From beea5a70c34bdcf2b02c37e6f56d2efcbd90fedb Mon Sep 17 00:00:00 2001 From: Denys Vlasenko Date: Tue, 22 Mar 2011 06:54:36 +0100 Subject: [PATCH] mesg: make group/all writability configurable Signed-off-by: Denys Vlasenko --- init/mesg.c | 60 +++++++++++++++++++++++++++++++---------------------- 1 file changed, 35 insertions(+), 25 deletions(-) diff --git a/init/mesg.c b/init/mesg.c index 676ca2e24..8489e621c 100644 --- a/init/mesg.c +++ b/init/mesg.c @@ -7,16 +7,28 @@ * Licensed under GPLv2 or later, see file LICENSE in this source tree. */ -//applet:IF_MESG(APPLET(mesg, BB_DIR_USR_BIN, BB_SUID_DROP)) - -//kbuild:lib-$(CONFIG_MESG) += mesg.o - //config:config MESG //config: bool "mesg" //config: default y //config: help //config: Mesg controls access to your terminal by others. It is typically //config: used to allow or disallow other users to write to your terminal +//config: +//config:config FEATURE_MESG_ENABLE_ONLY_GROUP +//config: bool "Enable writing to tty only by group, not by everybody" +//config: default y +//config: depends on MESG +//config: help +//config: Usually, ttys are owned by group "tty", and "write" tool is +//config: setgid to this group. This way, "mesg y" only needs to enable +//config: "write by owning group" bit in tty mode. +//config: +//config: If you set this option to N, "mesg y" will enable writing +//config: by anybody at all. This is not recommended. + +//applet:IF_MESG(APPLET(mesg, BB_DIR_USR_BIN, BB_SUID_DROP)) + +//kbuild:lib-$(CONFIG_MESG) += mesg.o //usage:#define mesg_trivial_usage //usage: "[y|n]" @@ -27,7 +39,7 @@ #include "libbb.h" -#ifdef USE_TTY_GROUP +#if ENABLE_FEATURE_MESG_ENABLE_ONLY_GROUP #define S_IWGRP_OR_S_IWOTH S_IWGRP #else #define S_IWGRP_OR_S_IWOTH (S_IWGRP | S_IWOTH) @@ -37,30 +49,28 @@ int mesg_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE; int mesg_main(int argc UNUSED_PARAM, char **argv) { struct stat sb; - const char *tty; + mode_t m; char c = 0; argv++; - if (!argv[0] - || (!argv[1] && ((c = argv[0][0]) == 'y' || c == 'n')) + if (argv[0] + && (argv[1] || ((c = argv[0][0]) != 'y' && c != 'n')) ) { - tty = xmalloc_ttyname(STDERR_FILENO); - if (tty == NULL) { - tty = "ttyname"; - } else if (stat(tty, &sb) == 0) { - mode_t m; - if (c == 0) { - puts((sb.st_mode & (S_IWGRP|S_IWOTH)) ? "is y" : "is n"); - return EXIT_SUCCESS; - } - m = (c == 'y') ? sb.st_mode | S_IWGRP_OR_S_IWOTH - : sb.st_mode & ~(S_IWGRP|S_IWOTH); - if (chmod(tty, m) == 0) { - return EXIT_SUCCESS; - } - } - bb_simple_perror_msg_and_die(tty); + bb_show_usage(); + } + + if (!isatty(STDERR_FILENO)) + bb_error_msg_and_die("not a tty"); + + xfstat(STDERR_FILENO, &sb, "stderr"); + if (c == 0) { + puts((sb.st_mode & (S_IWGRP|S_IWOTH)) ? "is y" : "is n"); + return EXIT_SUCCESS; } - bb_show_usage(); + m = (c == 'y') ? sb.st_mode | S_IWGRP_OR_S_IWOTH + : sb.st_mode & ~(S_IWGRP|S_IWOTH); + if (fchmod(STDERR_FILENO, m) != 0) + bb_perror_nomsg_and_die(); + return EXIT_SUCCESS; } -- 2.25.1