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Error "TLS read fatal alert "bad record mac"" on agent

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  • awrow
    Junior Member
    • May 2020
    • 16

    #1

    Error "TLS read fatal alert "bad record mac"" on agent

    Hello,

    I have an error in agent client log:
    Code:
    active check configuration update from [62.X.X.X:10051] started to fail (TCP successful, cannot establish TLS to [[62.X.X.X:10051]: SSL_connect() set result code to SSL_ERROR_SSL: file ../ssl/record/rec_layer_s3.c line 1528: error:140943FC:SSL routines:ssl3_read_bytes:sslv3 alert bad record mac: SSL alert number 20: TLS read fatal alert "bad record mac")
    I checked PSK identity and PSK on both server and client.

    Client runs Ubuntu 18.04
    OpenSSL version is 1.1.1.

    What can cause this error?
  • awrow
    Junior Member
    • May 2020
    • 16

    #2
    I've disabled TLS. Another error rises:
    Code:
    Received empty response from Zabbix Agent at [92.X.X.X]. Assuming that agent dropped connection because of access permissions.

    I uncommented this lines:
    AllowRoot=1
    user=root

    Also I edited systemctl edit zabbix-agent :
    [Service]
    User=root
    Group=root

    UPD:
    Without TLS the connection works but with it shows the error I stated at the 1 post
    Last edited by awrow; 10-05-2020, 13:16.

    Comment

    • Hamardaban
      Senior Member
      Zabbix Certified SpecialistZabbix Certified Professional
      • May 2019
      • 2713

      #3
      The same PSK identification string is used, but different PSK values are used for communication between components.

      Comment

      • awrow
        Junior Member
        • May 2020
        • 16

        #4
        I used the same PSK Identity and PSK value for the server and the client. Between what "components"?

        Comment

      • awrow
        Junior Member
        • May 2020
        • 16

        #5
        Hamardaban
        Attached Files

        Comment

        • Hamardaban
          Senior Member
          Zabbix Certified SpecialistZabbix Certified Professional
          • May 2019
          • 2713

          #6
          Great. So in your case, this is not the most common reason.

          (and try specifying the psk identity without a space)
          Last edited by Hamardaban; 11-05-2020, 09:29.

          Comment

          • awrow
            Junior Member
            • May 2020
            • 16

            #7
            The firewall was disabled on both server and client.
            Also I tried to specify the psk identity without a space - no reaction.

            upd: there is no any hardware firewall
            Attached Files
            Last edited by awrow; 11-05-2020, 10:57.

            Comment

            • awrow
              Junior Member
              • May 2020
              • 16

              #8
              Could the reason be the different versions of OpenSSL on the server and the client? Right now I can't check this.

              Comment

              • awrow
                Junior Member
                • May 2020
                • 16

                #9
                TLS connections for other clients that previously worked started to fail.
                The problem could be in the 4.4 Zabbix version.

                Comment

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