certificates/authority/tls.go

676 lines
22 KiB
Go

package authority
import (
"context"
"crypto"
"crypto/tls"
"crypto/x509"
"encoding/asn1"
"encoding/base64"
"encoding/json"
"encoding/pem"
"fmt"
"net"
"net/http"
"strings"
"time"
"github.com/pkg/errors"
"golang.org/x/crypto/ssh"
"go.step.sm/crypto/jose"
"go.step.sm/crypto/keyutil"
"go.step.sm/crypto/pemutil"
"go.step.sm/crypto/x509util"
"github.com/smallstep/certificates/authority/config"
"github.com/smallstep/certificates/authority/provisioner"
casapi "github.com/smallstep/certificates/cas/apiv1"
"github.com/smallstep/certificates/db"
"github.com/smallstep/certificates/errs"
"github.com/smallstep/certificates/policy"
)
// GetTLSOptions returns the tls options configured.
func (a *Authority) GetTLSOptions() *config.TLSOptions {
return a.config.TLS
}
var oidAuthorityKeyIdentifier = asn1.ObjectIdentifier{2, 5, 29, 35}
var oidSubjectKeyIdentifier = asn1.ObjectIdentifier{2, 5, 29, 14}
func withDefaultASN1DN(def *config.ASN1DN) provisioner.CertificateModifierFunc {
return func(crt *x509.Certificate, opts provisioner.SignOptions) error {
if def == nil {
return errors.New("default ASN1DN template cannot be nil")
}
if len(crt.Subject.Country) == 0 && def.Country != "" {
crt.Subject.Country = append(crt.Subject.Country, def.Country)
}
if len(crt.Subject.Organization) == 0 && def.Organization != "" {
crt.Subject.Organization = append(crt.Subject.Organization, def.Organization)
}
if len(crt.Subject.OrganizationalUnit) == 0 && def.OrganizationalUnit != "" {
crt.Subject.OrganizationalUnit = append(crt.Subject.OrganizationalUnit, def.OrganizationalUnit)
}
if len(crt.Subject.Locality) == 0 && def.Locality != "" {
crt.Subject.Locality = append(crt.Subject.Locality, def.Locality)
}
if len(crt.Subject.Province) == 0 && def.Province != "" {
crt.Subject.Province = append(crt.Subject.Province, def.Province)
}
if len(crt.Subject.StreetAddress) == 0 && def.StreetAddress != "" {
crt.Subject.StreetAddress = append(crt.Subject.StreetAddress, def.StreetAddress)
}
if crt.Subject.SerialNumber == "" && def.SerialNumber != "" {
crt.Subject.SerialNumber = def.SerialNumber
}
if crt.Subject.CommonName == "" && def.CommonName != "" {
crt.Subject.CommonName = def.CommonName
}
return nil
}
}
// Sign creates a signed certificate from a certificate signing request.
func (a *Authority) Sign(csr *x509.CertificateRequest, signOpts provisioner.SignOptions, extraOpts ...provisioner.SignOption) ([]*x509.Certificate, error) {
var (
certOptions []x509util.Option
certValidators []provisioner.CertificateValidator
certModifiers []provisioner.CertificateModifier
certEnforcers []provisioner.CertificateEnforcer
)
opts := []interface{}{errs.WithKeyVal("csr", csr), errs.WithKeyVal("signOptions", signOpts)}
if err := csr.CheckSignature(); err != nil {
return nil, errs.ApplyOptions(
errs.BadRequestErr(err, "invalid certificate request"),
opts...,
)
}
// Set backdate with the configured value
signOpts.Backdate = a.config.AuthorityConfig.Backdate.Duration
var prov provisioner.Interface
for _, op := range extraOpts {
switch k := op.(type) {
// Capture current provisioner
case provisioner.Interface:
prov = k
// Adds new options to NewCertificate
case provisioner.CertificateOptions:
certOptions = append(certOptions, k.Options(signOpts)...)
