1 files changed, 176 insertions, 0 deletions
diff --git a/slixmpp/plugins/xep_0454/__init__.py b/slixmpp/plugins/xep_0454/__init__.py
new file mode 100644
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+++ b/slixmpp/plugins/xep_0454/__init__.py
@@ -0,0 +1,176 @@
+#!/usr/bin/env python3
+# -*- coding: utf-8 -*-
+# vim:fenc=utf-8 et ts=4 sts=4 sw=4
+#
+# Copyright © 2022 Maxime “pep” Buquet <pep@bouah.net>
+#
+# See the LICENSE file for copying permissions.
+
+"""
+    XEP-0454: OMEMO Media Sharing
+"""
+
+from typing import IO, Optional, Tuple
+
+from os import urandom
+from pathlib import Path
+from io import BytesIO, SEEK_END
+
+from cryptography.hazmat.primitives.ciphers import Cipher, algorithms, modes
+
+from slixmpp.plugins import BasePlugin
+from slixmpp.plugins.base import register_plugin
+
+
+class InvalidURL(Exception):
+    """Raised for URLs that either aren't HTTPS or already contain a fragment."""
+
+
+EXTENSIONS_MAP = {
+    'jpeg': 'jpg',
+    'text': 'txt',
+}
+
+class XEP_0454(BasePlugin):
+    """
+        XEP-0454: OMEMO Media Sharing
+    """
+
+    name = 'xep_0454'
+    description = 'XEP-0454: OMEMO Media Sharing'
+    dependencies = {'xep_0363'}
+
+    @staticmethod
+    def encrypt(input_file: Optional[IO[bytes]] = None, filename: Optional[Path] = None) -> Tuple[bytes, str]:
+        """
+            Encrypts file as specified in XEP-0454 for use in file sharing
+
+            :param input_file: Binary file stream on the file.
+            :param filename: Path to the file to upload.
+
+            One of input_file or filename must be specified. If both are
+            passed, input_file will be used and filename ignored.
+        """
+        if input_file is None and filename is None:
+            raise ValueError('Specify either filename or input_file parameter')
+
+        aes_gcm_iv = urandom(12)
+        aes_gcm_key = urandom(32)
+
+        aes_gcm = Cipher(
+            algorithms.AES(aes_gcm_key),
+            modes.GCM(aes_gcm_iv),
+        ).encryptor()
+
+        if input_file is None:
+            input_file = open(filename, 'rb')
+
+        payload = b''
+        while True:
+            buf = input_file.read(4096)
+            if not buf:
+                break
+            payload += aes_gcm.update(buf)
+
+        payload += aes_gcm.finalize() + aes_gcm.tag
+        fragment = aes_gcm_iv.hex() + aes_gcm_key.hex()
+        return (payload, fragment)
+
+    @staticmethod
+    def decrypt(input_file: IO[bytes], fragment: str) -> bytes:
+        """
+            Decrypts file-like.
+
+            :param input_file: Binary file stream on the file, containing the
+                               tag (16 bytes) at the end.
+            :param fragment: 88 hex chars string composed of iv (24 chars)
+                             + key (64 chars).
+        """
+
+        assert len(fragment) == 88
+        aes_gcm_iv = bytes.fromhex(fragment[:24])
+        aes_gcm_key = bytes.fromhex(fragment[24:])
+
+        # Find 16 bytes tag
+        input_file.seek(-16, SEEK_END)
+        tag = input_file.read()
+
+        aes_gcm = Cipher(
+            algorithms.AES(aes_gcm_key),
+            modes.GCM(aes_gcm_iv, tag),
+        ).decryptor()
+
+        size = input_file.seek(0, SEEK_END)
+        input_file.seek(0)
+
+        count = size - 16
+        plain = b''
+        while count >= 0:
+            buf = input_file.read(4096)
+            count -= len(buf)
+            if count <= 0:
+                buf += input_file.read()
+                buf = buf[:-16]
+            plain += aes_gcm.update(buf)
+        plain += aes_gcm.finalize()
+
+        return plain
+
+    @staticmethod
+    def format_url(url: str, fragment: str) -> str:
+        """Helper to format a HTTPS URL to an AESGCM URI"""
+        if not url.startswith('https://') or url.find('#') != -1:
+            raise InvalidURL
+        return 'aesgcm://' + url[len('https://'):] + '#' + fragment
+
+    @staticmethod
+    def map_extensions(ext: str) -> str:
+        """
+            Apply conversions to extensions to reduce the number of
+            variations, (e.g., JPEG -> jpg).
+        """
+        return EXTENSIONS_MAP.get(ext, ext).lower()
+
+    async def upload_file(
+        self,
+        filename: Path,
+        _size: Optional[int] = None,
+        content_type: Optional[str] = None,
+        **kwargs,
+    ) -> str:
+        """
+            Wrapper to xep_0363 (HTTP Upload)'s upload_file method.
+
+            :param input_file: Binary file stream on the file.
+            :param filename: Path to the file to upload.
+
+            Same as `XEP_0454.encrypt`, one of input_file or filename must be
+            specified. If both are passed, input_file will be used and
+            filename ignored.
+
+            Other arguments passed in are passed to the actual
+            `XEP_0363.upload_file` call.
+        """
+        input_file = kwargs.get('input_file')
+        payload, fragment = self.encrypt(input_file, filename)
+
+        # Prepare kwargs for upload_file call
+        new_filename = urandom(12).hex()  # Random filename to hide user-provided path
+        if filename.suffix:
+            new_filename += self.map_extensions(filename.suffix)
+        kwargs['filename'] = new_filename
+
+        input_enc = BytesIO(payload)
+        kwargs['input_file'] = input_enc
+
+        # Size must also be overriden if provided
+        size = input_enc.seek(0, SEEK_END)
+        input_enc.seek(0)
+        kwargs['size'] = size
+
+        kwargs['content_type'] = content_type
+
+        url = await self.xmpp['xep_0363'].upload_file(**kwargs)
+        return self.format_url(url, fragment)
+
+register_plugin(XEP_0454)