#39 Handle SES payload invocations

lambda/app_handler/provider/request.py

@@ -16,6 +16,7 @@ def __init__(self, payload):
         self.payload = payload
         self.content = payload
         self.has_error = None
+        self.matched = False
         self.parse(payload)
 
     def parse(self, payload):
@@ -25,8 +26,13 @@ def parse(self, payload):
             - Invocation as a Python function
             - Invocation of Lambda function
             - Invocation behind an AWS HTTP v2 API Gateway
+            - Invocation by an SNS topic
         """
 
+        # Check if lambda was invoked as an SNS message
+        if self.is_sns_message(payload):
+            return
+
         if 'body' not in payload:
             logging.debug('Body not in payload, returning payload')
             return
@@ -62,39 +68,11 @@ def parse(self, payload):
         content_type = content_type.lower()
         logging.debug('Content-Type detected: %s', content_type)
 
-        matched = False
-
-        if content_type.startswith('application/x-www-form-urlencoded'):
-            logging.debug('Decoding URL encoded form')
-            try:
-                html_decoded = urllib.parse.unquote(self.content)
-                # Assume each value should only appear once, drop repeat keys
-                self.content = dict(urllib.parse.parse_qsl(html_decoded))
-                logging.debug(self.content)
-                matched = True
-            except(
-                AttributeError,
-                ValueError
-            ) as exception:
-                logging.critical('Error decoding URL encoded form')
-                logging.critical(exception)
-                self.has_error = True
+        self.is_form_url_encoded(content_type=content_type)
 
-        if content_type.startswith('application/json'):
-            logging.debug('Loading JSON string')
-            try:
-                self.content = json.loads(self.content, strict=False)
-                logging.debug(self.content)
-                matched = True
-            except (
-                JSONDecodeError,
-                TypeError
-            ) as exception:
-                logging.critical('Error loading string as JSON')
-                logging.critical(exception)
-                self.has_error = True
+        self.is_application_json(content_type=content_type)
 
-        if not matched:
+        if not self.matched:
             logging.critical('Error determining how to load content type.')
             self.has_error = True
 
@@ -119,3 +97,58 @@ def get_remote_ip(self):
         logging.debug('Fetched remote IP from payload: %s', remote_ip)
 
         return remote_ip
+
+
+    def is_sns_message(self, payload):
+        """
+        Determine if payload is an SNS message
+        """
+        # Handle first SNS message
+        if 'Records' in payload and isinstance(payload['Records'], list):
+            record = payload['Records'][0]
+            if 'Sns' in record and 'Message' in record['Sns'] and 'Subject' in record['Sns']:
+                logging.debug('SNS payload extracted')
+                self.content = record['Sns']
+                return True
+
+        return False
+
+
+    def is_application_json(self, content_type: str):
+        """
+        Determine of payload is JSON
+        """
+        if content_type.startswith('application/json'):
+            logging.debug('Loading JSON string')
+            try:
+                self.content = json.loads(self.content, strict=False)
+                logging.debug(self.content)
+                self.matched = True
+            except (
+                JSONDecodeError,
+                TypeError
+            ) as exception:
+                logging.critical('Error loading string as JSON')
+                logging.critical(exception)
+                self.has_error = True
+
+
+    def is_form_url_encoded(self, content_type: str):
+        """
+        Determine if payload is form URL encoded
+        """
+        if content_type.startswith('application/x-www-form-urlencoded'):
+            logging.debug('Decoding URL encoded form')
+            try:
+                html_decoded = urllib.parse.unquote(self.content)
+                # Assume each value should only appear once, drop repeat keys
+                self.content = dict(urllib.parse.parse_qsl(html_decoded))
+                logging.debug(self.content)
+                self.matched = True
+            except(
+                AttributeError,
+                ValueError
+            ) as exception:
+                logging.critical('Error decoding URL encoded form')
+                logging.critical(exception)
+                self.has_error = True

lambda/tests/unit/fixtures/sns_message_v1.json

@@ -0,0 +1,31 @@
+{
+  "Records": [
+    {
+      "EventVersion": "1.0",
+      "EventSubscriptionArn": "arn:aws:sns:us-east-1:123456789012:sns-lambda:21be56ed-a058-49f5-8c98-aedd2564c486",
+      "EventSource": "aws:sns",
+      "Sns": {
+        "SignatureVersion": "1",
+        "Timestamp": "2019-01-02T12:45:07.000Z",
+        "Signature": "tcc6faL2yUC6dgZdmrwh1Y4cGa/ebXEkAi6RibDsvpi+tE/1+82j...65r==",
+        "SigningCertURL": "https://sns.us-east-1.amazonaws.com/SimpleNotificationService-ac565b8b1a6c5d002d285f9598aa1d9b.pem",
+        "MessageId": "95df01b4-ee98-5cb9-9903-4c221d41eb5e",
+        "Message": "Hello from SNS!",
+        "MessageAttributes": {
+          "Test": {
+            "Type": "String",
+            "Value": "TestString"
+          },
+          "TestBinary": {
+            "Type": "Binary",
+            "Value": "TestBinary"
+          }
+        },
+        "Type": "Notification",
+        "UnsubscribeURL": "https://sns.us-east-1.amazonaws.com/?Action=Unsubscribe&SubscriptionArn=arn:aws:sns:us-east-1:123456789012:test-lambda:21be56ed-a058-49f5-8c98-aedd2564c486",
+        "TopicArn":"arn:aws:sns:us-east-1:123456789012:sns-lambda",
+        "Subject": "TestInvoke"
+      }
+    }
+  ]
+}

lambda/tests/unit/provider/test_request.py

@@ -146,3 +146,14 @@ def test_get_remote_ip():
     eventv2 = get_json_fixture_file('httpapiv2_gateway_request_urlencoded_base64.json')
     assert RequestProvider(eventv1).get_remote_ip() == '127.0.0.1'
     assert RequestProvider(eventv2).get_remote_ip() == '127.0.0.1'
+
+# SNS topic
+
+def test_payload_parse_sns_message():
+    """
+    Ensure that an SNS message is correctly parsed
+    """
+
+    sns_request = get_json_fixture_file('sns_message_v1.json')
+    assert RequestProvider(sns_request).content['Message'] == 'Hello from SNS!'
+    assert RequestProvider(sns_request).content['Subject'] == 'TestInvoke'