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0. 背景

Casbin是用于Golang项目的功能强大且高效的开源访问控制库。
强大通用也意味着概念和配置较多，具体到实际应用(以Gin Web框架开发）需要解决以下问题：

• 权限配置的存储，以及增删改查
• Gin框架的中间件如何实现

经过一番摸索实践出经验，计划分为三个章节，循序渐进的介绍使用方法

1. Casbin概念介绍以及库使用
2. 使用Gorm存储Casbin权限配置以及增删改查
3. 实现Gin鉴权中间件

1. 准备工作

接上一章，略改进一下，将model.conf文件内容存储到go字符串中,最终代码如下:

package mainimport ("log""github.com/casbin/casbin/v2""github.com/casbin/casbin/v2/model"gormadapter "github.com/casbin/gorm-adapter/v3""github.com/glebarez/sqlite""gorm.io/gorm"
)func main() {db, err := gorm.Open(sqlite.Open("test.db"), &gorm.Config{})if err != nil {panic("failed to connect database")}a, err := gormadapter.NewAdapterByDB(db)if err != nil {panic("new gorm adapter error: " + err.Error())}m, err := model.NewModelFromString(`[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) && keyMatch2(r.obj,p.obj) && r.act == p.act`)if err != nil {panic("new model error: " + err.Error())}e, err := casbin.NewEnforcer(m, a)if err != nil {panic("new casbin enforcer error: " + err.Error())}e.LoadPolicy()// 添加策略ok, err := e.AddPolicy("admin", "/api/user", "GET")log.Println("add admin /api/user GET: ", ok, err)ok, err = e.AddGroupingPolicy("leo", "admin")log.Println("add leo to admin group: ", ok, err)e.SavePolicy()ok, err = e.Enforce("leo", "/api/user", "GET")log.Println("leo GET /api/user :", ok, err)ok, err = e.Enforce("leo", "/api/user", "DELETE")log.Println("leo DELETE /api/user :", ok, err)
}

上述代码默认使用的gormadapter.CasbinRule对应的Go结构和数据库表如下

type CasbinRule struct {ID    uint   `gorm:"primaryKey;autoIncrement"`Ptype string `gorm:"size:100"`V0    string `gorm:"size:100"`V1    string `gorm:"size:100"`V2    string `gorm:"size:100"`V3    string `gorm:"size:100"`V4    string `gorm:"size:100"`V5    string `gorm:"size:100"`
}

2. 权限配置以及增删改查

以上准备知识，仅了解和casbin基本操作以及如何配合gorm存储到DB中，还需要完善权限，以及提供增删改查操作

2.1 策略和组使用规范

casbin的policy十分灵活，具体到自己业务使用中，我这里按以下两条规则使用，基本能满足业务需求

1. 所有策略只针对角色组设置
2. 用户关联到组(一个用户可以有多个组)

如下，两个角色组admin和user组，admin组能查询和删除用户，user组只能查询用户

ptype	v0	v1	v2	v3	v4	v5
p	admin	/api/user	GET
p	admin	/api/user	DELETE
p	user	/api/user	GET
…	…	…
g	leo	admin
g	leo2	user

基础代码如下，下一节给CasbinService添加增删改查功能

package mainimport ("github.com/casbin/casbin/v2""github.com/casbin/casbin/v2/model"gormadapter "github.com/casbin/gorm-adapter/v3""gorm.io/gorm"
)type CasbinService struct {enforcer *casbin.Enforceradapter  *gormadapter.Adapter
}func NewCasbinService(db *gorm.DB) (*CasbinService, error) {a, err := gormadapter.NewAdapterByDB(db)if err != nil {return nil, err}m, err := model.NewModelFromString(`[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) && keyMatch2(r.obj,p.obj) && r.act == p.act`)if err != nil {return nil, err}e, err := casbin.NewEnforcer(m, a)if err != nil {return nil, err}return &CasbinService{adapter: a, enforcer: e}, nil
}

2.2 用户以及组关系的增删改查

2.2.1 获取所有用户以及关联的角色

根据2.1中示范数据，预期输出

[{"username": "leo","roleNames": ["admin"]
}, {"username": "leo2","roleNames": ["user"]
}]

获取所有用户以及关联的角色代码片段

type User struct {UserName  stringRoleNames []string
}// 获取所有用户以及关联的角色
func (c *CasbinService) GetUsers() (users []User) {p := c.enforcer.GetGroupingPolicy()usernameUser := make(map[string]*User, 0)for _, _p := range p {username, usergroup := _p[0], _p[1]if v, ok := usernameUser[username]; ok {usernameUser[username].RoleNames = append(v.RoleNames, usergroup)} else {usernameUser[username] = &User{UserName: username, RoleNames: []string{usergroup}}}}for _, v := range usernameUser {users = append(users, *v)}return
}

