|
| 1 | +--- |
| 2 | +title: Casbin Auth |
| 3 | +description: Autoriza requests con la biblioteca de control de acceso Casbin usando un middleware personalizado pequeño. |
| 4 | +sidebar: |
| 5 | + order: 4 |
| 6 | +--- |
| 7 | + |
| 8 | +[Casbin](https://github.com/casbin/casbin) es una biblioteca de control de acceso open-source |
| 9 | +potente y eficiente para Go. Soporta aplicar autorización en muchos modelos: |
| 10 | + |
| 11 | +- ACL (Access Control List) |
| 12 | +- ACL con superuser |
| 13 | +- ACL sin usuarios, útil para sistemas sin autenticación o log-ins de usuario |
| 14 | +- ACL sin recursos: apunta a un tipo de recurso (por ejemplo `write-article`, `read-log`) en lugar de a uno individual |
| 15 | +- RBAC (Role-Based Access Control) |
| 16 | +- RBAC con roles de recursos: tanto usuarios como recursos pueden tener roles |
| 17 | +- RBAC con dominios/tenants: los usuarios pueden tener conjuntos de roles distintos por dominio/tenant |
| 18 | +- ABAC (Attribute-Based Access Control) |
| 19 | +- RESTful |
| 20 | +- Deny-override: se soportan reglas allow y deny; deny sobrescribe allow |
| 21 | + |
| 22 | +Consulta el [resumen de API](https://casbin.org/docs/api-overview) y la |
| 23 | +[documentación de Casbin](https://casbin.org/docs/) para más detalles. |
| 24 | + |
| 25 | +## Dependencias |
| 26 | + |
| 27 | +```bash |
| 28 | +go get github.com/casbin/casbin/v3 |
| 29 | +``` |
| 30 | + |
| 31 | +```go |
| 32 | +import ( |
| 33 | + "github.com/casbin/casbin/v3" |
| 34 | +) |
| 35 | +``` |
| 36 | + |
| 37 | +## Implementación |
| 38 | + |
| 39 | +Echo no incluye un middleware Casbin; la integración es un wrapper pequeño alrededor del |
| 40 | +enforcer de Casbin: |
| 41 | + |
| 42 | +```go |
| 43 | +// NewCasbinMiddleware returns middleware for Casbin (https://casbin.org/). |
| 44 | +func NewCasbinMiddleware(enforcer *casbin.Enforcer, userGetter func(*echo.Context) (string, error)) echo.MiddlewareFunc { |
| 45 | + return func(next echo.HandlerFunc) echo.HandlerFunc { |
| 46 | + return func(c *echo.Context) error { |
| 47 | + username, err := userGetter(c) |
| 48 | + if err != nil { |
| 49 | + return echo.ErrUnauthorized.Wrap(err) |
| 50 | + } |
| 51 | + if pass, err := enforcer.Enforce(username, c.Request().URL.Path, c.Request().Method); err != nil { |
| 52 | + return echo.ErrInternalServerError.Wrap(err) |
| 53 | + } else if !pass { |
| 54 | + return echo.NewHTTPError(http.StatusForbidden, "access denied") |
| 55 | + } |
| 56 | + return next(c) |
| 57 | + } |
| 58 | + } |
| 59 | +} |
| 60 | +``` |
| 61 | + |
| 62 | +## Ejemplo |
| 63 | + |
| 64 | +Crea un archivo de modelo Casbin `auth_model.conf`: |
| 65 | + |
| 66 | +```ini |
| 67 | +[request_definition] |
| 68 | +r = sub, obj, act |
| 69 | + |
| 70 | +[policy_definition] |
| 71 | +p = sub, obj, act |
| 72 | + |
| 73 | +[role_definition] |
| 74 | +g = _, _ |
| 75 | + |
| 76 | +[policy_effect] |
| 77 | +e = some(where (p.eft == allow)) |
| 78 | + |
| 79 | +[matchers] |
| 80 | +m = g(r.sub, p.sub) && keyMatch(r.obj, p.obj) && (r.act == p.act || p.act == "*") |
| 81 | +``` |
| 82 | + |
| 83 | +Crea un archivo de policy Casbin `auth_policy.csv`: |
| 84 | + |
| 85 | +```csv |
| 86 | +p, 1234567890, /dataset1/*, GET |
| 87 | +p, alice, /dataset1/*, GET |
| 88 | +p, alice, /dataset1/resource1, POST |
| 89 | +p, bob, /dataset2/resource1, * |
| 90 | +p, bob, /dataset2/resource2, GET |
| 91 | +p, bob, /dataset2/folder1/*, POST |
| 92 | +p, dataset1_admin, /dataset1/*, * |
| 93 | +g, cathy, dataset1_admin |
| 94 | +``` |
| 95 | + |
| 96 | +La autenticación y la autorización son responsabilidades separadas. Autentica al usuario con |
| 97 | +otro middleware (como JWT o Basic Auth), y luego proporciona un `userGetter` para que Casbin |
| 98 | +pueda autorizar el request. |
| 99 | + |
| 100 | +### Con JWT |
| 101 | + |
| 102 | +```go |
| 103 | +e.Use(echojwt.JWT([]byte("secret"))) // JWT middleware does authentication |
| 104 | +jwtUser := func(c *echo.Context) (string, error) { // JWT user getter for Casbin authorization |
