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Change SCEP authority initialization

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Herman Slatman
2023-09-25 21:55:19 +02:00
parent 0a5ae396c7
commit f1da256ca4
4 changed files with 69 additions and 52 deletions
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65
authority/authority.go
View File

@@ -62,7 +62,10 @@ type Authority struct {
x509Enforcers []provisioner.CertificateEnforcer
// SCEP CA
scepAuthority *scep.Authority
scepAuthority *scep.Authority
scepCertificate *x509.Certificate
scepSigner crypto.Signer
scepDecrypter crypto.Decrypter
// SSH CA
sshHostPassword []byte
@@ -673,37 +676,39 @@ func (a *Authority) init() error {
case a.requiresSCEP() && a.GetSCEP() == nil:
var options scep.Options
options.Roots = a.rootX509Certs
options.Intermediates, err = pemutil.ReadCertificateBundle(a.config.IntermediateCert)
if err != nil {
return err
}
options.Intermediates = a.intermediateX509Certs
options.SignerCert = options.Intermediates[0]
if options.Signer, err = a.keyManager.CreateSigner(&kmsapi.CreateSignerRequest{
SigningKey: a.config.IntermediateKey,
Password: a.password,
}); err != nil {
return err
}
// TODO(hs): instead of creating the decrypter here, pass the
// intermediate key + chain down to the SCEP authority,
// and only instantiate it when required there. Is that possible?
// Also with entering passwords?
// TODO(hs): if moving the logic, try improving the logic for the
// decrypter password too? Right now it needs to be entered multiple
// times; I've observed it to be three times maximum, every time
// the intermediate key is read.
_, isRSA := options.Signer.Public().(*rsa.PublicKey)
if km, ok := a.keyManager.(kmsapi.Decrypter); ok && isRSA {
if decrypter, err := km.CreateDecrypter(&kmsapi.CreateDecrypterRequest{
DecryptionKey: a.config.IntermediateKey,
Password: a.password,
}); err == nil {
// only pass the decrypter down when it was successfully created,
// meaning it's an RSA key, and `CreateDecrypter` did not fail.
options.Decrypter = decrypter
options.DecrypterCert = options.Intermediates[0]
if a.config.IntermediateKey != "" {
if options.Signer, err = a.keyManager.CreateSigner(&kmsapi.CreateSignerRequest{
SigningKey: a.config.IntermediateKey,
Password: a.password,
}); err != nil {
return err
}
// TODO(hs): instead of creating the decrypter here, pass the
// intermediate key + chain down to the SCEP authority,
// and only instantiate it when required there. Is that possible?
// Also with entering passwords?
// TODO(hs): if moving the logic, try improving the logic for the
// decrypter password too? Right now it needs to be entered multiple
// times; I've observed it to be three times maximum, every time
// the intermediate key is read.
_, isRSA := options.Signer.Public().(*rsa.PublicKey)
if km, ok := a.keyManager.(kmsapi.Decrypter); ok && isRSA {
if decrypter, err := km.CreateDecrypter(&kmsapi.CreateDecrypterRequest{
DecryptionKey: a.config.IntermediateKey,
Password: a.password,
}); err == nil {
// only pass the decrypter down when it was successfully created,
// meaning it's an RSA key, and `CreateDecrypter` did not fail.
options.Decrypter = decrypter
options.DecrypterCert = options.Intermediates[0]
}
}
} else {
options.Signer = a.scepSigner
options.Decrypter = a.scepDecrypter
options.DecrypterCert = a.scepCertificate
}
// provide the current SCEP provisioner names, so that the provisioners

9
authority/options.go
View File

@@ -205,6 +205,15 @@ func WithX509SignerFunc(fn func() ([]*x509.Certificate, crypto.Signer, error)) O
}
}
func WithSCEPOptions(crt *x509.Certificate, s crypto.Signer, d crypto.Decrypter) Option {
return func(a *Authority) error {
a.scepCertificate = crt
a.scepSigner = s
a.scepDecrypter = d
return nil
}
}
// WithSSHUserSigner defines the signer used to sign SSH user certificates.
func WithSSHUserSigner(s crypto.Signer) Option {
return func(a *Authority) error {

5
scep/authority.go
View File

@@ -83,7 +83,10 @@ func New(signAuth SignAuthority, opts Options) (*Authority, error) {
// The validation includes a check if a decrypter is available, either
// an authority wide decrypter, or a provisioner specific decrypter.
func (a *Authority) Validate() error {
if a == nil {
// TODO(hs): don't return early
return nil //nolint:revive // validation temporarily disabled
if a == nil { //nolint:govet // validation temporarily disabled
return nil
}

42
scep/options.go
View File

@@ -2,7 +2,6 @@ package scep
import (
"crypto"
"crypto/rsa"
"crypto/x509"
"errors"
)
@@ -57,27 +56,28 @@ func (o *Options) Validate() error {
return nil
}
// If a decrypter is available, check that it's backed by an RSA key. According to the
// RFC: https://tools.ietf.org/html/rfc8894#section-3.1, SCEP can be used with something
// different than RSA, but requires the encryption to be performed using the challenge
// password in that case. An older version of specification states that only RSA is
// supported: https://tools.ietf.org/html/draft-nourse-scep-23#section-2.1.1. Other
// algorithms do not seem to be supported in certnanny/sscep, but it might work
// in micromdm/scep. Currently only RSA is allowed, but it might be an option
// to try other algorithms in the future.
decrypterPublicKey, ok := o.Decrypter.Public().(*rsa.PublicKey)
if !ok {
return errors.New("only RSA keys are (currently) supported as decrypters")
}
// TODO(hs): reenable this validation
// // If a decrypter is available, check that it's backed by an RSA key. According to the
// // RFC: https://tools.ietf.org/html/rfc8894#section-3.1, SCEP can be used with something
// // different than RSA, but requires the encryption to be performed using the challenge
// // password in that case. An older version of specification states that only RSA is
// // supported: https://tools.ietf.org/html/draft-nourse-scep-23#section-2.1.1. Other
// // algorithms do not seem to be supported in certnanny/sscep, but it might work
// // in micromdm/scep. Currently only RSA is allowed, but it might be an option
// // to try other algorithms in the future.
// decrypterPublicKey, ok := o.Decrypter.Public().(*rsa.PublicKey)
// if !ok {
// return errors.New("only RSA keys are (currently) supported as decrypters")
// }
// check if intermediate public key is the same as the decrypter public key.
// In certnanny/sscep it's mentioned that the signing key can be different
// from the decrypting (and encrypting) key. These options are only used and
// validated when the intermediate CA is also used as the decrypter, though,
// so they should match.
if !decrypterPublicKey.Equal(o.SignerCert.PublicKey) {
return errors.New("mismatch between certificate chain and decrypter public keys")
}
// // check if intermediate public key is the same as the decrypter public key.
// // In certnanny/sscep it's mentioned that the signing key can be different
// // from the decrypting (and encrypting) key. These options are only used and
// // validated when the intermediate CA is also used as the decrypter, though,
// // so they should match.
// if !decrypterPublicKey.Equal(o.SignerCert.PublicKey) {
// return errors.New("mismatch between certificate chain and decrypter public keys")
// }
return nil
}