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seatd-launch: Set socket permissions directly

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Instead of relying on seatd's user/group arguments, which require
turning our UID back into a username, just chmod/chown the socket
ourselves once seatd is ready.

We also reduce the permissions to just user access, instead of user and
group like seatd specifies.
This commit is contained in:
Kenny Levinsen 2021-09-08 20:40:09 +02:00
parent 60c370d4ec
commit 17cdbe0ad2
1 changed files with 26 additions and 20 deletions
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46
seatd-launch/seatd-launch.c
View file

@ -1,13 +1,12 @@
#include <errno.h> #include <errno.h>
#include <poll.h> #include <poll.h>
#include <pwd.h>
#include <signal.h> #include <signal.h>
#include <stdbool.h> #include <stdbool.h>
#include <stddef.h> #include <stddef.h>
#include <stdio.h> #include <stdio.h>
#include <stdlib.h> #include <stdlib.h>
#include <string.h> #include <string.h>
#include <sys/types.h> #include <sys/stat.h>
#include <sys/wait.h> #include <sys/wait.h>
#include <unistd.h> #include <unistd.h>
@ -66,29 +65,13 @@ int main(int argc, char *argv[]) {
char pipebuf[8]; char pipebuf[8];
sprintf(pipebuf, "%d", fds[1]); sprintf(pipebuf, "%d", fds[1]);
struct passwd *user = getpwuid(getuid()); execlp("seatd", "seatd", "-n", pipebuf, "-s", sockpath, NULL);
if (!user) {
perror("getpwuid failed");
_exit(1);
}
// TODO: Make seatd accept the numeric UID
execlp("seatd", "seatd", "-n", pipebuf, "-u", user->pw_name, "-s", sockpath, NULL);
perror("Could not start seatd"); perror("Could not start seatd");
_exit(1); _exit(1);
} }
close(fds[1]); close(fds[1]);
// Drop privileges // Wait for seatd to be ready
if (setgid(getgid()) == -1) {
perror("Could not set gid to drop privileges");
goto error_seatd;
}
if (setuid(getuid()) == -1) {
perror("Could not set uid to drop privileges");
goto error_seatd;
}
char buf[1] = {0}; char buf[1] = {0};
while (true) { while (true) {
pid_t p = waitpid(seatd_child, NULL, WNOHANG); pid_t p = waitpid(seatd_child, NULL, WNOHANG);
@ -127,6 +110,29 @@ int main(int argc, char *argv[]) {
} }
close(fds[0]); close(fds[0]);
uid_t uid = getuid();
gid_t gid = getgid();
// Restrict access to the socket to just us
if (chown(sockpath, uid, gid) == -1) {
perror("Could not chown seatd socket");
goto error_seatd;
}
if (chmod(sockpath, 0700) == -1) {
perror("Could not chmod socket");
goto error;
}
// Drop privileges
if (setgid(gid) == -1) {
perror("Could not set gid to drop privileges");
goto error_seatd;
}
if (setuid(uid) == -1) {
perror("Could not set uid to drop privileges");
goto error_seatd;
}
pid_t child = fork(); pid_t child = fork();
if (child == -1) { if (child == -1) {
perror("Could not fork target process"); perror("Could not fork target process");