commands/telnetd/main.c

   1 /*
   2  * TNET         A server program for MINIX which implements the TCP/IP
   3  *              suite of networking protocols.  It is based on the
   4  *              TCP/IP code written by Phil Karn et al, as found in
   5  *              his NET package for Packet Radio communications.
   6  *
   7  *              This file contains an implementation of the "server"
   8  *              for the TELNET protocol.  This protocol can be used to
   9  *              remote-login on other systems, just like a normal TTY
  10  *              session.
  11  *
  12  * Usage:       telnetd [-dv]
  13  *
  14  * Version:     @(#)telnetd.c   1.00    07/26/92
  15  *
  16  * Author:      Fred N. van Kempen, <waltje@uwalt.nl.mugnet.org>
  17  *              Michael Temari, <temari@temari.ae.ge.com>
  18  */
  19 #include <sys/types.h>
  20 #include <fcntl.h>
  21 #include <sys/wait.h>
  22 #include <sys/ioctl.h>
  23 #include <sys/stat.h>
  24 #include <errno.h>
  25 #include <stdlib.h>
  26 #include <string.h>
  27 #include <unistd.h>
  28 #include <time.h>
  29 #include <stdio.h>
  30 #include <ttyent.h>
  31 #include <utmp.h>
  32 #include <net/gen/in.h>
  33 #include <net/gen/tcp.h>
  34 #include <net/gen/tcp_io.h>
  35 #include <net/gen/socket.h>
  36 #include <net/gen/netdb.h>
  37 #include <net/gen/inet.h>
  38 #include "telnetd.h"
  39
  40 static char *Version = "@(#) telnetd 1.00 (07/26/92)";
  41
  42 int opt_d = 0;                          /* debugging output flag        */
  43
  44 _PROTOTYPE(void usage, (void));
  45 _PROTOTYPE(int main, (int argc, char *argv[]));
  46 _PROTOTYPE(void wtmp, (int type, int linenr, char *line, pid_t pid,
  47                                                                 char *host));
  48
  49 void usage()
  50 {
  51    fprintf(stderr, "Usage: telnetd [-dv]\n");
  52
  53    exit(-1);
  54 }
  55
  56 int main(argc, argv)
  57 int argc;
  58 char *argv[];
  59 {
  60 char buff[128];
  61 register int c;
  62 int pty_fd;
  63 int tty_fd;
  64 pid_t pid;
  65 int lineno;
  66 char *tty_name;
  67 struct ttyent *ttyp;
  68 nwio_tcpconf_t tcpconf;
  69 struct hostent *hostent;
  70 char *hostname;
  71
  72    opterr = 0;
  73    while ((c = getopt(argc, argv, "dv")) != EOF) switch(c) {
  74         case 'd':
  75         case 'v':
  76                 opt_d = 1;
  77                 break;
  78         default:
  79                 usage();
  80    }
  81
  82    /* No more arguments allowed. */
  83    if (optind != argc) usage();
  84
  85    /* Obtain the name of the remote host. */
  86    if (ioctl(0, NWIOGTCPCONF, &tcpconf) < 0) {
  87         sprintf(buff, "Unable to obtain your IP address\r\n");
  88         (void) write(1, buff, strlen(buff));
  89         return(-1);
  90    }
  91    if ((hostent = gethostbyaddr((char *) &tcpconf.nwtc_remaddr,
  92                         sizeof(tcpconf.nwtc_remaddr), AF_INET)) != NULL) {
  93         hostname = hostent->h_name;
  94    } else {
  95         hostname = inet_ntoa(tcpconf.nwtc_remaddr);
  96    }
  97
  98    /* Try allocating a PTY. */
  99    if (get_pty(&pty_fd, &tty_name) < 0) {
 100         sprintf(buff, "I am sorry, but there is no free PTY left!\r\n");
 101         (void) write(1, buff, strlen(buff));
 102         return(-1);
 103    }
 104
 105    /* Find the tty in the tty table. */
 106    lineno = 0;
 107    for (;;) {
 108         if ((ttyp = getttyent()) == NULL) {
 109                 sprintf(buff, "Can't find %s in the tty table\r\n");
 110                 (void) write(1, buff, strlen(buff));
 111         }
 112         if (strcmp(ttyp->ty_name, tty_name+5) == 0) break;
 113         lineno++;
 114    }
 115    endttyent();
 116
 117    /* Initialize the connection to an 8 bit clean channel. */
 118    term_init();
 119
 120    /* Fork off a child process and have it execute a getty(8). */
 121    if ((pid = fork()) == 0) {
 122         /* Set up a new session. */
 123         setsid();
 124         if ((tty_fd = open(tty_name, O_RDWR)) < 0) {
 125                 sprintf(buff, "Can't open %s\r\n", tty_name);
 126                 (void) write(1, buff, strlen(buff));
 127                 return(-1);
 128         }
 129
 130         close(pty_fd);
 131         dup2(tty_fd, 0);
 132         dup2(tty_fd, 1);
 133         dup2(tty_fd, 2);
 134         close(tty_fd);
 135         (void) execl("/usr/sbin/getty", "getty", (char *)NULL);
 136         (void) execl("/usr/bin/getty", "getty", (char *)NULL);
 137         (void) execl("/usr/bin/login", "login", (char *)NULL);
 138         (void) write(1, "EXEC failed!\r\n", 14);
 139    } else if (pid < 0) {
 140         sprintf(buff, "I am sorry, but the fork(2) call failed!\r\n");
 141         (void) write(1, buff, strlen(buff));
 142         (void) close(pty_fd);
 143         return(-1);
 144    }
 145
 146    wtmp(LOGIN_PROCESS, lineno, tty_name+5, pid, hostname);
 147
 148    term_inout(pty_fd);
 149
 150    (void) close(pty_fd);
 151
 152    wtmp(DEAD_PROCESS, lineno, tty_name+5, pid, hostname);
 153
 154    chown(tty_name, 0, 0);
 155    chmod(tty_name, 0666);
 156
 157    return(0);
 158 }