pptp.c

/*
	an implementation of the PPTP protocol
	Copyright (C) 2000  Free Software Foundation

	This program is free software; you can redistribute it and/or modify
	it under the terms of the GNU General Public License as published by
	the Free Software Foundation; either version 2 of the License, or
	(at your option) any later version.

	This program is distributed in the hope that it will be useful,
	but WITHOUT ANY WARRANTY; without even the implied warranty of
	MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
	GNU General Public License for more details.

	You should have received a copy of the GNU General Public License
	along with this program; if not, write to the Free Software
	Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
	02110-1301, USA.

	pptp.c ... client shell to launch call managers, data handlers, and
	the pppd from the command line.
*/

#include <sys/types.h>
#include <sys/socket.h>
#if defined(__FreeBSD__)
#include <libutil.h>
#elif defined(__NetBSD__) || defined(__OpenBSD__)
#include <util.h>
#elif defined(__APPLE__)
#include <util.h>
#elif defined (__SVR4) && defined (__sun)
#else
#include <pty.h>
#endif
#ifdef USER_PPP
#include <fcntl.h>
#endif
#include <netinet/in.h>
#include <arpa/inet.h>
#include <sys/un.h>
#include <netdb.h>
#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include <syslog.h>
#include <unistd.h>
#include <signal.h>
#include <setjmp.h>
#include <errno.h>
#include <sys/wait.h>
#include <sys/param.h>
#if defined(__APPLE__)
#include "getopt.h"
#else
#include <getopt.h>
#endif
#include <limits.h>
#include "config.h"
#include "pptp_callmgr.h"
#include "pptp_gre.h"
#include "version.h"
#if defined(__linux__)
#include <sys/prctl.h>
#endif
#include "util.h"
#include "pptp_quirks.h"
#include "pqueue.h"
#include "pptp_options.h"
#include "pptp_compat.h"

#ifndef PPPD_BINARY
#define PPPD_BINARY "pppd"
#endif

int syncppp = 0;
int log_level = 1;
int disable_buffer = 0;
int test_type = 0;
int test_rate = 100;
int missing_window = MISSING_WINDOW;

struct in_addr get_ip_address(char *name);
int open_callmgr(struct in_addr inetaddr, char *phonenr, char *client_hostname, int argc, char **argv,char **envp, int pty_fd, int gre_fd);
void launch_callmgr(struct in_addr inetaddr, char *phonenr, char *client_hostname, int argc, char **argv,char **envp);
int get_call_id(int sock, pid_t gre, pid_t pppd, 
		 u_int16_t *call_id, u_int16_t *peer_call_id);
void launch_pppd(char *ttydev, int argc, char **argv);

/*** print usage and exit *****************************************************/
void usage(char *progname)
{
    fprintf(stderr,
            "%s\n"

"Copyright (C) 2000  Free Software Foundation\n\n"

"This program comes with ABSOLUTELY NO WARRANTY; for details see source.\n"
"This is free software, and you are welcome to redistribute it under certain\n"
"conditions; see source for details.\n\n"

            "Usage:\n"
            "  %s <hostname> [<pptp options>] [[--] <pppd options>]\n"
            "\n"
            "Or using pppd's pty option: \n"
            "  pppd pty \"%s <hostname> --nolaunchpppd <pptp options>\"\n"
            "\n"
            "Available pptp options:\n"
            "  --version        Display version number and exit\n"
            "  --phone <number>	Pass <number> to remote host as phone number\n"
            "  --nolaunchpppd	Do not launch pppd, for use as a pppd pty\n"
            "  --quirks <quirk>	Work around a buggy PPTP implementation\n"
            "			Currently recognised values are BEZEQ_ISRAEL only\n"
            "  --debug		Run in foreground (for debugging with gdb)\n"
            "  --sync		Enable Synchronous HDLC (pppd must use it too)\n"
            "  --timeout <secs>	Time to wait for reordered packets (0.01 to 10 secs)\n"
	    "  --nobuffer		Disable packet buffering and reordering completely\n"
	    "  --idle-wait		Time to wait before sending echo request\n"
            "  --max-echo-wait		Time to wait before giving up on lack of reply\n"
            "  --logstring <name>	Use <name> instead of 'anon' in syslog messages\n"
            "  --localbind <addr>	Bind to specified IP address instead of wildcard\n"
#ifdef SO_MARK
            "  --rtmark <n>	Use specified policy routing mark for all packets\n"
#endif
            "  --nohostroute		Do not add host route towards <hostname>\n"
            "  --loglevel <level>	Sets the debugging level (0=low, 1=default, 2=high)\n"
            "  --test-type <type>	Damage the packet stream by reordering\n"
            "  --test-rate <n>          Do the test every n packets\n"
            "  --missing-window <n>     Enable 'missing window' validation and set packet\n"
            "                           tolerance (300=default, 6000=recommended)\n"
            "  --client-hostname <name> Specify client hostname (used by Cisco VPDN Groups)\n",

            version, progname, progname);
    log("%s called with wrong arguments, program not started.", progname);
    exit(1);
}

