Add `PermanentIdentifier` SAN parsing and tests

acme/challenge.go

@@ -34,6 +34,7 @@ import (
 	"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/provisioner"
 )
@@ -599,6 +600,18 @@ func doTPMAttestationFormat(ctx context.Context, prov Provisioner, ch *Challenge
 		return nil, NewError(ErrorBadAttestationStatementType, "AK certificate is missing Subject Alternative Name extension")
 	}
 
+	sans, err := parseSANs(sanExtension)
+	if err != nil {
+		return nil, WrapError(ErrorBadAttestationStatementType, err, "failed parsing AK certificate SAN extension")
+	}
+
+	var permanentIdentifiers []string
+	for _, san := range sans {
+		if san.Type == x509util.PermanentIdentifierType {
+			permanentIdentifiers = append(permanentIdentifiers, san.Value)
+		}
+	}
+
 	// extract and validate pubArea, sig, certInfo and alg properties from the request body
 	pubArea, ok := att.AttStatement["pubArea"].([]byte)
 	if !ok {
@@ -686,8 +699,9 @@ func doTPMAttestationFormat(ctx context.Context, prov Provisioner, ch *Challenge
 	}
 
 	data := &tpmAttestationData{
-		Certificate:    akCert,
-		VerifiedChains: verifiedChains,
+		Certificate:          akCert,
+		VerifiedChains:       verifiedChains,
+		PermanentIdentifiers: permanentIdentifiers,
 	}
 
 	if data.Fingerprint, err = keyutil.Fingerprint(publicKey); err != nil {
@@ -698,6 +712,123 @@ func doTPMAttestationFormat(ctx context.Context, prov Provisioner, ch *Challenge
 	return data, nil
 }
 
