Python Paho-mqtt client with server side certificate problem

My python paho-mqtt client failed to connect to broker which written in java. The broker has enabled SSL connection with a jks type cert. The broker is beyond my administration.

I convert the jks cert to pem cert to use in my python code. But when I run the code, there is an error:

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)

So I think there is a problem with the cert. How can I bypass the CA signature digest algorithm check?

I converted the jks cert to pem cert with following commands:

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

Here is my full code:

# -*- 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()

Solution 1:

I have figured it out. On client side, you do not need to configure server's self-signed cert. Now it worked!

# -*- 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

# the key steps here
context = ssl.SSLContext(ssl.PROTOCOL_TLSv1)
# if you do not want to check the cert hostname, skip it
# context.check_hostname = False
client.tls_set_context(context)

client.connect("192.168.110.2", 56785, 60)

client.loop_forever()

Python Paho-mqtt client with server side certificate problem

Solution 1:

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