Compare issuer certificates using cert, signature algo and signature fields (#15285)

* Move existing test helpers into a new test_helpers.go file within PKI

* Compare issuer certificates by cert, signature algo and signature

 - Instead of comparing the strings of a certificate, instead leverage
   the Go Raw attribute within a parsed certificate to compare. The Raw
   attribute is a byte array of an ASN.1 DER containing the cert,
   signature algo and signature.
 - Rework a bit of the importIssuers function as well to fail checks on the
   inbound issuer earlier as well as load keys/issuers just before we need
   them
This commit is contained in:
Steven Clark
2022-05-11 13:04:54 -04:00
committed by GitHub
parent 229681f767
commit 4ea9745eea
6 changed files with 298 additions and 248 deletions

View File

@@ -9,16 +9,12 @@ import (
"crypto/elliptic"
"crypto/rand"
"crypto/rsa"
"crypto/sha256"
"crypto/sha512"
"crypto/x509"
"crypto/x509/pkix"
"encoding/base64"
"encoding/json"
"encoding/pem"
"fmt"
"hash"
"io/ioutil"
"math"
"math/big"
mathrand "math/rand"
@@ -2780,23 +2776,6 @@ func TestBackend_SignSelfIssued_DifferentTypes(t *testing.T) {
}
}
func getSelfSigned(t *testing.T, subject, issuer *x509.Certificate, key *rsa.PrivateKey) (string, *x509.Certificate) {
t.Helper()
selfSigned, err := x509.CreateCertificate(rand.Reader, subject, issuer, key.Public(), key)
if err != nil {
t.Fatal(err)
}
cert, err := x509.ParseCertificate(selfSigned)
if err != nil {
t.Fatal(err)
}
pemSS := strings.TrimSpace(string(pem.EncodeToMemory(&pem.Block{
Type: "CERTIFICATE",
Bytes: selfSigned,
})))
return pemSS, cert
}
// This is a really tricky test because the Go stdlib asn1 package is incapable
// of doing the right thing with custom OID SANs (see comments in the package,
// it's readily admitted that it's too magic) but that means that any
@@ -4028,70 +4007,6 @@ func TestBackend_RevokePlusTidy_Intermediate(t *testing.T) {
}
}
func getParsedCrl(t *testing.T, client *api.Client, mountPoint string) *pkix.CertificateList {
path := fmt.Sprintf("/v1/%s/crl", mountPoint)
return getParsedCrlAtPath(t, client, path)
}
func getParsedCrlForIssuer(t *testing.T, client *api.Client, mountPoint string, issuer string) *pkix.CertificateList {
path := fmt.Sprintf("/v1/%v/issuer/%v/crl/der", mountPoint, issuer)
crl := getParsedCrlAtPath(t, client, path)
// Now fetch the issuer as well and verify the certificate
path = fmt.Sprintf("/v1/%v/issuer/%v/der", mountPoint, issuer)
req := client.NewRequest("GET", path)
resp, err := client.RawRequest(req)
if err != nil {
t.Fatal(err)
}
defer resp.Body.Close()
certBytes, err := ioutil.ReadAll(resp.Body)
if err != nil {
t.Fatalf("err: %s", err)
}
if len(certBytes) == 0 {
t.Fatalf("expected certificate in response body")
}
cert, err := x509.ParseCertificate(certBytes)
if err != nil {
t.Fatal(err)
}
if cert == nil {
t.Fatalf("expected parsed certificate")
}
if err := cert.CheckCRLSignature(crl); err != nil {
t.Fatalf("expected valid signature on CRL for issuer %v: %v", issuer, crl)
}
return crl
}
func getParsedCrlAtPath(t *testing.T, client *api.Client, path string) *pkix.CertificateList {
req := client.NewRequest("GET", path)
