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wall: access FILE under real user's credentials

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While at it, move applet/config/kbuild bits into wall.c.
(This way, it's more visible that applet is suid'ed).

function                                             old     new   delta
wall_main                                             87     138     +51

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
This commit is contained in:
Denys Vlasenko
2013-10-06 15:14:25 +02:00
parent 3eab2b7675
commit cd256e1c40
4 changed files with 24 additions and 11 deletions
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25
miscutils/wall.c
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@ -6,6 +6,18 @@
* Licensed under GPLv2 or later, see file LICENSE in this source tree.
*/
//config:config WALL
//config: bool "wall"
//config: default y
//config: depends on FEATURE_UTMP
//config: help
//config: Write a message to all users that are logged in.
/* Needs to be run by root or be suid root - needs to write to /dev/TTY: */
//applet:IF_WALL(APPLET(wall, BB_DIR_USR_BIN, BB_SUID_REQUIRE))
//kbuild:lib-$(CONFIG_WALL) += wall.o
//usage:#define wall_trivial_usage
//usage: "[FILE]"
//usage:#define wall_full_usage "\n\n"
@ -22,8 +34,19 @@ int wall_main(int argc UNUSED_PARAM, char **argv)
{
struct utmp *ut;
char *msg;
int fd = argv[1] ? xopen(argv[1], O_RDONLY) : STDIN_FILENO;
int fd;
fd = STDIN_FILENO;
if (argv[1]) {
/* The applet is setuid.
* Access to the file must be under user's uid/gid.
*/
setfsuid(getuid());
setfsgid(getgid());
fd = xopen(argv[1], O_RDONLY);
setfsuid(geteuid());
setfsgid(getegid());
}
msg = xmalloc_read(fd, NULL);
if (ENABLE_FEATURE_CLEAN_UP && argv[1])
close(fd);