Thursday, November 18, 2010

Watchguard PPTP VPN user validation via RADIUS using Cisco ACS 4.2

Wow that title is a mouthful.

A customer has a Watchguard Firebox firewall and a Cisco ACS, all the users for Cisco related activities are on the ACS and the customer wants to migrate all the PPTP VPN users from the firewall to the Cisco ACS.

Both the ACS and Firebox support RADIUS, so it sounds quite easy.

I did the initial configuration; creating the AAA client in the ACS, changing the VPN configuration on the watchguard so it asks the ACS for the users, creating a test user and a test group with the following RADIUS parameters:

[011] Filter-Id PPTP-Users

[311\007] MS-MPPE-Encryption-Policy "Encryption Required"
[311\008] MS-MPPE-Encryption-Types "128-bit"
[311\012] MS-CHAP-MPPE-Keys 
[311\016] MS-MPPE-Send-Key 
[311\017] MS-MPPE-Recv-Key

Testing with a Windows 7 Enterprise client, I got the error:

Error 734: The PPP link control protocol was terminated. 

The logs on the firewall showed:

level=''3'' msg=''pri=''3'' msg_id=''1401-3003'' msg=''pptp MSCHAPv2 authentication ok for peer wg''''
level=''7'' msg=''sent [CHAP Success id=0x32 ''S=5F85A740C65AD93F308ED6681B455486FC2EF4F5 M=Access granted'']'' new_msg='' level=''7'' msg=''sent [CHAP Success id=0x32 ''S=5F85A740C65AD93F308ED6681B455486FC2EF4F5 M=Access granted'']'''' Debug
pppd[1255] MPPE required, but keys are not available. Possible plugin problem?
pppd MPPE required but not available'''

Basically the issue seemed to be MPPE related, since the configuration requires encryption, no MPPE = no VPN.

In the ACS the authentication showed as successful and little else. I checked and double checked the RADIUS attributes. After sometime with Watchguard support, they suggested to get a packet capture of the ACS RADIUS response:

Using Wireshark, it was clear that the ACS was not sending any MPPE related attributes and in fact the only Microsoft attribute was the one indicating that the authentication was OK. 

I replicated the VPN configuration using a cisco router and it worked without issues, after that, I was checking everything again and noticed that the cisco router was defined in the ACS AAA client section as "RADIUS (Cisco IOS/PIX 6.0)" while the Watchguard Firewall was defined as "RADIUS (IETF)"

I changed the firewall to "RADIUS (Cisco IOS/PIX 6.0)" and ta-da, everything worked.

All the Microsoft attributes were there and all was well in the land. Of course after reading the ACS help, it seems obvious:

"RADIUS (IETF). These are the standard IETF RADIUS attributes. Select this option if you are using devices supporting RADIUS but do not need to make use of the vendor-specific attributes (VSA) of the manufacturer.

RADIUS (Cisco IOS/PIX 6.0) Select the RADIUS (Cisco IOS) option when using a Cisco Systems IOS device as a AAA client. This option enables you to make use of the Cisco IOS and PIX 6.0 RADIUS VSAs."

IPexpert Contest Entry

There was/is my entry for the Free CCIE bootcamp/I love IPexpert Nov contest at IPexpert:

I replicated the logo using utp cables, serial cables, octopus cables, console cables and router faceplates, great fun with the help of @scontreraf and @coolbomb

The final image:

One of the many of how it was done:

Monday, November 8, 2010

Cisco IOS Site-to-Site IPSec VPN using Certificates

After a couple of weeks trying to get a Site-to-Site IPSec tunnel to work using a Watchguard firewall, I decided to simply do it with a Cisco Router.

These are the steps involved in the configuration, hopefully this will help someone else or myself in the future.