resp, err := client.RawRequest(req)
if err != nil {
t.Fatal(err)
}
defer resp.Body.Close()
crlBytes, err := ioutil.ReadAll(resp.Body)
if err != nil {
t.Fatalf("err: %s", err)
}
if len(crlBytes) == 0 {
t.Fatalf("expected CRL in response body")
}
crl, err := x509.ParseDERCRL(crlBytes)
if err != nil {
t.Fatal(err)
}
return crl
}
func TestBackend_Root_FullCAChain(t *testing.T) {
testCases := []struct {
testName string
@@ -5074,90 +4989,3 @@ var (
edCAKey string
edCACert string
)
func mountPKIEndpoint(t *testing.T, client *api.Client, path string) {
var err error
err = client.Sys().Mount(path, &api.MountInput{
Type: "pki",
Config: api.MountConfigInput{
DefaultLeaseTTL: "16h",
MaxLeaseTTL: "32h",
},
})
require.NoError(t, err, "failed mounting pki endpoint")
}
func requireSignedBy(t *testing.T, cert *x509.Certificate, key crypto.PublicKey) {
switch key.(type) {
case *rsa.PublicKey:
requireRSASignedBy(t, cert, key.(*rsa.PublicKey))
case *ecdsa.PublicKey:
requireECDSASignedBy(t, cert, key.(*ecdsa.PublicKey))
case ed25519.PublicKey:
requireED25519SignedBy(t, cert, key.(ed25519.PublicKey))
default:
require.Fail(t, "unknown public key type %#v", key)
}
}
func requireRSASignedBy(t *testing.T, cert *x509.Certificate, key *rsa.PublicKey) {
require.Contains(t, []x509.SignatureAlgorithm{x509.SHA256WithRSA, x509.SHA512WithRSA},
cert.SignatureAlgorithm, "only sha256 signatures supported")
var hasher hash.Hash
var hashAlgo crypto.Hash
switch cert.SignatureAlgorithm {
case x509.SHA256WithRSA:
hasher = sha256.New()
hashAlgo = crypto.SHA256
case x509.SHA512WithRSA:
hasher = sha512.New()
hashAlgo = crypto.SHA512
}
hasher.Write(cert.RawTBSCertificate)
hashData := hasher.Sum(nil)
err := rsa.VerifyPKCS1v15(key, hashAlgo, hashData, cert.Signature)
require.NoError(t, err, "the certificate was not signed by the expected public rsa key.")
}
func requireECDSASignedBy(t *testing.T, cert *x509.Certificate, key *ecdsa.PublicKey) {
require.Contains(t, []x509.SignatureAlgorithm{x509.ECDSAWithSHA256, x509.ECDSAWithSHA512},
cert.SignatureAlgorithm, "only ecdsa signatures supported")
var hasher hash.Hash
switch cert.SignatureAlgorithm {
case x509.ECDSAWithSHA256:
hasher = sha256.New()
case x509.ECDSAWithSHA512:
hasher = sha512.New()
}
hasher.Write(cert.RawTBSCertificate)
hashData := hasher.Sum(nil)
verify := ecdsa.VerifyASN1(key, hashData, cert.Signature)
require.True(t, verify, "the certificate was not signed by the expected public ecdsa key.")
}
func requireED25519SignedBy(t *testing.T, cert *x509.Certificate, key ed25519.PublicKey) {
require.Equal(t, x509.PureEd25519, cert.SignatureAlgorithm)
ed25519.Verify(key, cert.RawTBSCertificate, cert.Signature)
}
func parseCert(t *testing.T, pemCert string) *x509.Certificate {
block, _ := pem.Decode([]byte(pemCert))
require.NotNil(t, block, "failed to decode PEM block")
cert, err := x509.ParseCertificate(block.Bytes)
require.NoError(t, err)
return cert
}
func requireMatchingPublicKeys(t *testing.T, cert *x509.Certificate, key crypto.PublicKey) {
certPubKey := cert.PublicKey
require.True(t, reflect.DeepEqual(certPubKey, key),
"public keys mismatched: got: %v, expected: %v", certPubKey, key)
}

