Add an authorization middleware that supports ACL, RBAC based on casbin. (#939)

* Add an authorization middleware that supports ACL, RBAC based on casbin.
fix some coveralls check.
change test file with new rule.
renaming the prefix Authz to CasbinAuth
use built-in SetBasicAuth method in test file.
export all casbin auth configs.

* fix example code

Author: xqbumu

middleware/casbin_auth.go

@@ -0,0 +1,101 @@
+// Package middleware CasbinAuth provides handlers to enable ACL, RBAC, ABAC authorization support.
+// Simple Usage:
+// package main
+//
+// import (
+// 	"github.com/casbin/casbin"
+// 	"github.com/labstack/echo"
+// 	"github.com/labstack/echo/middleware"
+// )
+//
+// func main() {
+// 	e := echo.New()
+//
+// 	// mediate the access for every request
+// 	e.Use(middleware.CasbinAuth(casbin.NewEnforcer("casbin_auth_model.conf", "casbin_auth_policy.csv")))
+//
+// 	e.Logger.Fatal(e.Start(":1323"))
+// }
+//
+// Advanced Usage:
+//
+//	func main(){
+//		ce := casbin.NewEnforcer("casbin_auth_model.conf", "")
+//		ce.AddRoleForUser("alice", "admin")
+//		ce.AddPolicy(...)
+//
+//		e := echo.New()
+//
+//		echo.Use(middleware.CasbinAuth(ce))
+//
+//		e.Logger.Fatal(e.Start(":1323"))
+//	}
+package middleware
+
+import (
+	"github.com/casbin/casbin"
+	"github.com/labstack/echo"
+)
+
+type (
+	// CasbinAuthConfig defines the config for CasbinAuth middleware.
+	CasbinAuthConfig struct {
+		// Skipper defines a function to skip middleware.
+		Skipper Skipper
+		// Enforcer CasbinAuth main rule.
+		// Required.
+		Enforcer *casbin.Enforcer
+	}
+)
+
+var (
+	// DefaultCasbinAuthConfig is the default CasbinAuth middleware config.
+	DefaultCasbinAuthConfig = CasbinAuthConfig{
+		Skipper: DefaultSkipper,
+	}
+)
+
+// CasbinAuth returns an CasbinAuth middleware.
+//
+// For valid credentials it calls the next handler.
+// For missing or invalid credentials, it sends "401 - Unauthorized" response.
+func CasbinAuth(ce *casbin.Enforcer) echo.MiddlewareFunc {
+	c := DefaultCasbinAuthConfig
+	c.Enforcer = ce
+	return CasbinAuthWithConfig(c)
+}
+
+// CasbinAuthWithConfig returns an CasbinAuth middleware with config.
+// See `CasbinAuth()`.
+func CasbinAuthWithConfig(config CasbinAuthConfig) echo.MiddlewareFunc {
+	// Defaults
+	if config.Skipper == nil {
+		config.Skipper = DefaultCasbinAuthConfig.Skipper
+	}
+
+	return func(next echo.HandlerFunc) echo.HandlerFunc {
+		return func(c echo.Context) error {
+			if config.Skipper(c) || config.CheckPermission(c) {
+				return next(c)
+			}
+
+			return echo.ErrForbidden
+		}
+	}
+}
+
+// GetUserName gets the user name from the request.
+// Currently, only HTTP basic authentication is supported
+func (a *CasbinAuthConfig) GetUserName(c echo.Context) string {
+	username, _, _ := c.Request().BasicAuth()
+	return username
+}
+
+// CheckPermission checks the user/method/path combination from the request.
+// Returns true (permission granted) or false (permission forbidden)
+func (a *CasbinAuthConfig) CheckPermission(c echo.Context) bool {
+	user := a.GetUserName(c)
+	method := c.Request().Method
+	path := c.Request().URL.Path
+	return a.Enforcer.Enforce(user, path, method)
+}

middleware/casbin_auth_model.conf

@@ -0,0 +1,14 @@
+[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) && (r.act == p.act || p.act == "*")

middleware/casbin_auth_policy.csv

@@ -0,0 +1,7 @@
+p, alice, /dataset1/*, GET
+p, alice, /dataset1/resource1, POST
+p, bob, /dataset2/resource1, *
+p, bob, /dataset2/resource2, GET
+p, bob, /dataset2/folder1/*, POST
+p, dataset1_admin, /dataset1/*, *
+g, cathy, dataset1_admin

