envoy: Initial changes

internal/envoy/embed.go

@@ -0,0 +1,64 @@
+package envoy
+
+import (
+	"fmt"
+	"os"
+	"path/filepath"
+
+	"github.com/natefinch/atomic"
+	resources "gopkg.in/cookieo9/resources-go.v2"
+)
+
+var embeddedFilesDirectory = filepath.Join(os.TempDir(), "pomerium-embedded-files")
+
+func extractEmbeddedEnvoy() (outPath string, err error) {
+	exePath, err := resources.ExecutablePath()
+	if err != nil {
+		return "", fmt.Errorf("error finding executable path: %w", err)
+	}
+	bundle, err := resources.OpenZip(exePath)
+	if err != nil {
+		return "", fmt.Errorf("error opening binary zip file: %w", err)
+	}
+	defer bundle.Close()
+
+	rc, err := bundle.Open("envoy")
+	if err != nil {
+		return "", fmt.Errorf("error opening embedded envoy binary: %w", err)
+	}
+	defer rc.Close()
+
+	err = os.MkdirAll(embeddedFilesDirectory, 0755)
+	if err != nil {
+		return "", fmt.Errorf("error creating embedded file directory: (directory=%s): %w", embeddedFilesDirectory, err)
+	}
+
+	outPath = filepath.Join(embeddedFilesDirectory, "envoy")
+
+	// skip extraction if we already have it
+	var zfi os.FileInfo
+	if zf, ok := rc.(interface{ FileInfo() os.FileInfo }); ok {
+		zfi = zf.FileInfo()
+		if fi, e := os.Stat(outPath); e == nil {
+			if fi.Size() == zfi.Size() && fi.ModTime() == zfi.ModTime() {
+				return outPath, nil
+			}
+		}
+	}
+
+	err = atomic.WriteFile(outPath, rc)
+	if err != nil {
+		return "", fmt.Errorf("error extracting embedded envoy binary to temporary directory (path=%s): %w", outPath, err)
+	}
+
+	err = os.Chmod(outPath, 0755)
+	if err != nil {
+		return "", fmt.Errorf("error chmoding embedded envoy binary: %w", err)
+	}
+
+	if zfi != nil {
+		_ = os.Chtimes(outPath, zfi.ModTime(), zfi.ModTime())
+	}
+
+	return outPath, nil
+}