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Increase test coverage for AK certificate properties

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This commit is contained in:
Herman Slatman 2023-04-06 14:35:48 +02:00
parent ed1a62206e
commit d9aa2c110f
No known key found for this signature in database
GPG key ID: F4D8A44EA0A75A4F
3 changed files with 353 additions and 123 deletions
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15
acme/challenge.go
View file

@ -729,30 +729,29 @@ var (
// and a CRL Distribution Point extension [RFC5280] are both OPTIONAL as
// the status of many attestation certificates is available through metadata
// services. See, for example, the FIDO Metadata Service.
func validateAKCertificate(c *x509.Certificate) error {
if c.Version != 3 {
return fmt.Errorf("AK certificate has invalid version %d; only version 3 is allowed", c.Version)
}
if c.Subject.String() != "" {
return fmt.Errorf("AK certificate subject must be empty; got %s", c.Subject)
return fmt.Errorf("AK certificate subject must be empty; got %q", c.Subject)
}
if err := validateAKCertificateSubjectAlternativeNames(c); err != nil {
return err
if c.IsCA {
return errors.New("AK certificate must not be a CA")
}
if err := validateAKCertificateExtendedKeyUsage(c); err != nil {
return err
}
if c.IsCA {
return errors.New("AK certificate must not be a CA")
if err := validateAKCertificateSubjectAlternativeNames(c); err != nil {
return err
}
return nil
}
// validateAKCertificateSubjectAlternativeNames checks if the AK certificate
// has TPM hardware details set.
func validateAKCertificateSubjectAlternativeNames(c *x509.Certificate) error {
return nil // TODO(hs): remove this early return when we require AK certificates to set these
sans, err := x509util.ParseSubjectAlternativeNames(c)
if err != nil {
return fmt.Errorf("failed parsing AK certificate Subject Alternative Names: %w", err)

295
acme/challenge_test.go
View file

@ -31,15 +31,14 @@ import (
"time"
"github.com/fxamacker/cbor/v2"
"github.com/smallstep/certificates/authority/config"
"github.com/smallstep/certificates/authority/provisioner"
"github.com/stretchr/testify/assert"
"github.com/stretchr/testify/require"
"go.step.sm/crypto/jose"
"go.step.sm/crypto/keyutil"
"go.step.sm/crypto/minica"
"github.com/smallstep/certificates/authority/config"
"github.com/smallstep/certificates/authority/provisioner"
"go.step.sm/crypto/x509util"
)
type mockClient struct {
@ -4008,3 +4007,291 @@ func Test_deviceAttest01Validate(t *testing.T) {
})
}
}
var (
oidTPMManufacturer = asn1.ObjectIdentifier{2, 23, 133, 2, 1}
oidTPMModel = asn1.ObjectIdentifier{2, 23, 133, 2, 2}
oidTPMVersion = asn1.ObjectIdentifier{2, 23, 133, 2, 3}
)
func generateValidAKCertificate(t *testing.T) *x509.Certificate {
t.Helper()
signer, err := ecdsa.GenerateKey(elliptic.P256(), rand.Reader)
require.NoError(t, err)
template := &x509.Certificate{
PublicKey: signer.Public(),
Version: 3,
IsCA: false,
UnknownExtKeyUsage: []asn1.ObjectIdentifier{oidTCGKpAIKCertificate},
}
asn1Value := []byte(fmt.Sprintf(`{"extraNames":[{"type": %q, "value": %q},{"type": %q, "value": %q},{"type": %q, "value": %q}]}`, oidTPMManufacturer, "1414747215", oidTPMModel, "SLB 9670 TPM2.0", oidTPMVersion, "7.55"))
sans := []x509util.SubjectAlternativeName{
{Type: x509util.DirectoryNameType,
ASN1Value: asn1Value},