In my particular case, the remote end uses certificates for the VPN and has a Certification Authority, so first we have to generate a certificate and ask them to sign it, the CSR can be generated on the IOS but for backup purposes I always tend to use openssl, that way if the router/firewall dies, we have backups:

openssl req -new -nodes -keyout example.key -out example.csr

Generating a 1024 bit RSA private key
writing new private key to 'example.key'
You are about to be asked to enter information that will be incorporated
into your certificate request.
What you are about to enter is what is called a Distinguished Name or a DN.
There are quite a few fields but you can leave some blank
For some fields there will be a default value,
If you enter '.', the field will be left blank.
Country Name (2 letter code) [AU]:
State or Province Name (full name) [Some-State]:
Locality Name (eg, city) []:
Organization Name (eg, company) [Internet Widgits Pty Ltd]:
Organizational Unit Name (eg, section) []:
Common Name (eg, YOUR name) []:
Email Address []:

Please enter the following 'extra' attributes
to be sent with your certificate request
A challenge password []:
An optional company name []:

Now that the CSR its done, the CA has to sign it.

After the CA does the signing, we need to import the certificates into the IOS device. There are many ways of doing this, but I prefer the PKCS#12 method since it's self-contained and simpler.

To use PKCS#12, we need to create the p12 file, I do this with openssl:

openssl pkcs12 -export -in example.cer -inkey example.key -certfile ca.cer -name "name" -out example.p12
Enter Export Password:
Verifying - Enter Export Password:

Now that we have the certificate signed and in PKCS#12 format, we have to import it to the IOS device, for that we have to create a pki trustpoint:

R1(config)#crypto pki trustpoint EXAMPLE-VPN
R1(ca-trustpoint)#revocation-check none

With the trustpoint created, we can import the certificate. There are several methods, I use TFTP:

R1(config)#crypto ca import EXAMPLE-VPN pkcs12 tftp: PASSWORD
% Importing pkcs12…
Address or name of remote host []?
Source filename [trustpoint]? example.p12
Reading file from tftp://
Loading example.p12 from (via FastEthernet0/0): !
[OK - 1245 bytes]

CRYPTO_PKI: Imported PKCS12 file successful

We can verify that everything was imported correctly with the commands:

show crypto pki trustpoints
show crypto pki certificates

Now that the certificates are out of the way, we can focus on the VPN configuration itself.

The tunnel parameters for this example are:

IKE Phase 1
  • Encryption 3DES
  • Hash SHA
  • DH-Group 2

IKE Phase 2
  • ESP-3DES-MD5
  • Local Network:
  • Remote Network:

IKE Phase 1:

crypto isakmp policy 1
encr 3des
authentication rsa-sig
hash sha
group 2

This can be verified using show crypto isakmp policy


crypto ipsec transform-set TRANSFORM-SET-NAME esp-3des esp-md5-hmac

This can be verified using show crypto ipsec transform-set

Interesting traffic and NATing the source:

Lets assume that my network is, the remote network and that the remote side has told me that all of my traffic has to come from

ip access-list extended NAT-IP-VPN
permit ip host

ip nat pool VPN-NAT prefix-length 30

ip nat inside source list NAT-IP-VPN pool VPN-NAT overload

ip access-list extended TRAFFIC-VPN
permit ip host

Be careful with the NAT because if you have more than one statement the order matters. This can be verified using show ip nat translations, show access-lists

Crypto Map:

This is where we put it all together for the IKE Phase 2

crypto map VPN-Map-1 10 ipsec-isakmp
set peer
set security-association lifetime seconds 86400
set transform-set TRANSFORM-SET-NAME
match address TRAFFIC-VPN

Apply the crypto map/nat on the interfaces:

interface FastEthernet0/0
description LAN
ip nat inside

interface ATM0.1 point-to-point
description WAN
ip nat outside
crypto map VPN-Map-1


Now all we have to do is generate interesting traffic and test what happens, some useful commands are show crypto isakmp sa and show crypto ipsec sa.

Useful Links:

Wednesday, November 3, 2010

Basic Cisco ASA 8.2 Template

A basic Cisco ASA 8.2 template.This is meant to used as a starting point for a production configuration and obviously it has to be customized to meet your particular security requirements.

