1 files changed, 33 insertions, 13 deletions

diff --git a/src/crypto/x509/root_windows.go b/src/crypto/x509/root_windows.go
index ebf159c178..94669f229e 100644
--- a/src/crypto/x509/root_windows.go
+++ b/src/crypto/x509/root_windows.go
@@ -88,6 +88,9 @@ func checkChainTrustStatus(c *Certificate, chainCtx *syscall.CertChainContext) e
 		switch status {
 		case syscall.CERT_TRUST_IS_NOT_TIME_VALID:
 			return CertificateInvalidError{c, Expired, ""}
+		case syscall.CERT_TRUST_IS_NOT_VALID_FOR_USAGE:
+			return CertificateInvalidError{c, IncompatibleUsage, ""}
+		// TODO(filippo): surface more error statuses.
 		default:
 			return UnknownAuthorityError{c, nil, nil}
 		}
@@ -138,11 +141,19 @@ func checkChainSSLServerPolicy(c *Certificate, chainCtx *syscall.CertChainContex
 	return nil
 }
 
+// windowsExtKeyUsageOIDs are the C NUL-terminated string representations of the
+// OIDs for use with the Windows API.
+var windowsExtKeyUsageOIDs = make(map[ExtKeyUsage][]byte, len(extKeyUsageOIDs))
+
+func init() {
+	for _, eku := range extKeyUsageOIDs {
+		windowsExtKeyUsageOIDs[eku.extKeyUsage] = []byte(eku.oid.String() + "\x00")
+	}
+}
+
 // systemVerify is like Verify, except that it uses CryptoAPI calls
 // to build certificate chains and verify them.
 func (c *Certificate) systemVerify(opts *VerifyOptions) (chains [][]*Certificate, err error) {
-	hasDNSName := opts != nil && len(opts.DNSName) > 0
-
 	storeCtx, err := createStoreContext(c, opts)
 	if err != nil {
 		return nil, err
@@ -152,17 +163,26 @@ func (c *Certificate) systemVerify(opts *VerifyOptions) (chains [][]*Certificate
 	para := new(syscall.CertChainPara)
 	para.Size = uint32(unsafe.Sizeof(*para))
 
-	// If there's a DNSName set in opts, assume we're verifying
-	// a certificate from a TLS server.
-	if hasDNSName {
-		oids := []*byte{
-			&syscall.OID_PKIX_KP_SERVER_AUTH[0],
-			// Both IE and Chrome allow certificates with
-			// Server Gated Crypto as well. Some certificates
-			// in the wild require them.
-			&syscall.OID_SERVER_GATED_CRYPTO[0],
-			&syscall.OID_SGC_NETSCAPE[0],
+	keyUsages := opts.KeyUsages
+	if len(keyUsages) == 0 {
+		keyUsages = []ExtKeyUsage{ExtKeyUsageServerAuth}
+	}
+	oids := make([]*byte, 0, len(keyUsages))
+	for _, eku := range keyUsages {
+		if eku == ExtKeyUsageAny {
+			oids = nil
+			break
+		}
+		if oid, ok := windowsExtKeyUsageOIDs[eku]; ok {
+			oids = append(oids, &oid[0])
 		}
+		// Like the standard verifier, accept SGC EKUs as equivalent to ServerAuth.
+		if eku == ExtKeyUsageServerAuth {
+			oids = append(oids, &syscall.OID_SERVER_GATED_CRYPTO[0])
+			oids = append(oids, &syscall.OID_SGC_NETSCAPE[0])
+		}
+	}
+	if oids != nil {
 		para.RequestedUsage.Type = syscall.USAGE_MATCH_TYPE_OR
 		para.RequestedUsage.Usage.Length = uint32(len(oids))
 		para.RequestedUsage.Usage.UsageIdentifiers = &oids[0]
@@ -208,7 +228,7 @@ func (c *Certificate) systemVerify(opts *VerifyOptions) (chains [][]*Certificate
 		return nil, err
 	}
 
-	if hasDNSName {
+	if opts != nil && len(opts.DNSName) > 0 {
 		err = checkChainSSLServerPolicy(c, chainCtx, opts)
 		if err != nil {
 			return nil, err