Basic authentication

    import web
    import re
    import base64

    urls = (
        '/','Index',
        '/login','Login'
    )

    app = web.application(urls,globals())

    allowed = (
        ('jon','pass1'),
        ('tom','pass2')
    )

    class Index:
        def GET(self):
            if web.ctx.env.get('HTTP_AUTHORIZATION') is not None:
                return 'This is the index page'
            else:
                raise web.seeother('/login')
    class Login:
        def GET(self):
            auth = web.ctx.env.get('HTTP_AUTHORIZATION')
            authreq = False
            if auth is None:
                authreq = True
            else:
                auth = re.sub('^Basic ','',auth)
                username,password = base64.decodestring(auth).split(':')
                if (username,password) in allowed:
                    raise web.seeother('/')
                else:
                    authreq = True
            if authreq:
                web.header('WWW-Authenticate','Basic realm="Auth example"')
                web.ctx.status = '401 Unauthorized'
                return

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