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third_party/cherrypy/lib/auth_digest.py

Index: third_party/cherrypy/lib/auth_digest.py
===================================================================
--- third_party/cherrypy/lib/auth_digest.py	(revision 0)
+++ third_party/cherrypy/lib/auth_digest.py	(revision 0)
@@ -0,0 +1,365 @@
+# This file is part of CherryPy <http://www.cherrypy.org/>
+# -*- coding: utf-8 -*-
+# vim:ts=4:sw=4:expandtab:fileencoding=utf-8
+
+__doc__ = """An implementation of the server-side of HTTP Digest Access
+Authentication, which is described in :rfc:`2617`.
+
+Example usage, using the built-in get_ha1_dict_plain function which uses a dict
+of plaintext passwords as the credentials store::
+
+    userpassdict = {'alice' : '4x5istwelve'}
+    get_ha1 = cherrypy.lib.auth_digest.get_ha1_dict_plain(userpassdict)
+    digest_auth = {'tools.auth_digest.on': True,
+                   'tools.auth_digest.realm': 'wonderland',
+                   'tools.auth_digest.get_ha1': get_ha1,
+                   'tools.auth_digest.key': 'a565c27146791cfb',
+    }
+    app_config = { '/' : digest_auth }
+"""
+
+__author__ = 'visteya'
+__date__ = 'April 2009'
+
+
+import time
+from cherrypy._cpcompat import parse_http_list, parse_keqv_list
+
+import cherrypy
+from cherrypy._cpcompat import md5, ntob
+md5_hex = lambda s: md5(ntob(s)).hexdigest()
+
+qop_auth = 'auth'
+qop_auth_int = 'auth-int'
+valid_qops = (qop_auth, qop_auth_int)
+
+valid_algorithms = ('MD5', 'MD5-sess')
+
+
+def TRACE(msg):
+    cherrypy.log(msg, context='TOOLS.AUTH_DIGEST')
+
+# Three helper functions for users of the tool, providing three variants
+# of get_ha1() functions for three different kinds of credential stores.
+def get_ha1_dict_plain(user_password_dict):
+    """Returns a get_ha1 function which obtains a plaintext password from a
+    dictionary of the form: {username : password}.
+
+    If you want a simple dictionary-based authentication scheme, with plaintext
+    passwords, use get_ha1_dict_plain(my_userpass_dict) as the value for the
+    get_ha1 argument to digest_auth().
+    """
+    def get_ha1(realm, username):
+        password = user_password_dict.get(username)
+        if password:
+            return md5_hex('%s:%s:%s' % (username, realm, password))
+        return None
+
+    return get_ha1
+
+def get_ha1_dict(user_ha1_dict):
+    """Returns a get_ha1 function which obtains a HA1 password hash from a
+    dictionary of the form: {username : HA1}.
+
+    If you want a dictionary-based authentication scheme, but with
+    pre-computed HA1 hashes instead of plain-text passwords, use
+    get_ha1_dict(my_userha1_dict) as the value for the get_ha1
+    argument to digest_auth().
+    """
+    def get_ha1(realm, username):
+        return user_ha1_dict.get(user)
+
+    return get_ha1
+
+def get_ha1_file_htdigest(filename):
+    """Returns a get_ha1 function which obtains a HA1 password hash from a
+    flat file with lines of the same format as that produced by the Apache
+    htdigest utility. For example, for realm 'wonderland', username 'alice',
+    and password '4x5istwelve', the htdigest line would be::
+
+        alice:wonderland:3238cdfe91a8b2ed8e39646921a02d4c
+
+    If you want to use an Apache htdigest file as the credentials store,
+    then use get_ha1_file_htdigest(my_htdigest_file) as the value for the
+    get_ha1 argument to digest_auth().  It is recommended that the filename
+    argument be an absolute path, to avoid problems.
+    """
+    def get_ha1(realm, username):
+        result = None
+        f = open(filename, 'r')
+        for line in f:
+            u, r, ha1 = line.rstrip().split(':')
+            if u == username and r == realm:
+                result = ha1
+                break
+        f.close()
+        return result
+
+    return get_ha1
+
+
+def synthesize_nonce(s, key, timestamp=None):
+    """Synthesize a nonce value which resists spoofing and can be checked for staleness.
+    Returns a string suitable as the value for 'nonce' in the www-authenticate header.
+
+    s
+        A string related to the resource, such as the hostname of the server.
+
+    key
+        A secret string known only to the server.
+    
+    timestamp
+        An integer seconds-since-the-epoch timestamp
+    
+    """
+    if timestamp is None:
+        timestamp = int(time.time())
+    h = md5_hex('%s:%s:%s' % (timestamp, s, key))
+    nonce = '%s:%s' % (timestamp, h)
+    return nonce
+
+
+def H(s):
+    """The hash function H"""
+    return md5_hex(s)
+
+
+class HttpDigestAuthorization (object):
+    """Class to parse a Digest Authorization header and perform re-calculation
+    of the digest.
