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<<TableOfContents>>

= Authenticate Via External Cookie =

== Requirements ==

The external cookie authentication alternative may be a good choice for your installation if your MoinMoin wiki topic is closely associated with some other application.  You may be using MoinMoin for application documentation, popup help functions, or bug tracking.  Several of your application pages may have hyperlinks to wiki pages.  Wiki pages may contain custom macros that present data from your application database.  Wiki users must login before they can update wiki pages (or you wish that were the case).  Everyone with an application login ID also has a wiki login ID.  Your users are annoyed that they frequently must login twice, first to the other application and then to MoinMoin.  Your administrators are annoyed because they must maintain login IDs in two places.

To authenticate a MoinMoin user with an external cookie, your other application must be modified to create a cookie with each successful login.  It must delete the cookie as part of the logout process.  

In order to prevent hackers from easily creating their own cookie, Moin``Moin transactions need to authenticate the cookie.  One way to do this is to modify your other application to store a hash of the cookie value in a database, file, or other secure shared storage area that can be accessed by MoinMoin.  



== Strategy ==

The MoinMoin wiki code will be customized in two places.  ''wikiconfig.py'' will be modified to create a new External``Cookie class that will be used to authenticate a user.  Logging in to your other application will effectively log you in to the wiki.  Logging off of your other application will log you out of the wiki.  Several variables will be added to wikiconfig.py to customize the Settings:Preferences page and to automatically create new user records when required.

Your wiki themes may be modified to override the ''username'' method of the Theme class.  This method generates the ''login'' and ''logout'' hyperlinks within the wiki navigation area.  These hyperlinks will be customized to point to the login and logout pages of your other application.

You must modify your other application as outlined above to create/delete a cookie and (optionally) add/delete entries to a shared storage area.  If your wiki users can read the wiki without logging in, you may want to modify your other application login page so a wiki reader (logging in from a wiki page) will be returned to their referred-from page after login is complete (similar to the way MoinMoin login works). 

== Alternative Strategies Not Implemented ==

It is probably best to not synchronize inactivity timeouts between the other application and the wiki.  If a logged in user on the other application times out after an hour of inactivity, he can continue to edit and save pages on the wiki provided the other application timeout process is not modified to delete the entry in the shared storage area.  If the other application timed-out user logs in a again, a new entry in the shared storage area will be created and a new Moin``Auth cookie generated -- subsequent wiki transactions will use the new cookie.  The example wikiconfig.py contains an example showing how inactive entries might be removed from a My``SQL table soon after expiration by a Moin``Moin transaction.  However, most installations will probably choose to clear obsolete entries in the shared storage area with a process embedded in the other application.

One alternative to the use of a shared storage area is to encrypt the cookie in the other application and decrypt the cookie in the external_auth method.  If this method were implemented, the addition of a timestamp to the cookie value could force cookies to timeout with the addition of an aging check.  Without the aging check, any cookie generated would be valid forever (a minor issue) or until the encryption keys were changed.   Brief tests with the ezPy``Crypto example programs were discouraging because of the amount of compute time required.  My``SQL was faster -- the measured wall time to validate the cookie was usually 0 seconds and always less than 0.02 seconds.  

Another possibility to thwart the use of stolen cookies is to add the authenticated user's IP address to the cookie value and then check it against the IP address of the incoming Moin``Moin transaction.  But this has marginal value because some ISPs (AOL) change the low order bits of the IP address with each transaction and in other cases several users could appear to be coming from the same IP address.


== ExternalCookie Class ==

The first step is to override the external_auth method of the Config class by adding the code snippet below to your wikiconfig.py.



