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Python Cookbook by David Ascher, Alex Martelli

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Finding an Internet Explorer Cookie

Credit: Andy McKay

Problem

You need to find a specific IE cookie.

Solution

Cookies that your browser has downloaded contain potentially useful information, so it’s important to know how to get at them. With IE, you need to access the registry to find where the cookies are, then read them as files:

from string import lower, find
import re, os, glob
import win32api, win32con

def _getLocation(  ):
    """ Examines the registry to find the cookie folder IE uses """
    key = r'Software\Microsoft\Windows\CurrentVersion\Explorer\Shell Folders'
    regkey = win32api.RegOpenKey(win32con.HKEY_CURRENT_USER, key, 0,
        win32con.KEY_ALL_ACCESS)
    num = win32api.RegQueryInfoKey(regkey)[1]
    for x in range(num):
        k = win32api.RegEnumValue(regkey, x)
        if k[0] == 'Cookies':
            return k[1]

def _getCookieFiles(location, name):
    """ Rummages through all the filenames in the cookie folder and returns
    only the filenames that include the substring 'name'. name can be the domain; 
    for example 'activestate' will return all cookies for activestate.
    Unfortunately, it will also return cookies for domains such as
    activestate.foo.com, but that's unlikely to happen, and you can
    double-check later to see if it has occurred. """
    filemask = os.path.join(location, '*%s*' % name)
    filenames = glob.glob(filemask)
    return filenames

def _findCookie(files, cookie_re):
    """ Look through a group of files for a cookie that satisfies a
    given compiled RE, returning the first such cookie found. """
    for file in files:
        data = open(file, 'r').read(  )
        m = cookie_re.search(data)
        if m: return m.group(1)

def findIECookie(domain, cookie):
    """ Finds the cookie for a given domain from IE cookie files """
    try:
        l = _getLocation(  )
    except:
        # Print a debug message
        print "Error pulling registry key"
        return None

    # Found the key; now find the files and look through them
    f = _getCookieFiles(l, domain)
    if f:
        cookie_re = re.compile('%s\n(.*?)\n' % cookie)
        return _findCookie(f, cookie_re)
    else:
        print "No cookies for domain (%s) found" % domain
        return None


if _ _name_ _=='_ _main_ _':
    print findIECookie(domain='kuro5hin', cookie='k5-new_session')

Discussion

While Netscape cookies are in a text file, which you can access as shown in Recipe 11.9, IE keeps cookies as files in a directory, and you need to access the registry to find which directory that is. This recipe uses the win32all Windows-specific extensions to Python for registry access; as an alternative, the _winreg module that is part of Python’s standard distribution for Windows can be used. The code has been tested and works on IE 5 and 6.

In the recipe, the _getLocation function accesses the registry and finds and returns the directory IE is using for cookies files. The _getCookieFiles function receives the directory as an argument and uses standard module glob to return all filenames in the directory whose names include a particular requested domain name. The _findCookie function opens and reads all such files in turn, until it finds one that satisfies a compiled regular expression which the function receives as an argument. It then returns the substring of the file’s contents corresponding to the first parenthesized group in the RE, or None if no satisfactory file is found. As the leading underscore in each of these functions’ names indicates, these are all internal functions, meant only as implementation details of the only function this module is meant to expose, namely findIECookie, which appropriately uses the other functions to locate and return a specific cookie’s value for a given domain.

An alternative to this recipe could be to write a Python extension, or use calldll, to access the InternetGetCookie API function in Wininet.DLL, as documented on MSDN. However, the added value of the alternative seems to be not worth the effort of dropping down from a pure Python module to a C-coded extension.

See Also

Recipe 11.9; the Unofficial Cookie FAQ (http://www.cookiecentral.com/faq/) is chock-full of information on cookies; Documentation for win32api and win32con in win32all (http://starship.python.net/crew/mhammond/win32/Downloads.html) or ActivePython (http://www.activestate.com/ActivePython/); Windows API documentation available from Microsoft (http://msdn.microsoft.com); Python Programming on Win32, by Mark Hammond and Andy Robinson (O’Reilly); calldll is available at Sam Rushing’s page (http://www.nightmare.com/~rushing/dynwin/).

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