Merge pull request #510 from smallstep/ra-mode

StepCAS.

authority/config.go

@@ -189,7 +189,6 @@ func (c *Config) Validate() error {
 
 	// Options holds the RA/CAS configuration.
 	ra := c.AuthorityConfig.Options
-
 	// The default RA/CAS requires root, crt and key.
 	if ra.Is(cas.SoftCAS) {
 		switch {

authority/tls.go

@@ -148,6 +148,7 @@ func (a *Authority) Sign(csr *x509.CertificateRequest, signOpts provisioner.Sign
 	lifetime := leaf.NotAfter.Sub(leaf.NotBefore.Add(signOpts.Backdate))
 	resp, err := a.x509CAService.CreateCertificate(&casapi.CreateCertificateRequest{
 		Template: leaf,
+		CSR:      csr,
 		Lifetime: lifetime,
 		Backdate: signOpts.Backdate,
 	})
@@ -333,22 +334,21 @@ func (a *Authority) Revoke(ctx context.Context, revokeOpts *RevokeOptions) error
 		if !ok {
 			return errs.InternalServer("authority.Revoke; provisioner not found", opts...)
 		}
+		rci.ProvisionerID = p.GetID()
 		rci.TokenID, err = p.GetTokenID(revokeOpts.OTT)
 		if err != nil {
 			return errs.Wrap(http.StatusInternalServerError, err,
 				"authority.Revoke; could not get ID for token")
 		}
+		opts = append(opts, errs.WithKeyVal("provisionerID", rci.ProvisionerID))
 		opts = append(opts, errs.WithKeyVal("tokenID", rci.TokenID))
 	} else {
 		// Load the Certificate provisioner if one exists.
-		p, err = a.LoadProvisionerByCertificate(revokeOpts.Crt)
+		if p, err = a.LoadProvisionerByCertificate(revokeOpts.Crt); err == nil {
-		if err != nil {
+			rci.ProvisionerID = p.GetID()
-			return errs.Wrap(http.StatusUnauthorized, err,
+			opts = append(opts, errs.WithKeyVal("provisionerID", rci.ProvisionerID))
-				"authority.Revoke: unable to load certificate provisioner", opts...)
 		}
 	}
-	rci.ProvisionerID = p.GetID()
-	opts = append(opts, errs.WithKeyVal("provisionerID", rci.ProvisionerID))
 
 	if provisioner.MethodFromContext(ctx) == provisioner.SSHRevokeMethod {
 		err = a.db.RevokeSSH(rci)
@@ -367,9 +367,11 @@ func (a *Authority) Revoke(ctx context.Context, revokeOpts *RevokeOptions) error
 		// CAS operation, note that SoftCAS (default) is a noop.
 		// The revoke happens when this is stored in the db.
 		_, err = a.x509CAService.RevokeCertificate(&casapi.RevokeCertificateRequest{
-			Certificate: revokedCert,
+			Certificate:  revokedCert,
-			Reason:      rci.Reason,
+			SerialNumber: rci.Serial,
-			ReasonCode:  rci.ReasonCode,
+			Reason:       rci.Reason,
+			ReasonCode:   rci.ReasonCode,
+			PassiveOnly:  revokeOpts.PassiveOnly,
 		})
 		if err != nil {
 			return errs.Wrap(http.StatusInternalServerError, err, "authority.Revoke", opts...)
@@ -427,6 +429,7 @@ func (a *Authority) GetTLSCertificate() (*tls.Certificate, error) {
 
 	resp, err := a.x509CAService.CreateCertificate(&casapi.CreateCertificateRequest{
 		Template: certTpl,
+		CSR:      cr,
 		Lifetime: 24 * time.Hour,
 		Backdate: 1 * time.Minute,
 	})

authority/tls_test.go

@@ -1231,6 +1231,30 @@ func TestAuthority_Revoke(t *testing.T) {
 			crt, err := pemutil.ReadCertificate("./testdata/certs/foo.crt")
 			assert.FatalError(t, err)
 
+			return test{
+				auth: _a,
+				opts: &RevokeOptions{
+					Crt:        crt,
+					Serial:     "102012593071130646873265215610956555026",
+					ReasonCode: reasonCode,
+					Reason:     reason,
+					MTLS:       true,
+				},
+			}
+		},
+		"ok/mTLS-no-provisioner": func() test {
+			_a := testAuthority(t, WithDatabase(&db.MockAuthDB{}))
+
+			crt, err := pemutil.ReadCertificate("./testdata/certs/foo.crt")
+			assert.FatalError(t, err)
+			// Filter out provisioner extension.
+			for i, ext := range crt.Extensions {
+				if ext.Id.Equal(asn1.ObjectIdentifier{1, 3, 6, 1, 4, 1, 37476, 9000, 64, 1}) {
+					crt.Extensions = append(crt.Extensions[:i], crt.Extensions[i+1:]...)
+					break
+				}
+			}
+
 			return test{
 				auth: _a,
 				opts: &RevokeOptions{

cas/apiv1/options.go

@@ -14,17 +14,29 @@ type Options struct {
 	// The type of the CAS to use.
 	Type string `json:"type"`
 
-	// Path to the credentials file used in CloudCAS
+	// CertificateAuthority reference:
-	CredentialsFile string `json:"credentialsFile"`
+	// In StepCAS the value is the CA url, e.g. "https://ca.smallstep.com:9000".
+	// In CloudCAS the format is "projects/*/locations/*/certificateAuthorities/*".
+	CertificateAuthority string `json:"certificateAuthority,omitempty"`
 
-	// CertificateAuthority reference. In CloudCAS the format is
+	// CertificateAuthorityFingerprint is the root fingerprint used to
-	// `projects/*/locations/*/certificateAuthorities/*`.
+	// authenticate the connection to the CA when using StepCAS.
-	CertificateAuthority string `json:"certificateAuthority"`
+	CertificateAuthorityFingerprint string `json:"certificateAuthorityFingerprint,omitempty"`
 
-	// Certificate and signer are the issuer certificate,along with any other bundled certificates to be returned in the chain for consumers, and signer used in SoftCAS.
+	// CertificateIssuer contains the configuration used in StepCAS.
-	// They are configured in ca.json crt and key properties.
+	CertificateIssuer *CertificateIssuer `json:"certificateIssuer,omitempty"`
-	CertificateChain []*x509.Certificate
+
-	Signer           crypto.Signer `json:"-"`
+	// Path to the credentials file used in CloudCAS. If not defined the default
+	// authentication mechanism provided by Google SDK will be used. See
+	// https://cloud.google.com/docs/authentication.
+	CredentialsFile string `json:"credentialsFile,omitempty"`
+
+	// Certificate and signer are the issuer certificate, along with any other
+	// bundled certificates to be returned in the chain for consumers, and
+	// signer used in SoftCAS. They are configured in ca.json crt and key
+	// properties.
+	CertificateChain []*x509.Certificate `json:"-"`
+	Signer           crypto.Signer       `json:"-"`
 
 	// IsCreator is set to true when we're creating a certificate authority. Is
 	// used to skip some validations when initializing a CertificateAuthority.
@@ -39,6 +51,16 @@ type Options struct {
 	Location string `json:"-"`
 }
 
+// CertificateIssuer contains the properties used to use the StepCAS certificate
+// authority service.
+type CertificateIssuer struct {
+	Type        string `json:"type"`
+	Provisioner string `json:"provisioner,omitempty"`
+	Certificate string `json:"crt,omitempty"`
+	Key         string `json:"key,omitempty"`
+	Password    string `json:"password,omitempty"`
+}
+
 // Validate checks the fields in Options.
 func (o *Options) Validate() error {
 	var typ Type

cas/apiv1/requests.go

@@ -53,6 +53,7 @@ const (
 // CreateCertificateRequest is the request used to sign a new certificate.
 type CreateCertificateRequest struct {
 	Template  *x509.Certificate
+	CSR       *x509.CertificateRequest
 	Lifetime  time.Duration
 	Backdate  time.Duration
 	RequestID string
@@ -67,6 +68,7 @@ type CreateCertificateResponse struct {
 // RenewCertificateRequest is the request used to re-sign a certificate.
 type RenewCertificateRequest struct {
 	Template  *x509.Certificate
+	CSR       *x509.CertificateRequest
 	Lifetime  time.Duration
 	Backdate  time.Duration
 	RequestID string
@@ -80,10 +82,12 @@ type RenewCertificateResponse struct {
 
 // RevokeCertificateRequest is the request used to revoke a certificate.
 type RevokeCertificateRequest struct {
-	Certificate *x509.Certificate
+	Certificate  *x509.Certificate
-	Reason      string
+	SerialNumber string
-	ReasonCode  int
+	Reason       string
-	RequestID   string
+	ReasonCode   int
+	PassiveOnly  bool
+	RequestID    string
 }
 
 // RevokeCertificateResponse is the response to a revoke certificate request.

cas/apiv1/services.go

@@ -1,6 +1,7 @@
 package apiv1
 
 import (
+	"net/http"
 	"strings"
 )
 
@@ -35,6 +36,8 @@ const (
 	SoftCAS = "softcas"
 	// CloudCAS is a CertificateAuthorityService using Google Cloud CAS.
 	CloudCAS = "cloudcas"
+	// StepCAS is a CertificateAuthorityService using another step-ca instance.
+	StepCAS = "stepcas"
 )
 
