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This is a follow up from my earlier question on capturing the X-Forwarded-For IP address in across multiple proxies. Now, I'm looking to capture the Client's IP in the application's (Shibboleth's IdP) logs.

The follow is:

Client > Load Balancer > Apache httpd server > Tomcat server (running Shibboleth's IdP)

The variable with the Client's IP at the Load Balancer is ClientIP which I can capture in the web server's logs using LogFormat "%{ClientIP}i ... " and similarly in Tomcat's access logs using these inserver.xml`:

<Valve className="org.apache.catalina.valves.RemoteIpValve" 
protocolHeaderHttpsValue="https" />

<Valve className="org.apache.catalina.valves.AccessLogValve" 
pattern="%{ClientIP}i %h %l %u %t %r %>s %b %{Referer}i %{User-Agent}i" resolveHosts="false"/>

Now, I'm looking to capture this IP in Shibboleth's IdP audit logs. This discussion talks about using mod_rpaf for Apache but doesn't get into the details. I'm hoping to do without installing additional modules.

Looks like I'm missing a couple of (small?) pieces here. Any ideas? Many thanks!

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1 Answer 1

up vote 1 down vote accepted

After digging at LogBack's documentation on logging client IPs and the corresponding code for the MDCInsertingServletFilter servlet, turns out you must use the X-Forwarder-For header.

We replaced ClientIP with X-Forwarder-For in the load balancer, updated httpd.conf's LogFormat to log X-Forwarder-For, then updated Shibboleth's logging.xml file as follows for the audit logs:

<appender name="IDP_AUDIT" class="ch.qos.logback.core.rolling.RollingFileAppender">

  <rollingPolicy class="ch.qos.logback.core.rolling.TimeBasedRollingPolicy">
  <encoder class="ch.qos.logback.classic.encoder.PatternLayoutEncoder">

We made similar changes to the idp-process as well, and did not have to update Tomcat's logging.

Hope this helps others.

Edit 1: Tomcat Logging

Turns out, after a while, the X-Forwarded-For IP address stopped appearing in Shib's IdP logs. We ended up adding the RemoteIpValve in tomcat and restarting. Looks like it is needed after all:

  <Valve className="org.apache.catalina.valves.RemoteIpValve"
   trustedProxies="--IPs here--"
   protocolHeaderHttpsValue="https" />
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I'm not sure %X{req.xForwardedFor} is needed. When you use the Tomcat RemoteIpValve, it will set request.remoteAddr to the value of the X-Forwarded-For header, then it unsets the X-Forwarded-For header. So in logging.xml you would use %mdc{clientIP} (which shouldn't be needed because %msg includes the client IP). For more info:… (scroll down to the samples) – bmaupin Sep 23 at 17:44
@bmaupin thanks for weighing in. It has been a while since we got this working, but I faintly recall the only (or the first perhaps?) combination to log the actual IP was MDC filter + Tomcat valve + X-Forwarded-For. I don't recall any combination of clientIP working. The app has since moved to another platform, still this might be worth a second look. – KM. Sep 24 at 13:57
Ah, yes if you're using the MDC filter that might change things. On my end all I needed was 1. X-Forwarded-For in the load balancer 2. RemoteIpValve in the Tomcat server.xml, then the client IP showed up fine in the Shibboleth logs. – bmaupin Sep 24 at 14:06

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