plugins: Require an exe extension on windows

plugins/shared/loader/filter_unix.go

@@ -0,0 +1,10 @@
+// +build !windows
+
+package loader
+
+import "os"
+
+// executable Checks to see if the file is executable by anyone.
+func executable(path string, f os.FileInfo) bool {
+	return f.Mode().Perm()&0111 != 0
+}

plugins/shared/loader/filter_windows.go

@@ -0,0 +1,15 @@
+// +build windows
+
+package loader
+
+import (
+	"os"
+	"path/filepath"
+)
+
+// On windows, an executable can be any file with any extension. To avoid
+// introspecting the file, here we skip executability checks on windows systems
+// and simply check for the convention of an `exe` extension.
+func executable(path string, s os.FileInfo) bool {
+	return filepath.Ext(path) == "exe"
+}

plugins/shared/loader/init.go

@@ -5,7 +5,6 @@ import (
 	"os"
 	"os/exec"
 	"path/filepath"
-	"runtime"
 	"sort"
 
 	multierror "github.com/hashicorp/go-multierror"
@@ -251,11 +250,7 @@ func (l *PluginLoader) scan() ([]os.FileInfo, error) {
 			continue
 		}
 
-		// Check if it is executable by anyone. On windows, an executable is any file with any
-		// extension and the file begins with MZ, however, there is no easy way for us to
-		// actually validate the executability of a file, so here we skip executability checks
-		// for windows systems.
-		if runtime.GOOS != "windows" && s.Mode().Perm()&0111 == 0 {
+		if !executable(f, s) {
 			l.logger.Debug("skipping un-executable file in plugin folder", "file", f)
 			continue
 		}