使用Python验证SSL证书

Question

我需要编写一个脚本,通过HTTPS连接到公司内部网上的一堆站点,并验证他们的SSL证书是否有效; 他们没有过期,他们是为正确的地址等发出的.我们为这些网站使用我们自己的内部公司证书颁发机构,因此我们有CA的公钥来验证证书.

默认情况下,Python在使用HTTPS时接受并使用SSL证书,因此即使证书无效,诸如urllib2和Twisted之类的Python库也会很乐意使用证书.

是否有一个好的库可以让我通过HTTPS连接到一个站点并以这种方式验证它的证书？

如何在Python中验证证书？

Answer 1

我已经在Python Package Index中添加了一个发行版,它使得match_hostname()Python 3.2 ssl软件包中的函数可以在以前的Python版本中使用.

http://pypi.python.org/pypi/backports.ssl_match_hostname/

你可以安装它:

pip install backports.ssl_match_hostname

或者您可以将其作为项目中列出的依赖项setup.py.无论哪种方式,它可以像这样使用:

from backports.ssl_match_hostname import match_hostname, CertificateError
...
sslsock = ssl.wrap_socket(sock, ssl_version=ssl.PROTOCOL_SSLv3,
                      cert_reqs=ssl.CERT_REQUIRED, ca_certs=...)
try:
    match_hostname(sslsock.getpeercert(), hostname)
except CertificateError, ce:
    ...

Answer 2

您可以使用Twisted来验证证书.主API是CertificateOptions,它可以作为contextFactory各种函数的参数提供,例如listenSSL和startTLS.

不幸的是,Python和Twisted都没有提供实际进行HTTPS验证所需的大量CA证书,也没有HTTPS验证逻辑.由于PyOpenSSL的限制,你还不能完全正确地做到这一点,但是由于几乎所有证书都包含一个主题commonName,你可以得到足够的接近.

以下是验证Twisted HTTPS客户端的简单示例实现,它忽略通配符和subjectAltName扩展,并使用大多数Ubuntu发行版中"ca-certificates"包中存在的证书颁发机构证书.尝试使用您最喜欢的有效和无效的证书网站:).

import os
import glob
from OpenSSL.SSL import Context, TLSv1_METHOD, VERIFY_PEER, VERIFY_FAIL_IF_NO_PEER_CERT, OP_NO_SSLv2
from OpenSSL.crypto import load_certificate, FILETYPE_PEM
from twisted.python.urlpath import URLPath
from twisted.internet.ssl import ContextFactory
from twisted.internet import reactor
from twisted.web.client import getPage
certificateAuthorityMap = {}
for certFileName in glob.glob("/etc/ssl/certs/*.pem"):
    # There might be some dead symlinks in there, so let's make sure it's real.
    if os.path.exists(certFileName):
        data = open(certFileName).read()
        x509 = load_certificate(FILETYPE_PEM, data)
        digest = x509.digest('sha1')
        # Now, de-duplicate in case the same cert has multiple names.
        certificateAuthorityMap[digest] = x509
class HTTPSVerifyingContextFactory(ContextFactory):
    def __init__(self, hostname):
        self.hostname = hostname
    isClient = True
    def getContext(self):
        ctx = Context(TLSv1_METHOD)
        store = ctx.get_cert_store()
        for value in certificateAuthorityMap.values():
            store.add_cert(value)
        ctx.set_verify(VERIFY_PEER | VERIFY_FAIL_IF_NO_PEER_CERT, self.verifyHostname)
        ctx.set_options(OP_NO_SSLv2)
        return ctx
    def verifyHostname(self, connection, x509, errno, depth, preverifyOK):
        if preverifyOK:
            if self.hostname != x509.get_subject().commonName:
                return False
        return preverifyOK
def secureGet(url):
    return getPage(url, HTTPSVerifyingContextFactory(URLPath.fromString(url).netloc))
def done(result):
    print 'Done!', len(result)
secureGet("https://google.com/").addCallback(done)
reactor.run()

Answer 3

PycURL做得很漂亮.

以下是一个简短的例子.pycurl.error如果有些东西是可疑的,它会抛出一个带有错误代码和人类可读消息的元组.

import pycurl

curl = pycurl.Curl()
curl.setopt(pycurl.CAINFO, "myFineCA.crt")
curl.setopt(pycurl.SSL_VERIFYPEER, 1)
curl.setopt(pycurl.SSL_VERIFYHOST, 2)
curl.setopt(pycurl.URL, "https://internal.stuff/")

curl.perform()

您可能希望配置更多选项,例如存储结果的位置等.但不需要使用非必需品来混淆示例.

可能引发异常的示例:

(60, 'Peer certificate cannot be authenticated with known CA certificates')
(51, "common name 'CN=something.else.stuff,O=Example Corp,C=SE' does not match 'internal.stuff'")

我发现有用的一些链接是setopt和getinfo的libcurl-docs.

• http://curl.haxx.se/libcurl/c/curl_easy_setopt.html
• http://curl.haxx.se/libcurl/c/curl_easy_getinfo.html

Answer 4

从发布版本2.7.9/3.4.3开始,Python 默认尝试执行证书验证.