 // String returns a string from the type. It will always return the lower case
@@ -46,3 +49,23 @@ func (t Type) String() string {
 	}
 	return strings.ToLower(string(t))
 }
+
+// ErrNotImplemented is the type of error returned if an operation is not
+// implemented.
+type ErrNotImplemented struct {
+	Message string
+}
+
+// ErrNotImplemented implements the error interface.
+func (e ErrNotImplemented) Error() string {
+	if e.Message != "" {
+		return e.Message
+	}
+	return "not implemented"
+}
+
+// StatusCode implements the StatusCoder interface and returns the HTTP 501
+// error.
+func (e ErrNotImplemented) StatusCode() int {
+	return http.StatusNotImplemented
+}

cas/apiv1/services_test.go

@@ -1,6 +1,8 @@
 package apiv1
 
-import "testing"
+import (
+	"testing"
+)
 
 func TestType_String(t *testing.T) {
 	tests := []struct {
@@ -21,3 +23,51 @@ func TestType_String(t *testing.T) {
 		})
 	}
 }
+
+func TestErrNotImplemented_Error(t *testing.T) {
+	type fields struct {
+		Message string
+	}
+	tests := []struct {
+		name   string
+		fields fields
+		want   string
+	}{
+		{"default", fields{""}, "not implemented"},
+		{"with message", fields{"method not supported"}, "method not supported"},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			e := ErrNotImplemented{
+				Message: tt.fields.Message,
+			}
+			if got := e.Error(); got != tt.want {
+				t.Errorf("ErrNotImplemented.Error() = %v, want %v", got, tt.want)
+			}
+		})
+	}
+}
+
+func TestErrNotImplemented_StatusCode(t *testing.T) {
+	type fields struct {
+		Message string
+	}
+	tests := []struct {
+		name   string
+		fields fields
+		want   int
+	}{
+		{"default", fields{""}, 501},
+		{"with message", fields{"method not supported"}, 501},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			s := ErrNotImplemented{
+				Message: tt.fields.Message,
+			}
+			if got := s.StatusCode(); got != tt.want {
+				t.Errorf("ErrNotImplemented.StatusCode() = %v, want %v", got, tt.want)
+			}
+		})
+	}
+}

cas/cloudcas/cloudcas.go

@@ -141,7 +141,6 @@ func (c *CloudCAS) GetCertificateAuthority(req *apiv1.GetCertificateAuthorityReq
 		Name: name,
 	})
 	if err != nil {
-		println(name)
 		return nil, errors.Wrap(err, "cloudCAS GetCertificateAuthority failed")
 	}
 	if len(resp.PemCaCertificates) == 0 {

cas/stepcas/issuer.go

@@ -0,0 +1,78 @@
+package stepcas
+
+import (
+	"net/url"
+	"strings"
+	"time"
+
+	"github.com/pkg/errors"
+	"github.com/smallstep/certificates/cas/apiv1"
+)
+
+type stepIssuer interface {
+	SignToken(subject string, sans []string) (string, error)
+	RevokeToken(subject string) (string, error)
+	Lifetime(d time.Duration) time.Duration
+}
+
+// newStepIssuer returns the configured step issuer.
+func newStepIssuer(caURL *url.URL, iss *apiv1.CertificateIssuer) (stepIssuer, error) {
+	if err := validateCertificateIssuer(iss); err != nil {
+		return nil, err
+	}
+
+	switch strings.ToLower(iss.Type) {
+	case "x5c":
+		return newX5CIssuer(caURL, iss)
+	case "jwk":
+		return newJWKIssuer(caURL, iss)
+	default:
+		return nil, errors.Errorf("stepCAS `certificateIssuer.type` %s is not supported", iss.Type)
+	}
+}
+
+// validateCertificateIssuer validates the configuration of the certificate
+// issuer.
+func validateCertificateIssuer(iss *apiv1.CertificateIssuer) error {
+	switch {
+	case iss == nil:
+		return errors.New("stepCAS 'certificateIssuer' cannot be nil")
+	case iss.Type == "":
+		return errors.New("stepCAS `certificateIssuer.type` cannot be empty")
+	}
+
+	switch strings.ToLower(iss.Type) {
+	case "x5c":
+		return validateX5CIssuer(iss)
+	case "jwk":
+		return validateJWKIssuer(iss)
+	default:
+		return errors.Errorf("stepCAS `certificateIssuer.type` %s is not supported", iss.Type)
+	}
+}
+
+// validateX5CIssuer validates the configuration of x5c issuer.
+func validateX5CIssuer(iss *apiv1.CertificateIssuer) error {
+	switch {
+	case iss.Certificate == "":
+		return errors.New("stepCAS `certificateIssuer.crt` cannot be empty")
+	case iss.Key == "":
+		return errors.New("stepCAS `certificateIssuer.key` cannot be empty")
+	case iss.Provisioner == "":
+		return errors.New("stepCAS `certificateIssuer.provisioner` cannot be empty")
+	default:
+		return nil
+	}
+}
+
+// validateJWKIssuer validates the configuration of jwk issuer.
+func validateJWKIssuer(iss *apiv1.CertificateIssuer) error {
+	switch {
+	case iss.Key == "":
+		return errors.New("stepCAS `certificateIssuer.key` cannot be empty")
+	case iss.Provisioner == "":
+		return errors.New("stepCAS `certificateIssuer.provisioner` cannot be empty")
+	default:
+		return nil
+	}
+}

cas/stepcas/issuer_test.go

@@ -0,0 +1,80 @@
+package stepcas
+
+import (
+	"net/url"
+	"reflect"
+	"testing"
+	"time"
+
+	"github.com/smallstep/certificates/cas/apiv1"
+)
+
+type mockErrIssuer struct{}
+
+func (m mockErrIssuer) SignToken(subject string, sans []string) (string, error) {
+	return "", apiv1.ErrNotImplemented{}
+}
+
+func (m mockErrIssuer) RevokeToken(subject string) (string, error) {
+	return "", apiv1.ErrNotImplemented{}
+}
+
+func (m mockErrIssuer) Lifetime(d time.Duration) time.Duration {
+	return d
+}
+
+func Test_newStepIssuer(t *testing.T) {
+	caURL, err := url.Parse("https://ca.smallstep.com")
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	type args struct {
+		caURL *url.URL
+		iss   *apiv1.CertificateIssuer
+	}
+	tests := []struct {
+		name    string
+		args    args
+		want    stepIssuer
+		wantErr bool
+	}{
+		{"x5c", args{caURL, &apiv1.CertificateIssuer{
+			Type:        "x5c",
+			Provisioner: "X5C",
+			Certificate: testX5CPath,
+			Key:         testX5CKeyPath,
+		}}, &x5cIssuer{
+			caURL:    caURL,
+			certFile: testX5CPath,
+			keyFile:  testX5CKeyPath,
+			issuer:   "X5C",
+		}, false},
+		{"jwk", args{caURL, &apiv1.CertificateIssuer{
+			Type:        "jwk",
+			Provisioner: "ra@doe.org",
+			Key:         testX5CKeyPath,
+		}}, &jwkIssuer{
+			caURL:   caURL,
+			keyFile: testX5CKeyPath,
+			issuer:  "ra@doe.org",
+		}, false},
+		{"fail", args{caURL, &apiv1.CertificateIssuer{
+			Type:        "unknown",
+			Provisioner: "ra@doe.org",
+			Key:         testX5CKeyPath,
+		}}, nil, true},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			got, err := newStepIssuer(tt.args.caURL, tt.args.iss)
+			if (err != nil) != tt.wantErr {
+				t.Errorf("newStepIssuer() error = %v, wantErr %v", err, tt.wantErr)
+				return
+			}
+			if !reflect.DeepEqual(got, tt.want) {
+				t.Errorf("newStepIssuer() = %v, want %v", got, tt.want)
+			}
+		})
+	}
+}

cas/stepcas/jwk_issuer.go

@@ -0,0 +1,92 @@
+package stepcas
+
+import (
+	"net/url"
+	"time"
+
+	"github.com/pkg/errors"
+	"github.com/smallstep/certificates/cas/apiv1"
+	"go.step.sm/crypto/jose"
+	"go.step.sm/crypto/randutil"
+)
+
+type jwkIssuer struct {
+	caURL    *url.URL
+	issuer   string
+	keyFile  string
+	password string
+}
+
+func newJWKIssuer(caURL *url.URL, cfg *apiv1.CertificateIssuer) (*jwkIssuer, error) {
+	_, err := newJWKSigner(cfg.Key, cfg.Password)
+	if err != nil {
+		return nil, err
+	}
+
+	return &jwkIssuer{
+		caURL:    caURL,
+		issuer:   cfg.Provisioner,
+		keyFile:  cfg.Key,
+		password: cfg.Password,
+	}, nil
+}
+
+func (i *jwkIssuer) SignToken(subject string, sans []string) (string, error) {
+	aud := i.caURL.ResolveReference(&url.URL{
+		Path: "/1.0/sign",
+	}).String()
+	return i.createToken(aud, subject, sans)
+}
+
+func (i *jwkIssuer) RevokeToken(subject string) (string, error) {
+	aud := i.caURL.ResolveReference(&url.URL{
+		Path: "/1.0/revoke",
+	}).String()
+	return i.createToken(aud, subject, nil)
+}
+
+func (i *jwkIssuer) Lifetime(d time.Duration) time.Duration {
+	return d
+}
+
+func (i *jwkIssuer) createToken(aud, sub string, sans []string) (string, error) {
+	signer, err := newJWKSigner(i.keyFile, i.password)
+	if err != nil {
+		return "", err
+	}
+
+	id, err := randutil.Hex(64) // 256 bits
+	if err != nil {
+		return "", err
+	}
+
+	claims := defaultClaims(i.issuer, sub, aud, id)
+	builder := jose.Signed(signer).Claims(claims)
+	if len(sans) > 0 {
+		builder = builder.Claims(map[string]interface{}{
+			"sans": sans,
+		})
+	}
+
+	tok, err := builder.CompactSerialize()
+	if err != nil {
+		return "", errors.Wrap(err, "error signing token")
+	}
+
+	return tok, nil
+}
+
+func newJWKSigner(keyFile, password string) (jose.Signer, error) {
+	signer, err := readKey(keyFile, password)
+	if err != nil {
+		return nil, err
+	}
+	kid, err := jose.Thumbprint(&jose.JSONWebKey{Key: signer.Public()})
+	if err != nil {
+		return nil, err
+	}
+	so := new(jose.SignerOptions)
+	so.WithType("JWT")
+	so.WithHeader("kid", kid)
+	return newJoseSigner(signer, so)
+}

