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#define _XOPEN_SOURCE
#include <pwd.h>
#include <shadow.h>
#include <stdbool.h>
#include <sys/types.h>
#include <unistd.h>
#include <wlr/util/log.h>
#include "swaylock/swaylock.h"
#ifdef __GLIBC__
// GNU, you damn slimy bastard
#include <crypt.h>
#endif
static int comm[2][2];
static void clear_buffer(void *buf, size_t bytes) {
volatile char *buffer = buf;
volatile char zero = '\0';
for (size_t i = 0; i < bytes; ++i) {
buffer[i] = zero;
}
}
void run_child(void) {
/* This code runs as root */
struct passwd *pwent = getpwuid(getuid());
if (!pwent) {
wlr_log_errno(WLR_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) {
wlr_log_errno(WLR_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);
}
/* This code does not run as root */
wlr_log(WLR_DEBUG, "prepared to authorize user %s", pwent->pw_name);
size_t size;
char *buf;
while (1) {
ssize_t amt;
amt = read(comm[0][0], &size, sizeof(size));
if (amt == 0) {
break;
} else if (amt < 0) {
wlr_log_errno(WLR_ERROR, "read pw request");
}
wlr_log(WLR_DEBUG, "received pw check request");
buf = malloc(size);
if (!buf) {
wlr_log_errno(WLR_ERROR, "failed to malloc pw buffer");
exit(EXIT_FAILURE);
}
size_t offs = 0;
do {
amt = read(comm[0][0], &buf[offs], size - offs);
if (amt <= 0) {
wlr_log_errno(WLR_ERROR, "failed to read pw");
exit(EXIT_FAILURE);
}
offs += (size_t)amt;
} while (offs < size);
bool result = false;
char *c = crypt(buf, encpw);
if (c == NULL) {
wlr_log_errno(WLR_ERROR, "crypt");
}
result = strcmp(c, encpw) == 0;
if (write(comm[1][1], &result, sizeof(result)) != sizeof(result)) {
wlr_log_errno(WLR_ERROR, "failed to write pw check result");
clear_buffer(buf, size);
exit(EXIT_FAILURE);
}
clear_buffer(buf, size);
free(buf);
}
clear_buffer(encpw, strlen(encpw));
exit(EXIT_SUCCESS);
}
void initialize_pw_backend(void) {
if (geteuid() != 0) {
wlr_log(WLR_ERROR, "swaylock needs to be setuid to read /etc/shadow");
exit(EXIT_FAILURE);
}
if (pipe(comm[0]) != 0) {
wlr_log_errno(WLR_ERROR, "failed to create pipe");
exit(EXIT_FAILURE);
}
if (pipe(comm[1]) != 0) {
wlr_log_errno(WLR_ERROR, "failed to create pipe");
exit(EXIT_FAILURE);
}
pid_t child = fork();
if (child == 0) {
close(comm[0][1]);
close(comm[1][0]);
run_child();
} else if (child < 0) {
wlr_log_errno(WLR_ERROR, "failed to fork");
exit(EXIT_FAILURE);
}
close(comm[0][0]);
close(comm[1][1]);
if (setgid(getgid()) != 0) {
wlr_log_errno(WLR_ERROR, "Unable to drop root");
exit(EXIT_FAILURE);
}
if (setuid(getuid()) != 0) {
wlr_log_errno(WLR_ERROR, "Unable to drop root");
exit(EXIT_FAILURE);
}
}
bool attempt_password(struct swaylock_password *pw) {
bool result = false;
size_t len = pw->len + 1;
size_t offs = 0;
if (write(comm[0][1], &len, sizeof(len)) < 0) {
wlr_log_errno(WLR_ERROR, "Failed to request pw check");
goto ret;
}
do {
ssize_t amt = write(comm[0][1], &pw->buffer[offs], len - offs);
if (amt < 0) {
wlr_log_errno(WLR_ERROR, "Failed to write pw buffer");
goto ret;
}
offs += amt;
} while (offs < len);
if (read(comm[1][0], &result, sizeof(result)) != sizeof(result)) {
wlr_log_errno(WLR_ERROR, "Failed to read pw result");
goto ret;
}
wlr_log(WLR_DEBUG, "pw result: %d", result);
ret:
clear_password_buffer(pw);
return result;
}
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