2.2.2 角色组中添加用户

// 角色组中添加用户, 没有组默认创建
func (c *CasbinService) UpdateUserRole(username, rolename string) error {_, err := c.enforcer.AddGroupingPolicy(username, rolename)return err
}

2.2.3 角色组中删除用户

// 角色组中删除用户
func (c *CasbinService) DeleteUserRole(username, rolename string) error {_, err := c.enforcer.RemoveGroupingPolicy(username, rolename)return err
}

2.3 角色组权限的增删改查

2.3.1 获取所有角色组权限

根据2.1中示范数据，预期输出形式

[{"roleName": "admin","url": "/api/user","method": "DELETE"
}, {"roleName": "admin","url": "/api/user","method": "GET"
}, {"roleName": "user","url": "/api/user","method": "GET"
}]

获取所有角色组权限

```go
// (RoleName, Url, Method) 对应于 `CasbinRule` 表中的 (v0, v1, v2)
type RolePolicy struct {RoleName string `gorm:"column:v0"`Url      string `gorm:"column:v1"`Method   string `gorm:"column:v2"`
}// 获取所有角色组权限
func (c *CasbinService) GetRolePolicy() (roles []RolePolicy, err error) {err = c.adapter.GetDb().Model(&gormadapter.CasbinRule{}).Where("ptype = 'p'").Find(&roles).Errorif err != nil {return nil, err}return
}

2.3.2 创建角色组权限

// 创建角色组权限, 已有的会忽略
func (c *CasbinService) CreateRolePolicy(r RolePolicy) error {// 不直接操作数据库，利用enforcer简化操作err := c.enforcer.LoadPolicy()if err != nil {return err}_, err = c.enforcer.AddPolicy(r.RoleName, r.Url, r.Method)if err != nil {return err}return c.enforcer.SavePolicy()
}

2.3.3 修改角色组权限

// 修改角色组权限
func (c *CasbinService) UpdateRolePolicy(old, new RolePolicy) error {_, err := c.enforcer.UpdatePolicy([]string{old.RoleName, old.Url, old.Method},[]string{new.RoleName, new.Url, new.Method})if err != nil {return err}return c.enforcer.SavePolicy()
}

2.3.4 删除角色组权限

// 删除角色组权限
func (c *CasbinService) DeleteRolePolicy(r RolePolicy) error {_, err := c.enforcer.RemovePolicy(r.RoleName, r.Url, r.Method)if err != nil {return err}return c.enforcer.SavePolicy()
}

2.3.5 验证用户权限

// 验证用户权限
func (c *CasbinService) CanAccess(username, url, method string) (ok bool, err error) {return c.enforcer.Enforce(username, url, method)
}

3. 测试以及完整代码

3.1 casbin_service.go

package mainimport ("github.com/casbin/casbin/v2""github.com/casbin/casbin/v2/model"gormadapter "github.com/casbin/gorm-adapter/v3""gorm.io/gorm"
)/*
按如下约定:1. 所有策略只针对角色组设置2. 用户关联到组(一个用户可以有多个组)
+-------+-------+-----------+--------+----+----+----+
| ptype | v0    | v1        | v2     | v3 | v4 | v5 |
+-------+-------+-----------+--------+----+----+----+
| p     | admin | /api/user | GET    |    |    |    |
+-------+-------+-----------+--------+----+----+----+
| p     | admin | /api/user | DELETE |    |    |    |
+-------+-------+-----------+--------+----+----+----+
| p     | user  | /api/user | GET    |    |    |    |
+-------+-------+-----------+--------+----+----+----+
| ...   | ...   | ...       |        |    |    |    |
+-------+-------+-----------+--------+----+----+----+
| g     | leo   | admin     |        |    |    |    |
+-------+-------+-----------+--------+----+----+----+
| g     | leo2  | admin     |        |    |    |    |
+-------+-------+-----------+--------+----+----+----+
| g     | leo3  | user      |        |    |    |    |
+-------+-------+-----------+--------+----+----+----+
*/
type CasbinService struct {enforcer *casbin.Enforceradapter  *gormadapter.Adapter
}func NewCasbinService(db *gorm.DB) (*CasbinService, error) {a, err := gormadapter.NewAdapterByDB(db)if err != nil {return nil, err}m, err := model.NewModelFromString(`[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) && keyMatch2(r.obj,p.obj) && r.act == p.act`)if err != nil {return nil, err}e, err := casbin.NewEnforcer(m, a)if err != nil {return nil, err}return &CasbinService{adapter: a, enforcer: e}, nil