+// RFC 4043
+//
+// https://tools.ietf.org/html/rfc4043
+var (
+	oidPermanentIdentifier = []int{1, 3, 6, 1, 5, 5, 7, 8, 3}
+)
+
+// PermanentIdentifier represents an ASN.1 encoded "permanent identifier" as
+// defined by RFC4043.
+//
+//	PermanentIdentifier ::= SEQUENCE {
+//	    identifierValue    UTF8String OPTIONAL,
+//	    assigner           OBJECT IDENTIFIER OPTIONAL
+//	   }
+//
+// https://datatracker.ietf.org/doc/html/rfc4043
+type permanentIdentifier struct {
+	IdentifierValue string                `asn1:"utf8,optional"`
+	Assigner        asn1.ObjectIdentifier `asn1:"optional"`
+}
+
+func parsePermanentIdentifier(der []byte) (permanentIdentifier, error) {
+	var permID permanentIdentifier
+	if _, err := asn1.UnmarshalWithParams(der, &permID, "explicit,tag:0"); err != nil {
+		return permanentIdentifier{}, err
+	}
+	return permID, nil
+}
+
+func parseSANs(ext pkix.Extension) (sans []x509util.SubjectAlternativeName, err error) {
+
+	_, otherNames, err := parseSubjectAltName(ext)
+	if err != nil {
+		return nil, fmt.Errorf("parseSubjectAltName: %w", err)
+	}
+
+	for _, otherName := range otherNames {
+		if otherName.TypeID.Equal(oidPermanentIdentifier) {
+			permID, err := parsePermanentIdentifier(otherName.Value.FullBytes)
+			if err != nil {
+				return nil, fmt.Errorf("parsePermanentIdentifier: %w", err)
+			}
+			permanentIdentifier := x509util.SubjectAlternativeName{
+				Type:  x509util.PermanentIdentifierType,
+				Value: permID.IdentifierValue, // TODO(hs): change how these are returned
+			}
+			sans = append(sans, permanentIdentifier)
+		}
+	}
+
+	return
+}
+
+//	OtherName ::= SEQUENCE {
+//	  type-id    OBJECT IDENTIFIER,
+//	  value      [0] EXPLICIT ANY DEFINED BY type-id }
+type otherName struct {
+	TypeID asn1.ObjectIdentifier
+	Value  asn1.RawValue
+}
+
+// https://datatracker.ietf.org/doc/html/rfc5280#page-35
+func parseSubjectAltName(ext pkix.Extension) (dirNames []pkix.Name, otherNames []otherName, err error) {
+	err = forEachSAN(ext.Value, func(generalName asn1.RawValue) error {
+		switch generalName.Tag {
+		case 0: // otherName
+			var otherName otherName
+			if _, err := asn1.UnmarshalWithParams(generalName.FullBytes, &otherName, "tag:0"); err != nil {
+				return fmt.Errorf("OtherName: asn1.UnmarshalWithParams: %v", err)
+			}
+			otherNames = append(otherNames, otherName)
+		case 4: // directoryName
+			var rdns pkix.RDNSequence
+			if _, err := asn1.Unmarshal(generalName.Bytes, &rdns); err != nil {
+				return fmt.Errorf("DirectoryName: asn1.Unmarshal: %v", err)
+			}
+			var dirName pkix.Name
+			dirName.FillFromRDNSequence(&rdns)
+			dirNames = append(dirNames, dirName)
+		default:
+			//return fmt.Errorf("expected tag %d", generalName.Tag)
+			// TODO(hs): implement the others ... skipping for now
+		}
+		return nil
+	})
+	return
+}
+
+// Borrowed from the x509 package.
+func forEachSAN(extension []byte, callback func(ext asn1.RawValue) error) error {
+	var seq asn1.RawValue
+	rest, err := asn1.Unmarshal(extension, &seq)
+	if err != nil {
+		return err
+	} else if len(rest) != 0 {
+		return errors.New("x509: trailing data after X.509 extension")
+	}
+	if !seq.IsCompound || seq.Tag != 16 || seq.Class != 0 {
+		return asn1.StructuralError{Msg: "bad SAN sequence"}
+	}
+
+	rest = seq.Bytes
+	for len(rest) > 0 {
+		var v asn1.RawValue
+		rest, err = asn1.Unmarshal(rest, &v)
+		if err != nil {
+			return err
+		}
+
+		if err := callback(v); err != nil {
+			return err
+		}
+	}
+
+	return nil
+}
+
 // Apple Enterprise Attestation Root CA from
 // https://www.apple.com/certificateauthority/private/
 const appleEnterpriseAttestationRootCA = `-----BEGIN CERTIFICATE-----

acme/challenge_tpmsimulator_test.go

@@ -9,10 +9,12 @@ import (
 	"crypto/sha256"
 	"crypto/x509"
 	"crypto/x509/pkix"
+	"encoding/asn1"
 	"encoding/base64"
 	"encoding/json"
 	"encoding/pem"
 	"errors"
+	"fmt"
 	"net/url"
 	"testing"
 
@@ -27,6 +29,7 @@ import (
 	"go.step.sm/crypto/tpm"
 	"go.step.sm/crypto/tpm/simulator"
 	tpmstorage "go.step.sm/crypto/tpm/storage"
+	"go.step.sm/crypto/x509util"
 )
 
 func newSimulatedTPM(t *testing.T) *tpm.TPM {
@@ -61,7 +64,7 @@ func generateKeyID(t *testing.T, pub crypto.PublicKey) []byte {
 	return hash[:]
 }
 
