feat(webui): console authorization, RBAC, redaction, and audit model (Closes #633)

Phase 1 of the MCP Control Plane Web Console (#631) defines the model that
future gated writes must pass through, and enables none of them.

The read-only MVP (#426-#436) ships with no authentication; protection comes
from network placement alone (#435). That is adequate while every route is a
GET and inadequate the moment Phase 2 wires a write. This lands the authority
first, so no write can later be added without something to check it against.

webui/console_authz.py
  Identity sources (none / local-dev / access-proxy), a four-role matrix
  (viewer, operator, controller, admin), the privileged-action list, and a
  fail-closed authorize(). Every action maps to a task_key in
  task_capability_map, so the console cannot invent an authority the MCP layer
  does not already define. Roles are always server-side configuration, never a
  client assertion. Deny reasons are closed and enumerated; there is no
  implicit allow branch, and even an allow reports execution_enabled=false
  while ACTIVE_PHASE is 1.

webui/console_redaction.py
  One redaction pass for API payloads, rendered HTML, logs, and audit records.
  Reuses gitea_audit.redact as the shared authority rather than forking it,
  then adds console patterns for keychain references, credential assignments,
  PEM private-key blocks, and JWTs. Never raises: an unredactable value
  degrades to the placeholder rather than being emitted raw.

webui/console_audit.py
  Console-side audit records, which gitea_audit cannot supply: it records MCP
  mutations and carries no console actor, identity source, correlation id, or
  retention class, and an authorization denial is not a mutation at all. The
  two are additive and join on correlation.request_id. Records are redacted at
  build time, re-scanned at write time, and dropped rather than persisted if
  they still trip a detector. Retention is per-record; an unknown action is
  retained as privileged rather than standard.

webui/app.py
  Attaches an authorization block to the existing preview and attempt routes
  and records the decision. The terminal outcome is unchanged - gated_actions
  still fails closed for every action - so this cannot loosen anything. Adds
  GET /api/console/security-model publishing the three policies as JSON.

Probe authentication is deliberately declarative in this slice:
probe_auth_required() reports operator intent and no route consults it. The
documentation says so plainly and a regression test pins the not-enforced
status, so wiring it in Phase 2 is a deliberate change rather than a silent
one. An operator who sets the variable believing it protects a probe would be
worse off than one who knows it does not.

Tests: tests/test_webui_console_authz_audit.py - 75 passed, 93 subtests,
covering each acceptance criterion and each test the issue requires
(redaction units, default-deny for unauthenticated write stubs, audit record
creation for a simulated privileged preview).

Co-Authored-By: Claude Opus 4.8 (1M context) <[email protected]>

webui/app.py

@@ -2,6 +2,7 @@
 
 from __future__ import annotations
 
+import uuid
 from datetime import datetime, timezone
 
 from starlette.applications import Starlette
@@ -19,6 +20,9 @@ from final_report_validator import FINAL_REPORT_TASK_KINDS
 
 from webui.gated_actions import attempt_action, load_action_registry, preview_action
 from webui.gated_action_views import render_actions_page
+from webui import console_audit
+from webui.console_authz import authorize, rbac_matrix, resolve_principal
+from webui.console_redaction import redaction_policy
 from webui.audit_validator import audit_report, audit_to_dict
 from webui.audit_views import render_audit_page
 from webui.lease_loader import load_lease_snapshot, snapshot_to_dict as lease_snapshot_to_dict
@@ -215,6 +219,49 @@ async def api_actions(_request: Request) -> JSONResponse:
     return JSONResponse(load_action_registry().to_dict())
 
 
+def _request_id() -> str:
+    return f"req-{uuid.uuid4().hex}"
+
+
+def _audit_target(action_id: str, params: dict[str, object]) -> dict[str, object]:
+    """Describe the action target for the audit record (never secrets)."""
+    if "pr_number" in params:
+        return {"kind": "pr", "ref": f"#{params['pr_number']}"}
+    if "issue_number" in params:
+        return {"kind": "issue", "ref": f"#{params['issue_number']}"}
+    if "branch_name" in params:
+        return {"kind": "branch", "ref": str(params["branch_name"])}
+    return {"kind": "unspecified", "ref": action_id}
+
+
+def _authorize_request(
+    request: Request,
+    action_id: str,
+    params: dict[str, object],
+    *,
+    for_execution: bool,
+    result: str,
+) -> dict[str, object]:
+    """Resolve principal, decide, and audit. Returns the decision payload.
+
+    Phase 1 records the decision rather than enforcing it as the terminal
+    outcome: ``webui.gated_actions`` already fails closed for every action, so
+    this layer cannot loosen anything. Phase 2 enforces on this same decision.
+    """
+    principal = resolve_principal(headers=dict(request.headers))
+    decision = authorize(action_id, principal, for_execution=for_execution)
+    console_audit.record_event(
+        action_id=action_id,
+        result=result,
+        decision=decision,
+        principal=principal,
+        target=_audit_target(action_id, params),
+        request_id=_request_id(),
+        detail=decision.detail,
+    )
+    return decision.to_dict()
+
+
 async def api_action_preview(request: Request) -> JSONResponse:
     action_id = request.path_params["action_id"]
     params = dict(request.query_params)
@@ -224,6 +271,13 @@ async def api_action_preview(request: Request) -> JSONResponse:
     result = preview_action(action_id, **params)
     if "error" in result:
         return JSONResponse(result, status_code=404)
+    result["authorization"] = _authorize_request(
+        request,
+        action_id,
+        params,
+        for_execution=False,
+        result=console_audit.RESULT_PREVIEWED,
+    )
     return JSONResponse(result)
 
 
@@ -237,10 +291,31 @@ async def api_action_attempt(request: Request) -> JSONResponse:
     if not isinstance(body, dict):
         body = {}
     result = attempt_action(action_id, **body)
+    authorization = _authorize_request(
+        request,
+        action_id,
+        body,
+        for_execution=True,
+        result=(
+            console_audit.RESULT_DENIED
+            if not result.get("success")
+            else console_audit.RESULT_ALLOWED
+        ),
+    )
+    result["authorization"] = authorization
     status = 403 if not result.get("success") else 200
     return JSONResponse(result, status_code=status)
 
 
+async def api_console_security_model(_request: Request) -> JSONResponse:
+    """Read-only publication of the #633 authorization/redaction/audit model."""
+    return JSONResponse({
+        "rbac": rbac_matrix(),
+        "redaction": redaction_policy(),
+        "audit": console_audit.audit_policy(),
+    })
+
+
 async def method_not_allowed(request: Request, _exc: Exception) -> Response:
     path = request.url.path
     if path in _AUDIT_MUTATION_PATHS and request.method == "POST":
@@ -291,6 +366,11 @@ def create_app(*, bind_host: str | None = None) -> Starlette:
                 methods=["POST"],
             ),
             Route("/api/leases", api_leases, methods=["GET"]),
+            Route(
+                "/api/console/security-model",
+                api_console_security_model,
+                methods=["GET"],
+            ),
         ],
         exception_handlers={405: method_not_allowed},
     )