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ASA: ScanSafe step by step configuration

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Documentation

This configuration example is meant to be  interpreted with the aid of the official documentation from the  configuration guide located here:

http://www.cisco.com/en/US/docs/security/asa/asa90/configuration/guide/protect_cloud_web_security.html

 

Prerequisite

The ASA must be running minimum 9.0 code or above to be able to configure ScanSafe feature.

 

Limitations

1. IPV6 is not supported

2. Transparent mode is not supported

3. ASA clustering is not supported

4. Clientless SSL VPN is not supported

5. Cloud Web Security is not supported with the ASA CX module

6.The match default-inspection-traffic command does not include the default ports for the Cloud Web Security inspection (80 and 443).

 

Topology

topology.jpg

How ScanSafe works

1. Client PC tries to go to linkedin.com

2. This request is received by the ASA and it optionally retrieves the user and/or group information

3. ASA redirects the request to the Scan Safe Towers.

4. ASA acts as a proxy, changes the destination IP address and  port in the client requests and adds tower specific HTTP  headers and then sends the modified request to the Towers.

5. Based on the policies configured on the Tower, the reqeust is allowed or a blocked page is sent to the client PC.

 

Step by Step Configuration

1. Configure scansafe config

scansafe general-options

  server primary fqdn proxy193.scansafe.net port 8080

  server backup fqdn proxy1363.scansafe.net port 8080

  retry-count 5

  license <license key>

2. Create two access-lists to match http and https traffic

access-list http-traffic extended permit tcp any any eq www

access-list https-traffic extended permit tcp any any eq https

3. Create two class-maps to match both traffic

class-map http-class

  match access-list http_traffic

 

  class-map https-class

  match access-list https_traffic

4. Optional Whitelist

class-map type inspect scansafe match-any whitelist1

match user user1 group cisco

match user user2

match group group1

match user user3 group group3

5. Create two L-7 policy maps for http and https and call the optional whitelist

policy-map type inspect scansafe http-pmap

  parameters

  default group httptraffic

   http

  class whitelist1

   whitelist

policy-map type inspect scansafe https-pmap

  parameters

default group httpstraffic

  https

class whitelist1

  whitelist

 

6. Create new policy-map and configure scansafe inspection

policy-map inside-policy

  class http-class

   inspect scansafe http-pmap fail-close

  class https-class

   inspect scansafe https-pmap fail-close

7. Apply the policy to the interface

service-policy inside-policy interface inside

Final Configuration Section:

scansafe general-options

server primary fqdn proxy193.scansafe.net port 8080

server backup fqdn proxy1363.scansafe.net port 8080

retry-count 5

license <license key>

!

access-list http-traffic extended permit tcp any any eq www

access-list https-traffic extended permit tcp any any eq https

!

class-map http-class

match access-list http_traffic

 

class-map https-class

match access-list https_traffic

!

policy-map type inspect scansafe http-pmap

parameters

  default group httptraffic

  http

  class whitelist1

   whitelist

policy-map type inspect scansafe https-pmap

parameters

  default group httpstraffic

  https

  class whitelist1

   whitelist

!

policy-map inside-policy

class http-class

  inspect scansafe http-pmap fail-close

class https-class

  inspect scansafe https-pmap fail-close

!

service-policy inside-policy interface inside

 

Show commands and debugs:

1. show scansafe server

ASA# sh scansafe server

Primary: 70.39.176.3 (REACHABLE)*

Backup: 70.39.231.99

2. debug scansafe 255

Comments
Beginner

Great config!

