How Do I Connect to Active Directory Server Behind a Firewall

Question

I'm having trouble getting LDAP queries to reach my Active Directory running on Windows Server 2012 R2 behind a Cisco PIX 506E firewall. My goal is to create a SSO environment for some applications that are hosted in the cloud (on Digital Ocean). I have full control of the entire network path to the server, and I have opened ports 389 (LDAP) and 636 (LDAPS) on the PIX and added a static statement to forward the LDAP traffic to the AD server. As I will show below, I'm getting a hit count on the firewall access-list each time I attempt to make a connection, but I am unsuccessful.

Here's what I have done so far:

1. Opened LDAP and LDAPS ports on Firewall

fw1(config)# show access-list
access-list cached ACL log flows: total 0, denied 0 (deny-flow-max 1024)
            alert-interval 300
access-list inbound; 4 elements
access-list inbound line 1 permit icmp any any (hitcnt=383)
access-list inbound line 2 permit udp any interface outside eq 1194 (hitcnt=3)
access-list inbound line 3 permit tcp any any eq ldap (hitcnt=6)
access-list inbound line 4 permit tcp any any eq ldaps (hitcnt=1)

2. Port Forwarded the LDAP Traffic

fw1(config)# show static
static (inside,outside) udp interface 1194 172.23.6.148 1194 netmask 255.255.255.255 0 0
static (inside,outside) tcp interface ldap 172.23.6.127 ldap netmask 255.255.255.255 0 0
static (inside,outside) tcp interface ldaps 172.23.6.127 ldaps netmask 255.255.255.255 0 0

3. Turned off firewall on the AD Server

4. Used Microsoft's PortQuery Tool to test if the LDAP ports are really open

5. Used netstat to verify that the AD server is actually listening on port 389

At this point I feel like I'm not doing something right on the firewall. Although I have a similar setup for an OpenVPN server and that's working fine (i.e., the ACL and Static statements are getting traffic through the firewall to the OpenVPN server successfully).

I'm willing to provide any additional information needed to help me solve this, thanks.

PS. Below is the config of my PIX firewall.

fw1(config)# sho conf
: Saved
: Written by enable_15 at 22:16:51.652 EST Sat Oct 25 2014
PIX Version 6.3(5)
interface ethernet0 auto
interface ethernet1 auto
nameif ethernet0 outside security0
nameif ethernet1 inside security100
enable password ***** encrypted
passwd ***** encrypted
hostname fw1
domain-name ctc.local
clock timezone EST -5
fixup protocol dns maximum-length 512
fixup protocol ftp 21
fixup protocol h323 h225 1720
fixup protocol h323 ras 1718-1719
fixup protocol http 80
fixup protocol rsh 514
fixup protocol rtsp 554
fixup protocol sip 5060
fixup protocol sip udp 5060
no fixup protocol skinny 2000
fixup protocol smtp 25
fixup protocol sqlnet 1521
fixup protocol tftp 69
names
access-list inbound permit icmp any any
access-list inbound permit udp any interface outside eq 1194
access-list inbound permit tcp any interface outside eq 1194
access-list inbound permit tcp any any eq ldap
access-list inbound permit udp any any eq 389
pager lines 24
logging monitor notifications
logging buffered debugging
icmp permit any outside
icmp permit any inside
mtu outside 1500
mtu inside 1500
ip address outside MY_PUBLIC_IP 255.255.255.248
ip address inside 172.23.6.120 255.255.255.0
ip audit info action alarm
ip audit attack action alarm
pdm location 172.23.6.0 255.255.255.0 inside
pdm logging informational 100
pdm history enable
arp timeout 14400
global (outside) 1 interface
nat (inside) 1 172.23.6.0 255.255.255.0 0 0
static (inside,outside) udp interface 1194 172.23.6.148 1194 netmask 255.255.255.255 0 0
static (inside,outside) tcp interface ldap 172.23.6.127 ldap netmask 255.255.255.255 0 0
access-group inbound in interface outside
route outside 0.0.0.0 0.0.0.0 ISP_ROUTER_IP 1
timeout xlate 0:05:00
timeout conn 1:00:00 half-closed 0:10:00 udp 0:02:00 rpc 0:10:00 h225 1:00:00
timeout h323 0:05:00 mgcp 0:05:00 sip 0:30:00 sip_media 0:02:00
timeout sip-disconnect 0:02:00 sip-invite 0:03:00
timeout uauth 0:05:00 absolute
aaa-server TACACS+ protocol tacacs+
aaa-server TACACS+ max-failed-attempts 3
aaa-server TACACS+ deadtime 10
aaa-server RADIUS protocol radius
aaa-server RADIUS max-failed-attempts 3
aaa-server RADIUS deadtime 10
aaa-server LOCAL protocol local
http server enable
http 192.168.1.0 255.255.255.0 inside
http 172.23.6.0 255.255.255.0 inside
no snmp-server location
no snmp-server contact
snmp-server community public
snmp-server enable traps
floodguard enable
telnet timeout 5
ssh 172.23.6.0 255.255.255.0 inside
ssh 172.23.7.0 255.255.255.0 inside
ssh timeout 60
console timeout 0
dhcpd lease 3600
dhcpd ping_timeout 750
dhcpd auto_config outside
terminal width 80
Cryptochecksum:****

Solution

Don't open services on your domain controllers to the Internet. Configure a VPN between your digital ocean footprint and your on-prem Active Directory and query AD over the VPN.

Comments

[joeqwerty]

At this point I feel like I'm not doing something right on the firewall - You're not doing something right. First, don't do it this way, use a VPN as MDMarra stated in his answer. Second if you insist on doing it this way then you're going to need more than just LDAP traffic to pass through. - technet.microsoft.com/en-us/library/dd772723(v=ws.10).aspx

[Kismet Agbasi]

Thanks, I will follow MDMarra's suggestion. Thanks also for providing the article on Technet, I'll check that out too.

[Kismet Agbasi]

Thanks. I just got home and I'll test your suggestion to see how that works out. I'll report back my findings shortly.

[Kismet Agbasi]

Thanks for your suggestion again. I did some research and discovered that I could use Tinc to create a VPN between my cloud and on-premise servers. I've been able to set it up, but I can't ping any of the LAN IPs at the local site. So that's what I'm battling now, in case you can offer some pointers. Thanks.