"""
This module defines functions to implement HTTP Digest Authentication
(:rfc:`2617`).
This has full compliance with 'Digest' and 'Basic' authentication methods. In
'Digest' it supports both MD5 and MD5-sess algorithms.
Usage:
First use 'doAuth' to request the client authentication for a
certain resource. You should send an httplib.UNAUTHORIZED response to the
client so he knows he has to authenticate itself.
Then use 'parseAuthorization' to retrieve the 'auth_map' used in
'checkResponse'.
To use 'checkResponse' you must have already verified the password
associated with the 'username' key in 'auth_map' dict. Then you use the
'checkResponse' function to verify if the password matches the one sent
by the client.
SUPPORTED_ALGORITHM - list of supported 'Digest' algorithms
SUPPORTED_QOP - list of supported 'Digest' 'qop'.
"""
import time
from hashlib import md5
from cherrypy._cpcompat import (
base64_decode, ntob,
parse_http_list, parse_keqv_list
)
__version__ = 1, 0, 1
__author__ = 'Tiago Cogumbreiro <cogumbreiro@users.sf.net>'
__credits__ = """
Peter van Kampen for its recipe which implement most of Digest
authentication:
http://aspn.activestate.com/ASPN/Cookbook/Python/Recipe/302378
"""
__license__ = """
Copyright (c) 2005, Tiago Cogumbreiro <cogumbreiro@users.sf.net>
All rights reserved.
Redistribution and use in source and binary forms, with or without
modification, are permitted provided that the following conditions are met:
* Redistributions of source code must retain the above copyright notice,
this list of conditions and the following disclaimer.
* Redistributions in binary form must reproduce the above copyright notice,
this list of conditions and the following disclaimer in the documentation
and/or other materials provided with the distribution.
* Neither the name of Sylvain Hellegouarch nor the names of his
contributors may be used to endorse or promote products derived from
this software without specific prior written permission.
THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND
ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE
FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
"""
__all__ = ('digestAuth', 'basicAuth', 'doAuth', 'checkResponse',
'parseAuthorization', 'SUPPORTED_ALGORITHM', 'md5SessionKey',
'calculateNonce', 'SUPPORTED_QOP')
##########################################################################
MD5 = 'MD5'
MD5_SESS = 'MD5-sess'
AUTH = 'auth'
AUTH_INT = 'auth-int'
SUPPORTED_ALGORITHM = (MD5, MD5_SESS)
SUPPORTED_QOP = (AUTH, AUTH_INT)
##########################################################################
# doAuth
#
DIGEST_AUTH_ENCODERS = {
MD5: lambda val: md5(ntob(val)).hexdigest(),
MD5_SESS: lambda val: md5(ntob(val)).hexdigest(),
# SHA: lambda val: sha.new(ntob(val)).hexdigest (),
}
[docs]def calculateNonce(realm, algorithm=MD5):
"""This is an auxaliary function that calculates 'nonce' value. It is used
to handle sessions."""
global SUPPORTED_ALGORITHM, DIGEST_AUTH_ENCODERS
assert algorithm in SUPPORTED_ALGORITHM
try:
encoder = DIGEST_AUTH_ENCODERS[algorithm]
except KeyError:
raise NotImplementedError('The chosen algorithm (%s) does not have '
'an implementation yet' % algorithm)
return encoder('%d:%s' % (time.time(), realm))
[docs]def digestAuth(realm, algorithm=MD5, nonce=None, qop=AUTH):
"""Challenges the client for a Digest authentication."""
global SUPPORTED_ALGORITHM, DIGEST_AUTH_ENCODERS, SUPPORTED_QOP
assert algorithm in SUPPORTED_ALGORITHM
assert qop in SUPPORTED_QOP
if nonce is None:
nonce = calculateNonce(realm, algorithm)
return 'Digest realm="%s", nonce="%s", algorithm="%s", qop="%s"' % (
realm, nonce, algorithm, qop
)
[docs]def basicAuth(realm):
"""Challengenes the client for a Basic authentication."""
assert '"' not in realm, "Realms cannot contain the \" (quote) character."
return 'Basic realm="%s"' % realm
[docs]def doAuth(realm):
"""'doAuth' function returns the challenge string b giving priority over
Digest and fallback to Basic authentication when the browser doesn't
support the first one.
This should be set in the HTTP header under the key 'WWW-Authenticate'."""
return digestAuth(realm) + ' ' + basicAuth(realm)
##########################################################################
# Parse authorization parameters
#
def _parseDigestAuthorization(auth_params):
# Convert the auth params to a dict
items = parse_http_list(auth_params)
params = parse_keqv_list(items)
# Now validate the params
# Check for required parameters
required = ['username', 'realm', 'nonce', 'uri', 'response']
for k in required:
if k not in params:
return None
# If qop is sent then cnonce and nc MUST be present
if 'qop' in params and not ('cnonce' in params
and 'nc' in params):
return None
# If qop is not sent, neither cnonce nor nc can be present
if ('cnonce' in params or 'nc' in params) and \
'qop' not in params:
return None
return params
def _parseBasicAuthorization(auth_params):
username, password = base64_decode(auth_params).split(':', 1)
return {'username': username, 'password': password}
AUTH_SCHEMES = {
'basic': _parseBasicAuthorization,
'digest': _parseDigestAuthorization,
}
[docs]def parseAuthorization(credentials):
"""parseAuthorization will convert the value of the 'Authorization' key in
the HTTP header to a map itself. If the parsing fails 'None' is returned.
