openssh unix dev - Feb 2013 - getpgrp

These days, sshd.c has:

static void
grace_alarm_handler(int sig)
{
...
        if (getpgid(0) == getpid()) {
                signal(SIGTERM, SIG_IGN);
                killpg(0, SIGTERM);
        }

        sigdie(...);
}

however (really) old BSDs do not have getpgid().  They do have
getpgrp(), which does what we want here. The question is what to do if
we have neither: return the pid (and thus terminate nothing) or return
-1 and kill everything wihout getting to the sigdie().  I vote for the
latter (since they're unlikely to be able to log anything in a
signal-safe manner anyway).

Index: configure.ac
==================================================================RCS file:
/var/cvs/openssh/configure.ac,v
retrieving revision 1.503
diff -u -p -r1.503 configure.ac
--- configure.ac	10 Feb 2013 23:39:13 -0000	1.503
+++ configure.ac	15 Feb 2013 00:26:37 -0000
@@ -1550,6 +1550,8 @@ AC_CHECK_FUNCS([ \
 	getopt \
 	getpeereid \
 	getpeerucred \
+	getpgid \
+	getpgrp \
 	_getpty \
 	getrlimit \
 	getttyent \
Index: openbsd-compat/bsd-misc.c
==================================================================RCS file:
/var/cvs/openssh/openbsd-compat/bsd-misc.c,v
retrieving revision 1.36
diff -u -p -r1.36 bsd-misc.c
--- openbsd-compat/bsd-misc.c	8 Nov 2010 22:26:23 -0000	1.36
+++ openbsd-compat/bsd-misc.c	15 Feb 2013 00:26:37 -0000
@@ -246,4 +246,18 @@ int isblank(int c)
 {
 	return (c == ' ' || c == '\t');
 }
+
+#ifndef HAVE_GETPGID
+pid_t
+getpgid(pid_t pid)
+{
+#ifdef HAVE_GETPGRP
+	if (pid == 0)
+		return getpgrp();
+#endif
+	errno = ESRCH;
+	return -1;
+}
+#endif
+
 #endif
Index: openbsd-compat/bsd-misc.h
==================================================================RCS file:
/var/cvs/openssh/openbsd-compat/bsd-misc.h,v
retrieving revision 1.21
diff -u -p -r1.21 bsd-misc.h
--- openbsd-compat/bsd-misc.h	3 Jul 2012 22:50:10 -0000	1.21
+++ openbsd-compat/bsd-misc.h	15 Feb 2013 00:26:37 -0000
@@ -102,4 +102,8 @@ mysig_t mysignal(int sig, mysig_t act);
 int	isblank(int);
 #endif
 
+#ifndef HAVE_GETPGID
+pid_t getpgid(pid_t);
+#endif
+
 #endif /* _BSD_MISC_H */
-- 
Darren Tucker (dtucker at zip.com.au)
GPG key 8FF4FA69 / D9A3 86E9 7EEE AF4B B2D4  37C9 C982 80C7 8FF4 FA69
    Good judgement comes with experience. Unfortunately, the experience
usually comes from bad judgement.

On Fri, 15 Feb 2013, Darren Tucker wrote:
> These days, sshd.c has:
> 
> static void
> grace_alarm_handler(int sig)
> {
> ...
>         if (getpgid(0) == getpid()) {
>                 signal(SIGTERM, SIG_IGN);
>                 killpg(0, SIGTERM);
>         }
> 
>         sigdie(...);
> }
> 
> however (really) old BSDs do not have getpgid().  They do have
> getpgrp(), which does what we want here. The question is what to do if
> we have neither: return the pid (and thus terminate nothing) or return
> -1 and kill everything wihout getting to the sigdie().  I vote for the
> latter (since they're unlikely to be able to log anything in a
> signal-safe manner anyway).
Is killpg(-1, ...) defined to do anything? According to SUSv3, pgrp<=1
is undefined. Do you mean pgrp=0?

The condition I worry about is terminating the listening sshd by accident.
Maybe it would be best to disable AuthorizedKeysCommand on these hosts,
since it was the motivation for the killpg IIRC.

-d

On Fri, 15 Feb 2013, Darren Tucker wrote:
> +#ifndef HAVE_GETPGID
> +pid_t
> +getpgid(pid_t pid)
> +{
> +#ifdef HAVE_GETPGRP
> +	if (pid == 0)
> +		return getpgrp();
> +#endif
getpgrp() takes an argument on BSDs. AC_FUNC_GETPGRP tests for this:

http://www.gnu.org/software/autoconf/manual/autoconf-2.60/html_node/Particular-Functions.html#index-AC_005fFUNC_005fGETPGRP-376

-d