initial commit

.gitignore

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+# Created by https://www.gitignore.io/api/flask
+# Edit at https://www.gitignore.io/?templates=flask
+
+### Flask ###
+instance/*
+!instance/.gitignore
+.webassets-cache
+
+### Flask.Python Stack ###
+# Byte-compiled / optimized / DLL files
+__pycache__/
+*.py[cod]
+*$py.class
+
+# C extensions
+*.so
+
+# Distribution / packaging
+.Python
+build/
+develop-eggs/
+dist/
+downloads/
+eggs/
+.eggs/
+lib/
+lib64/
+parts/
+sdist/
+var/
+wheels/
+pip-wheel-metadata/
+share/python-wheels/
+*.egg-info/
+.installed.cfg
+*.egg
+MANIFEST
+
+# PyInstaller
+#  Usually these files are written by a python script from a template
+#  before PyInstaller builds the exe, so as to inject date/other infos into it.
+*.manifest
+*.spec
+
+# Installer logs
+pip-log.txt
+pip-delete-this-directory.txt
+
+# Unit test / coverage reports
+htmlcov/
+.tox/
+.nox/
+.coverage
+.coverage.*
+.cache
+nosetests.xml
+coverage.xml
+*.cover
+.hypothesis/
+.pytest_cache/
+
+# Translations
+*.mo
+*.pot
+
+# Scrapy stuff:
+.scrapy
+
+# Sphinx documentation
+docs/_build/
+
+# PyBuilder
+target/
+
+# pyenv
+.python-version
+
+# pipenv
+#   According to pypa/pipenv#598, it is recommended to include Pipfile.lock in version control.
+#   However, in case of collaboration, if having platform-specific dependencies or dependencies
+#   having no cross-platform support, pipenv may install dependencies that don't work, or not
+#   install all needed dependencies.
+#Pipfile.lock
+
+# celery beat schedule file
+celerybeat-schedule
+
+# SageMath parsed files
+*.sage.py
+
+# Spyder project settings
+.spyderproject
+.spyproject
+
+# Rope project settings
+.ropeproject
+
+# Mr Developer
+.mr.developer.cfg
+.project
+.pydevproject
+
+# mkdocs documentation
+/site
+
+# mypy
+.mypy_cache/
+.dmypy.json
+dmypy.json
+
+# Pyre type checker
+.pyre/
+
+# End of https://www.gitignore.io/api/flask

Dockerfile

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+FROM python:3.7-slim
+
+ENV PYTHONUNBUFFERED=1
+ENV GUNICORN_CMD_ARGS="--bind=0.0.0.0:8080 --access-logfile=-"
+
+WORKDIR /app
+
+COPY requirements.txt ./
+RUN pip install -r requirements.txt
+
+COPY . .
+
+CMD ["gunicorn", "main:app"]

README.md

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+Based on https://developers.cloudflare.com/access/setting-up-access/validate-jwt-tokens/

main.py

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+from flask import Flask, request
+import requests
+import jwt
+import json
+import os
+app = Flask(__name__)
+
+# Your CF Access Authentication domain
+AUTH_DOMAIN = os.getenv("AUTH_DOMAIN")
+CERTS_URL = "{}/cdn-cgi/access/certs".format(AUTH_DOMAIN)
+
+def _get_public_keys():
+    """
+    Returns:
+        List of RSA public keys usable by PyJWT.
+    """
+    r = requests.get(CERTS_URL)
+    public_keys = []
+    jwk_set = r.json()
+    for key_dict in jwk_set['keys']:
+        public_key = jwt.algorithms.RSAAlgorithm.from_jwk(json.dumps(key_dict))
+        public_keys.append(public_key)
+    return public_keys
+
+@app.route('/token/validate')
+def verify_token():
+    if 'aud' in request.args:
+        aud = request.args['aud']
+    else:
+        return "missing required application audience (AUD) tag", 400
+
+    token = ''
+    if 'CF_Authorization' in request.cookies:
+        token = request.cookies['CF_Authorization']
+    else:
+        return "missing required cf authorization token", 403
+    keys = _get_public_keys()
+
+    # Loop through the keys since we can't pass the key set to the decoder
+    valid_token = False
+    for key in keys:
+        try:
+            # decode returns the claims that has the email when needed
+            jwt.decode(token, key=key, audience=aud)
+            valid_token = True
+            break
+        except:
+            pass
+    if not valid_token:
+        return "invalid token", 403
+
+    return "OK", 200
+
+
+if __name__ == '__main__':
+    app.run()

requirements.txt

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+flask
+requests
+cryptography
+PyJWT
+gunicorn