The Definitive Guide to Casbin Authorization Control From Basics to Mastery

In today's complex application systems, access control remains a critical concern. This guide will help you understand Casbin's configuration system through practical examples of different access control models.

I. Casbin Core Concepts

1.1 Access Control Model Comparison

Model Type	Suitable Scale	Management Complexity	Flexibility	Performance	Typical Use Case
ACL	Small Projects	Low	Low	High	Personal Blog Systems
RBAC	Medium Projects	Medium	Medium	Medium	Enterprise Management
ABAC	Large Projects	High	High	Medium	Financial Applications
Domain RBAC	Multi-tenant	High	High	Medium	SaaS Platforms

1.2 Core Configuration Files

File	Purpose	Format	Required
model.conf	Define access control model	CONF	✅
policy.csv	Store permission rules	CSV	✅
rbac_model.conf	RBAC specific model	CONF	❌
custom_function.go	Custom matching functions	Go	❌

II. ACL Model Configuration

2.1 Basic Model Configuration

# acl_model.conf - Basic ACL model configuration
[request_definition]
r = sub, obj, act

[policy_definition]
p = sub, obj, act

[policy_effect]
e = some(where (p.eft == allow))

[matchers]
m = r.sub == p.sub && r.obj == p.obj && regexMatch(r.act, p.act)

2.2 ACL Policy Configuration Example

# acl_policy.csv - Permission rules configuration
# Format: p, subject, object, action
p, alice, /data1, GET
p, alice, /data1, POST
p, bob, /data2, GET
p, bob, /data2, POST

2.3 ACL Permission Decision Matrix

User	Resource Path	Request Method	Allowed	Reason
alice	/data1	GET	✅	Explicitly allowed
alice	/data2	GET	❌	No permission
bob	/data2	GET	✅	Explicitly allowed
bob	/data1	POST	❌	No permission

III. RBAC Model Configuration

3.1 RBAC Model Configuration

# rbac_model.conf - RBAC model configuration
[request_definition]
r = sub, obj, act

[policy_definition]
p = sub, obj, act

[role_definition]
g = _, _

[policy_effect]
e = some(where (p.eft == allow))

[matchers]
m = g(r.sub, p.sub) && keyMatch(r.obj, p.obj) && regexMatch(r.act, p.act)

3.2 RBAC Policy Configuration

# rbac_policy.csv - Role permission configuration
# Role definitions
p, admin, /*, GET|POST|PUT|DELETE
p, developer, /projects/*, GET|POST
p, viewer, /projects/*, GET

# User role mappings
g, alice, admin
g, bob, developer
g, charlie, viewer

3.3 RBAC Role Permission Matrix

Role	Resource Scope	GET	POST	PUT	DELETE
admin	/*	✅	✅	✅	✅
developer	/projects/*	✅	✅	❌	❌
viewer	/projects/*	✅	❌	❌	❌

IV. ABAC Model Configuration

4.1 ABAC Model Configuration

# abac_model.conf - ABAC model configuration
[request_definition]
r = sub, obj, act, dept

[policy_definition]
p = sub, obj, act, dept

[policy_effect]
e = some(where (p.eft == allow))

[matchers]
m = r.dept == p.dept && keyMatch(r.obj, p.obj) && regexMatch(r.act, p.act)

4.2 ABAC Policy Configuration

# abac_policy.csv - Attribute-based permission rules
# Format: p, role, resource, action, department
p, employee, /reports, GET|POST, sales
p, manager, /reports, GET|POST|DELETE, sales
p, employee, /reports, GET|POST, engineering
p, manager, /reports, GET|POST|DELETE, engineering

4.3 ABAC Permission Evaluation Matrix

User Role	Department	Report Action	Allowed	Condition
employee	sales	GET report	✅	Department match
manager	sales	DELETE report	✅	Role permission
employee	marketing	GET report	❌	Department mismatch

V. Domain RBAC Configuration

5.1 Domain RBAC Model Configuration

# domain_rbac_model.conf
[request_definition]
r = sub, dom, obj, act

[policy_definition]
p = sub, dom, obj, act

[role_definition]
g = _, _, _

[policy_effect]
e = some(where (p.eft == allow))

[matchers]
m = g(r.sub, p.sub, r.dom) && keyMatch(r.obj, p.obj) && regexMatch(r.act, p.act)

5.2 Domain RBAC Policy Configuration

# domain_rbac_policy.csv
# Tenant A permissions
p, admin, tenantA, /data/*, GET|POST|PUT|DELETE
p, user, tenantA, /data/*, GET|POST

# Tenant B permissions
p, admin, tenantB, /data/*, GET|POST|PUT|DELETE
p, user, tenantB, /data/*, GET

# User role mappings
g, alice, admin, tenantA
g, bob, user, tenantA
g, charlie, admin, tenantB

5.3 Multi-tenant Permission Matrix

Tenant	User	Role	Resource Scope	GET	POST	PUT	DELETE
tenantA	alice	admin	/data/*	✅	✅	✅	✅
tenantA	bob	user	/data/*	✅	✅	❌	❌
tenantB	charlie	admin	/data/*	✅	✅	✅	✅

VI. Performance Optimization

6.1 Cache Configuration Parameters

Parameter	Description	Default	Recommended
enableCache	Enable caching	No	✅
cacheCapacity	Cache capacity	10000	Based on memory
cacheTTL	Cache TTL	24h	Based on needs

6.2 Optimization Impact Comparison

Optimization	Before QPS	After QPS	Improvement	Memory Impact
Enable cache	5000	15000	200%	+50MB
Batch policy loading	2000	8000	300%	+20MB
Async policy update	3000	9000	200%	+10MB

VII. Common Issues and Solutions

7.1 Configuration Troubleshooting Guide

Issue	Possible Cause	Solution	Prevention
Permission check failure	Model config error	Check matcher syntax	Unit testing
Performance degradation	Too many policies	Enable caching	Monitoring
Rule conflicts	Duplicate policies	Clean redundant rules	Rule auditing

7.2 Performance Tuning Recommendations

Optimization Area	Measures	Difficulty	Impact
Cache optimization	Adjust cache params	Low	Significant
Policy optimization	Merge similar rules	Medium	Moderate
Model optimization	Simplify matchers	High	Significant

VIII. Best Practices

8.1 Model Selection Guide

System Characteristic	Recommended Model	Reason	Considerations
Users < 100	ACL	Simple, direct	Maintenance cost
Users < 1000	RBAC	Role management	Role design
Complex business rules	ABAC	Flexible control	Performance impact
Multi-tenant architecture	Domain RBAC	Tenant isolation	Config complexity

8.2 Operations Management Recommendations

Operation	Frequency	Priority	Implementation
Config backup	Daily	High	Automated backup
Performance monitoring	Real-time	High	Alerts system
Rule auditing	Weekly	Medium	Manual review
Load testing	Monthly	Medium	Automated tests

References

Casbin Official Documentation
Enterprise Permission System Design
Microservice Security Architecture Practices

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