// Validate the given certificate request.
case provisioner.CertificateRequestValidator:
if err := k.Valid(csr); err != nil {
return nil, errs.ApplyOptions(
errs.ForbiddenErr(err, "error validating certificate"),
opts...,
)
}
// Validates the unsigned certificate template.
case provisioner.CertificateValidator:
certValidators = append(certValidators, k)
// Modifies a certificate before validating it.
case provisioner.CertificateModifier:
certModifiers = append(certModifiers, k)
// Modifies a certificate after validating it.
case provisioner.CertificateEnforcer:
certEnforcers = append(certEnforcers, k)
default:
return nil, errs.InternalServer("authority.Sign; invalid extra option type %T", append([]interface{}{k}, opts...)...)
}
}
cert, err := x509util.NewCertificate(csr, certOptions...)
if err != nil {
if _, ok := err.(*x509util.TemplateError); ok {
return nil, errs.ApplyOptions(
errs.BadRequestErr(err, err.Error()),
errs.WithKeyVal("csr", csr),
errs.WithKeyVal("signOptions", signOpts),
)
}
// explicitly check for unmarshaling errors, which are most probably caused by JSON template (syntax) errors
if strings.HasPrefix(err.Error(), "error unmarshaling certificate") {
return nil, errs.InternalServerErr(templatingError(err),
errs.WithKeyVal("csr", csr),
errs.WithKeyVal("signOptions", signOpts),
errs.WithMessage("error applying certificate template"),
)
}
return nil, errs.Wrap(http.StatusInternalServerError, err, "authority.Sign", opts...)
}
// Certificate modifiers before validation
leaf := cert.GetCertificate()
// Set default subject
if err := withDefaultASN1DN(a.config.AuthorityConfig.Template).Modify(leaf, signOpts); err != nil {
return nil, errs.ApplyOptions(
errs.ForbiddenErr(err, "error creating certificate"),
opts...,
)
}
for _, m := range certModifiers {
if err := m.Modify(leaf, signOpts); err != nil {
return nil, errs.ApplyOptions(
errs.ForbiddenErr(err, "error creating certificate"),
opts...,
)
}
}
// Certificate validation.
for _, v := range certValidators {
if err := v.Valid(leaf, signOpts); err != nil {
return nil, errs.ApplyOptions(
errs.ForbiddenErr(err, "error validating certificate"),
opts...,
)
}
}
// Certificate modifiers after validation
for _, m := range certEnforcers {
if err := m.Enforce(leaf); err != nil {
return nil, errs.ApplyOptions(
errs.ForbiddenErr(err, "error creating certificate"),
opts...,
)
}
}
// Process injected modifiers after validation
for _, m := range a.x509Enforcers {
if err := m.Enforce(leaf); err != nil {
return nil, errs.ApplyOptions(
errs.ForbiddenErr(err, "error creating certificate"),
opts...,
)
}
}
// Check if authority is allowed to sign the certificate
var allowedToSign bool
if allowedToSign, err = a.isAllowedToSign(leaf); err != nil {
var pe *policy.NamePolicyError
if errors.As(err, &pe) && pe.Reason == policy.NotAllowed {
return nil, errs.ApplyOptions(&errs.Error{
// NOTE: custom forbidden error, so that denied name is sent to client
// as well as shown in the logs.
Status: http.StatusForbidden,
Err: fmt.Errorf("authority not allowed to sign: %w", err),
Msg: fmt.Sprintf("The request was forbidden by the certificate authority: %s", err.Error()),
}, opts...)
}
return nil, errs.InternalServerErr(err,
errs.WithKeyVal("csr", csr),
errs.WithKeyVal("signOptions", signOpts),
errs.WithMessage("error creating certificate"),
)
}
if !allowedToSign {
return nil, errs.ApplyOptions(
errs.ForbiddenErr(errors.New("authority not allowed to sign"), "error creating certificate"),
opts...,
)
}
// Sign certificate
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,
})
if err != nil {
return nil, errs.Wrap(http.StatusInternalServerError, err, "authority.Sign; error creating certificate", opts...)
}
fullchain := append([]*x509.Certificate{resp.Certificate}, resp.CertificateChain...)
if err = a.storeCertificate(prov, fullchain); err != nil {
if err != db.ErrNotImplemented {
return nil, errs.Wrap(http.StatusInternalServerError, err,
"authority.Sign; error storing certificate in db", opts...)
