[Dave Cridland] basic SCRAM-SHA-1 implementation (no channel binding). Fixes #5622

src/common/xmpp/auth_nb.py

@@ -29,6 +29,8 @@ import random
 import itertools
 import dispatcher_nb
 import hashlib
+import hmac
+import hashlib
 
 import logging
 log = logging.getLogger('gajim.c.x.auth_nb')
@@ -113,6 +115,11 @@ def challenge_splitter(data):
             quotes_open = False
     return dict_
 
+def scram_parse(chatter):
+    stuff = {}
+    for k, v in [s.split('=', 1) for s in chatter.split(',')]:
+        stuff[k] = v
+    return stuff
 
 class SASL(PlugIn):
     """
@@ -231,6 +238,13 @@ class SASL(PlugIn):
                 raise NodeProcessed
             except kerberos.GSSError, e:
                 log.info('GSSAPI authentication failed: %s' % str(e))
+        if 'SCRAM-SHA-1' in self.mecs:
+            self.mecs.remove('SCRAM-SHA-1')
+            self.mechanism = 'SCRAM-SHA-1'
+            self._owner._caller.get_password(self.set_password)
+            self.scram_step = 0
+            self.startsasl = SASL_IN_PROCESS
+            raise NodeProcessed
         if 'DIGEST-MD5' in self.mecs:
             self.mecs.remove('DIGEST-MD5')
             node = Node('auth', attrs={'xmlns': NS_SASL, 'mechanism': 'DIGEST-MD5'})
@@ -245,8 +259,8 @@ class SASL(PlugIn):
             self.startsasl = SASL_IN_PROCESS
             raise NodeProcessed
         self.startsasl = SASL_FAILURE
-        log.info('I can only use EXTERNAL, DIGEST-MD5, GSSAPI and PLAIN '
-                'mecanisms.')
+        log.info('I can only use EXTERNAL, SCRAM-SHA-1, DIGEST-MD5, GSSAPI and '
+            'PLAIN mecanisms.')
         if self.on_sasl:
             self.on_sasl()
         return
@@ -273,6 +287,8 @@ class SASL(PlugIn):
                 self.on_sasl()
             raise NodeProcessed
         elif challenge.getName() == 'success':
+            # TODO: Need to validate any data-with-success.
+            # TODO: Important for DIGEST-MD5 and SCRAM.
             self.startsasl = SASL_SUCCESS
             log.info('Successfully authenticated with remote server.')
             handlers = self._owner.Dispatcher.dumpHandlers()
@@ -310,9 +326,69 @@ class SASL(PlugIn):
             response = kerberos.authGSSClientResponse(self.gss_vc)
             if not response:
                 response = ''
-            self._owner.send(Node('response', attrs={'xmlns':NS_SASL},
+            self._owner.send(Node('response', attrs={'xmlns': NS_SASL},
                     payload=response).__str__())
             raise NodeProcessed
+        if self.mechanism == 'SCRAM-SHA-1':
+            hashfn = hashlib.sha1
+            def HMAC(k, s):
+                return hmac.HMAC(key=k, msg=s, digestmod=hashfn).digest()
+            def XOR(x, y):
+                r = []
+                for i in range(len(x)):
+                    r.append(chr(ord(x[i]) ^ ord(y[i])))
+                return ''.join(r)
+            def Hi(s, salt, iters):
+                ii = 1
+                p = s
+                try:
+                    p = s.encode('utf-8')
+                except:
+                    pass
+                ui_1 = HMAC(p, salt + '\0\0\0\01')
+                ui = ui_1
+                for i in range(iters - 1):
+                    ii += 1
+                    ui_1 = HMAC(p, ui_1)
+                    ui = XOR(ui, ui_1)
+                return ui
+            def H(s):
+                return hashfn(s).digest()
+            def scram_base64(s):
+                return ''.join(s.encode('base64').split('\n'))
+            if self.scram_step == 0:
+                self.scram_step = 1
+                self.scram_soup += ',' + data + ','
+                data = scram_parse(data)
+                # TODO: Should check cnonce here.
+                # TODO: Channel binding data goes in here too.
+                r = 'c=' + scram_base64(self.scram_gs2)
+                r += ',r=' + data['r']
+                self.scram_soup += r
+                salt = data['s'].decode('base64')
+                iter = int(data['i'])
+                SaltedPassword = Hi(self.password, salt, iter)
+                # TODO: Could cache this, along with salt+iter.
+                ClientKey = HMAC(SaltedPassword, 'Client Key')
+                StoredKey = H(ClientKey)
+                ClientSignature = HMAC(StoredKey, self.scram_soup)
+                ClientProof = XOR(ClientKey, ClientSignature)
+                r += ',p=' + scram_base64(ClientProof)
+                ServerKey = HMAC(SaltedPassword, 'Server Key')
+                self.scram_ServerSignature = HMAC(ServerKey, self.scram_soup)
+                sasl_data = scram_base64(r)
+                node = Node('response', attrs={'xmlns': NS_SASL},
+                    payload=[sasl_data])
+                self._owner.send(str(node))
+                raise NodeProcessed
+            if self.scram_step == 1:
+                data = scram_parse(data)
+                if data['v'].decode('base64') != self.scram_ServerSignature:
+                    # TODO: Not clear what to do here - need to abort.
+                    raise 'Hell'
+                node = Node('response', attrs={'xmlns': NS_SASL});
+                self._owner.send(str(node))
+                raise NodeProcessed
 
         # magic foo...
         chal = challenge_splitter(data)
@@ -350,7 +426,16 @@ class SASL(PlugIn):
             self.password = ''
         else:
             self.password = password
-        if self.mechanism == 'DIGEST-MD5':
+        if self.mechanism == 'SCRAM-SHA-1':
+            nonce = ''.join('%x' % randint(0, 2**28) for randint in \
+                itertools.repeat(random.randint, 7))
+            self.scram_soup = 'n=' + self.username + ',r=' + nonce
+            self.scram_gs2 = 'n,,' # No CB yet.
+            sasl_data = (self.scram_gs2 + self.scram_soup).encode('base64').\
+                replace('\n','')
+            node = Node('auth', attrs={'xmlns': NS_SASL,
+                'mechanism': self.mechanism}, payload=[sasl_data])
+        elif self.mechanism == 'DIGEST-MD5':
             def convert_to_iso88591(string):
                 try:
                     string = string.decode('utf-8').encode('iso-8859-1')