This templates uses:

*3 Interfaces (outside, inside10.0.0.0/24 and dmz
*Management interface (
*Banner for motd and ADSM.
*CET/CEST timezone.
*Firewall/NAT rules that allow IP/icmp traffic from inside to outside with nat, inside to dmz without nat, dmz to outside with nat.
*Static NATs for both dmz and inside hosts (tcp 80 and tcp 8080).
*AAA configuration with a local validation in case the AAA servers are unreachable or down (notacacsuser).
*SNMP access
*SSH/ASDM access everywhere except the dmz


ASA Version 8.2(3) 
interface GigabitEthernet0/0
 nameif outside
 security-level 0
 ip address 
interface GigabitEthernet0/1
 nameif inside
 security-level 100
 ip address 
interface GigabitEthernet0/2
 nameif dmz
 security-level 50
 ip address 
interface Management0/0
 nameif management
 security-level 100
 ip address 
banner motd -----------------------------------------------
banner motd WARNING: You have accessed a restricted system.
banner motd -----------------------------------------------
banner asdm -----------------------------------------------
banner asdm WARNING: You have accessed a restricted system.
banner asdm -----------------------------------------------
ftp mode passive
clock timezone CEST 1
clock summer-time CEST recurring last Sun Mar 2:00 last Sun Oct 2:00
dns server-group DefaultDNS
object-group service Web8080 tcp
 port-object eq 8080
access-list inside_access_in extended permit icmp any 
access-list inside_access_in extended permit ip any 
access-list inside_access_in extended permit icmp 
access-list outside_access_in extended permit icmp any any 
access-list outside_access_in extended permit tcp any interface outside eq www 
access-list outside_access_in extended permit tcp any interface outside object-group Web8080 
access-list dmz_access_in extended permit icmp echo-reply 
access-list dmz_access_in extended deny ip 
access-list dmz_access_in extended permit ip any 
access-list dmz_access_in extended deny icmp 
access-list dmz_access_in extended permit icmp any 
pager lines 24
logging enable
logging timestamp
logging buffer-size 96000
logging buffered debugging
logging asdm informational
logging host outside
mtu outside 1500
mtu inside 1500
mtu dmz 1500
mtu management 1500
no failover
icmp unreachable rate-limit 1 burst-size 1
asdm image disk0:/asdm-634-53.bin
no asdm history enable
arp timeout 14400
global (outside) 1 interface
nat (inside) 1
nat (dmz) 1
static (inside,outside) tcp interface www www netmask 
static (dmz,outside) tcp interface 8080 www netmask 
static (dmz,outside) netmask 
static (inside,dmz) netmask 
access-group outside_access_in in interface outside
access-group inside_access_in in interface inside
access-group dmz_access_in in interface dmz
route outside 1
timeout xlate 3:00:00
timeout conn 1:00:00 half-closed 0:10:00 udp 0:02:00 icmp 0:00:02
timeout sunrpc 0:10:00 h323 0:05:00 h225 1:00:00 mgcp 0:05:00 mgcp-pat 0:05:00
timeout sip 0:30:00 sip_media 0:02:00 sip-invite 0:03:00 sip-disconnect 0:02:00
timeout sip-provisional-media 0:02:00 uauth 0:05:00 absolute
timeout tcp-proxy-reassembly 0:01:00
dynamic-access-policy-record DfltAccessPolicy
aaa-server tacacs protocol tacacs+
aaa-server tacacs (management) host
 key tacacssecret
aaa authentication ssh console tacacs LOCAL
aaa authentication telnet console tacacs LOCAL
aaa authentication serial console tacacs LOCAL
aaa authentication enable console tacacs LOCAL
aaa authentication http console tacacs LOCAL
aaa authorization command tacacs LOCAL
http server enable
http management
http inside
http outside
snmp-server host inside poll community test version 2c
snmp-server location LOCATION
snmp-server contact
snmp-server enable traps snmp authentication linkup linkdown coldstart
sysopt noproxyarp outside
sysopt noproxyarp inside
sysopt noproxyarp dmz
sysopt noproxyarp management
crypto ipsec security-association lifetime seconds 28800
crypto ipsec security-association lifetime kilobytes 4608000
telnet timeout 5
ssh outside
ssh inside
ssh management
ssh timeout 5
ssh version 2
console timeout 5
threat-detection basic-threat
threat-detection statistics access-list
threat-detection statistics tcp-intercept rate-interval 30 burst-rate 400 average-rate 200
ntp server
username notacacsuser password notacacsuser privilege 15