# -*- test-case-name: twisted.test.test_newcred-*- # Copyright (c) Twisted Matrix Laboratories. # See LICENSE for details. """ This module defines L{ICredentials}, an interface for objects that represent authentication credentials to provide, and also includes a number of useful implementations of that interface. """ from zope.interface import implements, Interface import hmac, time, random, re from hashlib import md5 from twisted.python.randbytes import secureRandom from twisted.cred._digest import calcResponse, calcHA1, calcHA2 from twisted.cred import error class ICredentials(Interface): """ I check credentials. Implementors _must_ specify which sub-interfaces of ICredentials to which it conforms, using zope.interface.implements(). """ class IUsernameDigestHash(ICredentials): """ This credential is used when a CredentialChecker has access to the hash of the username:realm:password as in an Apache .htdigest file. """ def checkHash(digestHash): """ @param digestHash: The hashed username:realm:password to check against. @return: C{True} if the credentials represented by this object match the given hash, C{False} if they do not, or a L{Deferred} which will be called back with one of these values. """ class IUsernameHashedPassword(ICredentials): """ I encapsulate a username and a hashed password. This credential is used when a hashed password is received from the party requesting authentication. CredentialCheckers which check this kind of credential must store the passwords in plaintext (or as password-equivalent hashes) form so that they can be hashed in a manner appropriate for the particular credentials class. @type username: C{str} @ivar username: The username associated with these credentials. """ def checkPassword(password): """ Validate these credentials against the correct password. @type password: C{str} @param password: The correct, plaintext password against which to check. @rtype: C{bool} or L{Deferred} @return: C{True} if the credentials represented by this object match the given password, C{False} if they do not, or a L{Deferred} which will be called back with one of these values. """ class IUsernamePassword(ICredentials): """ I encapsulate a username and a plaintext password. This encapsulates the case where the password received over the network has been hashed with the identity function (That is, not at all). The CredentialsChecker may store the password in whatever format it desires, it need only transform the stored password in a similar way before performing the comparison. @type username: C{str} @ivar username: The username associated with these credentials. @type password: C{str} @ivar password: The password associated with these credentials. """ def checkPassword(password): """ Validate these credentials against the correct password. @type password: C{str} @param password: The correct, plaintext password against which to check. @rtype: C{bool} or L{Deferred} @return: C{True} if the credentials represented by this object match the given password, C{False} if they do not, or a L{Deferred} which will be called back with one of these values. """ class IAnonymous(ICredentials): """ I am an explicitly anonymous request for access. """ class DigestedCredentials(object): """ Yet Another Simple HTTP Digest authentication scheme. """ implements(IUsernameHashedPassword, IUsernameDigestHash) def __init__(self, username, method, realm, fields): self.username = username self.method = method self.realm = realm self.fields = fields def checkPassword(self, password): """ Verify that the credentials represented by this object agree with the given plaintext C{password} by hashing C{password} in the same way the response hash represented by this object was generated and comparing the results. """ response = self.fields.get('response') uri = self.fields.get('uri') nonce = self.fields.get('nonce') cnonce = self.fields.get('cnonce') nc = self.fields.get('nc') algo = self.fields.get('algorithm', 'md5').lower() qop = self.fields.get('qop', 'auth') expected = calcResponse( calcHA1(algo, self.username, self.realm, password, nonce, cnonce), calcHA2(algo, self.method, uri, qop, None), algo, nonce, nc, cnonce, qop) return expected == response def checkHash(self, digestHash): """ Verify that the credentials represented by this object agree with the credentials represented by the I{H(A1)} given in C{digestHash}. @param digestHash: A precomputed H(A1) value based on the