package kubeauth import ( "context" "errors" "fmt" "strings" cleanhttp "github.com/hashicorp/go-cleanhttp" "github.com/hashicorp/go-hclog" "gopkg.in/square/go-jose.v2/jwt" authv1 "k8s.io/api/authentication/v1" client_metav1 "k8s.io/apimachinery/pkg/apis/meta/v1" k8s "k8s.io/client-go/kubernetes" client_authv1 "k8s.io/client-go/kubernetes/typed/authentication/v1" client_corev1 "k8s.io/client-go/kubernetes/typed/core/v1" client_rest "k8s.io/client-go/rest" cert "k8s.io/client-go/util/cert" "github.com/hashicorp/consul/agent/consul/authmethod" "github.com/hashicorp/consul/agent/structs" ) func init() { // register this as an available auth method type authmethod.Register("kubernetes", func(logger hclog.Logger, method *structs.ACLAuthMethod) (authmethod.Validator, error) { v, err := NewValidator(method) if err != nil { return nil, err } return v, nil }) } const ( serviceAccountNamespaceField = "serviceaccount.namespace" serviceAccountNameField = "serviceaccount.name" serviceAccountUIDField = "serviceaccount.uid" serviceAccountServiceNameAnnotation = "consul.hashicorp.com/service-name" ) type Config struct { // Host must be a host string, a host:port pair, or a URL to the base of // the Kubernetes API server. Host string `json:",omitempty"` // PEM encoded CA cert for use by the TLS client used to talk with the // Kubernetes API. Every line must end with a newline: \n CACert string `json:",omitempty"` // A service account JWT used to access the TokenReview API to validate // other JWTs during login. It also must be able to read ServiceAccount // annotations. ServiceAccountJWT string `json:",omitempty"` enterpriseConfig `mapstructure:",squash"` } // Validator is the wrapper around the relevant portions of the Kubernetes API // that also conforms to the authmethod.Validator interface. type Validator struct { name string config *Config saGetter client_corev1.ServiceAccountsGetter trGetter client_authv1.TokenReviewsGetter } func NewValidator(method *structs.ACLAuthMethod) (*Validator, error) { if method.Type != "kubernetes" { return nil, fmt.Errorf("%q is not a kubernetes auth method", method.Name) } var config Config if err := authmethod.ParseConfig(method.Config, &config); err != nil { return nil, err } if config.Host == "" { return nil, fmt.Errorf("Config.Host is required") } if config.CACert == "" { return nil, fmt.Errorf("Config.CACert is required") } if _, err := cert.ParseCertsPEM([]byte(config.CACert)); err != nil { return nil, fmt.Errorf("error parsing kubernetes ca cert: %v", err) } // This is the bearer token we give the apiserver to use the API. if config.ServiceAccountJWT == "" { return nil, fmt.Errorf("Config.ServiceAccountJWT is required") } if _, err := jwt.ParseSigned(config.ServiceAccountJWT); err != nil { return nil, fmt.Errorf("Config.ServiceAccountJWT is not a valid JWT: %v", err) } if err := enterpriseValidation(method, &config); err != nil { return nil, err } transport := cleanhttp.DefaultTransport() client, err := k8s.NewForConfig(&client_rest.Config{ Host: config.Host, BearerToken: config.ServiceAccountJWT, Dial: transport.DialContext, TLSClientConfig: client_rest.TLSClientConfig{ CAData: []byte(config.CACert), }, ContentConfig: client_rest.ContentConfig{ ContentType: "application/json", }, }) if err != nil { return nil, err } return &Validator{ name: method.Name, config: &config, saGetter: client.CoreV1(), trGetter: client.AuthenticationV1(), }, nil } func (v *Validator) Name() string { return v.name } func (v *Validator) Stop() {} func (v *Validator) ValidateLogin(ctx context.Context, loginToken string) (*authmethod.Identity, error) { if _, err := jwt.ParseSigned(loginToken); err != nil { return nil, fmt.Errorf("failed to parse and validate JWT: %v", err) } // Check TokenReview for the bulk of the work. trResp, err := v.trGetter.TokenReviews().Create(ctx, &authv1.TokenReview{ Spec: authv1.TokenReviewSpec{ Token: loginToken, }, }, client_metav1.CreateOptions{}) if err != nil { return nil, err } else if trResp.Status.Error != "" { return nil, fmt.Errorf("lookup failed: %s", trResp.Status.Error) } if !trResp.Status.Authenticated { return nil, errors.New("lookup failed: service account jwt not valid") } // The username is of format: system:serviceaccount:(NAMESPACE):(SERVICEACCOUNT) parts := strings.Split(trResp.Status.User.Username, ":") if len(parts) != 4 { return nil, errors.New("lookup failed: unexpected username format") } // Validate the user that comes back from token review is a service account if parts[0] != "system" || parts[1] != "serviceaccount" { return nil, errors.New("lookup failed: username returned is not a service account") } var ( saNamespace = parts[2] saName = parts[3] saUID = trResp.Status.User.UID ) // Check to see if there is an override name on the ServiceAccount object. sa, err := v.saGetter.ServiceAccounts(saNamespace).Get(ctx, saName, client_metav1.GetOptions{}) if err != nil { return nil, fmt.Errorf("annotation lookup failed: %v", err) } annotations := sa.GetObjectMeta().GetAnnotations() if serviceNameOverride, ok := annotations[serviceAccountServiceNameAnnotation]; ok { saName = serviceNameOverride } fields := map[string]string{ serviceAccountNamespaceField: saNamespace, serviceAccountNameField: saName, serviceAccountUIDField: saUID, } id := v.NewIdentity() id.SelectableFields = &k8sFieldDetails{ ServiceAccount: k8sFieldDetailsServiceAccount{ Namespace: fields[serviceAccountNamespaceField], Name: fields[serviceAccountNameField], UID: fields[serviceAccountUIDField], }, } for k, val := range fields { id.ProjectedVars[k] = val } id.EnterpriseMeta = v.k8sEntMetaFromFields(fields) return id, nil } func (v *Validator) NewIdentity() *authmethod.Identity { id := &authmethod.Identity{ SelectableFields: &k8sFieldDetails{}, ProjectedVars: map[string]string{}, } for _, f := range availableFields { id.ProjectedVars[f] = "" } return id } var availableFields = []string{ serviceAccountNamespaceField, serviceAccountNameField, serviceAccountUIDField, } type k8sFieldDetails struct { ServiceAccount k8sFieldDetailsServiceAccount `bexpr:"serviceaccount"` } type k8sFieldDetailsServiceAccount struct { Namespace string `bexpr:"namespace"` Name string `bexpr:"name"` UID string `bexpr:"uid"` }