Monday, 5 February 2018

A small HTTP server in Python

The Python http.server module can be run from the commandline with

python3 -m http.server

to provide a simple http server that listens on a configurable port and basically serves any file from the directory it is started from.

That is a good start but I had some additional requirements to serve up files from my raspberry Pi:

  • The server must be able to run as a demonized process, i.e, in the background
  • It must server a limited set of files
  • from a configurable directory and
  • be able to run as a less privileged user
Now of course I could have opted for a light weight http server like nginx or lighttpd, but I decided to write my own so I wouldn't have to install a boatload of additional packages.

restrictedhttpserver.py

The server is based on the daemon module a wrote about in a previous article and can be started from the commandline in much the same way as http.server:


python3 restrictedhttpserver.py


It will run as the user that started it, will listen on port 8000 and start serving any file from the current directory. It will demonize itself as well.

It takes some additional options:

python3 restrictedhttpserver.py -h

usage: restrictedhttpserver.py [-h] [-p PID_FILE] [-l LOG_FILE] [-r ROOT_DIR]
                               [-n NAME] [-u USER] [-f] [-s] [-d]
                               [--bind ADDRESS] [-x] [-e EXT]
                               [port]

Example HTTP Server

positional arguments:
  port                  Specify alternate port [default: 8000]

optional arguments:
  -h, --help            show this help message and exit
  -p PID_FILE, --pid-file PID_FILE
  -l LOG_FILE, --log-file LOG_FILE
  -r ROOT_DIR, --root-dir ROOT_DIR
  -n NAME, --name NAME  name of the server used in log lines
  -u USER, --user USER  drop privileges of running server to those of user
  -f, --force           start a server even if pid file is present already
  -s, --stop            stop a running server
  -d, --debug           Run http server in foreground mode
  --bind ADDRESS, -b ADDRESS
                        Specify alternate bind address [default: all
                        interfaces]
  -x, --nodirlist       never show a directory listing
  -e EXT, --ext EXT     allowed file extensions (without .) May occur more
                        than once
For example if you wanted to run it as user www from the directory /public/www and just server html and css files, you could run it (as root) as follows:

python3 restrictedhttpserver.py -r /public/www -u www -e html -e css

Later you could stop this process by executing
python3 retrictedhttpserver.py -s


For more information have a look at the source code, it is pretty readable I think :-)

Availability

restrictedhttpserver.py and daemon.py are both available from this GitHub repository.

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