}
ext, err := createSubjectAltNameExtension(nil, nil, nil, nil, sans, true)
require.NoError(t, err)
ext.Set(template)
ca, err := minica.New()
require.NoError(t, err)
cert, err := ca.Sign(template)
require.NoError(t, err)
return cert
}
func Test_validateAKCertificate(t *testing.T) {
cert := generateValidAKCertificate(t)
tests := []struct {
name string
c *x509.Certificate
expErr error
}{
{
name: "ok",
c: cert,
expErr: nil,
},
{
name: "fail/version",
c: &x509.Certificate{
Version: 1,
},
expErr: errors.New("AK certificate has invalid version 1; only version 3 is allowed"),
},
{
name: "fail/subject",
c: &x509.Certificate{
Version: 3,
Subject: pkix.Name{CommonName: "fail!"},
},
expErr: errors.New(`AK certificate subject must be empty; got "CN=fail!"`),
},
{
name: "fail/isCA",
c: &x509.Certificate{
Version: 3,
IsCA: true,
},
expErr: errors.New("AK certificate must not be a CA"),
},
{
name: "fail/extendedKeyUsage",
c: &x509.Certificate{
Version: 3,
},
expErr: errors.New("AK certificate is missing Extended Key Usage extension"),
},
}
for _, tt := range tests {
t.Run(tt.name, func(t *testing.T) {
err := validateAKCertificate(tt.c)
if tt.expErr != nil {
if assert.Error(t, err) {
assert.EqualError(t, err, tt.expErr.Error())
}
return
}
assert.NoError(t, err)
})
}
}
func Test_validateAKCertificateSubjectAlternativeNames(t *testing.T) {
ok := generateValidAKCertificate(t)
t.Helper()
signer, err := ecdsa.GenerateKey(elliptic.P256(), rand.Reader)
require.NoError(t, err)
getBase := func() *x509.Certificate {
return &x509.Certificate{
PublicKey: signer.Public(),
Version: 3,
IsCA: false,
UnknownExtKeyUsage: []asn1.ObjectIdentifier{oidTCGKpAIKCertificate},
}
}
ca, err := minica.New()
require.NoError(t, err)
missingManufacturerASN1 := []byte(fmt.Sprintf(`{"extraNames":[{"type": %q, "value": %q},{"type": %q, "value": %q}]}`, oidTPMModel, "SLB 9670 TPM2.0", oidTPMVersion, "7.55"))
sans := []x509util.SubjectAlternativeName{
{Type: x509util.DirectoryNameType,
ASN1Value: missingManufacturerASN1},
}
ext, err := createSubjectAltNameExtension(nil, nil, nil, nil, sans, true)
require.NoError(t, err)
missingManufacturer := getBase()
ext.Set(missingManufacturer)
missingManufacturer, err = ca.Sign(missingManufacturer)
require.NoError(t, err)
missingModelASN1 := []byte(fmt.Sprintf(`{"extraNames":[{"type": %q, "value": %q},{"type": %q, "value": %q}]}`, oidTPMManufacturer, "1414747215", oidTPMVersion, "7.55"))
sans = []x509util.SubjectAlternativeName{
{Type: x509util.DirectoryNameType,
ASN1Value: missingModelASN1},
}
ext, err = createSubjectAltNameExtension(nil, nil, nil, nil, sans, true)
require.NoError(t, err)
missingModel := getBase()
ext.Set(missingModel)
missingModel, err = ca.Sign(missingModel)
require.NoError(t, err)
missingFirmwareVersionASN1 := []byte(fmt.Sprintf(`{"extraNames":[{"type": %q, "value": %q},{"type": %q, "value": %q}]}`, oidTPMManufacturer, "1414747215", oidTPMModel, "SLB 9670 TPM2.0"))
sans = []x509util.SubjectAlternativeName{
{Type: x509util.DirectoryNameType,
ASN1Value: missingFirmwareVersionASN1},
}
ext, err = createSubjectAltNameExtension(nil, nil, nil, nil, sans, true)
require.NoError(t, err)
missingFirmwareVersion := getBase()
ext.Set(missingFirmwareVersion)
missingFirmwareVersion, err = ca.Sign(missingFirmwareVersion)
require.NoError(t, err)
tests := []struct {
name string
c *x509.Certificate
