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"""
Crypto logic for RFC3826.
https://tools.ietf.org/html/rfc3826
"""
from pysnmp.crypto import backend, CRYPTODOME, CRYPTOGRAPHY, generic_decrypt, generic_encrypt
if backend == CRYPTOGRAPHY:
from cryptography.hazmat.backends import default_backend
from cryptography.hazmat.primitives.ciphers import algorithms, Cipher, modes
elif backend == CRYPTODOME:
from Cryptodome.Cipher import AES
def _cryptodome_cipher(key, iv):
"""Build a Pycryptodome AES Cipher object.
:param bytes key: Encryption key
:param bytes IV: Initialization vector
:returns: AES Cipher instance
"""
return AES.new(key, AES.MODE_CFB, iv, segment_size=128)
def _cryptography_cipher(key, iv):
"""Build a cryptography AES Cipher object.
:param bytes key: Encryption key
:param bytes IV: Initialization vector
:returns: AES Cipher instance
:rtype: cryptography.hazmat.primitives.ciphers.Cipher
"""
return Cipher(
algorithm=algorithms.AES(key),
mode=modes.CFB(iv),
backend=default_backend()
)
_CIPHER_FACTORY_MAP = {
CRYPTOGRAPHY: _cryptography_cipher,
CRYPTODOME: _cryptodome_cipher
}
def encrypt(plaintext, key, iv):
"""Encrypt data using AES 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 AES 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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