add readme

README.md

@@ -0,0 +1,49 @@
+# PJL Honeypot
+
+This is a very basic PJL or Jetdirect honeypot created as a byproduct of TUM's honeypot and malware analysis course.
+
+When connecting to it via [PRET](https://github.com/RUB-NDS/PRET), you probably won't notice a difference to other printers, and dropping PCL files will store them in a configurable directory (see usage).
+
+The honeypot is a standalone Python 3 script and is contained in a single file, allowing you to drop it on your existing honeypots easily. Furthermore, you can use the [Dockerfile](Dockerfile) to include it in your honeypot setup conveniently.
+
+## Usage
+
+```bash
+# no args => shows usage
+$ python3 jetdirect.py
+usage: jetdirect.py PORT PCL_DIRECTORY [LOGFILE]
+
+# use it e.g like this to
+# - listen on port 9100
+# - store printed pages in ./prints/
+# - log to ./jetdirect.log
+$ python3 jetdirect.py 9100 ./prints ./jetdirect.log
+```
+
+Additionally, there's a [Makefile](Makefile), which can be used to build and run the honeypot's Docker image:
+
+```bash
+# build the docker image
+$ make build
+
+# run the honeypot
+$ make run
+
+# remove the docker image
+$ make clean
+
+# connect to localhost via telnet
+$ make jetdirect
+```
+
+## Hacking
+
+This honeypot is built around a `commands` dictionary, containing most commands specified in HP's PJL handbook. You can modify that dictionary to match your needs. Commands are traversed via the dictionary, thus `INFO CONFIG` will first go to the `INFO` dictionary, and then search the `CONFIG` key.
+
+Once the honeypot finds a value, it'll interpret it. If it's a plain string, that's what will be sent back to the attacker. If it's a function or lambda, the first argument will be the command string passed in, so you can do your own processing.
+
+The filesystem is stored in `fs`, a read-only dictionary-like structure, allowing traversal and file information. If you want to store actual files in there, simply add their contents via `fs.add_file()`, the "directories" will then be created automatically.
+
+## License
+
+This honeypot is licensed under the [MIT license](LICENSE), so feel free to modify it.