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auth.go
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auth.go
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package api
import (
"crypto/ed25519"
"errors"
"fmt"
"net/http"
"strings"
"github.com/go-logr/logr"
"github.com/golang-jwt/jwt/v5"
"github.com/rancher-sandbox/cluster-api-provider-elemental/api/v1beta1"
corev1 "k8s.io/api/core/v1"
"k8s.io/apimachinery/pkg/types"
"sigs.k8s.io/controller-runtime/pkg/client"
)
var (
ErrUnauthorized = errors.New("unauthorized")
ErrForbidden = errors.New("forbidden")
ErrMissingRegistrationSecret = errors.New("registration secret is missing")
ErrNoSigningKey = errors.New("registration signing key is missing")
ErrUnparsableSigningKey = errors.New("registration signing key is not in the expected format")
)
type Authenticator interface {
ValidateHostRequest(*http.Request, http.ResponseWriter, *v1beta1.ElementalHost, *v1beta1.ElementalRegistration) error
ValidateRegistrationRequest(*http.Request, http.ResponseWriter, *v1beta1.ElementalRegistration) error
}
func NewAuthenticator(k8sClient client.Client, logger logr.Logger) Authenticator {
return &authenticator{
k8sClient: k8sClient,
logger: logger,
}
}
var _ Authenticator = (*authenticator)(nil)
type authenticator struct {
logger logr.Logger
k8sClient client.Client
}
func (a *authenticator) ValidateHostRequest(request *http.Request, response http.ResponseWriter, host *v1beta1.ElementalHost, registration *v1beta1.ElementalRegistration) error {
// Verify token was passed correctly
authValue := request.Header.Get("Authorization")
if len(authValue) == 0 {
err := fmt.Errorf("missing 'Authorization' header: %w", ErrUnauthorized)
a.writeResponse(response, err)
return err
}
token, found := strings.CutPrefix(authValue, "Bearer ")
if !found {
err := fmt.Errorf("not a 'Bearer' token: %w", ErrUnauthorized)
a.writeResponse(response, err)
return err
}
// Validate and Verify JWT
expectedClaims := &jwt.RegisteredClaims{
Subject: host.Name,
Audience: []string{registration.Spec.Config.Elemental.Registration.URI},
}
_, err := jwt.ParseWithClaims(token, expectedClaims, func(parsedToken *jwt.Token) (any, error) {
signingAlg := parsedToken.Method.Alg()
switch signingAlg {
case "EdDSA":
pubKey, err := jwt.ParseEdPublicKeyFromPEM([]byte(host.Spec.PubKey))
if err != nil {
return nil, fmt.Errorf("parsing host Public Key: %w", err)
}
return pubKey, nil
default:
return nil, fmt.Errorf("JWT is using unsupported '%s' signing algorithm: %w", signingAlg, ErrUnauthorized)
}
})
if err != nil {
err := fmt.Errorf("validating JWT token: %w: %w", err, ErrForbidden)
a.writeResponse(response, err)
return err
}
return nil
}
func (a *authenticator) ValidateRegistrationRequest(request *http.Request, response http.ResponseWriter, registration *v1beta1.ElementalRegistration) error {
// Verify token was passed correctly
authValue := request.Header.Get("Registration-Authorization")
if len(authValue) == 0 {
err := fmt.Errorf("missing 'Registration-Authorization' header: %w", ErrUnauthorized)
a.writeResponse(response, err)
return err
}
token, found := strings.CutPrefix(authValue, "Bearer ")
if !found {
err := fmt.Errorf("not a 'Bearer' token: %w", ErrUnauthorized)
a.writeResponse(response, err)
return err
}
// Fetch registration secret and read the private key
registrationSecret := &corev1.Secret{}
if err := a.k8sClient.Get(request.Context(), types.NamespacedName{
Name: registration.Name,
Namespace: registration.Namespace,
}, registrationSecret); err != nil {
err := fmt.Errorf("getting registration secret: %w", ErrMissingRegistrationSecret)
a.writeResponse(response, err)
return err
}
privKeyPem, found := registrationSecret.Data["privKey"]
if !found {
a.writeResponse(response, ErrNoSigningKey)
return ErrNoSigningKey
}
parsedKey, err := jwt.ParseEdPrivateKeyFromPEM(privKeyPem)
if err != nil {
err := fmt.Errorf("parsing ed25519 key: %w", err)
a.writeResponse(response, err)
return err
}
var privKey ed25519.PrivateKey
var ok bool
if privKey, ok = parsedKey.(ed25519.PrivateKey); !ok {
a.writeResponse(response, jwt.ErrNotEdPrivateKey)
return jwt.ErrNotEdPrivateKey
}
// Validate and Verify JWT
expectedClaims := &jwt.RegisteredClaims{
Subject: registration.Spec.Config.Elemental.Registration.URI,
Audience: []string{registration.Spec.Config.Elemental.Registration.URI},
}
_, err = jwt.ParseWithClaims(token, expectedClaims, func(parsedToken *jwt.Token) (any, error) {
signingAlg := parsedToken.Method.Alg()
switch signingAlg {
case "EdDSA":
return privKey.Public(), nil
default:
return nil, fmt.Errorf("JWT is using unsupported '%s' signing algorithm: %w", signingAlg, ErrUnauthorized)
}
})
if err != nil {
err := fmt.Errorf("validating JWT token: %w: %w", err, ErrForbidden)
a.writeResponse(response, err)
return err
}
return nil
}
func (a *authenticator) writeResponse(response http.ResponseWriter, err error) {
if errors.Is(err, ErrUnauthorized) {
response.WriteHeader(http.StatusUnauthorized)
WriteResponse(a.logger, response, fmt.Sprintf("Unauthorized: %s", err.Error()))
return
}
if errors.Is(err, ErrForbidden) {
response.WriteHeader(http.StatusForbidden)
WriteResponse(a.logger, response, fmt.Sprintf("Forbidden: %s", err.Error()))
return
}
response.WriteHeader(http.StatusInternalServerError)
WriteResponse(a.logger, response, fmt.Sprintf("Could not authenticate request: %s", err.Error()))
}