Enabling IP Validation in Load Balancer Environment using ProxyTrustedList & ProxyRemoteIPHeaderVar in OAM 11g

Why we are discussing this topic?

• It is important to understand the configuration required to be done in OAM for validating the IP addresses when the application server is behind the proxies.

What difference will it make if app server is behind the proxy?

• The client ip calculation will be different if proxy is present.

How client ip is fetched in OAM/Webgate?

• remote_addr contains the client ip, in case of proxy this remote_addr will have the last proxy IP Address.

How can i than validate the IP in this scenario where proxies are used?

• For such scenario we have to configure 2 user defined parameters in Webgate Profile:

• ProxyRemoteIPHeaderVar = <by default it is set to HTTP_X_FORWADED_FOR>

• ProxyTrustedIPList = <list of comma seperated IP Addresses>

• Along with these parameter we need to set the IP Validation flag in webgate profile.

How remote_addr & x_forwaded_for header are related?

• Remote_addr: Actually it contains the IP address of the client in general. But in scenarios where proxies are involved, this remote_addr conatins the last proxy IP Address.

• HTTP_X_FORWARDED_FOR: header is a common method for identifying the originating IP address of a client connecting to a web server through an HTTP proxy or load balancer.

Considering the scenario such as:

Client -> Proxy1 -> Proxy2 -> OHS Server(having Webgate)
 

Thus in this scenario, the headers contains following values;

• REMOTE_ADDR = Proxy2 IP

• HTTP_X_FORWARDED_FOR = Client IP, Proxy1 IP

So how the ProxyTrustedIPList is to be configured?

• This parameter should have all the proxies IP Addresses that are present in the deployment or production environment.

How HTTP_X_FORWADED_FOR & ProxyTrustedIPList co-relates?

The IP Addresses present in x_forwaded_for header are backtracked against trustediplist & when the Ip is not found in TrustedList than that is considered to be the client ip.

Consider the scenario:
Client -> Proxy1 -> Proxy2 -> OHS Server(having Webgate)

Headers:

• HTTP_X_FORWADED_FOR = ClientIp, Proxy1

• REMOTE_ADDR = Proxy2

Configuration:

• ProxyTrustedIPList = Proxy1, Proxy2

 

Enjoy :-)