/*
Copyright 2016 The Kubernetes Authors.

Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at

    http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.
*/

package filters

import (
	"context"
	"fmt"
	"net/http"
	"net/http/httptest"
	"reflect"
	"strings"
	"sync"
	"testing"

	authenticationapi "k8s.io/api/authentication/v1"
	"k8s.io/apimachinery/pkg/runtime"
	serializer "k8s.io/apimachinery/pkg/runtime/serializer"
	"k8s.io/apiserver/pkg/authentication/user"
	"k8s.io/apiserver/pkg/authorization/authorizer"
	"k8s.io/apiserver/pkg/endpoints/request"
)

type impersonateAuthorizer struct{}

func (impersonateAuthorizer) Authorize(ctx context.Context, a authorizer.Attributes) (authorized authorizer.Decision, reason string, err error) {
	user := a.GetUser()

	switch {
	case user.GetName() == "system:admin":
		return authorizer.DecisionAllow, "", nil

	case user.GetName() == "tester":
		return authorizer.DecisionNoOpinion, "", fmt.Errorf("works on my machine")

	case user.GetName() == "deny-me":
		return authorizer.DecisionNoOpinion, "denied", nil
	}

	if len(user.GetGroups()) > 0 && user.GetGroups()[0] == "wheel" && a.GetVerb() == "impersonate" && a.GetResource() == "users" {
		return authorizer.DecisionAllow, "", nil
	}

	if len(user.GetGroups()) > 0 && user.GetGroups()[0] == "sa-impersonater" && a.GetVerb() == "impersonate" && a.GetResource() == "serviceaccounts" {
		return authorizer.DecisionAllow, "", nil
	}

	if len(user.GetGroups()) > 0 && user.GetGroups()[0] == "regular-impersonater" && a.GetVerb() == "impersonate" && a.GetResource() == "users" {
		return authorizer.DecisionAllow, "", nil
	}

	if len(user.GetGroups()) > 1 && user.GetGroups()[1] == "group-impersonater" && a.GetVerb() == "impersonate" && a.GetResource() == "groups" {
		return authorizer.DecisionAllow, "", nil
	}

	if len(user.GetGroups()) > 1 && user.GetGroups()[1] == "extra-setter-scopes" && a.GetVerb() == "impersonate" && a.GetResource() == "userextras" && a.GetSubresource() == "scopes" {
		return authorizer.DecisionAllow, "", nil
	}

	if len(user.GetGroups()) > 1 && (user.GetGroups()[1] == "escaped-scopes" || user.GetGroups()[1] == "almost-escaped-scopes") {
		return authorizer.DecisionAllow, "", nil
	}

	if len(user.GetGroups()) > 1 && user.GetGroups()[1] == "extra-setter-particular-scopes" &&
		a.GetVerb() == "impersonate" && a.GetResource() == "userextras" && a.GetSubresource() == "scopes" && a.GetName() == "scope-a" {
		return authorizer.DecisionAllow, "", nil
	}

	if len(user.GetGroups()) > 1 && user.GetGroups()[1] == "extra-setter-project" && a.GetVerb() == "impersonate" && a.GetResource() == "userextras" && a.GetSubresource() == "project" {
		return authorizer.DecisionAllow, "", nil
	}

