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kubernetes.go
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kubernetes.go
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package authorization
import (
"context"
"encoding/base64"
"encoding/json"
"fmt"
"os"
"strings"
"time"
"k8s.io/apimachinery/pkg/util/clock"
"github.com/grpc-ecosystem/go-grpc-middleware/util/metautils"
"github.com/patrickmn/go-cache"
authv1 "k8s.io/api/authentication/v1"
metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
"k8s.io/client-go/kubernetes"
"k8s.io/client-go/rest"
"github.com/armadaproject/armada/internal/common/armadaerrors"
"github.com/armadaproject/armada/internal/common/auth/configuration"
)
type TokenReviewer interface {
ReviewToken(ctx context.Context, clusterUrl string, token string, ca []byte) (*authv1.TokenReview, error)
}
type KubernetesTokenReviewer struct{}
func (reviewer *KubernetesTokenReviewer) ReviewToken(ctx context.Context, clusterUrl string, token string, ca []byte) (*authv1.TokenReview, error) {
config := &rest.Config{
Host: clusterUrl,
BearerToken: token,
TLSClientConfig: rest.TLSClientConfig{CAData: ca},
}
clientSet, err := kubernetes.NewForConfig(config)
if err != nil {
return &authv1.TokenReview{}, err
}
tr := authv1.TokenReview{
Spec: authv1.TokenReviewSpec{
Token: token,
},
}
return clientSet.AuthenticationV1().TokenReviews().Create(ctx, &tr, metav1.CreateOptions{})
}
type KubernetesNativeAuthService struct {
KidMappingFileLocation string
TokenCache *cache.Cache
InvalidTokenExpiry int64
TokenReviewer TokenReviewer
Clock clock.Clock
}
func NewKubernetesNativeAuthService(config configuration.KubernetesAuthConfig) KubernetesNativeAuthService {
cache := cache.New(5*time.Minute, 5*time.Minute)
return KubernetesNativeAuthService{
KidMappingFileLocation: config.KidMappingFileLocation,
TokenCache: cache,
InvalidTokenExpiry: config.InvalidTokenExpiry,
TokenReviewer: &KubernetesTokenReviewer{},
Clock: clock.RealClock{},
}
}
type CacheData struct {
Name string `json:"name"`
Valid bool `json:"valid"`
}
func (authService *KubernetesNativeAuthService) Name() string {
return "KubernetesNative"
}
func (authService *KubernetesNativeAuthService) Authenticate(ctx context.Context) (Principal, error) {
// Retrieve token from context.
authHeader := strings.SplitN(metautils.ExtractIncoming(ctx).Get("authorization"), " ", 2)
if len(authHeader) < 2 || authHeader[0] != "KubernetesAuth" {
return nil, &armadaerrors.ErrMissingCredentials{
AuthService: authService.Name(),
}
}
token, ca, err := parseAuth(authHeader[1])
if err != nil {
return nil, &armadaerrors.ErrInvalidCredentials{
AuthService: authService.Name(),
}
}
// Get token time
expirationTime, err := parseTime(token)
if err != nil {
return nil, &armadaerrors.ErrInvalidCredentials{
AuthService: authService.Name(),
Message: err.Error(),
}
}
if authService.Clock.Now().After(expirationTime) {
return nil, &armadaerrors.ErrInvalidCredentials{
AuthService: authService.Name(),
Message: "invalid token, expired",
}
}
// Check Cache
data, found := authService.TokenCache.Get(token)
if found {
if cacheInfo, ok := data.(CacheData); ok {
if cacheInfo.Valid {
return NewStaticPrincipal(cacheInfo.Name, []string{cacheInfo.Name}), nil
} else {
return nil, &armadaerrors.ErrInvalidCredentials{
AuthService: authService.Name(),
Message: "token invalid",
}
}
}
}
// Get URL from token KID
url, err := authService.getClusterURL(token)
if err != nil {
return nil, &armadaerrors.ErrInvalidCredentials{
AuthService: authService.Name(),
Message: err.Error(),
}
}
// Make request to token review endpoint
name, err := authService.reviewToken(ctx, url, token, []byte(ca))
if err != nil {
// reviewToken returns appropriate armadaerrors.
return nil, err
}
// Add to cache
authService.TokenCache.Set(
token,
CacheData{
Name: name,
Valid: true,
},
expirationTime.Sub(time.Now()))
// Return very basic Principal
return NewStaticPrincipal(name, []string{name}), nil
}
func (authService *KubernetesNativeAuthService) getClusterURL(token string) (string, error) {
header := strings.Split(token, ".")[0]
decoded, err := base64.RawURLEncoding.DecodeString(header)
if err != nil {
return "", err
}
var unmarshalled struct {
Kid string `json:"kid"`
}
if err := json.Unmarshal(decoded, &unmarshalled); err != nil {
return "", err
}
if err = validateKid(unmarshalled.Kid); err != nil {
return "", err
}
url, err := os.ReadFile(authService.KidMappingFileLocation + unmarshalled.Kid)
if err != nil {
return "", err
}
return string(url), nil
}
func (authService *KubernetesNativeAuthService) reviewToken(ctx context.Context, clusterUrl string, token string, ca []byte) (string, error) {
result, err := authService.TokenReviewer.ReviewToken(ctx, clusterUrl, token, ca)
if err != nil {
// TODO(clif) Hard to tell if this should be internal auth error
// or invalid creds still.
return "", &armadaerrors.ErrInternalAuthServiceError{
AuthService: authService.Name(),
Message: err.Error(),
}
}
if !result.Status.Authenticated {
authService.TokenCache.Set(token, CacheData{Valid: false}, time.Duration(authService.InvalidTokenExpiry))
return "", &armadaerrors.ErrInvalidCredentials{
AuthService: authService.Name(),
Message: "provided token was rejected by TokenReview",
}
}
return result.Status.User.Username, nil
}
func parseAuth(auth string) (string, string, error) {
jsonData, err := base64.RawURLEncoding.DecodeString(auth)
if err != nil {
return "", "", err
}
var uMbody struct {
Token string `json:"token"`
Ca string `json:"ca"`
}
if err := json.Unmarshal(jsonData, &uMbody); err != nil {
return "", "", err
}
ca, err := base64.RawURLEncoding.DecodeString(uMbody.Ca)
if err != nil {
return "", "", err
}
return uMbody.Token, string(ca), nil
}
func parseTime(token string) (time.Time, error) {
splitToken := strings.Split(token, ".")
if len(splitToken) != 3 {
return time.Time{}, fmt.Errorf("provided JWT token was not of the correct form, should have 3 parts")
}
decoded, err := base64.RawURLEncoding.DecodeString(splitToken[1])
if err != nil {
return time.Time{}, err
}
var uMbody struct {
Expiry int64 `json:"exp"`
}
if err := json.Unmarshal(decoded, &uMbody); err != nil {
return time.Time{}, err
}
if uMbody.Expiry == 0 {
return time.Time{}, fmt.Errorf("token expiry time not set")
}
time := time.Unix(uMbody.Expiry, 0)
return time, nil
}
func validateKid(kid string) error {
if kid == "" {
return fmt.Errorf("kubernetes serviceaccount token KID must not be empty")
}
if strings.Contains(kid, "../") {
return fmt.Errorf("kid appears to contain ../, this appears to be an attack")
}
return nil
}