WebStack

Annotated examples/Common/Login/__init__.py

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2004-05-29 paulb file changeset files shortlog [project @ 2004-05-29 23:06:28 by paulb] Added a success screen for mod_python, which won't allow redirects and cookies in the same transaction.
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#!/usr/bin/env python
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"An example login screen."
 
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import WebStack.Generic
 
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import md5
 
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class LoginResource:
 
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    "A resource providing a login screen."
 
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    def __init__(self, authenticator, use_redirect=1):
 
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        """
 
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        Initialise the resource with an 'authenticator'. If the optional 'use_redirect'
 
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        flag is set to 0, a confirmation screen is given instead of redirecting the user
 
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        back to the original application.
 
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        """
 
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        self.authenticator = authenticator
 
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        self.use_redirect = use_redirect
 
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    def respond(self, trans):
 
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        fields = trans.get_fields_from_body()
 
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        redirect = ""
 
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        if fields.has_key("redirect"):
 
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            redirects = fields["redirect"]
 
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            redirect = redirects[0]
 
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            if self.authenticator.authenticate(trans):
 
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                if self.use_redirect:
 
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                    trans.set_header_value("Location", redirect)
 
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                    trans.set_response_code(307)
 
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                    return
 
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                else:
 
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                    self._show_success(trans, redirect)
 
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                    return
 
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        else:
 
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            fields = trans.get_fields_from_path()
 
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            if fields.has_key("redirect"):
 
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                redirects = fields["redirect"]
 
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                redirect = redirects[0]
 
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        self._show_login(trans, redirect)
 
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    def _show_login(self, trans, redirect):
 
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        # When authentication fails or is yet to take place, show the login
 
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        # screen.
 
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        trans.set_content_type(WebStack.Generic.ContentType("text/html"))
 
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        out = trans.get_response_stream()
 
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        out.write("""
 
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<html>
 
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  <head>
 
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    <title>Login Example</title>
 
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  </head>
 
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  <body>
 
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    <h1>Login</h1>
 
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    <form method="POST">
 
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      <p>Username: <input name="username" type="text" size="12"/></p>
 
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      <p>Password: <input name="password" type="text" size="12"/></p>
 
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      <p><input name="login" type="submit" value="Login"/></p>
 
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      <input name="redirect" type="hidden" value="%s"/>
 
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    </form>
 
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  </body>
 
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</html>
 
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""" % redirect)
 
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    def _show_success(self, trans, redirect):
 
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        # When authentication fails or is yet to take place, show the login
 
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        # screen.
 
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        trans.set_content_type(WebStack.Generic.ContentType("text/html"))
 
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        out = trans.get_response_stream()
 
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        out.write("""
 
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<html>
 
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  <head>
 
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    <title>Login Example</title>
 
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  </head>
 
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  <body>
 
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    <h1>Login Successful</h1>
 
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    <p>Please proceed <a href="%s">to the application</a>.</p>
 
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  </body>
 
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</html>
 
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""" % redirect)
 
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    def _decode(self, url):
 
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        "Decode the given 'url' for redirection purposes."
 
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        return url.replace("%3f", "?").replace("%26", "&")
 
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class LoginAuthenticator:
 
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    def __init__(self, secret_key, credentials, cookie_name=None):
 
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        """
 
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        Initialise the authenticator with a 'secret_key', the authenticator's registry of
 
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        'credentials' and an optional 'cookie_name'.
 
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        The 'credentials' must be an object which supports tests of the form
 
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        '(username, password) in credentials'.
 
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        """
 
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        self.secret_key = secret_key
 
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        self.credentials = credentials
 
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        self.cookie_name = cookie_name or "LoginAuthenticator"
 
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    def authenticate(self, trans):
 
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        # Process any supplied parameters.
 
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        fields = trans.get_fields_from_body()
 
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        if fields.has_key("username") and fields.has_key("password"):
 
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            usernames, passwords = fields["username"], fields["password"]
 
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            # Insist on only one username and password.
 
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            if len(usernames) == 1 and len(passwords) == 1:
 
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                username, password = usernames[0], passwords[0]
 
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                # Check against the class's credentials.
 
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                if (username, password) in self.credentials:
 
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                    # Make a special cookie token.
 
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                    # NOTE: This should be moved into a common library.
 
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                    trans.set_cookie_value(
 
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                        self.cookie_name,
 
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                        username + ":" + md5.md5(username + self.secret_key).hexdigest()
 
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                    )
 
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                    return 1
 
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        return 0
 
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