username, realm, and password associate with this credentials object. """ response = self.fields.get('response') uri = self.fields.get('uri') nonce = self.fields.get('nonce') cnonce = self.fields.get('cnonce') nc = self.fields.get('nc') algo = self.fields.get('algorithm', 'md5').lower() qop = self.fields.get('qop', 'auth') expected = calcResponse( calcHA1(algo, None, None, None, nonce, cnonce, preHA1=digestHash), calcHA2(algo, self.method, uri, qop, None), algo, nonce, nc, cnonce, qop) return expected == response class DigestCredentialFactory(object): """ Support for RFC2617 HTTP Digest Authentication @cvar CHALLENGE_LIFETIME_SECS: The number of seconds for which an opaque should be valid. @type privateKey: C{str} @ivar privateKey: A random string used for generating the secure opaque. @type algorithm: C{str} @param algorithm: Case insensitive string specifying the hash algorithm to use. Must be either C{'md5'} or C{'sha'}. C{'md5-sess'} is B{not} supported. @type authenticationRealm: C{str} @param authenticationRealm: case sensitive string that specifies the realm portion of the challenge """ _parseparts = re.compile( b'([^= ]+)' # The key b'=' # Conventional key/value separator (literal) b'(?:' # Group together a couple options b'"([^"]*)"' # A quoted string of length 0 or more b'|' # The other option in the group is coming b'([^,]+)' # An unquoted string of length 1 or more, up to a comma b')' # That non-matching group ends b',?') # There might be a comma at the end (none on last pair) CHALLENGE_LIFETIME_SECS = 15 * 60 # 15 minutes scheme = "digest" def __init__(self, algorithm, authenticationRealm): self.algorithm = algorithm self.authenticationRealm = authenticationRealm self.privateKey = secureRandom(12) def getChallenge(self, address): """ Generate the challenge for use in the WWW-Authenticate header. @param address: The client address to which this challenge is being sent. @return: The C{dict} that can be used to generate a WWW-Authenticate header. """ c = self._generateNonce() o = self._generateOpaque(c, address) return {'nonce': c, 'opaque': o, 'qop': 'auth', 'algorithm': self.algorithm, 'realm': self.authenticationRealm} def _generateNonce(self): """ Create a random value suitable for use as the nonce parameter of a WWW-Authenticate challenge. @rtype: C{str} """ return secureRandom(12).encode('hex') def _getTime(self): """ Parameterize the time based seed used in C{_generateOpaque} so we can deterministically unittest it's behavior. """ return time.time() def _generateOpaque(self, nonce, clientip): """ Generate an opaque to be returned to the client. This is a unique string that can be returned to us and verified. """ # Now, what we do is encode the nonce, client ip and a timestamp in the # opaque value with a suitable digest. now = str(int(self._getTime())) if clientip is None: clientip = '' key = "%s,%s,%s" % (nonce, clientip, now) digest = md5(key + self.privateKey).hexdigest() ekey = key.encode('base64') return "%s-%s" % (digest, ekey.replace('\n', '')) def _verifyOpaque(self, opaque, nonce, clientip): """ Given the opaque and nonce from the request, as well as the client IP that made the request, verify that the opaque was generated by us. And that it's not too old. @param opaque: The opaque value from the Digest response @param nonce: The nonce value from the Digest response @param clientip: The remote IP address of the client making the request or C{None} if the request was submitted over a channel where this does not make sense. @return: C{True} if the opaque was successfully verified. @raise error.LoginFailed: if C{opaque} could not be parsed or contained the wrong values. """ # First split the digest from the key opaqueParts = opaque.split('-') if len(opaqueParts) != 2: raise error.LoginFailed('Invalid response, invalid opaque value') if clientip is None: clientip = '' # Verify the key key = opaqueParts[1].decode('base64') keyParts = key.split(',') if len(keyParts) != 3: raise error.LoginFailed('Invalid response, invalid opaque value') if keyParts[0] != nonce: raise error.LoginFailed( 'Invalid response, incompatible opaque/nonce values') if keyParts[1] != clientip: raise error.LoginFailed( 'Invalid response, incompatible opaque/client values') try: when = int(keyParts[2]) except ValueError: raise error.LoginFailed( 'Invalid response, invalid opaque/time values') if (int(self._getTime()) - when > DigestCredentialFactory.CHALLENGE_LIFETIME_SECS): raise