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88 lines
2.5 KiB
88 lines
2.5 KiB
import os |
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from base64 import b64decode, b64encode |
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from cryptography.hazmat.primitives import hashes |
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from cryptography.hazmat.primitives.ciphers import Cipher, algorithms, modes |
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from cryptography.hazmat.primitives.kdf.pbkdf2 import PBKDF2HMAC |
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from cryptography.hazmat.backends import default_backend |
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_BACKEND = default_backend() |
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def decrypt(pwd, json): |
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iv = b64decode(json['iv']) |
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ct = b64decode(json['ct']) |
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salt = b64decode(json['salt']) |
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ts = json['ts'] / 8 |
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tag_start = len(ct) - ts |
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tag = ct[tag_start:] |
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ciphertext = ct[:tag_start] |
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mode_class = getattr(modes, json['mode'].upper()) |
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algo_class = getattr(algorithms, json['cipher'].upper()) |
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kdf = _kdf(json['ks'], iters=json['iter'], salt=salt)[0] |
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key = kdf.derive(pwd) |
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cipher = Cipher(algo_class(key), |
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mode_class(iv, tag, min_tag_length=ts), |
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backend=_BACKEND) |
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dec = cipher.decryptor() |
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result = dec.update(ciphertext) + dec.finalize() |
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return result |
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def encrypt(pwd, plaintext, salt_in=None, mode='gcm', algorithm='aes', |
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keysize=256, tagsize=128, iters=10000): |
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ts = tagsize / 8 |
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mode_class = getattr(modes, mode.upper()) |
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algo_class = getattr(algorithms, algorithm.upper()) |
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iv = os.urandom(16) |
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kdf, salt = _kdf(keysize, iters, salt_in) |
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key = kdf.derive(pwd) |
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cipher = Cipher(algo_class(key), |
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mode_class(iv, min_tag_length=ts), |
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backend=_BACKEND) |
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enc = cipher.encryptor() |
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ciphertext = enc.update(plaintext) + enc.finalize() |
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json = { |
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"v": 1, |
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"iv": b64encode(iv), |
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"salt": b64encode(salt), |
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"ct": b64encode(ciphertext + enc.tag[:ts]), |
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"iter": iters, |
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"ks": keysize, |
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"ts": tagsize, |
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"mode": mode, |
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"cipher": algorithm, |
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"adata": "" |
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} |
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return json |
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def _kdf(keysize=256, iters=10000, salt=None, **kwargs): |
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kdf_salt = salt or os.urandom(8) |
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kdf = PBKDF2HMAC(algorithm=hashes.SHA256(), |
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length=keysize / 8, |
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salt=kdf_salt, |
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iterations=iters, |
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backend=_BACKEND) |
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return kdf, kdf_salt |
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if __name__ == "__main__": |
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import json |
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blob = '{"iv":"/6dKRRAOZ60oyumLMQsBtg==","v":1,"iter":256000,"ks":128,"ts":64,"mode":"gcm","adata":"","cipher":"aes","salt":"s8+LFcBmbcc=","ct":"wTapp5CWmD6SFA=="}' |
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data = json.loads(blob) |
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result = decrypt('pwd', data) |
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assert result == "hi" |
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print(decrypt('pwd', encrypt('pwd', result, tagsize=64)))
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