middleware/casbin_auth_test.go

@@ -0,0 +1,86 @@
+package middleware
+
+import (
+	"net/http"
+	"net/http/httptest"
+	"testing"
+
+	"github.com/casbin/casbin"
+	"github.com/labstack/echo"
+)
+
+func testRequest(t *testing.T, ce *casbin.Enforcer, user string, path string, method string, code int) {
+	e := echo.New()
+	req := httptest.NewRequest(method, path, nil)
+	req.SetBasicAuth(user, "secret")
+	res := httptest.NewRecorder()
+	c := e.NewContext(req, res)
+	h := CasbinAuth(ce)(func(c echo.Context) error {
+		return c.String(http.StatusOK, "test")
+	})
+
+	err := h(c)
+
+	if err != nil {
+		if errObj, ok := err.(*echo.HTTPError); ok {
+			if errObj.Code != code {
+				t.Errorf("%s, %s, %s: %d, supposed to be %d", user, path, method, errObj.Code, code)
+			}
+		} else {
+			t.Error(err)
+		}
+	} else {
+		if c.Response().Status != code {
+			t.Errorf("%s, %s, %s: %d, supposed to be %d", user, path, method, c.Response().Status, code)
+		}
+	}
+}
+
+func TestCasbinAuth(t *testing.T) {
+	ce := casbin.NewEnforcer("casbin_auth_model.conf", "casbin_auth_policy.csv")
+
+	testRequest(t, ce, "alice", "/dataset1/resource1", echo.GET, 200)
+	testRequest(t, ce, "alice", "/dataset1/resource1", echo.POST, 200)
+	testRequest(t, ce, "alice", "/dataset1/resource2", echo.GET, 200)
+	testRequest(t, ce, "alice", "/dataset1/resource2", echo.POST, 403)
+}
+
+func TestPathWildcard(t *testing.T) {
+	ce := casbin.NewEnforcer("casbin_auth_model.conf", "casbin_auth_policy.csv")
+
+	testRequest(t, ce, "bob", "/dataset2/resource1", "GET", 200)
+	testRequest(t, ce, "bob", "/dataset2/resource1", "POST", 200)
+	testRequest(t, ce, "bob", "/dataset2/resource1", "DELETE", 200)
+	testRequest(t, ce, "bob", "/dataset2/resource2", "GET", 200)
+	testRequest(t, ce, "bob", "/dataset2/resource2", "POST", 403)
+	testRequest(t, ce, "bob", "/dataset2/resource2", "DELETE", 403)
+
+	testRequest(t, ce, "bob", "/dataset2/folder1/item1", "GET", 403)
+	testRequest(t, ce, "bob", "/dataset2/folder1/item1", "POST", 200)
+	testRequest(t, ce, "bob", "/dataset2/folder1/item1", "DELETE", 403)
+	testRequest(t, ce, "bob", "/dataset2/folder1/item2", "GET", 403)
+	testRequest(t, ce, "bob", "/dataset2/folder1/item2", "POST", 200)
+	testRequest(t, ce, "bob", "/dataset2/folder1/item2", "DELETE", 403)
+}
+
+func TestRBAC(t *testing.T) {
+	ce := casbin.NewEnforcer("casbin_auth_model.conf", "casbin_auth_policy.csv")
+
+	// cathy can access all /dataset1/* resources via all methods because it has the dataset1_admin role.
+	testRequest(t, ce, "cathy", "/dataset1/item", "GET", 200)
+	testRequest(t, ce, "cathy", "/dataset1/item", "POST", 200)
+	testRequest(t, ce, "cathy", "/dataset1/item", "DELETE", 200)
+	testRequest(t, ce, "cathy", "/dataset2/item", "GET", 403)
+	testRequest(t, ce, "cathy", "/dataset2/item", "POST", 403)
+	testRequest(t, ce, "cathy", "/dataset2/item", "DELETE", 403)
+
+	// delete all roles on user cathy, so cathy cannot access any resources now.
+	ce.DeleteRolesForUser("cathy")
+
+	testRequest(t, ce, "cathy", "/dataset1/item", "GET", 403)
+	testRequest(t, ce, "cathy", "/dataset1/item", "POST", 403)
+	testRequest(t, ce, "cathy", "/dataset1/item", "DELETE", 403)
+	testRequest(t, ce, "cathy", "/dataset2/item", "GET", 403)
+	testRequest(t, ce, "cathy", "/dataset2/item", "POST", 403)
+	testRequest(t, ce, "cathy", "/dataset2/item", "DELETE", 403)
+}