expErr error
}{
{"ok", ok, nil},
{"fail/missing-manufacturer", missingManufacturer, errors.New("missing TPM manufacturer")},
{"fail/missing-model", missingModel, errors.New("missing TPM model")},
{"fail/missing-firmware-version", missingFirmwareVersion, errors.New("missing TPM version")},
}
for _, tt := range tests {
t.Run(tt.name, func(t *testing.T) {
err := validateAKCertificateSubjectAlternativeNames(tt.c)
if tt.expErr != nil {
if assert.Error(t, err) {
assert.EqualError(t, err, tt.expErr.Error())
}
return
}
assert.NoError(t, err)
})
}
}
func Test_validateAKCertificateExtendedKeyUsage(t *testing.T) {
ok := generateValidAKCertificate(t)
missingEKU := &x509.Certificate{}
t.Helper()
signer, err := ecdsa.GenerateKey(elliptic.P256(), rand.Reader)
require.NoError(t, err)
template := &x509.Certificate{
PublicKey: signer.Public(),
ExtKeyUsage: []x509.ExtKeyUsage{x509.ExtKeyUsageServerAuth},
}
ca, err := minica.New()
require.NoError(t, err)
wrongEKU, err := ca.Sign(template)
require.NoError(t, err)
tests := []struct {
name string
c *x509.Certificate
expErr error
}{
{"ok", ok, nil},
{"fail/wrong-eku", wrongEKU, errors.New("AK certificate is missing Extended Key Usage value tcg-kp-AIKCertificate (2.23.133.8.3)")},
{"fail/missing-eku", missingEKU, errors.New("AK certificate is missing Extended Key Usage extension")},
}
for _, tt := range tests {
t.Run(tt.name, func(t *testing.T) {
err := validateAKCertificateExtendedKeyUsage(tt.c)
if tt.expErr != nil {
if assert.Error(t, err) {
assert.EqualError(t, err, tt.expErr.Error())
}
return
}
assert.NoError(t, err)
})
}
}
// createSubjectAltNameExtension will construct an Extension containing all
// SubjectAlternativeNames held in a Certificate. It implements more types than
// the golang x509 library, so it is used whenever OtherName or RegisteredID
// type SANs are present in the certificate.
//
// See also https://datatracker.ietf.org/doc/html/rfc5280.html#section-4.2.1.6
//
// TODO(hs): this was copied from go.step.sm/crypto/x509util to make it easier
// to create the SAN extension for testing purposes. Should it be exposed instead?
func createSubjectAltNameExtension(dnsNames, emailAddresses x509util.MultiString, ipAddresses x509util.MultiIP, uris x509util.MultiURL, sans []x509util.SubjectAlternativeName, subjectIsEmpty bool) (x509util.Extension, error) {
var zero x509util.Extension
var rawValues []asn1.RawValue
for _, dnsName := range dnsNames {
rawValue, err := x509util.SubjectAlternativeName{
Type: x509util.DNSType, Value: dnsName,
}.RawValue()
if err != nil {
return zero, err
}
rawValues = append(rawValues, rawValue)
}
for _, emailAddress := range emailAddresses {
rawValue, err := x509util.SubjectAlternativeName{
Type: x509util.EmailType, Value: emailAddress,
}.RawValue()
if err != nil {
return zero, err
}
rawValues = append(rawValues, rawValue)
}
for _, ip := range ipAddresses {
rawValue, err := x509util.SubjectAlternativeName{
Type: x509util.IPType, Value: ip.String(),
}.RawValue()
if err != nil {
return zero, err
}
rawValues = append(rawValues, rawValue)
}
for _, uri := range uris {
rawValue, err := x509util.SubjectAlternativeName{
Type: x509util.URIType, Value: uri.String(),
}.RawValue()
if err != nil {
return zero, err
}
rawValues = append(rawValues, rawValue)
}
for _, san := range sans {
rawValue, err := san.RawValue()
if err != nil {