}// (RoleName, Url, Method) 对应于 `CasbinRule` 表中的 (v0, v1, v2)
type RolePolicy struct {RoleName string `gorm:"column:v0"`Url      string `gorm:"column:v1"`Method   string `gorm:"column:v2"`
}// 获取所有角色组权限
func (c *CasbinService) GetRolePolicy() (roles []RolePolicy, err error) {err = c.adapter.GetDb().Model(&gormadapter.CasbinRule{}).Where("ptype = 'p'").Find(&roles).Errorif err != nil {return nil, err}return
}// 创建角色组权限, 已有的会忽略
func (c *CasbinService) CreateRolePolicy(r RolePolicy) error {// 不直接操作数据库，利用enforcer简化操作err := c.enforcer.LoadPolicy()if err != nil {return err}_, err = c.enforcer.AddPolicy(r.RoleName, r.Url, r.Method)if err != nil {return err}return c.enforcer.SavePolicy()
}// 修改角色组权限
func (c *CasbinService) UpdateRolePolicy(old, new RolePolicy) error {_, err := c.enforcer.UpdatePolicy([]string{old.RoleName, old.Url, old.Method},[]string{new.RoleName, new.Url, new.Method})if err != nil {return err}return c.enforcer.SavePolicy()
}// 删除角色组权限
func (c *CasbinService) DeleteRolePolicy(r RolePolicy) error {_, err := c.enforcer.RemovePolicy(r.RoleName, r.Url, r.Method)if err != nil {return err}return c.enforcer.SavePolicy()
}type User struct {UserName  stringRoleNames []string
}// 获取所有用户以及关联的角色
func (c *CasbinService) GetUsers() (users []User) {p := c.enforcer.GetGroupingPolicy()usernameUser := make(map[string]*User, 0)for _, _p := range p {username, usergroup := _p[0], _p[1]if v, ok := usernameUser[username]; ok {usernameUser[username].RoleNames = append(v.RoleNames, usergroup)} else {usernameUser[username] = &User{UserName: username, RoleNames: []string{usergroup}}}}for _, v := range usernameUser {users = append(users, *v)}return
}// 角色组中添加用户, 没有组默认创建
func (c *CasbinService) UpdateUserRole(username, rolename string) error {_, err := c.enforcer.AddGroupingPolicy(username, rolename)return err
}// 角色组中删除用户
func (c *CasbinService) DeleteUserRole(username, rolename string) error {_, err := c.enforcer.RemoveGroupingPolicy(username, rolename)return err
}// 验证用户权限
func (c *CasbinService) CanAccess(username, url, method string) (ok bool, err error) {return c.enforcer.Enforce(username, url, method)
}

3.2 casbin_service_test.go

package mainimport ("testing""github.com/glebarez/sqlite""gorm.io/gorm"
)func TestCasbinService(t *testing.T) {db, err := gorm.Open(sqlite.Open("test.db"), &gorm.Config{})if err != nil {panic("failed to connect database")}s, err := NewCasbinService(db)if err != nil {t.Fatalf("new service error: %v", err)}// 创建个用户，分别关联到`admin`和`user`组, `leo2`既是`admin`组又是`user`组t.Logf("create user: leo with group: admin result: %v", s.UpdateUserRole("leo", "admin"))t.Logf("create user: leo with group: admin result: %v", s.UpdateUserRole("leo2", "admin"))t.Logf("create user: leo with group: admin result: %v", s.UpdateUserRole("leo2", "user"))t.Log()t.Logf("users is: %v\n", s.GetUsers())// 针对`admin`和`user`组创建三条策略t.Log("create admin /api/user GET: ", s.CreateRolePolicy(RolePolicy{RoleName: "admin", Url: "/api/user", Method: "GET"}))t.Log("create admin /api/user DELETE: ", s.CreateRolePolicy(RolePolicy{RoleName: "admin", Url: "/api/user", Method: "DELETE"}))t.Log("create user /api/user GET: ", s.CreateRolePolicy(RolePolicy{RoleName: "user", Url: "/api/user", Method: "GET"}))t.Log("all policy is: ")t.Log(s.GetRolePolicy())t.Log("delete admin /api/user GET", s.DeleteRolePolicy(RolePolicy{RoleName: "admin", Url: "/api/user", Method: "GET"}))
}

3.3测试结果

4. 结语

基本的权限模型设计以及操作函数均已设计正常， 下一章开始结合gin框架设计一个中间件， 实现casbin权限验证