Provided by: python3-flask-httpauth_4.5.0-4_all 
NAME
flask-httpauth - Flask-HTTPAuth Documentation
Flask-HTTPAuth is a Flask extension that simplifies the use of HTTP authentication with Flask routes.
BASIC AUTHENTICATION EXAMPLES
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()
Security Concerns with Digest Authentication
The digest authentication algorithm requires a challenge to be sent to the client for use in encrypting
the password for transmission. This challenge needs to be used again when the password is decoded at the
server, so the challenge information needs to be stored so that it can be recalled later.
By default, Flask-HTTPAuth stores the challenge data in the Flask session. To make the authentication
flow secure when using session storage, it is required that server-side sessions are used instead of the
default Flask cookie based sessions, as this ensures that the challenge data is not at risk of being
captured as it moves in a cookie between server and client. The Flask-Session and Flask-KVSession
extensions are both very good options to implement server-side sessions.
As an alternative to using server-side sessions, an application can implement its own generation and
storage of challenge data. To do this, there are four callback functions that the application needs to
implement:
@auth.generate_nonce
def generate_nonce():
"""Return the nonce value to use for this client."""
pass
@auth.generate_opaque
def generate_opaque():
"""Return the opaque value to use for this client."""
pass
@auth.verify_nonce
def verify_nonce(nonce):
"""Verify that the nonce value sent by the client is correct."""
pass
@auth.verify_opaque
def verify_opaque(opaque):
"""Verify that the opaque value sent by the client is correct."""
pass
For information of what the nonce and opaque values are and how they are used in digest authentication,
consult RFC 2617.
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)
API DOCUMENTATION
class flask_httpauth.HTTPBasicAuth
This class handles HTTP Basic authentication for Flask routes.
__init__(scheme=None, realm=None)
Create a basic authentication object.
If the optional scheme argument is provided, it will be used instead of the standard
"Basic" scheme in the WWW-Authenticate response. A fairly common practice is to use a
custom scheme to prevent browsers from prompting the user to login.
The realm argument can be used to provide an application defined realm with the
WWW-Authenticate header.
verify_password(verify_password_callback)
If defined, this callback function will be called by the framework to verify that the
username and password combination provided by the client are valid. The callback function
takes two arguments, the username and the password. It must return the user object if
credentials are valid, or True if a user object is not available. In case of failed
authentication, it should return None or False. Example usage:
@auth.verify_password
def verify_password(username, password):
user = User.query.filter_by(username).first()
if user and passlib.hash.sha256_crypt.verify(password, user.password_hash):
return user
If this callback is defined, it is also invoked when the request does not have the
Authorization header with user credentials, and in this case both the username and password
arguments are set to empty strings. The application can opt to return True in this case and
that will allow anonymous users access to the route. The callback function can indicate
that the user is anonymous by writing a state variable to flask.g or by checking if
auth.current_user() is None.
Note that when a verify_password callback is provided the get_password and hash_password
callbacks are not used.
get_user_roles(roles_callback)
If defined, this callback function will be called by the framework to obtain the roles
assigned to a given user. The callback function takes a single argument, the user for which
roles are requested. The user object passed to this function will be the one returned by
the verify_callback function. The function should return the role or list of roles that
belong to the user. Example:
@auth.get_user_roles
def get_user_roles(user):
return user.get_roles()
get_password(password_callback)
Deprecated This callback function will be called by the framework to obtain the password
for a given user. Example:
@auth.get_password
def get_password(username):
return db.get_user_password(username)
hash_password(hash_password_callback)
Deprecated If defined, this callback function will be called by the framework to apply a
custom hashing algorithm to the password provided by the client. If this callback isn't
provided the password will be checked unchanged. The callback can take one or two
arguments. The one argument version receives the password to hash, while the two argument
version receives the username and the password in that order. Example single argument
callback:
@auth.hash_password
def hash_password(password):
return md5(password).hexdigest()
Example two argument callback:
@auth.hash_password
def hash_pw(username, password):
salt = get_salt(username)
return hash(password, salt)
error_handler(error_callback)
If defined, this callback function will be called by the framework when it is necessary to
send an authentication error back to the client. The function can take one argument, the
status code of the error, which can be 401 (incorrect credentials) or 403 (correct, but
insufficient credentials). To preserve compatiiblity with older releases of this package,
the function can also be defined without arguments. The return value from this function
must by any accepted response type in Flask routes. If this callback isn't provided a
default error response is generated. Example:
@auth.error_handler
def auth_error(status):
return "Access Denied", status
login_required(view_function_callback)
This callback function will be called when authentication is successful. This will
typically be a Flask view function. Example:
@app.route('/private')
@auth.login_required
def private_page():
return "Only for authorized people!"
An optional role argument can be given to further restrict access by roles. Example:
@app.route('/private')
@auth.login_required(role='admin')
def private_page():
return "Only for admins!"
