Set default SSH options if no user options are given.

authority/provisioner/aws.go

@@ -448,13 +448,18 @@ func (p *AWS) authorizeSSHSign(claims *awsPayload) ([]SignOption, error) {
 		sshCertificateKeyIDModifier(claims.Subject),
 	}
 
-	signOptions = append(signOptions, &sshCertificateOptionsValidator{&SSHOptions{
+	// Default to host + known IPs/hostnames
+	defaults := SSHOptions{
 		CertType: SSHHostCert,
 		Principals: []string{
 			doc.PrivateIP,
 			fmt.Sprintf("ip-%s.%s.compute.internal", strings.Replace(doc.PrivateIP, ".", "-", -1), doc.Region),
 		},
-	}})
+	}
+	// Validate user options
+	signOptions = append(signOptions, sshCertificateOptionsValidator(defaults))
+	// Set defaults if not given as user options
+	signOptions = append(signOptions, sshCertificateDefaultsModifier(defaults))
 
 	return append(signOptions,
 		// set the default extensions

authority/provisioner/azure.go

@@ -308,10 +308,15 @@ func (p *Azure) authorizeSSHSign(claims azurePayload, name string) ([]SignOption
 		sshCertificateKeyIDModifier(name),
 	}
 
-	signOptions = append(signOptions, &sshCertificateOptionsValidator{&SSHOptions{
+	// Default to host + known hostnames
+	defaults := SSHOptions{
 		CertType:   SSHHostCert,
 		Principals: []string{name},
-	}})
+	}
+	// Validate user options
+	signOptions = append(signOptions, sshCertificateOptionsValidator(defaults))
+	// Set defaults if not given as user options
+	signOptions = append(signOptions, sshCertificateDefaultsModifier(defaults))
 
 	return append(signOptions,
 		// set the default extensions

authority/provisioner/gcp.go

@@ -360,13 +360,18 @@ func (p *GCP) authorizeSSHSign(claims *gcpPayload) ([]SignOption, error) {
 		sshCertificateKeyIDModifier(ce.InstanceName),
 	}
 
-	signOptions = append(signOptions, &sshCertificateOptionsValidator{&SSHOptions{
+	// Default to host + known hostnames
+	defaults := SSHOptions{
 		CertType: SSHHostCert,
 		Principals: []string{
 			fmt.Sprintf("%s.c.%s.internal", ce.InstanceName, ce.ProjectID),
 			fmt.Sprintf("%s.%s.c.%s.internal", ce.InstanceName, ce.Zone, ce.ProjectID),
 		},
-	}})
+	}
+	// Validate user options
+	signOptions = append(signOptions, sshCertificateOptionsValidator(defaults))
+	// Set defaults if not given as user options
+	signOptions = append(signOptions, sshCertificateDefaultsModifier(defaults))
 
 	return append(signOptions,
 		// set the default extensions

authority/provisioner/jwk.go

@@ -178,7 +178,7 @@ func (p *JWK) authorizeSSHSign(claims *jwtPayload) ([]SignOption, error) {
 	opts := claims.Step.SSH
 	signOptions := []SignOption{
 		// validates user's SSHOptions with the ones in the token
-		&sshCertificateOptionsValidator{opts},
+		sshCertificateOptionsValidator(*opts),
 		// set the key id to the token subject
 		sshCertificateKeyIDModifier(claims.Subject),
 	}
@@ -197,6 +197,9 @@ func (p *JWK) authorizeSSHSign(claims *jwtPayload) ([]SignOption, error) {
 		signOptions = append(signOptions, sshCertificateValidBeforeModifier(opts.ValidBefore.RelativeTime(t).Unix()))
 	}
 
+	// Default to a user certificate with no principals if not set
+	signOptions = append(signOptions, sshCertificateDefaultsModifier{CertType: SSHUserCert})
+
 	return append(signOptions,
 		// set the default extensions
 		&sshDefaultExtensionModifier{},

authority/provisioner/oidc.go

@@ -303,20 +303,25 @@ func (o *OIDC) authorizeSSHSign(claims *openIDPayload) ([]SignOption, error) {
 		sshCertificateKeyIDModifier(claims.Email),
 	}
 