这已在PEP 467中提出,值得一读:https://www.python.org/dev/peps/pep-0476/

这些更改会影响所有相关的stdlib模块(urllib/urllib2,http,httplib).

相关文件:

https://docs.python.org/2/library/httplib.html#httplib.HTTPSConnection

此类现在默认执行所有必需的证书和主机名检查.要恢复到先前未验证的行为,可以将ssl._create_unverified_context()传递给context参数.

https://docs.python.org/3/library/http.client.html#http.client.HTTPSConnection

版本3.4.3中已更改:此类现在默认执行所有必需的证书和主机名检查.要恢复到先前未验证的行为,可以将ssl._create_unverified_context()传递给context参数.

请注意,新的内置验证基于系统提供的证书数据库.与之相反,请求包发布了自己的证书包.PEP 476的信任数据库部分讨论了这两种方法的优缺点.

Answer 5

这是一个演示证书验证的示例脚本:

import httplib
import re
import socket
import sys
import urllib2
import ssl

class InvalidCertificateException(httplib.HTTPException, urllib2.URLError):
    def __init__(self, host, cert, reason):
        httplib.HTTPException.__init__(self)
        self.host = host
        self.cert = cert
        self.reason = reason

    def __str__(self):
        return ('Host %s returned an invalid certificate (%s) %s\n' %
                (self.host, self.reason, self.cert))

class CertValidatingHTTPSConnection(httplib.HTTPConnection):
    default_port = httplib.HTTPS_PORT

    def __init__(self, host, port=None, key_file=None, cert_file=None,
                             ca_certs=None, strict=None, **kwargs):
        httplib.HTTPConnection.__init__(self, host, port, strict, **kwargs)
        self.key_file = key_file
        self.cert_file = cert_file
        self.ca_certs = ca_certs
        if self.ca_certs:
            self.cert_reqs = ssl.CERT_REQUIRED
        else:
            self.cert_reqs = ssl.CERT_NONE

    def _GetValidHostsForCert(self, cert):
        if 'subjectAltName' in cert:
            return [x[1] for x in cert['subjectAltName']
                         if x[0].lower() == 'dns']
        else:
            return [x[0][1] for x in cert['subject']
                            if x[0][0].lower() == 'commonname']

    def _ValidateCertificateHostname(self, cert, hostname):
        hosts = self._GetValidHostsForCert(cert)
        for host in hosts:
            host_re = host.replace('.', '\.').replace('*', '[^.]*')
            if re.search('^%s$' % (host_re,), hostname, re.I):
                return True
        return False

    def connect(self):
        sock = socket.create_connection((self.host, self.port))
        self.sock = ssl.wrap_socket(sock, keyfile=self.key_file,
                                          certfile=self.cert_file,
                                          cert_reqs=self.cert_reqs,
                                          ca_certs=self.ca_certs)
        if self.cert_reqs & ssl.CERT_REQUIRED:
            cert = self.sock.getpeercert()
            hostname = self.host.split(':', 0)[0]
            if not self._ValidateCertificateHostname(cert, hostname):
                raise InvalidCertificateException(hostname, cert,
                                                  'hostname mismatch')


class VerifiedHTTPSHandler(urllib2.HTTPSHandler):
    def __init__(self, **kwargs):
        urllib2.AbstractHTTPHandler.__init__(self)
        self._connection_args = kwargs

    def https_open(self, req):
        def http_class_wrapper(host, **kwargs):
            full_kwargs = dict(self._connection_args)
            full_kwargs.update(kwargs)
            return CertValidatingHTTPSConnection(host, **full_kwargs)

        try:
            return self.do_open(http_class_wrapper, req)
        except urllib2.URLError, e:
            if type(e.reason) == ssl.SSLError and e.reason.args[0] == 1:
                raise InvalidCertificateException(req.host, '',
                                                  e.reason.args[1])
            raise

    https_request = urllib2.HTTPSHandler.do_request_

if __name__ == "__main__":
    if len(sys.argv) != 3:
        print "usage: python %s CA_CERT URL" % sys.argv[0]
        exit(2)

    handler = VerifiedHTTPSHandler(ca_certs = sys.argv[1])
    opener = urllib2.build_opener(handler)
    print opener.open(sys.argv[2]).read()

Answer 6

或者通过使用请求库简化您的生活:

import requests
requests.get('https://somesite.com', cert='/path/server.crt', verify=True)

关于其用法的更多话.

Answer 7

M2Crypto可以进行验证.如果您愿意,也可以使用M2Crypto和Twisted.Chandler桌面客户端使用Twisted进行网络连接,使用M2Crypto进行SSL,包括证书验证.

基于Glyphs注释,似乎M2Crypto默认情况下比默认使用pyOpenSSL做更好的证书验证,因为M2Crypto也会检查subjectAltName字段.

我还在博客上写了如何获得 Mozilla Firefox附带的证书,并使用Python SSL解决方案.