An optional optional argument can be set to True to allow the route to execute also when
authentication is not included with the request, in which case auth.current_user() will be
set to None. Example:
@app.route('/private')
@auth.login_required(optional=True)
def private_page():
user = auth.current_user()
return "Hello {}!".format(user.name if user is not None else 'anonymous')
current_user()
The user object returned by the verify_password callback on successful authentication. If
no user is returned by the callback, this is set to the username passed by the client.
Example:
@app.route('/')
@auth.login_required
def index():
user = auth.current_user()
return "Hello, {}!".format(user.name)
username()
Deprecated A view function that is protected with this class can access the logged username
through this method. Example:
@app.route('/')
@auth.login_required
def index():
return "Hello, {}!".format(auth.username())
class flask_httpauth.HTTPDigestAuth
This class handles HTTP Digest authentication for Flask routes. The SECRET_KEY configuration must
be set in the Flask application to enable the session to work. Flask by default stores user
sessions in the client as secure cookies, so the client must be able to handle cookies. To make
this authentication method secure, a session interface that writes sessions in the server must be
used.
__init__(self, scheme=None, realm=None, use_ha1_pw=False)
Create a digest authentication object.
If the optional scheme argument is provided, it will be used instead of the "Digest" scheme
in the WWW-Authenticate response. A fairly common practice is to use a custom scheme to
prevent browsers from prompting the user to login.
The realm argument can be used to provide an application defined realm with the
WWW-Authenticate header.
If use_ha1_pw is False, then the get_password callback needs to return the plain text
password for the given user. If use_ha1_pw is True, the get_password callback needs to
return the HA1 value for the given user. The advantage of setting use_ha1_pw to True is
that it allows the application to store the HA1 hash of the password in the user database.
generate_ha1(username, password)
Generate the HA1 hash that can be stored in the user database when use_ha1_pw is set to
True in the constructor.
generate_nonce(nonce_making_callback)
If defined, this callback function will be called by the framework to generate a nonce. If
this is defined, verify_nonce should also be defined.
This can be used to use a state storage mechanism other than the session.
verify_nonce(nonce_verify_callback)
If defined, this callback function will be called by the framework to verify that a nonce
is valid. It will be called with a single argument: the nonce to be verified.
This can be used to use a state storage mechanism other than the session.
generate_opaque(opaque_making_callback)
If defined, this callback function will be called by the framework to generate an opaque
value. If this is defined, verify_opaque should also be defined.
This can be used to use a state storage mechanism other than the session.
verify_opaque(opaque_verify_callback)
If defined, this callback function will be called by the framework to verify that an opaque
value is valid. It will be called with a single argument: the opaque value to be verified.
This can be used to use a state storage mechanism other than the session.
get_password(password_callback)
See basic authentication for documentation and examples.
get_user_roles(roles_callback)
See basic authentication for documentation and examples.
error_handler(error_callback)
See basic authentication for documentation and examples.
login_required(view_function_callback)
See basic authentication for documentation and examples.
current_user()
See basic authentication for documentation and examples.
username()
See basic authentication for documentation and examples.
class flask_httpauth.HTTPTokenAuth
This class handles HTTP authentication with custom schemes for Flask routes.
__init__(scheme='Bearer', realm=None, header=None)
Create a token authentication object.
The scheme argument can be use to specify the scheme to be used in the WWW-Authenticate
response. The Authorization header sent by the client must include this scheme followed by
the token. Example:
Authorization: Bearer this-is-my-token
The realm argument can be used to provide an application defined realm with the
WWW-Authenticate header.
The header argument can be used to specify a custom header instead of Authorization from
where to obtain the token. If a custom header is used, the scheme should not be included.
Example:
X-API-Key: this-is-my-token
verify_token(verify_token_callback)
This callback function will be called by the framework to verify that the credentials sent
by the client with the Authorization header are valid. The callback function takes one
argument, the token provided by the client. The function must return the user object if the
token is valid, or True if a user object is not available. In case of a failed
authentication, the function should return None or False. Example usage:
@auth.verify_token
def verify_token(token):
return User.query.filter_by(token=token).first()
Note that a verify_token callback is required when using this class.
get_user_roles(roles_callback)
See basic authentication for documentation and examples.
error_handler(error_callback)
See basic authentication for documentation and examples.
login_required(view_function_callback)
See basic authentication for documentation and examples.
current_user()
See basic authentication for documentation and examples.
class flask_httpauth.HTTPMultiAuth
This class handles HTTP authentication with custom schemes for Flask routes.
__init__(auth_object, ...)
Create a multiple authentication object.
The arguments are one or more instances of HTTPBasicAuth, HTTPDigestAuth or HTTPTokenAuth.
A route protected with this authentication method will try all the given authentication
objects until one succeeds.
login_required(view_function_callback)
See basic authentication for documentation and examples.
current_user()
See basic authentication for documentation and examples.
AUTHOR
Miguel Grinberg
COPYRIGHT
2022, Miguel Grinberg
Jan 25, 2022 FLASK-HTTPAUTH(3)