List_object Not Working For Cross-account With Aws Lambda

I'm trying to download a file from S3 path in another account using AWS Lambda & python. I'm able to download the files if I provide full key to the copy_object. This will not

Solution 1:

Probably the issue is due to KMS. If the lambda and bucket are in different accounts, lambda will not have automatically access to kms key in the second account. You have to modify KMS key policy to allow for that. So try adding lambda role arn to the KMS policy in the second account.