Ssh asking for password; but then “Read from remote host … Connection reset by peer”

ssh

When I try to connect to remote server, ssh asks for password, checks it (if I put wrong password it will say "Permission denied") but doesn't let me in:

$ ssh user11@123
user11@123's password:

nothing happens, and some time later:

Read from remote host 123: Connection reset by peer

123 is hided server's ip.

Both ssh and sftp do this.

Remote is linux+OpenSSH and week ago ssh worked ok.

in -vvv mode I have after entry of password

debug3: packet_send2: adding 64 (len 58 padlen 6 extra_pad 64)
debug2: we sent a password packet, wait for reply
debug1: Authentication succeeded (password).
debug1: channel 0: new [client-session]
debug3: ssh_session2_open: channel_new: 0
debug2: channel 0: send open
debug1: Entering interactive session.

after some time…

debug1: channel 0: free: client-session, nchannels 1
debug3: channel 0: status: The following connections are open:
  #0 client-session (t3 r-1 i0/0 o0/0 fd 4/5 cfd -1)

debug3: channel 0: close_fds r 4 w 5 e 6 c -1
Read from remote host 123: Connection reset by peer
debug1: Transferred: stdin 0, stdout 0, stderr 63 bytes in 117.1 seconds
debug1: Bytes per second: stdin 0.0, stdout 0.0, stderr 0.5

Best Answer

There can be a few different causes of this, there's not enough information here to narrow down the problem exactly.

You'd have to check in your various log files on the server "123" in /var/log to see what's going on. This means checking out its console if you can't SSH to it.

An (incomplete) list of possible causes might be:

Some kind of runaway processes on your server filling up your process table, meaning it can't spawn your shell
Not enough RAM to spawn a shell.
Hard disk failure, meaning it can not load your shell from disk even though sshd might still be alive.
Your login shell set incorrectly to /bin/false or something
Somebody felt it would be funny to rm -rf / your server.
Some script kiddie tried to install a rootkit but botched it up to the degree that a shell won't launch.

Either way you're going to have to go to the console of the server to see what might be going on.

Related Solutions

Sshd on mac does no longer accept connections in inetd (-i) mode, but does in do not detach mode (-D), how to fix

It's pretty non-standard to use initd to start anything on a Mac. Instead, launchd is used, kicking off sshd in an ad hoc fashion (ie, it doesn't run as a typical server daemon until there's knock on the door). I suspect that your use of Linux-centric Webmin to manage ssh is contributing to the problem, since Webmin doesn't know a whole lot about launchd.

First, make sure the ssh launchd item is configured to load, just to eliminate the obvious.

sudo launchctl load -w /System/Library/LaunchDaemons/ssh.plist

This is akin to ticking the box on Server Admin.app in the Settings options to enable SSH. Check syslog to see if launchctl is complaining about something.

It's unclear why you would want Webmin to handle SSH, but Apple's default configuration might be illuminating.

There's a launchd item in /System/Library/LaunchDaemons called sshd.plist. This XML file indicates that /usr/libexec/sshd-keygen-wrapper is used as the "program" that actually kicks off /usr/sbin/sshd using the -i flag. (The sshd-keygen-wrapper program is a shell script to first set up initial rsa and dsa keys in empty user home dirs.) The sshd-keygen-wrapper, however, also kicks off sshd like exec /usr/sbin/sshd $@ and is a trusted/whitelisted program as far as the socket firewall is concerned.

You might also want to grab the default /etc/sshd_config from backup or another machine to eliminate that as a variable in troubleshooting.

SSH X11 not working

The reason ssh X forwarding wasn't working was because I have a /etc/ssh/sshrc config file.

The end of the sshd(8) man page states:

If ~/.ssh/rc exists, runs it; else if /etc/ssh/sshrc exists, runs it; otherwise runs xauth

So I add the following commands to /etc/ssh/sshrc (also from the sshd man page) on the server side:

if read proto cookie && [ -n "$DISPLAY" ]; then
        if [ `echo $DISPLAY | cut -c1-10` = 'localhost:' ]; then
                # X11UseLocalhost=yes
                echo add unix:`echo $DISPLAY |
                    cut -c11-` $proto $cookie
        else
                # X11UseLocalhost=no
                echo add $DISPLAY $proto $cookie
        fi | xauth -q -
fi

And it works!

Best Answer

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Sshd on mac does no longer accept connections in inetd (-i) mode, but does in do not detach mode (-D), how to fix

SSH X11 not working

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