Re: Problem with IPSEC


I am just using a Local Security Policy on the RRAS server. I may have
to use a group policy on the client computers. Thanks for all the help
it was a very interesting problem.


Steven L Umbach wrote:
Thanks for the update Greg. By that way are you using ipsec policies on the
client computers or just on the RRAS server doing NAT?? My assumption was
that it was configured on the client computers themselves.

Steve


"Greg O" <gregorme@xxxxxxxxx> wrote in message
news:1154245441.418733.89760@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx

Hi Steven,
It looks like I found the answer on the IPSEC forum, and it is
impossible for rules to permit individual web sites (as I suspected).
The reason is if the server is running RRAS then NAT occurs before
IPSEC, and so IPSEC doesn't see the IP addresses of internal computers
on the network. Consequently it cannot filter the external traffic.


Steven L Umbach wrote:
The newsgroup is Microsoft.public.windows.networking.ipsec. If your ISP
does
not have it available create an account in your newsreader program [I use
Outlook Express] to use news.microsoft.com. That newsgroup is not very
active but I would still post there and check back periodically.

Steve


"Greg O" <gregorme@xxxxxxxxx> wrote in message
news:1153570894.767864.222160@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
I couldn't find any newsgroup that had IPSEC in the name, I posted a
link to this thread to server.general. Do you have an URL for this
newsgroup?


Steven L Umbach wrote:
I have not used that many filter lists for subnets in an ipsec rule to
see
how it works. It sounds like you are doing everything right but that
the
weighting is not working as expected. It might be worthwhile to also
posting
the ipsec newsgroup as often a member of the MS ipsec team will reply
to
posts there.

Steve

"Greg O" <gregorme@xxxxxxxxx> wrote in message
news:1153451512.873657.30310@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx

Yes, rules like this work on an internal subnet. For example to
block
internet access I use a general block, then there are 3 internal
subnets. I permit all traffic from subnet 1 to subnet 2, subnet 2 to
subnet 3 and subnet 3 to subnet 1. If I then try to permit specific
IP
addresses or even a subnet on the internet it doesn't work. So say
for
nytimes.com I try to permit 199.0.0.0 to and from 192.168.0.0 (as 2
subnets but one internal and one external) it doesn't work. I wonder
if
a recent patch caused this problem.




Steven L Umbach wrote:
It does sound like you are running into issues with rule weighting
that
are
contrary to what is believed to work. Have you tried using a
default
block
all IP rule and then add the allowed exceptions such as all traffic
to
your
local subnet [which should also allow DNS since you domain
controllers
do
DNS] and then port 80 TCP to the websites you want to access?

Steve


"Greg O" <gregorme@xxxxxxxxx> wrote in message
news:1153315840.492516.314830@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
I can isolate the problem to being with IPSEC as follows.
1. Turn off IPSEC. Browser loads the same page with
www.nytimes.com
and
199.239.236.200.
2. Turn on IPSEC which has a general rule blocking all TCP
traffic
to a
subnet with a low weighting and a more specific rule permitting
TCP
traffic to and from 199.239.236.200 and the same subnet with a
higher
weighting. You can't allow traffic in IPSEC to a domain name, it
just
makes up a list of filters to the IP addresses recorded in DNS
for
that
name. You can permit DNS queries though in IPSEC. When IPSEC is
turned
on www.nytimes.com and 199.239.236.200 both don't connect.
Therefore
IPSEC is blocking access to this web site.
3. In IPSEC delete the general rule blocking all TCP traffic to
the
subnet. Then www.nytimes.com and 199.239.236.200 both connect
again.
Therefore the general rule in IPSEC even though it has a lower
weighting (I checked this already in IP Security Monitor) is
still
overriding the permit rule for 199.239.236.200. I tried varying
the
specific rule to different IP addresses, and nothing helped. I
tried
making the specific rule more general, so any traffic to or from
199.239.236.200 to anywhere is permitted and it was still
blocked. I
tried any traffic to or from 199.239.236.200 on port 80 to a
specific
subnet, but that didn't work.
As far as I can tell I am not doing anything wrong. There are
only
a
few settings so it is hard to make a mistake.
Here's what I think is happening. If I block all traffic with a
general rule and then permit some with a specific rule on the
internal
LAN then that works. If the specific rule is for connecting to
the
Internet then it doesn't work. So it seems for some reason IPSEC
won't
do this for the Internet but it will on an internal network. BTW
this
is with 2003 server standard with all patches up to date. I first
noticed this problem a few months ago and put it aside thinking I
was
making a mistake somewhere.
The simplest way is to try it yourself. Use say a local security
policy on the gateway server, this is what I do. Block all TCP
even
all
traffic to a particular subnet from the gateway server. Then try
and
make a specific rule to connect to the internet from that subnet.
Thanks for all the help, but I am thinking that for some reason
IPSEC
just can't do this.




