251 lines
9.3 KiB
Python
251 lines
9.3 KiB
Python
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# -*- coding: utf-8 -*-
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#
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# Cipher/AES.py : AES
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#
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# ===================================================================
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# The contents of this file are dedicated to the public domain. To
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# the extent that dedication to the public domain is not available,
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# everyone is granted a worldwide, perpetual, royalty-free,
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# non-exclusive license to exercise all rights associated with the
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# contents of this file for any purpose whatsoever.
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# No rights are reserved.
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#
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# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
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# EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
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# MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
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# NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS
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# BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
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# ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
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# CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
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# SOFTWARE.
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# ===================================================================
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"""
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Module's constants for the modes of operation supported with AES:
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:var MODE_ECB: :ref:`Electronic Code Book (ECB) <ecb_mode>`
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:var MODE_CBC: :ref:`Cipher-Block Chaining (CBC) <cbc_mode>`
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:var MODE_CFB: :ref:`Cipher FeedBack (CFB) <cfb_mode>`
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:var MODE_OFB: :ref:`Output FeedBack (OFB) <ofb_mode>`
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:var MODE_CTR: :ref:`CounTer Mode (CTR) <ctr_mode>`
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:var MODE_OPENPGP: :ref:`OpenPGP Mode <openpgp_mode>`
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:var MODE_CCM: :ref:`Counter with CBC-MAC (CCM) Mode <ccm_mode>`
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:var MODE_EAX: :ref:`EAX Mode <eax_mode>`
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:var MODE_GCM: :ref:`Galois Counter Mode (GCM) <gcm_mode>`
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:var MODE_SIV: :ref:`Syntethic Initialization Vector (SIV) <siv_mode>`
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:var MODE_OCB: :ref:`Offset Code Book (OCB) <ocb_mode>`
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"""
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import sys
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from Crypto.Cipher import _create_cipher
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from Crypto.Util._raw_api import (load_pycryptodome_raw_lib,
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VoidPointer, SmartPointer,
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c_size_t, c_uint8_ptr)
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from Crypto.Util import _cpu_features
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from Crypto.Random import get_random_bytes
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_cproto = """
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int AES_start_operation(const uint8_t key[],
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size_t key_len,
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void **pResult);
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int AES_encrypt(const void *state,
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const uint8_t *in,
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uint8_t *out,
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size_t data_len);
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int AES_decrypt(const void *state,
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const uint8_t *in,
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uint8_t *out,
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size_t data_len);
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int AES_stop_operation(void *state);
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"""
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# Load portable AES
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_raw_aes_lib = load_pycryptodome_raw_lib("Crypto.Cipher._raw_aes",
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_cproto)
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# Try to load AES with AES NI instructions
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try:
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_raw_aesni_lib = None
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if _cpu_features.have_aes_ni():
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_raw_aesni_lib = load_pycryptodome_raw_lib("Crypto.Cipher._raw_aesni",
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_cproto.replace("AES",
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"AESNI"))
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# _raw_aesni may not have been compiled in
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except OSError:
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pass
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def _create_base_cipher(dict_parameters):
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"""This method instantiates and returns a handle to a low-level
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base cipher. It will absorb named parameters in the process."""
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use_aesni = dict_parameters.pop("use_aesni", True)
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try:
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key = dict_parameters.pop("key")
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except KeyError:
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raise TypeError("Missing 'key' parameter")
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if len(key) not in key_size:
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raise ValueError("Incorrect AES key length (%d bytes)" % len(key))
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if use_aesni and _raw_aesni_lib:
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start_operation = _raw_aesni_lib.AESNI_start_operation
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stop_operation = _raw_aesni_lib.AESNI_stop_operation
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else:
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start_operation = _raw_aes_lib.AES_start_operation
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stop_operation = _raw_aes_lib.AES_stop_operation
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cipher = VoidPointer()
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result = start_operation(c_uint8_ptr(key),
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c_size_t(len(key)),
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cipher.address_of())
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if result:
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raise ValueError("Error %X while instantiating the AES cipher"
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% result)
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return SmartPointer(cipher.get(), stop_operation)
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def _derive_Poly1305_key_pair(key, nonce):
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"""Derive a tuple (r, s, nonce) for a Poly1305 MAC.
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If nonce is ``None``, a new 16-byte nonce is generated.
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"""
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if len(key) != 32:
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raise ValueError("Poly1305 with AES requires a 32-byte key")
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if nonce is None:
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nonce = get_random_bytes(16)
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elif len(nonce) != 16:
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raise ValueError("Poly1305 with AES requires a 16-byte nonce")
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s = new(key[:16], MODE_ECB).encrypt(nonce)
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return key[16:], s, nonce
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def new(key, mode, *args, **kwargs):
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"""Create a new AES cipher.