The code below is for Moin 1.7. 
  * edit your wikiconfig.py or farmconfig.py
  * find the line containing `class Config(DefaultConfig):` or `class FarmConfig(DefaultConfig):`
  * replace the above line with all of the code below
  * if using farmconfig.py find and comment/uncomment the appropriate `class` statements

{{{#!python
# +++++++++++++++ beginning of external_cookie  example

# This is some sample code you might find useful when you want to use some
# external cookie (made by some other program, not moin) with moin.
# See the +++ places for customizing it to your needs.  Copy this
# code into your farmconfig.py or wikiconfig.py by pasting it over the current:
#
#    class Config(DefaultConfig):
# OR
#    class FarmConfig(DefaultConfig):


from MoinMoin.config.multiconfig import DefaultConfig
from MoinMoin.auth import BaseAuth
    
# This is included in case you want to create a log file during testing
import time
def writeLog(*args): 
    '''Write an entry in a log file with a timestamp and all of the args.'''
    s = time.strftime('%Y-%m-%d %H:%M:%S ',time.localtime())
    for a in args:
        s = '%s %s;' % (s,a)
    log = open('/mywiki/cookie.log', 'a') # +++ location for log file
    log.write('\n' + s + '\n')
    log.close()
    return
    
# these 2 methods are examples of how to "authenticate" the other application cookie
import MySQLdb
def verifySession(sidHash): # +++ to use this, uncomment a procedure call below in ExternalCookie
    """Return True if sidHash value exists (meaning user is currently logged on), false otherwise.  
    
    If you are not a MySQL user, find another way to store this information.  ActiveSession is a two-column table
    containing a hashed cookie value (sidHash) plus a date-time stamp (tStamp).
    Your other application must add an entry to this table each time a user logs on and delete the entry when the user logs off.
    """
    db = MySQLdb.connect(db='mydb',user='myuserid',passwd='mypw') #+++ user ID needs read access
    c = db.cursor()
    q = 'select sidHash from ActiveSession where sidHash="%s"' % sidHash
    result = c.execute(q)
    c.close()
    if result == 1:
        return True
    return False
    
def verifySessionPlus(sidHash,timeout=3600*4): # +++ to use this, uncomment a procedure call below in ExternalCookie
    """Return True if sidHash value exists (meaning user is currently logged on), false otherwise.  
    
    This version of verifySession deletes entries inactive for more than 4 hours and
    updates the tStamp field with each moin transaction.  If performance is 
    important, find another way to delete inactive sessions.
    """
    db = MySQLdb.connect(db='mydb',user='myuserid',passwd='mypw') # +++ user ID needs write access
    c = db.cursor()
    q = 'delete from ActiveSession where tStamp<"%s"' % int(time.time() - timeout) # delete inactive entries
    result = c.execute(q)
    q = 'update ActiveSession set tStamp=%s where sidHash="%s"' % (int(time.time()),sidHash)
    result = c.execute(q)
    c.close()
    if result == 1:
        return True
    return False
    

class ExternalCookie(BaseAuth):
    name = 'external_cookie'
    # +++ The next 2 lines may be useful if you are overriding the username method in your themes.
    # +++  If commented out, wiki pages will not have login or logout hyperlinks
    login_inputs = ['username', 'password'] # +++ required to get a login hyperlink in wiki navigation area
    logout_possible = True # +++ required to get a logout hyperlink in wiki navigation area

    def request(self, request, user_obj, **kw):
        """Return (user-obj,False) if user is authenticated, else return (None,True). """
        # login = kw.get('login') # +++ example does not use this; login is expected in other application
        # user_obj = kw.get('user_obj')  # +++ example does not use this
        # username = kw.get('name') # +++ example does not use this
        # logout = kw.get('logout') # +++ example does not use this; logout is expected in other application
        import Cookie
        user = None  # user is not authenticated
        try_next = True  # if True, moin tries the next auth method in auth list
        
        otherAppCookie = "MoinAuth" # +++ username, email,useralias, session ID separated by #
        try:
            cookie = Cookie.SimpleCookie(request.saved_cookie)
        except Cookie.CookieError:
            cookie = None # ignore invalid cookies

        if cookie and otherAppCookie in cookie: # having this cookie means user auth has already been done in other application
            import urllib
            cookievalue = cookie[otherAppCookie].value
            # +++ decode and parse the cookie value - edit this to fit your needs.
            cookievalue = urllib.unquote(cookievalue) # cookie value is urlencoded, decode it
            cookievalue = cookievalue.decode('iso-8859-1') # decode cookie charset to unicode
            cookievalue = cookievalue.split('#') # cookie has format loginname#email#aliasname#sessionid

            email = aliasname = sessionid = ''
            try:  # extract fields from other app cookie
                auth_username = cookievalue[0] # the wiki username
                email = cookievalue[1] # email is required for user to change and save user preferences
                aliasname = cookievalue[2] # aliasname is useful only if auth_username is not wiki-like
                sessionid = cookievalue[3] # optional other app session ID  -- a unique timestamp or random number 
            except IndexError: 
                pass  # do not need aliasname or sessionid unless you uncomment lines below
            #~ writeLog('auth_username',auth_username)
            #~ writeLog('email',email)
            #~ writeLog('aliasname',aliasname)
            #~ writeLog('sessionid',sessionid)

