open-consul/agent/consul/authmethod/kubeauth/k8s.go

228 lines
6.4 KiB
Go

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"`
}