# ciphers.py
#
# Copyright (C) 2006-2016 wolfSSL Inc.
#
# This file is part of wolfSSL. (formerly known as CyaSSL)
#
# wolfSSL is free software; you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation; either version 2 of the License, or
# (at your option) any later version.
#
# wolfSSL 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 General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with this program; if not, write to the Free Software
# Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA
from wolfcrypt._ffi   import ffi as _ffi
from wolfcrypt._ffi   import lib as _lib
from wolfcrypt.utils  import t2b
from wolfcrypt.random import Random

from wolfcrypt.exceptions import *


# key direction flags
_ENCRYPTION  = 0
_DECRYPTION  = 1


# feedback modes
MODE_ECB = 1 # Electronic Code Book
MODE_CBC = 2 # Cipher Block Chaining
MODE_CFB = 3 # Cipher Feedback
MODE_OFB = 5 # Output Feedback
MODE_CTR = 6 # Counter

_FEEDBACK_MODES = [MODE_ECB, MODE_CBC, MODE_CFB, MODE_OFB, MODE_CTR]


class _Cipher(object):
    """
    A **PEP 272: Block Encryption Algorithms** compliant
    **Symmetric Key Cipher**.
    """
    def __init__(self, key, mode, IV=None):
        if mode not in _FEEDBACK_MODES:
            raise ValueError("this mode is not supported")

        if mode == MODE_CBC:
            if IV is None:
                raise ValueError("this mode requires an 'IV' string")
        else:
            raise ValueError("this mode is not supported by this cipher")

        if self.key_size:
            if self.key_size != len(key):
                raise ValueError("key must be %d in length" % self.key_size)
        elif self._key_sizes:
            if len(key) not in self._key_sizes:
                raise ValueError("key must be %s in length" % self._key_sizes)
        else:
            if not len(key):
                raise ValueError("key must not be 0 in length")

        if IV is not None and len(IV) != self.block_size:
            raise ValueError("IV must be %d in length" % self.block_size)

        self._native_object = _ffi.new(self._native_type)
        self._enc = None
        self._dec = None
        self._key = t2b(key)

        if IV:
            self._IV = t2b(IV)
        else:
            self._IV = t2b("\0" * self.block_size)


    @classmethod
    def new(cls, key, mode, IV=None, **kwargs):
        """
        Returns a ciphering object, using the secret key contained in
        the string **key**, and using the feedback mode **mode**, which
        must be one of MODE_* defined in this module.

        If **mode** is MODE_CBC or MODE_CFB, **IV** must be provided and
        must be a string of the same length as the block size. Not
        providing a value of **IV** will result in a ValueError exception
        being raised.
        """
        return cls(key, mode, IV)


    def encrypt(self, string):
        """
        Encrypts a non-empty string, using the key-dependent data in
        the object, and with the appropriate feedback mode. The
        string's length must be an exact multiple of the algorithm's
        block size or, in CFB mode, of the segment size. Returns a
        string containing the ciphertext.
        """
        string = t2b(string)

        if not string or len(string) % self.block_size:
            raise ValueError(
                "string must be a multiple of %d in length" % self.block_size)

        if self._enc is None:
            self._enc = _ffi.new(self._native_type)
            ret = self._set_key(_ENCRYPTION)
            if ret < 0:
                raise WolfCryptError("Invalid key error (%d)" % ret)

        result = t2b("\0" * len(string))
        ret = self._encrypt(result, string)
        if ret < 0:
            raise WolfCryptError("Encryption error (%d)" % ret)

        return result


    def decrypt(self, string):
        """
        Decrypts **string**, using the key-dependent data in the
        object and with the appropriate feedback mode. The string's
        length must be an exact multiple of the algorithm's block
        size or, in CFB mode, of the segment size.  Returns a string
        containing the plaintext.
        """
        string = t2b(string)

        if not string or len(string) % self.block_size:
            raise ValueError(
                "string must be a multiple of %d in length" % self.block_size)

        if self._dec is None:
            self._dec = _ffi.new(self._native_type)
            ret = self._set_key(_DECRYPTION)
            if ret < 0:
                raise WolfCryptError("Invalid key error (%d)" % ret)

        result = t2b("\0" * len(string))
        ret = self._decrypt(result, string)
        if ret < 0:
            raise WolfCryptError("Decryption error (%d)" % ret)

        return result


class Aes(_Cipher):
    """
    The **Advanced Encryption Standard** (AES), a.k.a. Rijndael, is
    a symmetric-key cipher standardized by **NIST**.
    """
    block_size   = 16
    key_size     = None # 16, 24, 32
    _key_sizes   = [16, 24, 32]
    _native_type = "Aes *"