}
}
return fullchain, nil
}
// isAllowedToSign checks if the Authority is allowed to sign the X.509 certificate.
func (a *Authority) isAllowedToSign(cert *x509.Certificate) (bool, error) {
// if no policy is configured, the cert is implicitly allowed
if a.x509Policy == nil {
return true, nil
}
return a.x509Policy.IsX509CertificateAllowed(cert)
}
// AreSANsAllowed evaluates the provided sans against the
// authority X.509 policy.
func (a *Authority) AreSANsAllowed(ctx context.Context, sans []string) error {
// no policy configured; return early
if a.x509Policy == nil {
return nil
}
// evaluate the X.509 policy for the provided sans
var err error
_, err = a.x509Policy.AreSANsAllowed(sans)
return err
}
// Renew creates a new Certificate identical to the old certificate, except
// with a validity window that begins 'now'.
func (a *Authority) Renew(oldCert *x509.Certificate) ([]*x509.Certificate, error) {
return a.Rekey(oldCert, nil)
}
// Rekey is used for rekeying and renewing based on the public key.
// If the public key is 'nil' then it's assumed that the cert should be renewed
// using the existing public key. If the public key is not 'nil' then it's
// assumed that the cert should be rekeyed.
// For both Rekey and Renew all other attributes of the new certificate should
// match the old certificate. The exceptions are 'AuthorityKeyId' (which may
// have changed), 'SubjectKeyId' (different in case of rekey), and
// 'NotBefore/NotAfter' (the validity duration of the new certificate should be
// equal to the old one, but starting 'now').
func (a *Authority) Rekey(oldCert *x509.Certificate, pk crypto.PublicKey) ([]*x509.Certificate, error) {
isRekey := (pk != nil)
opts := []interface{}{errs.WithKeyVal("serialNumber", oldCert.SerialNumber.String())}
// Check step provisioner extensions
if err := a.authorizeRenew(oldCert); err != nil {
return nil, errs.Wrap(http.StatusInternalServerError, err, "authority.Rekey", opts...)
}
// Durations
backdate := a.config.AuthorityConfig.Backdate.Duration
duration := oldCert.NotAfter.Sub(oldCert.NotBefore)
lifetime := duration - backdate
// Create new certificate from previous values.
// Issuer, NotBefore, NotAfter and SubjectKeyId will be set by the CAS.
newCert := &x509.Certificate{
Subject: oldCert.Subject,
KeyUsage: oldCert.KeyUsage,
UnhandledCriticalExtensions: oldCert.UnhandledCriticalExtensions,
ExtKeyUsage: oldCert.ExtKeyUsage,
UnknownExtKeyUsage: oldCert.UnknownExtKeyUsage,
BasicConstraintsValid: oldCert.BasicConstraintsValid,
IsCA: oldCert.IsCA,
MaxPathLen: oldCert.MaxPathLen,
MaxPathLenZero: oldCert.MaxPathLenZero,
OCSPServer: oldCert.OCSPServer,
IssuingCertificateURL: oldCert.IssuingCertificateURL,
PermittedDNSDomainsCritical: oldCert.PermittedDNSDomainsCritical,
PermittedEmailAddresses: oldCert.PermittedEmailAddresses,
DNSNames: oldCert.DNSNames,
EmailAddresses: oldCert.EmailAddresses,
IPAddresses: oldCert.IPAddresses,
URIs: oldCert.URIs,
PermittedDNSDomains: oldCert.PermittedDNSDomains,
ExcludedDNSDomains: oldCert.ExcludedDNSDomains,
PermittedIPRanges: oldCert.PermittedIPRanges,
ExcludedIPRanges: oldCert.ExcludedIPRanges,
ExcludedEmailAddresses: oldCert.ExcludedEmailAddresses,
PermittedURIDomains: oldCert.PermittedURIDomains,
ExcludedURIDomains: oldCert.ExcludedURIDomains,
CRLDistributionPoints: oldCert.CRLDistributionPoints,
PolicyIdentifiers: oldCert.PolicyIdentifiers,
}
if isRekey {
newCert.PublicKey = pk
} else {
newCert.PublicKey = oldCert.PublicKey
}
// Copy all extensions except:
//
// 1. Authority Key Identifier - This one might be different if we rotate
// the intermediate certificate and it will cause a TLS bad certificate
// error.