+    """
+
+    def errmsg(self, s):
+        return 'Digest Authorization header: %s' % s
+
+    def __init__(self, auth_header, http_method, debug=False):
+        self.http_method = http_method
+        self.debug = debug
+        scheme, params  = auth_header.split(" ", 1)
+        self.scheme = scheme.lower()
+        if self.scheme != 'digest':
+            raise ValueError('Authorization scheme is not "Digest"')
+
+        self.auth_header = auth_header
+
+        # make a dict of the params
+        items = parse_http_list(params)
+        paramsd = parse_keqv_list(items)
+
+        self.realm = paramsd.get('realm')
+        self.username = paramsd.get('username')
+        self.nonce = paramsd.get('nonce')
+        self.uri = paramsd.get('uri')
+        self.method = paramsd.get('method')
+        self.response = paramsd.get('response') # the response digest
+        self.algorithm = paramsd.get('algorithm', 'MD5')
+        self.cnonce = paramsd.get('cnonce')
+        self.opaque = paramsd.get('opaque')
+        self.qop = paramsd.get('qop') # qop
+        self.nc = paramsd.get('nc') # nonce count
+
+        # perform some correctness checks
+        if self.algorithm not in valid_algorithms:
+            raise ValueError(self.errmsg("Unsupported value for algorithm: '%s'" % self.algorithm))
+
+        has_reqd = self.username and \
+                   self.realm and \
+                   self.nonce and \
+                   self.uri and \
+                   self.response
+        if not has_reqd:
+            raise ValueError(self.errmsg("Not all required parameters are present."))
+
+        if self.qop:
+            if self.qop not in valid_qops:
+                raise ValueError(self.errmsg("Unsupported value for qop: '%s'" % self.qop))
+            if not (self.cnonce and self.nc):
+                raise ValueError(self.errmsg("If qop is sent then cnonce and nc MUST be present"))
+        else:
+            if self.cnonce or self.nc:
+                raise ValueError(self.errmsg("If qop is not sent, neither cnonce nor nc can be present"))
+
+
+    def __str__(self):
+        return 'authorization : %s' % self.auth_header
+
+    def validate_nonce(self, s, key):
+        """Validate the nonce.
+        Returns True if nonce was generated by synthesize_nonce() and the timestamp
+        is not spoofed, else returns False.
+
+        s
+            A string related to the resource, such as the hostname of the server.
+            
+        key
+            A secret string known only to the server.
+        
+        Both s and key must be the same values which were used to synthesize the nonce
+        we are trying to validate.
+        """
+        try:
+            timestamp, hashpart = self.nonce.split(':', 1)
+            s_timestamp, s_hashpart = synthesize_nonce(s, key, timestamp).split(':', 1)
+            is_valid = s_hashpart == hashpart
+            if self.debug:
+                TRACE('validate_nonce: %s' % is_valid)
+            return is_valid
+        except ValueError: # split() error
+            pass
+        return False
+
+
+    def is_nonce_stale(self, max_age_seconds=600):
+        """Returns True if a validated nonce is stale. The nonce contains a
+        timestamp in plaintext and also a secure hash of the timestamp. You should
+        first validate the nonce to ensure the plaintext timestamp is not spoofed.
+        """
+        try:
+            timestamp, hashpart = self.nonce.split(':', 1)
+            if int(timestamp) + max_age_seconds > int(time.time()):
+                return False
+        except ValueError: # int() error
+            pass
+        if self.debug:
+            TRACE("nonce is stale")
+        return True
+
+
+    def HA2(self, entity_body=''):
+        """Returns the H(A2) string. See :rfc:`2617` section 3.2.2.3."""
+        # RFC 2617 3.2.2.3
+        # If the "qop" directive's value is "auth" or is unspecified, then A2 is:
+        #    A2 = method ":" digest-uri-value
+        #
+        # If the "qop" value is "auth-int", then A2 is:
+        #    A2 = method ":" digest-uri-value ":" H(entity-body)
+        if self.qop is None or self.qop == "auth":
+            a2 = '%s:%s' % (self.http_method, self.uri)
+        elif self.qop == "auth-int":
+            a2 = "%s:%s:%s" % (self.http_method, self.uri, H(entity_body))
+        else:
+            # in theory, this should never happen, since I validate qop in __init__()
+            raise ValueError(self.errmsg("Unrecognized value for qop!"))
+        return H(a2)
+
+
+    def request_digest(self, ha1, entity_body=''):
+        """Calculates the Request-Digest. See :rfc:`2617` section 3.2.2.1.
+
+        ha1
+            The HA1 string obtained from the credentials store.
