真实鉴权Real authentication

先说问题The problem

先动手Do it first

先在页面上接线——页面只懂规则。然后跑下面那条判题，那才是真会失败的东西。Wire it on the page — the bench only knows the rules. Then run the check below; that is the part that can actually fail.

create_app(…)

为什么这样设计Why it is built this way

用到的 APIAPIs in play

代码The code

# create_app takes ASGI middlewares; the identity layer is one of them
app = create_app(..., extra_middlewares=[Middleware(TrustedIdentityMiddleware)])

class TrustedIdentityMiddleware:                 # plain ASGI: (app, scope, receive, send)
    async def __call__(self, scope, receive, send):
        verified = TOKENS.get(_bearer(scope))     # 401 when the token is missing or unknown
        if verified is None:
            return await _reject(send, 401, ...)
        scope["headers"] = [...("x-user-id", verified)]   # overwrite the client's claim
        await self.app(scope, receive, send)

# now the header a client typed is discarded; deps.get_current_user_id reads what you wrote
assert client_b.get(f"/sessions/{session_of_a}/messages").status_code == 404
assert (await policy.can_edit("auditor", ResourceKind.AGENT, "owner-b", "agent-1", None)) is False

判题The check

python lab.py run c8

它断言了什么What it asserts

• X-User-Id alone, no token: read -> 200 with 1 victim row(s), PATCH -> 200; an unshared id gets 0
• the framework says so itself: Return the caller's user ID from the ``X-User-ID`` request header.
• tokenless X-User-Id -> 401, rejected claim recorded as 'owner-b'
• valid token for owner-a + header claiming owner-b -> the header is discarded, the victim's session route reads back 404 where the owner gets 200
• policy wired: auditor reads owner-b's agent with editable=False, PATCH -> 403 for the auditor and 200 for the owner
• the share list is per-owner: owner-a sees 0 agent(s), not owner-b's

会踩的坑Where it hurts

• 把服务直接部署到公网「先内部用用」。X-User-ID 可伪造 + 沙箱能执行命令，等于把远程代码执行挂在了一个不需要密码的端口上。

  Deploying the service publicly because it is 'internal for now'. A forgeable X-User-ID plus a sandbox that executes commands is remote code execution on a passwordless port.

费曼闸门Say it back