cas/stepcas/jwk_issuer_test.go

@@ -0,0 +1,172 @@
+package stepcas
+
+import (
+	"net/url"
+	"reflect"
+	"testing"
+	"time"
+
+	"go.step.sm/crypto/jose"
+)
+
+func Test_jwkIssuer_SignToken(t *testing.T) {
+	caURL, err := url.Parse("https://ca.smallstep.com")
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	type fields struct {
+		caURL   *url.URL
+		keyFile string
+		issuer  string
+	}
+	type args struct {
+		subject string
+		sans    []string
+	}
+	type claims struct {
+		Aud  []string `json:"aud"`
+		Sub  string   `json:"sub"`
+		Sans []string `json:"sans"`
+	}
+	tests := []struct {
+		name    string
+		fields  fields
+		args    args
+		wantErr bool
+	}{
+		{"ok", fields{caURL, testX5CKeyPath, "ra@doe.org"}, args{"doe", []string{"doe.org"}}, false},
+		{"fail key", fields{caURL, "", "ra@doe.org"}, args{"doe", []string{"doe.org"}}, true},
+		{"fail no signer", fields{caURL, testIssPath, "ra@doe.org"}, args{"doe", []string{"doe.org"}}, true},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			i := &jwkIssuer{
+				caURL:   tt.fields.caURL,
+				keyFile: tt.fields.keyFile,
+				issuer:  tt.fields.issuer,
+			}
+			got, err := i.SignToken(tt.args.subject, tt.args.sans)
+			if (err != nil) != tt.wantErr {
+				t.Errorf("jwkIssuer.SignToken() error = %v, wantErr %v", err, tt.wantErr)
+				return
+			}
+			if !tt.wantErr {
+				jwt, err := jose.ParseSigned(got)
+				if err != nil {
+					t.Errorf("jose.ParseSigned() error = %v", err)
+				}
+				var c claims
+				want := claims{
+					Aud:  []string{tt.fields.caURL.String() + "/1.0/sign"},
+					Sub:  tt.args.subject,
+					Sans: tt.args.sans,
+				}
+				if err := jwt.Claims(testX5CKey.Public(), &c); err != nil {
+					t.Errorf("jwt.Claims() error = %v", err)
+				}
+				if !reflect.DeepEqual(c, want) {
+					t.Errorf("jwt.Claims() claims = %#v, want %#v", c, want)
+				}
+			}
+		})
+	}
+}
+
+func Test_jwkIssuer_RevokeToken(t *testing.T) {
+	caURL, err := url.Parse("https://ca.smallstep.com")
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	type fields struct {
+		caURL   *url.URL
+		keyFile string
+		issuer  string
+	}
+	type args struct {
+		subject string
+	}
+	type claims struct {
+		Aud  []string `json:"aud"`
+		Sub  string   `json:"sub"`
+		Sans []string `json:"sans"`
+	}
+	tests := []struct {
+		name    string
+		fields  fields
+		args    args
+		wantErr bool
+	}{
+		{"ok", fields{caURL, testX5CKeyPath, "ra@smallstep.com"}, args{"doe"}, false},
+		{"fail key", fields{caURL, "", "ra@smallstep.com"}, args{"doe"}, true},
+		{"fail no signer", fields{caURL, testIssPath, "ra@smallstep.com"}, args{"doe"}, true},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			i := &jwkIssuer{
+				caURL:   tt.fields.caURL,
+				keyFile: tt.fields.keyFile,
+				issuer:  tt.fields.issuer,
+			}
+			got, err := i.RevokeToken(tt.args.subject)
+			if (err != nil) != tt.wantErr {
+				t.Errorf("jwkIssuer.RevokeToken() error = %v, wantErr %v", err, tt.wantErr)
+				return
+			}
+			if !tt.wantErr {
+				jwt, err := jose.ParseSigned(got)
+				if err != nil {
+					t.Errorf("jose.ParseSigned() error = %v", err)
+				}
+				var c claims
+				want := claims{
+					Aud: []string{tt.fields.caURL.String() + "/1.0/revoke"},
+					Sub: tt.args.subject,
+				}
+				if err := jwt.Claims(testX5CKey.Public(), &c); err != nil {
+					t.Errorf("jwt.Claims() error = %v", err)
+				}
+				if !reflect.DeepEqual(c, want) {
+					t.Errorf("jwt.Claims() claims = %#v, want %#v", c, want)
+				}
+			}
+		})
+	}
+}
+
+func Test_jwkIssuer_Lifetime(t *testing.T) {
+	caURL, err := url.Parse("https://ca.smallstep.com")
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	type fields struct {
+		caURL   *url.URL
+		keyFile string
+		issuer  string
+	}
+	type args struct {
+		d time.Duration
+	}
+	tests := []struct {
+		name   string
+		fields fields
+		args   args
+		want   time.Duration
+	}{
+		{"ok", fields{caURL, testX5CKeyPath, "ra@smallstep.com"}, args{time.Second}, time.Second},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			i := &jwkIssuer{
+				caURL:   tt.fields.caURL,
+				keyFile: tt.fields.keyFile,
+				issuer:  tt.fields.issuer,
+			}
+			if got := i.Lifetime(tt.args.d); got != tt.want {
+				t.Errorf("jwkIssuer.Lifetime() = %v, want %v", got, tt.want)
+			}
+		})
+	}
+}

cas/stepcas/stepcas.go

@@ -0,0 +1,178 @@
+package stepcas
+
+import (
+	"context"
+	"crypto/x509"
+	"net/url"
+	"time"
+
+	"github.com/pkg/errors"
+	"github.com/smallstep/certificates/api"
+	"github.com/smallstep/certificates/ca"
+	"github.com/smallstep/certificates/cas/apiv1"
+)
+
+func init() {
+	apiv1.Register(apiv1.StepCAS, func(ctx context.Context, opts apiv1.Options) (apiv1.CertificateAuthorityService, error) {
+		return New(ctx, opts)
+	})
+}
+
+// StepCAS implements the cas.CertificateAuthorityService interface using
+// another step-ca instance.
+type StepCAS struct {
+	iss         stepIssuer
+	client      *ca.Client
+	fingerprint string
+}
+
+// New creates a new CertificateAuthorityService implementation using another
+// step-ca instance.
+func New(ctx context.Context, opts apiv1.Options) (*StepCAS, error) {
+	switch {
+	case opts.CertificateAuthority == "":
+		return nil, errors.New("stepCAS 'certificateAuthority' cannot be empty")
+	case opts.CertificateAuthorityFingerprint == "":
+		return nil, errors.New("stepCAS 'certificateAuthorityFingerprint' cannot be empty")
+	}
+
+	caURL, err := url.Parse(opts.CertificateAuthority)
+	if err != nil {
+		return nil, errors.Wrap(err, "stepCAS `certificateAuthority` is not valid")
+	}
+
+	// Create configured issuer
+	iss, err := newStepIssuer(caURL, opts.CertificateIssuer)
+	if err != nil {
+		return nil, err
+	}
+
+	// Create client.
+	client, err := ca.NewClient(opts.CertificateAuthority, ca.WithRootSHA256(opts.CertificateAuthorityFingerprint))
+	if err != nil {
+		return nil, err
+	}
+
+	return &StepCAS{
+		iss:         iss,
+		client:      client,
+		fingerprint: opts.CertificateAuthorityFingerprint,
+	}, nil
+}
+
+// CreateCertificate uses the step-ca sign request with the configured
+// provisioner to get a new certificate from the certificate authority.
+func (s *StepCAS) CreateCertificate(req *apiv1.CreateCertificateRequest) (*apiv1.CreateCertificateResponse, error) {
+	switch {
+	case req.CSR == nil:
+		return nil, errors.New("createCertificateRequest `csr` cannot be nil")
+	case req.Lifetime == 0:
+		return nil, errors.New("createCertificateRequest `lifetime` cannot be 0")
+	}
+
+	cert, chain, err := s.createCertificate(req.CSR, req.Lifetime)
+	if err != nil {
+		return nil, err
+	}
+
+	return &apiv1.CreateCertificateResponse{
+		Certificate:      cert,
+		CertificateChain: chain,
+	}, nil
+}
+
+// RenewCertificate will always return a non-implemented error as mTLS renewals
+// are not supported yet.
+func (s *StepCAS) RenewCertificate(req *apiv1.RenewCertificateRequest) (*apiv1.RenewCertificateResponse, error) {
+	return nil, apiv1.ErrNotImplemented{Message: "stepCAS does not support mTLS renewals"}
+}
+
+func (s *StepCAS) RevokeCertificate(req *apiv1.RevokeCertificateRequest) (*apiv1.RevokeCertificateResponse, error) {
+	switch {
+	case req.SerialNumber == "" && req.Certificate == nil:
+		return nil, errors.New("revokeCertificateRequest `serialNumber` or `certificate` are required")
+	}
+
+	serialNumber := req.SerialNumber
+	if req.Certificate != nil {
+		serialNumber = req.Certificate.SerialNumber.String()
+	}
+
+	token, err := s.iss.RevokeToken(serialNumber)
+	if err != nil {
+		return nil, err
+	}
+
+	_, err = s.client.Revoke(&api.RevokeRequest{
+		Serial:     serialNumber,
+		ReasonCode: req.ReasonCode,
+		Reason:     req.Reason,
+		OTT:        token,
+		Passive:    req.PassiveOnly,
+	}, nil)
+	if err != nil {
+		return nil, err
+	}
+
+	return &apiv1.RevokeCertificateResponse{
+		Certificate:      req.Certificate,
+		CertificateChain: nil,
+	}, nil
+}
+
+// GetCertificateAuthority returns the root certificate of the certificate
+// authority using the configured fingerprint.
+func (s *StepCAS) GetCertificateAuthority(req *apiv1.GetCertificateAuthorityRequest) (*apiv1.GetCertificateAuthorityResponse, error) {
+	resp, err := s.client.Root(s.fingerprint)
+	if err != nil {
+		return nil, err
+	}
+	return &apiv1.GetCertificateAuthorityResponse{
+		RootCertificate: resp.RootPEM.Certificate,
+	}, nil
+}
+
+func (s *StepCAS) createCertificate(cr *x509.CertificateRequest, lifetime time.Duration) (*x509.Certificate, []*x509.Certificate, error) {
+	sans := make([]string, 0, len(cr.DNSNames)+len(cr.EmailAddresses)+len(cr.IPAddresses)+len(cr.URIs))
+	sans = append(sans, cr.DNSNames...)
+	sans = append(sans, cr.EmailAddresses...)
+	for _, ip := range cr.IPAddresses {
+		sans = append(sans, ip.String())
+	}
+	for _, u := range cr.URIs {
+		sans = append(sans, u.String())
+	}
+
+	commonName := cr.Subject.CommonName
+	if commonName == "" && len(sans) > 0 {
+		commonName = sans[0]
+	}
+
+	token, err := s.iss.SignToken(commonName, sans)
+	if err != nil {
+		return nil, nil, err
+	}
+
+	resp, err := s.client.Sign(&api.SignRequest{
+		CsrPEM:   api.CertificateRequest{CertificateRequest: cr},
+		OTT:      token,
+		NotAfter: s.lifetime(lifetime),
+	})
+	if err != nil {
+		return nil, nil, err
+	}
+
+	var chain []*x509.Certificate
+	cert := resp.CertChainPEM[0].Certificate
+	for _, c := range resp.CertChainPEM[1:] {
+		chain = append(chain, c.Certificate)
+	}
+
+	return cert, chain, nil
+}
+
+func (s *StepCAS) lifetime(d time.Duration) api.TimeDuration {
+	var td api.TimeDuration
+	td.SetDuration(s.iss.Lifetime(d))
+	return td
+}

