
need, which means copying /usr/sbin/openvpn
/usr/lib/libpkcs11-helper.so.1 /lib/tls/i686/cmov/libpthread.so.0
/lib/tls/i686/cmov/libc.so.6 /lib/ld-linux.so.2
/lib/tls/i686/cmov/libdl.so.2 /lib/i686/cmov/libcrypto.so.0.9.8
/lib/libz.so.1 /lib/i686/cmov/libssl.so.0.9.8 /usr/lib/liblzo2.so.2
just to get the executable to launch. Then you will most likely need
access to at least one of the /dev, /proc and /sys pseudo-filesystems
which means you will have to `mount --bind` them in the target
directory for your chroot, etc...

Post-initialization chroot, for which the code has been added inside
OpenVPN (see init.c:392 and misc.c:48) requires none of that and
actually does better, as you can have your OpenVPN chroot'ed in a
completely empty directory.

Now, to transpose that back to SELinux, if the setcon code could be
added inside OpenVPN (next to the setuid and chroot code which have
already been accepted as clearly benefiting) it would be possible to
reduce the SELinux policy for OpenVPN from ~100 lines (
http://oss.tresys.com/projects/clip/browser/trunk/refpolicy/src/selinux-policy-clip/policy/modules/services/openvpn.te?rev=13
) to ~10 !!  (basically just the lines allowing network I/O)


I totally agree with you however on the "Keep It Simple, Stupid
(KISS)" principle applied to security. I hope that this /10 cut in the
oh-so-complex writing of a SELinux policy proves to you the benefit of
my patch :-)


On Tue, Jul 28, 2009 at 4:20 PM, Alon Bar-Lev wrote:
> I don't understand you guys.
>
> I never said do not use SELinux, or that SELinux does not have advantages.
> I know perfectly what the advantages are.
>
> BUT it is much easier to create profile to unprivileged user that runs
> OpenVPN than a profile of a daemon that needs special rights.
>
> As far as I learned, when security is concerned:
> 1. Make your solution as simple as possible.
> 2. Make the simple solution secure enough.
> 3. Enhance the security using security products.
>
> When you try to do (3) before (1) you get unmanageable solution, which
> in time also results in unsecured solution.
>
> Just my two cents.
>
> Alon.
>
> On Tue, Jul 28, 2009 at 5:05 PM, David
> Sommerseth wrote:
>>
>>
>> Alon Bar-Lev wrote:
>>>
>>> I do not understand, but it looks that two of you are searching for a
>>> solution inside the box, while the solution is out side the box.
>>>
>>> I added the ability for OpenVPN to run using unprivileged user, yes,
>>> please read it as-is, unprivileged user!!!
>>> This means that you don't need any special permission to run OpenVPN.
>>>
>>> How did I manage to do this?
>>>
>>> Simply,
>>> 1. Linux's tun device access may be enabled to a specific user or group.
>>> 2. Wrap iproute2 calls.
>>
>> This is not what SELinux primarily solves, even though it also solves this
>> too.  But it can restrict access to resources OpenVPN initially should only
>> have.
>>
>> OpenVPN depends on devices in kernel space, even if you restrict that on the
>> "normal" file system level (chmod 600 /dev/net/tun*), a bug/exploit in the
>> device being used can still be used for privilege

Re: [Openvpn-devel] OpenVPN 2.1_rc19 released

2009-07-28 Thread Alon Bar-Lev 
I don't understand you guys.

I never said do not use SELinux, or that SELinux does not have advantages.
I know perfectly what the advantages are.

BUT it is much easier to create profile to unprivileged user that runs
OpenVPN than a profile of a daemon that needs special rights.

As far as I learned, when security is concerned:
1. Make your solution as simple as possible.
2. Make the simple solution secure enough.
3. Enhance the security using security products.

When you try to do (3) before (1) you get unmanageable solution, which
in time also results in unsecured solution.

Just my two cents.

Alon.

