"Bad packet length 1231976033"

Darren Tucker dtucker at dtucker.net
Mon Apr 10 23:24:29 AEST 2023

On Mon, 10 Apr 2023 at 07:07, Peter Stuge <peter at stuge.se> wrote:
> Brian Candler wrote:
> > > What's odd is that the length is *always* 1231976033 (which is
> > > 0x496E7661 or "Inva" in ASCII).

One thing that can cause this is if the libc writes to stderr (ie fd
2) on some classes of error.   This is something libc should probably
not do, since in things that are not simple command line tools (say, a
ssh daemon) may be using fd 2 for something else entirely.

> > Could you get a tcpdump when this happens?
> Or debug output from at least the client (run ssh with -vvv) or
> preferably the server (run sshd with -ddd).

That's probably not going to show it, but strace'ing either the client
or the server will probably capture the error message in full.

Since you're using 9.1, the message could be an "Invalid free", since
there was a double-free bug in that release :-(

Darren Tucker (dtucker at dtucker.net)
GPG key 11EAA6FA / A86E 3E07 5B19 5880 E860  37F4 9357 ECEF 11EA A6FA
    Good judgement comes with experience. Unfortunately, the experience
usually comes from bad judgement.

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