cas/stepcas/stepcas_test.go

@@ -0,0 +1,807 @@
+package stepcas
+
+import (
+	"bytes"
+	"context"
+	"crypto"
+	"crypto/ed25519"
+	"crypto/rand"
+	"crypto/x509"
+	"encoding/json"
+	"encoding/pem"
+	"fmt"
+	"io/ioutil"
+	"net/http"
+	"net/http/httptest"
+	"net/url"
+	"os"
+	"path/filepath"
+	"reflect"
+	"testing"
+	"time"
+
+	"github.com/smallstep/certificates/api"
+	"github.com/smallstep/certificates/ca"
+	"github.com/smallstep/certificates/cas/apiv1"
+	"go.step.sm/crypto/pemutil"
+	"go.step.sm/crypto/randutil"
+	"go.step.sm/crypto/x509util"
+)
+
+var (
+	testRootCrt                   *x509.Certificate
+	testRootKey                   crypto.Signer
+	testRootPath, testRootKeyPath string
+	testRootFingerprint           string
+
+	testIssCrt                  *x509.Certificate
+	testIssKey                  crypto.Signer
+	testIssPath, testIssKeyPath string
+
+	testX5CCrt                         *x509.Certificate
+	testX5CKey                         crypto.Signer
+	testX5CPath, testX5CKeyPath        string
+	testPassword, testEncryptedKeyPath string
+
+	testCR     *x509.CertificateRequest
+	testCrt    *x509.Certificate
+	testKey    crypto.Signer
+	testFailCR *x509.CertificateRequest
+)
+
+func mustSignCertificate(subject string, sans []string, template string, parent *x509.Certificate, signer crypto.Signer) (*x509.Certificate, crypto.Signer) {
+	pub, priv, err := ed25519.GenerateKey(rand.Reader)
+	if err != nil {
+		panic(err)
+	}
+	cr, err := x509util.CreateCertificateRequest(subject, sans, priv)
+	if err != nil {
+		panic(err)
+	}
+	cert, err := x509util.NewCertificate(cr, x509util.WithTemplate(template, x509util.CreateTemplateData(subject, sans)))
+	if err != nil {
+		panic(err)
+	}
+
+	crt := cert.GetCertificate()
+	crt.NotBefore = time.Now()
+	crt.NotAfter = crt.NotBefore.Add(time.Hour)
+	if parent == nil {
+		parent = crt
+	}
+	if signer == nil {
+		signer = priv
+	}
+	if crt, err = x509util.CreateCertificate(crt, parent, pub, signer); err != nil {
+		panic(err)
+	}
+	return crt, priv
+}
+
+func mustSerializeCrt(filename string, certs ...*x509.Certificate) {
+	buf := new(bytes.Buffer)
+	for _, c := range certs {
+		if err := pem.Encode(buf, &pem.Block{
+			Type:  "CERTIFICATE",
+			Bytes: c.Raw,
+		}); err != nil {
+			panic(err)
+		}
+	}
+	if err := ioutil.WriteFile(filename, buf.Bytes(), 0600); err != nil {
+		panic(err)
+	}
+}
+
+func mustSerializeKey(filename string, key crypto.Signer) {
+	b, err := x509.MarshalPKCS8PrivateKey(key)
+	if err != nil {
+		panic(err)
+	}
+	b = pem.EncodeToMemory(&pem.Block{
+		Type:  "PRIVATE KEY",
+		Bytes: b,
+	})
+	if err := ioutil.WriteFile(filename, b, 0600); err != nil {
+		panic(err)
+	}
+}
+
+func mustEncryptKey(filename string, key crypto.Signer) {
+	_, err := pemutil.Serialize(key,
+		pemutil.ToFile(filename, 0600),
+		pemutil.WithPKCS8(true),
+		pemutil.WithPassword([]byte(testPassword)))
+	if err != nil {
+		panic(err)
+	}
+}
+
+func testCAHelper(t *testing.T) (*url.URL, *ca.Client) {
+	t.Helper()
+
+	writeJSON := func(w http.ResponseWriter, v interface{}) {
+		_ = json.NewEncoder(w).Encode(v)
+	}
+	parseJSON := func(r *http.Request, v interface{}) {
+		_ = json.NewDecoder(r.Body).Decode(v)
+	}
+	srv := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		switch {
+		case r.RequestURI == "/root/"+testRootFingerprint:
+			w.WriteHeader(http.StatusOK)
+			writeJSON(w, api.RootResponse{
+				RootPEM: api.NewCertificate(testRootCrt),
+			})
+		case r.RequestURI == "/sign":
+			var msg api.SignRequest
+			parseJSON(r, &msg)
+			if msg.CsrPEM.DNSNames[0] == "fail.doe.org" {
+				w.WriteHeader(http.StatusBadRequest)
+				fmt.Fprintf(w, `{"error":"fail","message":"fail"}`)
+				return
+			}
+			w.WriteHeader(http.StatusOK)
+			writeJSON(w, api.SignResponse{
+				CertChainPEM: []api.Certificate{api.NewCertificate(testCrt), api.NewCertificate(testIssCrt)},
+			})
+		case r.RequestURI == "/revoke":
+			var msg api.RevokeRequest
+			parseJSON(r, &msg)
+			if msg.Serial == "fail" {
+				w.WriteHeader(http.StatusBadRequest)
+				fmt.Fprintf(w, `{"error":"fail","message":"fail"}`)
+				return
+			}
+			w.WriteHeader(http.StatusOK)
+			writeJSON(w, api.RevokeResponse{
+				Status: "ok",
+			})
+		default:
+			w.WriteHeader(http.StatusNotFound)
+			fmt.Fprintf(w, `{"error":"not found"}`)
+		}
+	}))
+	t.Cleanup(func() {
+		srv.Close()
+	})
+	u, err := url.Parse(srv.URL)
+	if err != nil {
+		srv.Close()
+		t.Fatal(err)
+	}
+
+	client, err := ca.NewClient(srv.URL, ca.WithTransport(http.DefaultTransport))
+	if err != nil {
+		srv.Close()
+		t.Fatal(err)
+	}
+
+	return u, client
+}
+
+func testX5CIssuer(t *testing.T, caURL *url.URL, password string) *x5cIssuer {
+	t.Helper()
+	key, givenPassword := testX5CKeyPath, password
+	if password != "" {
+		key = testEncryptedKeyPath
+		password = testPassword
+	}
+	x5c, err := newX5CIssuer(caURL, &apiv1.CertificateIssuer{
+		Type:        "x5c",
+		Provisioner: "X5C",
+		Certificate: testX5CPath,
+		Key:         key,
+		Password:    password,
+	})
+	if err != nil {
+		t.Fatal(err)
+	}
+	x5c.password = givenPassword
+	return x5c
+}
+
+func testJWKIssuer(t *testing.T, caURL *url.URL, password string) *jwkIssuer {
+	t.Helper()
+	key, givenPassword := testX5CKeyPath, password
+	if password != "" {
+		key = testEncryptedKeyPath
+		password = testPassword
+	}
+	jwk, err := newJWKIssuer(caURL, &apiv1.CertificateIssuer{
+		Type:        "jwk",
+		Provisioner: "ra@doe.org",
+		Key:         key,
+		Password:    password,
+	})
+	if err != nil {
+		t.Fatal(err)
+	}
+	jwk.password = givenPassword
+	return jwk
+}
+
+func TestMain(m *testing.M) {
+	testRootCrt, testRootKey = mustSignCertificate("Test Root Certificate", nil, x509util.DefaultRootTemplate, nil, nil)
+	testIssCrt, testIssKey = mustSignCertificate("Test Intermediate Certificate", nil, x509util.DefaultIntermediateTemplate, testRootCrt, testRootKey)
+	testX5CCrt, testX5CKey = mustSignCertificate("Test X5C Certificate", nil, x509util.DefaultLeafTemplate, testIssCrt, testIssKey)
+
+	// Final certificate.
+	var err error
+	sans := []string{"doe.org", "jane@doe.org", "127.0.0.1", "::1", "localhost", "uuid:f81d4fae-7dec-11d0-a765-00a0c91e6bf6;name=value"}
+	testCrt, testKey = mustSignCertificate("Test Certificate", sans, x509util.DefaultLeafTemplate, testIssCrt, testIssKey)
+	testCR, err = x509util.CreateCertificateRequest("Test Certificate", sans, testKey)
+	if err != nil {
+		panic(err)
+	}
+
+	// CR used in errors.
+	testFailCR, err = x509util.CreateCertificateRequest("", []string{"fail.doe.org"}, testKey)
+	if err != nil {
+		panic(err)
+	}
+
+	// Password used to encrypto the key
+	testPassword, err = randutil.Hex(32)
+	if err != nil {
+		panic(err)
+	}
+
+	testRootFingerprint = x509util.Fingerprint(testRootCrt)
+
+	path, err := ioutil.TempDir(os.TempDir(), "stepcas")
+	if err != nil {
+		panic(err)
+	}
+
+	testRootPath = filepath.Join(path, "root_ca.crt")
+	testRootKeyPath = filepath.Join(path, "root_ca.key")
+	mustSerializeCrt(testRootPath, testRootCrt)
+	mustSerializeKey(testRootKeyPath, testRootKey)
+
+	testIssPath = filepath.Join(path, "intermediate_ca.crt")
+	testIssKeyPath = filepath.Join(path, "intermediate_ca.key")
+	mustSerializeCrt(testIssPath, testIssCrt)
+	mustSerializeKey(testIssKeyPath, testIssKey)
+
+	testX5CPath = filepath.Join(path, "x5c.crt")
+	testX5CKeyPath = filepath.Join(path, "x5c.key")
+	mustSerializeCrt(testX5CPath, testX5CCrt, testIssCrt)
+	mustSerializeKey(testX5CKeyPath, testX5CKey)
+
+	testEncryptedKeyPath = filepath.Join(path, "x5c.enc.key")
+	mustEncryptKey(testEncryptedKeyPath, testX5CKey)
+
+	code := m.Run()
+	if err := os.RemoveAll(path); err != nil {
+		panic(err)
+	}
+	os.Exit(code)
+}
+
+func Test_init(t *testing.T) {
+	caURL, _ := testCAHelper(t)
+
+	fn, ok := apiv1.LoadCertificateAuthorityServiceNewFunc(apiv1.StepCAS)
+	if !ok {
+		t.Errorf("apiv1.Register() ok = %v, want true", ok)
+		return
+	}
+	fn(context.Background(), apiv1.Options{
+		CertificateAuthority:            caURL.String(),
+		CertificateAuthorityFingerprint: testRootFingerprint,
+		CertificateIssuer: &apiv1.CertificateIssuer{
+			Type:        "x5c",
+			Provisioner: "X5C",
+			Certificate: testX5CPath,
+			Key:         testX5CKeyPath,
+		},
+	})
+}
+
+func TestNew(t *testing.T) {
+	caURL, client := testCAHelper(t)
+	type args struct {
+		ctx  context.Context
+		opts apiv1.Options
+	}
