An error occurred (InvalidLambdaResponseException) when calling the InitiateAuth operation: Unrecognizable lambda output

Question

Am new to aws development and was trying to do password less features using aws cognito's Custom Auth Flow, lambda triggers and the aws python SDK.

My problem is after the call to InitiateAuth, I always get the error below: An error occurred (InvalidLambdaResponseException) when calling the InitiateAuth operation: Unrecognizable lambda output

Full traceback is: Traceback (most recent call last): File "test_custom_auth.py", line 52, in <module> ClientId=client_id File "/Users/jules/Repositories/snaaap/onemac-api/env/lib/python3.6/site-packages/botocore/client.py", line 320, in _api_call return self._make_api_call(operation_name, kwargs) File "/Users/jules/Repositories/snaaap/onemac-api/env/lib/python3.6/site-packages/botocore/client.py", line 623, in _make_api_call raise error_class(parsed_response, operation_name) botocore.errorfactory.InvalidLambdaResponseException: An error occurred (InvalidLambdaResponseException) when calling the InitiateAuth operation: Unrecognizable lambda output

I can see thru cloudwatch logs that the defineAuthChallenge Trigger and createAuthChallenge Trigger calls are successful and was even able to print out logs to verify this.

I did the lambda functions first with Javascript, then with Python, just to try another method.

I tried to return the following in python (I am editing using the lambda editor console)

• return event
• result = { "isBase64Encoded": False, "statusCode": 200, "headers": {}, "body": json.dumps(event) } return result

I tried to return the following in javascript (I am editing using the lambda editor console)

• context.succeed(event)
• callback(null, event)
• context.done(event)
• context.done(JSON.stringify(event))

And permutations of those mentioned above, but I still kept on getting the error :( Appreciate anyone that can help!

EDIT

Performed another request:

Below are the logs from defineAuthChallenge: START RequestId: 14441740-cc65-11e8-a632-9508cbba464c Version: $LATEST END RequestId: 14441740-cc65-11e8-a632-9508cbba464c REPORT RequestId: 14441740-cc65-11e8-a632-9508cbba464c Duration: 6.70 ms Billed Duration: 100 ms Memory Size: 128 MB Max Memory Used: 20 MB

Below are the logs from **createAuthChallenge **: START RequestId: 144995b6-cc65-11e8-8d2d-5388c84ccf95 Version: $LATEST END RequestId: 144995b6-cc65-11e8-8d2d-5388c84ccf95 REPORT RequestId: 144995b6-cc65-11e8-8d2d-5388c84ccf95 Duration: 592.59 ms Billed Duration: 600 ms Memory Size: 128 MB Max Memory Used: 29 MB

Answer 1

Changed challengeMetaData to challengeMetadata in the response I am returning from my createAuthChallenge function. Learned that when you put an invalid key in the response attribute lambda will throw the InvalidLambdaResponseException, though I hope next time cloudwatch can catch it.

Got an idea from @thomasmichaelwallace, and this article https://forums.aws.amazon.com/thread.jspa?threadID=237677.