[Bug 1424] New: Cannot signal a process over a channel (rfc 4254, section 6 .9)

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https://bugzilla.mindrot.org/show_bug.cgi?id=1424

           Summary: Cannot signal a process over a channel (rfc 4254,
                    section 6.9)
    Classification: Unclassified
           Product: Portable OpenSSH
           Version: 4.7p1
          Platform: ix86
        OS/Version: Linux
            Status: NEW
          Severity: normal
          Priority: P2
         Component: sshd
        AssignedTo: bitbucket at mindrot.org
        ReportedBy: dazuma at gmail.com


It does not appear that sshd in OpenSSH implements section 6.9 of rfc
4254. That is, sending SSH_MSG_CHANNEL_REQUEST with type "signal" for a
channel, has no effect.

This is being reproduced with a custom client, connecting to OpenSSH
4.7p1 sshd running on Linux (Fedora 8 package openssh-4.7p1-4.fc8). I
opened a channel, started a simple long-running remote process (e.g.
sleep) with an "exec", and then attempted to send the "TERM" signal as
described in the rfc, with want_reply set to TRUE. The server sent back
SSH_MSG_CHANNEL_FAILURE, and the process was unaffected.

However, I do not believe this is platform-specific or usage-specific.
Looking at the code for session.c in cvs, it appears that the function
session_input_channel_req does not recognize an rtype of "signal".
http://www.openbsd.org/cgi-bin/cvsweb/src/usr.bin/ssh/session.c?rev=1.224

This appears to have been reported before on the mailing list, but
there were no replies, and I could not find a bug open for it.
http://marc.info/?l=openssh-unix-dev&m=115992994907390&w=2

Also see this thread from some years ago, which includes a patch
against an older version of OpenSSH:
http://marc.info/?l=openssh-unix-dev&m=104300802407848&w=2

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