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BRD

Feature BRD: Unauthorized Access Handling
Document Version: 1.0
Author: Senior Business Analyst
Date: 2025-09-10
Status: Draft for Review

1. Introduction

1.1. Feature Overview

This document specifies the business requirements for a standardized, system-wide Unauthorized Access Handling procedure. This is a non-functional, security-centric feature that defines the precise, consistent response the system must take whenever a user attempts to perform an action or access a resource for which they do not possess the required permissions. This framework underpins the entire security model, as defined in ADR-0004 and the Access Control Model Foundation BRD, ensuring that access denial is as predictable and secure as access approval.

1.2. Business Objectives

  • Provide Clear and Safe User Feedback: To inform users that an action has been blocked due to permissions, without revealing sensitive system information that could be exploited.
  • Enforce a Secure Default State: To ensure that the default outcome of any failed security check is a safe, non-permissive state that protects system data and functionality.
  • Create a Consistent User Experience: To guarantee that a user encounters the same predictable and professional response to access denial, regardless of what page or feature they are interacting with.

1.3. Scope

In Scope Out of Scope
Defining the standard system behavior for a failed permission check. The user authentication (login/logout) process itself.
The design and content requirements for a dedicated "Access Denied" page. A workflow for users to "Request Access" to a feature. (This would be a separate feature).
The required server response for unauthorized API calls (e.g., HTTP 403). Logging or auditing of failed access attempts. (This would be part of a separate Security Auditing feature).
The principle of "graceful degradation" where UI elements are hidden/disabled based on permissions. Specific email or in-app notifications to administrators about unauthorized attempts.

2. Business Requirements & Rules

2.1. Triggering Condition

  • Rule 2.1.1 (Universal Trigger): The Unauthorized Access Handling procedure MUST be invoked whenever and wherever the system performs a permission check as defined in the "Access Control Model Foundation" BRD (Rule 3.1.1), and that check fails because the required permission is absent from the user's effective permission set.

2.2. System Response Logic

  • Rule 2.2.1 (Halt and Deny): Upon a failed permission check, the system MUST immediately and completely halt the attempted action. No part of the restricted action should be partially executed.
  • Rule 2.2.2 (Response by Context): The system's response MUST be context-aware:
    • Page-Level Access: If a user attempts to navigate directly to a URL for which they lack the required viewing permission, the system MUST redirect them to the standard "Access Denied" page.
    • API-Level Access: If a user's browser makes a background API call (e.g., a POST, PUT, DELETE request) for an action they are not permitted to perform, the server MUST reject the request with an HTTP 403 Forbidden status code.
  • Rule 2.2.3 (UI Graceful Degradation): As a preventative measure, the user interface SHOULD proactively hide or disable interactive elements (buttons, links, form fields) that correspond to actions the user does not have permission to perform. This prevents the user from attempting the action in the first place. This rule is a "SHOULD" as the back-end enforcement (Rule 2.2.2) is the primary security control.

2.3. "Access Denied" Page Requirements

  • Rule 2.3.1 (Clear Messaging): The page MUST display a clear, concise, and non-technical message to the user.
    • Example Header: "Access Denied"
    • Example Body Text: "Sorry, you do not have the necessary permissions to view this page. Please contact your administrator if you believe this is an error."
  • Rule 2.3.2 (No Technical Details): To prevent security information leakage, the page MUST NOT reveal any technical details about the failed check, including the specific permission string that was missing.
  • Rule 2.3.3 (Clear Navigation Path): The page MUST provide the user with at least one clear, actionable navigation link to exit the error state, such as a "Return to Dashboard" or "Go to Homepage" button.

3. User Scenarios

3.1. Scenario 1: User Attempts to Access a Restricted Page via URL

  • Persona: Bob, a sales analyst.
  • Action: A colleague sends Bob a direct link to the "Admin: User Creation" page. Bob is logged in and clicks the link.
  • Expected System Behavior:
    1. The system receives the request for the user creation page.
    2. It checks Bob's effective permissions and does not find the required user:create permission.
    3. The Unauthorized Access Handling procedure is triggered.
    4. Instead of rendering the user creation form, the system redirects Bob's browser to the standard "Access Denied" page.

3.2. Scenario 2: User Interacts with a Disabled UI Element

  • Persona: Carol, a marketing manager who can edit users (user:edit) but not create them (user:create).
  • Action: On the User Listing page, Carol sees the "Edit" button next to users, but the "Create New User" button is visibly disabled (greyed out). She uses her browser's developer tools to manually enable the button and clicks it.
  • Expected System Behavior:
    1. The front-end, despite the manual override, sends an API request to the server to initiate the user creation process.
    2. The back-end server receives the request and, before processing it, performs its own authoritative permission check on Carol's account.
    3. The check for user:create fails.
    4. The server halts the action and returns an HTTP 403 Forbidden response to the browser.
    5. The UI receives the 403 error and displays a user-friendly, non-disruptive error message (e.g., a temporary "toast" notification) stating "Action failed: Insufficient permissions." The user remains on the User Listing page.

3.3. Scenario 3: Standard User Experience for a Permitted User

  • Persona: David, a System Administrator.
  • Action: David navigates to the User Listing page.
  • Expected System Behavior:
    1. The system checks David's permissions and finds user:create, user:edit, etc.
    2. The page loads normally.
    3. The "Create New User" button and all "Edit" buttons are visible