Access Control Knowledge Base

Quick reference for access control models, authorization patterns, and PHP implementations.

Access Control Models Comparison

Model	Full Name	Basis	Granularity	Scalability	Complexity
ACL	Access Control List	Per-resource permissions	Fine	Poor at scale	Low
RBAC	Role-Based Access Control	Roles assigned to users	Medium	Good	Medium
ABAC	Attribute-Based Access Control	Policies over attributes	Very fine	Excellent	High
ReBAC	Relationship-Based Access Control	Object relationships	Very fine	Excellent	High

Decision Matrix: When to Use Which Model

Scenario	Recommended	Why
Simple app, few resources	ACL	Direct, easy to implement
Enterprise, department-based access	RBAC	Maps to organizational roles
Complex policies, dynamic rules	ABAC	Flexible attribute evaluation
Social graphs, shared resources	ReBAC	Natural relationship modeling
Multi-tenant SaaS	RBAC + tenant scope	Roles per tenant
Healthcare, finance (compliance)	ABAC	Fine-grained audit trail
Document sharing (Google Docs style)	ReBAC	Owner/editor/viewer relations
Microservices with JWT	RBAC (claims)	Stateless, token-based

RBAC: Role-Based Access Control

Role Hierarchy

┌─────────────────────────────────────────────────────────────────────────────┐
│                         RBAC ROLE HIERARCHY                                  │
├─────────────────────────────────────────────────────────────────────────────┤
│                                                                              │
│                        ┌──────────────┐                                      │
│                        │  SUPER_ADMIN │                                      │
│                        │  (all perms) │                                      │
│                        └──────┬───────┘                                      │
│                               │ inherits                                     │
│                        ┌──────▼───────┐                                      │
│                        │    ADMIN     │                                      │
│                        │  (manage)   │                                      │
│                        └──────┬───────┘                                      │
│                    ┌──────────┼──────────┐                                   │
│                    │ inherits │          │ inherits                           │
│             ┌──────▼───────┐  │  ┌───────▼──────┐                            │
│             │   MANAGER   │  │  │   EDITOR     │                            │
│             │ (approve)   │  │  │ (create/edit)│                            │
│             └──────┬───────┘  │  └───────┬──────┘                            │
│                    │          │          │                                    │
│                    └──────────┼──────────┘                                    │
│                        ┌──────▼───────┐                                      │
│                        │    USER      │                                      │
│                        │  (read)     │                                      │
│                        └──────┬───────┘                                      │
│                        ┌──────▼───────┐                                      │
│                        │    GUEST     │                                      │
│                        │  (limited)  │                                      │
│                        └──────────────┘                                      │
│                                                                              │
└─────────────────────────────────────────────────────────────────────────────┘

Permission Inheritance

Role	Own Permissions	Inherited From	Total Permissions
GUEST	view_public	-	1
USER	view, create	GUEST	3
EDITOR	edit, publish	USER	5
MANAGER	approve, assign	USER	5
ADMIN	manage_users, configure	MANAGER, EDITOR	10
SUPER_ADMIN	all	ADMIN	all

RBAC PHP Implementation

<?php

declare(strict_types=1);

namespace Domain\Authorization;

final readonly class Role
{
    /**
     * @param list<Permission> $permissions
     * @param list<self> $parents
     */
    public function __construct(
        private string $name,
        private array $permissions = [],
        private array $parents = [],
    ) {}

    public function hasPermission(Permission $permission): bool
    {
        if (in_array($permission, $this->permissions, true)) {
            return true;
        }

        foreach ($this->parents as $parent) {
            if ($parent->hasPermission($permission)) {
                return true;
            }
        }

        return false;
    }

    public function getName(): string
    {
        return $this->name;
    }

    /** @return list<Permission> */
    public function getAllPermissions(): array
    {
        $permissions = $this->permissions;

        foreach ($this->parents as $parent) {
            $permissions = array_merge($permissions, $parent->getAllPermissions());
        }

        return array_values(array_unique($permissions));
    }
}

ABAC: Attribute-Based Access Control

Core Concepts

Concept	Description	Example
Subject	Who is requesting access	User with attributes (role, department, clearance)
Resource	What is being accessed	Document with attributes (classification, owner)
Action	Operation being performed	read, write, delete, approve
Environment	Contextual conditions	Time of day, IP range, MFA status