View File

@@ -11,6 +11,7 @@ import (
"encoding/asn1"
"encoding/base64"
"encoding/pem"
"errors"
"fmt"
"io"
"net"
@@ -1550,3 +1551,15 @@ func stringToOid(in string) (asn1.ObjectIdentifier, error) {
}
return ret, nil
}
func parseCertificateFromBytes(certBytes []byte) (*x509.Certificate, error) {
block, extra := pem.Decode(certBytes)
if block == nil {
return nil, errors.New("unable to parse certificate: invalid PEM")
}
if len(strings.TrimSpace(string(extra))) > 0 {
return nil, errors.New("unable to parse certificate: trailing PEM data")
}
return x509.ParseCertificate(block.Bytes)
}

View File

@@ -2,8 +2,6 @@ package pki
import (
"context"
"crypto/x509"
"crypto/x509/pkix"
"testing"
"time"
@@ -66,17 +64,21 @@ func TestBackend_CRL_EnableDisable(t *testing.T) {
serials[i] = resp.Data["serial_number"].(string)
}
test := func(num int) {
certList := getCrlCertificateList(t, client)
test := func(numRevokedExpected int, expectedSerials ...string) {
certList := getCrlCertificateList(t, client, "pki")
lenList := len(certList.RevokedCertificates)
if lenList != num {
t.Fatalf("expected %d revoked certificates, found %d", num, lenList)
if lenList != numRevokedExpected {
t.Fatalf("expected %d revoked certificates, found %d", numRevokedExpected, lenList)
}
for _, serialNum := range expectedSerials {
requireSerialNumberInCRL(t, certList, serialNum)
}
}
revoke := func(num int) {
revoke := func(serialIndex int) {
resp, err = client.Logical().Write("pki/revoke", map[string]interface{}{
"serial_number": serials[num],
"serial_number": serials[serialIndex],
})
if err != nil {
t.Fatal(err)
@@ -102,14 +104,14 @@ func TestBackend_CRL_EnableDisable(t *testing.T) {
test(0)
revoke(0)
revoke(1)
test(2)
test(2, serials[0], serials[1])
toggle(true)
test(0)
revoke(2)
revoke(3)
test(0)
toggle(false)
test(4)
test(4, serials[0], serials[1], serials[2], serials[3])
revoke(4)
revoke(5)
test(6)
@@ -119,12 +121,12 @@ func TestBackend_CRL_EnableDisable(t *testing.T) {
test(6)
// The rotate command should reset the update time of the CRL.
crlCreationTime1 := getCrlCertificateList(t, client).ThisUpdate
crlCreationTime1 := getCrlCertificateList(t, client, "pki").ThisUpdate
time.Sleep(1 * time.Second)
_, err = client.Logical().Read("pki/crl/rotate")
require.NoError(t, err)
crlCreationTime2 := getCrlCertificateList(t, client).ThisUpdate
crlCreationTime2 := getCrlCertificateList(t, client, "pki").ThisUpdate
require.NotEqual(t, crlCreationTime1, crlCreationTime2)
}
@@ -164,22 +166,3 @@ func requestCrlFromBackend(t *testing.T, s logical.Storage, b *backend) *logical
require.False(t, resp.IsError(), "crl error response: %v", resp)
return resp
}
func getCrlCertificateList(t *testing.T, client *api.Client) pkix.TBSCertificateList {
resp, err := client.Logical().ReadWithContext(context.Background(), "pki/cert/crl")
require.NoError(t, err, "crl req failed with an error")
require.NotNil(t, resp, "crl response was nil with no error")
crlPem := resp.Data["certificate"].(string)
return parseCrlPemString(t, crlPem)
}
func parseCrlPemString(t *testing.T, crlPem string) pkix.TBSCertificateList {
return parseCrlPemBytes(t, []byte(crlPem))
}
func parseCrlPemBytes(t *testing.T, crlPem []byte) pkix.TBSCertificateList {
certList, err := x509.ParseCRL(crlPem)
require.NoError(t, err)
return certList.TBSCertList
}

View File

@@ -10,21 +10,6 @@ import (
"github.com/mitchellh/mapstructure"
)
func createBackendWithStorage(t *testing.T) (*backend, logical.Storage) {
config := logical.TestBackendConfig()
config.StorageView = &logical.InmemStorage{}
var err error
b := Backend(config)
err = b.Setup(context.Background(), config)
if err != nil {
t.Fatal(err)
}
// Assume for our tests we have performed the migration already.
b.pkiStorageVersion.Store(1)
return b, config.StorageView
}
func TestPki_RoleGenerateLease(t *testing.T) {
var resp *logical.Response
var err error

