From 7766b079c8fd004fee9d5eba19cb98cac568773b Mon Sep 17 00:00:00 2001
From: Anatol Pomozov <anatol.pomozov@gmail.com>
Date: Thu, 23 Mar 2023 18:49:14 -0700
Subject: [PATCH] generator: Do not rely on user's lookup order for binaries

Until now we used `exec.LookPath` golang function to lookup binaries.
This function depends on user's $PATH envvar and the order directories
specified there. This could mess with our image symlink tree.

What we want is to make sure that we lookup/add files at non-symlinked
directories first (i.e. /usr/bin).

Closes #213
---
 generator/generator.go      | 28 ++++++++++++++++++++++++++--
 generator/generator_test.go |  6 ++++++
 2 files changed, 32 insertions(+), 2 deletions(-)

diff --git a/generator/generator.go b/generator/generator.go
index 0ab135c..8f0a72f 100644
--- a/generator/generator.go
+++ b/generator/generator.go
@@ -5,7 +5,6 @@ import (
 	"fmt"
 	"net"
 	"os"
-	"os/exec"
 	"path/filepath"
 	"time"
 
@@ -290,7 +289,7 @@ func (img *Image) appendExtraFiles(binaries ...string) error {
 			// If the given name is not an absolute path, assume that it refers
 			// to an executable and lookup the path to the executable using $PATH.
 			var err error
-			f, err = exec.LookPath(f)
+			f, err = lookupPath(f)
 			if err != nil {
 				return err
 			}
@@ -303,6 +302,31 @@ func (img *Image) appendExtraFiles(binaries ...string) error {
 	return nil
 }
 
+func lookupPath(binary string) (string, error) {
+	paths := []string{
+		"/usr/bin",
+		"/usr/sbin",
+		"/bin",
+		"/sbin",
+		"/usr/local/bin",
+		"/usr/local/sbin",
+	}
+
+	for _, p := range paths {
+		f := filepath.Join(p, binary)
+		_, err := os.Stat(f)
+		if os.IsNotExist(err) {
+			continue
+		}
+		if err != nil {
+			return "", err
+		}
+		return f, nil
+	}
+
+	return "", os.ErrNotExist
+}
+
 func findFwFile(fw string) (string, error) {
 	supportedFwExt := []string{
 		"",
diff --git a/generator/generator_test.go b/generator/generator_test.go
index 57b7cce..5938cbc 100644
--- a/generator/generator_test.go
+++ b/generator/generator_test.go
@@ -550,3 +550,9 @@ func TestModprobeOptions(t *testing.T) {
 	}
 	require.Equal(t, expect, cfg.ModprobeOptions)
 }
+
+func TestLookupFile(t *testing.T) {
+	path, err := lookupPath("echo")
+	require.NoError(t, err)
+	require.Equal(t, "/usr/bin/echo", path)
+}