	return authorizer.DecisionNoOpinion, "deny by default", nil
}

func TestImpersonationFilter(t *testing.T) {
	testCases := []struct {
		name                    string
		user                    user.Info
		impersonationUser       string
		impersonationGroups     []string
		impersonationUserExtras map[string][]string
		expectedUser            user.Info
		expectedCode            int
	}{
		{
			name: "not-impersonating",
			user: &user.DefaultInfo{
				Name: "tester",
			},
			expectedUser: &user.DefaultInfo{
				Name: "tester",
			},
			expectedCode: http.StatusOK,
		},
		{
			name: "impersonating-error",
			user: &user.DefaultInfo{
				Name: "tester",
			},
			impersonationUser: "anyone",
			expectedUser: &user.DefaultInfo{
				Name: "tester",
			},
			expectedCode: http.StatusForbidden,
		},
		{
			name: "impersonating-group-without-user",
			user: &user.DefaultInfo{
				Name: "tester",
			},
			impersonationGroups: []string{"some-group"},
			expectedUser: &user.DefaultInfo{
				Name: "tester",
			},
			expectedCode: http.StatusInternalServerError,
		},
		{
			name: "impersonating-extra-without-user",
			user: &user.DefaultInfo{
				Name: "tester",
			},
			impersonationUserExtras: map[string][]string{"scopes": {"scope-a"}},
			expectedUser: &user.DefaultInfo{
				Name: "tester",
			},
			expectedCode: http.StatusInternalServerError,
		},
		{
			name: "disallowed-group",
			user: &user.DefaultInfo{
				Name:   "dev",
				Groups: []string{"wheel"},
			},
			impersonationUser:   "system:admin",
			impersonationGroups: []string{"some-group"},
			expectedUser: &user.DefaultInfo{
				Name:   "dev",
				Groups: []string{"wheel"},
			},
			expectedCode: http.StatusForbidden,
		},
		{
			name: "allowed-group",
			user: &user.DefaultInfo{
				Name:   "dev",
				Groups: []string{"wheel", "group-impersonater"},
			},
			impersonationUser:   "system:admin",
			impersonationGroups: []string{"some-group"},
			expectedUser: &user.DefaultInfo{
				Name:   "system:admin",
				Groups: []string{"some-group", "system:authenticated"},
				Extra:  map[string][]string{},
			},
			expectedCode: http.StatusOK,
		},
		{
			name: "disallowed-userextra-1",
			user: &user.DefaultInfo{
				Name:   "dev",
				Groups: []string{"wheel"},
			},
			impersonationUser:       "system:admin",
			impersonationGroups:     []string{"some-group"},
			impersonationUserExtras: map[string][]string{"scopes": {"scope-a"}},
			expectedUser: &user.DefaultInfo{
				Name:   "dev",
				Groups: []string{"wheel"},
			},
			expectedCode: http.StatusForbidden,
		},
		{
			name: "disallowed-userextra-2",
			user: &user.DefaultInfo{
				Name:   "dev",
				Groups: []string{"wheel", "extra-setter-project"},
			},
			impersonationUser:       "system:admin",
			impersonationGroups:     []string{"some-group"},
			impersonationUserExtras: map[string][]string{"scopes": {"scope-a"}},
			expectedUser: &user.DefaultInfo{
				Name:   "dev",
				Groups: []string{"wheel", "extra-setter-project"},
			},
			expectedCode: http.StatusForbidden,
		},
		{
			name: "disallowed-userextra-3",
			user: &user.DefaultInfo{
				Name:   "dev",
				Groups: []string{"wheel", "extra-setter-particular-scopes"},
			},
			impersonationUser:       "system:admin",
			impersonationGroups:     []string{"some-group"},
			impersonationUserExtras: map[string][]string{"scopes": {"scope-a", "scope-b"}},
			expectedUser: &user.DefaultInfo{
				Name:   "dev",
				Groups: []string{"wheel", "extra-setter-particular-scopes"},
			},
			expectedCode: http.StatusForbidden,
		},
		{
			name: "allowed-userextras",
			user: &user.DefaultInfo{
				Name:   "dev",
				Groups: []string{"wheel", "extra-setter-scopes"},
			},
			impersonationUser:       "system:admin",
			impersonationUserExtras: map[string][]string{"scopes": {"scope-a", "scope-b"}},
			expectedUser: &user.DefaultInfo{
				Name:   "system:admin",
				Groups: []string{"system:authenticated"},
				Extra:  map[string][]string{"scopes": {"scope-a", "scope-b"}},
			},
			expectedCode: http.StatusOK,
		},
		{
			name: "percent-escaped-userextras",
			user: &user.DefaultInfo{
				Name:   "dev",
				Groups: []string{"wheel", "escaped-scopes"},
			},
			impersonationUser:       "system:admin",
			impersonationUserExtras: map[string][]string{"example.com%2fescaped%e1%9b%84scopes": {"scope-a", "scope-b"}},
			expectedUser: &user.DefaultInfo{
				Name:   "system:admin",