| 105 | + token, err := echo.ContextGet[*jwt.Token](c, "user") |
| 106 | + if err != nil { |
| 107 | + return "", err |
| 108 | + } |
| 109 | + return token.Claims.GetSubject() |
| 110 | +} |
| 111 | +e.Use(NewCasbinMiddleware(ce, jwtUser)) // Casbin does authorization |
| 112 | +``` |
| 113 | + |
| 114 | +Pruébalo con: |
| 115 | + |
| 116 | +```bash |
| 117 | +curl -v "http://localhost:8080/dataset1/any" -H "Authorization: Bearer eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJzdWIiOiIxMjM0NTY3ODkwIiwibmFtZSI6IkpvaG4gRG9lIiwiYWRtaW4iOnRydWV9.TJVA95OrM7E2cBab30RMHrHDcEfxjoYZgeFONFh7HgQ" |
| 118 | +``` |
| 119 | + |
| 120 | +### Con Basic Auth |
| 121 | + |
| 122 | +```go |
| 123 | +// BasicAuth middleware does authentication |
| 124 | +e.Use(middleware.BasicAuth(func(c *echo.Context, user, password string) (bool, error) { |
| 125 | + return subtle.ConstantTimeCompare([]byte(user), []byte("alice")) == 1 && |
| 126 | + subtle.ConstantTimeCompare([]byte(password), []byte("password")) == 1, nil |
| 127 | +})) |
| 128 | +basicAuthUser := func(c *echo.Context) (string, error) { // Basic auth user getter for Casbin authorization |
| 129 | + username, _, _ := c.Request().BasicAuth() // password is verified by the BasicAuth middleware above |
| 130 | + return username, nil |
| 131 | +} |
| 132 | +e.Use(NewCasbinMiddleware(ce, basicAuthUser)) // Casbin does authorization |
| 133 | +``` |
| 134 | + |
| 135 | +Pruébalo con: |
| 136 | + |
| 137 | +```bash |
| 138 | +# should pass |
| 139 | +curl -v -u "alice:password" http://localhost:8080/dataset1/any |
| 140 | +# should fail |
| 141 | +curl -v -u "alice:password" http://localhost:8080/dataset2/resource2 |
| 142 | +``` |
| 143 | + |
| 144 | +### Ejemplo completo de Casbin + JWT |
| 145 | + |
| 146 | +```go |
| 147 | +package main |
| 148 | + |
| 149 | +import ( |
| 150 | + "log/slog" |
| 151 | + "net/http" |
| 152 | + |
| 153 | + "github.com/casbin/casbin/v3" |
| 154 | + "github.com/golang-jwt/jwt/v5" |
| 155 | + echojwt "github.com/labstack/echo-jwt/v5" |
| 156 | + "github.com/labstack/echo/v5" |
| 157 | +) |
| 158 | + |
| 159 | +// NewCasbinMiddleware returns middleware for Casbin (https://casbin.org/). |
| 160 | +func NewCasbinMiddleware(enforcer *casbin.Enforcer, userGetter func(*echo.Context) (string, error)) echo.MiddlewareFunc { |
| 161 | + return func(next echo.HandlerFunc) echo.HandlerFunc { |
| 162 | + return func(c *echo.Context) error { |
| 163 | + username, err := userGetter(c) |
| 164 | + if err != nil { |
| 165 | + return echo.ErrUnauthorized.Wrap(err) |
| 166 | + } |
| 167 | + if pass, err := enforcer.Enforce(username, c.Request().URL.Path, c.Request().Method); err != nil { |
| 168 | + return echo.ErrInternalServerError.Wrap(err) |
| 169 | + } else if !pass { |
| 170 | + return echo.NewHTTPError(http.StatusForbidden, "access denied") |
| 171 | + } |
| 172 | + return next(c) |
| 173 | + } |
| 174 | + } |
| 175 | +} |
| 176 | + |
| 177 | +func main() { |
| 178 | + e := echo.New() |
| 179 | + |
| 180 | + ce, err := casbin.NewEnforcer("auth_model.conf", "auth_policy.csv") |
| 181 | + if err != nil { |
| 182 | + slog.Error("failed to initialize Casbin enforcer", "error", err) |
| 183 | + } |
| 184 | + |
| 185 | + e.Use(echojwt.JWT([]byte("secret"))) // JWT middleware does authentication |
| 186 | + jwtUser := func(c *echo.Context) (string, error) { // JWT user getter for Casbin authorization |
| 187 | + token, err := echo.ContextGet[*jwt.Token](c, "user") |
| 188 | + if err != nil { |
| 189 | + return "", err |
| 190 | + } |
| 191 | + return token.Claims.GetSubject() |
| 192 | + } |
| 193 | + e.Use(NewCasbinMiddleware(ce, jwtUser)) // Casbin does authorization |
| 194 | + |
| 195 | + e.GET("/*", func(c *echo.Context) error { |
| 196 | + return c.String(http.StatusOK, "Hello, World!") |
| 197 | + }) |
| 198 | + |
| 199 | + if err := e.Start(":8080"); err != nil { |
| 200 | + e.Logger.Error("failed to start server", "error", err) |
| 201 | + } |
| 202 | +} |
| 203 | +``` |
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