            # +++ any hacker can create a cookie, uncomment these lines to verify the cookie was created by the other application
            # if auth_username:
                # import hashlib  # +++ python 2.5; see http://code.krypto.org/python/hashlib for 2.3, 2.4 download
                # sidHash = hashlib.md5(cookie[otherAppCookie].value).hexdigest() 
                # sidOK = verifySession(sidHash) # verify user is currently logged on to the other application +++ or use verifySessionPlus
                # if not sidOK:
                    # auth_username = None
                    
            if auth_username:
                # we have an authorized user, create the moin user object
                from MoinMoin.user import User
                # giving auth_username to User constructor means that authentication has already been done.
                user = User(request, name=auth_username, auth_username=auth_username, auth_method=self.name)
                changed = False
                if email != user.email: # was the email addr externally updated?
                    user.email = email ; 
                    changed = True # yes -> update user profile
                # if aliasname != user.aliasname: # +++ was the aliasname externally updated?
                    # user.aliasname = aliasname ; 
                    # changed = True # yes -> update user profile

                if user:
                    user.create_or_update(changed)
                if user and user.valid: 
                    try_next = False # have valid user; stop processing auth method list
        #~ writeLog(str(user), try_next)
        return user, try_next 


class Config(DefaultConfig):
#~ class FarmConfig(DefaultConfig):

    # from MoinMoin.auth import MoinAuth
    # auth = [ExternalCookie(), MoinAuth()] # try external_cookie, then normal moin login
    auth = [ExternalCookie()] # only way to login is external application
    
    # +++ these are suggested changes to the user preferences form if the  external_cookie  is the only auth method
    user_form_disable = ['name', 'aliasname', 'email',] # don't let the user change these, but show them
    user_form_remove = ['password', 'password2', 'css_url', 'logout', 'create', 'account_sendmail','jid'] # remove completely

    user_autocreate = True # +++ Moin will autocreate a new user ID if none exists

# +++++++++++++++ end of external_cookie  example,  your custom configurations continue below 
}}}

== Initial Testing ==

If you use the Firefox browser and have the Web Developer addon extension installed, initial testing will be fast and painless. Log on to your other application and click on Tools... Web Developer... Cookies... View Cookie Information.  You will probably find at least one cookie that looks like a session identifier created by your application at login, usually these will have a value with a large random number and perhaps a time stamp.

Next, click on Tools... Web Developer... Cookies... Add Cookie.  Give the cookie a name of ''Moin``Auth'' (case sensitive). Set the value to `yourname#youremail@yourprovider.com` with no spaces, and be sure to use the '''#''' character as a separator.  If your other application and the wiki run on the same host, set the host to the same value used by your other application (if not, omit the host from the domain name to share cookies across hosts).  Set the path value to "/" without the quotes.  Click the ''Session Cookie'' check box and click save.

Open a second browser window and load your starting wiki page.  The wiki should recognize you as a logged in user. Do a quick test to verify that you can edit and save a wiki page and verify that you can change your User Preferences.  

== Changing the Other Application ==
  
The example external_cookie method expects the cookie value to contain several pieces of information separated with the '''#''' character:
  * the wiki user id -- always required
  * the user's email address -- needed if the user is to be able to update and save MoinMoin User Preferences
  * user alias -- usually not required, used to override user IDs that are not wiki-like user names
  * unique session ID -- a big random number or timestamp and random number

Your application must store the Moin``Auth cookie with a path set to '/'.  Setting the path to '/' is normally not recommended because it presents a small security risk.  It allows an application to read the cookies created by a different application.  In this case, that is exactly our intent -- MoinMoin must be able to read the cookies set by the other application.