Policy Evaluation

┌─────────────────────────────────────────────────────────────────────────────┐
│                        ABAC POLICY EVALUATION                                │
├─────────────────────────────────────────────────────────────────────────────┤
│                                                                              │
│   Request(subject, resource, action, environment)                            │
│       │                                                                      │
│       ▼                                                                      │
│   ┌──────────────────────┐                                                   │
│   │  Policy Decision     │                                                   │
│   │  Point (PDP)         │ ◀── Policy Store (rules)                         │
│   └──────────┬───────────┘                                                   │
│              │                                                               │
│       ┌──────┼──────┐                                                        │
│       ▼      ▼      ▼                                                        │
│   Policy1  Policy2  PolicyN                                                  │
│    ALLOW    DENY    ALLOW                                                    │
│       │      │      │                                                        │
│       └──────┼──────┘                                                        │
│              ▼                                                               │
│   ┌──────────────────┐                                                       │
│   │ Combining Algo   │                                                       │
│   │ (deny-overrides) │                                                       │
│   └────────┬─────────┘                                                       │
│            ▼                                                                 │
│         DENY                                                                 │
│                                                                              │
└─────────────────────────────────────────────────────────────────────────────┘

ABAC Policy Implementation

<?php

declare(strict_types=1);

namespace Domain\Authorization;

final readonly class AbacPolicy
{
    public function __construct(
        private string $name,
        private string $description,
        /** @var list<callable(AuthorizationContext): ?bool> */
        private array $rules,
    ) {}

    public function evaluate(AuthorizationContext $context): ?bool
    {
        foreach ($this->rules as $rule) {
            $result = $rule($context);
            if ($result === false) {
                return false;
            }
        }

        return true;
    }

    public function getName(): string
    {
        return $this->name;
    }
}

final readonly class AuthorizationContext
{
    public function __construct(
        private array $subjectAttributes,
        private array $resourceAttributes,
        private string $action,
        private array $environmentAttributes = [],
    ) {}

    public function getSubjectAttribute(string $key): mixed
    {
        return $this->subjectAttributes[$key] ?? null;
    }

    public function getResourceAttribute(string $key): mixed
    {
        return $this->resourceAttributes[$key] ?? null;
    }

    public function getAction(): string
    {
        return $this->action;
    }

    public function getEnvironmentAttribute(string $key): mixed
    {
        return $this->environmentAttributes[$key] ?? null;
    }
}

ReBAC: Relationship-Based Access Control

Google Zanzibar Model

Relationships are stored as tuples: user:relation:object

Tuple	Meaning
user:123#viewer@document:456	User 123 is a viewer of document 456
group:eng#member@user:123	User 123 is a member of group eng
document:456#parent@folder:789	Document 456 is in folder 789
folder:789#viewer@group:eng#member	Members of eng group are viewers of folder 789

Relationship Graph

┌─────────────────────────────────────────────────────────────────────────────┐
│                    ReBAC RELATIONSHIP GRAPH                                   │
├─────────────────────────────────────────────────────────────────────────────┤
│                                                                              │
│   user:alice ──owner──▶ document:report                                     │
│       │                     │                                                │
│       │ member              │ parent                                         │
│       ▼                     ▼                                                │
│   group:engineering    folder:shared                                        │
│       │                     │                                                │
│       │ viewer              │ viewer                                         │
│       ▼                     ▼                                                │
│   folder:eng-docs      org:acme (all members can view)                     │
│                                                                              │
│   Check: Can alice view document:report?                                    │
│   Path:  alice ──owner──▶ document:report  ✓ (owner implies viewer)         │
│                                                                              │
│   Check: Can bob view folder:shared?                                        │
│   Path:  bob ──member──▶ org:acme ──viewer──▶ folder:shared  ✓             │
│                                                                              │
└─────────────────────────────────────────────────────────────────────────────┘

Multi-Tenancy Authorization

Pattern	Description	Isolation Level
Tenant-scoped roles	User has different roles per tenant	Strong
Shared roles, tenant filter	Global roles, data filtered by tenant	Medium
Tenant in JWT claims	Tenant ID in authentication token	Medium
Row-level security	Database enforces tenant isolation	Strong
Separate schemas	Each tenant has own DB schema	Strongest

Tenant-Scoped Authorization

<?php

declare(strict_types=1);

namespace Domain\Authorization;

final readonly class TenantPermissionChecker
{
    public function __construct(
        private TenantRoleRepositoryInterface $roleRepository,
    ) {}

    public function hasPermission(string $userId, string $tenantId, Permission $permission): bool
    {
        $roles = $this->roleRepository->findRolesForUserInTenant($userId, $tenantId);

        foreach ($roles as $role) {
            if ($role->hasPermission($permission)) {
                return true;
            }
        }

        return false;
    }

    public function assertPermission(string $userId, string $tenantId, Permission $permission): void
    {
        if (!$this->hasPermission($userId, $tenantId, $permission)) {
            throw new AccessDeniedException(
                sprintf('User %s lacks %s in tenant %s', $userId, $permission->value, $tenantId),
            );
        }
    }
}

