Enabled when coreutils is configured with --with-tty-group.
Based on a patch written by Piotr Gackiewicz. Details at
http://bugzilla.redhat.com/454261
* src/who.c (is_tty_writable): A new function returning true if a TTY
device is writable by the group. Additionally it checks the group to be
the same as TTY_GROUP_NAME when compiled with --with-tty-group.
* m4/jm-macros.m4: Introduce a new configure option --with-tty-group.
* NEWS: Mention the change.
* Noteworthy changes in release ?.? (????-??-??) [?]
+** New features
+
+ who: the "+/-" --mesg (-T) indicator of whether a user/tty is accepting
+ messages could be incorrectly listed as "+", when in fact, the user was
+ not accepting messages (mesg no). Before, who would examine only the
+ permission bits, and not consider the group of the TTY device file.
+ Thus, if a login tty's group would change somehow e.g., to "root",
+ that would make it unwritable (via write(1)) by normal users, in spite
+ of whatever the permission bits might imply. Now, when configured
+ using the --with-tty-group[=NAME] option, who also compares the group
+ of the TTY device with NAME (or "tty" if no group name is specified).
+
* Noteworthy changes in release 8.4 (2010-01-13) [stable]
Phillip Jones mouse@datastacks.com
Piergiorgio Sartor sartor@sony.de
Pieter Bowman bowman@math.utah.edu
+Piotr Gackiewicz gacek@intertele.pl
Piotr Kwapulinski kwap@univ.gda.pl
Prashant TR tr@eth.net
Priit Jõerüüt jemm4jemm@yahoo.com
])
AC_REQUIRE([AM_LANGINFO_CODESET])
+
+ # Accept configure options: --with-tty-group[=GROUP], --without-tty-group
+ # You can determine the group of a TTY via 'stat --format %G /dev/tty'
+ # Omitting this option is equivalent to using --without-tty-group.
+ AC_ARG_WITH([tty-group],
+ AS_HELP_STRING([--with-tty-group[[[=NAME]]]],
+ [group used by system for TTYs, "tty" when not specified]
+ [ (default: do not rely on any group used for TTYs)]),
+ [tty_group_name=$withval],
+ [tty_group_name=no])
+
+ if test "x$tty_group_name" != xno; then
+ if test "x$tty_group_name" = xyes; then
+ tty_group_name=tty
+ fi
+ AC_MSG_NOTICE([TTY group used by system set to "$tty_group_name"])
+ AC_DEFINE_UNQUOTED([TTY_GROUP_NAME], ["$tty_group_name"],
+ [group used by system for TTYs])
+ fi
])
AC_DEFUN([gl_CHECK_ALL_HEADERS],
#include "hard-locale.h"
#include "quote.h"
+#ifdef TTY_GROUP_NAME
+# include <grp.h>
+#endif
+
/* The official name of this program (e.g., no `g' prefix). */
#define PROGRAM_NAME "who"
free (x_exitstr);
}
+/* Return true if a terminal device given as PSTAT allows other users
+ to send messages to; false otherwise */
+static bool
+is_tty_writable (struct stat const *pstat)
+{
+#ifdef TTY_GROUP_NAME
+ /* Ensure the group of the TTY device matches TTY_GROUP_NAME, more info at
+ https://bugzilla.redhat.com/454261 */
+ struct group *ttygr = getgrnam (TTY_GROUP_NAME);
+ if (!ttygr || (pstat->st_gid != ttygr->gr_gid))
+ return false;
+#endif
+
+ return pstat->st_mode & S_IWGRP;
+}
+
/* Send properly parsed USER_PROCESS info to print_line. The most
recent boot time is BOOTTIME. */
static void
if (stat (line, &stats) == 0)
{
- mesg = (stats.st_mode & S_IWGRP) ? '+' : '-';
+ mesg = is_tty_writable (&stats) ? '+' : '-';
last_change = stats.st_atime;
}
else