As you have already demonstrated to yourself above, any user with the skill to install the Firefox Web Developer addon could easily create a cookie and hack his way into the wiki using someone else's ID.    
To prevent this from happening, MoinMoin will need to validate the cookie value against an entry in a secure shared storage area created by the other application.   

We want to avoid creating a potential new security issue by building a cross-reference of user ID to session ID or even a list of session IDs that might be of use to a hacker.  A better way is for your application to hash (not encrypt) the Moin``Auth cookie value and store the result in a secure shared storage area.  Add a timestamp to each entry so obsolete entries can be removed later.  

There is commented out code in the example wikiconfig.py to perform a hash of the cookie contents and validate the result against a MySQL table.  In addition, there is alternative commented out code that will delete entries from the My``SQL table that are more than 4 hours old, validate the hashed cookie value against the table and update the timestamp.  A better method is to modify the other application to remove obsolete entries from the table, perhaps each time a user logs in.

As you begin to modify your application almost all of your testing can be done with the Firefox Web Developer extension.  Before you login to the other application there should be no Moin``Auth cookie, after login there should be a Moin``Auth cookie, after logout there should be no cookie. In addition, the shared storage area should be updated with a new hashed cookie value after login and cleared after logout.  Accessing a wiki page after you are logged in will cause moin to create a MOIN_SESSION cookie.



== Modifying themes ==

The next step is to modify the login and logout links in the navigation area of wiki pages.  If you limit your users to one theme, modify the code below to point to your other application's login and logoff pages.  If you allow users to choose from among several themes, it may be easiest to modify the /Moin``Moin/theme/__init__.py script directly.

If you always log on to your other application before accessing a wiki page, this modification and the one following are not required.  If you comment out the `login_inputs` and `logout_possible` variables near the top of the External``Cookie class, then your wiki pages will not contain login and logout hyperlinks.


The code below is for moin 1.7.

{{{#!python
    def username(self, d):
        """ Assemble the username / userprefs link
        
        @param d: parameter dictionary
        @rtype: unicode
        @return: username html
        """
        request = self.request
        _ = request.getText

        userlinks = []
        # Add username/homepage link for registered users. We don't care
        # if it exists, the user can create it.
        if request.user.valid and request.user.name:
            interwiki = wikiutil.getInterwikiHomePage(request)
            name = request.user.name
            aliasname = request.user.aliasname
            if not aliasname:
                aliasname = name
            title = "%s @ %s" % (aliasname, interwiki[0])
            # link to (interwiki) user homepage
            homelink = (request.formatter.interwikilink(1, title=title, id="userhome", generated=True, *interwiki) +
                        request.formatter.text(name) +
                        request.formatter.interwikilink(0, title=title, id="userhome", *interwiki))
            userlinks.append(homelink)
            # link to userprefs action
            if 'userprefs' not in self.request.cfg.actions_excluded:
                userlinks.append(d['page'].link_to(request, text=_('Settings'),
                                               querystr={'action': 'userprefs'}, id='userprefs', rel='nofollow'))

        if request.user.valid:  
            if request.user.auth_method in request.cfg.auth_can_logout:
                userlinks.append('<a href="/myapp/Logout">%s</a>' % _('Logout', formatted=False)) # +++ other app logout page
        else:
            query = {'action': 'login'}
            # special direct-login link if the auth methods want no input
            if request.cfg.auth_login_inputs == ['special_no_input']:
                query['login'] = '1'
            if request.cfg.auth_have_login:
                userlinks.append('<a  href="/myapp/Login">%s</a>' % _("Login", formatted=False)) # +++ other app login page

        userlinks = [u'<li>%s</li>' % link for link in userlinks]
        html = u'<ul id="username">%s</ul>' % ''.join(userlinks)
        return html
}}}


== Modifying the Application Login Page ==

As a final touch, you may want to consider modifying your login page for wiki users who decide to login from a wiki page.  This depends upon your choice of web servers, but most will pass something similar to an HTTP_REFERER field which will contain the prior URL.  

Check this value to determine if the referrer page was a wiki page, if so save the URL and at the end of a successful logon either redirect the current page back the referring wiki page or open a new window with the URL of the referring page.
