我的python paho-mqtt client 无法连接到用java编写的broker。代理已启用具有jks类型证书的SSL连接。经纪人不在我的管理范围之内。

我将jks证书转换为pem证书，以便在我的python代码中使用。但是当我运行代码时，出现了一个错误：

Traceback (most recent call last):
  File "test.py", line 55, in <module>
    client.connect("192.168.110.2", 56785, 60)
  File "C:\Python\Python37\lib\site-packages\paho\mqtt\client.py", line 760, in
connect
    return self.reconnect()
  File "C:\Python\Python37\lib\site-packages\paho\mqtt\client.py", line 919, in
reconnect
    sock.do_handshake()
  File "C:\Python\Python37\lib\ssl.py", line 1117, in do_handshake
    self._sslobj.do_handshake()
ssl.SSLCertVerificationError: [SSL: CERTIFICATE_VERIFY_FAILED] certificate verify failed: CA signature digest algorithm too weak (_ssl.c:1056)

所以我认为证书有问题。如何绕过CA签名摘要算法检查？

我使用以下命令将jks证书转换为pem证书：

keytool -importkeystore -srckeystore server.jks -destkeystore server.p12 -srcstoretype jks -deststoretype pkcs12
openssl pkcs12 -in server.p12 -out server.pem

下面是我的完整代码：

# -*- coding:utf-8 -*-
import json
import ssl
import time
import paho.mqtt.client as mqtt
# constants
token = 'token '
mqtt_username = 'name'
mqtt_passwd = 'pass'
test_payload = {"type": "a_type","data": "my data","tokens": [token]}
def on_connect(client, userdata, flags, rc):
    print("Connected with result code " + str(rc))
    if rc == 0:
        # subscribe
        client.subscribe("Client/%s/Biz/Down" % token, 1)
        time.sleep(3)
        client.publish('Client/%s/Biz/Up' % token,
                       json.dumps(test_payload))
    # time.sleep(5)
    else:
        client.disconnect()
def on_message(client, userdata, msg):
    print(msg.topic + " " + str(msg.payload))
    if ("Client/%s/Biz/Down" % token) == msg.topic:
        client.disconnect()
client = mqtt.Client('', True, None, mqtt.MQTTv31)
client.username_pw_set(mqtt_username, mqtt_passwd)
client.on_connect = on_connect
client.on_message = on_message
client.tls_set('./server.pem')
client.connect("192.168.110.2", 56785, 60)
client.loop_forever()