+	tests := []struct {
+		name    string
+		args    args
+		want    *StepCAS
+		wantErr bool
+	}{
+		{"ok", args{context.TODO(), apiv1.Options{
+			CertificateAuthority:            caURL.String(),
+			CertificateAuthorityFingerprint: testRootFingerprint,
+			CertificateIssuer: &apiv1.CertificateIssuer{
+				Type:        "x5c",
+				Provisioner: "X5C",
+				Certificate: testX5CPath,
+				Key:         testX5CKeyPath,
+			},
+		}}, &StepCAS{
+			iss: &x5cIssuer{
+				caURL:    caURL,
+				certFile: testX5CPath,
+				keyFile:  testX5CKeyPath,
+				issuer:   "X5C",
+			},
+			client:      client,
+			fingerprint: testRootFingerprint,
+		}, false},
+		{"ok jwk", args{context.TODO(), apiv1.Options{
+			CertificateAuthority:            caURL.String(),
+			CertificateAuthorityFingerprint: testRootFingerprint,
+			CertificateIssuer: &apiv1.CertificateIssuer{
+				Type:        "jwk",
+				Provisioner: "ra@doe.org",
+				Key:         testX5CKeyPath,
+			},
+		}}, &StepCAS{
+			iss: &jwkIssuer{
+				caURL:   caURL,
+				keyFile: testX5CKeyPath,
+				issuer:  "ra@doe.org",
+			},
+			client:      client,
+			fingerprint: testRootFingerprint,
+		}, false},
+		{"fail authority", args{context.TODO(), apiv1.Options{
+			CertificateAuthority:            "",
+			CertificateAuthorityFingerprint: testRootFingerprint,
+			CertificateIssuer: &apiv1.CertificateIssuer{
+				Type:        "x5c",
+				Provisioner: "X5C",
+				Certificate: testX5CPath,
+				Key:         testX5CKeyPath,
+			},
+		}}, nil, true},
+		{"fail fingerprint", args{context.TODO(), apiv1.Options{
+			CertificateAuthority:            caURL.String(),
+			CertificateAuthorityFingerprint: "",
+			CertificateIssuer: &apiv1.CertificateIssuer{
+				Type:        "x5c",
+				Provisioner: "X5C",
+				Certificate: testX5CPath,
+				Key:         testX5CKeyPath,
+			},
+		}}, nil, true},
+		{"fail type", args{context.TODO(), apiv1.Options{
+			CertificateAuthority:            caURL.String(),
+			CertificateAuthorityFingerprint: testRootFingerprint,
+			CertificateIssuer: &apiv1.CertificateIssuer{
+				Type:        "",
+				Provisioner: "X5C",
+				Certificate: testX5CPath,
+				Key:         testX5CKeyPath,
+			},
+		}}, nil, true},
+		{"fail provisioner", args{context.TODO(), apiv1.Options{
+			CertificateAuthority:            caURL.String(),
+			CertificateAuthorityFingerprint: testRootFingerprint,
+			CertificateIssuer: &apiv1.CertificateIssuer{
+				Type:        "x5c",
+				Provisioner: "",
+				Certificate: testX5CPath,
+				Key:         testX5CKeyPath,
+			},
+		}}, nil, true},
+		{"fail provisioner jwk", args{context.TODO(), apiv1.Options{
+			CertificateAuthority:            caURL.String(),
+			CertificateAuthorityFingerprint: testRootFingerprint,
+			CertificateIssuer: &apiv1.CertificateIssuer{
+				Type:        "jwk",
+				Provisioner: "",
+				Key:         testX5CKeyPath,
+			},
+		}}, nil, true},
+		{"fail certificate", args{context.TODO(), apiv1.Options{
+			CertificateAuthority:            caURL.String(),
+			CertificateAuthorityFingerprint: testRootFingerprint,
+			CertificateIssuer: &apiv1.CertificateIssuer{
+				Type:        "x5c",
+				Provisioner: "X5C",
+				Certificate: "",
+				Key:         testX5CKeyPath,
+			},
+		}}, nil, true},
+		{"fail key", args{context.TODO(), apiv1.Options{
+			CertificateAuthority:            caURL.String(),
+			CertificateAuthorityFingerprint: testRootFingerprint,
+			CertificateIssuer: &apiv1.CertificateIssuer{
+				Type:        "x5c",
+				Provisioner: "X5C",
+				Certificate: testX5CPath,
+				Key:         "",
+			},
+		}}, nil, true},
+		{"fail key jwk", args{context.TODO(), apiv1.Options{
+			CertificateAuthority:            caURL.String(),
+			CertificateAuthorityFingerprint: testRootFingerprint,
+			CertificateIssuer: &apiv1.CertificateIssuer{
+				Type:        "jwk",
+				Provisioner: "ra@smallstep.com",
+				Key:         "",
+			},
+		}}, nil, true},
+		{"bad authority", args{context.TODO(), apiv1.Options{
+			CertificateAuthority:            "https://foobar",
+			CertificateAuthorityFingerprint: testRootFingerprint,
+			CertificateIssuer: &apiv1.CertificateIssuer{
+				Type:        "x5c",
+				Provisioner: "X5C",
+				Certificate: testX5CPath,
+				Key:         testX5CKeyPath,
+			},
+		}}, nil, true},
+		{"fail parse url", args{context.TODO(), apiv1.Options{
+			CertificateAuthority:            "::failparse",
+			CertificateAuthorityFingerprint: testRootFingerprint,
+			CertificateIssuer: &apiv1.CertificateIssuer{
+				Type:        "x5c",
+				Provisioner: "X5C",
+				Certificate: testX5CPath,
+				Key:         testX5CKeyPath,
+			},
+		}}, nil, true},
+		{"fail new client", args{context.TODO(), apiv1.Options{
+			CertificateAuthority:            caURL.String(),
+			CertificateAuthorityFingerprint: "foobar",
+			CertificateIssuer: &apiv1.CertificateIssuer{
+				Type:        "x5c",
+				Provisioner: "X5C",
+				Certificate: testX5CPath,
+				Key:         testX5CKeyPath,
+			},
+		}}, nil, true},
+		{"fail new x5c issuer", args{context.TODO(), apiv1.Options{
+			CertificateAuthority:            caURL.String(),
+			CertificateAuthorityFingerprint: testRootFingerprint,
+			CertificateIssuer: &apiv1.CertificateIssuer{
+				Type:        "x5c",
+				Provisioner: "X5C",
+				Certificate: testX5CPath + ".missing",
+				Key:         testX5CKeyPath,
+			},
+		}}, nil, true},
+		{"fail new jwk issuer", args{context.TODO(), apiv1.Options{
+			CertificateAuthority:            caURL.String(),
+			CertificateAuthorityFingerprint: testRootFingerprint,
+			CertificateIssuer: &apiv1.CertificateIssuer{
+				Type:        "jwk",
+				Provisioner: "ra@doe.org",
+				Key:         testX5CKeyPath + ".missing",
+			},
+		}}, nil, true},
+		{"bad issuer", args{context.TODO(), apiv1.Options{
+			CertificateAuthority:            caURL.String(),
+			CertificateAuthorityFingerprint: testRootFingerprint,
+			CertificateIssuer:               nil}}, nil, true},
+		{"bad issuer type", args{context.TODO(), apiv1.Options{
+			CertificateAuthority:            caURL.String(),
+			CertificateAuthorityFingerprint: testRootFingerprint,
+			CertificateIssuer: &apiv1.CertificateIssuer{
+				Type:        "fail",
+				Provisioner: "X5C",
+				Certificate: testX5CPath,
+				Key:         testX5CKeyPath,
+			},
+		}}, nil, true},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			got, err := New(tt.args.ctx, tt.args.opts)
+			if (err != nil) != tt.wantErr {
+				t.Errorf("New() error = %v, wantErr %v", err, tt.wantErr)
+				return
+			}
+			// We cannot compare client
+			if got != nil && tt.want != nil {
+				got.client = tt.want.client
+			}
+			if !reflect.DeepEqual(got, tt.want) {
+				t.Errorf("New() = %v, want %v", got, tt.want)
+			}
+		})
+	}
+}
+
+func TestStepCAS_CreateCertificate(t *testing.T) {
+	caURL, client := testCAHelper(t)
+	x5c := testX5CIssuer(t, caURL, "")
+	jwk := testJWKIssuer(t, caURL, "")
+	x5cEnc := testX5CIssuer(t, caURL, testPassword)
+	jwkEnc := testJWKIssuer(t, caURL, testPassword)
+	x5cBad := testX5CIssuer(t, caURL, "bad-password")
+	jwkBad := testJWKIssuer(t, caURL, "bad-password")
+
+	type fields struct {
+		iss         stepIssuer
+		client      *ca.Client
+		fingerprint string
+	}
+	type args struct {
+		req *apiv1.CreateCertificateRequest
+	}
+	tests := []struct {
+		name    string
+		fields  fields
+		args    args
+		want    *apiv1.CreateCertificateResponse
+		wantErr bool
+	}{
+		{"ok", fields{x5c, client, testRootFingerprint}, args{&apiv1.CreateCertificateRequest{
+			CSR:      testCR,
+			Lifetime: time.Hour,
+		}}, &apiv1.CreateCertificateResponse{
+			Certificate:      testCrt,
+			CertificateChain: []*x509.Certificate{testIssCrt},
+		}, false},
+		{"ok with password", fields{x5cEnc, client, testRootFingerprint}, args{&apiv1.CreateCertificateRequest{
+			CSR:      testCR,
+			Lifetime: time.Hour,
+		}}, &apiv1.CreateCertificateResponse{
+			Certificate:      testCrt,
+			CertificateChain: []*x509.Certificate{testIssCrt},
+		}, false},
+		{"ok jwk", fields{jwk, client, testRootFingerprint}, args{&apiv1.CreateCertificateRequest{
+			CSR:      testCR,
+			Lifetime: time.Hour,
+		}}, &apiv1.CreateCertificateResponse{
+			Certificate:      testCrt,
+			CertificateChain: []*x509.Certificate{testIssCrt},
+		}, false},
+		{"ok jwk with password", fields{jwkEnc, client, testRootFingerprint}, args{&apiv1.CreateCertificateRequest{