Symfony Voter Implementation

<?php

declare(strict_types=1);

namespace Infrastructure\Security\Voter;

use Symfony\Component\Security\Core\Authentication\Token\TokenInterface;
use Symfony\Component\Security\Core\Authorization\Voter\Voter;

final class DocumentVoter extends Voter
{
    public const string VIEW = 'DOCUMENT_VIEW';
    public const string EDIT = 'DOCUMENT_EDIT';
    public const string DELETE = 'DOCUMENT_DELETE';

    protected function supports(string $attribute, mixed $subject): bool
    {
        return in_array($attribute, [self::VIEW, self::EDIT, self::DELETE], true)
            && $subject instanceof Document;
    }

    protected function voteOnAttribute(string $attribute, mixed $subject, TokenInterface $token): bool
    {
        $user = $token->getUser();
        if (!$user instanceof User) {
            return false;
        }

        /** @var Document $document */
        $document = $subject;

        return match ($attribute) {
            self::VIEW => $this->canView($document, $user),
            self::EDIT => $this->canEdit($document, $user),
            self::DELETE => $this->canDelete($document, $user),
            default => false,
        };
    }

    private function canView(Document $document, User $user): bool
    {
        if ($document->isPublic()) {
            return true;
        }

        return $document->getOwnerId() === $user->getId()
            || $user->hasRole('ROLE_ADMIN');
    }

    private function canEdit(Document $document, User $user): bool
    {
        return $document->getOwnerId() === $user->getId()
            || $user->hasRole('ROLE_EDITOR');
    }

    private function canDelete(Document $document, User $user): bool
    {
        return $document->getOwnerId() === $user->getId()
            || $user->hasRole('ROLE_ADMIN');
    }
}

Laravel Gate/Policy

<?php

declare(strict_types=1);

namespace App\Policies;

use App\Models\Document;
use App\Models\User;

final class DocumentPolicy
{
    public function view(User $user, Document $document): bool
    {
        if ($document->is_public) {
            return true;
        }

        return $user->id === $document->owner_id
            || $user->hasRole('admin');
    }

    public function update(User $user, Document $document): bool
    {
        return $user->id === $document->owner_id
            || $user->hasRole('editor');
    }

    public function delete(User $user, Document $document): bool
    {
        return $user->id === $document->owner_id
            || $user->hasRole('admin');
    }
}

Anti-Patterns

Anti-Pattern	Problem	Solution
Inline role checks	if ($user->role === 'admin') scattered in code	Use Voter/Policy abstraction
Hardcoded permissions	Permissions compiled into code	Store in database/config
Missing deny-by-default	Forgetting to deny when no rule matches	Default to DENY
Role explosion	Too many roles (one per use case)	Switch to ABAC or group permissions
Checking in views only	No server-side enforcement	Always check in backend
No audit logging	Cannot trace who accessed what	Log every authorization decision
Caching without invalidation	Stale permission grants	Event-driven cache invalidation
God role	Single admin role with all permissions	Granular admin sub-roles

Common Violations Quick Reference

Violation	Where to Look	Severity
No authorization on API endpoints	Controllers, routes	Critical
Hardcoded role names in business logic	Domain layer, services	Warning
Missing tenant isolation in queries	Repositories, query builders	Critical
No CSRF protection on state-changing forms	Form handlers, middleware	Critical
Permissions not cached	Voter/Policy implementations	Warning
No audit trail for access decisions	Authorization layer	Warning
Overly permissive default roles	Role configuration	Warning

Detection Patterns

# Authorization implementations
Grep: "Voter|VoterInterface|AbstractVoter" --glob "**/*.php"
Grep: "Gate::define|Gate::allows|Gate::denies|@can" --glob "**/*.php"
Grep: "Policy|AuthorizesRequests" --glob "**/*.php"

# Role checks
Grep: "hasRole|isGranted|->can\(|->cannot\(" --glob "**/*.php"
Grep: "ROLE_|Permission::|PermissionEnum" --glob "**/*.php"

# Inline role checks (anti-pattern)
Grep: "role\s*===?\s*['\"]admin|role\s*===?\s*['\"]user" --glob "**/*.php"

# Tenant isolation
Grep: "tenant_id|tenantId|getTenantId" --glob "**/*.php"
Grep: "TenantScope|MultiTenant|BelongsToTenant" --glob "**/*.php"

# Casbin
Grep: "Enforcer|casbin|model\.conf|policy\.csv" --glob "**/*.php"

# Security configuration
Grep: "security\.yaml|security\.php|access_control" --glob "**/*.{yaml,php}"
Grep: "#\[IsGranted|@IsGranted|@Security" --glob "**/*.php"

# Missing authorization
Grep: "class.*Controller" --glob "**/*.php"
Grep: "class.*Action" --glob "**/Action/**/*.php"

References

For detailed information, load these reference files:

• references/models.md — Detailed ACL, RBAC, ABAC, ReBAC analysis with scalability comparisons and PHP examples
• references/php-implementations.md — Symfony Voters, Laravel Gates/Policies, Casbin PHP, permission caching strategies