title: Identity Server 3 Access Token Validation endpoint fails with Audience Validation Failed
body: <p>I have an IdentityServer3 instance set up and I am requesting a token using the authorize endpoint (/core/connect/authorize).</p>
  
  <p>My application requesting the token is an iOS application.</p>
  
  <p>I pass the following parameters; </p>
  
  <pre><code>client_id=&lt;clientid&gt;
  response_type=id_token
  scope=openid
  redirect_uri=&lt;redirecturi&gt;
  state=&lt;state&gt;
  nonce=&lt;nonce&gt;
  </code></pre>
  
  <p>This then opens up a web view for me, I enter my credentials and it returns the <code>redirect_uri</code> with the <code>#id_token</code> appended to the url.</p>
  
  <p>To validate the token I pass it to the access token validation endpoint (/core/connect/accesstokenvalidation) of my IdentityServer. I append <code>?token=&lt;access token received from login&gt;</code>.</p>
  
  <p>I then get the response </p>
  
  <pre><code>{ "Message": "invalid_token" }
  </code></pre>
  
  <p>When I check the log </p>
  
  <pre><code>System.IdentityModel.Tokens.SecurityTokenInvalidAudienceException: IDX10214: Audience validation failed. Audience: '&lt;clientid&gt;'. Did not match: validationParamters.ValidAudience: '&lt;identity_server_host&gt;/resources' or validationParameters.ValidAudiences: 'null'
  </code></pre>
  
  <p>What am I doing wrong here? Surely the IdentityServer that created the token should validate it as valid?</p>