ARR 3.0 - Bug?

A few weeks back we found a bug in ARR 3.0, if it's not a bug then it's definitely an odd feature.

We have a couple of ARR servers and while configuring, troubleshooting, etc.. we kept one of the servers off. We turned it on and it started failing with the following errors getting logged in the event log.

Application Log

Source: Application Error

Event ID: 1000

Faulting application name: w3wp.exe, version: 8.0.9200.16384, time stamp: 0x50108835

Faulting module name: requestRouter.dll, version: 7.1.1952.0, time stamp: 0x5552511b

Exception code: 0xc0000005

Fault offset: 0x000000000000f2dd

Faulting process id: 0x8bc

Faulting application start time: 0x01d0b89d5edc49ba

Faulting application path: c:\windows\system32\inetsrv\w3wp.exe

Faulting module path: C:\Program Files\IIS\Application Request Routing\requestRouter.dll

Report Id: 9caa10cb-2490-11e5-943b-005056010c6a

Faulting package full name:

Faulting package-relative application ID:

System log

Source: WAS

Event ID: 5009

A process serving application pool 'stark.dev.com' terminated unexpectedly. The process id was '52'. The process exit code was '0xff'.

Source: WAS

Event ID: 5011

A process serving application pool 'stark.dev.com' suffered a fatal communication error with the Windows Process Activation Service. The process id was '2792'. The data field contains the error number.

Source: WAS

Event ID: 5002

Application pool 'stark.dev.com' is being automatically disabled due to a series of failures in the process(es) serving that application pool.

This last one was due to rapid fail being enabled in the app pool

The odd thing is that, Server 1 was working fine, but Server 2 wasn't. Odder still was that they were configured in the same way, at least it look that way, at first.

After a lot of troubleshooting, we found the issue in Server 2, which, surprise, surprise was not configured the same way as Server 1.

This is the offending rule:

Yes, it's a stupid rule, it clearly should've have been Match Any but then again ARR should not have taken the app pool down.

We talked with Microsoft support who said that they were going to talk to the product team but I've not heard anything, so who knows.

Using ARR (Reverse Proxy) with Microsoft Dynamics CRM 2015 - IFD

In this post I'll discuss how we have used the Application Request Routing module from IIS to expose Ms Dynamics CRM to the big bad world.

In this project I'm working on at the moment we want to allow authorized third parties to access to our application, which means that there has been a lot of discussions around what's the best way of doing this.

The Problem:

We want to allow third parties access to our MS Dynamics CRM 2015 system but these third parties might be mom and pop operations so federating with them is not an option. In reality, this is a fantasy conjured up by the PM, but we all go along with it, because sometimes it's important to know which battles to fight.

We also don't want to expose our MS Dynamics CRM 2015 servers to the big bad internet.

The Solution:

Use ARR to expose the MS Dynamics CRM 2015 website to the outside world, while keeping the servers happily inside the perimeter.

This is an architecture diagram of what we are trying to achieve.

I'm assuming that you have a working MS Dynamics CRM 2013/2015 installation configured for Internet Facing Deployment and a wildcard certificate for the appropriate domain available.

Install ARR.

Navigate to this page and click on install this extension, which will use the Windows Platform installer to install ARR, just follow the instructions therein. Alternatively you can do it manually, which I haven't tried.

Configure ARR

ARR is configured from the IIS Manager console.

So fire it up (windows key + r -> inetmgr)  and let's get started:

We first create a Server Farm for the MS Dynamics CRM Web Servers. If you have web and application CRM servers then you only need to add the web servers. We have full servers.

Ensure you add all servers, not just one server, unless you only have one server like myself in this environment :)

If you are only using ARR to expose MS Dynamics CRM to the outside world, then it's probably ok to click yes here.

 We can now configure our server farm.

We want to make sure that traffic is only directed to servers that are up and running so I normally set the organization's wsdl page as the health test URL. The server's page (using FQDN) should also work and in fact should be used if you have more than one organization.

The other thing that needs to be done is to set load balancing to be a based on Client affinity, in other words, a client will always hit the same server, unless that server is down. This is an optional step, that's only required, as far as I can tell, for reports.

We now need to check that the routing rule is correct for the current set up.

Pretty simple, as we're sending everything that hits this server onward to the MS Dynamics CRM Farm. However, the rule will, by default, forward it to http rather than https, so this needs to be changed.

The final step is to create the proxy websites. I'm going to assume that a wildcard certificate has been installed already for the server. These website will receive the traffic from the internet and forward it to the MS Dynamics CRM Web Servers.

When using IFD, a website is needed for each organization and another one for the auth website. You can also add one for the discovery service, but as far as my limited testing goes, it works without it.

At this point ARR is configured, now all that remains is to set up name resolution.

I normally use CNAME aliases for auth, disc and the various organizations to point to the ARR server:

stark.dev.local --> ARR Server (Organization)
auth.dev.local --> ARR Server  (auth)
disc.dev.local --> ARR Server   (discovery)

In my next post I will add ADFS to the reverse proxy, note that it's perfectly acceptable to use ARR for this purpose as well, but it also possible to use WAP, which provides pre-authentication.

