如何在PyCrypto中使用X509证书？

Question

我想用PyCrypto加密python中的一些数据.

但是我在使用时遇到错误key = RSA.importKey(pubkey):

RSA key format is not supported

密钥生成时:

openssl req -x509 -nodes -days 365 -newkey rsa:2048 -keyout mycert.key -out mycert.pem

代码是:

def encrypt(data):
    pubkey = open('mycert.pem').read()
    key = RSA.importKey(pubkey)
    cipher = PKCS1_OAEP.new(key)
    return cipher.encrypt(data)

Answer 1

PyCrypto不支持X.509证书.您必须首先使用以下命令提取公钥:

openssl x509 -inform pem -in mycert.pem -pubkey -noout > publickey.pem

然后,您可以使用RSA.importKey上publickey.pem.

如果您不想或不能使用openssl,您可以使用PEM X.509证书并使用纯Python执行此操作:

from Crypto.Util.asn1 import DerSequence
from Crypto.PublicKey import RSA
from binascii import a2b_base64

# Convert from PEM to DER
pem = open("mycert.pem").read()
lines = pem.replace(" ",'').split()
der = a2b_base64(''.join(lines[1:-1]))

# Extract subjectPublicKeyInfo field from X.509 certificate (see RFC3280)
cert = DerSequence()
cert.decode(der)
tbsCertificate = DerSequence()
tbsCertificate.decode(cert[0])
subjectPublicKeyInfo = tbsCertificate[6]

# Initialize RSA key
rsa_key = RSA.importKey(subjectPublicKeyInfo)