How works WebAgent ACO parameter CustomIPHeader

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Article ID: 36859

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Updated On:

Products

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

Issue/Introduction

 

We want to know how the ACO parameter customipheader works ? 

We want to know the expected behaviour among these 4 configurations of
that parameter :

  1 - when there's no header;
  2 - when the header is set with 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 value in the SMSESSION cookie.
 
The Web Agent only accept 1 single value is motivated by security
concerns.

CustomIPHeader accepts single value because of security attacks
possible if SiteMinder would allows multiple values :

Sample of an attack :
 
  1. "Alice" logs into SiteMinder with IP 111.111.111.111;
  
  2. "Mallory" has IP 2.2.2.2;

  3. "Mallory" captures "Alice's" SiteMinder credential and learns her
      IP;
  4. "Mallory" configures his browser to send "Alice's" cookie along
      with the header "x-forwarded-for: 111.111.111.111";

  5. Mallory issues a request to MyHR, ENET, or Authoria;

  6. Proxy modifies the XFF(X-Forwarded-For) header to be
      "111.111.111.111,2.2.2.2";

  7. The Web Agent runs the IP check;

  8. The credential contains IP 111.111.111.111;

  9. The REMOTE_ADDR is Proxy, so XFF will be used;

  10. The first 15 characters of XFF are 111.111.111.111;

  11. IP check passes, because 111.111.111.111 = 111.111.111.111;

  12. Mallory is interactively logged into ACS applications as Alice;