    def _set_key(self, direction):
        if direction == _ENCRYPTION:
            return _lib.wc_AesSetKey(
                self._enc, self._key, len(self._key), self._IV, _ENCRYPTION)
        else:
            return _lib.wc_AesSetKey(
                self._dec, self._key, len(self._key), self._IV, _DECRYPTION)


    def _encrypt(self, destination, source):
        return _lib.wc_AesCbcEncrypt(self._enc, destination, source,len(source))


    def _decrypt(self, destination, source):
        return _lib.wc_AesCbcDecrypt(self._dec, destination, source,len(source))


class _Rsa(object):
    RSA_MIN_PAD_SIZE = 11

    def __init__(self):
        self.native_object = _ffi.new("RsaKey *")
        ret = _lib.wc_InitRsaKey(self.native_object, _ffi.NULL)
        if ret < 0:
            raise WolfCryptError("Invalid key error (%d)" % ret)

        self._random = Random()
        ret = _lib.wc_RsaSetRNG(self.native_object, self._random.native_object)
        if ret < 0:
            raise WolfCryptError("Key initialization error (%d)" % ret)


    def __del__(self):
        if self.native_object:
            _lib.wc_FreeRsaKey(self.native_object)


class RsaPublic(_Rsa):
    def __init__(self, key):
        key = t2b(key)

        _Rsa.__init__(self)

        idx = _ffi.new("word32*")
        idx[0] = 0

        ret = _lib.wc_RsaPublicKeyDecode(key, idx, self.native_object, len(key))
        if ret < 0:
            raise WolfCryptError("Invalid key error (%d)" % ret)

        self.output_size = _lib.wc_RsaEncryptSize(self.native_object)
        if self.output_size <= 0:
            raise WolfCryptError("Invalid key error (%d)" % self.output_size)


    def encrypt(self, plaintext):
        """
        Encrypts **plaintext**, using the public key data in the
        object. The plaintext's length must not be greater than:

            **self.output_size - self.RSA_MIN_PAD_SIZE**

        Returns a string containing the ciphertext.
        """

        plaintext = t2b(plaintext)
        ciphertext = t2b("\0" * self.output_size)

        ret = _lib.wc_RsaPublicEncrypt(plaintext, len(plaintext),
                                       ciphertext, len(ciphertext),
                                       self.native_object,
                                       self._random.native_object)

        if ret != self.output_size:
            raise WolfCryptError("Encryption error (%d)" % ret)

        return ciphertext


    def verify(self, signature):
        """
        Verifies **signature**, using the public key data in the
        object. The signature's length must be equal to:

            **self.output_size**

        Returns a string containing the plaintext.
        """
        signature = t2b(signature)
        plaintext = t2b("\0" * self.output_size)

        ret = _lib.wc_RsaSSL_Verify(signature, len(signature),
                                    plaintext, len(plaintext),
                                    self.native_object)

        if ret < 0:
            raise WolfCryptError("Verify error (%d)" % ret)

        return plaintext[:ret]


class RsaPrivate(RsaPublic):
    def __init__(self, key):
        key = t2b(key)

        _Rsa.__init__(self)

        idx = _ffi.new("word32*")
        idx[0] = 0

        ret = _lib.wc_RsaPrivateKeyDecode(key, idx, self.native_object,len(key))
        if ret < 0:
            raise WolfCryptError("Invalid key error (%d)" % ret)

        self.output_size = _lib.wc_RsaEncryptSize(self.native_object)
        if self.output_size <= 0:
            raise WolfCryptError("Invalid key error (%d)" % self.output_size)


    def decrypt(self, ciphertext):
        """
        Decrypts **ciphertext**, using the private key data in the
        object. The ciphertext's length must be equal to:

            **self.output_size**

        Returns a string containing the plaintext.
        """
        ciphertext = t2b(ciphertext)
        plaintext = t2b("\0" * self.output_size)

        ret = _lib.wc_RsaPrivateDecrypt(ciphertext, len(ciphertext),
                                        plaintext, len(plaintext),
                                        self.native_object)

        if ret < 0:
            raise WolfCryptError("Decryption error (%d)" % ret)

        return plaintext[:ret]


    def sign(self, plaintext):
        """
        Signs **plaintext**, using the private key data in the object.
        The plaintext's length must not be greater than:

            **self.output_size - self.RSA_MIN_PAD_SIZE**

        Returns a string containing the signature.
        """
        plaintext = t2b(plaintext)
        signature = t2b("\0" * self.output_size)

        ret = _lib.wc_RsaSSL_Sign(plaintext, len(plaintext),
                                  signature, len(signature),
                                  self.native_object,
                                  self._random.native_object)

        if ret != self.output_size:
            raise WolfCryptError("Signature error (%d)" % ret)

        return signature
