How to create new user accounts in python eve api secured with User-Restricted Resource Access

Question

I first created a web api using the python-eve framework, without authentication or user accounts, and it worked great! I am now trying to add authentication and user accounts, and am having some difficulty. I want to use User-Restricted Resource Access, but how can a user create a new user account, if the resources are restricted? What am I missing?

I have been trying to follow the Restful Account Management Tutorial and the introduction to Authentication and Authorization on python-eve.org, and I've searched stackoverflow, including this answer here.

Here is my implementation:

run.py

import os.path
from eve import Eve
import my_auth
from flask.ext.bootstrap import Bootstrap
from eve_docs import eve_docs

app = Eve(auth=my_auth.BCryptAuth, settings = 'deployed_settings.py')

app.on_insert_accounts += my_auth.create_user
Bootstrap(app)
app.register_blueprint(eve_docs, url_prefix='/docs')

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

my_auth.py

import bcrypt
from eve import Eve
from eve.auth import BasicAuth 

class BCryptAuth(BasicAuth):
    def check_auth(self, username, password, allowed_roles, resource, method):
         # use Eve's own db driver; no additional connections/resources are used
         accounts = Eve.app.data.driver.db['accounts']
         account = accounts.find_one({'username': username})
         if account and 'user_id' in account:
             self.set_request_auth_value(account['user_id'])
         return account and bcrypt.hashpw(
             password.encode('utf-8'),account['salt'].encode('utf-8')) == account['password']

def create_user(documents):
    for document in documents:
        document['salt'] = bcrypt.gensalt().encode('utf-8')
        password = document['password'].encode('utf-8')
        document['password'] = bcrypt.hashpw(password, document['salt'])

deployed_settings.py

# We are running on a local machine, so just use the local mongod instance.
# Note that MONGO_HOST and MONGO_PORT could very well be left
# out as they already default to a bare bones local 'mongod' instance.
MONGO_HOST = 'localhost'
MONGO_PORT = 27017
MONGO_USERNAME = ''
MONGO_PASSWORD = ''
MONGO_DBNAME = 'practice'

# Name of the field used to store the owner of each document
AUTH_FIELD = 'user_id'

# Enable reads (GET), inserts (POST) and DELETE for resources/collections
# (if you omit this line, the API will default to ['GET'] and provide
# read-only access to the endpoint).
RESOURCE_METHODS = ['GET', 'POST', 'DELETE']

# Enable reads (GET), edits (PATCH), replacements (PUT) and deletes of
# individual items  (defaults to read-only item access).
ITEM_METHODS = ['GET', 'PATCH', 'PUT', 'DELETE']
IF_MATCH = False  # When set to false, older versions may potentially replace newer versions

XML = False  # disable xml output

# Schemas for data objects are defined here:

classes = {
# ... Contents omitted for this question
}

people = {
# ... Contents omitted for this question
}

logs = {
# ... Contents omitted for this question
}

sessions = {
# ... Contents omitted for this question
}


accounts = {
    # the standard account entry point is defined as '/accounts/<ObjectId>'.
    # an additional read-only entry point is accessible at '/accounts/<username>'.
    'additional_lookup': {
        'url': 'regex("[\w]+")',
        'field': 'username',
    },

    # disable endpoint caching to prevent apps from caching account data
    'cache_control': '',
    'cache_expires': 0,

    # schema for the accounts endpoint
    'schema': {
        'username': {
            'type': 'string',
            'required': True,
            'unique': True,
        },
        'password': {
            'type': 'string',
            'required': True,
        },
    },
}

# The DOMAIN dict explains which resources will be available and how they will
# be accessible to the API consumer.
DOMAIN = {
    'classes': classes,
    'people': people,
    'logs': logs,
    'sessions': sessions,
    'accounts': accounts,
}

Answer 1

One simple solution would be to not restrict your user creation method. Something like so:

class BCryptAuth(BasicAuth):
    def check_auth(self, username, password, allowed_roles, resource, method):

        # allow anyone to create a new account.
        if resource == 'accounts' and method == 'POST':
            return True

        accounts = Eve.app.data.driver.db['accounts']
        account = accounts.find_one({'username': username})
        if account and 'user_id' in account:
           self.set_request_auth_value(account['user_id'])
        return account and bcrypt.hashpw(password.encode('utf-8'),account['salt'].encode('utf-8')) == account['password']

Alternatively, and especially so if you only allow POSTing to the account endpoint, you could opt out of authentication for the endpoint:

'accounts': {
    # or you could provide a different custom class here, 
    # so you don't need the guard in the general-purpose auth class.
    'authentication': None,
    ...
}

Hope this helps.