#if defined (__SVR4) && defined (__sun)
struct in_addr localbind = { .s_addr = INADDR_ANY };
#else
struct in_addr localbind = { INADDR_NONE };
#endif
int rtmark = 0;
int nohostroute = 0;
static int signaled = 0;

/*** do nothing signal handler ************************************************/
void do_nothing(int sig)
{ 
    /* do nothing signal handler. Better than SIG_IGN. */
    signaled = sig;
}

sigjmp_buf env;

/*** signal handler ***********************************************************/
void sighandler(int sig __attribute__ ((unused)))
{
    siglongjmp(env, 1);
}

/*** report statistics signal handler (SIGUSR1) *******************************/
void sigstats(int sig __attribute__ ((unused)))
{
    syslog(LOG_NOTICE, "GRE statistics:\n");
#define LOG(name,value) syslog(LOG_NOTICE, name "\n", stats .value)
    LOG("rx accepted  = %d", rx_accepted);
    LOG("rx lost      = %d", rx_lost);
    LOG("rx under win = %d", rx_underwin);
    LOG("rx over  win = %d", rx_overwin);
    LOG("rx buffered  = %d", rx_buffered);
    LOG("rx OS errors = %d", rx_errors);
    LOG("rx truncated = %d", rx_truncated);
    LOG("rx invalid   = %d", rx_invalid);
    LOG("rx acks      = %d", rx_acks);
    LOG("tx sent      = %d", tx_sent);
    LOG("tx failed    = %d", tx_failed);
    LOG("tx short     = %d", tx_short);
    LOG("tx acks      = %d", tx_acks);
    LOG("tx oversize  = %d", tx_oversize);
    LOG("round trip   = %d usecs", rtt);
#undef LOG
}

/*** main *********************************************************************/
/* TODO: redesign to avoid longjmp/setjmp.  Several variables here
   have a volatile qualifier to silence warnings from gcc < 3.0.
   Remove the volatile qualifiers if longjmp/setjmp are removed.
   */
int main(int argc, char **argv, char **envp)
{
    struct in_addr inetaddr;
    volatile int callmgr_sock = -1;
    char ttydev[PATH_MAX];
    char *pty_name;
    int pty_fd, tty_fd, gre_fd, rc;
    volatile pid_t parent_pid, child_pid;
    u_int16_t call_id, peer_call_id;
    char buf[128];
    int pppdargc;
    char **pppdargv;
    char phonenrbuf[65]; /* maximum length of field plus one for the trailing
                          * '\0' */
    char client_hostname_buf[64] = {0}; /* maximum length plus trailing '\0' */
    char * volatile client_hostname = NULL;
    char * volatile phonenr = NULL;
    volatile int launchpppd = 1, debug = 0;

