package provisioner import ( "context" "crypto/ecdsa" "crypto/rsa" "crypto/x509" "encoding/pem" "github.com/pkg/errors" "github.com/smallstep/cli/crypto/pemutil" "github.com/smallstep/cli/jose" "golang.org/x/crypto/ed25519" ) // NOTE: There can be at most one kubernetes service account provisioner configured // per instance of step-ca. This is due to a lack of distinguishing information // contained in kubernetes service account tokens. const ( // K8sSAName is the default name used for kubernetes service account provisioners. K8sSAName = "k8sSA-default" // K8sSAID is the default ID for kubernetes service account provisioners. K8sSAID = "k8ssa/" + K8sSAName k8sSAIssuer = "kubernetes/serviceaccount" ) // This number must <= 1. We'll verify this in Init() below. var numK8sSAProvisioners = 0 // jwtPayload extends jwt.Claims with step attributes. type k8sSAPayload struct { jose.Claims Namespace string `json:"kubernetes.io/serviceaccount/namespace,omitempty"` SecretName string `json:"kubernetes.io/serviceaccount/secret.name,omitempty"` ServiceAccountName string `json:"kubernetes.io/serviceaccount/service-account.name,omitempty"` ServiceAccountUID string `json:"kubernetes.io/serviceaccount/service-account.uid,omitempty"` } // K8sSA represents a Kubernetes ServiceAccount provisioner; an // entity trusted to make signature requests. type K8sSA struct { Type string `json:"type"` Name string `json:"name"` Claims *Claims `json:"claims,omitempty"` PubKeys []byte `json:"publicKeys,omitempty"` claimer *Claimer audiences Audiences //kauthn kauthn.AuthenticationV1Interface pubKeys []interface{} } // GetID returns the provisioner unique identifier. The name and credential id // should uniquely identify any K8sSA provisioner. func (p *K8sSA) GetID() string { return K8sSAID } // GetTokenID returns an unimplemented error and does not use the input ott. func (p *K8sSA) GetTokenID(ott string) (string, error) { return "", errors.New("not implemented") } // GetName returns the name of the provisioner. func (p *K8sSA) GetName() string { return p.Name } // GetType returns the type of provisioner. func (p *K8sSA) GetType() Type { return TypeK8sSA } // GetEncryptedKey returns false, because the kubernetes provisioner does not // have access to the private key. func (p *K8sSA) GetEncryptedKey() (string, string, bool) { return "", "", false } // Init initializes and validates the fields of a K8sSA type. func (p *K8sSA) Init(config Config) (err error) { switch { case p.Type == "": return errors.New("provisioner type cannot be empty") case p.Name == "": return errors.New("provisioner name cannot be empty") case numK8sSAProvisioners >= 1: return errors.New("cannot have more than one kubernetes service account provisioner") } if p.PubKeys != nil { var ( block *pem.Block rest = p.PubKeys ) for rest != nil { block, rest = pem.Decode(rest) if block == nil { break } key, err := pemutil.ParseKey(pem.EncodeToMemory(block)) if err != nil { return errors.Wrapf(err, "error parsing public key in provisioner %s", p.GetID()) } switch q := key.(type) { case *rsa.PublicKey, *ecdsa.PublicKey, ed25519.PublicKey: default: return errors.Errorf("Unexpected public key type %T in provisioner %s", q, p.GetID()) } p.pubKeys = append(p.pubKeys, key) } } else { // TODO: Use the TokenReview API if no pub keys provided. This will need to // be configured with additional attributes in the K8sSA struct for // connecting to the kubernetes API server. return errors.New("K8s Service Account provisioner cannot be initialized without pub keys") } /* // NOTE: Not sure if we should be doing this initialization here ... // If you have a k8sSA provisioner defined in your config, but you're not // in a kubernetes pod then your CA will fail to startup. Maybe we just postpone // creating the authn until token validation time? if err := checkAccess(k8s.AuthorizationV1()); err != nil { return errors.Wrapf(err, "error verifying access to kubernetes authz service for provisioner %s", p.GetID()) } p.kauthn = k8s.AuthenticationV1() */ // Update claims with global ones if p.claimer, err = NewClaimer(p.Claims, config.Claims); err != nil { return err } p.audiences = config.Audiences numK8sSAProvisioners++ return err } // authorizeToken performs common jwt authorization actions and returns the // claims for case specific downstream parsing. // e.g. a Sign request will auth/validate different fields than a Revoke request. func (p *K8sSA) authorizeToken(token string, audiences []string) (*k8sSAPayload, error) { jwt, err := jose.ParseSigned(token) if err != nil { return nil, errors.Wrapf(err, "error parsing token") } var ( valid bool claims k8sSAPayload ) if p.pubKeys == nil { return nil, errors.New("TokenReview API integration not implemented") /* NOTE: We plan to support the TokenReview API in a future release. Below is some code that should be useful when we prioritize this integration. tr := kauthnApi.TokenReview{Spec: kauthnApi.TokenReviewSpec{Token: string(token)}} rvw, err := p.kauthn.TokenReviews().Create(&tr) if err != nil { return nil, errors.Wrap(err, "error using kubernetes TokenReview API") } if rvw.Status.Error != "" { return nil, errors.Errorf("error from kubernetes TokenReviewAPI: %s", rvw.Status.Error) } if !rvw.Status.Authenticated { return nil, errors.New("error from kubernetes TokenReviewAPI: token could not be authenticated") } if err = jwt.UnsafeClaimsWithoutVerification(&claims); err != nil { return nil, errors.Wrap(err, "error parsing claims") } */ } for _, pk := range p.pubKeys { if err = jwt.Claims(pk, &claims); err == nil { valid = true break } } if !valid { return nil, errors.New("error validating token and extracting claims") } // According to "rfc7519 JSON Web Token" acceptable skew should be no // more than a few minutes. if err = claims.Validate(jose.Expected{ Issuer: k8sSAIssuer, }); err != nil { return nil, errors.Wrapf(err, "invalid token claims") } if claims.Subject == "" { return nil, errors.New("token subject cannot be empty") } return &claims, nil } // AuthorizeRevoke returns an error if the provisioner does not have rights to // revoke the certificate with serial number in the `sub` property. func (p *K8sSA) AuthorizeRevoke(token string) error { _, err := p.authorizeToken(token, p.audiences.Revoke) return err } // AuthorizeSign validates the given token. func (p *K8sSA) AuthorizeSign(ctx context.Context, token string) ([]SignOption, error) { _, err := p.authorizeToken(token, p.audiences.Sign) if err != nil { return nil, err } // Check for SSH sign-ing request. if MethodFromContext(ctx) == SignSSHMethod { return nil, errors.New("ssh certificates not enabled for k8s ServiceAccount provisioners") } return []SignOption{ // modifiers / withOptions newProvisionerExtensionOption(TypeK8sSA, p.Name, ""), profileDefaultDuration(p.claimer.DefaultTLSCertDuration()), // validators defaultPublicKeyValidator{}, newValidityValidator(p.claimer.MinTLSCertDuration(), p.claimer.MaxTLSCertDuration()), }, nil } // AuthorizeRenewal returns an error if the renewal is disabled. func (p *K8sSA) AuthorizeRenewal(cert *x509.Certificate) error { if p.claimer.IsDisableRenewal() { return errors.Errorf("renew is disabled for provisioner %s", p.GetID()) } return nil } /* func checkAccess(authz kauthz.AuthorizationV1Interface) error { r := &kauthzApi.SelfSubjectAccessReview{ Spec: kauthzApi.SelfSubjectAccessReviewSpec{ ResourceAttributes: &kauthzApi.ResourceAttributes{ Group: "authentication.k8s.io", Version: "v1", Resource: "tokenreviews", Verb: "create", }, }, } rvw, err := authz.SelfSubjectAccessReviews().Create(r) if err != nil { return err } if !rvw.Status.Allowed { return fmt.Errorf("Unable to create kubernetes token reviews: %s", rvw.Status.Reason) } return nil } */