Use workaround for windows x509.SystemCertPool() (#4018)

Signed-off-by: Nikki Attea <[email protected]>

asset/fetcher.go

@@ -56,6 +56,8 @@ func httpGet(ctx context.Context, path, trustedCAFile string, headers map[string
 			logger.Errorf("failed to append %s to RootCAs, using system certs only", trustedCAFile)
 		}
 
+		appendCerts(rootCAs)
+
 		client = &http.Client{
 			Transport: &http.Transport{
 				TLSClientConfig: &tls.Config{

asset/fetcher_unix.go

@@ -0,0 +1,7 @@
+// +build !windows
+
+package asset
+
+import "crypto/x509"
+
+func appendCerts(rootCAs *x509.CertPool) {}

asset/fetcher_windows.go

@@ -0,0 +1,45 @@
+// +build windows
+
+package asset
+
+import (
+	"crypto/x509"
+	"syscall"
+	"unsafe"
+)
+
+const (
+	// CRYPT_E_NOT_FOUND is an error code specific to windows cert pool.
+	// See https://github.com/golang/go/issues/16736#issuecomment-540373689.
+	CRYPT_E_NOT_FOUND = 0x80092004
+)
+
+func appendCerts(rootCAs *x509.CertPool) {
+	storeHandle, err := syscall.CertOpenSystemStore(0, syscall.StringToUTF16Ptr("Root"))
+	if err != nil {
+		logger.WithError(err).Error(syscall.GetLastError())
+	}
+
+	var cert *syscall.CertContext
+	for {
+		cert, err = syscall.CertEnumCertificatesInStore(storeHandle, cert)
+		if err != nil {
+			if errno, ok := err.(syscall.Errno); ok {
+				if errno == CRYPT_E_NOT_FOUND {
+					break
+				}
+			}
+			logger.WithError(err).Error(syscall.GetLastError())
+		}
+		if cert == nil {
+			break
+		}
+		// Copy the buf, since ParseCertificate does not create its own copy.
+		buf := (*[1 << 20]byte)(unsafe.Pointer(cert.EncodedCert))[:]
+		buf2 := make([]byte, cert.Length)
+		copy(buf2, buf)
+		if c, err := x509.ParseCertificate(buf2); err == nil {
+			rootCAs.AddCert(c)
+		}
+	}
+}