View File

@@ -1,10 +1,10 @@
package pki
import (
"bytes"
"context"
"crypto"
"crypto/x509"
"encoding/pem"
"fmt"
"strings"
@@ -349,15 +349,12 @@ func importKey(mkc managedKeyContext, s logical.Storage, keyValue string, keyNam
}
func (i issuerEntry) GetCertificate() (*x509.Certificate, error) {
block, extra := pem.Decode([]byte(i.Certificate))
if block == nil {
return nil, errutil.InternalError{Err: fmt.Sprintf("unable to parse certificate from issuer: invalid PEM: %v", i.ID)}
}
if len(strings.TrimSpace(string(extra))) > 0 {
return nil, errutil.InternalError{Err: fmt.Sprintf("unable to parse certificate for issuer (%v): trailing PEM data: %v", i.ID, string(extra))}
cert, err := parseCertificateFromBytes([]byte(i.Certificate))
if err != nil {
return nil, errutil.InternalError{Err: fmt.Sprintf("unable to parse certificate from issuer: %s: %v", err.Error(), i.ID)}
}
return x509.ParseCertificate(block.Bytes)
return cert, nil
}
func (i issuerEntry) EnsureUsage(usage issuerUsage) error {
@@ -513,19 +510,23 @@ func importIssuer(ctx managedKeyContext, s logical.Storage, certValue string, is
// Discussed further in #11960 and RFC 7468.
certValue = strings.TrimSpace(certValue) + "\n"
// Before we can import a known issuer, we first need to know if the issuer
// exists in storage already. This means iterating through all known
// issuers and comparing their private value against this value.
knownIssuers, err := listIssuers(ctx.ctx, s)
// Extracting the certificate is necessary for two reasons: first, it lets
// us fetch the serial number; second, for the public key comparison with
// known keys.
issuerCert, err := parseCertificateFromBytes([]byte(certValue))
if err != nil {
return nil, false, err
}
// Before we return below, we need to iterate over _all_ keys and see if
// one of them a public key matching this certificate, and if so, update our
// link accordingly. We fetch the list of keys up front, even may not need
// it, to give ourselves a better chance of succeeding below.
knownKeys, err := listKeys(ctx.ctx, s)
// Ensure this certificate is a usable as a CA certificate.
if !issuerCert.BasicConstraintsValid || !issuerCert.IsCA {
return nil, false, errutil.UserError{Err: "Refusing to import non-CA certificate"}
}
// Before we can import a known issuer, we first need to know if the issuer
// exists in storage already. This means iterating through all known
// issuers and comparing their private value against this value.
knownIssuers, err := listIssuers(ctx.ctx, s)
if err != nil {
return nil, false, err
}
@@ -535,8 +536,11 @@ func importIssuer(ctx managedKeyContext, s logical.Storage, certValue string, is
if err != nil {
return nil, false, err
}
if existingIssuer.Certificate == certValue {
existingIssuerCert, err := existingIssuer.GetCertificate()
if err != nil {
return nil, false, err
}
if areCertificatesEqual(existingIssuerCert, issuerCert) {
// Here, we don't need to stitch together the key entries,
// because the last run should've done that for us (or, when
// importing a key).
@@ -559,21 +563,17 @@ func importIssuer(ctx managedKeyContext, s logical.Storage, certValue string, is
return nil, false, fmt.Errorf("bad issuer: potentially multiple PEM blobs in one certificate storage entry:\n%v", result.Certificate)
}
// Extracting the certificate is necessary for two reasons: first, it lets
// us fetch the serial number; second, for the public key comparison with
// known keys.
issuerCert, err := result.GetCertificate()
result.SerialNumber = strings.TrimSpace(certutil.GetHexFormatted(issuerCert.SerialNumber.Bytes(), ":"))
// Before we return below, we need to iterate over _all_ keys and see if
// one of them a public key matching this certificate, and if so, update our
// link accordingly. We fetch the list of keys up front, even may not need
// it, to give ourselves a better chance of succeeding below.
knownKeys, err := listKeys(ctx.ctx, s)
if err != nil {
return nil, false, err
}
// Ensure this certificate is a usable as a CA certificate.
if !issuerCert.BasicConstraintsValid || !issuerCert.IsCA {
return nil, false, errutil.UserError{Err: "Refusing to import non-CA certificate"}
}
result.SerialNumber = strings.TrimSpace(certutil.GetHexFormatted(issuerCert.SerialNumber.Bytes(), ":"))
// Now, for each key, try and compute the issuer<->key link. We delay
// writing issuer to storage as we won't need to update the key, only
// the issuer.
@@ -620,6 +620,10 @@ func importIssuer(ctx managedKeyContext, s logical.Storage, certValue string, is
return &result, false, nil
}
func areCertificatesEqual(cert1 *x509.Certificate, cert2 *x509.Certificate) bool {
return bytes.Compare(cert1.Raw, cert2.Raw) == 0
}
func setLocalCRLConfig(ctx context.Context, s logical.Storage, mapping *localCRLConfigEntry) error {
json, err := logical.StorageEntryJSON(storageLocalCRLConfig, mapping)
if err != nil {