On Tue, Jul 28, 2009 at 5:05 PM, David
Sommerseth wrote:
>
>
> Alon Bar-Lev wrote:
>>
>> I do not understand, but it looks that two of you are searching for a
>> solution inside the box, while the solution is out side the box.
>>
>> I added the ability for OpenVPN to run using unprivileged user, yes,
>> please read it as-is, unprivileged user!!!
>> This means that you don't need any special permission to run OpenVPN.
>>
>> How did I manage to do this?
>>
>> Simply,
>> 1. Linux's tun device access may be enabled to a specific user or group.
>> 2. Wrap iproute2 calls.
>
> This is not what SELinux primarily solves, even though it also solves this
> too.  But it can restrict access to resources OpenVPN initially should only
> have.
>
> OpenVPN depends on devices in kernel space, even if you restrict that on the
> "normal" file system level (chmod 600 /dev/net/tun*), a bug/exploit in the
> device being used can still be used for privilege escalation.  This is one
> of the attack vectors SELinux tries to solve.  It makes sure the application
> do not get access to devices, files, processes, etc which is not defined in
> the security context - because this is possible attack vectors.
>
>> I am not against SELinux usage in OpenVPN. I just want you to be aware
>> that there is alternatives that can use OpenVPN without any special
>> right.
>
> Agreed, there are plenty of alternatives, but they only focus on the
> user-space area primarily, not kernel space.  In the wrapper you suggest,
> there is nothing here protecting against malformed information being sent to
> the wrapper around iproute2, combine that with some buffer overflows bugs in
> iproute2, and you have yet another attack vector.  Take a look after the
> latest cheddar_bay exploit being found recently.  Here several small flaws
> are used together to gain root shell access on a vulnerable system.
>
> SELinux will make it more difficult, as it is even more tricky to disable
> the SELinux controll mechanism on the way.
>
>
> Kind regards,
>
> David Sommerseth
>
>
>> On Tue, Jul 28, 2009 at 4:28 PM, David
>> Sommerseth wrote:
>>>
>>> Alon Bar-Lev wrote:

 I do not understand either.

 If you run OpenVPN from unprivileged user from startup, this apposed
 of letting OpenVPN to setuid(), what do you need to protect in middle
 of operation?

 On Tue, Jul 28, 2009 at 11:33 AM, Sebastien
 Raveau wrote:
>
> I'm not sure I understand you...
>
> As I explained in
> http://article.gmane.org/gmane.network.openvpn.devel/2700 it is indeed
> possible to apply SELinux "from the outside" of a program, like
> chroot, and just like chroot doing that is less efficient and less
> practical.
>
>>> I hope I'm not interrupting badly now.
>>>
>>> A little basic part, for those wanting to understand the depths. What
>>> SELinux provides is access control on different kind of layers inside the
>>> kernel space, also on system calls.  For a brief overview over SELinux,
>>> have
>>> a look here:
>>> http://www.ibm.com/developerworks/linux/library/l-sppriv.html,
>>>
>>> http://www.ibm.com/developerworks/linux/library/l-selinux/index.html?S_TACT=105AGX03_CMP=EDU
>>> (A lot of more good SELinux information is available on IBM's
>>> developerWorks
>>> site)
>>>
>>> It makes sense to do a security context switch after OpenVPN has
>>> initialised
>>> and chrooted, then changing security context and drop the rest of the
>>> privileges.  In the new OpenVPN security context, it should then not be
>>> allowed to do any chrooting or network configuration (as this is a part
>>> of
>>> the initialisation, IMO), and even if possible, setuid() should be
>>> disallowed.  That way you can really lock down everything OpenVPN should
>>> not
>>> do - just allowing what it needs to do.  Basically, the OpenVPN security
>>> context should only be allowed to write to log files, execute code in
>>> plug-ins, read a limited range of files, and read/write to a network
>>> device
>>> granting access to the openvpn context.
>>>
>>> What I am lacking in this patch, is a security context definition (at
>>> least
>>> an example of how to configure a proper context for OpenVPN).  Further;
>>> has
>>> it been investigated if there need to be done some other

Re: [Openvpn-devel] OpenVPN 2.1_rc19 released

2009-07-28 Thread David Sommerseth 



Alon Bar-Lev wrote:

I do not understand, but it looks that two of you are searching for a
solution inside the box, while the solution is out side the box.

I added the ability for OpenVPN to run using unprivileged user, yes,
please read it as-is, unprivileged user!!!
This means that you don't need any special permission to run OpenVPN.

How did I manage to do this?

Simply,
1. Linux's tun device access may be enabled to a specific user or group.
2. Wrap iproute2 calls.