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:param key:
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The secret key to use in the symmetric cipher.
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It must be 16, 24 or 32 bytes long (respectively for *AES-128*,
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*AES-192* or *AES-256*).
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For ``MODE_SIV`` only, it doubles to 32, 48, or 64 bytes.
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:type key: bytes/bytearray/memoryview
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:param mode:
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The chaining mode to use for encryption or decryption.
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If in doubt, use ``MODE_EAX``.
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:type mode: One of the supported ``MODE_*`` constants
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:Keyword Arguments:
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* **iv** (*bytes*, *bytearray*, *memoryview*) --
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(Only applicable for ``MODE_CBC``, ``MODE_CFB``, ``MODE_OFB``,
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and ``MODE_OPENPGP`` modes).
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The initialization vector to use for encryption or decryption.
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For ``MODE_CBC``, ``MODE_CFB``, and ``MODE_OFB`` it must be 16 bytes long.
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For ``MODE_OPENPGP`` mode only,
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it must be 16 bytes long for encryption
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and 18 bytes for decryption (in the latter case, it is
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actually the *encrypted* IV which was prefixed to the ciphertext).
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If not provided, a random byte string is generated (you must then
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read its value with the :attr:`iv` attribute).
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* **nonce** (*bytes*, *bytearray*, *memoryview*) --
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(Only applicable for ``MODE_CCM``, ``MODE_EAX``, ``MODE_GCM``,
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``MODE_SIV``, ``MODE_OCB``, and ``MODE_CTR``).
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A value that must never be reused for any other encryption done
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with this key (except possibly for ``MODE_SIV``, see below).
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For ``MODE_EAX``, ``MODE_GCM`` and ``MODE_SIV`` there are no
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restrictions on its length (recommended: **16** bytes).
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For ``MODE_CCM``, its length must be in the range **[7..13]**.
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Bear in mind that with CCM there is a trade-off between nonce
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length and maximum message size. Recommendation: **11** bytes.
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For ``MODE_OCB``, its length must be in the range **[1..15]**
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(recommended: **15**).
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For ``MODE_CTR``, its length must be in the range **[0..15]**
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(recommended: **8**).
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For ``MODE_SIV``, the nonce is optional, if it is not specified,
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then no nonce is being used, which renders the encryption
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deterministic.
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If not provided, for modes other than ``MODE_SIV```, a random
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byte string of the recommended length is used (you must then
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read its value with the :attr:`nonce` attribute).
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* **segment_size** (*integer*) --
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(Only ``MODE_CFB``).The number of **bits** the plaintext and ciphertext
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are segmented in. It must be a multiple of 8.
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If not specified, it will be assumed to be 8.
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* **mac_len** : (*integer*) --
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(Only ``MODE_EAX``, ``MODE_GCM``, ``MODE_OCB``, ``MODE_CCM``)
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Length of the authentication tag, in bytes.
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It must be even and in the range **[4..16]**.
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The recommended value (and the default, if not specified) is **16**.
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* **msg_len** : (*integer*) --
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(Only ``MODE_CCM``). Length of the message to (de)cipher.
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If not specified, ``encrypt`` must be called with the entire message.
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Similarly, ``decrypt`` can only be called once.
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* **assoc_len** : (*integer*) --
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(Only ``MODE_CCM``). Length of the associated data.
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If not specified, all associated data is buffered internally,
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which may represent a problem for very large messages.
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* **initial_value** : (*integer* or *bytes/bytearray/memoryview*) --
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(Only ``MODE_CTR``).
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The initial value for the counter. If not present, the cipher will
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start counting from 0. The value is incremented by one for each block.
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The counter number is encoded in big endian mode.
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* **counter** : (*object*) --
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Instance of ``Crypto.Util.Counter``, which allows full customization
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of the counter block. This parameter is incompatible to both ``nonce``
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and ``initial_value``.
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* **use_aesni** : (*boolean*) --
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Use Intel AES-NI hardware extensions (default: use if available).
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:Return: an AES object, of the applicable mode.
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"""
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kwargs["add_aes_modes"] = True
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return _create_cipher(sys.modules[__name__], key, mode, *args, **kwargs)
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MODE_ECB = 1
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MODE_CBC = 2
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MODE_CFB = 3
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MODE_OFB = 5
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MODE_CTR = 6
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MODE_OPENPGP = 7
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MODE_CCM = 8
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MODE_EAX = 9
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MODE_SIV = 10
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MODE_GCM = 11
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MODE_OCB = 12
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# Size of a data block (in bytes)
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block_size = 16
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# Size of a key (in bytes)
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key_size = (16, 24, 32)
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