xref: /freebsd-11-stable/usr.sbin/ppp/main.c

/*-
 * SPDX-License-Identifier: BSD-2-Clause-FreeBSD
 *
 * Copyright (c) 1996 - 2001 Brian Somers <brian@Awfulhak.org>
 *          based on work by Toshiharu OHNO <tony-o@iij.ad.jp>
 *                           Internet Initiative Japan, Inc (IIJ)
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 *
 * $FreeBSD: stable/11/usr.sbin/ppp/main.c 330449 2018-03-05 07:26:05Z eadler $
 */

#include <sys/param.h>
#include <netinet/in.h>
#include <netinet/in_systm.h>
#include <netinet/ip.h>
#include <sys/un.h>
#include <sys/socket.h>
#include <net/route.h>

#include <errno.h>
#include <fcntl.h>
#include <paths.h>
#include <signal.h>
#include <stdarg.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/time.h>
#include <termios.h>
#include <unistd.h>
#include <sys/stat.h>

#ifndef NONAT
#ifdef LOCALNAT
#include "alias.h"
#else
#include <alias.h>
#endif
#endif

#include "layer.h"
#include "probe.h"
#include "mbuf.h"
#include "log.h"
#include "defs.h"
#include "id.h"
#include "timer.h"
#include "fsm.h"
#include "lqr.h"
#include "hdlc.h"
#include "lcp.h"
#include "ccp.h"
#include "iplist.h"
#include "throughput.h"
#include "slcompress.h"
#include "ncpaddr.h"
#include "ipcp.h"
#include "filter.h"
#include "descriptor.h"
#include "link.h"
#include "mp.h"
#ifndef NORADIUS
#include "radius.h"
#endif
#include "ipv6cp.h"
#include "ncp.h"
#include "bundle.h"
#include "auth.h"
#include "systems.h"
#include "sig.h"
#include "main.h"
#include "server.h"
#include "prompt.h"
#include "chat.h"
#include "chap.h"
#include "cbcp.h"
#include "datalink.h"
#include "iface.h"

#ifndef O_NONBLOCK
#ifdef O_NDELAY
#define	O_NONBLOCK O_NDELAY
#endif
#endif

static void DoLoop(struct bundle *);
static void TerminalStop(int);

static struct bundle *SignalBundle;
static struct prompt *SignalPrompt;
struct libalias *la;

void
Cleanup()
{
  SignalBundle->CleaningUp = 1;
  bundle_Close(SignalBundle, NULL, CLOSE_STAYDOWN);
}

void
AbortProgram(int excode)
{
  if (SignalBundle)
    server_Close(SignalBundle);
  log_Printf(LogPHASE, "PPP Terminated (%s).\n", ex_desc(excode));
  if (SignalBundle) {
    bundle_Close(SignalBundle, NULL, CLOSE_STAYDOWN);
    bundle_Destroy(SignalBundle);
  }
  log_Close();
  exit(excode);
}

static void
CloseConnection(int signo)
{
  /* NOTE, these are manual, we've done a setsid() */
  sig_signal(SIGINT, SIG_IGN);
  log_Printf(LogPHASE, "Caught signal %d, abort connection(s)\n", signo);
  bundle_Down(SignalBundle, CLOSE_STAYDOWN);
  sig_signal(SIGINT, CloseConnection);
}

static void
CloseSession(int signo)
{
  log_Printf(LogPHASE, "Signal %d, terminate.\n", signo);
  Cleanup();
}

static pid_t BGPid = 0;

static void
KillChild(int signo)
{
  signal(signo, SIG_IGN);
  log_Printf(LogPHASE, "Parent: Signal %d\n", signo);
  kill(BGPid, SIGINT);
}

static void
TerminalCont(int signo __unused)
{
  signal(SIGCONT, SIG_DFL);
  prompt_Continue(SignalPrompt);
}

static void
TerminalStop(int signo __unused)
{
  prompt_Suspend(SignalPrompt);
  signal(SIGCONT, TerminalCont);
  raise(SIGSTOP);
}

static void
BringDownServer(int signo __unused)
{
  /* Drops all child prompts too ! */
  if (server_Close(SignalBundle))
    log_Printf(LogPHASE, "Closed server socket\n");
}

