I knew already that Amazon had two ways of calling their services. The first was by consuming the WSDL metadata and calling through SOAP, and the second was through REST. Of course the REST would be too cumbersome by itself but not to fear – there is a SDK which makes that easier from common languages like Java and .NET. But the SOAP should be brain dead simple to consume right? Wrong. After searching the forums for a while I figured out that somebody had managed to get it working through WSE 2.0 but nobody had managed to get it working from WCF. I thought to myself – “Self, I can’t allowed this to happen”. Myself agreed.

OK the first thing was to get it to work any way I could. While I was searching the forums I came across this post which describes how to call AWS using SOAPSonar. So I downloaded my trial edition and gave it a whirl.Using SOAPSonar enterprise I was able to add a certificate that I had saved earlier called ‘brainhz-cert.cer’ and call the service. Excellent. So now all I needed was to do this same task in WCF.

The first step was figuring out how they were securing their service. After looking through their docs I found a couple of helpful snippets.

  1. AWS does not implement a full public key infrastructure. The certificate information is used only to authenticate requests to AWS. AWS uses X.509 certificates only as carriers for public keys and does not trust or use in any way any identity binding that might be included in an X.509 certificate. Pasted from here.
  2. Amazon does not store your private key.  Creating a new certificate/private key pair invalidates your old one.  This only affects your X.509 key used to authenticate AWS requests.  It does not affect the ssh keypairs you use to log into instances (linux) or retrieve their password (windows). Pasted from here.
  3. The WS-Security 1.0 specification requires you to sign the SOAP message with the private key associated with the X.509 certificate and include the X.509 certificate in the SOAP message header. Specifically, you must represent the X.509 certificate as a BinarySecurityToken as described in the WS-Security X.509 token profile (also available if you go to the OASIS-Open web site). Pasted from here.

From this I was able to deduce that they were using the WSS SOAP Message Security X.509 Certificate Token Profile 1.0

I guessed that I needed to use Message based security with the Certificate credential type, but I double checked myself on the MSDN website.

WSS SOAP Message Security X.509 Certificate Token Profile 1.0

<basicHttpBinding>
  <security mode="Message">
    <message credentialType="Certificate"/>
  </security>
</basicHttpBinding>

Pasted from here.

I needed to specify which certificate I was going to use. It looked like I already had one in my Personal store (sometimes called the My store).

<endpointBehaviors>
	<behavior name="cert">
		<clientCredentials>
			<clientCertificate storeLocation="CurrentUser" storeName="My"
				 x509FindType="FindByThumbprint"
				findValue="6b 6a e8 ad b6 61 9c 1d a2 75 21 e4 4a d7 15 53 11 e6 72 27"/>
		</clientCredentials>
	</behavior>
</endpointBehaviors>

After adding that the next error that I ran into was this:
“The service certificate is not provided for target ‘http://ec2.amazonaws.com/’. Specify a service certificate in ClientCredentials.”

OK, so I needed the serviceCertificate. I used FireFox and hit https://ec2.amazonaws.com/ and saved the certificate. Then I imported it into my trusted people store.
Then I went in and added the following in my endpoint behavior:

<serviceCertificate>
	<defaultCertificate storeLocation="CurrentUser" storeName="TrustedPeople"
		x509FindType="FindByThumbprint" findValue="29 ca cd 8f 43 2e ff 31 f2 7f e5 70 e9 2e 1a f3 9e 1b f8 e8"/>
	<authentication certificateValidationMode="PeerOrChainTrust" revocationMode="NoCheck"/>
</serviceCertificate>

I had high hopes, before running this time, but no. The next error was:
“Private key is not present in the X.509 certificate”. When I looked at the certificate in the store, sure enough I did not see the “You have a private key that corresponds to this certificate” at the bottom.
Weird that it worked for SOAPSonar, but whatever. I went to Amazon, created and downloaded another certificate, combined the two and put them in my personal store. I then had to switch the certificate thumbprint to the one starting with 72 46.

After doing all of that I received a very strange error.
“Value (xmlenc#) for parameter Version is invalid. Version not well formed. Must be in YYYY-MM-DD format.”
WTF? I had never seen this one before, and I didn’t really know what sort of black magic was going on beneath me. So I turned on message level tracing, did some searching, and ended up trying two things:

  1. Switching the algorithmSuite from Default (Basic256), to (Basic128).
  2. Switching the OperationContract ProtectionLevel to Sign only.

WARNING: this is a HACK do not do this.
I went into the generated code into Reference.cs and changed the attribute on DescribeImages.

        [OperationContract(Action="DescribeImages", ReplyAction="*", ProtectionLevel=ProtectionLevel.Sign)]

Now fervently praying, I ran again. Bad news and good news.
Bad news was it didn’t work, good news was it was a message size issue, which I have fixed so many times in the past. Because we were using Message security I couldn’t turn on streaming. So I had to just up the maximum.
maxBufferSize=”9999999″ maxReceivedMessageSize=”9999999″

After cranking up the number high enough I got
System.ServiceModel.Security.MessageSecurityException occurred
Message=Security processor was unable to find a security header in the message. This might be because the message was an unsecured fault or because there was a binding mismatch between the communicating parties. This can occur if the service is configured for security and the client is not using security.

This was starting to make me mad. I was saying things that are unfit for children’s ears to my computer. After tracing, I discovered that this was related to the fact that Amazon messages are only secured one way.
The responses, or this response anyway, seemed to be unsecured. After some searching I found a hotfix for this issue in WCF.

http://support.microsoft.com/kb/971493

However, it required a customBinding. ARRGH!

Now the next step was to figure out which of the properties needed to be set so that it matched what I was doing before.
I created a program that created the two bindings, and compared the binding elements using reflection. The outcome of that program was the following binding declaration:

<binding name="customWithUnsecuredResponse">
	<security authenticationMode="MutualCertificate"
		 allowSerializedSigningTokenOnReply="true"
		 defaultAlgorithmSuite="Basic128"
		 messageSecurityVersion="WSSecurity10..."
		 enableUnsecuredResponse="true"
		 securityHeaderLayout="Lax"
		 />
	<textMessageEncoding />
	<httpTransport maxBufferSize="9999999" maxReceivedMessageSize="9999999" />
</binding>

I particularly liked the message security version which has to be high on the list of longest names in all of .NET. It was so long that I had to use ellipses because it was screwing up the CSS layout. The full name is (one piece at a time):
WSSecurity10
WSTrustFebruary2005
WSSecureConversationFebruary2005
WSSecurityPolicy11
BasicSecurityProfile10

Wow – what a mouthful…
Also notice the enableUnsecuredResponse = true, which was the cause of the problem.

After running one more time…

I bet the suspense is killing you…


IT WORKED!!!

I spent the next several minutes whooping it up. After having done it, I can honestly say that may be the only person in the world that has been stupid enough to try and get this working :)

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