-func mustAttestTPM(t *testing.T, keyAuthorization string) ([]byte, crypto.Signer, *x509.Certificate) {
+func mustAttestTPM(t *testing.T, keyAuthorization string, permanentIdentifiers []string) ([]byte, crypto.Signer, *x509.Certificate) {
 	t.Helper()
 	aca, err := minica.New(
 		minica.WithName("TPM Testing"),
@@ -90,13 +93,26 @@ func mustAttestTPM(t *testing.T, keyAuthorization string) ([]byte, crypto.Signer
 	// create template and sign certificate for the AK public key
 	keyID := generateKeyID(t, eks[0].Public())
 	template := &x509.Certificate{
-		Subject: pkix.Name{
-			CommonName: "testakcert",
-		},
 		PublicKey: akp.Public,
-		URIs: []*url.URL{
+	}
+	if len(permanentIdentifiers) == 0 {
+		template.URIs = []*url.URL{
 			{Scheme: "urn", Opaque: "ek:sha256:" + base64.StdEncoding.EncodeToString(keyID)},
-		},
+		}
+	} else {
+		san := x509util.SubjectAlternativeName{
+			Type:  x509util.PermanentIdentifierType,
+			Value: permanentIdentifiers[0], // TODO(hs): multiple?
+		}
+		ext, err := createSubjectAltNameExtension(nil, nil, nil, nil, []x509util.SubjectAlternativeName{san}, true)
+		require.NoError(t, err)
+		template.ExtraExtensions = append(template.ExtraExtensions,
+			pkix.Extension{
+				Id:       asn1.ObjectIdentifier(ext.ID),
+				Critical: ext.Critical,
+				Value:    ext.Value,
+			},
+		)
 	}
 	akCert, err := aca.Sign(template)
 	require.NoError(t, err)
@@ -168,8 +184,8 @@ func Test_deviceAttest01ValidateWithTPMSimulator(t *testing.T) {
 	}
 	tests := map[string]func(t *testing.T) test{
 		"ok/doTPMAttestationFormat-storeError": func(t *testing.T) test {
-			_, keyAuth := mustAccountAndKeyAuthorization(t, "token")
-			payload, _, root := mustAttestTPM(t, keyAuth) // TODO: value(s) for AK cert?
+			jwk, keyAuth := mustAccountAndKeyAuthorization(t, "token")
+			payload, _, root := mustAttestTPM(t, keyAuth, nil) // TODO: value(s) for AK cert?
 			caRoot := pem.EncodeToMemory(&pem.Block{Type: "CERTIFICATE", Bytes: root.Raw})
 			ctx := NewProvisionerContext(context.Background(), mustAttestationProvisioner(t, caRoot))
 