static void
RestartServer(int signo __unused)
{
  /* Drops all child prompts and re-opens the socket */
  server_Reopen(SignalBundle);
}

static void
Usage(void)
{
  fprintf(stderr, "usage: ppp [-auto | -foreground | -background | -direct |"
          " -dedicated | -ddial | -interactive]"
#ifndef NONAT
          " [-nat]"
#endif
          " [-quiet] [-unit N] [system ...]\n");
  exit(EX_START);
}

struct switches {
  unsigned nat : 1;
  unsigned fg : 1;
  unsigned quiet : 1;
  int mode;
  int unit;
};

static int
ProcessArgs(int argc, char **argv, struct switches *sw)
{
  int optc, newmode, arg;
  char *cp;

  optc = 0;
  memset(sw, '\0', sizeof *sw);
  sw->mode = PHYS_INTERACTIVE;
  sw->unit = -1;

  for (arg = 1; arg < argc && *argv[arg] == '-'; arg++, optc++) {
    cp = argv[arg] + 1;
    newmode = Nam2mode(cp);
    switch (newmode) {
      case PHYS_NONE:
        if (strcmp(cp, "nat") == 0) {
#ifdef NONAT
          log_Printf(LogWARN, "%s ignored: NAT is compiled out\n", argv[arg]);
#else
          sw->nat = 1;
#endif
          optc--;			/* this option isn't exclusive */
        } else if (strcmp(cp, "alias") == 0) {
#ifdef NONAT
          log_Printf(LogWARN, "%s ignored: NAT is compiled out\n", argv[arg]);
          fprintf(stderr, "%s ignored: NAT is compiled out\n", argv[arg]);
#else
          log_Printf(LogWARN, "%s is deprecated\n", argv[arg]);
          fprintf(stderr, "%s is deprecated\n", argv[arg]);
          sw->nat = 1;
#endif
          optc--;			/* this option isn't exclusive */
        } else if (strncmp(cp, "unit", 4) == 0) {
          optc--;			/* this option isn't exclusive */
          if (cp[4] == '\0') {
            optc--;			/* nor is the argument */
            if (++arg == argc) {
              fprintf(stderr, "-unit: Expected unit number\n");
              Usage();
            } else
              sw->unit = atoi(argv[arg]);
          } else
            sw->unit = atoi(cp + 4);
        } else if (strcmp(cp, "quiet") == 0) {
          sw->quiet = 1;
          optc--;			/* this option isn't exclusive */
        } else
          Usage();
        break;

      case PHYS_ALL:
        Usage();
        break;

      default:
        sw->mode = newmode;
        if (newmode == PHYS_FOREGROUND)
          sw->fg = 1;
    }
  }

  if (optc > 1) {
    fprintf(stderr, "You may specify only one mode.\n");
    exit(EX_START);
  }

  if (sw->mode == PHYS_AUTO && arg == argc) {
    fprintf(stderr, "A system must be specified in auto mode.\n");
    exit(EX_START);
  }

  return arg;		/* Don't SetLabel yet ! */
}

static void
CheckLabel(const char *label, struct prompt *prompt, int mode)
{
  const char *err;

  if ((err = system_IsValid(label, prompt, mode)) != NULL) {
    fprintf(stderr, "%s: %s\n", label, err);
    if (mode == PHYS_DIRECT)
      log_Printf(LogWARN, "Label %s rejected -direct connection: %s\n",
                 label, err);
    log_Close();
    exit(1);
  }
}


int
main(int argc, char **argv)
{
  char *name;
  const char *lastlabel;
  int arg, holdfd[3], label;
  unsigned f;
  struct bundle *bundle;
  struct prompt *prompt;
  struct switches sw;

  probe_Init();

  /*
   * We open 3 descriptors to ensure that STDIN_FILENO, STDOUT_FILENO and
   * STDERR_FILENO are always open.  These are closed before DoLoop(),
   * but *after* we've avoided the possibility of erroneously closing
   * an important descriptor with close(STD{IN,OUT,ERR}_FILENO).
   */
  if ((holdfd[0] = open(_PATH_DEVNULL, O_RDWR)) == -1) {
    fprintf(stderr, "Cannot open %s !\n", _PATH_DEVNULL);
    return 2;
  }
  for (f = 1; f < sizeof holdfd / sizeof *holdfd; f++)
    holdfd[f] = dup(holdfd[0]);

  name = strrchr(argv[0], '/');
  log_Open(name ? name + 1 : argv[0]);

