suid executable not elevating permissions but `sudo` does elevate
I'm trying to write a program that will quickly shut down a laptop without prompting for a password or confirmation. The laptop is running Linux, specifically Manjaro.
To that end, I'm trying to make a setuid executable called downnow that executes shutdown with fixed arguments (and also spawns a shell).
// downnow.c
#include <stdlib.h>
int main() {
system("shutdown --no-wall --halt now");
return 0;
}
then I compiled downnow, moved it to /bin, changed its owner and gave it setuid and setgid permissions:
$ sudo chown root /bin/downnow
$ sudo chgrp root /bin/downnow
$ sudo chmod u+s /bin/downnow
$ sudo chmod g+s /bin/downnow
However, when I attempt to execute downnow as an unprivileged user, it can't communicate with systemd.
$ downnow
Failed to halt system via logind: Interactive authentication required.
Failed to talk to init daemon.
I get the same message before and after ch{own,grp,mod}ing.
stat reports the same permissions on /bin/downnow and /usr/bin/sudo.
$ stat /bin/downnow
File: /bin/downnow
Size: XXXX Blocks: XX IO Block: XXXX regular file
Device: XXXXX/XXXXX Inode: XXXXXX Links: 1
Access: (6755/-rwsr-sr-x) Uid: ( 0/ root) Gid: ( 0/ root)
$ stat /usr/bin/sudo
File: /usr/bin/sudo
Size: XXXXXX Blocks: XXX IO Block: XXXX regular file
Device: XXXXX/XXXXX Inode: XXXXXXX Links: 1
Access: (4755/-rwsr-xr-x) Uid: ( 0/ root) Gid: ( 0/ root)
Why might downnow fail to elevate its privileges when sudo works perfectly?
setuid
asked 29 mins ago
Gregory NisbetGregory Nisbet
1,3771020
add a comment |
I'm trying to write a program that will quickly shut down a laptop without prompting for a password or confirmation. The laptop is running Linux, specifically Manjaro.
To that end, I'm trying to make a setuid executable called downnow that executes shutdown with fixed arguments (and also spawns a shell).
// downnow.c
#include <stdlib.h>
int main() {
system("shutdown --no-wall --halt now");
return 0;
}
then I compiled downnow, moved it to /bin, changed its owner and gave it setuid and setgid permissions:
$ sudo chown root /bin/downnow
$ sudo chgrp root /bin/downnow
$ sudo chmod u+s /bin/downnow
$ sudo chmod g+s /bin/downnow
However, when I attempt to execute downnow as an unprivileged user, it can't communicate with systemd.
$ downnow
Failed to halt system via logind: Interactive authentication required.
Failed to talk to init daemon.
I get the same message before and after ch{own,grp,mod}ing.
stat reports the same permissions on /bin/downnow and /usr/bin/sudo.
$ stat /bin/downnow
File: /bin/downnow
Size: XXXX Blocks: XX IO Block: XXXX regular file
Device: XXXXX/XXXXX Inode: XXXXXX Links: 1
Access: (6755/-rwsr-sr-x) Uid: ( 0/ root) Gid: ( 0/ root)
$ stat /usr/bin/sudo
File: /usr/bin/sudo
Size: XXXXXX Blocks: XXX IO Block: XXXX regular file
Device: XXXXX/XXXXX Inode: XXXXXXX Links: 1
Access: (4755/-rwsr-xr-x) Uid: ( 0/ root) Gid: ( 0/ root)
Why might downnow fail to elevate its privileges when sudo works perfectly?
setuid
asked 29 mins ago
Gregory NisbetGregory Nisbet
1,3771020
add a comment |
I'm trying to write a program that will quickly shut down a laptop without prompting for a password or confirmation. The laptop is running Linux, specifically Manjaro.
To that end, I'm trying to make a setuid executable called downnow that executes shutdown with fixed arguments (and also spawns a shell).
// downnow.c
#include <stdlib.h>
int main() {
system("shutdown --no-wall --halt now");
return 0;
}
then I compiled downnow, moved it to /bin, changed its owner and gave it setuid and setgid permissions:
$ sudo chown root /bin/downnow
$ sudo chgrp root /bin/downnow
$ sudo chmod u+s /bin/downnow
$ sudo chmod g+s /bin/downnow
However, when I attempt to execute downnow as an unprivileged user, it can't communicate with systemd.
$ downnow
Failed to halt system via logind: Interactive authentication required.
Failed to talk to init daemon.
I get the same message before and after ch{own,grp,mod}ing.
stat reports the same permissions on /bin/downnow and /usr/bin/sudo.
$ stat /bin/downnow
File: /bin/downnow
Size: XXXX Blocks: XX IO Block: XXXX regular file
Device: XXXXX/XXXXX Inode: XXXXXX Links: 1
Access: (6755/-rwsr-sr-x) Uid: ( 0/ root) Gid: ( 0/ root)
$ stat /usr/bin/sudo
File: /usr/bin/sudo
Size: XXXXXX Blocks: XXX IO Block: XXXX regular file
Device: XXXXX/XXXXX Inode: XXXXXXX Links: 1
Access: (4755/-rwsr-xr-x) Uid: ( 0/ root) Gid: ( 0/ root)
Why might downnow fail to elevate its privileges when sudo works perfectly?
setuid
asked 29 mins ago
Gregory NisbetGregory Nisbet
1,3771020
I'm trying to write a program that will quickly shut down a laptop without prompting for a password or confirmation. The laptop is running Linux, specifically Manjaro.
To that end, I'm trying to make a setuid executable called downnow that executes shutdown with fixed arguments (and also spawns a shell).
// downnow.c
#include <stdlib.h>
int main() {
system("shutdown --no-wall --halt now");
return 0;
}
then I compiled downnow, moved it to /bin, changed its owner and gave it setuid and setgid permissions:
$ sudo chown root /bin/downnow
$ sudo chgrp root /bin/downnow
$ sudo chmod u+s /bin/downnow
$ sudo chmod g+s /bin/downnow
However, when I attempt to execute downnow as an unprivileged user, it can't communicate with systemd.
$ downnow
Failed to halt system via logind: Interactive authentication required.
Failed to talk to init daemon.
I get the same message before and after ch{own,grp,mod}ing.
stat reports the same permissions on /bin/downnow and /usr/bin/sudo.
$ stat /bin/downnow
File: /bin/downnow
Size: XXXX Blocks: XX IO Block: XXXX regular file
Device: XXXXX/XXXXX Inode: XXXXXX Links: 1
Access: (6755/-rwsr-sr-x) Uid: ( 0/ root) Gid: ( 0/ root)
$ stat /usr/bin/sudo
File: /usr/bin/sudo
Size: XXXXXX Blocks: XXX IO Block: XXXX regular file
Device: XXXXX/XXXXX Inode: XXXXXXX Links: 1
Access: (4755/-rwsr-xr-x) Uid: ( 0/ root) Gid: ( 0/ root)
Why might downnow fail to elevate its privileges when sudo works perfectly?
setuid
setuid
asked 29 mins ago
Gregory NisbetGregory Nisbet
1,3771020
asked 29 mins ago
Gregory NisbetGregory Nisbet
1,3771020
asked 29 mins ago
Gregory NisbetGregory Nisbet
1,3771020
asked 29 mins ago
Gregory NisbetGregory Nisbet
1,3771020
asked 29 mins ago
Gregory NisbetGregory Nisbet
1,3771020
1,3771020
add a comment |
add a comment |
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