Create BLAKE2s.py

audit/BLAKE2s.py

@@ -0,0 +1,247 @@
+# ===================================================================
+#
+# Copyright (c) 2014, Legrandin <helderijs@gmail.com>
+# All rights reserved.
+#
+# Redistribution and use in source and binary forms, with or without
+# modification, are permitted provided that the following conditions
+# are met:
+#
+# 1. Redistributions of source code must retain the above copyright
+#    notice, this list of conditions and the following disclaimer.
+# 2. Redistributions in binary form must reproduce the above copyright
+#    notice, this list of conditions and the following disclaimer in
+#    the documentation and/or other materials provided with the
+#    distribution.
+#
+# THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+# "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+# LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
+# FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
+# COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
+# INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
+# BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
+# LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
+# CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+# LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
+# ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+# POSSIBILITY OF SUCH DAMAGE.
+# ===================================================================
+
+from binascii import unhexlify
+
+from Crypto.Util.py3compat import bord, tobytes
+
+from Crypto.Random import get_random_bytes
+from Crypto.Util._raw_api import (load_pycryptodome_raw_lib,
+                                  VoidPointer, SmartPointer,
+                                  create_string_buffer,
+                                  get_raw_buffer, c_size_t,
+                                  c_uint8_ptr)
+
+_raw_blake2s_lib = load_pycryptodome_raw_lib("Crypto.Hash._BLAKE2s",
+                        """
+                        int blake2s_init(void **state,
+                                         const uint8_t *key,
+                                         size_t key_size,
+                                         size_t digest_size);
+                        int blake2s_destroy(void *state);
+                        int blake2s_update(void *state,
+                                           const uint8_t *buf,
+                                           size_t len);
+                        int blake2s_digest(const void *state,
+                                           uint8_t digest[32]);
+                        int blake2s_copy(const void *src, void *dst);
+                        """)
+
+
+class BLAKE2s_Hash(object):
+    """A BLAKE2s hash object.
+    Do not instantiate directly. Use the :func:`new` function.
+
+    :ivar oid: ASN.1 Object ID
+    :vartype oid: string
+
+    :ivar block_size: the size in bytes of the internal message block,
+                      input to the compression function
+    :vartype block_size: integer
+
+    :ivar digest_size: the size in bytes of the resulting hash
+    :vartype digest_size: integer
+    """
+
+    # The internal block size of the hash algorithm in bytes.
+    block_size = 32
+
+    def __init__(self, data, key, digest_bytes, update_after_digest):
+
+        # The size of the resulting hash in bytes.
+        self.digest_size = digest_bytes
+
+        self._update_after_digest = update_after_digest
+        self._digest_done = False
+
+        # See https://tools.ietf.org/html/rfc7693
+        if digest_bytes in (16, 20, 28, 32) and not key:
+            self.oid = "1.3.6.1.4.1.1722.12.2.2." + str(digest_bytes)
+
+        state = VoidPointer()
+        result = _raw_blake2s_lib.blake2s_init(state.address_of(),
+                                               c_uint8_ptr(key),
+                                               c_size_t(len(key)),
+                                               c_size_t(digest_bytes)
+                                               )
+        if result:
+            raise ValueError("Error %d while instantiating BLAKE2s" % result)
+        self._state = SmartPointer(state.get(),
+                                   _raw_blake2s_lib.blake2s_destroy)
+        if data:
+            self.update(data)
+
+
+    def update(self, data):
+        """Continue hashing of a message by consuming the next chunk of data.
+
+        Args:
+            data (byte string/byte array/memoryview): The next chunk of the message being hashed.
+        """
+
+        if self._digest_done and not self._update_after_digest:
+            raise TypeError("You can only call 'digest' or 'hexdigest' on this object")
+
+        result = _raw_blake2s_lib.blake2s_update(self._state.get(),
+                                                 c_uint8_ptr(data),
+                                                 c_size_t(len(data)))
+        if result:
+            raise ValueError("Error %d while hashing BLAKE2s data" % result)
+        return self
+
+
+    def digest(self):
+        """Return the **binary** (non-printable) digest of the message that has been hashed so far.
+
+        :return: The hash digest, computed over the data processed so far.
+                 Binary form.
