ssh over stunnel hangs on second connection
cygwin@kosowsky.org
cygwin@kosowsky.org
Thu Feb 15 23:14:18 GMT 2024
Here is some more strangeness:
1. (As before)
- ssh first time -> succeeds
- logout
- ssh again -> hangs
2. Another sequence
- SESSION 1: ssh first time -> succeeds
- SESSION 2: ssh second time -> succeeds (without logging out session 1)
- ...
- SESSION N: ssh n'th time -> succeeds (without logging out any of the previous ones
- logout of any of the first N-sessions
- SESSION N+1: ssh -> FAILS
- SESSION N+2: ssh -> FAILS
- ...
So it seems like logging out of an 'ssh over stunnel' session somehow
causes 'stunnel' to hang on any succeeding sessions
"" wrote at about 14:23:30 -0500 on Thursday, February 15, 2024:
> I am using Cygwin stunnel 5.71 on Windows 11 to connect to 'ssh' into my Ubuntu
> server over 'stunnel'.
>
> - The first time I ssh via stunnel it works fine The second time, I
> - try to connect, it hangs with 'ssh -v' showing only the initial
> local steps of connection:
>
> OpenSSH_9.5p1, OpenSSL 3.0.12 24 Oct 2023
> debug1: Reading configuration data /home/myuser/.ssh/config
> debug1: Reading configuration data /etc/ssh_config
> debug1: Connecting to localhost [::1] port 2222.
> debug1: Connection established.
> debug1: identity file /home/myuser/.ssh/id_rsa type 0
> debug1: identity file /home/myuser/.ssh/id_rsa-cert type -1
> debug1: identity file /home/myuser/.ssh/id_ecdsa type -1
> debug1: identity file /home/myuser/.ssh/id_ecdsa-cert type -1
> debug1: identity file /home/myuser/.ssh/id_ecdsa_sk type -1
> debug1: identity file /home/myuser/.ssh/id_ecdsa_sk-cert type -1
> debug1: identity file /home/myuser/.ssh/id_ed25519 type -1
> debug1: identity file /home/myuser/.ssh/id_ed25519-cert type -1
> debug1: identity file /home/myuser/.ssh/id_ed25519_sk type -1
> debug1: identity file /home/myuser/.ssh/id_ed25519_sk-cert type -1
> debug1: identity file /home/myuser/.ssh/id_xmss type -1
> debug1: identity file /home/myuser/.ssh/id_xmss-cert type -1
> debug1: identity file /home/myuser/.ssh/id_dsa type -1
> debug1: identity file /home/myuser/.ssh/id_dsa-cert type -1
> debug1: Local version string SSH-2.0-OpenSSH_9.5
>
> and '/var/log/stunnel' on the Cygwin client failing early:
>
> LOG7[main]: Found 1 ready file descriptor(s)
> LOG7[main]: FD=4 events=0x1 revents=0x0
> LOG7[main]: FD=8 events=0x1 revents=0x1
> LOG7[main]: FD=10 events=0x1 revents=0x0
> LOG7[main]: Service [ssh] accepted (FD=3) from ::1:52718
>
>
> - If I connect a *third* (or more times), 'ssh -v' hangs with the same
> output as above, but there is *no* additional logging in
> '/var/log/stunnel' on the client.
>
>
> It thus is acting as if 'stunnel' on the Cygwin client itself somehow
> hangs/becomes unresponsive early in the second 'ssh' connection
> attempt.
>
> Note that the client '/usr/bin/stunnel/ process continues to run so it
> doesn't crash.
>
> Killing and relaunching /usr/bin/stunnel restarts the situation
> allowing me to ssh-over-stunel OK on the first attempt but again
> hanging on the 2nd and subsequent 'ssh' attempts
>
> Also, the 'stunnel' server on Ubuntu continues to run throughout since
> I can continue to ssh-over-stunnel into it from other machines.
>
> It doesn't *seem* to be a firewall problem, since it connects fine the
> first time. Nor does it seem to be a network or 'stunnel' server
> problem.
>
> Any ideas on why this is happening?
>
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