title: Sending AWS EC2 RestAPI using Postman returns error
body: <p>I am trying to send a EC2 RestAPI (DescribeInstances) using Postman application. I created a user in IAM in AWS. I generated a AccessKeyId and SecretKey for that particular user, and gave the user "AmazonEC2FullAccess" policy (all EC2 access).
  I used the following steps in Postman to send the ResAPI:</p>
  
  <ul>
  <li>"Get" operation, set End Point to <a href="https://ec2.amazonaws.com/?Action=DescribeInstances" rel="nofollow noreferrer">https://ec2.amazonaws.com/?Action=DescribeInstances</a></li>
  <li><p>In the "Authorization" Tab, selected "AWS Signature" and set the following fields:</p>
  
  <ul>
  <li>AccessKey = ACCESSKEYEXAMPLE</li>
  <li>SecretKey = SECRETKEYEXAMPLE</li>
  <li>AWS Region = us-west-1</li>
  <li>Service Name = ec2</li>
  </ul></li>
  <li><p>Click on "Update Request", which ends up generating 3 Headers.  I used the info from the generated Headers to modify the endpoint as follows:</p></li>
  </ul>
  
  <p><a href="https://ec2.amazonaws.com/?Action=DescribeInstances&amp;Version=2016-11-15&amp;X-Amz-Algorithm=AWS4-HMAC-SHA256&amp;X-Amz-Credential=ACCESSKEYEXAMPLE/20170913/us-west-1/ec2/aws4_request&amp;X-Amz-Date=20170913T013055Z&amp;X-Amz-SignedHeaders=content-type&amp;X-Amz-Signature=amzsignaturesamplegenerated" rel="nofollow noreferrer">https://ec2.amazonaws.com/?Action=DescribeInstances&amp;Version=2016-11-15&amp;X-Amz-Algorithm=AWS4-HMAC-SHA256&amp;X-Amz-Credential=ACCESSKEYEXAMPLE/20170913/us-west-1/ec2/aws4_request&amp;X-Amz-Date=20170913T013055Z&amp;X-Amz-SignedHeaders=content-type&amp;X-Amz-Signature=amzsignaturesamplegenerated</a></p>
  
  <ul>
  <li>"Content-Type" header is set to "application/x-www-form-urlencoded", and deleted X-Amz-Date and Authorization headers.</li>
  </ul>
  
  <p>When I sent the RestAPI by clicking on "Send", I get the following error response:
  Status : "401 Unauthorized"
  
  <Code>AuthFailure</Code>AWS was not able to validate the provided access credentials4bc49d04-2115-4b95-8af5-5ac879ac5df3</p>
  
  <p>The error seems to suggest a malformed RestAPI as opposed to an unauthorized access. Tried different variations, very confused. Any help would be highly appreciated.</p>
  
  <p>Thank you,
  Ahmed.</p>