@@ -200,6 +216,7 @@ func Test_deviceAttest01ValidateWithTPMSimulator(t *testing.T) {
 			return test{
 				args: args{
 					ctx: ctx,
+					jwk: jwk,
 					ch: &Challenge{
 						ID:              "chID",
 						AuthorizationID: "azID",
@@ -236,9 +253,102 @@ func Test_deviceAttest01ValidateWithTPMSimulator(t *testing.T) {
 				wantErr: nil,
 			}
 		},
+		"ok with invalid PermanentIdentifier SAN": func(t *testing.T) test {
+			jwk, keyAuth := mustAccountAndKeyAuthorization(t, "token")
+			payload, _, root := mustAttestTPM(t, keyAuth, []string{"device.id.12345678"}) // TODO: value(s) for AK cert?
+			caRoot := pem.EncodeToMemory(&pem.Block{Type: "CERTIFICATE", Bytes: root.Raw})
+			ctx := NewProvisionerContext(context.Background(), mustAttestationProvisioner(t, caRoot))
+			return test{
+				args: args{
+					ctx: ctx,
+					jwk: jwk,
+					ch: &Challenge{
+						ID:              "chID",
+						AuthorizationID: "azID",
+						Token:           "token",
+						Type:            "device-attest-01",
+						Status:          StatusPending,
+						Value:           "device.id.99999999",
+					},
+					payload: payload,
+					db: &MockDB{
+						MockGetAuthorization: func(ctx context.Context, id string) (*Authorization, error) {
+							assert.Equal(t, "azID", id)
+							return &Authorization{ID: "azID"}, nil
+						},
+						MockUpdateChallenge: func(ctx context.Context, updch *Challenge) error {
+							assert.Equal(t, "chID", updch.ID)
+							assert.Equal(t, "token", updch.Token)
+							assert.Equal(t, StatusInvalid, updch.Status)
+							assert.Equal(t, ChallengeType("device-attest-01"), updch.Type)
+							assert.Equal(t, "device.id.99999999", updch.Value)
+
+							err := NewError(ErrorRejectedIdentifierType, `permanent identifier does not match`).
+								AddSubproblems(NewSubproblemWithIdentifier(
+									ErrorMalformedType,
+									Identifier{Type: "permanent-identifier", Value: "device.id.99999999"},
+									`challenge identifier "device.id.99999999" doesn't match any of the attested hardware identifiers ["device.id.12345678"]`,
+								))
+
+							assert.EqualError(t, updch.Error.Err, err.Err.Error())
+							assert.Equal(t, err.Type, updch.Error.Type)
+							assert.Equal(t, err.Detail, updch.Error.Detail)
+							assert.Equal(t, err.Status, updch.Error.Status)
+							assert.Equal(t, err.Subproblems, updch.Error.Subproblems)
+
+							return nil
+						},
+					},
+				},
+				wantErr: nil,
+			}
+		},
 		"ok": func(t *testing.T) test {
 			jwk, keyAuth := mustAccountAndKeyAuthorization(t, "token")
-			payload, signer, root := mustAttestTPM(t, keyAuth) // TODO: value(s) for AK cert?
+			payload, signer, root := mustAttestTPM(t, keyAuth, nil) // TODO: value(s) for AK cert?
+			caRoot := pem.EncodeToMemory(&pem.Block{Type: "CERTIFICATE", Bytes: root.Raw})
+			ctx := NewProvisionerContext(context.Background(), mustAttestationProvisioner(t, caRoot))
+			return test{
+				args: args{
+					ctx: ctx,
+					jwk: jwk,
+					ch: &Challenge{
+						ID:              "chID",
+						AuthorizationID: "azID",
+						Token:           "token",
+						Type:            "device-attest-01",
+						Status:          StatusPending,
+						Value:           "device.id.12345678",
+					},
+					payload: payload,
+					db: &MockDB{
+						MockGetAuthorization: func(ctx context.Context, id string) (*Authorization, error) {
+							assert.Equal(t, "azID", id)
+							return &Authorization{ID: "azID"}, nil
+						},
+						MockUpdateAuthorization: func(ctx context.Context, az *Authorization) error {
+							fingerprint, err := keyutil.Fingerprint(signer.Public())
+							assert.NoError(t, err)
+							assert.Equal(t, "azID", az.ID)
+							assert.Equal(t, fingerprint, az.Fingerprint)
+							return nil
+						},
+						MockUpdateChallenge: func(ctx context.Context, updch *Challenge) error {
+							assert.Equal(t, "chID", updch.ID)
+							assert.Equal(t, "token", updch.Token)
+							assert.Equal(t, StatusValid, updch.Status)
+							assert.Equal(t, ChallengeType("device-attest-01"), updch.Type)
+							assert.Equal(t, "device.id.12345678", updch.Value)
+							return nil
+						},
+					},
+				},
+				wantErr: nil,
+			}
+		},
+		"ok with PermanentIdentifier SAN": func(t *testing.T) test {
+			jwk, keyAuth := mustAccountAndKeyAuthorization(t, "token")
+			payload, signer, root := mustAttestTPM(t, keyAuth, []string{"device.id.12345678"}) // TODO: value(s) for AK cert?
 			caRoot := pem.EncodeToMemory(&pem.Block{Type: "CERTIFICATE", Bytes: root.Raw})
 			ctx := NewProvisionerContext(context.Background(), mustAttestationProvisioner(t, caRoot))
 			return test{
@@ -341,9 +451,6 @@ func Test_doTPMAttestationFormat(t *testing.T) {
 	// create template and sign certificate for the AK public key
 	keyID := generateKeyID(t, eks[0].Public())
 	template := &x509.Certificate{
-		Subject: pkix.Name{
-			CommonName: "testakcert",
-		},
 		PublicKey: akp.Public,
 		URIs: []*url.URL{
 			{Scheme: "urn", Opaque: "ek:sha256:" + base64.StdEncoding.EncodeToString(keyID)},
@@ -739,3 +846,82 @@ 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. 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
+}