yaftp: Yet another file transfer protocol

Weiwen Chen's fifth project of Computer Network course in FDU.

A simple ftp-like file transfer protocol package.

Simple ui: https://github.com/ofey404/yaftp-ui

Usage

Installation

git clone https://github.com/ofey404/yaftp.git
cd yaftp
pip install -e .

Then you can use yaftp package in python:

$ python
Python 3.9.1 (default, Dec  8 2020, 00:00:00) 
[GCC 10.2.1 20201125 (Red Hat 10.2.1-9)] on linux
Type "help", "copyright", "credits" or "license" for more information.
>>> import yaftp
>>> 

Set up a server

import yaftp

yaftp.YAFTPServer(
    address=("127.0.0.1", 2121),
    local_dir="tests/data",
    auth={
        "USER": "PASSWORD",
        "OFEY": "404",
        "ANONYMOUS": ""   # Blank means login without password
    }
).serve()

Interact with a server

import yaftp

c = yaftp.YAFTP(
    address=("127.0.0.1", 2121),
    user="USER",
    passwd="PASSWORD"
)

c.login()
# Out[2]: 230

c.dir()
# Out[3]: ['test_folder/', 'hello.txt']

c.get(name="hello.txt", savepath="saved_file")
# Out[4]: 213

%cat saved_file
# hello from the other side!

c.send(filepath="saved_file", name="hey.txt")
# Out[6]: 213

c.dir()
# Out[7]: ['test_folder/', 'hello.txt', 'hey.txt']

c.cd(path="test_folder")
# Out[8]: 212

c.dir()
# Out[9]: ['hey.txt']

c.quit()
# Out[10]: 231

Implementation detail

Super simple, just a toy, never care about performance.

Use async event loop to handle control connection, while firing other threads to deal with data connection.

Commands

• LOGIN USER[:PASSWORD]
• DIR [RELATIVE_PATH]
• PWD
• CD [RELATIVE_PATH]
• GET FILENAME DATA_PORT
  • DATA_PORT should be opened in localhost before command is executed.
• SEND FILENAME DATA_PORT
  • DATA_PORT: same as above.
• DELETE FILENAME
• BYE

Only support active mode

Implemented a ftp-like active mode, because it's easy, without much synchronizaion effort.

When sending or getting a file:

• Client open a local data port, listening.
• Client -- request --> Server
  • request specify the data port.
• Server -- connect --> Client:data_port
  • then send file.

Vulnerabilities

I've try my best on error handling and prevent secure vulnerabilitys, like:

• Prevent user dir or cd beyond root directory.

But I'm sure that's not enough, this library must be full of holes.

Reference

• https://en.wikipedia.org/wiki/List_of_FTP_server_return_codes

API Design refer to:

• https://docs.python.org/3/library/ftplib.html
• https://pyftpdlib.readthedocs.io/en/latest/index.html