Web Server in a DMZ on a PIX 515 security help needed

Posted on 2010-08-15
Last Modified: 2013-12-04
I have a PIX 515 that has a DMZ. I need to place a web server in the DMZ and have it access a MS SQL server inside our network. The server is 2008 R2. My plan is to connect a switch to the DMZ interface and then connect the web server to the switch. For access back to our SQL server I was thinking of using the second NIC on the web server and connecting that to a vlan on the switch and placing the SQL server's second NIC on the same vlan, both NICs using a completely different subnet than that of our internal network. Of course I would open the respective ports on the PIX needed for access. The switch that is connected to the DMZ would only have the web server and the sql server's second nic connected to it on their own vlan.

Is this a good plan from a security and operational standpoint? Do you see anything wrong with this plan or have any suggestions? What is a best practice?

Question by:wayy2be
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Expert Comment

ID: 33443463
Well, your desing is good, but as per my experience, the practice followed is to have the default route of the Web server point to the interface of the firewall to which it is connected. The firewall will naturally have routes to pass traffic to the internal network (sql server). All u need to make sure is that only necessary ports and source are allowed to access the Web server and the SQL server, in the firewall.
LVL 28

Expert Comment

ID: 33445519
My recommendation would be to avoid the 2nd NIC scenario for SQL and the Web Server. Unless you have a massive amount of volume of SQL traffic just let it all pass through the NIC. With your design you will have direct exposure to the SQL server all ports should by chance the Web server become compromized, then should the SQL server become compromized an attacker will have access to your entire internal LAN. In effect you have created a bridge path around your PIX to your inside network.

You should work from the priciple of least privilege.

1. Create a subnet and add switch and web server to dmz interface on PIX
2. Create access and nat rules between ouside and dmz to allow access to web server on port 80 (and 443 if needed)
3. Create access and nat rules between dmz and inside to allow web server access only to SQL server on tcp 1433 (or whatever port your SQL is set to listen on)

Good Luck

Author Comment

ID: 33522647

That sounds much better. I will add a switch to the DMZ port on the 515 and connect the web server to that switch.  What commands do I need to use to configure steps 2 & 3?  I need outside users to access ports 80 and 443 and the web server needs to access ports 1433 on SQL server and 25 on our mail server. Any help you can provide would be great.  Thanks
LVL 28

Accepted Solution

bgoering earned 500 total points
ID: 33523017
You will need to create static statements and acls to permit the access - assumming your web server is ip a.a.a.a, sql server is ip b.b.b.b, mail server is ip c.c.c.c and new interface is called dmz it will look something like:

# allow access to web server
access-list outside_access_in extended permit tcp any host a.a.a.a eq http
access-list outside_access_in extended permit tcp any host a.a.a.a eq https

# allow web server to access inside sql and smtp
access-list dmz_access_in extended permit tcp host a.a.a.a host b.b.b.b eq 1433
access-list dmz_access_in extended permit tcp host a.a.a.a host c.c.c.c eq smtp

# define translation rules (assumming network starts with 0 and netmask is
# this also assumes that smtp and sql server are on network b.b.b.0
# defines routing for entire dmz network to outside and inside
static (dmz,outside) a.a.a.0 a.a.a.0 netmask
static (inside,dmz) b.b.b.0 b.b.b.0 netmask

If you have other inside networks to route to from dmz add static statements for those networks as well
Good Luck

Good Luck

Author Comment

ID: 33558439
Sounds good and thank you for the info. I cannot try this for a week or two and Experts Exchange keeps bombing me with "Abandoned Question" emails (Whats up with that?). What I will do is close the question and if I have difficulty I will repost. Thanks again for your help!

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