Wireshark · Wireshark-dev: Re: [Wireshark-dev] [Outreachy] Multiple-line parsing of packets dissected over HTTP

[Joey Salazar <jgsal@xxxxxxxxxxxxxx>]

Hi Pascal,

On Wednesday, January 20, 2021 4:23 AM, Pascal Quantin wrote:

Hi Joey,

Le mar. 19 janv. 2021 à 23:35, Joey Salazar <jgsal@xxxxxxxxxxxxxx> a écrit :

On Tuesday, January 19, 2021 4:20 PM, Pascal Quantin wrote:

Le mar. 19 janv. 2021 à 23:09, Joey Salazar <jgsal@xxxxxxxxxxxxxx> a écrit :

Hi Pascal,

On Tuesday, January 19, 2021 11:19 AM, Pascal Quantin wrote:

Hi Joey,

Le mar. 19 janv. 2021 à 17:45, Joey Salazar via Wireshark-dev <wireshark-dev@xxxxxxxxxxxxx> a écrit :

Hi all,

In commit 33af2649 [1] we can keep dissecting the contents of the req, adv, and res packets by setting

 while (plen > 0) { }

either in `dissect_git_pdu()` or in `dissect_one_pkt_line()`, but for now in `dissect_git_pdu()` it'd be a bit messy, so wanted to ask for your feedback for getting `dissect_one_pkt_line()` to work properly first.

As you can see in pcap 169 [2], it correctly parses the length of the first line as 0x0014 (20 bytes) until `0x0a`, then it's supposed to get the length of the next line by the first 4 hex bytes in that line, but instead of reading the length as 0x0018 (24 bytes) it's reading it as 0x0010 (16 bytes), and anyways, this particular line's length actually is 59 bytes.

Suggestions on how to approach this?

So what is the code leading to this dissection? It does not seem to be gitlab.com/joeysal/wireshark/-/commit/33af2649927cb5660d4aeb64b9a9e9a58a1823aa as dissect_one_pkt_line() seem to read only one line

Yes, the code on that commit is what gives the parsing of the screenshot.

So what mechanism is used to call dissect_one_plt_line() a second time? With only screenshots and no pcap / code to look at, we can hardly help.

The code has already been provided. I confirm again that there hasn't been other lines added other than what's in that commit.

Does it mean that packet-http.c calls your dissector per line? Please provide more info, or even better share the pcap if you want us to provide some help.

Please find attached the pcap I'm using with the patch from the commit. As you can see, the way 167 and 255 are parsed is similar, but I'm referring specifically to 169 for now ("To-do" in line 121 will be for the cases where there's a 0000 terminator packet like the end of the first-line in 167) .

Unfortunately you did not share the associated TLS secret (or I missed it) that would allow me to decrypt the session and test your dissector. Could you send it?

My big apologies, I haven't worked with TLS certificates in the past and completely missed to send the secret. Apologies for taking your time. Please let me know if I'm missing anything else.

Thanks,

Joey

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