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Read password hash before fork

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This ensures that the parent properly errors only if the password
cannot be read.
This commit is contained in:
Sertonix 2024-01-16 12:25:01 +01:00 committed by Simon Ser
parent 376cc5fcd4
commit f9ce3f193b
1 changed files with 26 additions and 36 deletions
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62
shadow.c
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@ -1,4 +1,5 @@
#define _XOPEN_SOURCE // for crypt #define _XOPEN_SOURCE // for crypt
#include <assert.h>
#include <pwd.h> #include <pwd.h>
#include <shadow.h> #include <shadow.h>
#include <stdlib.h> #include <stdlib.h>
@ -14,15 +15,23 @@
#include "password-buffer.h" #include "password-buffer.h"
#include "swaylock.h" #include "swaylock.h"
char *encpw = NULL;
void initialize_pw_backend(int argc, char **argv) { void initialize_pw_backend(int argc, char **argv) {
if (geteuid() != 0) { /* This code runs as root */
swaylock_log(LOG_ERROR, struct passwd *pwent = getpwuid(getuid());
"swaylock needs to be setuid to read /etc/shadow"); if (!pwent) {
swaylock_log_errno(LOG_ERROR, "failed to getpwuid");
exit(EXIT_FAILURE); exit(EXIT_FAILURE);
} }
encpw = pwent->pw_passwd;
if (!spawn_comm_child()) { if (strcmp(encpw, "x") == 0) {
exit(EXIT_FAILURE); struct spwd *swent = getspnam(pwent->pw_name);
if (!swent) {
swaylock_log_errno(LOG_ERROR, "failed to getspnam");
exit(EXIT_FAILURE);
}
encpw = swent->sp_pwdp;
} }
if (setgid(getgid()) != 0) { if (setgid(getgid()) != 0) {
@ -38,40 +47,21 @@ void initialize_pw_backend(int argc, char **argv) {
"able to restore it after setuid/setgid)"); "able to restore it after setuid/setgid)");
exit(EXIT_FAILURE); exit(EXIT_FAILURE);
} }
}
void run_pw_backend_child(void) {
/* This code runs as root */
struct passwd *pwent = getpwuid(getuid());
if (!pwent) {
swaylock_log_errno(LOG_ERROR, "failed to getpwuid");
exit(EXIT_FAILURE);
}
char *encpw = pwent->pw_passwd;
if (strcmp(encpw, "x") == 0) {
struct spwd *swent = getspnam(pwent->pw_name);
if (!swent) {
swaylock_log_errno(LOG_ERROR, "failed to getspnam");
exit(EXIT_FAILURE);
}
encpw = swent->sp_pwdp;
}
/* We don't need any additional logging here because the parent process will
* also fail here and will handle logging for us. */
if (setgid(getgid()) != 0) {
exit(EXIT_FAILURE);
}
if (setuid(getuid()) != 0) {
exit(EXIT_FAILURE);
}
if (setuid(0) != -1) {
exit(EXIT_FAILURE);
}
/* This code does not run as root */ /* This code does not run as root */
swaylock_log(LOG_DEBUG, "Prepared to authorize user %s", pwent->pw_name); swaylock_log(LOG_DEBUG, "Prepared to authorize user %s", pwent->pw_name);
if (!spawn_comm_child()) {
exit(EXIT_FAILURE);
}
/* Buffer is only used by the child */
clear_buffer(encpw, strlen(encpw));
encpw = NULL;
}
void run_pw_backend_child(void) {
assert(encpw != NULL);
while (1) { while (1) {
char *buf; char *buf;
ssize_t size = read_comm_request(&buf); ssize_t size = read_comm_request(&buf);