Gpg module: send signed presences, and verify the signature in received presences.

1 files changed, 69 insertions, 1 deletions

diff --git a/plugins/gpg/__init__.py b/plugins/gpg/__init__.py
index 88259acf..2c6d9981 100644
--- a/plugins/gpg/__init__.py
+++ b/plugins/gpg/__init__.py
@@ -1,8 +1,76 @@
 from gpg import gnupg
+from xml.etree import cElementTree as ET
+import xml.sax.saxutils
 
 from plugin import BasePlugin
 
+import logging
+log = logging.getLogger(__name__)
+
+NS_SIGNED = "jabber:x:signed"
+NS_ENCRYPTED = "jabber:x:encrypted"
+
 class Plugin(BasePlugin):
     def init(self):
-        pass
+        self.contacts = {}
+        # a dict of {full-JID: 'signed'/'valid'/'invalid'}
+        # Whenever we receive a signed presence from a JID, we add it to this
+        # dict, this way we know if we can encrypt the messages we will send to
+        # this JID.
+        # If that resource sends a non-signed presence, then we remove it
+        # from that dict and stop encrypting our messages.
+        self.gpg = gnupg.GPG()
+        self.keyid = self.config.get('keyid', '') or None
+        self.passphrase = self.config.get('passphrase', '') or None
+        if not self.keyid:
+            self.core.information('No GPG keyid provided in the configuration', 'Warning')
+
+        self.add_event_handler('send_normal_presence', self.sign_presence)
+        self.add_event_handler('normal_presence', self.on_normal_presence)
+
+    def cleanup(self):
+        self.send_unsigned_presence()
+
+    def sign_presence(self, presence):
+        """
+        Sign every normal presence we send
+        """
+        signed_element = ET.Element('{%s}x' % (NS_SIGNED))
+        t = self.gpg.sign(presence['status'], keyid=self.keyid, passphrase=self.passphrase)
+        if not t:
+            self.core.information('Could not sign presence. Disabling GPG module', 'Info')
+            self.core.plugin_manager.unload('gpg')
+            return
+        signed_element.text = xml.sax.saxutils.escape(str(t))
+        presence.append(signed_element)
+
+    def send_unsigned_presence(self):
+        """
+        Send our current presence, to everyone, but unsigned, to indicate
+        that we cannot/do not want to encrypt/unencrypt messages.
+        """
+        current_presence = self.core.get_status()
+        self.core.command_status('%s %s' % (current_presence.show or 'available', current_presence.message,))
 
+    def on_normal_presence(self, presence, resource):
+        """
+        Check if it’s signed, if it is and we can verify the signature,
+        add 'valid' or 'invalid' into the dict. If it cannot be verified, just add
+        'signed'. Otherwise, do nothing.
+        """
+        signed = presence.find('{%s}x' % (NS_SIGNED,))
+        bare = presence['from'].bare
+        full = presence['from'].full
+        if signed is None:
+            log.debug('Not signed')
+            if bare in self.contacts.keys():
+                del self.contacts[bare]
+            return
+        if self.config.has_section('keys') and bare in self.config.options('keys'):
+            verify = self.gpg.verify(signed.text)
+            if verify:
+                self.contacts[full] = 'valid'
+            else:
+                self.contacts[full] = 'invalid'
+        else:
+            self.contacts[full] = 'signed'