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

[Joey Salazar via Wireshark-dev <wireshark-dev () wireshark org>]

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 () protonmail com> a écrit :
>
> > On Tuesday, January 19, 2021 4:20 PM, Pascal Quantin wrote:
> >
> > > Le mar. 19 janv. 2021 à 23:09, Joey Salazar <jgsal () protonmail com> 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 () wireshark org> 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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