#ifndef NONAT
  la = LibAliasInit(NULL);
#endif
  label = ProcessArgs(argc, argv, &sw);

  /*
   * A FreeBSD & OpenBSD hack to dodge a bug in the tty driver that drops
   * output occasionally.... I must find the real reason some time.  To
   * display the dodgy behaviour, comment out this bit, make yourself a large
   * routing table and then run ppp in interactive mode.  The `show route'
   * command will drop chunks of data !!!
   */
  if (sw.mode == PHYS_INTERACTIVE) {
    close(STDIN_FILENO);
    if (open(_PATH_TTY, O_RDONLY) != STDIN_FILENO) {
      fprintf(stderr, "Cannot open %s for input !\n", _PATH_TTY);
      return 2;
    }
  }

  /* Allow output for the moment (except in direct mode) */
  if (sw.mode == PHYS_DIRECT)
    prompt = NULL;
  else
    SignalPrompt = prompt = prompt_Create(NULL, NULL, PROMPT_STD);

  ID0init();
  if (ID0realuid() != 0) {
    char conf[200], *ptr;

    snprintf(conf, sizeof conf, "%s/%s", PPP_CONFDIR, CONFFILE);
    do {
      struct stat sb;

      if (stat(conf, &sb) == 0 && sb.st_mode & S_IWOTH) {
        log_Printf(LogALERT, "ppp: Access violation: Please protect %s\n",
                   conf);
        return -1;
      }
      ptr = conf + strlen(conf)-2;
      while (ptr > conf && *ptr != '/')
        *ptr-- = '\0';
    } while (ptr >= conf);
  }

  if (label < argc)
    for (arg = label; arg < argc; arg++)
      CheckLabel(argv[arg], prompt, sw.mode);
  else
    CheckLabel("default", prompt, sw.mode);

  if (!sw.quiet)
    prompt_Printf(prompt, "Working in %s mode\n", mode2Nam(sw.mode));

  if ((bundle = bundle_Create(TUN_PREFIX, sw.mode, sw.unit)) == NULL)
    return EX_START;

  /* NOTE:  We may now have changed argv[1] via a ``set proctitle'' */

  SignalBundle = bundle;
  bundle->NatEnabled = sw.nat;
  if (sw.nat)
    opt_enable(bundle, OPT_IFACEALIAS);

  if (system_Select(bundle, "default", CONFFILE, prompt, NULL) < 0)
    prompt_Printf(prompt, "Warning: No default entry found in config file.\n");

  sig_signal(SIGHUP, CloseSession);
  sig_signal(SIGTERM, CloseSession);
  sig_signal(SIGINT, CloseConnection);
  sig_signal(SIGQUIT, CloseSession);
  sig_signal(SIGALRM, SIG_IGN);
  signal(SIGPIPE, SIG_IGN);

  if (sw.mode == PHYS_INTERACTIVE)
    sig_signal(SIGTSTP, TerminalStop);

  sig_signal(SIGUSR1, RestartServer);
  sig_signal(SIGUSR2, BringDownServer);

  lastlabel = argv[argc - 1];
  for (arg = label; arg < argc; arg++) {
    /* In case we use LABEL or ``set enddisc label'' */
    bundle_SetLabel(bundle, lastlabel);
    system_Select(bundle, argv[arg], CONFFILE, prompt, NULL);
  }

  if (label < argc)
    /* In case the last label did a ``load'' */
    bundle_SetLabel(bundle, lastlabel);

  if (sw.mode == PHYS_AUTO &&
      ncprange_family(&bundle->ncp.ipcp.cfg.peer_range) == AF_UNSPEC) {
    prompt_Printf(prompt, "You must ``set ifaddr'' with a peer address "
                  "in auto mode.\n");
    AbortProgram(EX_START);
  }

