initscripts/src/securetty.c

   1
   2 #include <errno.h>
   3 #include <fcntl.h>
   4 #include <signal.h>
   5 #include <stdio.h>
   6 #include <stdlib.h>
   7 #include <string.h>
   8 #include <syslog.h>
   9 #include <unistd.h>
  10
  11 #include <sys/types.h>
  12 #include <sys/stat.h>
  13
  14 void alarm_handler(int num) {
  15         return;
  16 }
  17
  18 int open_and_lock_securetty() {
  19         int fd;
  20         struct flock lock;
  21         struct sigaction act, oldact;
  22
  23         lock.l_type = F_WRLCK;
  24         lock.l_whence = SEEK_SET;
  25         lock.l_start = 0;
  26         lock.l_len = 0;
  27
  28         fd = open("/etc/securetty", O_RDWR);
  29         if (fd == -1) {
  30                 syslog(LOG_ERR, "Couldn't open /etc/securetty: %s",strerror(errno));
  31                 return -1;
  32         }
  33         act.sa_handler = alarm_handler;
  34         act.sa_flags = 0;
  35         sigaction(SIGALRM, &act, &oldact);
  36         alarm(2);
  37         while (fcntl(fd, F_SETLKW, &lock) == -1) {
  38                 if (errno == EINTR) {
  39                         syslog(LOG_ERR, "Couldn't lock /etc/securetty: Timeout exceeded");
  40                 } else {
  41                         syslog(LOG_ERR, "Couldn't lock /etc/securetty: %s",strerror(errno));
  42                 }
  43                 return -1;
  44         }
  45         alarm(0);
  46         sigaction(SIGALRM, &oldact, NULL);
  47         return fd;
  48 }
  49
  50 int rewrite_securetty(char *terminal) {
  51         int fd;
  52         char *buf, *pos;
  53         struct stat sbuf;
  54
  55         fd = open_and_lock_securetty();
  56         if (fd == -1)
  57                 return 1;
  58         if (fstat(fd, &sbuf) == -1) {
  59                 close(fd);
  60                 syslog(LOG_ERR, "Couldn't stat /etc/securetty: %s",strerror(errno));
  61                 return 1;
  62         }
  63         buf = malloc(sbuf.st_size + 1);
  64         if (read(fd, buf, sbuf.st_size) != sbuf.st_size) {
  65                 close(fd);
  66                 syslog(LOG_ERR, "Couldn't read /etc/securetty: %s",strerror(errno));
  67                 return 1;
  68         }
  69         if (!strncmp(buf,terminal,strlen(terminal)) && buf[strlen(terminal)] == '\n')
  70                 goto out_ok;
  71         if ((pos = strstr(buf, terminal))) {
  72                 if (pos[strlen(terminal)] == '\n' && *(pos-1) == '\n')
  73                         goto out_ok;
  74         }
  75         if (lseek(fd, 0, SEEK_END) == -1) {
  76                 close(fd);
  77                 syslog(LOG_ERR, "Couldn't seek to end of /etc/securetty: %s",strerror(errno));
  78                 return 1;
  79         }
  80         write(fd, terminal, strlen(terminal));
  81         write(fd, "\n", 1);
  82 out_ok:
  83         close(fd);
  84         return 0;
  85 }
  86
  87 int main(int argc, char **argv) {
  88         if (argc < 2 ) {
  89                 fprintf(stderr, "Usage: securetty <device>\n");
  90                 exit(1);
  91         }
  92         openlog("securetty", LOG_CONS, LOG_DAEMON);
  93         return rewrite_securetty(argv[1]);
  94 }