//
// 2. Subject Key Identifier, if rekey - For rekey, SubjectKeyIdentifier
// extension will be calculated for the new public key by
// x509util.CreateCertificate()
for _, ext := range oldCert.Extensions {
if ext.Id.Equal(oidAuthorityKeyIdentifier) {
continue
}
if ext.Id.Equal(oidSubjectKeyIdentifier) && isRekey {
newCert.SubjectKeyId = nil
continue
}
newCert.ExtraExtensions = append(newCert.ExtraExtensions, ext)
}
resp, err := a.x509CAService.RenewCertificate(&casapi.RenewCertificateRequest{
Template: newCert,
Lifetime: lifetime,
Backdate: backdate,
})
if err != nil {
return nil, errs.Wrap(http.StatusInternalServerError, err, "authority.Rekey", opts...)
}
fullchain := append([]*x509.Certificate{resp.Certificate}, resp.CertificateChain...)
if err = a.storeRenewedCertificate(oldCert, fullchain); err != nil {
if err != db.ErrNotImplemented {
return nil, errs.Wrap(http.StatusInternalServerError, err, "authority.Rekey; error storing certificate in db", opts...)
}
}
return fullchain, nil
}
// storeCertificate allows to use an extension of the db.AuthDB interface that
// can log the full chain of certificates.
//
// TODO: at some point we should replace the db.AuthDB interface to implement
// `StoreCertificate(...*x509.Certificate) error` instead of just
// `StoreCertificate(*x509.Certificate) error`.
func (a *Authority) storeCertificate(prov provisioner.Interface, fullchain []*x509.Certificate) error {
type linkedChainStorer interface {
StoreCertificateChain(provisioner.Interface, ...*x509.Certificate) error
}
type certificateChainStorer interface {
StoreCertificateChain(...*x509.Certificate) error
}
// Store certificate in linkedca
switch s := a.adminDB.(type) {
case linkedChainStorer:
return s.StoreCertificateChain(prov, fullchain...)
case certificateChainStorer:
return s.StoreCertificateChain(fullchain...)
}
// Store certificate in local db
switch s := a.db.(type) {
case linkedChainStorer:
return s.StoreCertificateChain(prov, fullchain...)
case certificateChainStorer:
return s.StoreCertificateChain(fullchain...)
default:
return a.db.StoreCertificate(fullchain[0])
}
}
// storeRenewedCertificate allows to use an extension of the db.AuthDB interface
// that can log if a certificate has been renewed or rekeyed.
//
// TODO: at some point we should implement this in the standard implementation.
func (a *Authority) storeRenewedCertificate(oldCert *x509.Certificate, fullchain []*x509.Certificate) error {
type renewedCertificateChainStorer interface {
StoreRenewedCertificate(*x509.Certificate, ...*x509.Certificate) error
}
// Store certificate in linkedca
if s, ok := a.adminDB.(renewedCertificateChainStorer); ok {
return s.StoreRenewedCertificate(oldCert, fullchain...)
}
// Store certificate in local db
if s, ok := a.db.(renewedCertificateChainStorer); ok {
return s.StoreRenewedCertificate(oldCert, fullchain...)
}
return a.db.StoreCertificate(fullchain[0])
}
// RevokeOptions are the options for the Revoke API.
type RevokeOptions struct {
Serial string
Reason string
ReasonCode int
PassiveOnly bool
MTLS bool
ACME bool
Crt *x509.Certificate
OTT string
}
// Revoke revokes a certificate.
//
// NOTE: Only supports passive revocation - prevent existing certificates from
// being renewed.
