Skip to content

umqtt connect function needs to support message length > 127 #171

New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Jump to bottom
Closed
martyvis opened this issue Apr 26, 2017 · 1 comment
Closed

umqtt connect function needs to support message length > 127 #171

martyvis opened this issue Apr 26, 2017 · 1 comment

Comments

@martyvis
Copy link

I was trying to get an esp8266 connecting to "Losant" via MQTT using the Losant native device identifiers as well as authentication. Unfortunately they have a 24 byte client ID, 36 byte user ID and 64 byte password. I found that "tshark" was interpreting these CONNECT requests as malformed :-

Transmission Control Protocol, Src Port: 1537 (1537), Dst Port: 1883 (1883), Seq: 1, Ack: 1, Len: 147
MQ Telemetry Transport Protocol
    Connect Command
        0001 0000 = Header Flags: 0x10 (Connect Command)
            0001 .... = Message Type: Connect Command (1)
            .... 0... = DUP Flag: Not set
            .... .00. = QOS Level: Fire and Forget (0)
            .... ...0 = Retain: Not set
        Msg Len: 17
[Malformed Packet: MQTT]
MQ Telemetry Transport Protocol
    Publish Message
        0011 0100 = Header Flags: 0x34 (Publish Message)
            0011 .... = Message Type: Publish Message (3)
            .... 0... = DUP Flag: Not set
            .... .10. = QOS Level: Assured Delivery (2)
            .... ...0 = Retain: Not set
        Msg Len: 101
[Malformed Packet: MQTT]

If I shortened the password to a maximal 51 bytes, it would get decoded correctly. I also curiously noticed the Msg Len was 127.

Transmission Control Protocol, Src Port: 24094 (24094), Dst Port: 1883 (1883), Seq: 1, Ack: 1, Len: 129
MQ Telemetry Transport Protocol
    Connect Command
        0001 0000 = Header Flags: 0x10 (Connect Command)
            0001 .... = Message Type: Connect Command (1)
            .... 0... = DUP Flag: Not set
            .... .00. = QOS Level: Fire and Forget (0)
            .... ...0 = Retain: Not set
        Msg Len: 127
        Protocol Name: MQTT
        Version: 4
        1100 0010 = Connect Flags: 0xc2
            1... .... = User Name Flag: Set
            .1.. .... = Password Flag: Set
            ..0. .... = Will Retain: Not set
            ...0 0... = QOS Level: Fire and Forget (0)
            .... .0.. = Will Flag: Not set
            .... ..1. = Clean Session Flag: Set
            .... ...0 = (Reserved): Not set
        Keep Alive: 0
        Client ID: 58ffe54ebea7820001dc1111
        User Name: 7e6f0030-5806-4d52-a1b0-8f1c48fe1111
        Password: passw0rd0123456789012345678901234567890123456789012

Going through the MQTT 3.1.1 specs I could see there was meant to be special handling for a message length >127 where we write the length into the header. I can see in the umqtt code for the publish function we seem to be doing this with the "while sz > 0x7f:" code. We need to do the same for the connect function.
@martyvis
Copy link
Author

Arrgh, looks like it is already being addressed at #163

Sign up for free to join this conversation on GitHub. Already have an account? Sign in to comment
Assignees
No one assigned
Labels
None yet
Projects
None yet
Milestone
No milestone
Development

No branches or pull requests
1 participant
@martyvis