Important note to others (as this happened to us): When you apply the service-policy called "inside-policy" on the inside interface, it will replace the default policy. (the one with a global class, inspecting ftp and other protocols)

A quick fix to this is to simply add the global-class inspections to the newly created "inside-policy"(otherwise things like ftp would break..trim down as needed.):

policy-map inside-policy

class http-class

  inspect scansafe http-pmap fail-close

class https-class

  inspect scansafe https-pmap fail-close

class global-class

  inspect ftp

  inspect h323 h225

  inspect h323 ras

  inspect ip-options

  inspect netbios

  inspect rsh

  inspect rtsp

  inspect sqlnet

  inspect sunrpc

  inspect tftp

  inspect xdmcp

  inspect dns dynamic-filter-snoop

To add the to access-list configs: If there are http/https destinations in which you do NOT want redirected (such as intranet websites or other speciatly cloud apps that don't play nice with a proxy), you can modify the access lists to include deny statements (effectively, denying redirection, so it routes as normal):

access-list http-traffic remark Do not redirect internal web servers

access-list http-traffic extended deny tcp any object-group internal-web-servers eq www

access-list http-traffic remark Ignore traffic sourced from another internal proxy

access-list http-traffic extended deny tcp host 10.10.10.1 any eq www

access-list http-traffic extended permit tcp any any eq www

access-list https-traffic extended permit tcp any any eq https

I also included an example to deny a source, which would be useful if you currently have a proxy appliance that clients are being redirected to. The current proxy could be ignored, and clients could be gradually moved from the old to the new scan safe redirection. The deny statements should be replicated to the https-traffic ACL as needed.

Hello,

May I ask if there is need to configure the VPN tunnel between ASA acting as proxy for http/https traffic and the ScanSafe towers?

 

Thank you.

 

 

Beginner

Hello,

 

Yes, two SSL tunnels leading to two CWS towers are configured as part of establishing communication from ASA to CWS cloud. 

These tunnel are not regular SSL VPN tunnels. They are configured using CWS commands on ASA.

 

Regards,

Tomas

Beginner

I am running into a problem with ACL whitelisting internal websites:

 

access-list scansafe-http extended deny tcp any 192.168.253.0 255.255.255.0 eq www

access-list scansafe-http extended permit tcp any any eq www

access-list scansafe-https extended deny tcp any 192.168.253.0 255.255.255.0 eq https

access-list scansafe-https extended permit tcp any any eq https

 

and I can see the drops the policy:


Global policy:
  Service-policy: global_policy
    Class-map: inspection_default
    Class-map: http-class
      Inspect: scansafe http-pmap fail-open, packet 6667, lock fail 0, drop 0, reset-drop 0, v6-fail-close 0
Number of whitelisted connections: 0
Number of connections allowed without scansafe inspection because of "fail-open" config: 0
Number of connections dropped because of "fail-close" config: 0
Number of HTTP connections inspected: 179
Number of HTTPS connections inspected: 0
Number of HTTP connections dropped because of errors: 0
Number of HTTPS connections dropped because of errors: 0
    Class-map: https-class
      Inspect: scansafe https-pmap fail-open, packet 40703, lock fail 0, drop 6, reset-drop 19, v6-fail-close 0
Number of whitelisted connections: 0
Number of connections allowed without scansafe inspection because of "fail-open" config: 0
Number of connections dropped because of "fail-close" config: 0
Number of HTTP connections inspected: 0
Number of HTTPS connections inspected: 616
Number of HTTP connections dropped because of errors: 0
Number of HTTPS connections dropped because of errors: 0

 

any clue as to why this is happening ? the traffic is kept on the ASA, i.e. source is on the "inside" and destination is on "DMZ".

 

config:

class-map http-class

match access-list scansafe-http

class-map https-class

match access-list scansafe-https

class-map inspection_default

match default-inspection-traffic

!

policy-map type inspect scansafe https-pmap

parameters

  https

policy-map type inspect scansafe http-pmap

parameters

  http

policy-map global_policy

class inspection_default

  inspect dns preset_dns_map

  inspect h323 h225

  inspect h323 ras

  inspect rsh

  inspect rtsp

  inspect esmtp

  inspect sqlnet

  inspect skinny 

  inspect sunrpc

  inspect xdmcp

  inspect sip 

  inspect netbios

  inspect tftp

  inspect ip-options

  inspect ftp

  inspect icmp

  inspect icmp error

 class http-class

  inspect scansafe http-pmap fail-open

 class https-class

  inspect scansafe https-pmap fail-open

 class class-default

  user-statistics accounting

!

 

Beginner

Did you ever figure out why it wasn't bypassing internal servers?

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