Steven L Umbach wrote:
I am a bit confused. I though before you said you could access
the
website
by putting the IP address in the address bar but now you are
saying
you
can
not? It is not unusual not to be able to access a website by
entering
the
IP
address in the address bar. If you have a Windows 2003 Server
that
you
can
use for testing you might want to try that because then you can
use
netsh
to
enable auditing of dropped traffic for ipsec that can help in
troubleshooting ipsec rules. You also may want to try using your
ipsec
rule
to see if you can access a simple web server on your network.
69.94.43.76
is an IP that I can use in the address bar to access a website.
Just
to
verify your ipsec rules for http should be a default rule to
block
all
for
source:my IP, destination:any IP, source port:any, destination
port:80,
protocol:TCP, and filter action block. Then for the exceptions
source:my
IP, destination:allowed website IP, source port:any, destination
port:80,
protocol:TCP, and filter action permit. The link below on ipsec
rule
weighting may be of help.

Steve

http://www.microsoft.com/technet/community/columns/cableguy/cg0205.mspx


"Greg O" <gregorme@xxxxxxxxx> wrote in message
news:1153210871.974270.118290@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx

BTW nytimes.com is just an example, there are other web sites
I
want
to
allow as well. The problem is not a DNS one because I can do
the
following:
1. Make a rule in IPSEC for a domain nytimes.com. That queries
DNS
and
automatically creates 4 rules with specific IP addresses e.g.
199.239.136.200 (I think from memory) and adds these into
IPSEC.
So
now
I have a policy that is the general block all TCP traffic, and
a
specific one that says allow these 4 IP addresses to the
particular
subnet. If I put any of these 4 IP addresses into the browser
(instead
of www.nytimes.com) then DNS is bypassed since it is the IP
address
I
am using. I try it and can't get the web site. If I delete the
rule
that blocks all TCP traffic I get the web site. If I unassign
the
policy I get the web site. So the only variable here is
whether I
have
the rule blocking all TCP traffic, DNS is not being used. Of
course
the
DNS issue is another problem, if I get the IP addresses
connecting I
can at least use them in favourites for a workaround.
I have tried other web sites too and couldn't connect with
the
IPSEC
policy on with any of them.


Steven L Umbach wrote:
Are you sure that when a user enters nytimes in their address
bar
that
it
is
resolving to an IP address in the allow list? What you could
do
on
a
client
computer is run ipconfig /displaydns to see if the IP address
shown
for
nytimes is in the allow list or try using TDImon from
Sysinternals
to
view
the IP traffic in real time looking for port 80 outbound
traffic.
Another
thing I would try is to create a hosts file on a client
computer
with
the
IP
address or addresses for nytimes to see if that works or not
which
would
insure only the IPs in the hosts file are used. To answer an
earlier
question, yes ipsec filters are weighted such that a specific
rule
overrides
a general rule. Unfortunately I don't believe you can enable
logging
for
ipsec in XP like you can for Windows 2003 to see events for
dropped
traffic.
I tend to think the problem is that an IP address not on the
allow
list
is
being used sometimes.

