How works WebAgent ACO parameter CustomIPHeader

Products

• CA Single Sign On Secure Proxy Server (SiteMinder)
• CA Single Sign On SOA Security Manager (SiteMinder)
• CA Single Sign-On
• CA Single Sign On Agents (SiteMinder)
• SITEMINDER

Issue/Introduction

How does the ACO parameter customipheader works?

What is the expected behavior among these 4 configurations of that parameter:

1. When there's no header;
2. When the header is set to one value;
3. When the header is set with 2 values;
4. When the header is set with n > 2 values.

 

Resolution

By default, the Web Agent obtains the requesting client's IP address from the Web Server variable REMOTE_ADDR (Remote Address) that the Web Server sets for a particular request.

The Web Agent stores the client's IP address as the value in the SMSESSION cookie.
 
The Web Agent only accepts 1 single value motivated by security concerns.

CustomIPHeader accepts a single value, because security attacks are possible if SiteMinder would allow multiple values:

Sample of an attack:

1. "<user1>" logs into SiteMinder with IP 10.0.0.1;
2. "<user2>" has IP 192.168.1.1;
3. "<user2>" captures "<user1>'s" SiteMinder credential and learns its IP;
4. "<user2>" configures his browser to send "<user1>'s" cookie along with the header "x-forwarded-for: 10.0.0.1";
5. "<user2>" issues a request to MyHR, ENET, or Authoria;
6. Proxy modifies the XFF(X-Forwarded-For) header to be "10.0.0.1,192.168.1.1";
7. The Web Agent runs the IP check;
8. The credential contains IP 10.0.0.1;
9. The REMOTE_ADDR is a Proxy, so XFF will be used;
10. The first 15 characters of XFF are 10.0.0.1;
11. IP check passes because 10.0.0.1 = 10.0.0.1;
12. "<user2>" is interactively logged into ACS applications as "<user1>".