error.LoginFailed( 'Invalid response, incompatible opaque/nonce too old') # Verify the digest digest = md5(key + self.privateKey).hexdigest() if digest != opaqueParts[0]: raise error.LoginFailed('Invalid response, invalid opaque value') return True def decode(self, response, method, host): """ Decode the given response and attempt to generate a L{DigestedCredentials} from it. @type response: C{str} @param response: A string of comma seperated key=value pairs @type method: C{str} @param method: The action requested to which this response is addressed (GET, POST, INVITE, OPTIONS, etc). @type host: C{str} @param host: The address the request was sent from. @raise error.LoginFailed: If the response does not contain a username, a nonce, an opaque, or if the opaque is invalid. @return: L{DigestedCredentials} """ response = ' '.join(response.splitlines()) parts = self._parseparts.findall(response) auth = {} for (key, bare, quoted) in parts: value = (quoted or bare).strip() auth[key.strip()] = value username = auth.get('username') if not username: raise error.LoginFailed('Invalid response, no username given.') if 'opaque' not in auth: raise error.LoginFailed('Invalid response, no opaque given.') if 'nonce' not in auth: raise error.LoginFailed('Invalid response, no nonce given.') # Now verify the nonce/opaque values for this client if self._verifyOpaque(auth.get('opaque'), auth.get('nonce'), host): return DigestedCredentials(username, method, self.authenticationRealm, auth) class CramMD5Credentials: implements(IUsernameHashedPassword) challenge = '' response = '' def __init__(self, host=None): self.host = host def getChallenge(self): if self.challenge: return self.challenge # The data encoded in the first ready response contains an # presumptively arbitrary string of random digits, a timestamp, and # the fully-qualified primary host name of the server. The syntax of # the unencoded form must correspond to that of an RFC 822 'msg-id' # [RFC822] as described in [POP3]. # -- RFC 2195 r = random.randrange(0x7fffffff) t = time.time() self.challenge = '<%d.%d@%s>' % (r, t, self.host) return self.challenge def setResponse(self, response): self.username, self.response = response.split(None, 1) def moreChallenges(self): return False def checkPassword(self, password): verify = hmac.HMAC(password, self.challenge).hexdigest() return verify == self.response class UsernameHashedPassword: implements(IUsernameHashedPassword) def __init__(self, username, hashed): self.username = username self.hashed = hashed def checkPassword(self, password): return self.hashed == password class UsernamePassword: implements(IUsernamePassword) def __init__(self, username, password): self.username = username self.password = password def checkPassword(self, password): return self.password == password class Anonymous: implements(IAnonymous) class ISSHPrivateKey(ICredentials): """ L{ISSHPrivateKey} credentials encapsulate an SSH public key to be checked against a user's private key. @ivar username: The username associated with these credentials. @type username: C{str} @ivar algName: The algorithm name for the blob. @type algName: C{str} @ivar blob: The public key blob as sent by the client. @type blob: C{str} @ivar sigData: The data the signature was made from. @type sigData: C{str} @ivar signature: The signed data. This is checked to verify that the user owns the private key. @type signature: C{str} or C{NoneType} """ class SSHPrivateKey: implements(ISSHPrivateKey) def __init__(self, username, algName, blob, sigData, signature): self.username = username self.algName = algName self.blob = blob self.sigData = sigData self.signature = signature class IPluggableAuthenticationModules(ICredentials): """I encapsulate the authentication of a user via PAM (Pluggable Authentication Modules. I use PyPAM (available from http://www.tummy.com/Software/PyPam/index.html). @ivar username: The username for the user being logged in. @ivar pamConversion: A function that is called with a list of tuples (message, messageType). See the PAM documentation for the meaning of messageType. The function returns a Deferred which will fire with a list of (response, 0), one for each message. The 0 is currently unused, but is required by the PAM library. """ class PluggableAuthenticationModules: implements(IPluggableAuthenticationModules) def __init__(self, username, pamConversion): self.username = username self.pamConversion = pamConversion