Fixes ansible#6454 verify ec2 key fingerprints

library/cloud/ec2_key

@@ -132,6 +132,10 @@ except ImportError:
     print "failed=True msg='boto required for this module'"
     sys.exit(1)
 
+import random
+import string
+
+
 def main():
     argument_spec = ec2_argument_spec()
     argument_spec.update(dict(
@@ -187,10 +191,45 @@ def main():
     # Ensure requested key is present
     elif state == 'present':
         if key:
-            '''existing key found'''
-            # Should check if the fingerprint is the same - but lack of info
-            # and different fingerprint provided (pub or private) depending if
-            # the key has been created of imported.
+            # existing key found
+            if key_material:
+                # EC2's fingerprints are non-trivial to generate, so push this key 
+                # to a temporary name and make ec2 calculate the fingerprint for us.
+                #
+                # http://blog.jbrowne.com/?p=23
+                # https://forums.aws.amazon.com/thread.jspa?messageID=352828
+
+                # find an unused name
+                test = 'empty'
+                while test:
+                    randomchars = [random.choice(string.ascii_letters + string.digits) for x in range(0,10)]
+                    tmpkeyname = "ansible-" + ''.join(randomchars)
+                    test = ec2.get_key_pair(tmpkeyname)
+
+                # create tmp key
+                tmpkey = ec2.import_key_pair(tmpkeyname, key_material)
+                # get tmp key fingerprint
+                tmpfingerprint = tmpkey.fingerprint
+                # delete tmp key
+                tmpkey.delete()
+
+                if key.fingerprint != tmpfingerprint:
+                    if not module.check_mode:
+                        key.delete()
+                        key = ec2.import_key_pair(name, key_material)    
+
+                        if wait:
+                            start = time.time()
+                            action_complete = False
+                            while (time.time() - start) < wait_timeout:
+                                if ec2.get_key_pair(name):
+                                    action_complete = True
+                                    break
+                                time.sleep(1)
+                            if not action_complete:
+                                module.fail_json(msg="timed out while waiting for the key to be re-created")
+
+                    changed = True
             pass
 
         # if the key doesn't exist, create it now