--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/libervia/backend/memory/crypto.py	Fri Jun 02 11:49:51 2023 +0200
@@ -0,0 +1,170 @@
+#!/usr/bin/env python3
+
+# SAT: a jabber client
+# Copyright (C) 2009-2021 Jérôme Poisson (goffi@goffi.org)
+# Copyright (C) 2013-2016 Adrien Cossa (souliane@mailoo.org)
+
+# This program is free software: you can redistribute it and/or modify
+# it under the terms of the GNU Affero General Public License as published by
+# the Free Software Foundation, either version 3 of the License, or
+# (at your option) any later version.
+
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU Affero General Public License for more details.
+
+# You should have received a copy of the GNU Affero General Public License
+# along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+from os import urandom
+from base64 import b64encode, b64decode
+from cryptography.hazmat.primitives import hashes
+from cryptography.hazmat.primitives.kdf.pbkdf2 import PBKDF2HMAC
+from cryptography.hazmat.primitives.ciphers import Cipher, algorithms, modes
+from cryptography.hazmat.backends import default_backend
+
+
+crypto_backend = default_backend()
+
+
+class BlockCipher:
+
+    BLOCK_SIZE = 16
+    MAX_KEY_SIZE = 32
+    IV_SIZE = BLOCK_SIZE  # initialization vector size, 16 bits
+
+    @staticmethod
+    def encrypt(key, text, leave_empty=True):
+        """Encrypt a message.
+
+        Based on http://stackoverflow.com/a/12525165
+
+        @param key (unicode): the encryption key
+        @param text (unicode): the text to encrypt
+        @param leave_empty (bool): if True, empty text will be returned "as is"
+        @return (D(str)): base-64 encoded encrypted message
+        """
+        if leave_empty and text == "":
+            return ""
+        iv = BlockCipher.get_random_key()
+        key = key.encode()
+        key = (
+            key[: BlockCipher.MAX_KEY_SIZE]
+            if len(key) >= BlockCipher.MAX_KEY_SIZE
+            else BlockCipher.pad(key)
+        )
+
+        cipher = Cipher(algorithms.AES(key), modes.CFB8(iv), backend=crypto_backend)
+        encryptor = cipher.encryptor()
+        encrypted = encryptor.update(BlockCipher.pad(text.encode())) + encryptor.finalize()
+        return b64encode(iv + encrypted).decode()
+
+    @staticmethod
+    def decrypt(key, ciphertext, leave_empty=True):
+        """Decrypt a message.
+
+        Based on http://stackoverflow.com/a/12525165
+
+        @param key (unicode): the decryption key
+        @param ciphertext (base-64 encoded str): the text to decrypt
+        @param leave_empty (bool): if True, empty ciphertext will be returned "as is"
+        @return: Deferred: str or None if the password could not be decrypted
+        """
+        if leave_empty and ciphertext == "":
+            return ""
+        ciphertext = b64decode(ciphertext)
+        iv, ciphertext = (
+            ciphertext[: BlockCipher.IV_SIZE],
+            ciphertext[BlockCipher.IV_SIZE :],
+        )
+        key = key.encode()
+        key = (
+            key[: BlockCipher.MAX_KEY_SIZE]
+            if len(key) >= BlockCipher.MAX_KEY_SIZE
+            else BlockCipher.pad(key)
+        )
+
+        cipher = Cipher(algorithms.AES(key), modes.CFB8(iv), backend=crypto_backend)
+        decryptor = cipher.decryptor()
+        decrypted = decryptor.update(ciphertext) + decryptor.finalize()
+        return BlockCipher.unpad(decrypted)
+
+    @staticmethod
+    def get_random_key(size=None, base64=False):
+        """Return a random key suitable for block cipher encryption.
+
+        Note: a good value for the key length is to make it as long as the block size.
+
+        @param size: key length in bytes, positive or null (default: BlockCipher.IV_SIZE)
+        @param base64: if True, encode the result to base-64
+        @return: str (eventually base-64 encoded)
+        """
+        if size is None or size < 0:
+            size = BlockCipher.IV_SIZE
+        key = urandom(size)
+        return b64encode(key) if base64 else key
+
+    @staticmethod
+    def pad(s):
+        """Method from http://stackoverflow.com/a/12525165"""
+        bs = BlockCipher.BLOCK_SIZE
+        return s + (bs - len(s) % bs) * (chr(bs - len(s) % bs)).encode()
+
+    @staticmethod
+    def unpad(s):
+        """Method from http://stackoverflow.com/a/12525165"""
+        s = s.decode()
+        return s[0 : -ord(s[-1])]
+
+
+class PasswordHasher:
+
+    SALT_LEN = 16  # 128 bits
+
+    @staticmethod
+    def hash(password, salt=None, leave_empty=True):
+        """Hash a password.
+
+        @param password (str): the password to hash
+        @param salt (base-64 encoded str): if not None, use the given salt instead of a random value
+        @param leave_empty (bool): if True, empty password will be returned "as is"
+        @return: Deferred: base-64 encoded str
+        """
+        if leave_empty and password == "":
+            return ""
+        salt = (
+            b64decode(salt)[: PasswordHasher.SALT_LEN]
+            if salt
+            else urandom(PasswordHasher.SALT_LEN)
+        )
+
+        # we use PyCrypto's PBKDF2 arguments while porting to crytography, to stay
+        # compatible with existing installations. But this is temporary and we need
+        # to update them to more secure values.
+        kdf = PBKDF2HMAC(
+            # FIXME: SHA1() is not secure, it is used here for historical reasons
+            #   and must be changed as soon as possible
+            algorithm=hashes.SHA1(),
+            length=16,
+            salt=salt,
+            iterations=1000,
+            backend=crypto_backend
+        )
+        key = kdf.derive(password.encode())
+        return b64encode(salt + key).decode()
+
+    @staticmethod
+    def verify(attempt, pwd_hash):
+        """Verify a password attempt.
+
+        @param attempt (str): the attempt to check
+        @param pwd_hash (str): the hash of the password
+        @return: Deferred: boolean
+        """
+        assert isinstance(attempt, str)
+        assert isinstance(pwd_hash, str)
+        leave_empty = pwd_hash == ""
+        attempt_hash = PasswordHasher.hash(attempt, pwd_hash, leave_empty)
+        assert isinstance(attempt_hash, str)
+        return attempt_hash == pwd_hash