Add compare argument to compute_caps_hash()

2 files changed, 23 insertions, 4 deletions

diff --git a/nbxmpp/structs.py b/nbxmpp/structs.py
index 6f7ac29..9253bee 100644
--- a/nbxmpp/structs.py
+++ b/nbxmpp/structs.py
@@ -112,13 +112,26 @@ AdHocCommandNote = namedtuple('AdHocCommandNote', 'text type')
 IBBData = namedtuple('IBBData', 'block_size sid seq type data')
 IBBData.__new__.__defaults__ = (None, None, None, None, None)
 
-DiscoInfo = namedtuple('DiscoInfo', 'jid node identities features dataforms')
-
 DiscoItems = namedtuple('DiscoItems', 'jid node items')
 DiscoItem = namedtuple('DiscoItem', 'jid name node')
 DiscoItem.__new__.__defaults__ = (None, None)
 
 
+class DiscoInfo(namedtuple('DiscoInfo', 'jid node identities features dataforms')):
+
+    __slots__ = []
+
+    def __new__(cls, jid, node, identities, features, dataforms):
+        return super(DiscoInfo, cls).__new__(cls, jid, node, identities,
+                                             features, dataforms)
+
+    def get_caps_hash(self):
+        try:
+            return self.node.split('#')[1]
+        except Exception:
+            return None
+
+
 class DiscoIdentity(namedtuple('DiscoIdentity', 'category type name lang')):
 
     __slots__ = []
diff --git a/nbxmpp/util.py b/nbxmpp/util.py
index 79b5060..8fec8ab 100644
--- a/nbxmpp/util.py
+++ b/nbxmpp/util.py
@@ -257,12 +257,14 @@ def text_to_color(text, background_color):
     return rc, gc, bc
 
 
-def compute_caps_hash(info):
+def compute_caps_hash(info, compare=True):
     """
     Compute caps hash according to XEP-0115, V1.5
     https://xmpp.org/extensions/xep-0115.html#ver-proc
 
     :param: info    DiscoInfo
+    :param: compare If True an exception is raised if the hash announced in
+                    the node attr is not equal to what is calculated
     """
     # Initialize an empty string S.
     string_ = ''
@@ -367,4 +369,8 @@ def compute_caps_hash(info):
                 string_ += '%s<' % value
 
     hash_ = hashlib.sha1(string_.encode())
-    return b64encode(hash_.digest())
+    b64hash = b64encode(hash_.digest())
+    if compare and b64hash != info.get_caps_hash():
+        raise DiscoInfoMalformed('Caps hashes differ: %s != %s' % (
+            b64hash, info.get_caps_hash()))
+    return b64hash