From 3721bf9f6b19ceaae75454956571c33caf5f1e87 Mon Sep 17 00:00:00 2001
From: Emmanuel Gil Peyrot <linkmauve@linkmauve.fr>
Date: Sat, 11 Feb 2017 04:02:20 +0000
Subject: [PATCH] Implement XEP-0300 (Use of Cryptographic Hash Functions in
 XMPP)

This is used to provide hash agility support and let other XEPs select
which hash function they support.
---
 slixmpp/plugins/xep_0300/__init__.py | 16 ++++++
 slixmpp/plugins/xep_0300/hash.py     | 80 ++++++++++++++++++++++++++++
 slixmpp/plugins/xep_0300/stanza.py   | 35 ++++++++++++
 3 files changed, 131 insertions(+)
 create mode 100644 slixmpp/plugins/xep_0300/__init__.py
 create mode 100644 slixmpp/plugins/xep_0300/hash.py
 create mode 100644 slixmpp/plugins/xep_0300/stanza.py

diff --git a/slixmpp/plugins/xep_0300/__init__.py b/slixmpp/plugins/xep_0300/__init__.py
new file mode 100644
index 00000000..522d40e3
--- /dev/null
+++ b/slixmpp/plugins/xep_0300/__init__.py
@@ -0,0 +1,16 @@
+"""
+    Slixmpp: The Slick XMPP Library
+    Copyright (C) 2017 Emmanuel Gil Peyrot
+    This file is part of Slixmpp.
+
+    See the file LICENSE for copying permission.
+"""
+
+from slixmpp.plugins.base import register_plugin
+
+from slixmpp.plugins.xep_0300 import stanza
+from slixmpp.plugins.xep_0300.stanza import Hash
+from slixmpp.plugins.xep_0300.hash import XEP_0300
+
+
+register_plugin(XEP_0300)
diff --git a/slixmpp/plugins/xep_0300/hash.py b/slixmpp/plugins/xep_0300/hash.py
new file mode 100644
index 00000000..0c71aac1
--- /dev/null
+++ b/slixmpp/plugins/xep_0300/hash.py
@@ -0,0 +1,80 @@
+"""
+    Slixmpp: The Slick XMPP Library
+    Copyright (C) 2017 Emmanuel Gil Peyrot
+    This file is part of Slixmpp.
+
+    See the file LICENSE for copying permission.
+"""
+
+from base64 import b64encode
+import hashlib
+import logging
+
+from slixmpp.plugins import BasePlugin
+from slixmpp.plugins.xep_0300 import stanza, Hash
+
+
+log = logging.getLogger(__name__)
+
+
+class XEP_0300(BasePlugin):
+
+    name = 'xep_0300'
+    description = 'XEP-0300: Use of Cryptographic Hash Functions in XMPP'
+    dependencies = {'xep_0030'}
+    stanza = stanza
+    default_config = {
+        'block_size': 1024 * 1024,  # One MiB
+        'prefered': 'sha-256',
+        'enable_sha-1': False,
+        'enable_sha-256': True,
+        'enable_sha-512': True,
+        'enable_sha3-256': True,
+        'enable_sha3-512': True,
+        'enable_BLAKE2b256': True,
+        'enable_BLAKE2b512': True,
+    }
+
+    _hashlib_function = {
+        'sha-1': hashlib.sha1,
+        'sha-256': hashlib.sha256,
+        'sha-512': hashlib.sha512,
+        'sha3-256': hashlib.sha3_256,
+        'sha3-512': hashlib.sha3_512,
+        'BLAKE2b256': lambda: hashlib.blake2b(digest_size=32),
+        'BLAKE2b512': lambda: hashlib.blake2b(digest_size=64),
+    }
+
+    def plugin_init(self):
+        namespace = 'urn:xmpp:hash-function-text-names:%s'
+        self.enabled_hashes = []
+        for algo in self._hashlib_function:
+            if getattr(self, 'enable_' + algo, False):
+                self.enabled_hashes.append(namespace % algo)
+
+    def session_bind(self, jid):
+        self.xmpp['xep_0030'].add_feature(Hash.namespace)
+
+        for namespace in self.enabled_hashes:
+            self.xmpp['xep_0030'].add_feature(namespace)
+
+    def plugin_end(self):
+        for namespace in self.enabled_hashes:
+            self.xmpp['xep_0030'].del_feature(namespace)
+
+        self.xmpp['xep_0030'].del_feature(feature=Hash.namespace)
+
+    def compute_hash(self, filename, function=None):
+        if function is None:
+            function = self.prefered
+        h = self._hashlib_function[function]()
+        with open(filename, 'rb') as f:
+            while True:
+                block = f.read(self.block_size)
+                if not block:
+                    break
+                h.update(block)
+        hash_elem = Hash()
+        hash_elem['algo'] = function
+        hash_elem['value'] = b64encode(h.digest())
+        return hash_elem
diff --git a/slixmpp/plugins/xep_0300/stanza.py b/slixmpp/plugins/xep_0300/stanza.py
new file mode 100644
index 00000000..f5ab483c
--- /dev/null
+++ b/slixmpp/plugins/xep_0300/stanza.py
@@ -0,0 +1,35 @@
+"""
+    Slixmpp: The Slick XMPP Library
+    Copyright (C) 2017 Emmanuel Gil Peyrot
+    This file is part of Slixmpp.
+
+    See the file LICENSE for copying permission.
+"""
+
+from slixmpp.xmlstream import ElementBase
+
+
+class Hash(ElementBase):
+    name = 'hash'
+    namespace = 'urn:xmpp:hashes:2'
+    plugin_attrib = 'hash'
+    interfaces = {'algo', 'value'}
+
+    allowed_algos = ['sha-1', 'sha-256', 'sha-512', 'sha3-256', 'sha3-512', 'BLAKE2b256', 'BLAKE2b512']
+
+    def set_algo(self, value):
+        if value in self.allowed_algos:
+            self._set_attr('algo', value)
+        elif value in [None, '']:
+            self._del_attr('algo')
+        else:
+            raise ValueError('Invalid algo: %s' % value)
+
+    def get_value(self):
+        return self.xml.text
+
+    def set_value(self, value):
+        self.xml.text = value
+
+    def del_value(self):
+        self.xml.text = ''