This is not what SELinux primarily solves, even though it also solves this 
too.  But it can restrict access to resources OpenVPN initially should only 
have.


OpenVPN depends on devices in kernel space, even if you restrict that on 
the "normal" file system level (chmod 600 /dev/net/tun*), a bug/exploit in 
the device being used can still be used for privilege escalation.  This is 
one of the attack vectors SELinux tries to solve.  It makes sure the 
application do not get access to devices, files, processes, etc which is 
not defined in the security context - because this is possible attack vectors.



I am not against SELinux usage in OpenVPN. I just want you to be aware
that there is alternatives that can use OpenVPN without any special
right.


Agreed, there are plenty of alternatives, but they only focus on the 
user-space area primarily, not kernel space.  In the wrapper you suggest, 
there is nothing here protecting against malformed information being sent 
to the wrapper around iproute2, combine that with some buffer overflows 
bugs in iproute2, and you have yet another attack vector.  Take a look 
after the latest cheddar_bay exploit being found recently.  Here several 
small flaws are used together to gain root shell access on a vulnerable system.


SELinux will make it more difficult, as it is even more tricky to disable 
the SELinux controll mechanism on the way.



Kind regards,

David Sommerseth



On Tue, Jul 28, 2009 at 4:28 PM, David
Sommerseth wrote:

Alon Bar-Lev wrote:

I do not understand either.

If you run OpenVPN from unprivileged user from startup, this apposed
of letting OpenVPN to setuid(), what do you need to protect in middle
of operation?

On Tue, Jul 28, 2009 at 11:33 AM, Sebastien
Raveau wrote:

I'm not sure I understand you...

As I explained in
http://article.gmane.org/gmane.network.openvpn.devel/2700 it is indeed
possible to apply SELinux "from the outside" of a program, like
chroot, and just like chroot doing that is less efficient and less
practical.


I hope I'm not interrupting badly now.

A little basic part, for those wanting to understand the depths. What
SELinux provides is access control on different kind of layers inside the
kernel space, also on system calls.  For a brief overview over SELinux, have
a look here: http://www.ibm.com/developerworks/linux/library/l-sppriv.html,
http://www.ibm.com/developerworks/linux/library/l-selinux/index.html?S_TACT=105AGX03_CMP=EDU
(A lot of more good SELinux information is available on IBM's developerWorks
site)

It makes sense to do a security context switch after OpenVPN has initialised
and chrooted, then changing security context and drop the rest of the
privileges.  In the new OpenVPN security context, it should then not be
allowed to do any chrooting or network configuration (as this is a part of
the initialisation, IMO), and even if possible, setuid() should be
disallowed.  That way you can really lock down everything OpenVPN should not
do - just allowing what it needs to do.  Basically, the OpenVPN security
context should only be allowed to write to log files, execute code in
plug-ins, read a limited range of files, and read/write to a network device
granting access to the openvpn context.

What I am lacking in this patch, is a security context definition (at least
an example of how to configure a proper context for OpenVPN).  Further; has
it been investigated if there need to be done some other context changes to
the TUN/TAP devices?  What about other files?  If a log file is labelled
var_log_t, will the new openvpn security context be allowed to write to this
log file?  How would this work with the security context of the directory of
the log file? (It might be that the easy approach would to do logging via
syslog())   Then what about plug-ins, how would OpenVPN work in these
settings when the SELinux context is changed?  F.ex. how would this patch
work against the down-root.so plugin?

I do agree, implementing SELinux in the openvpn code is an important step!
 But it seems to be just too easy to do setcon().  It is just missing a
consequence analysis of what else needs to be changed in addition to this
patch.

I'm not an SELinux expert, and Sebastien might know far more about SElinux
 than anyone of us.  I don't want to trample on anyone feet ... but I just
wanted to have clarified these issues before I can give 100% support to this
patch, as it just seemed to be too easy.


--
kind

Re: [Openvpn-devel] OpenVPN 2.1_rc19 released

2009-07-28 Thread Alon Bar-Lev 
I do not understand, but it looks that two of you are searching for a
solution inside the box, while the solution is out side the box.

I added the ability for OpenVPN to run using unprivileged user, yes,
please read it as-is, unprivileged user!!!
This means that you don't need any special permission to run OpenVPN.