+
+        entity_body
+            If 'qop' is set to 'auth-int', then A2 includes a hash
+            of the "entity body".  The entity body is the part of the
+            message which follows the HTTP headers. See :rfc:`2617` section
+            4.3.  This refers to the entity the user agent sent in the request which
+            has the Authorization header. Typically GET requests don't have an entity,
+            and POST requests do.
+        
+        """
+        ha2 = self.HA2(entity_body)
+        # Request-Digest -- RFC 2617 3.2.2.1
+        if self.qop:
+            req = "%s:%s:%s:%s:%s" % (self.nonce, self.nc, self.cnonce, self.qop, ha2)
+        else:
+            req = "%s:%s" % (self.nonce, ha2)
+
+        # RFC 2617 3.2.2.2
+        #
+        # If the "algorithm" directive's value is "MD5" or is unspecified, then A1 is:
+        # A1 = unq(username-value) ":" unq(realm-value) ":" passwd
+        #
+        # If the "algorithm" directive's value is "MD5-sess", then A1 is
+        # calculated only once - on the first request by the client following
+        # receipt of a WWW-Authenticate challenge from the server.
+        # A1 = H( unq(username-value) ":" unq(realm-value) ":" passwd )
+        #         ":" unq(nonce-value) ":" unq(cnonce-value)
+        if self.algorithm == 'MD5-sess':
+            ha1 = H('%s:%s:%s' % (ha1, self.nonce, self.cnonce))
+
+        digest = H('%s:%s' % (ha1, req))
+        return digest
+
+
+
+def www_authenticate(realm, key, algorithm='MD5', nonce=None, qop=qop_auth, stale=False):
+    """Constructs a WWW-Authenticate header for Digest authentication."""
+    if qop not in valid_qops:
+        raise ValueError("Unsupported value for qop: '%s'" % qop)
+    if algorithm not in valid_algorithms:
+        raise ValueError("Unsupported value for algorithm: '%s'" % algorithm)
+
+    if nonce is None:
+        nonce = synthesize_nonce(realm, key)
+    s = 'Digest realm="%s", nonce="%s", algorithm="%s", qop="%s"' % (
+                realm, nonce, algorithm, qop)
+    if stale:
+        s += ', stale="true"'
+    return s
+
+
+def digest_auth(realm, get_ha1, key, debug=False):
+    """A CherryPy tool which hooks at before_handler to perform
+    HTTP Digest Access Authentication, as specified in :rfc:`2617`.
+    
+    If the request has an 'authorization' header with a 'Digest' scheme, this
+    tool authenticates the credentials supplied in that header.  If
+    the request has no 'authorization' header, or if it does but the scheme is
+    not "Digest", or if authentication fails, the tool sends a 401 response with
+    a 'WWW-Authenticate' Digest header.
+    
+    realm
+        A string containing the authentication realm.
+    
+    get_ha1
+        A callable which looks up a username in a credentials store
+        and returns the HA1 string, which is defined in the RFC to be
+        MD5(username : realm : password).  The function's signature is:
+        ``get_ha1(realm, username)``
+        where username is obtained from the request's 'authorization' header.
+        If username is not found in the credentials store, get_ha1() returns
+        None.
+    
+    key
+        A secret string known only to the server, used in the synthesis of nonces.
+    
+    """
+    request = cherrypy.serving.request
+    
+    auth_header = request.headers.get('authorization')
+    nonce_is_stale = False
+    if auth_header is not None:
+        try:
+            auth = HttpDigestAuthorization(auth_header, request.method, debug=debug)
+        except ValueError:
+            raise cherrypy.HTTPError(400, "The Authorization header could not be parsed.")
+        
+        if debug:
+            TRACE(str(auth))
+        
+        if auth.validate_nonce(realm, key):
+            ha1 = get_ha1(realm, auth.username)
+            if ha1 is not None:
+                # note that for request.body to be available we need to hook in at
+                # before_handler, not on_start_resource like 3.1.x digest_auth does.
+                digest = auth.request_digest(ha1, entity_body=request.body)
+                if digest == auth.response: # authenticated
+                    if debug:
+                        TRACE("digest matches auth.response")
+                    # Now check if nonce is stale.
+                    # The choice of ten minutes' lifetime for nonce is somewhat arbitrary
+                    nonce_is_stale = auth.is_nonce_stale(max_age_seconds=600)
+                    if not nonce_is_stale:
+                        request.login = auth.username
+                        if debug:
+                            TRACE("authentication of %s successful" % auth.username)
+                        return
+    
+    # Respond with 401 status and a WWW-Authenticate header
+    header = www_authenticate(realm, key, stale=nonce_is_stale)
+    if debug:
+        TRACE(header)
+    cherrypy.serving.response.headers['WWW-Authenticate'] = header
+    raise cherrypy.HTTPError(401, "You are not authorized to access that resource")
+
Property changes on: third_party/cherrypy/lib/auth_digest.py
___________________________________________________________________
Added: svn:eol-style
   + LF