return zero, err
}
rawValues = append(rawValues, rawValue)
}
// Now marshal the rawValues into the ASN1 sequence, and create an Extension object to hold the extension
rawBytes, err := asn1.Marshal(rawValues)
if err != nil {
return zero, fmt.Errorf("error marshaling SubjectAlternativeName extension to ASN1: %w", err)
}
return x509util.Extension{
ID: x509util.ObjectIdentifier(oidSubjectAlternativeName),
Critical: subjectIsEmpty,
Value: rawBytes,
}, nil
}

142
acme/challenge_tpmsimulator_test.go
View file

@ -8,7 +8,6 @@ import (
"crypto"
"crypto/sha256"
"crypto/x509"
"crypto/x509/pkix"
"encoding/asn1"
"encoding/base64"
"encoding/json"
@ -97,25 +96,22 @@ func mustAttestTPM(t *testing.T, keyAuthorization string, permanentIdentifiers [
IsCA: false,
UnknownExtKeyUsage: []asn1.ObjectIdentifier{oidTCGKpAIKCertificate},
}
if len(permanentIdentifiers) == 0 {
template.URIs = []*url.URL{
{Scheme: "urn", Opaque: "ek:sha256:" + base64.StdEncoding.EncodeToString(keyID)},
}
} else {
san := x509util.SubjectAlternativeName{
sans := []x509util.SubjectAlternativeName{}
uris := []*url.URL{{Scheme: "urn", Opaque: "ek:sha256:" + base64.StdEncoding.EncodeToString(keyID)}}
for _, pi := range permanentIdentifiers {
sans = append(sans, x509util.SubjectAlternativeName{
Type: x509util.PermanentIdentifierType,
Value: permanentIdentifiers[0], // TODO(hs): multiple?
Value: pi,
})
}
ext, err := createSubjectAltNameExtension(nil, nil, nil, nil, []x509util.SubjectAlternativeName{san}, true)
asn1Value := []byte(fmt.Sprintf(`{"extraNames":[{"type": %q, "value": %q},{"type": %q, "value": %q},{"type": %q, "value": %q}]}`, oidTPMManufacturer, "1414747215", oidTPMModel, "SLB 9670 TPM2.0", oidTPMVersion, "7.55"))
sans = append(sans, x509util.SubjectAlternativeName{
Type: x509util.DirectoryNameType,
ASN1Value: asn1Value,
})
ext, err := createSubjectAltNameExtension(nil, nil, nil, uris, sans, true)
require.NoError(t, err)
template.ExtraExtensions = append(template.ExtraExtensions,
pkix.Extension{
Id: asn1.ObjectIdentifier(ext.ID),
Critical: ext.Critical,
Value: ext.Value,
},
)
}
ext.Set(template)
akCert, err := aca.Sign(template)
require.NoError(t, err)
require.NotNil(t, akCert)
@ -461,14 +457,30 @@ func Test_doTPMAttestationFormat(t *testing.T) {
PublicKey: akp.Public,
IsCA: false,
UnknownExtKeyUsage: []asn1.ObjectIdentifier{oidTCGKpAIKCertificate},
URIs: []*url.URL{
{Scheme: "urn", Opaque: "ek:sha256:" + base64.StdEncoding.EncodeToString(keyID)},
},
}
sans := []x509util.SubjectAlternativeName{}
uris := []*url.URL{{Scheme: "urn", Opaque: "ek:sha256:" + base64.StdEncoding.EncodeToString(keyID)}}
asn1Value := []byte(fmt.Sprintf(`{"extraNames":[{"type": %q, "value": %q},{"type": %q, "value": %q},{"type": %q, "value": %q}]}`, oidTPMManufacturer, "1414747215", oidTPMModel, "SLB 9670 TPM2.0", oidTPMVersion, "7.55"))
sans = append(sans, x509util.SubjectAlternativeName{
Type: x509util.DirectoryNameType,
ASN1Value: asn1Value,
})
ext, err := createSubjectAltNameExtension(nil, nil, nil, uris, sans, true)
require.NoError(t, err)
ext.Set(template)
akCert, err := aca.Sign(template)
require.NoError(t, err)
require.NotNil(t, akCert)
invalidTemplate := &x509.Certificate{
PublicKey: akp.Public,
IsCA: false,
UnknownExtKeyUsage: []asn1.ObjectIdentifier{oidTCGKpAIKCertificate},
}
invalidAKCert, err := aca.Sign(invalidTemplate)
require.NoError(t, err)
