Understanding AWS Malformed Policy Error

The AWS Malformed Policy Error is a common issue encountered when working with policies in AWS Identity and Access Management (IAM). Policies determine who has what permissions to which resources and can be quite complex. A malformed policy indicates that there is a syntax, structural, or JSON formatting error, making it invalid. Let's delve into the specifics and understand how to tackle this issue effectively.

What is a Malformed Policy?

In the context of AWS IAM, a malformed policy refers to any policy document that does not comply with the required JSON syntax and AWS policy structure. This can include errors such as missing brackets, incorrect property names, or syntactical mistakes that prevent AWS from interpreting the policy correctly.

Causes of Malformation

1. Syntax Errors: Incorrect JSON syntax is the most frequent cause. This may involve missing commas, colons, or brackets.
2. Invalid JSON Structure: Even if the JSON syntax is correct, the structure may still be invalid for AWS policies.
3. Typographical Errors: Misspellings of reserved keywords such as Effect, Action, Resource, or Version.
4. Unsupported Elements: Inclusion of properties or elements not supported by AWS in policy documents.
5. Incorrect Data Types: Using the incorrect data type, such as a string instead of an array or object when required.

Example of an Invalid Policy

Consider the following malformed policy:

• There is a missing colon after "Effect" in the second statement, making this JSON invalid.
• Version: Specifies the language version of the policy. While not mandatory, including it is a best practice.
• Statement: Contains one or more permissions. Each statement is an object that can contain several properties:
  • Effect: Either Allow or Deny, specifying the permission outcome.
  • Action: Specifies the AWS service operations that are allowed or denied.
  • Resource: Specifies the AWS resources to which the actions apply.