MS Dynamics CRM - Blocking Direct Access to SharePoint

In this project I'm working on we've had a requirement to block direct access to SharePoint, in other words. Our users can only access their documents through CRM.

There are various ways, in which this can be achieved and today I will be discussing achieving this by leveraging ARR.

We have a similar architecture to this:

We have a Sharepoint site collection and every document is stored in this site collection, so our users would go https://sp.dev.local/sites/spsite/<crm_entity>/ to access documents for <crm_entity>

This is actually a somewhat irritating requirement because IE behaves differently than Firefox and Chrome. We're lucky enough not to have to support Opera and Safari as well, nothing wrong with these browsers, but 5 browsers would drive our testers crazy.

In any case, we've configured two farms, CRM and SHAREPOINT, so we need rules for those.

So for CRM we have:

<rule name="CRM Farm Forwarding Rule" enabled="true" patternSyntax="Wildcard" stopProcessing="false">
    <match url="*" />
    <conditions logicalGrouping="MatchAny" trackAllCaptures="true">
        <add input="{HTTP_HOST}" pattern="*crm.dev.local" />
    </conditions>
    <serverVariables>
    </serverVariables>
    <action type="Rewrite" url="https://CRM/{R:0}" />
</rule>

And for Sharepoint we have:

<rule name="Sharepoint Farm Forwarding Rule" enabled="true" patternSyntax="Wildcard" stopProcessing="true">
    <match url="*" />
    <conditions logicalGrouping="MatchAny" trackAllCaptures="true">
        <add input="{HTTP_HOST}" pattern="*sp.dev.local" />
    </conditions>
    <serverVariables>
    </serverVariables>
    <action type="Rewrite" url="https://SHAREPOINT/{R:0}" />
</rule>

So far so good, this is where things start to get interesting. We want to block direct access to SP for IE browsers, which we can achieve like this:

 
<rule name="IE - Allow Access to SharePoint grid in CRM" enabled="true" patternSyntax="Wildcard" stopProcessing="true">
    <match url="*sites/SPSITE/crmgrid*" />
    <conditions logicalGrouping="MatchAny" trackAllCaptures="false">
    </conditions>
    <serverVariables>
    </serverVariables>
    <action type="Rewrite" url="https://SHAREPOINT/{R:0}" />
</rule>    

and

<rule name="IE - Block Direct Access to SharePoint" stopProcessing="true">
    <match url="sites\/SPSITE" />
    <conditions logicalGrouping="MatchAll" trackAllCaptures="false">
        <add input="{HTTP_REFERER}" pattern="^/?$" negate="true" />
        <add input="{HTTP_USER_AGENT}" pattern="MSIE" />
    </conditions>
    <serverVariables>
    </serverVariables>
    <action type="CustomResponse" statusCode="403" subStatusCode="1" statusReason="IE" statusDescription="Direct Access to SHAREPOINT is not permitted" />
</rule>

The first rules allows traffic if it's trying to access SP through the List component, this allows the SharePoint CRM List component to work.

The second rule will block access for IE user agents ( i.e containing MSIE) and where the referer is not empty. It will stop processing if there is a match.

For some reason, I.E. blanks the referer when accessing documents in SharePoint from the list component but crucially fills it in if accessing documents directly from SharePoint.

Firefox and Chrome will have the correct referer, i.e. sp.dev.local/sites/spsite/crmgrid, so there is a single rule:

<rule name="Other Browsers - Block Direct Access to SharePoint" enabled="true" patternSyntax="Wildcard" stopProcessing="true">
    <match url="*sites/SPSITE*" />
    <conditions logicalGrouping="MatchAll" trackAllCaptures="false">
        <add input="{HTTP_REFERER}" pattern="*dev.local/sites/SPSITE/crmgrid*" negate="true" />
        <add input="{HTTP_USER_AGENT}" pattern="*MSIE*" negate="true" />
    </conditions>
    <serverVariables>
    </serverVariables>
    <action type="CustomResponse" statusCode="403" subStatusCode="2" statusReason="Other" statusDescription="Direct Access to SHAREPOINT is not permitted" />
</rule>

Just need to make sure that the user agent is not from IE. The rule will stop processing if there is a match.

Rules.xml can be found below, with the rules in the correct order.

Thus effectively we do the following:

CRM -> Rewrite to  CRM Farm
SP - crm grid?  -> Rewrite to SP Farm
SP - IE and empty Referer -> Rewrite to SP Farm
SP - Other Browser and correct Referer -> Rewrite to SP Farm
SP -> Rewrite to Farm

The last rule is only needed if there are other sites in SP that the users might need to access.

