Serverless function security
Secure function triggers, per-workload permissions, event validation, retries, and resource costs within the provider/customer responsibility boundary.
What it means
Serverless security protects event-driven code, its permissions, dependencies, triggers, and interactions with managed services. The provider manages infrastructure, but the customer still defines important application and identity controls. Short-lived execution does not mean short-lived credentials or harmless business effects.
A practical example
A function processes an incoming storage event with an identity restricted to the required objects. It validates event data, handles retries without duplicate effects, and avoids logging credentials or granting a shared broad role to every function.
What to check
Map triggers and trust boundaries, scope permissions per function, protect secrets, and bound resource consumption. Test duplicate and malformed events alongside dependency and deployment review.
A common pitfall
Assuming provider-managed infrastructure removes application security responsibilities leaves authorization and event validation unaddressed. A small function can still hold powerful permissions.
Think it through
Why test the same event more than once?
Answer: Event delivery may be retried, and the function must not turn duplicates into repeated sensitive business actions.
A small function can have broad authority
Imagine a fictional academy function processes uploaded homework. Its code is short, but its execution identity can read every storage object and update all learner records. The function's size says little about the effect of a compromise or logic mistake.
Give each workload the operations and resources it needs. Review credentials and access inherited through platform configuration, not only the permissions mentioned in source code.
The event is an input, not a trusted conclusion
An upload event describes something to process. The function must still validate the relevant object, expected origin, and business state before acting. A filename or user identifier supplied within an event should not override the service's own access model.
Events can be duplicated or arrive after other changes. Suppose the academy processes the same submission notification twice. The workflow should avoid creating inconsistent grades or repeated sensitive side effects. Durable processing state and idempotent operations help make retries understandable.
Managed infrastructure still has dependencies
The provider may maintain the execution platform while the customer owns code, dependencies, configuration, and identity policy. The precise split depends on the selected service. A platform upgrade cannot correct an application's overbroad permissions or unsafe data handling automatically.
Costs and availability also deserve controls. Bound execution time, concurrency, and input size according to the task, and monitor failures without logging secret values or unnecessary submission contents.
For a paper exercise, draw the upload store, event source, function, and results database. Mark the identity and required operations on every edge. Add a duplicate event, malformed input, and unavailable database, then define the expected safe behavior. The outcome should demonstrate both constrained authority and recoverable processing rather than relying on the short-lived nature of an individual invocation.
Related concepts
References & further reading
Original explanations, with primary references for deeper study.
OWASP: Serverless FaaS Security