如何在python中验证SSL证书?

时间:2010-12-09 20:54:27

标签: python ssl openssl x509certificate m2crypto

我需要验证证书是否由我的自定义CA签名。使用OpenSSL命令行实用程序很容易做到:

# Custom CA file: ca-cert.pem
# Cert signed by above CA: bob.cert
$ openssl verify -CAfile test-ca-cert.pem bob.cert
bob.cert: OK

但是我需要在Python中做同样的事情,我真的不想呼叫命令行实用程序。据我所知,M2Crypto是OpenSSL的“最完整”的python包装器,但我无法弄清楚如何完成命令行实用程序的功能!

引用this question了解如何在C代码中完成同样的任务,我已经能够完成一半了。 我选择的变量名与openssl verify命令行实用程序的源代码中使用的变量名相同,请参阅openssl-xxx/apps/verify.c

import M2Crypto as m2
# Load the certificates
cacert = m2.X509.load_cert('test-ca-cert.pem')   # Create cert object from CA cert file
bobcert = m2.X509.load_cert('bob.cert')     # Create cert object from Bob's cert file
cert_ctx = m2.X509.X509_Store()             # Step 1 from referenced C code steps
csc = m2.X509.X509_Store_Context(cert_ctx)  # Step 2 & 5
cert_ctx.add_cert(cacert)                   # Step 3
cert_ctx.add_cert(bobcert)                  # ditto
# Skip step 4 (no CRLs to add)
# Step 5 is combined with step 2...I think. (X509_STORE_CTX_init: Python creates and 
#   initialises an object in the same step)
# Skip step 6? (can't find anything corresponding to 
#   X509_STORE_CTX_set_purpose, not sure if we need to anyway???)
# 
# It all falls apart at this point, as steps 7 and 8 don't have any corresponding
# functions in M2Crypto -- I even grepped the entire source code of M2Crypto, and
# neither of the following functions are present in it:
# Step 7: X509_STORE_CTX_set_cert - Tell the context which certificate to validate.
# Step 8: X509_verify_cert - Finally, validate it

所以我已经到了一半,但我似乎无法完成验证!我错过了什么吗?我应该从M2Crypto使用其他功能吗?我应该寻找一个完全不同的OpenSSL python包装器吗?我怎样才能在python中完成这个任务!?!?

请注意,我正在使用证书加密/解密FILES,因此我对使用基于SSL连接的对等证书验证(具有already been answered)不感兴趣,因为我不喜欢有任何SSL连接。

3 个答案:

答案 0 :(得分:5)

使用普通的M2Crypto无法做到这一点,因为它没有包含一些必需的功能。好消息是,如果你安装了SWIG,你可以自己包装并使用M2Crypto代码。我不久前为自己制作了一个带有一些额外功能的模块,并决定现在发布它,因为它进行了这种验证。您可以在此处查看:https://github.com/abbot/m2ext。这是如何使用此模块验证证书的示例:

import sys
from m2ext import SSL
from M2Crypto import X509

print "Validating certificate %s using CApath %s" % (sys.argv[1], sys.argv[2])
cert = X509.load_cert(sys.argv[1])
ctx = SSL.Context()
ctx.load_verify_locations(capath=sys.argv[2])
if ctx.validate_certificate(cert):
    print "valid"
else:
    print "invalid"

不幸的是,M2Crypto开发似乎停滞不前(过去两年中bug跟踪器没有封闭的问题),维护人员忽略了我的错误和电子邮件以及其他一些补丁......

答案 1 :(得分:-1)

您可以使用遗憾的未记录的X509.verify方法来检查证书是否已使用CA的私钥进行签名。由于这在后台调用OpenSSL的x509_verify,我确信这也会正确检查所有参数(如过期):

from M2Crypto X509

cert = X509.load_cert("certificate-filename")

caCertificate = X509.load_cert("trusted-ca-filename")
caPublic = caCertificate.get_pubkey()

if cert.verify(caPublic) == 1:
     # Certificate is okay!
else:
     # not okay

答案 2 :(得分:-3)

就像你说的那样, OpenSSL需要连接

M2Crypto没有良好的验证

这个巧妙的想法怎么样:

import os 
os.system('openssl verify -CAfile ../ca-cert.pem bob.cert')

它很难看,但它确实有用!