How did I manage to do this?

Simply,
1. Linux's tun device access may be enabled to a specific user or group.
2. Wrap iproute2 calls.

So I run OpenVPN completely in unprivileged mode, it can access the
tun device, then when it wish to alter network configuration it can do
so by the wrapper (I used sudo for this).

Most OpenVPN configuration requires more than one time network settings.

In stead of sudo wrapper you can use SELinux enabled wrapper.

The advantage of sudo wrapper is that it is simple, and the script can
check if the new network configuration is valid for OpenVPN usage.

I am not against SELinux usage in OpenVPN. I just want you to be aware
that there is alternatives that can use OpenVPN without any special
right.

Alon.


On Tue, Jul 28, 2009 at 4:28 PM, David
Sommerseth wrote:
> Alon Bar-Lev wrote:
>>
>> I do not understand either.
>>
>> If you run OpenVPN from unprivileged user from startup, this apposed
>> of letting OpenVPN to setuid(), what do you need to protect in middle
>> of operation?
>>
>> On Tue, Jul 28, 2009 at 11:33 AM, Sebastien
>> Raveau wrote:
>>>
>>> I'm not sure I understand you...
>>>
>>> As I explained in
>>> http://article.gmane.org/gmane.network.openvpn.devel/2700 it is indeed
>>> possible to apply SELinux "from the outside" of a program, like
>>> chroot, and just like chroot doing that is less efficient and less
>>> practical.
>>>
>
> I hope I'm not interrupting badly now.
>
> A little basic part, for those wanting to understand the depths. What
> SELinux provides is access control on different kind of layers inside the
> kernel space, also on system calls.  For a brief overview over SELinux, have
> a look here: http://www.ibm.com/developerworks/linux/library/l-sppriv.html,
> http://www.ibm.com/developerworks/linux/library/l-selinux/index.html?S_TACT=105AGX03_CMP=EDU
> (A lot of more good SELinux information is available on IBM's developerWorks
> site)
>
> It makes sense to do a security context switch after OpenVPN has initialised
> and chrooted, then changing security context and drop the rest of the
> privileges.  In the new OpenVPN security context, it should then not be
> allowed to do any chrooting or network configuration (as this is a part of
> the initialisation, IMO), and even if possible, setuid() should be
> disallowed.  That way you can really lock down everything OpenVPN should not
> do - just allowing what it needs to do.  Basically, the OpenVPN security
> context should only be allowed to write to log files, execute code in
> plug-ins, read a limited range of files, and read/write to a network device
> granting access to the openvpn context.
>
> What I am lacking in this patch, is a security context definition (at least
> an example of how to configure a proper context for OpenVPN).  Further; has
> it been investigated if there need to be done some other context changes to
> the TUN/TAP devices?  What about other files?  If a log file is labelled
> var_log_t, will the new openvpn security context be allowed to write to this
> log file?  How would this work with the security context of the directory of
> the log file? (It might be that the easy approach would to do logging via
> syslog())   Then what about plug-ins, how would OpenVPN work in these
> settings when the SELinux context is changed?  F.ex. how would this patch
> work against the down-root.so plugin?
>
> I do agree, implementing SELinux in the openvpn code is an important step!
>  But it seems to be just too easy to do setcon().  It is just missing a
> consequence analysis of what else needs to be changed in addition to this
> patch.
>
> I'm not an SELinux expert, and Sebastien might know far more about SElinux
>  than anyone of us.  I don't want to trample on anyone feet ... but I just
> wanted to have clarified these issues before I can give 100% support to this
> patch, as it just seemed to be too easy.
>
>
> --
> kind regards,
>
> David Sommerseth
>
>
>

Re: [Openvpn-devel] OpenVPN 2.1_rc19 released

2009-07-28 Thread David Sommerseth 

Alon Bar-Lev wrote:

I do not understand either.

If you run OpenVPN from unprivileged user from startup, this apposed
of letting OpenVPN to setuid(), what do you need to protect in middle
of operation?

On Tue, Jul 28, 2009 at 11:33 AM, Sebastien
Raveau wrote:

I'm not sure I understand you...

As I explained in
http://article.gmane.org/gmane.network.openvpn.devel/2700 it is indeed
possible to apply SELinux "from the outside" of a program, like
chroot, and just like chroot doing that is less efficient and less
practical.



