certificates/authority/provisioner/sign_ssh_options.go

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package provisioner
import (
"time"
"github.com/pkg/errors"
"golang.org/x/crypto/ssh"
)
const (
// SSHUserCert is the string used to represent ssh.UserCert.
SSHUserCert = "user"
// SSHHostCert is the string used to represent ssh.HostCert.
SSHHostCert = "host"
)
// SSHCertificateModifier is the interface used to change properties in an SSH
// certificate.
type SSHCertificateModifier interface {
SignOption
Modify(cert *ssh.Certificate) error
}
// SSHCertificateOptionModifier is the interface used to add custom options used
// to modify the SSH certificate.
type SSHCertificateOptionModifier interface {
SignOption
Option(o SSHOptions) SSHCertificateModifier
}
// SSHCertificateValidator is the interface used to validate an SSH certificate.
type SSHCertificateValidator interface {
SignOption
Valid(cert *ssh.Certificate) error
}
// SSHCertificateOptionsValidator is the interface used to validate the custom
// options used to modify the SSH certificate.
type SSHCertificateOptionsValidator interface {
SignOption
Valid(got SSHOptions) error
}
// SSHOptions contains the options that can be passed to the SignSSH method.
type SSHOptions struct {
CertType string `json:"certType"`
Principals []string `json:"principals"`
ValidAfter TimeDuration `json:"validAfter,omitempty"`
ValidBefore TimeDuration `json:"validBefore,omitempty"`
}
// Type returns the uint32 representation of the CertType.
func (o SSHOptions) Type() uint32 {
return sshCertTypeUInt32(o.CertType)
}
// Modify implements SSHCertificateModifier and sets the SSHOption in the ssh.Certificate.
func (o SSHOptions) Modify(cert *ssh.Certificate) error {
switch o.CertType {
case "": // ignore
case SSHUserCert:
cert.CertType = ssh.UserCert
case SSHHostCert:
cert.CertType = ssh.HostCert
default:
return errors.Errorf("ssh certificate has an unknown type: %s", o.CertType)
}
cert.ValidPrincipals = o.Principals
if !o.ValidAfter.IsZero() {
cert.ValidAfter = uint64(o.ValidAfter.Time().Unix())
}
if !o.ValidBefore.IsZero() {
cert.ValidBefore = uint64(o.ValidBefore.Time().Unix())
}
if cert.ValidAfter > 0 && cert.ValidBefore > 0 && cert.ValidAfter > cert.ValidBefore {
return errors.New("ssh certificate valid after cannot be greater than valid before")
}
return nil
}
// match compares two SSHOptions and return an error if they don't match. It
// ignores zero values.
func (o SSHOptions) match(got SSHOptions) error {
if o.CertType != "" && got.CertType != "" && o.CertType != got.CertType {
return errors.Errorf("ssh certificate type does not match - got %v, want %v", got.CertType, o.CertType)
}
if len(o.Principals) > 0 && len(got.Principals) > 0 && !containsAllMembers(o.Principals, got.Principals) {
return errors.Errorf("ssh certificate principals does not match - got %v, want %v", got.Principals, o.Principals)
}
if !o.ValidAfter.IsZero() && !got.ValidAfter.IsZero() && !o.ValidAfter.Equal(&got.ValidAfter) {
return errors.Errorf("ssh certificate valid after does not match - got %v, want %v", got.ValidAfter, o.ValidAfter)
}
if !o.ValidBefore.IsZero() && !got.ValidBefore.IsZero() && !o.ValidBefore.Equal(&got.ValidBefore) {
return errors.Errorf("ssh certificate valid before does not match - got %v, want %v", got.ValidBefore, o.ValidBefore)
}
return nil
}
// sshCertificateKeyIDModifier is an SSHCertificateModifier that sets the given
// Key ID in the SSH certificate.
type sshCertificateKeyIDModifier string
func (m sshCertificateKeyIDModifier) Modify(cert *ssh.Certificate) error {
cert.KeyId = string(m)
return nil
}
// sshCertificateCertTypeModifier is an SSHCertificateModifier that sets the
// certificate type to the SSH certificate.
type sshCertificateCertTypeModifier string
func (m sshCertificateCertTypeModifier) Modify(cert *ssh.Certificate) error {
cert.CertType = sshCertTypeUInt32(string(m))
return nil
}
// sshCertificatePrincipalsModifier is an SSHCertificateModifier that sets the
// principals to the SSH certificate.
type sshCertificatePrincipalsModifier []string
func (m sshCertificatePrincipalsModifier) Modify(cert *ssh.Certificate) error {
cert.ValidPrincipals = []string(m)
return nil
}
// sshCertificateValidAfterModifier is an SSHCertificateModifier that sets the
// ValidAfter in the SSH certificate.
type sshCertificateValidAfterModifier uint64
func (m sshCertificateValidAfterModifier) Modify(cert *ssh.Certificate) error {
cert.ValidAfter = uint64(m)
return nil
}
// sshCertificateValidBeforeModifier is an SSHCertificateModifier that sets the
// ValidBefore in the SSH certificate.