+			CSR:      testCR,
+			Lifetime: time.Hour,
+		}}, &apiv1.CreateCertificateResponse{
+			Certificate:      testCrt,
+			CertificateChain: []*x509.Certificate{testIssCrt},
+		}, false},
+		{"fail CSR", fields{x5c, client, testRootFingerprint}, args{&apiv1.CreateCertificateRequest{
+			CSR:      nil,
+			Lifetime: time.Hour,
+		}}, nil, true},
+		{"fail lifetime", fields{x5c, client, testRootFingerprint}, args{&apiv1.CreateCertificateRequest{
+			CSR:      testCR,
+			Lifetime: 0,
+		}}, nil, true},
+		{"fail sign token", fields{mockErrIssuer{}, client, testRootFingerprint}, args{&apiv1.CreateCertificateRequest{
+			CSR:      testCR,
+			Lifetime: time.Hour,
+		}}, nil, true},
+		{"fail client sign", fields{x5c, client, testRootFingerprint}, args{&apiv1.CreateCertificateRequest{
+			CSR:      testFailCR,
+			Lifetime: time.Hour,
+		}}, nil, true},
+		{"fail password", fields{x5cBad, client, testRootFingerprint}, args{&apiv1.CreateCertificateRequest{
+			CSR:      testCR,
+			Lifetime: time.Hour,
+		}}, nil, true},
+		{"fail jwk password", fields{jwkBad, client, testRootFingerprint}, args{&apiv1.CreateCertificateRequest{
+			CSR:      testCR,
+			Lifetime: time.Hour,
+		}}, nil, true},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			s := &StepCAS{
+				iss:         tt.fields.iss,
+				client:      tt.fields.client,
+				fingerprint: tt.fields.fingerprint,
+			}
+			got, err := s.CreateCertificate(tt.args.req)
+			if (err != nil) != tt.wantErr {
+				t.Errorf("StepCAS.CreateCertificate() error = %v, wantErr %v", err, tt.wantErr)
+				return
+			}
+			if !reflect.DeepEqual(got, tt.want) {
+				t.Errorf("StepCAS.CreateCertificate() = %v, want %v", got, tt.want)
+			}
+		})
+	}
+}
+
+func TestStepCAS_RenewCertificate(t *testing.T) {
+	caURL, client := testCAHelper(t)
+	x5c := testX5CIssuer(t, caURL, "")
+	jwk := testJWKIssuer(t, caURL, "")
+
+	type fields struct {
+		iss         stepIssuer
+		client      *ca.Client
+		fingerprint string
+	}
+	type args struct {
+		req *apiv1.RenewCertificateRequest
+	}
+	tests := []struct {
+		name    string
+		fields  fields
+		args    args
+		want    *apiv1.RenewCertificateResponse
+		wantErr bool
+	}{
+		{"not implemented", fields{x5c, client, testRootFingerprint}, args{&apiv1.RenewCertificateRequest{
+			CSR:      testCR,
+			Lifetime: time.Hour,
+		}}, nil, true},
+		{"not implemented jwk", fields{jwk, client, testRootFingerprint}, args{&apiv1.RenewCertificateRequest{
+			CSR:      testCR,
+			Lifetime: time.Hour,
+		}}, nil, true},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			s := &StepCAS{
+				iss:         tt.fields.iss,
+				client:      tt.fields.client,
+				fingerprint: tt.fields.fingerprint,
+			}
+			got, err := s.RenewCertificate(tt.args.req)
+			if (err != nil) != tt.wantErr {
+				t.Errorf("StepCAS.RenewCertificate() error = %v, wantErr %v", err, tt.wantErr)
+				return
+			}
+			if !reflect.DeepEqual(got, tt.want) {
+				t.Errorf("StepCAS.RenewCertificate() = %v, want %v", got, tt.want)
+			}
+		})
+	}
+}
+
+func TestStepCAS_RevokeCertificate(t *testing.T) {
+	caURL, client := testCAHelper(t)
+	x5c := testX5CIssuer(t, caURL, "")
+	jwk := testJWKIssuer(t, caURL, "")
+	x5cEnc := testX5CIssuer(t, caURL, testPassword)
+	jwkEnc := testJWKIssuer(t, caURL, testPassword)
+	x5cBad := testX5CIssuer(t, caURL, "bad-password")
+	jwkBad := testJWKIssuer(t, caURL, "bad-password")
+
+	type fields struct {
+		iss         stepIssuer
+		client      *ca.Client
+		fingerprint string
+	}
+	type args struct {
+		req *apiv1.RevokeCertificateRequest
+	}
+	tests := []struct {
+		name    string
+		fields  fields
+		args    args
+		want    *apiv1.RevokeCertificateResponse
+		wantErr bool
+	}{
+		{"ok serial number", fields{x5c, client, testRootFingerprint}, args{&apiv1.RevokeCertificateRequest{
+			SerialNumber: "ok",
+			Certificate:  nil,
+		}}, &apiv1.RevokeCertificateResponse{}, false},
+		{"ok certificate", fields{x5c, client, testRootFingerprint}, args{&apiv1.RevokeCertificateRequest{
+			SerialNumber: "",
+			Certificate:  testCrt,
+		}}, &apiv1.RevokeCertificateResponse{
+			Certificate: testCrt,
+		}, false},
+		{"ok both", fields{x5c, client, testRootFingerprint}, args{&apiv1.RevokeCertificateRequest{
+			SerialNumber: "ok",
+			Certificate:  testCrt,
+		}}, &apiv1.RevokeCertificateResponse{
+			Certificate: testCrt,
+		}, false},
+		{"ok with password", fields{x5cEnc, client, testRootFingerprint}, args{&apiv1.RevokeCertificateRequest{
+			SerialNumber: "ok",
+			Certificate:  nil,
+		}}, &apiv1.RevokeCertificateResponse{}, false},
+		{"ok serial number jwk", fields{jwk, client, testRootFingerprint}, args{&apiv1.RevokeCertificateRequest{
+			SerialNumber: "ok",
+			Certificate:  nil,
+		}}, &apiv1.RevokeCertificateResponse{}, false},
+		{"ok certificate jwk", fields{jwk, client, testRootFingerprint}, args{&apiv1.RevokeCertificateRequest{
+			SerialNumber: "",
+			Certificate:  testCrt,
+		}}, &apiv1.RevokeCertificateResponse{
+			Certificate: testCrt,
+		}, false},
+		{"ok both jwk", fields{jwk, client, testRootFingerprint}, args{&apiv1.RevokeCertificateRequest{
+			SerialNumber: "ok",
+			Certificate:  testCrt,
+		}}, &apiv1.RevokeCertificateResponse{
+			Certificate: testCrt,
+		}, false},
+		{"ok jwk with password", fields{jwkEnc, client, testRootFingerprint}, args{&apiv1.RevokeCertificateRequest{
+			SerialNumber: "ok",
+			Certificate:  nil,
+		}}, &apiv1.RevokeCertificateResponse{}, false},
+		{"fail request", fields{x5c, client, testRootFingerprint}, args{&apiv1.RevokeCertificateRequest{
+			SerialNumber: "",
+			Certificate:  nil,
+		}}, nil, true},
+		{"fail revoke token", fields{mockErrIssuer{}, client, testRootFingerprint}, args{&apiv1.RevokeCertificateRequest{
+			SerialNumber: "ok",
+		}}, nil, true},
+		{"fail client revoke", fields{x5c, client, testRootFingerprint}, args{&apiv1.RevokeCertificateRequest{
+			SerialNumber: "fail",
+		}}, nil, true},
+		{"fail password", fields{x5cBad, client, testRootFingerprint}, args{&apiv1.RevokeCertificateRequest{
+			SerialNumber: "ok",
+			Certificate:  nil,
+		}}, nil, true},
+		{"fail jwk password", fields{jwkBad, client, testRootFingerprint}, args{&apiv1.RevokeCertificateRequest{
+			SerialNumber: "ok",
+			Certificate:  nil,
+		}}, nil, true},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			s := &StepCAS{
+				iss:         tt.fields.iss,
+				client:      tt.fields.client,
+				fingerprint: tt.fields.fingerprint,
+			}
+			got, err := s.RevokeCertificate(tt.args.req)
+			if (err != nil) != tt.wantErr {
+				t.Errorf("StepCAS.RevokeCertificate() error = %v, wantErr %v", err, tt.wantErr)
+				return
+			}
+			if !reflect.DeepEqual(got, tt.want) {
+				t.Errorf("StepCAS.RevokeCertificate() = %v, want %v", got, tt.want)
+			}
+		})
+	}
+}
+
+func TestStepCAS_GetCertificateAuthority(t *testing.T) {
+	caURL, client := testCAHelper(t)
+	x5c := testX5CIssuer(t, caURL, "")
+	jwk := testJWKIssuer(t, caURL, "")
+
+	type fields struct {
+		iss         stepIssuer
+		client      *ca.Client
+		fingerprint string
+	}
+	type args struct {
+		req *apiv1.GetCertificateAuthorityRequest
+	}
+	tests := []struct {
+		name    string
+		fields  fields
+		args    args
+		want    *apiv1.GetCertificateAuthorityResponse
+		wantErr bool
+	}{
+		{"ok", fields{x5c, client, testRootFingerprint}, args{&apiv1.GetCertificateAuthorityRequest{
+			Name: caURL.String(),
+		}}, &apiv1.GetCertificateAuthorityResponse{
+			RootCertificate: testRootCrt,
+		}, false},
+		{"ok jwk", fields{jwk, client, testRootFingerprint}, args{&apiv1.GetCertificateAuthorityRequest{
+			Name: caURL.String(),
+		}}, &apiv1.GetCertificateAuthorityResponse{
+			RootCertificate: testRootCrt,
+		}, false},
+		{"fail fingerprint", fields{x5c, client, "fail"}, args{&apiv1.GetCertificateAuthorityRequest{
+			Name: caURL.String(),
+		}}, nil, true},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			s := &StepCAS{
+				iss:         tt.fields.iss,
+				client:      tt.fields.client,
+				fingerprint: tt.fields.fingerprint,
+			}
+			got, err := s.GetCertificateAuthority(tt.args.req)
+			if (err != nil) != tt.wantErr {
+				t.Errorf("StepCAS.GetCertificateAuthority() error = %v, wantErr %v", err, tt.wantErr)
+				return
+			}
+			if !reflect.DeepEqual(got, tt.want) {
+				t.Errorf("StepCAS.GetCertificateAuthority() = %v, want %v", got, tt.want)
+			}
+		})
+	}
+}

