SSH connection hangs after authentication completes successfully - SSH

This is a discussion on SSH connection hangs after authentication completes successfully - SSH ; I am having the following connection problem: I have a Linux box A running OpenSSH 4.2p1. Whenever I try to open an SSH connection from A to some remote box B (running whatever SSH software) the authentication phase completes all ...

+ Reply to Thread
Results 1 to 3 of 3

Thread: SSH connection hangs after authentication completes successfully

  1. SSH connection hangs after authentication completes successfully

    I am having the following connection problem:

    I have a Linux box A running OpenSSH 4.2p1. Whenever I try to
    open an SSH connection from A to some remote box B (running whatever SSH
    software) the authentication phase completes all right. More to the
    point, SSH packets are exchanged between both parties without any
    problem, as long as everything happens in the authentication phase. For
    instance, when using password authentication, and intentionally using the
    wrong password, I can see in the server's traces all the dialog, in
    particular how the server sends back (and the client receives, in the
    client's traces) the corresponding authentication failure packets.

    When the authentication phase is completed successfully A sends a
    channel open packet, which elicits a channel open confirm packet from B.
    The problem is that the dialog hangs indefinitely at that point, until B
    just times out, waiting for A to send something. It seems to be an issue
    with A, because it happens for all sorts of different servers B. Even
    more, when A is the server and B is the client, the same behavior takes
    place.

    Any suggestions where to look for the cause? I know this is not a
    low-level networking issue per se (packets are exchanged without problems
    up till that point) or something to do firewalls (it happens even without
    firewalls.)


  2. Re: SSH connection hangs after authentication completes successfully

    "James H. Newman" writes:

    > I am having the following connection problem:


    > I have a Linux box A running OpenSSH 4.2p1. Whenever I try to
    >open an SSH connection from A to some remote box B (running whatever SSH
    >software) the authentication phase completes all right. More to the
    >point, SSH packets are exchanged between both parties without any
    >problem, as long as everything happens in the authentication phase. For
    >instance, when using password authentication, and intentionally using the
    >wrong password, I can see in the server's traces all the dialog, in
    >particular how the server sends back (and the client receives, in the
    >client's traces) the corresponding authentication failure packets.


    > When the authentication phase is completed successfully A sends a
    >channel open packet, which elicits a channel open confirm packet from B.
    >The problem is that the dialog hangs indefinitely at that point, until B
    >just times out, waiting for A to send something. It seems to be an issue
    >with A, because it happens for all sorts of different servers B. Even
    >more, when A is the server and B is the client, the same behavior takes
    >place.


    > Any suggestions where to look for the cause? I know this is not a
    >low-level networking issue per se (packets are exchanged without problems
    >up till that point) or something to do firewalls (it happens even without
    >firewalls.)


    What happens if you ssh from A to A? Does anyting appear in the logs? You
    could set up sshd to run in debug mode and see if there are any hints.




  3. Re: SSH connection hangs after authentication completessuccessfully

    On Sun, 19 Oct 2008 23:36:04 +0000, Unruh wrote:

    > "James H. Newman" writes:
    >
    >> I am having the following connection problem:

    >
    >> I have a Linux box A running OpenSSH 4.2p1. Whenever I try to
    >>open an SSH connection from A to some remote box B (running whatever SSH
    >>software) the authentication phase completes all right. More to the
    >>point, SSH packets are exchanged between both parties without any
    >>problem, as long as everything happens in the authentication phase. For
    >>instance, when using password authentication, and intentionally using
    >>the wrong password, I can see in the server's traces all the dialog, in
    >>particular how the server sends back (and the client receives, in the
    >>client's traces) the corresponding authentication failure packets.

    >
    >> When the authentication phase is completed successfully A sends a
    >>channel open packet, which elicits a channel open confirm packet from B.
    >>The problem is that the dialog hangs indefinitely at that point, until B
    >>just times out, waiting for A to send something. It seems to be an issue
    >>with A, because it happens for all sorts of different servers B. Even
    >>more, when A is the server and B is the client, the same behavior takes
    >>place.

    >
    >> Any suggestions where to look for the cause? I know this is not a
    >>low-level networking issue per se (packets are exchanged without
    >>problems up till that point) or something to do firewalls (it happens
    >>even without firewalls.)

    >
    > What happens if you ssh from A to A? Does anyting appear in the logs?
    > You could set up sshd to run in debug mode and see if there are any
    > hints.


    I have already done this. A to A works flawlessly. When setting
    both the SSH client and server in debug mode I get to see the correct SSH
    packet exchange to do the authentication. Like I said, it is immediately
    after establishing the channel that the connection hangs.



+ Reply to Thread