require.NotNil(t, invalidAKCert)
// generate a JWK and the key authorization value
jwk, err := jose.GenerateJWK("EC", "P-256", "ES256", "sig", "", 0)
require.NoError(t, err)
@ -655,6 +667,17 @@ func Test_doTPMAttestationFormat(t *testing.T) {
"pubArea": params.Public,
},
}}, nil, newBadAttestationStatementError("x5c is not valid: x509: certificate signed by unknown authority")},
{"fail validateAKCertificate", args{ctx, mustAttestationProvisioner(t, acaRoot), &Challenge{Token: "token"}, jwk, &attestationObject{
Format: "tpm",
AttStatement: map[string]interface{}{
"ver": "2.0",
"x5c": []interface{}{invalidAKCert.Raw, aca.Intermediate.Raw},
"alg": int64(-257), // RS256
"sig": params.CreateSignature,
"certInfo": params.CreateAttestation,
"pubArea": params.Public,
},
}}, nil, newBadAttestationStatementError("AK certificate is not valid: missing TPM manufacturer")},
{"fail pubArea not present", args{ctx, mustAttestationProvisioner(t, acaRoot), &Challenge{Token: "token"}, jwk, &attestationObject{
Format: "tpm",
AttStatement: map[string]interface{}{
@ -834,82 +857,3 @@ func Test_doTPMAttestationFormat(t *testing.T) {
})
}
}
// createSubjectAltNameExtension will construct an Extension containing all
// SubjectAlternativeNames held in a Certificate. It implements more types than
// the golang x509 library, so it is used whenever OtherName or RegisteredID
// type SANs are present in the certificate.
//
// See also https://datatracker.ietf.org/doc/html/rfc5280.html#section-4.2.1.6
//
// TODO(hs): this was copied from go.step.sm/crypto/x509util to make it easier
// to create the SAN extension for testing purposes. Should it be exposed instead?
func createSubjectAltNameExtension(dnsNames, emailAddresses x509util.MultiString, ipAddresses x509util.MultiIP, uris x509util.MultiURL, sans []x509util.SubjectAlternativeName, subjectIsEmpty bool) (x509util.Extension, error) {
var zero x509util.Extension
var rawValues []asn1.RawValue
for _, dnsName := range dnsNames {
rawValue, err := x509util.SubjectAlternativeName{
Type: x509util.DNSType, Value: dnsName,
}.RawValue()
if err != nil {
return zero, err
}
rawValues = append(rawValues, rawValue)
}
for _, emailAddress := range emailAddresses {
rawValue, err := x509util.SubjectAlternativeName{
Type: x509util.EmailType, Value: emailAddress,
}.RawValue()
if err != nil {
return zero, err
}
rawValues = append(rawValues, rawValue)
}
for _, ip := range ipAddresses {
rawValue, err := x509util.SubjectAlternativeName{
Type: x509util.IPType, Value: ip.String(),
}.RawValue()
if err != nil {
return zero, err
}
rawValues = append(rawValues, rawValue)
}
for _, uri := range uris {
rawValue, err := x509util.SubjectAlternativeName{
Type: x509util.URIType, Value: uri.String(),
}.RawValue()
if err != nil {
return zero, err
}
rawValues = append(rawValues, rawValue)
}
for _, san := range sans {
rawValue, err := san.RawValue()
if err != nil {
return zero, err
}
rawValues = append(rawValues, rawValue)
}
// Now marshal the rawValues into the ASN1 sequence, and create an Extension object to hold the extension
rawBytes, err := asn1.Marshal(rawValues)
if err != nil {
return zero, fmt.Errorf("error marshaling SubjectAlternativeName extension to ASN1: %w", err)
}
return x509util.Extension{
ID: x509util.ObjectIdentifier(oidSubjectAlternativeName),
Critical: subjectIsEmpty,
Value: rawBytes,
}, nil
}