				Groups: []string{"system:authenticated"},
				Extra:  map[string][]string{"example.com/escapedᛄscopes": {"scope-a", "scope-b"}},
			},
			expectedCode: http.StatusOK,
		},
		{
			name: "almost-percent-escaped-userextras",
			user: &user.DefaultInfo{
				Name:   "dev",
				Groups: []string{"wheel", "almost-escaped-scopes"},
			},
			impersonationUser:       "system:admin",
			impersonationUserExtras: map[string][]string{"almost%zzpercent%xxencoded": {"scope-a", "scope-b"}},
			expectedUser: &user.DefaultInfo{
				Name:   "system:admin",
				Groups: []string{"system:authenticated"},
				Extra:  map[string][]string{"almost%zzpercent%xxencoded": {"scope-a", "scope-b"}},
			},
			expectedCode: http.StatusOK,
		},
		{
			name: "allowed-users-impersonation",
			user: &user.DefaultInfo{
				Name:   "dev",
				Groups: []string{"regular-impersonater"},
			},
			impersonationUser: "tester",
			expectedUser: &user.DefaultInfo{
				Name:   "tester",
				Groups: []string{"system:authenticated"},
				Extra:  map[string][]string{},
			},
			expectedCode: http.StatusOK,
		},
		{
			name: "disallowed-impersonating",
			user: &user.DefaultInfo{
				Name:   "dev",
				Groups: []string{"sa-impersonater"},
			},
			impersonationUser: "tester",
			expectedUser: &user.DefaultInfo{
				Name:   "dev",
				Groups: []string{"sa-impersonater"},
			},
			expectedCode: http.StatusForbidden,
		},
		{
			name: "allowed-sa-impersonating",
			user: &user.DefaultInfo{
				Name:   "dev",
				Groups: []string{"sa-impersonater"},
				Extra:  map[string][]string{},
			},
			impersonationUser: "system:serviceaccount:foo:default",
			expectedUser: &user.DefaultInfo{
				Name:   "system:serviceaccount:foo:default",
				Groups: []string{"system:serviceaccounts", "system:serviceaccounts:foo", "system:authenticated"},
				Extra:  map[string][]string{},
			},
			expectedCode: http.StatusOK,
		},
		{
			name: "anonymous-username-prevents-adding-authenticated-group",
			user: &user.DefaultInfo{
				Name: "system:admin",
			},
			impersonationUser: "system:anonymous",
			expectedUser: &user.DefaultInfo{
				Name:   "system:anonymous",
				Groups: []string{"system:unauthenticated"},
				Extra:  map[string][]string{},
			},
			expectedCode: http.StatusOK,
		},
		{
			name: "unauthenticated-group-prevents-adding-authenticated-group",
			user: &user.DefaultInfo{
				Name: "system:admin",
			},
			impersonationUser:   "unknown",
			impersonationGroups: []string{"system:unauthenticated"},
			expectedUser: &user.DefaultInfo{
				Name:   "unknown",
				Groups: []string{"system:unauthenticated"},
				Extra:  map[string][]string{},
			},
			expectedCode: http.StatusOK,
		},
		{
			name: "unauthenticated-group-prevents-double-adding-authenticated-group",
			user: &user.DefaultInfo{
				Name: "system:admin",
			},
			impersonationUser:   "unknown",
			impersonationGroups: []string{"system:authenticated"},
			expectedUser: &user.DefaultInfo{
				Name:   "unknown",
				Groups: []string{"system:authenticated"},
				Extra:  map[string][]string{},
			},
			expectedCode: http.StatusOK,
		},
		{
			name: "specified-authenticated-group-prevents-double-adding-authenticated-group",
			user: &user.DefaultInfo{
				Name:   "dev",
				Groups: []string{"wheel", "group-impersonater"},
			},
			impersonationUser:   "system:admin",
			impersonationGroups: []string{"some-group", "system:authenticated"},
			expectedUser: &user.DefaultInfo{
				Name:   "system:admin",
				Groups: []string{"some-group", "system:authenticated"},
				Extra:  map[string][]string{},
			},
			expectedCode: http.StatusOK,
		},
		{
			name: "anonymous-user-should-include-unauthenticated-group",
			user: &user.DefaultInfo{
				Name: "system:admin",
			},
			impersonationUser: "system:anonymous",
			expectedUser: &user.DefaultInfo{
				Name:   "system:anonymous",
				Groups: []string{"system:unauthenticated"},
				Extra:  map[string][]string{},
			},
			expectedCode: http.StatusOK,
		},
		{
			name: "anonymous-user-prevents-double-adding-unauthenticated-group",
			user: &user.DefaultInfo{
				Name: "system:admin",
			},
			impersonationUser:   "system:anonymous",
			impersonationGroups: []string{"system:unauthenticated"},
			expectedUser: &user.DefaultInfo{
				Name:   "system:anonymous",
				Groups: []string{"system:unauthenticated"},
				Extra:  map[string][]string{},
			},
			expectedCode: http.StatusOK,
		},
	}