View File

@@ -0,0 +1,237 @@
package pki
import (
"context"
"crypto"
"crypto/ecdsa"
"crypto/ed25519"
"crypto/rand"
"crypto/rsa"
"crypto/sha256"
"crypto/sha512"
"crypto/x509"
"crypto/x509/pkix"
"encoding/pem"
"fmt"
"hash"
"io/ioutil"
"strings"
"testing"
"github.com/hashicorp/vault/api"
"github.com/hashicorp/vault/sdk/helper/certutil"
"github.com/hashicorp/vault/sdk/logical"
"github.com/stretchr/testify/require"
)
// Setup helpers
func createBackendWithStorage(t *testing.T) (*backend, logical.Storage) {
config := logical.TestBackendConfig()
config.StorageView = &logical.InmemStorage{}
var err error
b := Backend(config)
err = b.Setup(context.Background(), config)
if err != nil {
t.Fatal(err)
}
// Assume for our tests we have performed the migration already.
b.pkiStorageVersion.Store(1)
return b, config.StorageView
}
func mountPKIEndpoint(t *testing.T, client *api.Client, path string) {
var err error
err = client.Sys().Mount(path, &api.MountInput{
Type: "pki",
Config: api.MountConfigInput{
DefaultLeaseTTL: "16h",
MaxLeaseTTL: "32h",
},
})
require.NoError(t, err, "failed mounting pki endpoint")
}
// Signing helpers
func requireSignedBy(t *testing.T, cert *x509.Certificate, key crypto.PublicKey) {
switch key.(type) {
case *rsa.PublicKey:
requireRSASignedBy(t, cert, key.(*rsa.PublicKey))
case *ecdsa.PublicKey:
requireECDSASignedBy(t, cert, key.(*ecdsa.PublicKey))
case ed25519.PublicKey:
requireED25519SignedBy(t, cert, key.(ed25519.PublicKey))
default:
require.Fail(t, "unknown public key type %#v", key)
}
}
func requireRSASignedBy(t *testing.T, cert *x509.Certificate, key *rsa.PublicKey) {
require.Contains(t, []x509.SignatureAlgorithm{x509.SHA256WithRSA, x509.SHA512WithRSA},
cert.SignatureAlgorithm, "only sha256 signatures supported")
var hasher hash.Hash
var hashAlgo crypto.Hash
switch cert.SignatureAlgorithm {
case x509.SHA256WithRSA:
hasher = sha256.New()
hashAlgo = crypto.SHA256
case x509.SHA512WithRSA:
hasher = sha512.New()
hashAlgo = crypto.SHA512
}
hasher.Write(cert.RawTBSCertificate)
hashData := hasher.Sum(nil)
err := rsa.VerifyPKCS1v15(key, hashAlgo, hashData, cert.Signature)
require.NoError(t, err, "the certificate was not signed by the expected public rsa key.")
}
func requireECDSASignedBy(t *testing.T, cert *x509.Certificate, key *ecdsa.PublicKey) {
require.Contains(t, []x509.SignatureAlgorithm{x509.ECDSAWithSHA256, x509.ECDSAWithSHA512},
cert.SignatureAlgorithm, "only ecdsa signatures supported")
var hasher hash.Hash
switch cert.SignatureAlgorithm {
case x509.ECDSAWithSHA256:
hasher = sha256.New()
case x509.ECDSAWithSHA512:
hasher = sha512.New()
}
hasher.Write(cert.RawTBSCertificate)
hashData := hasher.Sum(nil)
verify := ecdsa.VerifyASN1(key, hashData, cert.Signature)
require.True(t, verify, "the certificate was not signed by the expected public ecdsa key.")
}
func requireED25519SignedBy(t *testing.T, cert *x509.Certificate, key ed25519.PublicKey) {
require.Equal(t, x509.PureEd25519, cert.SignatureAlgorithm)
ed25519.Verify(key, cert.RawTBSCertificate, cert.Signature)
}
// Certificate helper
func parseCert(t *testing.T, pemCert string) *x509.Certificate {
block, _ := pem.Decode([]byte(pemCert))
require.NotNil(t, block, "failed to decode PEM block")
cert, err := x509.ParseCertificate(block.Bytes)
require.NoError(t, err)
return cert
}