  if (prompt) {
    prompt->bundle = bundle;	/* couldn't do it earlier */
    if (!sw.quiet)
      prompt_Printf(prompt, "Using interface: %s\n", bundle->iface->name);
  }

  if (sw.mode != PHYS_INTERACTIVE) {
    if (sw.mode != PHYS_DIRECT) {
      if (!sw.fg) {
        int bgpipe[2];
        pid_t bgpid;

        if (sw.mode == PHYS_BACKGROUND && pipe(bgpipe)) {
          log_Printf(LogERROR, "pipe: %s\n", strerror(errno));
	  AbortProgram(EX_SOCK);
        }

        bgpid = fork();
        if (bgpid == -1) {
	  log_Printf(LogERROR, "fork: %s\n", strerror(errno));
	  AbortProgram(EX_SOCK);
        }

        if (bgpid) {
	  char c = EX_NORMAL;
          int ret;

	  if (sw.mode == PHYS_BACKGROUND) {
	    close(bgpipe[1]);
	    BGPid = bgpid;
            /* If we get a signal, kill the child */
            signal(SIGHUP, KillChild);
            signal(SIGTERM, KillChild);
            signal(SIGINT, KillChild);
            signal(SIGQUIT, KillChild);

	    /* Wait for our child to close its pipe before we exit */
            while ((ret = read(bgpipe[0], &c, 1)) == 1) {
              switch (c) {
                case EX_NORMAL:
                  if (!sw.quiet) {
	            prompt_Printf(prompt, "PPP enabled\n");
	            log_Printf(LogPHASE, "Parent: PPP enabled\n");
                  }
	          break;
                case EX_REDIAL:
                  if (!sw.quiet)
	            prompt_Printf(prompt, "Attempting redial\n");
                  continue;
                case EX_RECONNECT:
                  if (!sw.quiet)
	            prompt_Printf(prompt, "Attempting reconnect\n");
                  continue;
	        default:
	          prompt_Printf(prompt, "Child failed (%s)\n",
                                ex_desc((int)c));
	          log_Printf(LogPHASE, "Parent: Child failed (%s)\n",
		             ex_desc((int) c));
	      }
	      break;
            }
            if (ret != 1) {
	      prompt_Printf(prompt, "Child exit, no status.\n");
	      log_Printf(LogPHASE, "Parent: Child exit, no status.\n");
	    }
	    close(bgpipe[0]);
	  }
	  return c;
        } else if (sw.mode == PHYS_BACKGROUND) {
	  close(bgpipe[0]);
          bundle->notify.fd = bgpipe[1];
        }

        bundle_ChangedPID(bundle);
        bundle_LockTun(bundle);	/* we have a new pid */
      }

      /* -auto, -dedicated, -ddial, -foreground & -background */
      prompt_Destroy(prompt, 0);
      close(STDOUT_FILENO);
      close(STDERR_FILENO);
      close(STDIN_FILENO);
      if (!sw.fg)
        setsid();
    } else {
      /*
       * -direct - STDIN_FILENO gets used by physical_Open.  STDOUT_FILENO
       * *may* get used in exec/pipe mode.
       */
      prompt_TtyInit(NULL);
      close(STDERR_FILENO);
    }
  } else {
    /* -interactive */
    close(STDERR_FILENO);
    prompt_TtyInit(prompt);
    prompt_TtyCommandMode(prompt);
    prompt_Required(prompt);
  }

  /* We can get rid of these now */
  for (f = 0; f < sizeof holdfd / sizeof *holdfd; f++)
    close(holdfd[f]);

  log_Printf(LogPHASE, "PPP Started (%s mode).\n", mode2Nam(sw.mode));
  DoLoop(bundle);
  AbortProgram(EX_NORMAL);

  return EX_NORMAL;
}

static void
DoLoop(struct bundle *bundle)
{
  fd_set *rfds, *wfds, *efds;
  int i, nfds, nothing_done;

  if ((rfds = mkfdset()) == NULL) {
    log_Printf(LogERROR, "DoLoop: Cannot create fd_set\n");
    return;
  }

  if ((wfds = mkfdset()) == NULL) {
    log_Printf(LogERROR, "DoLoop: Cannot create fd_set\n");
    free(rfds);
    return;
  }

  if ((efds = mkfdset()) == NULL) {
    log_Printf(LogERROR, "DoLoop: Cannot create fd_set\n");
    free(rfds);
    free(wfds);
    return;
  }

  for (; !bundle_IsDead(bundle); bundle_CleanDatalinks(bundle)) {
    nfds = 0;
    zerofdset(rfds);
    zerofdset(wfds);
    zerofdset(efds);

