Security Model

AWSim is a development emulator. This page states what it assumes, so you can tell whether your deployment matches those assumptions.

Trust Boundary

AWSim assumes a trusted local context and trusts its callers.

By default there is no authentication and no authorization: any client that can reach the port can call any API. That is the correct default for the primary use case, a developer running AWSim on their own machine or a CI job running it as a throwaway container.

It is not a suitable default for a shared host or a network anyone untrusted can reach.

Features That Make Outbound Requests

Several emulated services fetch URLs supplied by the caller. This is correct emulation of the AWS service, and it also means a caller can induce AWSim to make requests on their behalf:

Feature	What it fetches
API Gateway HTTP integrations	The integration URI configured on a route
Cognito federation	The identity provider's JWKS and discovery endpoints
Bedrock backend	The configured upstream model endpoint
RDS Data API, Lambda	Container images, when a container runtime is in use

On a trusted network this is the feature working. On an exposed instance it is a server-side request forgery primitive. Bear it in mind before exposing AWSim.

Hardening

Four gates are available, all off by default. They are independent and compose:

Setting	What it does
AWSIM_IAM_ENFORCE	Evaluates IAM policies on every request. Keys bound to an IAM user are enforced; unbound keys act as administrators so the first users can be created. See IAM enforcement
AWSIM_REQUIRE_SIGNED_REQUESTS	Rejects any request whose access key does not resolve to a known IAM user, with InvalidClientTokenId
AWSIM_VERIFY_SIGV4	Cryptographically verifies every SigV4 signature against the bound secret, rejecting forgeries with SignatureDoesNotMatch
AWSIM_REQUIRE_OPERATOR_AUTH	Gates the admin UI and admin endpoints behind a login. See operator auth

To restrict reachability instead, bind loopback:

awsim --bind 127.0.0.1

The default binds all interfaces, because publishing a container port requires it. When AWSim starts on a non-loopback address with no gate enabled, it logs a one-line notice saying so.

Container Posture

The published image runs as an unprivileged user (uid 65532), not root. If you mount a volume at /data that is owned by root, the process cannot write to it; either chown it to 65532:65532 or let Docker create the volume.

What Is Verified

The following were checked directly rather than assumed:

• SigV4 signature comparison and the operator bootstrap token comparison both use constant-time equality.
• Cognito stores passwords with bcrypt and signs tokens with RS256; no none algorithm path exists.
• DynamoDB's SQLite layer binds every caller-supplied value as a parameter and interpolates only static column lists, so it is not injectable.
• Archive extraction, and every path built from caller-supplied text, is contained by a shared helper that rejects traversal components.

What This Page Is Not

AWSim is not hardened for exposure to an untrusted network, and the gates above do not make it so. They make it usable in a semi-trusted setting such as a shared development host. Do not put it on the public internet.