Run flask application over HTTPS

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flask_ssl

Skill - Run flask application over HTTPS

Table of Contents

Skills Required

Please make sure to have all the skills mentioned above to understand and execute the code mentioned below. Go through the above skills if necessary for reference or revision

  • In this post we will learn how to run a flask application over HTTPS

“adhoc” option for quick and testing purposes

from flask import Flask

# create a server instance
app = Flask(__name__)

@app.route('/')
def index():
    return "Hello World!!!"

# run the server
app.run(host="0.0.0.0", port=50100, debug=True, ssl_context="adhoc")
  • As shown in the above code, add an input ssl_context="adhoc" in the app.run function.
  • This will run the flask application over HTTPS with a dummy SSL certificate
  • This method is very easy and useful for development purposes

Generate a self-signed SSL certificate using OpenSSL command line utility

  • For development purposes, OpenSSL can be used to create a self-signed SSL certificate and generate it’s pem and key files using the following command
  • OpenSSL for windows can be downloaded from https://slproweb.com/products/Win32OpenSSL.html
"C:\Program Files\OpenSSL-Win64\bin\openssl.exe" req -x509 -newkey rsa:4096 -nodes -out cert.pem -keyout key.pem -days 3650
  • This command generates pem and cert files valid for 3650 days (10 years)
  • If git is installed in the windows machine, then openssl.exe can be found at C:\Program Files\Git\usr\bin\openssl.exe . Using the below command, openssl in git can be used to generate the self-signed SSL certificate files
"C:\Program Files\Git\usr\bin\openssl.exe" req -x509 -newkey rsa:4096 -nodes -out cert.pem -keyout key.pem -days 3650

Using .key and .pem files for HTTPS in flask

  • key and pem files can be generated from an SSL certificate or generated from a utility like OpenSSL
  • pem file is the certificate file and key file is the private key file of the SSL certificate
from flask import Flask

# create a server instance
app = Flask(__name__)

@app.route('/')
def index():
    return "Hello World!!!"

# run the server
app.run(host="0.0.0.0", port=50100, debug=True, ssl_context=('cert.pem', 'key.pem'))
  • As shown in the above code using ssl_context=('cert.pem', 'key.pem') in app.run function can run the application over HTTPS with cert and pem files of the SSL certificate
  • If cert and pem files are present in a separate folder say C:\taming_python\flask_iis, then
    ssl_context=('C:\\taming_python\\flask_iis\\cert.pem', 'C:\\taming_python\\flask_iis\\key.pem') can be used

Best Practice for production scenarios

  • Although we have learnt how to use SSL in flask application, in production scenarios, it is better use SSL in a reverse proxy like Nginx or IIS and place the flask application behind the reverse proxy
  • A post on how to host a flask application behind IIS as a reverse proxy can be found here

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Video

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References

Location: Mumbai, Maharashtra, India

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