Steve


"Greg O" <gregorme@xxxxxxxxx> wrote in message
news:1153188726.753104.275010@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
Hi Steve,
The IP addresses IPSEC sets up are correct. I can check
that
by
using those addresses directly in the address bar of the
browser,
e.g.
instead of www.nytimes.com I put the IP address IPSEC added
to
the
allow filter and the page opens. So the IP addresses IPSEC
find
(it
does a DNS search for them) are sufficient to open the web
pages.
Also
it is necessary to allow DNS servers in IPSEC so you can
put
"www.nytimes.com" in the address bar and the DNS server
will
return
the
IP address for it. This part works, the DNS server of my
ISP
returns
an
IP address in the IPSEC allow list, but still it doesn't
allow
the
packets through for the IP address itself.
The feature in IPSEC is very useful if it works because
people
can
give a list of web sites they want to visit, and no other
web
sites
are
allowed. So this list of web sites might be added to group
policy
and
this is quite secure if those sites are safe. The allow
function
works
well for internal use. For example I can use a filter to
block
all
TCP
and UDP traffic, and then allow all TCP traffic from a
first
subnet
to
a second subnet (both internal). This works, and the
traffic
in
the
internal subnets is allowed, and outside those subnets is
completely
blocked. But if I do the same thing, allow all traffic from
a
first
internal subnet to an external IP address (even allowing
all
ports
from
that address) IPSEC doesn't allow it. I'm only using RRAS
for
a
firewall and if I turn off the IPSEC blocking of all TCP
the
internet
all works.



Steven L Umbach wrote:
No it is not a bug in ipsec. Many websites, especially the
larger
volume
websites use multiple websites links/IP addresses. What
you
want
to
do
may
work if you are trying to allow a simple website that uses
a
singe
or
a
couple IP address. You can see what I mean if you use
something
like
Ethereal while connecting connect to a website. Also when
you
enter a
DNS
name it will resolve to the IP addresses it currently
finds
to
create
the
filter. However I have seen many large websites then seem
to
use
dozens
of
IP addresses for their main website that seem to change
frequently
time
you
access them. You can sometimes see this when use nslookup
to
resolve a
domain name and try it a couple of times. A better
solution
would
be
to
use
something like ISA 2004 to restrict access though that is
not
a
trivial
investment in software/licenses and configuration time.
Otherwise
try
using
a packet sniffer like Ethereal to see if you can track
down
all
necessary
IPs needed to allow the website to work though again that
will
not
work
if
the website starts resolving to different IPs not included
in
the
filter
list. TDImon fee from SysInternals can also give you an
idea
of
IPs
and
ports/protocols the operating system accesses when
connecting
to
a
website
and it does not need to be installed as an application.

Steve


"Greg O" <gregorme@xxxxxxxxx> wrote in message
news:1153148032.486898.123020@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
Hi,
I use IPSEC to control internet access on a domain. I
block
port
80
for
browsers and ports 8080 and 3128 for most internet
proxies.
I
also
block all UDP since most internet games will run on UDP
even
with
all
TCP blocked. I want to allow individual web sites into
the
domain
though. In IPSEC there is a setting for a particular
domain,
if
you
try
it with say nytimes.com it looks up DNS and makes
filters
with
each
of
the IP addresses listed there. IPSEC I think is supposed
to
work
so
that more specific filters (like allowing a web site)
override
more
general filters (like blocking port 80. So allowing the
IP
addresses
of
nytimes.com should make it work, but it is still
filtered
by
IPSEC.
I
know that's the problem because if I list the port 80
block
the
nytimes.com site starts working. Is this a big in IPSEC?
Also
is
there
another way to do this without IPSEC, I see that network
adaptor
filters and RRAS filters don't seem to have the settings
for
this.








.

Relevant Pages

  • Re: Problem with IPSEC
    ... rules like this work on an internal subnet. ... addresses or even a subnet on the internet it doesn't work. ... Turn off IPSEC. ... yes ipsec filters are weighted such that a specific rule ...
    (microsoft.public.windows.server.security)
  • Re: Problem with IPSEC
    ... various policies on in IPSEC and activate them in task scheduler. ... Consequently it cannot filter the external traffic. ... rules like this work on an internal subnet. ... addresses or even a subnet on the internet it doesn't work. ...
    (microsoft.public.windows.server.security)
  • Re: Single 2003 Server with DHCP, DNS and ISA 2006
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    (microsoft.public.windows.server.general)
  • Re: Problem with IPSEC
    ... the ipsec newsgroup as often a member of the MS ipsec team will reply to ... rules like this work on an internal subnet. ... addresses or even a subnet on the internet it doesn't work. ... yes ipsec filters are weighted such that a specific ...
    (microsoft.public.windows.server.security)
  • Re: Site VPN between SBS 2003 and Windows 2003/ISA 2004
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