I hope I'm not interrupting badly now.

A little basic part, for those wanting to understand the depths. What 
SELinux provides is access control on different kind of layers inside the 
kernel space, also on system calls.  For a brief overview over SELinux, 
have a look here: 
http://www.ibm.com/developerworks/linux/library/l-sppriv.html, 
http://www.ibm.com/developerworks/linux/library/l-selinux/index.html?S_TACT=105AGX03_CMP=EDU 
(A lot of more good SELinux information is available on IBM's 
developerWorks site)


It makes sense to do a security context switch after OpenVPN has 
initialised and chrooted, then changing security context and drop the rest 
of the privileges.  In the new OpenVPN security context, it should then not 
be allowed to do any chrooting or network configuration (as this is a part 
of the initialisation, IMO), and even if possible, setuid() should be 
disallowed.  That way you can really lock down everything OpenVPN should 
not do - just allowing what it needs to do.  Basically, the OpenVPN 
security context should only be allowed to write to log files, execute code 
in plug-ins, read a limited range of files, and read/write to a network 
device granting access to the openvpn context.


What I am lacking in this patch, is a security context definition (at least 
an example of how to configure a proper context for OpenVPN).  Further; has 
it been investigated if there need to be done some other context changes to 
the TUN/TAP devices?  What about other files?  If a log file is labelled 
var_log_t, will the new openvpn security context be allowed to write to 
this log file?  How would this work with the security context of the 
directory of the log file? (It might be that the easy approach would to do 
logging via syslog())   Then what about plug-ins, how would OpenVPN work in 
these settings when the SELinux context is changed?  F.ex. how would this 
patch work against the down-root.so plugin?


I do agree, implementing SELinux in the openvpn code is an important step! 
 But it seems to be just too easy to do setcon().  It is just missing a 
consequence analysis of what else needs to be changed in addition to this 
patch.


I'm not an SELinux expert, and Sebastien might know far more about SElinux 
 than anyone of us.  I don't want to trample on anyone feet ... but I just 
wanted to have clarified these issues before I can give 100% support to 
this patch, as it just seemed to be too easy.



--
kind regards,

David Sommerseth

Re: [Openvpn-devel] OpenVPN 2.1_rc19 released

2009-07-28 Thread Alon Bar-Lev 
I do not understand either.

If you run OpenVPN from unprivileged user from startup, this apposed
of letting OpenVPN to setuid(), what do you need to protect in middle
of operation?

On Tue, Jul 28, 2009 at 11:33 AM, Sebastien
Raveau wrote:
> I'm not sure I understand you...
>
> As I explained in
> http://article.gmane.org/gmane.network.openvpn.devel/2700 it is indeed
> possible to apply SELinux "from the outside" of a program, like
> chroot, and just like chroot doing that is less efficient and less
> practical.
>
> On Tue, Jul 28, 2009 at 10:18 AM, Alon Bar-Lev wrote:
>> Do that.
>> But as in this case OpenVPN does not run under privilege account at
>> any time, you can do this simply without any selinux code into VPN.
>>
>> On Tue, Jul 28, 2009 at 11:12 AM, Sebastien
>> Raveau wrote:
>>> On Tue, Jul 28, 2009 at 9:59 AM, Alon Bar-Lev wrote:
 Why don't you use openvpn in completely unprivileged mode?
 Look at [1] search for Unprivileged mode.
 [1] 
 http://openvpn.net/index.php/open-source/documentation/howto.html#security
>>>
>>> What makes you think I don't already? :-)
>>>
>>> I do, and it is *not* sufficient as this does not protect against
>>> kernel exploits. If a hacker manages to perform remote code execution
>>> in OpenVPN and thus exploit a vulnerable system call, (s)he obtains
>>> kernel privileges and all of a sudden all your setuid, chroot etc are
>>> useless...
>>>
>>> This can be countered with SELinux (and equivalents such as
>>> GRSecurity, RSBAC, LIDS etc) basically by applying access control on
>>> system calls.
>>>
>>>
>>> Kind regards,
>>>
>>> --
>>> Sebastien Raveau
>>>
>>
>
>
>
> --
> Sebastien Raveau
>

Re: [Openvpn-devel] OpenVPN 2.1_rc19 released

2009-07-28 Thread Sebastien Raveau 
I'm not sure I understand you...

