Implement SafeVault security framework with input sanitization, BCrypt authentication, and RBAC

SECURITY_SUMMARY.md

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+# Security Summary - SafeVault Project
+
+## Overview
+This document outlines the security vulnerabilities that were identified during development and the fixes that were applied to the SafeVault application.
+
+## Activity 1: Secure Coding Practices
+
+### Vulnerability 1: Cross-Site Scripting (XSS)
+**Description:** User input could contain malicious JavaScript code that executes in the browser.
+
+**Example Attack:**
+```html
+<script>alert('XSS Attack')</script>
+<img src=x onerror="alert('XSS')">
+```
+
+**Fix Applied:**
+- Implemented `InputSanitizer.SanitizeForXss()` method
+- Encodes HTML special characters: `<`, `>`, `&`, `"`, `'`, `/`
+- All user inputs displayed in HTML context are sanitized
+- Applied in webform.html with proper validation
+
+**Location:** `SafeVault.App/Security/InputSanitizer.cs`
+
+### Vulnerability 2: SQL Injection
+**Description:** Unparameterized SQL queries could allow attackers to manipulate database queries.
+
+**Example Attack:**
+```sql
+Username: admin' OR '1'='1
+Password: anything' OR '1'='1
+```
+
+**Fix Applied:**
+- Implemented parameterized queries in `UserRepository`
+- All SQL queries use parameter binding via `DbCommand.Parameters`
+- Added `InputSanitizer.ContainsSqlInjectionPattern()` to detect injection attempts
+- Input validation prevents malicious patterns from reaching the database
+
+**Vulnerable Code (DO NOT USE):**
+```csharp
+// INSECURE - String concatenation
+string query = "SELECT * FROM Users WHERE Username = '" + username + "'";
+```
+
+**Secure Code (USED):**
+```csharp
+// SECURE - Parameterized query
+string query = "SELECT * FROM Users WHERE Username = @Username";
+command.Parameters.Add(new SqlParameter("@Username", username));
+```
+
+**Location:** `SafeVault.App/Data/UserRepository.cs`
+
+### Vulnerability 3: Weak Input Validation
+**Description:** Insufficient validation could allow malformed or malicious data.
+
+**Fix Applied:**
+- Email validation using regex pattern
+- Username validation (alphanumeric + underscore, 3-20 characters)
+- SQL injection pattern detection
+- Password strength requirements enforced
+
+**Location:** `SafeVault.App/Security/InputSanitizer.cs`
+
+## Activity 2: Authentication & Authorization
+
+### Vulnerability 4: Plain Text Passwords
+**Description:** Storing passwords in plain text or using weak hashing exposes user credentials.
+
+**Fix Applied:**
+- Implemented BCrypt password hashing with work factor
+- Uses `AuthService.HashPassword()` for password hashing
+- Uses `AuthService.VerifyPassword()` for secure password verification
+- BCrypt automatically handles salting and multiple rounds of hashing
+
+**Vulnerable Code (DO NOT USE):**
+```csharp
+// INSECURE - Plain text or simple hash
+user.Password = password; // Plain text
+user.PasswordHash = ComputeSHA256(password); // Weak hash without salt
+```
+
+**Secure Code (USED):**
+```csharp
+// SECURE - BCrypt with automatic salting
+user.PasswordHash = AuthService.HashPassword(password);
+bool isValid = AuthService.VerifyPassword(password, user.PasswordHash);
+```
+
+**Location:** `SafeVault.App/Security/AuthService.cs`
+
+### Vulnerability 5: Missing Authorization Checks
+**Description:** Users could access resources or perform actions without proper authorization.
+
+**Fix Applied:**
+- Implemented role-based authorization with `RoleAuthorization`
+- Admin and User roles defined
+- `RequireAdmin()` and `RequireRole()` methods enforce authorization
+- `CanAccessResource()` checks resource ownership
+- Throws `UnauthorizedAccessException` for unauthorized access attempts
+
+**Location:** `SafeVault.App/Security/RoleAuthorization.cs`
+
+### Vulnerability 6: Weak Password Requirements
+**Description:** Weak passwords could be easily guessed or brute-forced.
+
+**Fix Applied:**
+- Password must be at least 8 characters
+- Must contain uppercase letter
+- Must contain lowercase letter
+- Must contain digit
+- Must contain special character
+- Validated by `AuthService.IsStrongPassword()`
+
+**Location:** `SafeVault.App/Security/AuthService.cs`
+
+## Activity 3: Security Testing & Regression Prevention
+
+### Security Testing Implementation
+To prevent regression of security vulnerabilities, comprehensive tests were implemented:
+
+1. **TestInputValidation.cs**
+   - Tests XSS sanitization
+   - Tests SQL injection detection
+   - Tests email validation
+   - Tests username validation
+
+2. **TestAuthentication.cs**
+   - Tests password hashing
+   - Tests password verification
+   - Tests login with valid/invalid credentials
+   - Tests password strength requirements
+
+3. **TestAuthorization.cs**
+   - Tests role checking (admin/user)
+   - Tests resource access control
+   - Tests authorization exceptions
+   - Tests privilege escalation prevention
+
+4. **TestSecurityRegression.cs**
+   - Tests for previously vulnerable patterns
+   - Tests parameterized query usage
+   - Tests input sanitization consistency
+   - Ensures security fixes remain effective
+
+**Location:** `Tests/` folder
+
+## Security Best Practices Applied
+
+### 1. Defense in Depth
+- Multiple layers of security: input validation, sanitization, parameterized queries
+- Client-side and server-side validation
+- Both preventive (parameterized queries) and detective (pattern matching) controls
+
+### 2. Principle of Least Privilege
+- Role-based access control limits user permissions
+- Users can only access their own resources
+- Admins have elevated privileges with explicit checks
+
+### 3. Secure by Default
+- Default role is "user" (not admin)
+- All queries use parameterized approach
+- Password hashing is mandatory
+- Input validation required before database operations
+
+### 4. Security Through Obscurity Avoided
+- Security mechanisms are well-documented
+- Relies on proven cryptographic methods (BCrypt)
+- Uses industry-standard security practices
+
+## Remaining Considerations
+
+### Production Deployment Recommendations
+1. **HTTPS:** Use TLS/SSL for all communications
+2. **CSRF Protection:** Implement anti-CSRF tokens for web forms
+3. **Rate Limiting:** Prevent brute-force attacks on login
+4. **Session Management:** Implement secure session handling
+5. **Logging:** Log authentication attempts and authorization failures
+6. **Database Security:** Use database-level access controls
+7. **Secrets Management:** Store connection strings securely (not in code)
+8. **Regular Updates:** Keep BCrypt.Net-Next and other dependencies updated
+
+### Potential Future Enhancements
+- Two-factor authentication (2FA)
+- Account lockout after failed login attempts
+- Password reset functionality with secure tokens
+- Audit logging for all security-relevant events
+- Content Security Policy (CSP) headers
+- Input sanitization for additional contexts (URLs, JSON, etc.)
+
+## Testing Verification
+All security tests pass successfully:
+- ✅ Input validation tests
+- ✅ Authentication tests
+- ✅ Authorization tests
+- ✅ Security regression tests
+
+## Conclusion
+The SafeVault application implements comprehensive security controls to protect against common vulnerabilities including XSS, SQL injection, weak authentication, and inadequate authorization. All identified vulnerabilities have been addressed with industry-standard security practices and are covered by automated tests to prevent regression.
+
+**Last Updated:** February 9, 2026
+**Version:** 1.0