Tools for configuring AWS credentials in MQTT Mutual Auth Demo (#370)

This adds aws_config_offline, which allows the user to download demo_config.h for the MQTT Mutual Auth Demo using a webpage.
This also adds aws_config_quick_start, which provides a means to generate demo_config.h for the Mutual Auth Demo with boto3.

tools/aws_config_quick_start/misc.py

@@ -0,0 +1,99 @@
+#!/usr/bin/env python
+
+import os
+import boto3
+
+
+def describe_endpoint():
+    client = boto3.client('iot')
+    endpoint = client.describe_endpoint(endpointType='iot:Data-ATS')
+    return endpoint['endpointAddress']
+
+
+def get_account_id():
+    client = boto3.client('sts')
+    aws_account_id = client.get_caller_identity()['Account']
+    return aws_account_id.strip('\n')
+
+
+def get_aws_region():
+    my_session = boto3.session.Session()
+    aws_region = my_session.region_name
+    return aws_region.strip('\n')
+
+
+def create_policy_document():
+    this_file_directory = os.getcwd()
+    policy_document = os.path.join(this_file_directory,
+                                   'policy_document.templ')
+    region_name = str(get_aws_region())
+    aws_account_id = str(get_account_id())
+    with open(policy_document) as policy_document_file:
+        policy_document_text = policy_document_file.read()
+
+    # Replace Account ID and AWS Region
+    policy_document_text = policy_document_text.replace('<aws-region>',
+                                                        region_name)
+    policy_document_text = policy_document_text.replace('<aws-account-id>',
+                                                        aws_account_id)
+
+    return policy_document_text
+
+
+def format_credential_keys_text(credential_text):
+    credential_text_lines = credential_text.split('\n')
+    formatted_credential_text_lines = []
+
+    for credential_text_line in credential_text_lines:
+        if credential_text_line.strip():
+            formatted_credential_text_line = '    {:68s}'\
+                .format('"' + credential_text_line + '\\n"')
+            formatted_credential_text_lines.append(
+                formatted_credential_text_line)
+
+    formatted_credential_text = ' \\\n'.join(formatted_credential_text_lines)
+    return formatted_credential_text
+
+
+def write_client_credentials(
+        source_dir,
+        thing_name='',
+        client_certificate_pem='',
+        client_private_key_pem='',
+        cleanup=False):
+
+    file_to_modify = os.path.join(source_dir,
+                                  'FreeRTOS-Plus',
+                                  'Demo',
+                                  'coreMQTT_Windows_Simulator',
+                                  'MQTT_Mutual_Auth',
+                                  'demo_config.h')
+    file_text = ''
+
+    if cleanup:
+        filename = "demo_config_empty.templ"
+        with open(filename, 'r') as template_file:
+            file_text = template_file.read()
+
+    else:
+        endpoint = describe_endpoint()
+        client_certificate_pem =\
+            format_credential_keys_text(client_certificate_pem)
+        client_private_key_pem =\
+            format_credential_keys_text(client_private_key_pem)
+
+        filename = "demo_config.templ"
+        with open(filename, 'r') as template_file:
+            file_text = template_file.read()
+            file_text = file_text.replace("<IOTEndpoint>",
+                                          "\"" + endpoint + "\"")
+            file_text = file_text.replace("<IOTThingName>",
+                                          "\"" + thing_name + "\"")
+            file_text = file_text.replace("<ClientCertificatePEM>",
+                                          client_certificate_pem)
+            file_text = file_text.replace("<ClientPrivateKeyPEM>",
+                                          client_private_key_pem)
+
+    header_file = open(str(file_to_modify), 'w')
+    header_file.write(file_text)
+    header_file.close()