Add template support on k8ssa provisioner.

authority/provisioner/k8sSA.go

@@ -10,6 +10,7 @@ import (
 
 	"github.com/pkg/errors"
 	"github.com/smallstep/certificates/errs"
+	"github.com/smallstep/certificates/sshutil"
 	"github.com/smallstep/certificates/x509util"
 	"github.com/smallstep/cli/crypto/pemutil"
 	"github.com/smallstep/cli/jose"
@@ -46,6 +47,7 @@ type K8sSA struct {
 	PubKeys    []byte      `json:"publicKeys,omitempty"`
 	Claims     *Claims     `json:"claims,omitempty"`
 	Options    *Options    `json:"options,omitempty"`
+	SSHOptions *SSHOptions `json:"sshOptions,omitempty"`
 	claimer    *Claimer
 	audiences  Audiences
 	//kauthn    kauthn.AuthenticationV1Interface
@@ -249,16 +251,27 @@ func (p *K8sSA) AuthorizeSSHSign(ctx context.Context, token string) ([]SignOptio
 	if !p.claimer.IsSSHCAEnabled() {
 		return nil, errs.Unauthorized("k8ssa.AuthorizeSSHSign; sshCA is disabled for k8sSA provisioner %s", p.GetID())
 	}
-	if _, err := p.authorizeToken(token, p.audiences.SSHSign); err != nil {
+	claims, err := p.authorizeToken(token, p.audiences.SSHSign)
+	if err != nil {
 		return nil, errs.Wrap(http.StatusInternalServerError, err, "k8ssa.AuthorizeSSHSign")
 	}
 
-	// Default to a user certificate with no principals if not set
-	signOptions := []SignOption{sshCertDefaultsModifier{CertType: SSHUserCert}}
+	// Certificate templates.
+	// Set some default variables to be used in the templates.
+	data := sshutil.CreateTemplateData(sshutil.HostCert, claims.ServiceAccountName, []string{claims.ServiceAccountName})
+	if v, err := unsafeParseSigned(token); err == nil {
+		data.SetToken(v)
+	}
+
+	templateOptions, err := CustomSSHTemplateOptions(p.SSHOptions, data, sshutil.CertificateRequestTemplate)
+	if err != nil {
+		return nil, errs.Wrap(http.StatusInternalServerError, err, "k8ssa.AuthorizeSSHSign")
+	}
+	signOptions := []SignOption{templateOptions}
 
 	return append(signOptions,
-		// Set the default extensions.
-		&sshDefaultExtensionModifier{},
+		// Require type, key-id and principals in the SignSSHOptions.
+		&sshCertOptionsRequireValidator{CertType: true, KeyID: true, Principals: true},
 		// Set the validity bounds if not set.
 		&sshDefaultDuration{p.claimer},
 		// Validate public key

authority/provisioner/sign_ssh_options.go

@@ -299,6 +299,26 @@ func (v sshCertOptionsValidator) Valid(got SignSSHOptions) error {
 	return want.match(got)
 }
 
+// sshCertOptionsRequireValidator defines which elements in the SignSSHOptions are required.
+type sshCertOptionsRequireValidator struct {
+	CertType   bool
+	KeyID      bool
+	Principals bool
+}
+
+func (v sshCertOptionsRequireValidator) Valid(got SignSSHOptions) error {
+	switch {
+	case v.CertType && got.CertType == "":
+		return errors.New("ssh certificate certType cannot be empty")
+	case v.KeyID && got.KeyID == "":
+		return errors.New("ssh certificate keyID cannot be empty")
+	case v.Principals && len(got.Principals) == 0:
+		return errors.New("ssh certificate principals cannot be empty")
+	default:
+		return nil
+	}
+}
+
 type sshCertValidityValidator struct {
 	*Claimer
 }

authority/ssh.go

@@ -206,8 +206,6 @@ func (a *Authority) GetSSHBastion(ctx context.Context, user string, hostname str
 // SignSSH creates a signed SSH certificate with the given public key and options.
 func (a *Authority) SignSSH(ctx context.Context, key ssh.PublicKey, opts provisioner.SignSSHOptions, signOpts ...provisioner.SignOption) (*ssh.Certificate, error) {
 	var (
-		err         error
-		certType    sshutil.CertType
 		certOptions []sshutil.Option
 		mods        []provisioner.SSHCertModifier
 		validators  []provisioner.SSHCertValidator
@@ -216,14 +214,6 @@ func (a *Authority) SignSSH(ctx context.Context, key ssh.PublicKey, opts provisi
 	// Set backdate with the configured value
 	opts.Backdate = a.config.AuthorityConfig.Backdate.Duration
 
-	// Validate certificate type.
-	if opts.CertType != "" {
-		certType, err = sshutil.CertTypeFromString(opts.CertType)
-		if err != nil {
-			return nil, errs.Wrap(http.StatusBadRequest, err, "authority.SignSSH")
-		}
-	}
-
 	for _, op := range signOpts {
 		switch o := op.(type) {
 		// add options to NewCertificate
@@ -251,7 +241,7 @@ func (a *Authority) SignSSH(ctx context.Context, key ssh.PublicKey, opts provisi
 
 	// Simulated certificate request with request options.
 	cr := sshutil.CertificateRequest{
-		Type:       certType,
+		Type:       opts.CertType,
 		KeyID:      opts.KeyID,
 		Principals: opts.Principals,
 		Key:        key,

sshutil/certificate_request.go

@@ -11,7 +11,7 @@ import "golang.org/x/crypto/ssh"
 // passed with the API instead of the validated ones.
 type CertificateRequest struct {
 	Key        ssh.PublicKey
-	Type       CertType
+	Type       string
 	KeyID      string
 	Principals []string
 }

sshutil/templates.go

@@ -143,3 +143,18 @@ const DefaultIIDCertificate = `{
 {{- end }}
 	"extensions": {{ toJson .Extensions }}
 }`
+
+const CertificateRequestTemplate = `{
+	"type": "{{ .Insecure.CR.Type }}",
+	"keyId": "{{ .Insecure.CR.KeyID }}",
+	"principals": {{ toJson .Insecure.CR.Principals }}
+{{- if eq .Insecure.CR.Type "user" }}
+	, "extensions": {
+		"permit-X11-forwarding":   "",
+		"permit-agent-forwarding": "",
+		"permit-port-forwarding":  "",
+		"permit-pty":              "",
+		"permit-user-rc":          ""
+	}
+{{- end }}
+}`