Corsproxy is a very small and simple but highly efficient Linux HTTP proxy server which receives a HTTP GET or POST request on a port and forwards that request to a pre-configured target server and port. The proxy server then receives the HTTP reply from that server, and returns it to the original client unaltered except that the HTTP header has the Access-Control-Allow-Origin field set to get around CORS restrictions.
Why another CORS proxy program? Existing CORS proxies I found require the originating client to specify the target host within the incoming URL to the proxy. The proxy dynamically extracts the target host from the URL and then sends the "real" URL to the target. My application use case only allowed me to change the host so I could not "embed" the real host in the target URL. This simple CORS proxy must instead be statically pre-configured with the target server so it knows where to forward incoming requests. E.g.
./corsproxy 8000:192.168.1.1:9000
The above will receive requests on port 8000 and forward them to host 192.168.1.1 on port 9000.
./corsproxy 8000:192.168.1.1:9000 8001:192.168.1.2:9001
This runs 2 proxies. It will do as the previous example but will also independently and asynchronously receive requests on port 8001 and forward them to host 192.168.1.2 on port 9001. You can specify as many proxy mappings as you want.
Instead of specifying the target mappings on the command line as above,
you can instead choose to configure them in your ~/.config/corsproxy
file, either space delimited, or on individual lines, etc. This is
convenient if you are starting the program via
systemd etc. Proxy
mappings are only read from the file if none are specified on the
command line.
The receiving (i.e. listening) port and host/IP address must at least be
specified in each proxy mapping. The target port is optional and is 80
if not specified. The format, as seen in the above examples,
is port:host[:targetport].
The latest version and documentation is available at http://github.com/bulletmark/corsproxy.
Requires Python 3.5 or later on a Linux server (I use a Raspberry Pi).
These instructions assume you are using systemd to start the application. A systemd service service file is provided.
git clone https://github.com/bulletmark/corsproxy
cd corsproxy
python3 -m venv venv
venv/bin/pip install -r requirements.txt
mkdir -p ~/.config
vim ~/.config/corsproxy # Add the target servers
sudo cp corsproxy.service /etc/systemd/system
sudoedit /etc/systemd/system/corsproxy.service # Edit #TEMPLATE# values.To enable starting at boot and also start immediately:
sudo systemctl enable corsproxy
sudo systemctl start corsproxy
To stop immediately and also disable starting at boot:
sudo systemctl stop corsproxy
sudo systemctl disable corsproxy
Show status:
systemctl status corsproxy
Show log:
journalctl -u corsproxy
cd to source directory, as above. Then update the source:
git pull
Update ~/.config/corsproxy and /etc/systemd/system/corsproxy.service if
necessary. Then restart the service.
sudo systemctl restart corsproxy
Alternatively, for many users it may be easier to install and run this
application using Docker. Follow
your Linux distribution's instructions to ensure Docker is
installed and enabled to
automatically start at boot. Also ensure you add your
user to the
docker group.
The Docker image is available on Docker Hub. Run the following command:
docker run --restart always -d -p 8000:8000 bulletmark/corsproxy 8000:192.168.1.98
Be sure to change the target host mapping to what you require. The image is available for amd64, arm64, and arm/v7 architectures. E.g. on a standard PC, or on a Raspberry Pi, just run the above single command and docker will download, install, and run the appropriate image. Docker will also restart the corsproxy container when your system starts.
Type corsproxy -h to view the following usage summary:
usage: corsproxy [-h] [targets ...]
Provides a simple CORS proxy for GET and POST requests. Reads list of target
port:host[:targetport] from the command line, or from your config file.
positional arguments:
targets 1 or more proxy target hosts in port:host[:targetport] format.
if not set then will try to read from
~/.config/corsproxy file.
options:
-h, --help show this help message and exit
Copyright (C) 2019 Mark Blakeney. This program is distributed under the terms of the GNU General Public License. This program is free software: you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation, either version 3 of the License, or any later version. This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License at http://www.gnu.org/licenses/ for more details.