python paramiko CryptographyDeprecationWarning

import paramiko
client = paramiko.SSHClient()
client.connect(serverIp, port=serverPort, username=serverUser)

報警告如下：

paramiko\ecdsakey.py:164: CryptographyDeprecationWarning: Support for unsafe construction of public numbers from encoded data will be removed in a future version. Please use EllipticCurvePublicKey.from_encoded_point
  self.ecdsa_curve.curve_class(), pointinfo
paramiko\kex_ecdh_nist.py:39: CryptographyDeprecationWarning: encode_point has been deprecated on EllipticCurvePublicNumbers and will be removed in a future version. Please use EllipticCurvePublicKey.public_bytes to obtain both compressed and uncompressed point encoding.
  m.add_string(self.Q_C.public_numbers().encode_point())
paramiko\kex_ecdh_nist.py:96: CryptographyDeprecationWarning: Support for unsafe construction of public numbers from encoded data will be removed in a future version. Please use EllipticCurvePublicKey.from_encoded_point
  self.curve, Q_S_bytes
paramiko\kex_ecdh_nist.py:111: CryptographyDeprecationWarning: encode_point has been deprecated on EllipticCurvePublicNumbers and will be removed in a future version. Please use EllipticCurvePublicKey.public_bytes to obtain both compressed and uncompressed point encoding.
  hm.add_string(self.Q_C.public_numbers().encode_point())

原因

paramiko 2.4.2 依賴 cryptography，而最新的cryptography==2.5裏有一些棄用的API。

解決

刪掉cryptography 2.5，安裝2.4.2，就不會報錯了。

pip uninstall cryptography==2.5
pip install cryptography==2.4.2

補充

paramiko的issue #1369提到了這個問題，並已有PR #1379了，尚未合併。