    /* All our datalinks, the tun device and the MP socket */
    descriptor_UpdateSet(&bundle->desc, rfds, wfds, efds, &nfds);

    /* All our prompts and the diagnostic socket */
    descriptor_UpdateSet(&server.desc, rfds, NULL, NULL, &nfds);

    bundle_CleanDatalinks(bundle);
    if (bundle_IsDead(bundle))
      /* Don't select - we'll be here forever */
      break;

    /*
     * It's possible that we've had a signal since we last checked.  If
     * we don't check again before calling select(), we may end up stuck
     * after having missed the event.... sig_Handle() tries to be as
     * quick as possible if nothing is likely to have happened.
     * This is only really likely if we block in open(... O_NONBLOCK)
     * which will happen with a misconfigured device.
     */
    if (sig_Handle())
      continue;

    i = select(nfds, rfds, wfds, efds, NULL);

    if (i < 0 && errno != EINTR) {
      log_Printf(LogERROR, "DoLoop: select(): %s\n", strerror(errno));
      if (log_IsKept(LogTIMER)) {
        struct timeval t;

        for (i = 0; i <= nfds; i++) {
          if (FD_ISSET(i, rfds)) {
            log_Printf(LogTIMER, "Read set contains %d\n", i);
            FD_CLR(i, rfds);
            t.tv_sec = t.tv_usec = 0;
            if (select(nfds, rfds, wfds, efds, &t) != -1) {
              log_Printf(LogTIMER, "The culprit !\n");
              break;
            }
          }
          if (FD_ISSET(i, wfds)) {
            log_Printf(LogTIMER, "Write set contains %d\n", i);
            FD_CLR(i, wfds);
            t.tv_sec = t.tv_usec = 0;
            if (select(nfds, rfds, wfds, efds, &t) != -1) {
              log_Printf(LogTIMER, "The culprit !\n");
              break;
            }
          }
          if (FD_ISSET(i, efds)) {
            log_Printf(LogTIMER, "Error set contains %d\n", i);
            FD_CLR(i, efds);
            t.tv_sec = t.tv_usec = 0;
            if (select(nfds, rfds, wfds, efds, &t) != -1) {
              log_Printf(LogTIMER, "The culprit !\n");
              break;
            }
          }
        }
      }
      break;
    }

    log_Printf(LogTIMER, "Select returns %d\n", i);

    sig_Handle();

    if (i <= 0)
      continue;

    for (i = 0; i <= nfds; i++)
      if (FD_ISSET(i, efds)) {
        log_Printf(LogPHASE, "Exception detected on descriptor %d\n", i);
        /* We deal gracefully with link descriptor exceptions */
        if (!bundle_Exception(bundle, i)) {
          log_Printf(LogERROR, "Exception cannot be handled !\n");
          break;
        }
      }

    if (i <= nfds)
      break;

    nothing_done = 1;

    if (descriptor_IsSet(&server.desc, rfds)) {
      descriptor_Read(&server.desc, bundle, rfds);
      nothing_done = 0;
    }

    if (descriptor_IsSet(&bundle->desc, rfds)) {
      descriptor_Read(&bundle->desc, bundle, rfds);
      nothing_done = 0;
    }

    if (descriptor_IsSet(&bundle->desc, wfds))
      if (descriptor_Write(&bundle->desc, bundle, wfds) <= 0 && nothing_done) {
        /*
         * This is disastrous.  The OS has told us that something is
         * writable, and all our write()s have failed.  Rather than
         * going back immediately to do our UpdateSet()s and select(),
         * we sleep for a bit to avoid gobbling up all cpu time.
         */
        struct timeval t;

        t.tv_sec = 0;
        t.tv_usec = 100000;
        select(0, NULL, NULL, NULL, &t);
      }
  }

  log_Printf(LogDEBUG, "DoLoop done.\n");
}