func requireMatchingPublicKeys(t *testing.T, cert *x509.Certificate, key crypto.PublicKey) {
certPubKey := cert.PublicKey
areEqual, err := certutil.ComparePublicKeysAndType(certPubKey, key)
require.NoError(t, err, "failed comparing public keys: %#v", err)
require.True(t, areEqual, "public keys mismatched: got: %v, expected: %v", certPubKey, key)
}
func getSelfSigned(t *testing.T, subject, issuer *x509.Certificate, key *rsa.PrivateKey) (string, *x509.Certificate) {
t.Helper()
selfSigned, err := x509.CreateCertificate(rand.Reader, subject, issuer, key.Public(), key)
if err != nil {
t.Fatal(err)
}
cert, err := x509.ParseCertificate(selfSigned)
if err != nil {
t.Fatal(err)
}
pemSS := strings.TrimSpace(string(pem.EncodeToMemory(&pem.Block{
Type: "CERTIFICATE",
Bytes: selfSigned,
})))
return pemSS, cert
}
// CRL related helpers
func getCrlCertificateList(t *testing.T, client *api.Client, mountPoint string) pkix.TBSCertificateList {
path := fmt.Sprintf("/v1/%s/crl", mountPoint)
return getParsedCrlAtPath(t, client, path).TBSCertList
}
func parseCrlPemBytes(t *testing.T, crlPem []byte) pkix.TBSCertificateList {
certList, err := x509.ParseCRL(crlPem)
require.NoError(t, err)
return certList.TBSCertList
}
func requireSerialNumberInCRL(t *testing.T, revokeList pkix.TBSCertificateList, serialNum string) {
serialsInList := make([]string, 0, len(revokeList.RevokedCertificates))
for _, revokeEntry := range revokeList.RevokedCertificates {
formattedSerial := certutil.GetHexFormatted(revokeEntry.SerialNumber.Bytes(), ":")
serialsInList = append(serialsInList, formattedSerial)
if formattedSerial == serialNum {
return
}
}
t.Fatalf("the serial number %s, was not found in the CRL list containing: %v", serialNum, serialsInList)
}
func getParsedCrl(t *testing.T, client *api.Client, mountPoint string) *pkix.CertificateList {
path := fmt.Sprintf("/v1/%s/crl", mountPoint)
return getParsedCrlAtPath(t, client, path)
}
func getParsedCrlForIssuer(t *testing.T, client *api.Client, mountPoint string, issuer string) *pkix.CertificateList {
path := fmt.Sprintf("/v1/%v/issuer/%v/crl/der", mountPoint, issuer)
crl := getParsedCrlAtPath(t, client, path)
// Now fetch the issuer as well and verify the certificate
path = fmt.Sprintf("/v1/%v/issuer/%v/der", mountPoint, issuer)
req := client.NewRequest("GET", path)
resp, err := client.RawRequest(req)
if err != nil {
t.Fatal(err)
}
defer resp.Body.Close()
certBytes, err := ioutil.ReadAll(resp.Body)
if err != nil {
t.Fatalf("err: %s", err)
}
if len(certBytes) == 0 {
t.Fatalf("expected certificate in response body")
}
cert, err := x509.ParseCertificate(certBytes)
if err != nil {
t.Fatal(err)
}
if cert == nil {
t.Fatalf("expected parsed certificate")
}
if err := cert.CheckCRLSignature(crl); err != nil {
t.Fatalf("expected valid signature on CRL for issuer %v: %v", issuer, crl)
}
return crl
}
func getParsedCrlAtPath(t *testing.T, client *api.Client, path string) *pkix.CertificateList {
req := client.NewRequest("GET", path)
resp, err := client.RawRequest(req)
if err != nil {
t.Fatal(err)
}
defer resp.Body.Close()
crlBytes, err := ioutil.ReadAll(resp.Body)
if err != nil {
t.Fatalf("err: %s", err)
}
if len(crlBytes) == 0 {
t.Fatalf("expected CRL in response body")
}
crl, err := x509.ParseDERCRL(crlBytes)
if err != nil {
t.Fatal(err)
}
return crl
}