ARR reverse proxy outbound rewrite rule for redirections

arriis-7.5reverse-proxyrewrite

I'm currently trying to put together a proof of concept on mixing various technologies onto one web site in order to ease migrations and add flexibility.
The idea is to create one 'mashup' site behind an IIS 7.5 ARR reverse proxy.

For the time being the ARR reverse proxy forwards all request to our main site.
The request are as follow:

 client -> ARR: Get /
 ARR -> Server 1: Get /
 Server 1 -> ARR: 200: /index.htm
 ARR -> client: 200: /index.htm

…so far so good.

Let's say, I want to add a new site (root of another server) as a subsite of my main website.
a simple inbound rule does the trick:

<rule name="sub1" stopProcessing="true">
  <match url="^mySubsite(.*)" />
  <conditions logicalGrouping="MatchAll" trackAllCaptures="false" />
  <action type="Rewrite" url="http://server2/{R:1}" />
</rule>

The requests now are:

 client -> ARR: Get /mySubsite
 ARR -> Server 2: Get /
 Server 2 -> ARR: 200: /index.htm
 ARR -> client: 200: /index.htm

… still ok.

The issue comes when the site on server2 sends a redirection (e.g. to a login page). In the case of SharePoint, it will redirect the user to: /_layouts/Authenticate.aspx?Source=%2F
…which does not exists:

client -> ARR: Get /mySubsite
ARR -> Server 2: Get /
Server 2 -> ARR: 301: /_layouts/Authenticate.aspx?Source=%2F
ARR -> client: 301: /_layouts/Authenticate.aspx?Source=%2F
client -> ARR: Get /_layouts/Authenticate.aspx?Source=%2F
ARR -> client: 404: Not Found

Does anyone know a way write the outbound rule to rewrite the response from server 2 "301: /_layouts/Authenticate.aspx?Source=%2F" to "301: /mySubsite/_layouts/Authenticate.aspx?Source=%2FmySubsite%2F"?

Best Answer

I solved this by using subdomains. So instead of:

www.mydomain.com/mysite1
www.mydomain.com/mysite2

I'm using:

mysite1.mydomain.com
mysite2.mydomain.com

This means that all relative links and redirects still work as they did before.

If there really is a need to rewrite the location header, see this walkthrough

Related Solutions

IIS 7.5 and ARR 2 Reverse Proxy

Is 'localhost' on the same server? i.e. is Tomcat on port 9443 while ARR is on port 80, on the same server?

Here are the key things to setup:

create a Server Farm. If it's on the same box, add a single node pointing to 'localhost'.
if you say 'yes' to create the URL Rewrite rules, it will capture all traffic and forward to that server farm. If that's fine, then say yes.
if you didn't create the URL Rewrite rule in the previous step, then go to the top level of IIS, go to URL Rewrite, and create a new rule. Use {HTTP_HOST} for the domain name, or {SERVER_ADDR} for the IP binding. Set the action to use the Server Farm you set up in the first step above.
the Default Web Site should catch all traffic, which in turn will be caught by the URL Rewrite rule at the global level.

Reverse Proxy – should virtual directory/subfolders match rewrite rules

There is an undocumented issue with ARR / rewrite, where it cannot map subfolders. I am adding this for my reference and hoping it helps others

A workaround I have tried that seems to be effective, is to create a folder inside your source web application, add a web.config inside that folder with the rules pointing to the destination web application:

<?xml version="1.0" encoding="UTF-8"?>
<configuration>
    <system.webServer>
        <rewrite>
            <rules>
                <rule name="ReverseProxyInboundRule1" stopProcessing="true">
                    <match url="(.*)" />
                    <action type="Rewrite" url="http://<<<TARGET_HOSTNAME>>>{R:1}" />
                    <serverVariables>
                        <set name="HTTP_X_ORIGINAL_ACCEPT_ENCODING" value="{HTTP_ACCEPT_ENCODING}" />
                        <set name="HTTP_ACCEPT_ENCODING" value="" />
                    </serverVariables>
                </rule>
            </rules>
            <outboundRules>
                <rule name="RestoreAcceptEncoding" preCondition="RestoreAcceptEncoding">
                    <match serverVariable="HTTP_ACCEPT_ENCODING" pattern="^(.*)$" />
                    <action type="Rewrite" value="{HTTP_X_ORIGINAL_ACCEPT_ENCODING}" />
                </rule>
                <preConditions>
                    <preCondition name="RestoreAcceptEncoding">
                        <add input="{HTTP_X_ORIGINAL_ACCEPT_ENCODING}" pattern=".*" />
                    </preCondition>
                </preConditions>
            </outboundRules>
        </rewrite>
    </system.webServer>
</configuration>

Also added instructions from https://blogs.msdn.microsoft.com/friis/2016/08/25/iis-with-url-rewrite-as-a-reverse-proxy-part-2-dealing-with-500-52-status-codes/ around GZIP

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