Add ssh_config equivalents of -N, -s, -n and -f #231

vog · 2021-02-26T00:37:38Z

Dear OpenSSH developers,

I kindly ask you to review the attached set of patches which introduce ssh_config equivalents of the flags -N, -s, -n and -f in a straight forward way:

~~NoShell for -N~~
SessionType for -N and -s
StdinNull for -n
ForkAfterAuthentication for -f

The ssh_config names are corresponding directly to the internal flag names. The man pages ssh(1) and ssh_config(5) are adjusted accordingly.

As a final remark, I noticed that the variable ono_shell_flag (not to be confused with no_shell_flag) is only assigned once and never used. So I assume this is dead code and I'm proposing a patch to remove it.
(Update: ono_shell_flag was actually meant to be used, see 5953c14)

Related mailing list threads:

[PATCH] Add ssh_config option ExecRemoteCommand which is equivalent to -N (original proposal from 2016)
Option equivalent to -n in client? (another user asking for a similar improvement in 2021)
[PATCH] Add ssh_config equivalents of -N, -n and -f (new proposed patches in 2021)

Best regards,
Volker

@vog

openssh#231 openssh@6c6813f openssh@de28eef openssh@aac32c9 openssh@0f7dd4d https://marc.info/?l=openssh-unix-dev&m=147248154926769 https://marc.info/?l=openssh-unix-dev&m=161301825023655 https://marc.info/?l=openssh-unix-dev&m=161387765919633 Description (from @vog): Dear OpenSSH developers, I kindly ask you to review the attached set of patches which introduce ssh_config equivalents of the flags -N, -n and -f in a straight-forward way: NoShell for -N StdinNull for -n ForkAfterAuthentication for -f The ssh_config names were derived directly from the internal flag names, e.g. no_shell_flag was moved to option.no_shell and hence the ssh_config name became NoShell. The man pages ssh(1) and ssh_config(5) are adjusted accordingly. As a final remark, I noticed that the variable ono_shell_flag (not to be confused with no_shell_flag) is only assigned once and never used. So I assume this is dead code and I'm proposing a patch to remove it.

vog · 2021-03-09T00:04:30Z

Rebased to latest master.

vog · 2021-03-17T23:14:15Z

Rebased again to latest master.

vog · 2021-03-25T09:12:07Z

Rebased again to latest master.

vog · 2021-05-04T08:00:41Z

Rebased yet another time to latest master.

vog · 2021-06-10T15:35:28Z

Rebased to latest master, removing the commit that removed ono_shell_flag, as this variable is no longer unused (see 5953c14)

vog · 2021-06-10T15:44:28Z

Feedback from Damien Miller via mailing list:

I think SessionType=none/subsystem/default is the way to go. I'll
have some time to look at it next week, but if you want to implement
it then please don't let me stop you :)

Thanks again for your patience.

-d

vog · 2021-06-10T16:34:54Z

Implemented SessionType instead of NoShell. That way, we also have an ssh_option that is equivalent to -s.

candlerb · 2021-07-06T08:02:48Z

mux.c

@@ -71,7 +71,6 @@
 /* from ssh.c */
 extern int tty_flag;
 extern Options options;
-extern int stdin_null_flag;
 extern char *host;
 extern int subsystem_flag;


Should extern int subsystem_flag be removed too?

Of course! Fixed.

candlerb · 2021-07-06T08:10:58Z

ssh_config.5

+is run in the background.
+A common trick is to use this to run X11 programs on a remote machine.
+For example,
+.Ic ssh shadows.cs.hut.fi emacs &


Should this say ssh -n ...? Or ssh -o StdinNull=yes ...?

Otherwise, you've silently assumed the reader has put this option in ~/.ssh/config for Host shadows.cs.hut.fi (but they may not wish to do so for every session to that host)

I took that example from the ssh.1 manpage where "ssh -n" is described.

I agree that it doesn't fit well here.

I'm just leaving this out of ssh_config.5, the description is perfectly fine without it.

candlerb · 2021-07-06T08:13:42Z

ssh_config.5

@@ -683,6 +683,45 @@ Valid options are:
 and
 .Cm sha256
 (the default).
+.It Cm ForkAfterAuthentication


Should these new options also be listed in ssh.1 under -o option?

Indeed! I missed that place in the manpages. Fixed.

vog · 2021-07-06T09:48:44Z

Thanks for the feedback! I'll have a look at it this evening.

…nd -s Also, combine the internal flags "no_shell_flag" and "subsystem_flag" into a single enum "session_type".

vog · 2021-07-06T20:08:05Z

I just improved the pull request by rebasing it to the latest master and applying all feedback received via mailing list and in this GitHub issue so far.

djmdjm · 2021-07-09T04:15:57Z

FYI these patches are all out for review upstream

vog · 2021-07-09T06:05:52Z

Thanks!

djmdjm · 2021-07-13T23:50:24Z

SessionType merged as eda8909

vog · 2021-07-21T15:09:25Z

@djmdjm Thanks for the notification! What is the status of the other 2 commits? Should I rebase them, or anything?

djmdjm · 2021-07-23T04:08:31Z

All committed now (as a917e97 and e0c5088) - thanks for your patience!

vog force-pushed the ssh-config-improvements branch from 6c6813f to 792101d Compare March 9, 2021 00:03

vog force-pushed the ssh-config-improvements branch from 792101d to 45a7907 Compare March 17, 2021 23:12

vog force-pushed the ssh-config-improvements branch from 45a7907 to 8cf12df Compare March 25, 2021 04:10

vog force-pushed the ssh-config-improvements branch from 8cf12df to c8d5494 Compare April 10, 2021 11:48

vog force-pushed the ssh-config-improvements branch from c8d5494 to a20217b Compare May 4, 2021 07:56

vog force-pushed the ssh-config-improvements branch from a20217b to b50aeb2 Compare June 10, 2021 15:30

vog force-pushed the ssh-config-improvements branch from b50aeb2 to b9e0e25 Compare June 10, 2021 16:34

vog changed the title ~~Add ssh_config equivalents of -N, -n and -f~~ Add ssh_config equivalents of -N, -s, -n and -f Jun 10, 2021

candlerb reviewed Jul 6, 2021

View reviewed changes

vog added 3 commits July 6, 2021 22:04

Add ssh_config option SessionType which combines the behavior of -N a…

559ad9c

…nd -s Also, combine the internal flags "no_shell_flag" and "subsystem_flag" into a single enum "session_type".

Add ssh_config option StdinNull with same behavior as -n

388a797

Add ssh_config option ForkAfterAuthentication with same behavior as -f

8f31723

vog force-pushed the ssh-config-improvements branch from b9e0e25 to 8f31723 Compare July 6, 2021 20:04

djmdjm closed this Jul 23, 2021

johnjohndoe mentioned this pull request Nov 2, 2021

Add BHNT79 hacks berlin-hack-and-tell/bhnt.c-base.org#302

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Add ssh_config equivalents of -N, -s, -n and -f #231

Add ssh_config equivalents of -N, -s, -n and -f #231

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Add ssh_config equivalents of -N, -s, -n and -f #231

Add ssh_config equivalents of -N, -s, -n and -f #231

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