<?xml version="1.0" encoding="UTF-8"?>
<appcmd>
    <CONFIG CONFIG.SECTION="system.webServer/rewrite/globalRules" path="MACHINE/WEBROOT/APPHOST" overrideMode="Inherit" locked="false">
        <system.webServer-rewrite-globalRules>
            <rule name="CRM Farm Forwarding Rule" enabled="true" patternSyntax="Wildcard" stopProcessing="false">
                <match url="*" />
                <conditions logicalGrouping="MatchAny" trackAllCaptures="true">
                    <add input="{HTTP_HOST}" pattern="*crm.dev.local" />
                </conditions>
                <serverVariables>
                </serverVariables>
                <action type="Rewrite" url="https://CRM/{R:0}" />
            </rule>
            <rule name="IE - Allow Access to SharePoint grid in CRM" enabled="true" patternSyntax="Wildcard" stopProcessing="true">
                <match url="*sites/SPSITE/crmgrid*" />
                <conditions logicalGrouping="MatchAny" trackAllCaptures="false">
                </conditions>
                <serverVariables>
                </serverVariables>
                <action type="Rewrite" url="https://SHAREPOINT/{R:0}" />
            </rule>
            <rule name="IE - Block Direct Access to SharePoint" stopProcessing="true">
                <match url="sites\/SPSITE" />
                <conditions logicalGrouping="MatchAll" trackAllCaptures="false">
                    <add input="{HTTP_REFERER}" pattern="^/?$" negate="true" />
                    <add input="{HTTP_USER_AGENT}" pattern="MSIE" />
                </conditions>
                <serverVariables>
                </serverVariables>
                <action type="CustomResponse" statusCode="403" subStatusCode="1" statusReason="IE" statusDescription="Direct Access to SHAREPOINT is not permitted" />
            </rule>
            <rule name="Other Browsers - Block Direct Access to SharePoint" enabled="true" patternSyntax="Wildcard" stopProcessing="true">
                <match url="*sites/SPSITE*" />
                <conditions logicalGrouping="MatchAll" trackAllCaptures="false">
                    <add input="{HTTP_REFERER}" pattern="*dev.local/sites/SPSITE/crmgrid*" negate="true" />
                    <add input="{HTTP_USER_AGENT}" pattern="*MSIE*" negate="true" />
                </conditions>
                <serverVariables>
                </serverVariables>
                <action type="CustomResponse" statusCode="403" subStatusCode="2" statusReason="Other" statusDescription="Direct Access to SHAREPOINT is not permitted" />
            </rule>
            <rule name="Sharepoint Farm Forwarding Rule" enabled="true" patternSyntax="Wildcard" stopProcessing="true">
                <match url="*" />
                <conditions logicalGrouping="MatchAny" trackAllCaptures="true">
                    <add input="{HTTP_HOST}" pattern="*sp.dev.local" />
                </conditions>
                <serverVariables>
                </serverVariables>
                <action type="Rewrite" url="https://SHAREPOINT/{R:0}" />
            </rule>
        </system.webServer-rewrite-globalRules>
    </CONFIG>
</appcmd>

It can be exported with this command:

appcmd.exe list config -section:system.webServer/rewrite/globalRules -xml > rules.xml 

The imported with this command:

appcmd.exe set config /in < rules.xml

Removing HTTP Headers for an ARR/MS Dynamics CRM/Sharepoint 2013 system

We had a pen test carried out last week and one of the outcomes was that we were leaking information with our HTTP headers and they must be removed.

Our environment consists of a web layer (IIS using ARR) and then an app layer (MS Dynamics CRM and MS SharePoint)

Personally I think this is a bit of security through obscurity but needs must so here we go:

X-AspNet-Version Header:

MS Dynamics CRM 2013

In the web.config, <drive>:Program Files\Microsoft Dynamics CRM\CRMWeb  add enableVersionHeader="false" to the httpRuntime element, normally you'll end up with something like this:

<httpRuntime executionTimeout="300" maxRequestLength="32768" requestValidationMode="3.0" encoderType="Microsoft.Crm.CrmHttpEncoder, Microsoft.Crm" enableVersionHeader="false"/>

MS SharePoint 2013

In the web.config,  <drive>:inetpub\wwwroot\wss\VirtualDirectories\80\ add enableVersionHeader="false" to the httpRuntime element, normally you'll end up with something like this:

<httpRuntime maxRequestLength="51200" requestValidationMode="2.0" enableVersionHeader="False" />

X-Powered-By Header:

From IIS Manager -> Server -> HTTP Response Headers

Server Header:

The simplest way I found is to use URL Rewrite to blank this header, which works very well for our system as we're using ARR already so just need to do this one on the web layer ... from IIS Manager -> Url Rewrite -> Add Rule

Select Blank Outbound Rule

Fill in the details as below

Don't forget to click Apply when you've finished.

It's worth pointing out  that this will simply blank out the value of the Server Header, rather than remove it completely.

If you want to remove it completely you will need to install urlscan.

This approach can be used for all the other headers above I suppose.

X-Powered-By: ARR/2.5 Header

From a powershell console with elevated permissions go to C:\Windows\system32\inetsrv and run this command:

.\appcmd.exe set config -section:webFarms /"[name='serverfarmname'].applicationRequestRouting.protocol.arrResponseHeader:false" /commit:apphost