As I explained in
http://article.gmane.org/gmane.network.openvpn.devel/2700 it is indeed
possible to apply SELinux "from the outside" of a program, like
chroot, and just like chroot doing that is less efficient and less
practical.

On Tue, Jul 28, 2009 at 10:18 AM, Alon Bar-Lev wrote:
> Do that.
> But as in this case OpenVPN does not run under privilege account at
> any time, you can do this simply without any selinux code into VPN.
>
> On Tue, Jul 28, 2009 at 11:12 AM, Sebastien
> Raveau wrote:
>> On Tue, Jul 28, 2009 at 9:59 AM, Alon Bar-Lev wrote:
>>> Why don't you use openvpn in completely unprivileged mode?
>>> Look at [1] search for Unprivileged mode.
>>> [1] 
>>> http://openvpn.net/index.php/open-source/documentation/howto.html#security
>>
>> What makes you think I don't already? :-)
>>
>> I do, and it is *not* sufficient as this does not protect against
>> kernel exploits. If a hacker manages to perform remote code execution
>> in OpenVPN and thus exploit a vulnerable system call, (s)he obtains
>> kernel privileges and all of a sudden all your setuid, chroot etc are
>> useless...
>>
>> This can be countered with SELinux (and equivalents such as
>> GRSecurity, RSBAC, LIDS etc) basically by applying access control on
>> system calls.
>>
>>
>> Kind regards,
>>
>> --
>> Sebastien Raveau
>>
>



-- 
Sebastien Raveau

Re: [Openvpn-devel] OpenVPN 2.1_rc19 released

2009-07-28 Thread Alon Bar-Lev 
Do that.
But as in this case OpenVPN does not run under privilege account at
any time, you can do this simply without any selinux code into VPN.

On Tue, Jul 28, 2009 at 11:12 AM, Sebastien
Raveau wrote:
> On Tue, Jul 28, 2009 at 9:59 AM, Alon Bar-Lev wrote:
>> Why don't you use openvpn in completely unprivileged mode?
>> Look at [1] search for Unprivileged mode.
>> [1] 
>> http://openvpn.net/index.php/open-source/documentation/howto.html#security
>
> What makes you think I don't already? :-)
>
> I do, and it is *not* sufficient as this does not protect against
> kernel exploits. If a hacker manages to perform remote code execution
> in OpenVPN and thus exploit a vulnerable system call, (s)he obtains
> kernel privileges and all of a sudden all your setuid, chroot etc are
> useless...
>
> This can be countered with SELinux (and equivalents such as
> GRSecurity, RSBAC, LIDS etc) basically by applying access control on
> system calls.
>
>
> Kind regards,
>
> --
> Sebastien Raveau
>

Re: [Openvpn-devel] OpenVPN 2.1_rc19 released

2009-07-28 Thread Alon Bar-Lev 
Hello,

Why don't you use openvpn in completely unprivileged mode?

Look at [1] search for Unprivileged mode.

OpenVPN can access tun device as regular user, execute iproute2 using
sudo wrapper or any other wrapper you supply.

Alon

[1] http://openvpn.net/index.php/open-source/documentation/howto.html#security

On Tue, Jul 28, 2009 at 10:49 AM, Sebastien Raveau
 wrote:
>
> Hi!
>
> Pardon me for asking but... I see you guys talking about a new release
> candidate, and I am still without news about my contribution to
> OpenVPN that I submitted one month ago:
> http://article.gmane.org/gmane.network.openvpn.devel/2700
>
> Is there something wrong about it?
>
> --
> Sebastien Raveau
>
> --
> Let Crystal Reports handle the reporting - Free Crystal Reports 2008 30-Day
> trial. Simplify your report design, integration and deployment - and focus on
> what you do best, core application coding. Discover what's new with
> Crystal Reports now.  http://p.sf.net/sfu/bobj-july
> ___
> Openvpn-devel mailing list
> Openvpn-devel@lists.sourceforge.net
> https://lists.sourceforge.net/lists/listinfo/openvpn-devel

Re: [Openvpn-devel] OpenVPN 2.1_rc19 released

2009-07-17 Thread Karl O. Pinc 


On 07/16/2009 04:24:44 PM, James Yonan wrote:

Matthias Andree wrote:
> James Yonan schrieb:
>
>> 2009.07.16 -- Version 2.1_rc19
> ...
>
>> * In configure.ac, use datadir instead of datarootdir for
compatibility
>>with 
> Dear Jim,
>
> This is backwards.  Please don't do that,




We need to be able to build OpenVPN on older Linux distros, such as
RHEL
4, that use pre-2.60 versions of autoconf.