//
// TODO: Add OCSP and CRL support.
func (a *Authority) Revoke(ctx context.Context, revokeOpts *RevokeOptions) error {
opts := []interface{}{
errs.WithKeyVal("serialNumber", revokeOpts.Serial),
errs.WithKeyVal("reasonCode", revokeOpts.ReasonCode),
errs.WithKeyVal("reason", revokeOpts.Reason),
errs.WithKeyVal("passiveOnly", revokeOpts.PassiveOnly),
errs.WithKeyVal("MTLS", revokeOpts.MTLS),
errs.WithKeyVal("ACME", revokeOpts.ACME),
errs.WithKeyVal("context", provisioner.MethodFromContext(ctx).String()),
}
if revokeOpts.MTLS || revokeOpts.ACME {
opts = append(opts, errs.WithKeyVal("certificate", base64.StdEncoding.EncodeToString(revokeOpts.Crt.Raw)))
} else {
opts = append(opts, errs.WithKeyVal("token", revokeOpts.OTT))
}
rci := &db.RevokedCertificateInfo{
Serial: revokeOpts.Serial,
ReasonCode: revokeOpts.ReasonCode,
Reason: revokeOpts.Reason,
MTLS: revokeOpts.MTLS,
ACME: revokeOpts.ACME,
RevokedAt: time.Now().UTC(),
}
var (
p provisioner.Interface
err error
)
// If not mTLS nor ACME, then get the TokenID of the token.
if !(revokeOpts.MTLS || revokeOpts.ACME) {
token, err := jose.ParseSigned(revokeOpts.OTT)
if err != nil {
return errs.Wrap(http.StatusUnauthorized, err,
"authority.Revoke; error parsing token", opts...)
}
// Get claims w/out verification.
var claims Claims
if err = token.UnsafeClaimsWithoutVerification(&claims); err != nil {
return errs.Wrap(http.StatusUnauthorized, err, "authority.Revoke", opts...)
}
// This method will also validate the audiences for JWK provisioners.
p, err = a.LoadProvisionerByToken(token, &claims.Claims)
if err != nil {
return err
}
rci.ProvisionerID = p.GetID()
rci.TokenID, err = p.GetTokenID(revokeOpts.OTT)
if err != nil && !errors.Is(err, provisioner.ErrAllowTokenReuse) {
return errs.Wrap(http.StatusInternalServerError, err,
"authority.Revoke; could not get ID for token")
}
opts = append(opts,
errs.WithKeyVal("provisionerID", rci.ProvisionerID),
errs.WithKeyVal("tokenID", rci.TokenID),
)
} else if p, err = a.LoadProvisionerByCertificate(revokeOpts.Crt); err == nil {
// Load the Certificate provisioner if one exists.
rci.ProvisionerID = p.GetID()
opts = append(opts, errs.WithKeyVal("provisionerID", rci.ProvisionerID))
}
if provisioner.MethodFromContext(ctx) == provisioner.SSHRevokeMethod {
err = a.revokeSSH(nil, rci)
} else {
// Revoke an X.509 certificate using CAS. If the certificate is not
// provided we will try to read it from the db. If the read fails we
// won't throw an error as it will be responsibility of the CAS
// implementation to require a certificate.
var revokedCert *x509.Certificate
if revokeOpts.Crt != nil {
revokedCert = revokeOpts.Crt
} else if rci.Serial != "" {
revokedCert, _ = a.db.GetCertificate(rci.Serial)
}
// 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,
SerialNumber: rci.Serial,
Reason: rci.Reason,
ReasonCode: rci.ReasonCode,
PassiveOnly: revokeOpts.PassiveOnly,
})
if err != nil {
return errs.Wrap(http.StatusInternalServerError, err, "authority.Revoke", opts...)
}
// Save as revoked in the Db.
err = a.revoke(revokedCert, rci)
}
switch err {
case nil:
return nil
case db.ErrNotImplemented:
return errs.NotImplemented("authority.Revoke; no persistence layer configured", opts...)
case db.ErrAlreadyExists:
return errs.ApplyOptions(
errs.BadRequest("certificate with serial number '%s' is already revoked", rci.Serial),
opts...,
)
default:
return errs.Wrap(http.StatusInternalServerError, err, "authority.Revoke", opts...)