cas/stepcas/x5c_issuer.go

@@ -0,0 +1,185 @@
+package stepcas
+
+import (
+	"crypto"
+	"crypto/ecdsa"
+	"crypto/ed25519"
+	"crypto/rsa"
+	"net/url"
+	"time"
+
+	"github.com/pkg/errors"
+	"github.com/smallstep/certificates/cas/apiv1"
+	"go.step.sm/crypto/jose"
+	"go.step.sm/crypto/pemutil"
+	"go.step.sm/crypto/randutil"
+)
+
+const defaultValidity = 5 * time.Minute
+
+// timeNow returns the current time.
+// This method is used for unit testing purposes.
+var timeNow = func() time.Time {
+	return time.Now()
+}
+
+type x5cIssuer struct {
+	caURL    *url.URL
+	issuer   string
+	certFile string
+	keyFile  string
+	password string
+}
+
+// newX5CIssuer create a new x5c token issuer. The given configuration should be
+// already validate.
+func newX5CIssuer(caURL *url.URL, cfg *apiv1.CertificateIssuer) (*x5cIssuer, error) {
+	_, err := newX5CSigner(cfg.Certificate, cfg.Key, cfg.Password)
+	if err != nil {
+		return nil, err
+	}
+
+	return &x5cIssuer{
+		caURL:    caURL,
+		issuer:   cfg.Provisioner,
+		certFile: cfg.Certificate,
+		keyFile:  cfg.Key,
+		password: cfg.Password,
+	}, nil
+}
+
+func (i *x5cIssuer) SignToken(subject string, sans []string) (string, error) {
+	aud := i.caURL.ResolveReference(&url.URL{
+		Path:     "/1.0/sign",
+		Fragment: "x5c/" + i.issuer,
+	}).String()
+
+	return i.createToken(aud, subject, sans)
+}
+
+func (i *x5cIssuer) RevokeToken(subject string) (string, error) {
+	aud := i.caURL.ResolveReference(&url.URL{
+		Path:     "/1.0/revoke",
+		Fragment: "x5c/" + i.issuer,
+	}).String()
+
+	return i.createToken(aud, subject, nil)
+}
+
+func (i *x5cIssuer) Lifetime(d time.Duration) time.Duration {
+	cert, err := pemutil.ReadCertificate(i.certFile, pemutil.WithFirstBlock())
+	if err != nil {
+		return d
+	}
+	now := timeNow()
+	if now.Add(d + time.Minute).After(cert.NotAfter) {
+		return cert.NotAfter.Sub(now) - time.Minute
+	}
+	return d
+}
+
+func (i *x5cIssuer) createToken(aud, sub string, sans []string) (string, error) {
+	signer, err := newX5CSigner(i.certFile, i.keyFile, i.password)
+	if err != nil {
+		return "", err
+	}
+
+	id, err := randutil.Hex(64) // 256 bits
+	if err != nil {
+		return "", err
+	}
+
+	claims := defaultClaims(i.issuer, sub, aud, id)
+	builder := jose.Signed(signer).Claims(claims)
+	if len(sans) > 0 {
+		builder = builder.Claims(map[string]interface{}{
+			"sans": sans,
+		})
+	}
+
+	tok, err := builder.CompactSerialize()
+	if err != nil {
+		return "", errors.Wrap(err, "error signing token")
+	}
+
+	return tok, nil
+}
+
+func defaultClaims(iss, sub, aud, id string) jose.Claims {
+	now := timeNow()
+	return jose.Claims{
+		ID:        id,
+		Issuer:    iss,
+		Subject:   sub,
+		Audience:  jose.Audience{aud},
+		Expiry:    jose.NewNumericDate(now.Add(defaultValidity)),
+		NotBefore: jose.NewNumericDate(now),
+		IssuedAt:  jose.NewNumericDate(now),
+	}
+}
+
+func readKey(keyFile, password string) (crypto.Signer, error) {
+	var opts []pemutil.Options
+	if password != "" {
+		opts = append(opts, pemutil.WithPassword([]byte(password)))
+	}
+	key, err := pemutil.Read(keyFile, opts...)
+	if err != nil {
+		return nil, err
+	}
+	signer, ok := key.(crypto.Signer)
+	if !ok {
+		return nil, errors.New("key is not a crypto.Signer")
+	}
+	return signer, nil
+}
+
+func newX5CSigner(certFile, keyFile, password string) (jose.Signer, error) {
+	signer, err := readKey(keyFile, password)
+	if err != nil {
+		return nil, err
+	}
+	kid, err := jose.Thumbprint(&jose.JSONWebKey{Key: signer.Public()})
+	if err != nil {
+		return nil, err
+	}
+	certs, err := jose.ValidateX5C(certFile, signer)
+	if err != nil {
+		return nil, errors.Wrap(err, "error validating x5c certificate chain and key")
+	}
+
+	so := new(jose.SignerOptions)
+	so.WithType("JWT")
+	so.WithHeader("kid", kid)
+	so.WithHeader("x5c", certs)
+	return newJoseSigner(signer, so)
+}
+
+func newJoseSigner(key crypto.Signer, so *jose.SignerOptions) (jose.Signer, error) {
+	var alg jose.SignatureAlgorithm
+	switch k := key.Public().(type) {
+	case *ecdsa.PublicKey:
+		switch k.Curve.Params().Name {
+		case "P-256":
+			alg = jose.ES256
+		case "P-384":
+			alg = jose.ES384
+		case "P-521":
+			alg = jose.ES512
+		default:
+			return nil, errors.Errorf("unsupported elliptic curve %s", k.Curve.Params().Name)
+		}
+	case ed25519.PublicKey:
+		alg = jose.EdDSA
+	case *rsa.PublicKey:
+		alg = jose.DefaultRSASigAlgorithm
+	default:
+		return nil, errors.Errorf("unsupported key type %T", k)
+	}
+
+	signer, err := jose.NewSigner(jose.SigningKey{Algorithm: alg, Key: key}, so)
+	if err != nil {
+		return nil, errors.Wrap(err, "error creating jose.Signer")
+	}
+	return signer, nil
+}

