FWIW, now that privsep is mandatory I have no objection to including signal support in sshd. On Wed, 25 Jul 2018, Yonathan Bleyfuesz wrote: > Hi all, > > I would like to propose some ideas to revivify this subject. > > -First, we could add support on the client to send signal thanks to the escape characters. > (code : https://github.com/JawaGL/openssh-portable/commit/5bc9e6bc959b1b0f89d7ca7b4b04d7c37079fef0 ). > > With this, in order to send a message requesting the server to send a SIGTERM to the remote process, you need to type “~ST” which is not really invasive client-side. > > But this means that the client has to enable TTY. > > > -Secondly , server-side, there is a problem with the currently suggested patch : it only works when we do an ‘exec’ request to the server (eg : ssh some-host “some; commands;”). > > This is because in the other possible configuration, a shell is launched by the server. Then when we launch a process, it is forked by this shell and thus it has its own group-id. > > When the user launches a signal-request hoping to reach a blocking process, the pid that is used by the ‘killpg’ function is the one of the shell. So it is this shell that catches the signal resulting in it: > - dying and leaving zombies > - dying and taking its child with him (SIGHUP and SIGKILL) > - ignoring the signal (SIGINT, SIGTERM, SIGQUIT). > > Example of ID’s when I connect to a server and launch the script test_signal.sh : > PID PPID PGID SID > 4060 1598 4060 1556 sshd sshd: root@pts/2 > 4062 4060 4062 4062 bash -bash > 4075 4062 4075 4062 sh sh test_signal.sh > 4076 4075 4075 4062 sh sh test_signal.sh > > So in order to take this use case into account we could use the 'tcgetpgrp()’ function from ‘unistd.h’. > (code : https://github.com/JawaGL/openssh-portable/commit/3667c0d90688c43ac0729083f73afa65102226b4 ) > > Of course this would still work if there are no TTY present since we can still access the PGID of the forked child in the session attributes. > > -Finally, in order to test these functionalities, we could integrate a test case in the regress folder. (code : https://github.com/JawaGL/openssh-portable/commit/02c39b15363c54d0e622e5724c721a474e1cacd6). > > > I tested all these features on MacOSX and Ubuntu 18. > > I hope this helps, > Thanks in advance for your returns, > > Yonathan > > > _______________________________________________ > openssh-unix-dev mailing list > openssh-unix-dev@xxxxxxxxxxx > https://lists.mindrot.org/mailman/listinfo/openssh-unix-dev > _______________________________________________ openssh-unix-dev mailing list openssh-unix-dev@xxxxxxxxxxx https://lists.mindrot.org/mailman/listinfo/openssh-unix-dev