+        :rtype: byte string
+        """
+
+        bfr = create_string_buffer(32)
+        result = _raw_blake2s_lib.blake2s_digest(self._state.get(),
+                                                 bfr)
+        if result:
+            raise ValueError("Error %d while creating BLAKE2s digest" % result)
+
+        self._digest_done = True
+
+        return get_raw_buffer(bfr)[:self.digest_size]
+
+
+    def hexdigest(self):
+        """Return the **printable** digest of the message that has been hashed so far.
+
+        :return: The hash digest, computed over the data processed so far.
+                 Hexadecimal encoded.
+        :rtype: string
+        """
+
+        return "".join(["%02x" % bord(x) for x in tuple(self.digest())])
+
+
+    def verify(self, mac_tag):
+        """Verify that a given **binary** MAC (computed by another party)
+        is valid.
+
+        Args:
+          mac_tag (byte string/byte array/memoryview): the expected MAC of the message.
+
+        Raises:
+            ValueError: if the MAC does not match. It means that the message
+                has been tampered with or that the MAC key is incorrect.
+        """
+
+        secret = get_random_bytes(16)
+
+        mac1 = new(digest_bits=160, key=secret, data=mac_tag)
+        mac2 = new(digest_bits=160, key=secret, data=self.digest())
+
+        if mac1.digest() != mac2.digest():
+            raise ValueError("MAC check failed")
+
+
+    def hexverify(self, hex_mac_tag):
+        """Verify that a given **printable** MAC (computed by another party)
+        is valid.
+
+        Args:
+            hex_mac_tag (string): the expected MAC of the message, as a hexadecimal string.
+
+        Raises:
+            ValueError: if the MAC does not match. It means that the message
+                has been tampered with or that the MAC key is incorrect.
+        """
+
+        self.verify(unhexlify(tobytes(hex_mac_tag)))
+
+
+    def new(self, **kwargs):
+        """Return a new instance of a BLAKE2s hash object.
+        See :func:`new`.
+        """
+
+        if "digest_bytes" not in kwargs and "digest_bits" not in kwargs:
+            kwargs["digest_bytes"] = self.digest_size
+
+        return new(**kwargs)
+
+
+def new(**kwargs):
+    """Create a new hash object.
+
+    Args:
+        data (byte string/byte array/memoryview):
+            Optional. The very first chunk of the message to hash.
+            It is equivalent to an early call to :meth:`BLAKE2s_Hash.update`.
+        digest_bytes (integer):
+            Optional. The size of the digest, in bytes (1 to 32). Default is 32.
+        digest_bits (integer):
+            Optional and alternative to ``digest_bytes``.
+            The size of the digest, in bits (8 to 256, in steps of 8).
+            Default is 256.
+        key (byte string):
+            Optional. The key to use to compute the MAC (1 to 64 bytes).
+            If not specified, no key will be used.
+        update_after_digest (boolean):
+            Optional. By default, a hash object cannot be updated anymore after
+            the digest is computed. When this flag is ``True``, such check
+            is no longer enforced.
+
+    Returns:
+        A :class:`BLAKE2s_Hash` hash object
+    """
+
+    data = kwargs.pop("data", None)
+    update_after_digest = kwargs.pop("update_after_digest", False)
+
+    digest_bytes = kwargs.pop("digest_bytes", None)
+    digest_bits = kwargs.pop("digest_bits", None)
+    if None not in (digest_bytes, digest_bits):
+        raise TypeError("Only one digest parameter must be provided")
+    if (None, None) == (digest_bytes, digest_bits):
+        digest_bytes = 32
+    if digest_bytes is not None:
+        if not (1 <= digest_bytes <= 32):
+            raise ValueError("'digest_bytes' not in range 1..32")
+    else:
+        if not (8 <= digest_bits <= 256) or (digest_bits % 8):
+            raise ValueError("'digest_bytes' not in range 8..256, "
+                             "with steps of 8")
+        digest_bytes = digest_bits // 8
+
+    key = kwargs.pop("key", b"")
+    if len(key) > 32:
+        raise ValueError("BLAKE2s key cannot exceed 32 bytes")
+
+    if kwargs:
+        raise TypeError("Unknown parameters: " + str(kwargs))
+
+    return BLAKE2s_Hash(data, key, digest_bytes, update_after_digest)