In SAP API Management, an HTTP 401 status indicates "Unauthorized," meaning authentication failed. Let’s investigate why this might happen with a basic authentication policy:
Step 1: Basic Authentication Policy- This policy verifies credentials (username/password) in the HTTP Authorization header. If valid, the request proceeds; otherwise, a 401 error is returned.
Step 2: Role of AssignMessage Policy- The AssignMessage policy in SAP API Management manipulates request/response messages. The AssignTo tag specifies the target (e.g., request, response).
Step 3: Analyze the Issue- A 401 error suggests the authentication policy didn’t receive correct credentials. If an AssignMessage policy precedes it and modifies the response prematurely:
A. type="response": Setting AssignTo type="response" means the policy generates a response message, bypassing further processing (including authentication). This could trigger a 401 if the authentication policy never executes.
B. type="record": "record" is not a valid AssignTo type in SAP API Management (valid types include request, response, etc.), so this is irrelevant.
C. type="read": "read" is also not a valid type, making it incorrect.
Step 4: Scenario- If AssignMessage with type="response" is placed before the authentication policy, it short-circuits the flow, preventing credential validation and causing a 401.
Step 5: Official Source- The SAP Help Portal’s "AssignMessage Policy" documentation states that type="response" creates a response message, potentially interrupting the request flow if misconfigured.
Conclusion: Option A is the verified reason for the 401 error.References:
SAP Help Portal: "AssignMessage Policy" (SAP API Management)
SAP Help Portal: "BasicAuthentication Policy"