	var ctx context.Context
	var actualUser user.Info
	var lock sync.Mutex

	doNothingHandler := http.HandlerFunc(func(w http.ResponseWriter, req *http.Request) {
		currentCtx := req.Context()
		user, exists := request.UserFrom(currentCtx)
		if !exists {
			actualUser = nil
			return
		}

		actualUser = user

		if _, ok := req.Header[authenticationapi.ImpersonateUserHeader]; ok {
			t.Fatal("user header still present")
		}
		if _, ok := req.Header[authenticationapi.ImpersonateGroupHeader]; ok {
			t.Fatal("group header still present")
		}
		for key := range req.Header {
			if strings.HasPrefix(key, authenticationapi.ImpersonateUserExtraHeaderPrefix) {
				t.Fatalf("extra header still present: %v", key)
			}
		}

	})
	handler := func(delegate http.Handler) http.Handler {
		return http.HandlerFunc(func(w http.ResponseWriter, req *http.Request) {
			defer func() {
				if r := recover(); r != nil {
					t.Errorf("Recovered %v", r)
				}
			}()
			lock.Lock()
			defer lock.Unlock()
			req = req.WithContext(ctx)
			currentCtx := req.Context()

			user, exists := request.UserFrom(currentCtx)
			if !exists {
				actualUser = nil
				return
			} else {
				actualUser = user
			}

			delegate.ServeHTTP(w, req)
		})
	}(WithImpersonation(doNothingHandler, impersonateAuthorizer{}, serializer.NewCodecFactory(runtime.NewScheme())))

	server := httptest.NewServer(handler)
	defer server.Close()

	for _, tc := range testCases {
		t.Run(tc.name, func(t *testing.T) {
			func() {
				lock.Lock()
				defer lock.Unlock()
				ctx = request.WithUser(request.NewContext(), tc.user)
			}()

			req, err := http.NewRequest("GET", server.URL, nil)
			if err != nil {
				t.Errorf("%s: unexpected error: %v", tc.name, err)
				return
			}
			if len(tc.impersonationUser) > 0 {
				req.Header.Add(authenticationapi.ImpersonateUserHeader, tc.impersonationUser)
			}
			for _, group := range tc.impersonationGroups {
				req.Header.Add(authenticationapi.ImpersonateGroupHeader, group)
			}
			for extraKey, values := range tc.impersonationUserExtras {
				for _, value := range values {
					req.Header.Add(authenticationapi.ImpersonateUserExtraHeaderPrefix+extraKey, value)
				}
			}

			resp, err := http.DefaultClient.Do(req)
			if err != nil {
				t.Errorf("%s: unexpected error: %v", tc.name, err)
				return
			}
			if resp.StatusCode != tc.expectedCode {
				t.Errorf("%s: expected %v, actual %v", tc.name, tc.expectedCode, resp.StatusCode)
				return
			}

			if !reflect.DeepEqual(actualUser, tc.expectedUser) {
				t.Errorf("%s: expected %#v, actual %#v", tc.name, tc.expectedUser, actualUser)
				return
			}
		})
	}
}
