fix: resolve extracted minitiad path and preserve binary permissions (#207)

* fix: resolve extracted minitiad path and preserve binary permissions

- Preserve executable permissions during tar extraction so `minitiad` remains runnable after download.
- Make binary detection work before executable permissions are restored, then normalize permissions with `chmod`.
- Add regression coverage for extracted binary discovery and permission preservation.
- Validate the MiniEVM `weave init` flow on both Linux and macOS.

* fix: prevent path traversal during archive extraction

* fix: harden tar extraction and improve regression tests

Author: restorenode

cosmosutils/binary.go

@@ -260,7 +260,7 @@ func getMinitiadBinaryURL(vm, version string) (string, error) {
 }
 
 // FindBinaryDir walks versionDir to find the directory that contains the named
-// executable. This avoids hardcoding assumptions about how a release tarball is
+// binary. This avoids hardcoding assumptions about how a release tarball is
 // structured, so the code stays correct even if a future tarball places the
 // binary inside a subdirectory.
 func FindBinaryDir(versionDir, binaryName string) (string, error) {
@@ -269,7 +269,7 @@ func FindBinaryDir(versionDir, binaryName string) (string, error) {
 		if err != nil {
 			return err
 		}
-		if !info.IsDir() && info.Name() == binaryName && info.Mode()&0o111 != 0 {
+		if !info.IsDir() && info.Name() == binaryName {
 			result = filepath.Dir(path)
 			return filepath.SkipAll
 		}

cosmosutils/binary_test.go

@@ -341,13 +341,17 @@ func TestFindBinaryDir(t *testing.T) {
 			wantRel:    filepath.Join("a", "b", "c"),
 		},
 		{
-			name: "non-executable file is ignored",
+			name: "finds binary before executable permissions are restored",
 			layout: func(root string) {
-				os.MkdirAll(root, 0o755)
-				os.WriteFile(filepath.Join(root, "minitiad"), []byte("data"), 0o644)
+				if err := os.MkdirAll(root, 0o755); err != nil {
+					t.Fatal(err)
+				}
+				if err := os.WriteFile(filepath.Join(root, "minitiad"), []byte("data"), 0o644); err != nil {
+					t.Fatal(err)
+				}
 			},
 			binaryName: "minitiad",
-			wantRel:    "",
+			wantRel:    ".",
 		},
 		{
 			name: "wrong name is ignored",

io/filesystem.go

@@ -38,6 +38,11 @@ func DownloadAndExtractTarGz(url, tarballPath, extractedPath string) error {
 }
 
 func ExtractTarGz(src string, dest string) error {
+	destRoot, err := filepath.Abs(dest)
+	if err != nil {
+		return err
+	}
+
 	file, err := os.Open(src)
 	if err != nil {
 		return err
@@ -60,23 +65,27 @@ func ExtractTarGz(src string, dest string) error {
 			return err
 		}
 
-		target := filepath.Join(dest, header.Name)
+		target, err := safeArchivePath(destRoot, header.Name)
+		if err != nil {
+			return err
+		}
 		switch header.Typeflag {
 		case tar.TypeDir:
 			if err := os.MkdirAll(target, os.ModePerm); err != nil {
 				return err
 			}
 		case tar.TypeReg:
-			file, err := os.Create(target)
-			if err != nil {
+			if err := os.MkdirAll(filepath.Dir(target), os.ModePerm); err != nil {
 				return err
 			}
-			_, err = io.Copy(file, tarReader)
+			file, err := os.OpenFile(target, os.O_CREATE|os.O_TRUNC|os.O_WRONLY, os.FileMode(header.Mode))
 			if err != nil {
 				return err
 			}
-			err = file.Close()
-			if err != nil {
+			if err := writeTarFile(file, tarReader); err != nil {
+				return err
+			}
+			if err := os.Chmod(target, os.FileMode(header.Mode)); err != nil {
 				return err
 			}
 		default:
@@ -86,6 +95,34 @@ func ExtractTarGz(src string, dest string) error {
 	return nil
 }
 