type sshCertificateValidBeforeModifier uint64
func (m sshCertificateValidBeforeModifier) Modify(cert *ssh.Certificate) error {
cert.ValidBefore = uint64(m)
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{}
func (m *sshDefaultExtensionModifier) Modify(cert *ssh.Certificate) error {
switch cert.CertType {
// Default to no extensions for HostCert.
case ssh.HostCert:
return nil
case ssh.UserCert:
if cert.Extensions == nil {
cert.Extensions = make(map[string]string)
}
cert.Extensions["permit-X11-forwarding"] = ""
cert.Extensions["permit-agent-forwarding"] = ""
cert.Extensions["permit-port-forwarding"] = ""
cert.Extensions["permit-pty"] = ""
cert.Extensions["permit-user-rc"] = ""
return nil
default:
return errors.New("ssh certificate type has not been set or is invalid")
}
}
// sshCertificateValidityModifier is a SSHCertificateModifier checks the
// validity bounds, setting them if they are not provided. It will fail if a
// CertType has not been set or is not valid.
type sshCertificateValidityModifier struct {
*Claimer
}
func (m *sshCertificateValidityModifier) Modify(cert *ssh.Certificate) error {
var d, min, max time.Duration
switch cert.CertType {
case ssh.UserCert:
d = m.DefaultUserSSHCertDuration()
min = m.MinUserSSHCertDuration()
max = m.MaxUserSSHCertDuration()
case ssh.HostCert:
d = m.DefaultHostSSHCertDuration()
min = m.MinHostSSHCertDuration()
max = m.MaxHostSSHCertDuration()
case 0:
return errors.New("ssh certificate type has not been set")
default:
return errors.Errorf("unknown ssh certificate type %d", cert.CertType)
}
if cert.ValidAfter == 0 {
cert.ValidAfter = uint64(now().Unix())
}
if cert.ValidBefore == 0 {
t := time.Unix(int64(cert.ValidAfter), 0)
cert.ValidBefore = uint64(t.Add(d).Unix())
}
diff := time.Duration(cert.ValidBefore-cert.ValidAfter) * time.Second
switch {
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case diff < min:
return errors.Errorf("ssh certificate duration cannot be lower than %s", min)
case diff > max:
return errors.Errorf("ssh certificate duration cannot be greater than %s", max)
default:
return nil
}
}
// sshCertificateOptionsValidator validates the user SSHOptions with the ones
// usually present in the token.
type sshCertificateOptionsValidator SSHOptions
// Valid implements SSHCertificateOptionsValidator and returns nil if both
// SSHOptions match.
func (v sshCertificateOptionsValidator) Valid(got SSHOptions) error {
want := SSHOptions(v)
return want.match(got)
}
// sshCertificateDefaultValidator implements a simple validator for all the
// fields in the SSH certificate.
type sshCertificateDefaultValidator struct{}
// Valid returns an error if the given certificate does not contain the necessary fields.
func (v *sshCertificateDefaultValidator) Valid(cert *ssh.Certificate) error {
switch {
case len(cert.Nonce) == 0:
return errors.New("ssh certificate nonce cannot be empty")
case cert.Key == nil:
return errors.New("ssh certificate key cannot be nil")
case cert.Serial == 0:
return errors.New("ssh certificate serial cannot be 0")
case cert.CertType != ssh.UserCert && cert.CertType != ssh.HostCert:
return errors.Errorf("ssh certificate has an unknown type: %d", cert.CertType)
case cert.KeyId == "":
return errors.New("ssh certificate key id cannot be empty")
case len(cert.ValidPrincipals) == 0:
return errors.New("ssh certificate valid principals cannot be empty")
case cert.ValidAfter == 0:
return errors.New("ssh certificate valid after cannot be 0")
case cert.ValidBefore == 0:
return errors.New("ssh certificate valid before cannot be 0")
case cert.CertType == ssh.UserCert && len(cert.Extensions) == 0:
return errors.New("ssh certificate extensions cannot be empty")
case cert.SignatureKey == nil:
return errors.New("ssh certificate signature key cannot be nil")
case cert.Signature == nil:
return errors.New("ssh certificate signature cannot be nil")
default:
return nil
}
}
// sshCertTypeUInt32
func sshCertTypeUInt32(ct string) uint32 {
switch ct {
case SSHUserCert:
return ssh.UserCert
case SSHHostCert:
return ssh.HostCert
default:
return 0
}
}
// containsAllMembers reports whether all members of subgroup are within group.
func containsAllMembers(group, subgroup []string) bool {
lg, lsg := len(group), len(subgroup)
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if lsg > lg || (lg > 0 && lsg == 0) {
return false
}
visit := make(map[string]struct{}, lg)
for i := 0; i < lg; i++ {
visit[group[i]] = struct{}{}
}
for i := 0; i < lsg; i++ {
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if _, ok := visit[subgroup[i]]; !ok {
return false
}
}
return true
}