cas/stepcas/x5c_issuer_test.go

@@ -0,0 +1,277 @@
+package stepcas
+
+import (
+	"crypto"
+	"crypto/ecdsa"
+	"crypto/ed25519"
+	"crypto/elliptic"
+	"crypto/rand"
+	"crypto/rsa"
+	"io"
+	"net/url"
+	"reflect"
+	"testing"
+	"time"
+
+	"go.step.sm/crypto/jose"
+)
+
+type noneSigner []byte
+
+func (b noneSigner) Public() crypto.PublicKey {
+	return []byte(b)
+}
+
+func (b noneSigner) Sign(rand io.Reader, digest []byte, opts crypto.SignerOpts) (signature []byte, err error) {
+	return digest, nil
+}
+
+func fakeTime(t *testing.T) {
+	t.Helper()
+	tmp := timeNow
+	t.Cleanup(func() {
+		timeNow = tmp
+	})
+	timeNow = func() time.Time {
+		return testX5CCrt.NotBefore
+	}
+}
+
+func Test_x5cIssuer_SignToken(t *testing.T) {
+	caURL, err := url.Parse("https://ca.smallstep.com")
+	if err != nil {
+		t.Fatal(err)
+	}
+	type fields struct {
+		caURL    *url.URL
+		certFile string
+		keyFile  string
+		issuer   string
+	}
+	type args struct {
+		subject string
+		sans    []string
+	}
+	type claims struct {
+		Aud  []string `json:"aud"`
+		Sub  string   `json:"sub"`
+		Sans []string `json:"sans"`
+	}
+	tests := []struct {
+		name    string
+		fields  fields
+		args    args
+		wantErr bool
+	}{
+		{"ok", fields{caURL, testX5CPath, testX5CKeyPath, "X5C"}, args{"doe", []string{"doe.org"}}, false},
+		{"fail crt", fields{caURL, "", testX5CKeyPath, "X5C"}, args{"doe", []string{"doe.org"}}, true},
+		{"fail key", fields{caURL, testX5CPath, "", "X5C"}, args{"doe", []string{"doe.org"}}, true},
+		{"fail no signer", fields{caURL, testIssKeyPath, testIssPath, "X5C"}, args{"doe", []string{"doe.org"}}, true},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			i := &x5cIssuer{
+				caURL:    tt.fields.caURL,
+				certFile: tt.fields.certFile,
+				keyFile:  tt.fields.keyFile,
+				issuer:   tt.fields.issuer,
+			}
+			got, err := i.SignToken(tt.args.subject, tt.args.sans)
+			if (err != nil) != tt.wantErr {
+				t.Errorf("x5cIssuer.SignToken() error = %v, wantErr %v", err, tt.wantErr)
+			}
+			if !tt.wantErr {
+				jwt, err := jose.ParseSigned(got)
+				if err != nil {
+					t.Errorf("jose.ParseSigned() error = %v", err)
+				}
+				var c claims
+				want := claims{
+					Aud:  []string{tt.fields.caURL.String() + "/1.0/sign#x5c/X5C"},
+					Sub:  tt.args.subject,
+					Sans: tt.args.sans,
+				}
+				if err := jwt.Claims(testX5CKey.Public(), &c); err != nil {
+					t.Errorf("jwt.Claims() error = %v", err)
+				}
+				if !reflect.DeepEqual(c, want) {
+					t.Errorf("jwt.Claims() claims = %#v, want %#v", c, want)
+				}
+			}
+		})
+	}
+}
+
+func Test_x5cIssuer_RevokeToken(t *testing.T) {
+	caURL, err := url.Parse("https://ca.smallstep.com")
+	if err != nil {
+		t.Fatal(err)
+	}
+	type fields struct {
+		caURL    *url.URL
+		certFile string
+		keyFile  string
+		issuer   string
+	}
+	type args struct {
+		subject string
+	}
+	type claims struct {
+		Aud  []string `json:"aud"`
+		Sub  string   `json:"sub"`
+		Sans []string `json:"sans"`
+	}
+	tests := []struct {
+		name    string
+		fields  fields
+		args    args
+		wantErr bool
+	}{
+		{"ok", fields{caURL, testX5CPath, testX5CKeyPath, "X5C"}, args{"doe"}, false},
+		{"fail crt", fields{caURL, "", testX5CKeyPath, "X5C"}, args{"doe"}, true},
+		{"fail key", fields{caURL, testX5CPath, "", "X5C"}, args{"doe"}, true},
+		{"fail no signer", fields{caURL, testIssKeyPath, testIssPath, "X5C"}, args{"doe"}, true},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			i := &x5cIssuer{
+				caURL:    tt.fields.caURL,
+				certFile: tt.fields.certFile,
+				keyFile:  tt.fields.keyFile,
+				issuer:   tt.fields.issuer,
+			}
+			got, err := i.RevokeToken(tt.args.subject)
+			if (err != nil) != tt.wantErr {
+				t.Errorf("x5cIssuer.RevokeToken() error = %v, wantErr %v", err, tt.wantErr)
+				return
+			}
+			if !tt.wantErr {
+				jwt, err := jose.ParseSigned(got)
+				if err != nil {
+					t.Errorf("jose.ParseSigned() error = %v", err)
+				}
+				var c claims
+				want := claims{
+					Aud: []string{tt.fields.caURL.String() + "/1.0/revoke#x5c/X5C"},
+					Sub: tt.args.subject,
+				}
+				if err := jwt.Claims(testX5CKey.Public(), &c); err != nil {
+					t.Errorf("jwt.Claims() error = %v", err)
+				}
+				if !reflect.DeepEqual(c, want) {
+					t.Errorf("jwt.Claims() claims = %#v, want %#v", c, want)
+				}
+			}
+		})
+	}
+}
+
+func Test_x5cIssuer_Lifetime(t *testing.T) {
+	fakeTime(t)
+	caURL, err := url.Parse("https://ca.smallstep.com")
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	// With a leeway of 1m the max duration will be 59m.
+	maxDuration := testX5CCrt.NotAfter.Sub(timeNow()) - time.Minute
+
+	type fields struct {
+		caURL    *url.URL
+		certFile string
+		keyFile  string
+		issuer   string
+	}
+	type args struct {
+		d time.Duration
+	}
+	tests := []struct {
+		name   string
+		fields fields
+		args   args
+		want   time.Duration
+	}{
+		{"ok 0s", fields{caURL, testX5CPath, testX5CKeyPath, "X5C"}, args{0}, 0},
+		{"ok 1m", fields{caURL, testX5CPath, testX5CKeyPath, "X5C"}, args{time.Minute}, time.Minute},
+		{"ok max-1m", fields{caURL, testX5CPath, testX5CKeyPath, "X5C"}, args{maxDuration - time.Minute}, maxDuration - time.Minute},
+		{"ok max", fields{caURL, testX5CPath, testX5CKeyPath, "X5C"}, args{maxDuration}, maxDuration},
+		{"ok max+1m", fields{caURL, testX5CPath, testX5CKeyPath, "X5C"}, args{maxDuration + time.Minute}, maxDuration},
+		{"ok fail", fields{caURL, testX5CPath + ".missing", testX5CKeyPath, "X5C"}, args{maxDuration + time.Minute}, maxDuration + time.Minute},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			i := &x5cIssuer{
+				caURL:    tt.fields.caURL,
+				certFile: tt.fields.certFile,
+				keyFile:  tt.fields.keyFile,
+				issuer:   tt.fields.issuer,
+			}
+			if got := i.Lifetime(tt.args.d); got != tt.want {
+				t.Errorf("x5cIssuer.Lifetime() = %v, want %v", got, tt.want)
+			}
+		})
+	}
+}
+
+func Test_newJoseSigner(t *testing.T) {
+	mustSigner := func(args ...interface{}) crypto.Signer {
+		if err := args[len(args)-1]; err != nil {
+			t.Fatal(err)
+		}
+		for _, a := range args {
+			if s, ok := a.(crypto.Signer); ok {
+				return s
+			}
+		}
+		t.Fatal("signer not found")
+		return nil
+	}
+
+	p224 := mustSigner(ecdsa.GenerateKey(elliptic.P224(), rand.Reader))
+	p256 := mustSigner(ecdsa.GenerateKey(elliptic.P256(), rand.Reader))
+	p384 := mustSigner(ecdsa.GenerateKey(elliptic.P384(), rand.Reader))
+	p521 := mustSigner(ecdsa.GenerateKey(elliptic.P521(), rand.Reader))
+	edKey := mustSigner(ed25519.GenerateKey(rand.Reader))
+	rsaKey := mustSigner(rsa.GenerateKey(rand.Reader, 2048))
+
+	type args struct {
+		key crypto.Signer
+		so  *jose.SignerOptions
+	}
+	tests := []struct {
+		name    string
+		args    args
+		want    []jose.Header
+		wantErr bool
+	}{
+		{"p256", args{p256, nil}, []jose.Header{{Algorithm: "ES256"}}, false},
+		{"p384", args{p384, new(jose.SignerOptions).WithType("JWT")}, []jose.Header{{Algorithm: "ES384", ExtraHeaders: map[jose.HeaderKey]interface{}{"typ": "JWT"}}}, false},
+		{"p521", args{p521, new(jose.SignerOptions).WithHeader("kid", "the-kid")}, []jose.Header{{Algorithm: "ES512", KeyID: "the-kid"}}, false},
+		{"ed25519", args{edKey, nil}, []jose.Header{{Algorithm: "EdDSA"}}, false},
+		{"rsa", args{rsaKey, nil}, []jose.Header{{Algorithm: "RS256"}}, false},
+		{"fail p224", args{p224, nil}, nil, true},
+		{"fail signer", args{noneSigner{1, 2, 3}, nil}, nil, true},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			got, err := newJoseSigner(tt.args.key, tt.args.so)
+			if (err != nil) != tt.wantErr {
+				t.Errorf("newJoseSigner() error = %v, wantErr %v", err, tt.wantErr)
+				return
+			}
+			if !tt.wantErr {
+				jws, err := got.Sign([]byte("{}"))
+				if err != nil {
+					t.Errorf("jose.Signer.Sign() err = %v", err)
+				}
+				jwt, err := jose.ParseSigned(jws.FullSerialize())
+				if err != nil {
+					t.Errorf("jose.ParseSigned() err = %v", err)
+				}
+				if !reflect.DeepEqual(jwt.Headers, tt.want) {
+					t.Errorf("jose.Header got = %v, want = %v", jwt.Headers, tt.want)
+				}
+			}
+		})
+	}
+}

cmd/step-ca/main.go

@@ -37,6 +37,7 @@ import (
 	// Enabled cas interfaces.
 	_ "github.com/smallstep/certificates/cas/cloudcas"
 	_ "github.com/smallstep/certificates/cas/softcas"
+	_ "github.com/smallstep/certificates/cas/stepcas"
 )
 
 // commit and buildTime are filled in during build by the Makefile

go.mod

@@ -21,7 +21,7 @@ require (
 	github.com/smallstep/nosql v0.3.6
 	github.com/urfave/cli v1.22.4
 	go.step.sm/cli-utils v0.2.0
-	go.step.sm/crypto v0.7.3
+	go.step.sm/crypto v0.8.0
 	golang.org/x/crypto v0.0.0-20201016220609-9e8e0b390897
 	golang.org/x/net v0.0.0-20210119194325-5f4716e94777
 	google.golang.org/api v0.33.0

go.sum

@@ -322,8 +322,8 @@ go.opencensus.io v0.22.5/go.mod h1:5pWMHQbX5EPX2/62yrJeAkowc+lfs/XD7Uxpq3pI6kk=
 go.step.sm/cli-utils v0.2.0 h1:hpVu9+6dpv/7/Bd8nGJFc3V+gQ+TciSJRTu9TavDUQ4=
 go.step.sm/cli-utils v0.2.0/go.mod h1:+t4qCp5NO+080DdGkJxEh3xL5S4TcYC2JTPLMM72b6Y=
 go.step.sm/crypto v0.6.1/go.mod h1:AKS4yMZVZD4EGjpSkY4eibuMenrvKCscb+BpWMet8c0=
-go.step.sm/crypto v0.7.3 h1:uWkT0vsaZVixgn5x6Ojqittry9PiyVn2ihEYG/qOxV8=
+go.step.sm/crypto v0.8.0 h1:S4qBPyy3hR7KWLybSkHB0H14pwFfYkom4RZ96JzmXig=
-go.step.sm/crypto v0.7.3/go.mod h1:AKS4yMZVZD4EGjpSkY4eibuMenrvKCscb+BpWMet8c0=
+go.step.sm/crypto v0.8.0/go.mod h1:+CYG05Mek1YDqi5WK0ERc6cOpKly2i/a5aZmU1sfGj0=
 golang.org/x/crypto v0.0.0-20181203042331-505ab145d0a9/go.mod h1:6SG95UA2DQfeDnfUPMdvaQW0Q7yPrPDi9nlGo2tz2b4=
 golang.org/x/crypto v0.0.0-20190308221718-c2843e01d9a2/go.mod h1:djNgcEr1/C05ACkg1iLfiJU5Ep61QUkGW8qpdssI0+w=
 golang.org/x/crypto v0.0.0-20190510104115-cbcb75029529/go.mod h1:yigFU9vqHzYiE8UmvKecakEJjdnWj3jj499lnFckfCI=