-	// Non-admins are only able to sign user certificates
-	if o.IsAdmin(claims.Email) {
-		signOptions = append(signOptions, &sshCertificateOptionsValidator{})
-	} else {
-		name := SanitizeSSHUserPrincipal(claims.Email)
-		if !sshUserRegex.MatchString(name) {
-			return nil, errors.Errorf("invalid principal '%s' from email address '%s'", name, claims.Email)
-		}
-		signOptions = append(signOptions, &sshCertificateOptionsValidator{&SSHOptions{
-			CertType:   SSHUserCert,
-			Principals: []string{name},
-		}})
+	name := SanitizeSSHUserPrincipal(claims.Email)
+	if !sshUserRegex.MatchString(name) {
+		return nil, errors.Errorf("invalid principal '%s' from email address '%s'", name, claims.Email)
+	}
+
+	// Admin users will default to user + name but they can be changed by the
+	// user options. Non-admins are only able to sign user certificates.
+	defaults := SSHOptions{
+		CertType:   SSHUserCert,
+		Principals: []string{name},
 	}
 
+	if !o.IsAdmin(claims.Email) {
+		signOptions = append(signOptions, sshCertificateOptionsValidator(defaults))
+	}
+
+	// Default to a user with name as principal if not set
+	signOptions = append(signOptions, sshCertificateDefaultsModifier(defaults))
+
 	return append(signOptions,
 		// set the default extensions
 		&sshDefaultExtensionModifier{},

authority/provisioner/sign_ssh_options.go

@@ -143,6 +143,27 @@ func (m sshCertificateValidBeforeModifier) Modify(cert *ssh.Certificate) error {
 	return nil
 }
 
+// sshCertificateDefaultModifier implements a SSHCertificateModifier that
+// modifies the certificate with the given options if they are not set.
+type sshCertificateDefaultsModifier SSHOptions
+
+// Modify implements the SSHCertificateModifier interface.
+func (m sshCertificateDefaultsModifier) Modify(cert *ssh.Certificate) error {
+	if cert.CertType == 0 {
+		cert.CertType = sshCertTypeUInt32(m.CertType)
+	}
+	if len(cert.ValidPrincipals) == 0 {
+		cert.ValidPrincipals = m.Principals
+	}
+	if cert.ValidAfter == 0 && !m.ValidAfter.IsZero() {
+		cert.ValidAfter = uint64(m.ValidAfter.Unix())
+	}
+	if cert.ValidBefore == 0 && !m.ValidBefore.IsZero() {
+		cert.ValidBefore = uint64(m.ValidBefore.Unix())
+	}
+	return nil
+}
+
 // sshDefaultExtensionModifier implements an SSHCertificateModifier that sets
 // the default extensions in an SSH certificate.
 type sshDefaultExtensionModifier struct{}
@@ -212,17 +233,13 @@ func (m *sshCertificateValidityModifier) Modify(cert *ssh.Certificate) error {
 
 // sshCertificateOptionsValidator validates the user SSHOptions with the ones
 // usually present in the token.
-type sshCertificateOptionsValidator struct {
-	Want *SSHOptions
-}
+type sshCertificateOptionsValidator SSHOptions
 
 // Valid implements SSHCertificateOptionsValidator and returns nil if both
 // SSHOptions match.
-func (v *sshCertificateOptionsValidator) Valid(got SSHOptions) error {
-	if v.Want == nil {
-		return nil
-	}
-	return v.Want.match(got)
+func (v sshCertificateOptionsValidator) Valid(got SSHOptions) error {
+	want := SSHOptions(v)
+	return want.match(got)
 }
 
 // sshCertificateDefaultValidator implements a simple validator for all the