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"""
Crypto logic for Reeder 3DES-EDE for USM (Internet draft).
https://tools.ietf.org/html/draft-reeder-snmpv3-usm-3desede-00
"""
from pysnmp.crypto import backend, CRYPTODOME, CRYPTOGRPAHY, generic_decrypt, generic_encrypt
if backend == CRYPTOGRPAHY:
from cryptography.hazmat.backends import default_backend
from cryptography.hazmat.primitives.ciphers import algorithms, Cipher, modes
elif backend == CRYPTODOME:
from Cryptodome.Cipher import DES3
def _cryptodome_cipher(key, iv):
"""Build a Pycryptodome DES3 Cipher object.
:param bytes key: Encryption key
:param bytes IV: Initialization vector
:returns: DES3 Cipher instance
"""
return DES3.new(key, DES3.MODE_CBC, iv)
def _cryptography_cipher(key, iv):
"""Build a cryptography TripleDES Cipher object.
:param bytes key: Encryption key
:param bytes IV: Initialization vector
:returns: TripleDES Cipher instance
:rtype: cryptography.hazmat.primitives.ciphers.Cipher
"""
return Cipher(
algorithm=algorithms.TripleDES(key),
mode=modes.CBC(iv),
backend=default_backend()
)
_CIPHER_FACTORY_MAP = {
CRYPTOGRPAHY: _cryptography_cipher,
CRYPTODOME: _cryptodome_cipher
}
def encrypt(plaintext, key, iv):
"""Encrypt data using triple DES on the available backend.
:param bytes plaintext: Plaintext data to encrypt
:param bytes key: Encryption key
:param bytes IV: Initialization vector
:returns: Encrypted ciphertext
:rtype: bytes
"""
return generic_encrypt(_CIPHER_FACTORY_MAP, plaintext, key, iv)
def decrypt(ciphertext, key, iv):
"""Decrypt data using triple DES on the available backend.
:param bytes ciphertext: Ciphertext data to decrypt
:param bytes key: Encryption key
:param bytes IV: Initialization vector
:returns: Decrypted plaintext
:rtype: bytes
"""
return generic_decrypt(_CIPHER_FACTORY_MAP, ciphertext, key, iv)
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