secrets-engine/tests/authorization_stub.py

"""In-process stand-ins for approval-engine and access-engine.

These exist so the whole GH-DEC-2026-003 chain can be exercised end to end
before either engine is deployed: claim -> check -> consume -> OpenBao. They are
test doubles for *transport and sequencing*, not for the contracts -- the wire
shapes are pinned independently against flex-auth's real replay fixtures in
tests/test_decision_replay.py, which is what stops these stubs from quietly
defining a contract of their own.
"""
from __future__ import annotations

import json
import threading
from datetime import datetime, timedelta, timezone
from http.server import BaseHTTPRequestHandler, HTTPServer

from secrets_engine.approval_claim import binding_from_check_request
from secrets_engine.authorization import request_digest


def _now():
    return datetime.now(timezone.utc)


def _stamp(moment):
    return moment.strftime("%Y-%m-%dT%H:%M:%SZ")


class AuthorizationStub:
    """Serves the claim, check and consume endpoints on a loopback port."""

    def __init__(self, *, approval_id, package, version, policy_digest="sha256:" + "1" * 64):
        self.approval_id = approval_id
        self.package = package
        self.version = version
        self.policy_digest = policy_digest
        self.calls: list[str] = []
        self.consumed = False
        #: set to force a specific failure for negative tests
        self.claim_valid_now = True
        self.claim_reason_code = "ok"
        self.include_pdp_digest = True
        self.effect = "allow"
        self.consume_status = 200
        self._pdp_digest = ""
        self._server = None
        self._thread = None

    # -- lifecycle ----------------------------------------------------------
    def start(self):
        stub = self

        class Handler(BaseHTTPRequestHandler):
            def log_message(self, *_args):
                pass

            def _send(self, status, payload):
                body = json.dumps(payload).encode()
                self.send_response(status)
                self.send_header("Content-Type", "application/json")
                self.send_header("Content-Length", str(len(body)))
                self.end_headers()
                self.wfile.write(body)

            def do_GET(self):
                if self.path == f"/v1/approvals/{stub.approval_id}/claim":
                    stub.calls.append("claim")
                    return self._send(200, stub.claim())
                return self._send(404, {"error": "not found"})

            def do_POST(self):
                length = int(self.headers.get("Content-Length") or 0)
                raw = self.rfile.read(length) if length else b"{}"
                if self.path == "/v1/check":
                    stub.calls.append("check")
                    return self._send(200, stub.decision(json.loads(raw)))
                if self.path == f"/v1/approvals/{stub.approval_id}/consume":
                    stub.calls.append("consume")
                    if stub.consume_status != 200:
                        return self._send(stub.consume_status, {"error": "conflict"})
                    stub.consumed = True
                    return self._send(200, {
                        "status": "consumed",
                        "request_digest": json.loads(raw).get("request_digest"),
                        "consumed_at": _stamp(_now()),
                    })
                return self._send(404, {"error": "not found"})

        self._server = HTTPServer(("127.0.0.1", 0), Handler)
        self._thread = threading.Thread(target=self._server.serve_forever, daemon=True)
        self._thread.start()
        return self

    def stop(self):
        if self._server is not None:
            self._server.shutdown()
            self._server.server_close()

    @property
    def url(self):
        return f"http://127.0.0.1:{self._server.server_address[1]}"

    # -- payloads -----------------------------------------------------------
    def bind_request(self, request):
        """Record the request the engine will propose, so the claim can name it."""
        self._pdp_digest = request_digest(request)
        self._binding = binding_from_check_request(request)
        return self._pdp_digest

    def claim(self):
        now = _now()
        binding = {
            # approval-engine's own vocabulary, deliberately unlike ours
            "action": f"secrets.kv.{self._binding['action']}",
            "actor": self._binding["actor"],
            "principal": self._binding["principal"],
            "purpose": self._binding["purpose"],
            "target": {"id": "lane-under-test", "stage": "prod"},
            "digest": "sha256:" + "3" * 64,
        }
        if self.include_pdp_digest:
            binding["pdp_digest"] = self._pdp_digest
        return {
            "schema_version": "0.1",
            "kind": "approval-claim",
            "issuer": "approval-engine",
            "approval_id": self.approval_id,
            "state": "valid" if self.claim_valid_now else "revoked",
            "valid_now": self.claim_valid_now,
            "consumed": False,
            "binding": binding,
            "freshness": {
                "observed_at": _stamp(now),
                "ttl_seconds": 30,
                "not_after": _stamp(now + timedelta(seconds=30)),
            },
            "validity": {
                "not_before": _stamp(now - timedelta(hours=1)),
                "expires_at": _stamp(now + timedelta(hours=1)),
            },
            "reason_code": self.claim_reason_code,
        }

    def decision(self, request):
        now = _now()
        binding = {k: request[k] for k in ("tenant", "subject", "action", "resource")
                   if request.get(k) is not None}
        if request.get("context") is not None:
            binding["context"] = request["context"]
        binding["request_digest"] = request_digest(request)
        return {
            "id": "decision:stub-" + request["action"],
            "contract_version": "flex-auth.decision-record.v1",
            "request_id": request.get("id"),
            "effect": self.effect,
            "subject": request["subject"],
            "resource": request["resource"],
            "binding": binding,
            "lifetime": {
                "kind": "ttl",
                "ttl": "15m",
                "not_before": _stamp(now - timedelta(minutes=1)),
                "expires_at": _stamp(now + timedelta(minutes=15)),
            },
            "provenance": {
                "evaluator": "stub/local",
                "mode": "standalone",
                "policy_package": self.package,
                "policy_version": self.version,
                "policy_package_digest": self.policy_digest,
                "decision_time": _stamp(now),
            },
        }