Switch branches/tags
Nothing to show
Find file
Fetching contributors…
Cannot retrieve contributors at this time
166 lines (134 sloc) 5.3 KB
layout title
User Authentication with PostgreSQL database

User Authentication with PostgreSQL database


  • You want a system to authenticate users, with a postgresql database.


  • A user authentication system could have a lot of functions. For this example, we're only going to manage the authentication process, through a postgresql database.


  • for all the web functions, and hashlib to store the passwords securely:

    import web import hashlib

1st: The database

First of all, we need a table for the users. This scheme is very simple, but is enough for a lot of projects.

CREATE TABLE example_users
  id serial NOT NULL,
  user character varying(80) NOT NULL,
  pass character(40) NOT NULL,
  email character varying(100) NOT NULL,
  privilege integer NOT NULL DEFAULT 0,
  CONSTRAINT utilisateur_pkey PRIMARY KEY (id)

2nd: the urls

There will be 2 states during the login/logout session:

  • "Login" is for the login page

  • "Reset" for the logout page.

sessions doesn't work in debug mode because it interfere with reloading. see session_with_reloader for more details.

web.config.debug = False

urls = (
  '/login', 'Login',
  '/reset', 'Reset',
app = web.application(urls, locals())
db = web.database(dbn='postgres', db='YOURDB', user='USERNAME', pw='PASSWORD')

store = web.session.DiskStore('sessions')
session = web.session.Session(app, store,
                              initializer={'login': 0, 'privilege': 0})

3rd: Logged or not logged ?

To manage the access for people who are logged or not is very easy. Just define the logged expression like this, and use it for your login/reset classes:

def logged():
	if session.login==1:
		return True
		return False

4th: Easy Privleges Management

I manage my users in 4 categories: admin+user+reader (logged), and visitors (not logged). The directory template is choosing according to the privilege specified in the table example_users.

def create_render(privilege):
    if logged():
        if privilege == 0:
            render = web.template.render('templates/reader')
        elif privilege == 1:
            render = web.template.render('templates/user')
        elif privilege == 2:
            render = web.template.render('templates/admin')
            render = web.template.render('templates/communs')
        render = web.template.render('templates/communs')
    return render

5th: Login and Reset Python Classes

Now, let's have fun:

  • If you are already logged, you are redirecting to the login_double.html template file
  • Else, to the login.html.

class Login:

    def GET(self):
        if logged():
            render = create_render(session.privilege)
            return '%s' % render.login_double()
            render = create_render(session.privilege)
            return '%s' % render.login()
  • Ok, ok. Now, for the POST(). According to the .html file, we recover the variables posted in the form (see the login.html), and we compare it to the example_users.user row.
  • For security, we don't store passwords in the database directly, but store the hash of the password + salt; this is kind of line one-way encryption, so we can tell if the user's passwords match, but an attacker couldn't figure out what the password was to start with.
  • If the login/pass is ok, redirect to the login_ok.html.
  • If not, redirect to the login_error.html.

    def POST(self):
        name, passwd = web.input().name, web.input().passwd
        ident ='example_users', where='name=$name', vars=locals())[0]
            if hashlib.sha1("sAlT754-"+passwd).hexdigest() == ident['pass']:
                session.login = 1
                session.privilege = ident['privilege']
                render = create_render(session.privilege)
                return render.login_ok()
                session.login = 0
                session.privilege = 0
                render = create_render(session.privilege)
                return render.login_error()
            session.login = 0
            session.privilege = 0
            render = create_render(session.privilege)
            return render.login_error()

For the reset function, we just kill the session, and redirect to the logout.html template file.

class Reset:

    def GET(self):
        session.login = 0
        render = create_render(session.privilege)
        return render.logout()

6th: HTML templates help

Well, I think that nobody will need this, but, I prefer to give all the informations. The most important is the login.html.

<form action="/login" method="POST">
	<table id="login">
			<td>User: </td>
			<td><input type="text" name="user"></td>
			<td>Password: </td>
			<td><input type="password" name="passwd"></td>
			<td><input type="submit" value="LOGIN"></td>

7th: Some problems or questions ?

  • Mail: you can contact me at guillaume(at)process-evolution(dot)fr
  • IRC: #webpy on (pseudo: Ephedrax)
  • Translations: I'm french, and my english is can edit my work
  • Revision: Vayn