"""
global AUTH_SCHEMES
auth_scheme, auth_params = credentials.split(' ', 1)
auth_scheme = auth_scheme.lower()
parser = AUTH_SCHEMES[auth_scheme]
params = parser(auth_params)
if params is None:
return
assert 'auth_scheme' not in params
params['auth_scheme'] = auth_scheme
return params
##########################################################################
# Check provided response for a valid password
#
[docs]def md5SessionKey(params, password):
"""
If the "algorithm" directive's value is "MD5-sess", then A1
[the session key] is calculated only once - on the first request by the
client following receipt of a WWW-Authenticate challenge from the server.
This creates a 'session key' for the authentication of subsequent
requests and responses which is different for each "authentication
session", thus limiting the amount of material hashed with any one
key.
Because the server need only use the hash of the user
credentials in order to create the A1 value, this construction could
be used in conjunction with a third party authentication service so
that the web server would not need the actual password value. The
specification of such a protocol is beyond the scope of this
specification.
"""
keys = ('username', 'realm', 'nonce', 'cnonce')
params_copy = {}
for key in keys:
params_copy[key] = params[key]
params_copy['algorithm'] = MD5_SESS
return _A1(params_copy, password)
def _A1(params, password):
algorithm = params.get('algorithm', MD5)
H = DIGEST_AUTH_ENCODERS[algorithm]
if algorithm == MD5:
# If the "algorithm" directive's value is "MD5" or is
# unspecified, then A1 is:
# A1 = unq(username-value) ":" unq(realm-value) ":" passwd
return '%s:%s:%s' % (params['username'], params['realm'], password)
elif algorithm == MD5_SESS:
# This is A1 if qop is set
# A1 = H( unq(username-value) ":" unq(realm-value) ":" passwd )
# ":" unq(nonce-value) ":" unq(cnonce-value)
h_a1 = H('%s:%s:%s' % (params['username'], params['realm'], password))
return '%s:%s:%s' % (h_a1, params['nonce'], params['cnonce'])
def _A2(params, method, kwargs):
# If the "qop" directive's value is "auth" or is unspecified, then A2 is:
# A2 = Method ":" digest-uri-value
qop = params.get('qop', 'auth')
if qop == 'auth':
return method + ':' + params['uri']
elif qop == 'auth-int':
# If the "qop" value is "auth-int", then A2 is:
# A2 = Method ":" digest-uri-value ":" H(entity-body)
entity_body = kwargs.get('entity_body', '')
H = kwargs['H']
return '%s:%s:%s' % (
method,
params['uri'],
H(entity_body)
)
else:
raise NotImplementedError("The 'qop' method is unknown: %s" % qop)
def _computeDigestResponse(auth_map, password, method='GET', A1=None,
**kwargs):
"""
Generates a response respecting the algorithm defined in RFC 2617
"""
params = auth_map
algorithm = params.get('algorithm', MD5)
H = DIGEST_AUTH_ENCODERS[algorithm]
KD = lambda secret, data: H(secret + ':' + data)
qop = params.get('qop', None)
H_A2 = H(_A2(params, method, kwargs))
if algorithm == MD5_SESS and A1 is not None:
H_A1 = H(A1)
else:
H_A1 = H(_A1(params, password))
if qop in ('auth', 'auth-int'):
# If the "qop" value is "auth" or "auth-int":
# request-digest = <"> < KD ( H(A1), unq(nonce-value)
# ":" nc-value
# ":" unq(cnonce-value)
# ":" unq(qop-value)
# ":" H(A2)
# ) <">
request = '%s:%s:%s:%s:%s' % (
params['nonce'],
params['nc'],
params['cnonce'],
params['qop'],
H_A2,
)
elif qop is None:
# If the "qop" directive is not present (this construction is
# for compatibility with RFC 2069):
# request-digest =
# <"> < KD ( H(A1), unq(nonce-value) ":" H(A2) ) > <">
request = '%s:%s' % (params['nonce'], H_A2)
return KD(H_A1, request)
def _checkDigestResponse(auth_map, password, method='GET', A1=None, **kwargs):
"""This function is used to verify the response given by the client when
he tries to authenticate.
Optional arguments:
entity_body - when 'qop' is set to 'auth-int' you MUST provide the
raw data you are going to send to the client (usually the
HTML page.
request_uri - the uri from the request line compared with the 'uri'
directive of the authorization map. They must represent
the same resource (unused at this time).
"""
if auth_map['realm'] != kwargs.get('realm', None):
return False
response = _computeDigestResponse(
auth_map, password, method, A1, **kwargs)
return response == auth_map['response']
def _checkBasicResponse(auth_map, password, method='GET', encrypt=None,
**kwargs):
# Note that the Basic response doesn't provide the realm value so we cannot
# test it
pass_through = lambda password, username=None: password
encrypt = encrypt or pass_through
try:
candidate = encrypt(auth_map['password'], auth_map['username'])
except TypeError:
# if encrypt only takes one parameter, it's the password
candidate = encrypt(auth_map['password'])
return candidate == password
AUTH_RESPONSES = {
'basic': _checkBasicResponse,
'digest': _checkDigestResponse,
}
[docs]def checkResponse(auth_map, password, method='GET', encrypt=None, **kwargs):
"""'checkResponse' compares the auth_map with the password and optionally
other arguments that each implementation might need.
If the response is of type 'Basic' then the function has the following
signature::
checkBasicResponse(auth_map, password) -> bool
If the response is of type 'Digest' then the function has the following
signature::
checkDigestResponse(auth_map, password, method='GET', A1=None) -> bool
The 'A1' argument is only used in MD5_SESS algorithm based responses.
Check md5SessionKey() for more info.
"""
checker = AUTH_RESPONSES[auth_map['auth_scheme']]
return checker(auth_map, password, method=method, encrypt=encrypt,
**kwargs)