I don't know about earlier, but autoconf 2.59 comes with

# m4_version_prereq(VERSION, [IF-OK], [IF-NOT = FAIL])
# 
# Check this Autoconf version against VERSION.

AFICT this can be used to do things one way with older
versions and another with newer.

m4_version_preqreq(`2.60', datarootdir, datadir)

I can't say whether this is actually a better way
to do things.

Karl 
Free Software:  "You don't pay back, you pay forward."
 -- Robert A. Heinlein

Re: [Openvpn-devel] OpenVPN 2.1_rc19 released

2009-07-16 Thread James Yonan 

Matthias Andree wrote:

James Yonan schrieb:


2009.07.16 -- Version 2.1_rc19

...


* In configure.ac, use datadir instead of datarootdir for compatibility
   with 

Dear Jim,

This is backwards.  Please don't do that, but revert that change and
instead update the argument of AC_PREREQ in configure.ac to read this:
AC_PREREQ(2.60)

Since you're using autoconf/automake, configure.ac changes and
requirements have zero impact on end users who download the tarball that
you generate through "make dist". Such changes only affects developers
who want to hack configure.ac or use the SVN version, and you can simply
expect them to have an autoconf version no older than 36 months.

In my experience, newer autoconf versions are more portable, have less
bugs, and are good for a much smoother ride than older versions.

I'm happy to look into updating configure.ac, which in general needs an
overhaul anyways - unless you say "no configure.ac updates before 2.1
release".


We need to be able to build OpenVPN on older Linux distros, such as RHEL 
4, that use pre-2.60 versions of autoconf.


Before I made this change, I found that the previous code (using 
datarootdir instead of datadir on RHEL 4, autoconf-2.59-5) would 
generate a make install script that violated the --prefix argument -- 
i.e. make install would try to write stuff outside the --prefix dir.  I 
was running the make install as a non-root user, so the jailbreak out of 
--prefix was obvious because it tried to write to parts of the 
filesystem that generated "permission denied" errors and halted the script.


I'm not an autoconf/automake expert, so if there's a better way to fix 
the issue, I'm open to it.


James

Re: [Openvpn-devel] OpenVPN 2.1_rc19 released

2009-07-16 Thread Matthias Andree 
James Yonan schrieb:

> 2009.07.16 -- Version 2.1_rc19
...

> * In configure.ac, use datadir instead of datarootdir for compatibility
>with

[Openvpn-devel] OpenVPN 2.1_rc19 released

2009-07-16 Thread James Yonan 
This release fixes an issue with the Windows TAP driver that can cause 
BSODs on Vista (normally seen in the OpenVPN client).  The problem is 
that Windows has always restricted kernel threads to a very small stack 
size (12KB on x86 32-bit).  If they go over this limit, Windows will 
crash with a BSOD.  Apparently Vista has added a bit more bloat to its 
kernel stack usage, and as a result, when the TAP driver is called, and 
then it in turn calls other kernel-level functions, there is a chance 
that the kernel stack can overflow in a particular sequence of code that 
is executed when the client initially connects and gets an IP address 
assignment from the server.  Apparently because XP is more efficient in 
its use of stack space, the same build of the TAP driver running on XP 
does not exhibit this defect.


2009.07.16 -- Version 2.1_rc19

* In Windows TAP driver, refactor DHCP/ARP packet injection code to
  use a DPC (deferred procedure call) to defer packet injection until
  IRQL < DISPATCH_LEVEL, rather than calling NdisMEthIndicateReceive
  in the context of AdapterTransmit.  This is an attempt to reduce kernel
  stack usage, and prevent EXCEPTION_DOUBLE_FAULT BSODs that have been
  observed on Vista.  Updated TAP driver version number to 9.6.

* In configure.ac, use datadir instead of datarootdir for compatibility
  with