Getting Started

Installation

You can install Flask-HTTPAuth with pip:

pip install flask-httpauth

Basic authentication example

The following example application uses HTTP Basic authentication to protect route '/':

from flask import Flask
from flask_httpauth import HTTPBasicAuth
from werkzeug.security import generate_password_hash, check_password_hash

app = Flask(__name__)
auth = HTTPBasicAuth()

users = {
    "john": generate_password_hash("hello"),
    "susan": generate_password_hash("bye")
}

@auth.verify_password
def verify_password(username, password):
    if username in users and \
            check_password_hash(users.get(username), password):
        return username

@app.route('/')
@auth.login_required
def index():
    return "Hello, {}!".format(auth.current_user())

if __name__ == '__main__':
    app.run()

The function decorated with the verify_password decorator receives the username and password sent by the client. If the credentials belong to a user, then the function should return the user object. If the credentials are invalid the function can return None or False. The user object can then be queried from the current_user() method of the authentication instance.

Digest authentication example

The following example uses HTTP Digest authentication:

from flask import Flask
from flask_httpauth import HTTPDigestAuth

app = Flask(__name__)
app.config['SECRET_KEY'] = 'secret key here'
auth = HTTPDigestAuth()

users = {
    "john": "hello",
    "susan": "bye"
}

@auth.get_password
def get_pw(username):
    if username in users:
        return users.get(username)
    return None

@app.route('/')
@auth.login_required
def index():
    return "Hello, {}!".format(auth.username())

if __name__ == '__main__':
    app.run()

Token Authentication Example

The following example application uses a custom HTTP authentication scheme to protect route '/' with a token:

from flask import Flask
from flask_httpauth import HTTPTokenAuth

app = Flask(__name__)
auth = HTTPTokenAuth(scheme='Bearer')

tokens = {
    "secret-token-1": "john",
    "secret-token-2": "susan"
}

@auth.verify_token
def verify_token(token):
    if token in tokens:
        return tokens[token]

@app.route('/')
@auth.login_required
def index():
    return "Hello, {}!".format(auth.current_user())

if __name__ == '__main__':
    app.run()

The HTTPTokenAuth is a generic authentication handler that can be used with non-standard authentication schemes, with the scheme name given as an argument in the constructor. In the above example, the WWW-Authenticate header provided by the server will use Bearer as scheme:

WWW-Authenticate: Bearer realm="Authentication Required"

The verify_token callback receives the authentication credentials provided by the client on the Authorization header. This can be a simple token, or can contain multiple arguments, which the function will have to parse and extract from the string. As with the verify_password, the function should return the user object if the token is valid.

In the examples directory you can find a complete example that uses JWS tokens. JWS tokens are similar to JWT tokens. However using JWT tokens would require an external dependency.

Using Multiple Authentication Schemes

Applications sometimes need to support a combination of authentication methods. For example, a web application could be authenticated by sending client id and secret over basic authentication, while third party API clients use a JWS or JWT bearer token. The MultiAuth class allows you to protect a route with more than one authentication object. To grant access to the endpoint, one of the authentication methods must validate.

In the examples directory you can find a complete example that uses basic and token authentication.

User Roles

Flask-HTTPAuth includes a simple role-based authentication system that can optionally be added to provide an additional layer of granularity in filtering accesses to routes. To enable role support, write a function that returns the list of roles for a given user and decorate it with the get_user_roles decorator:

@auth.get_user_roles
def get_user_roles(user):
    return user.get_roles()

To restrict access to a route to users having a given role, add the role argument to the login_required decorator:

@app.route('/admin')
@auth.login_required(role='admin')
def admins_only():
    return "Hello {}, you are an admin!".format(auth.current_user())

The role argument can take a list of roles, in which case users who have any of the given roles will be granted access:

@app.route('/admin')
@auth.login_required(role=['admin', 'moderator'])
def admins_only():
    return "Hello {}, you are an admin or a moderator!".format(auth.current_user())

In the most advanced usage, users can be filtered by having multiple roles:

@app.route('/admin')
@auth.login_required(role=['user', ['moderator', 'contributor']])
def admins_only():
    return "Hello {}, you are a user or a moderator/contributor!".format(auth.current_user())

Deployment Considerations

Be aware that some web servers do not pass the Authorization headers to the WSGI application by default. For example, if you use Apache with mod_wsgi, you have to set option WSGIPassAuthorization On as documented here.

Deprecated Basic Authentication Options

Before the verify_password described above existed there were other simpler mechanisms for implementing basic authentication. While these are deprecated they are still maintained. However, the verify_password callback should be preferred as it provides greater security and flexibility.

The get_password callback needs to return the password associated with the username given as argument. Flask-HTTPAuth will allow access only if get_password(username) == password. Example:

@auth.get_password
def get_password(username):
    return get_password_for_username(username)

Using this callback alone is in general not a good idea because it requires passwords to be available in plaintext in the server. In the more likely scenario that the passwords are stored hashed in a user database, then an additional callback is needed to define how to hash a password:

@auth.hash_password
def hash_pw(password):
    return hash_password(password)

In this example, you have to replace hash_password() with the specific hashing function used in your application. When the hash_password callback is provided, access will be granted when get_password(username) == hash_password(password).

If the hashing algorithm requires the username to be known then the callback can take two arguments instead of one:

@auth.hash_password
def hash_pw(username, password):
    salt = get_salt(username)
    return hash_password(password, salt)