}
}
func (a *Authority) revoke(crt *x509.Certificate, rci *db.RevokedCertificateInfo) error {
if lca, ok := a.adminDB.(interface {
Revoke(*x509.Certificate, *db.RevokedCertificateInfo) error
}); ok {
return lca.Revoke(crt, rci)
}
return a.db.Revoke(rci)
}
func (a *Authority) revokeSSH(crt *ssh.Certificate, rci *db.RevokedCertificateInfo) error {
if lca, ok := a.adminDB.(interface {
RevokeSSH(*ssh.Certificate, *db.RevokedCertificateInfo) error
}); ok {
return lca.RevokeSSH(crt, rci)
}
return a.db.Revoke(rci)
}
// GetTLSCertificate creates a new leaf certificate to be used by the CA HTTPS server.
func (a *Authority) GetTLSCertificate() (*tls.Certificate, error) {
fatal := func(err error) (*tls.Certificate, error) {
return nil, errs.Wrap(http.StatusInternalServerError, err, "authority.GetTLSCertificate")
}
// Generate default key.
priv, err := keyutil.GenerateDefaultKey()
if err != nil {
return fatal(err)
}
signer, ok := priv.(crypto.Signer)
if !ok {
return fatal(errors.New("private key is not a crypto.Signer"))
}
// prepare the sans: IPv6 DNS hostname representations are converted to their IP representation
sans := make([]string, len(a.config.DNSNames))
for i, san := range a.config.DNSNames {
if strings.HasPrefix(san, "[") && strings.HasSuffix(san, "]") {
if ip := net.ParseIP(san[1 : len(san)-1]); ip != nil {
san = ip.String()
}
}
sans[i] = san
}
// Create initial certificate request.
cr, err := x509util.CreateCertificateRequest(a.config.CommonName, sans, signer)
if err != nil {
return fatal(err)
}
// Generate certificate template directly from the certificate request.
template, err := x509util.NewCertificate(cr)
if err != nil {
return fatal(err)
}
// Get x509 certificate template, set validity and sign it.
now := time.Now()
certTpl := template.GetCertificate()
certTpl.NotBefore = now.Add(-1 * time.Minute)
certTpl.NotAfter = now.Add(24 * time.Hour)
resp, err := a.x509CAService.CreateCertificate(&casapi.CreateCertificateRequest{
Template: certTpl,
CSR: cr,
Lifetime: 24 * time.Hour,
Backdate: 1 * time.Minute,
})
if err != nil {
return fatal(err)
}
// Generate PEM blocks to create tls.Certificate
pemBlocks := pem.EncodeToMemory(&pem.Block{
Type: "CERTIFICATE",
Bytes: resp.Certificate.Raw,
})
for _, crt := range resp.CertificateChain {
pemBlocks = append(pemBlocks, pem.EncodeToMemory(&pem.Block{
Type: "CERTIFICATE",
Bytes: crt.Raw,
})...)
}
keyPEM, err := pemutil.Serialize(priv)
if err != nil {
return fatal(err)
}
tlsCrt, err := tls.X509KeyPair(pemBlocks, pem.EncodeToMemory(keyPEM))
if err != nil {
return fatal(err)
}
// Set leaf certificate
tlsCrt.Leaf = resp.Certificate
return &tlsCrt, nil
}
// templatingError tries to extract more information about the cause of
// an error related to (most probably) malformed template data and adds
// this to the error message.
func templatingError(err error) error {
cause := errors.Cause(err)
var (
syntaxError *json.SyntaxError
typeError *json.UnmarshalTypeError
)
if errors.As(err, &syntaxError) {
// offset is arguably not super clear to the user, but it's the best we can do here
cause = fmt.Errorf("%s at offset %d", cause.Error(), syntaxError.Offset)
} else if errors.As(err, &typeError) {
// slightly rewriting the default error message to include the offset
cause = fmt.Errorf("cannot unmarshal %s at offset %d into Go value of type %s", typeError.Value, typeError.Offset, typeError.Type)
}
return errors.Wrap(cause, "error applying certificate template")
}