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#include <errno.h>
#include <fcntl.h>
#include <signal.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <syslog.h>
#include <unistd.h>
#include <sys/types.h>
#include <sys/stat.h>
void alarm_handler(int num) {
return;
}
int open_and_lock_securetty() {
int fd;
struct flock lock;
struct sigaction act, oldact;
lock.l_type = F_WRLCK;
lock.l_whence = SEEK_SET;
lock.l_start = 0;
lock.l_len = 0;
fd = open("/etc/securetty", O_RDWR);
if (fd == -1) {
syslog(LOG_ERR, "Couldn't open /etc/securetty: %s",strerror(errno));
return -1;
}
act.sa_handler = alarm_handler;
act.sa_flags = 0;
sigaction(SIGALRM, &act, &oldact);
alarm(2);
while (fcntl(fd, F_SETLKW, &lock) == -1) {
if (errno == EINTR) {
syslog(LOG_ERR, "Couldn't lock /etc/securetty: Timeout exceeded");
} else {
syslog(LOG_ERR, "Couldn't lock /etc/securetty: %s",strerror(errno));
}
return -1;
}
alarm(0);
sigaction(SIGALRM, &oldact, NULL);
return fd;
}
int rewrite_securetty(char *terminal) {
int fd;
char *buf, *pos;
struct stat sbuf;
fd = open_and_lock_securetty();
if (fd == -1)
return 1;
if (fstat(fd, &sbuf) == -1) {
close(fd);
syslog(LOG_ERR, "Couldn't stat /etc/securetty: %s",strerror(errno));
return 1;
}
buf = malloc(sbuf.st_size + 1);
if (read(fd, buf, sbuf.st_size) != sbuf.st_size) {
close(fd);
syslog(LOG_ERR, "Couldn't read /etc/securetty: %s",strerror(errno));
return 1;
}
if (!strncmp(buf,terminal,strlen(terminal)) && buf[strlen(terminal)] == '\n')
goto out_ok;
if ((pos = strstr(buf, terminal))) {
if (pos[strlen(terminal)] == '\n' && *(pos-1) == '\n')
goto out_ok;
}
if (lseek(fd, 0, SEEK_END) == -1) {
close(fd);
syslog(LOG_ERR, "Couldn't seek to end of /etc/securetty: %s",strerror(errno));
return 1;
}
write(fd, terminal, strlen(terminal));
write(fd, "\n", 1);
out_ok:
close(fd);
return 0;
}
int main(int argc, char **argv) {
if (argc < 2 ) {
fprintf(stderr, "Usage: securetty <device>\n");
exit(1);
}
openlog("securetty", LOG_CONS, LOG_DAEMON);
return rewrite_securetty(argv[1]);
}
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