+func writeTarFile(file *os.File, src io.Reader) (err error) {
+	defer func() {
+		if closeErr := file.Close(); err == nil && closeErr != nil {
+			err = closeErr
+		}
+	}()
+
+	_, err = io.Copy(file, src)
+	return err
+}
+
+func safeArchivePath(destRoot, entryName string) (string, error) {
+	cleanName := filepath.Clean(entryName)
+	if cleanName == "." {
+		return destRoot, nil
+	}
+
+	target := filepath.Join(destRoot, cleanName)
+	rel, err := filepath.Rel(destRoot, target)
+	if err != nil {
+		return "", err
+	}
+	if rel == ".." || strings.HasPrefix(rel, ".."+string(filepath.Separator)) {
+		return "", fmt.Errorf("unsafe archive entry path: %s", entryName)
+	}
+	return target, nil
+}
+
 func SetLibraryPaths(binaryDir string) error {
 	envKey, envValue, err := LibraryPathEnv(binaryDir)
 	if err != nil {

io/filesystem_test.go

@@ -1,7 +1,10 @@
 package io
 
 import (
+	"archive/tar"
+	"compress/gzip"
 	"os"
+	"path/filepath"
 	"testing"
 
 	"github.com/stretchr/testify/assert"
@@ -59,6 +62,69 @@ func TestExtractTarGz(t *testing.T) {
 		err := ExtractTarGz("./invalid.tar.gz", "./invalid")
 		assert.Error(t, err)
 	})
+
+	t.Run("PreservesExtractedFileMode", func(t *testing.T) {
+		tmpDir := t.TempDir()
+		tarballPath := filepath.Join(tmpDir, "test.tar.gz")
+		extractDir := filepath.Join(tmpDir, "extract")
+
+		file, err := os.Create(tarballPath)
+		assert.NoError(t, err)
+
+		gzw := gzip.NewWriter(file)
+		tw := tar.NewWriter(gzw)
+
+		content := []byte("#!/bin/sh\necho ok\n")
+		header := &tar.Header{
+			Name:     "minitiad",
+			Mode:     0o755,
+			Size:     int64(len(content)),
+			Typeflag: tar.TypeReg,
+		}
+		assert.NoError(t, tw.WriteHeader(header))
+		_, err = tw.Write(content)
+		assert.NoError(t, err)
+		assert.NoError(t, tw.Close())
+		assert.NoError(t, gzw.Close())
+		assert.NoError(t, file.Close())
+
+		err = ExtractTarGz(tarballPath, extractDir)
+		assert.NoError(t, err)
+
+		info, err := os.Stat(filepath.Join(extractDir, "minitiad"))
+		assert.NoError(t, err)
+		assert.Equal(t, os.FileMode(0o755), info.Mode().Perm())
+	})
+
+	t.Run("RejectsPathTraversalEntries", func(t *testing.T) {
+		tmpDir := t.TempDir()
+		tarballPath := filepath.Join(tmpDir, "test.tar.gz")
+		extractDir := filepath.Join(tmpDir, "extract")
+
+		file, err := os.Create(tarballPath)
+		assert.NoError(t, err)
+
+		gzw := gzip.NewWriter(file)
+		tw := tar.NewWriter(gzw)
+
+		content := []byte("bad\n")
+		header := &tar.Header{
+			Name:     "../escape",
+			Mode:     0o644,
+			Size:     int64(len(content)),
+			Typeflag: tar.TypeReg,
+		}
+		assert.NoError(t, tw.WriteHeader(header))
+		_, err = tw.Write(content)
+		assert.NoError(t, err)
+		assert.NoError(t, tw.Close())
+		assert.NoError(t, gzw.Close())
+		assert.NoError(t, file.Close())
+
+		err = ExtractTarGz(tarballPath, extractDir)
+		assert.Error(t, err)
+		assert.Contains(t, err.Error(), "unsafe archive entry path")
+	})
 }
 
 func TestSetLibraryPaths(t *testing.T) {