    while(1){ 
        /* structure with all recognised options for pptp */
        static struct option long_options[] = {
            {"phone", 1, 0, 0},  
            {"nolaunchpppd", 0, 0, 0},  
            {"quirks", 1, 0, 0},
            {"debug", 0, 0, 0},
            {"sync", 0, 0, 0},
            {"timeout", 1, 0, 0},
            {"logstring", 1, 0, 0},
            {"localbind", 1, 0, 0},
            {"loglevel", 1, 0, 0},
	    {"nobuffer", 0, 0, 0},
	    {"idle-wait", 1, 0, 0},
	    {"max-echo-wait", 1, 0, 0},
	    {"version", 0, 0, 0},
	    {"test-type", 1, 0, 0},
	    {"test-rate", 1, 0, 0},
	    {"rtmark", 1, 0, 0},
	    {"nohostroute", 0, 0, 0},
	    {"missing-window", 1, 0, 0},
	    {"client-hostname", 1, 0, 0},
            {0, 0, 0, 0}
        };
        int option_index = 0;
        int c;
        c = getopt_long (argc, argv, "", long_options, &option_index);
        if (c == -1) break;  /* no more options */
        switch (c) {
            case 0: 
                if (option_index == 0) { /* --phone specified */
                    strncpy(phonenrbuf,optarg,sizeof(phonenrbuf));
                    phonenrbuf[sizeof(phonenrbuf) - 1] = '\0';
                    phonenr = phonenrbuf;
                } else if (option_index == 1) {/* --nolaunchpppd specified */
                    launchpppd = 0;
                } else if (option_index == 2) {/* --quirks specified */
                    if (set_quirk_index(find_quirk(optarg)))
                        usage(argv[0]);
                } else if (option_index == 3) {/* --debug */
                    debug = 1;
                } else if (option_index == 4) {/* --sync specified */
                    syncppp = 1;
                } else if (option_index == 5) {/* --timeout */
                    float new_packet_timeout = atof(optarg);
                    if (new_packet_timeout < 0.0099 ||
                            new_packet_timeout > 10) {
                        fprintf(stderr, "Packet timeout %s (%f) out of range: "
                                "should be between 0.01 and 10 seconds\n",
                                optarg, new_packet_timeout);
                        log("Packet timeout %s (%f) out of range: should be"
                                "between 0.01 and 10 seconds", optarg,
                                new_packet_timeout);
                        exit(2);
                    } else {
                        packet_timeout_usecs = new_packet_timeout * 1000000;
                    }
                } else if (option_index == 6) {/* --logstring */
                    log_string = strdup(optarg);
                } else if (option_index == 7) {/* --localbind */ 
                    if (inet_pton(AF_INET, optarg, (void *) &localbind) < 1) {
                        fprintf(stderr, "Local bind address %s invalid\n", 
				optarg);
                        log("Local bind address %s invalid\n", optarg);
                        exit(2);
                    }
                } else if (option_index == 8) { /* --loglevel */
                    log_level = atoi(optarg);
                    if (log_level < 0 || log_level > 2)
                        usage(argv[0]);
                } else if (option_index == 9) { /* --nobuffer */
		    disable_buffer = 1;
                } else if (option_index == 10) { /* --idle-wait */
                    int x = atoi(optarg);
                    if (x < 0) {
                        fprintf(stderr, "--idle-wait must not be negative\n");
                        log("--idle-wait must not be negative\n");
                        exit(2);
                    } else {
                        idle_wait = x;
                    }
                } else if (option_index == 11) { /* --max-echo-wait */
                    int x = atoi(optarg);
                    if (x < 0) {
                        fprintf(stderr, "--max-echo-wait must not be negative\n");
                        log("--max-echo-wait must not be negative\n");
                        exit(2);
                    } else {
                        max_echo_wait = x;
                    }
		    fprintf(stderr, "--max-echo-wait ignored, not yet implemented\n");
                } else if (option_index == 12) { /* --version */
		    fprintf(stdout, "%s\n", version);
		    exit(0);
		} else if (option_index == 13) { /* --test-type */
		    test_type = atoi(optarg);
		} else if (option_index == 14) { /* --test-rate */
		    test_rate = atoi(optarg);
		} else if (option_index == 15) { /* --rtmark */
#ifdef SO_MARK
		    rtmark = atoi(optarg);
#else
		    fprintf(stderr, "--rtmark support was missing when "
				    "this binary was compiled.\n");
		    exit(2);
#endif
		} else if (option_index == 16) { /* --nohostroute */
		    nohostroute = 1;
		} else if (option_index == 17) { /* --missing window */
		    int x = atoi(optarg);
		    if (x <= 0) {
			fprintf(stderr, "--missing-window must be integer "
				"greater than zero\n");
			log("--missing-window must be integer "
			    "greater than zero\n");
			exit(2);
		    } else if (x < 300) {
			fprintf(stderr, "--missing-window is set very low: "
				"default=300, recommended=6000 - proceeding");
			log("--missing-window is set very low: "
			    "default=300, recommended=6000 - proceeding\n");
		    } else {
			fprintf(stderr, "--missing-window validation is active "
				"and set to: %d\n", x);
			log("--missing-window validation is active "
			    "and set to: %d\n", x);
			missing_window = x;
		    }
		} else if (option_index == 18) { /* --client-hostname */
		    strncpy(client_hostname_buf, optarg, sizeof(client_hostname_buf));
		    client_hostname_buf[63] = '\0'; /* Terminate string to be safe */
		    log("client-hostname set to %s\n", client_hostname_buf);
		    client_hostname = client_hostname_buf;
		}
                break;
            case '?': /* unrecognised option */
                /* fall through */
            default:
		usage(argv[0]);
        }
    }

    /* at least one argument is required */
    if (argc <= optind)
        usage(argv[0]);

    /* Get IP address for the hostname in argv[1] */
    inetaddr = get_ip_address(argv[optind]);
    optind++;

    /* Find the ppp options, extract phone number */
    pppdargc = argc - optind;
    pppdargv = argv + optind;
    log("The synchronous pptp option is %sactivated\n", syncppp ? "" : "NOT ");

    /* Now we have the peer address, bind the GRE socket early,
       before starting pppd. This prevents the ICMP Unreachable bug
       documented in <1026868263.2855.67.camel@jander> */
    gre_fd = pptp_gre_bind(inetaddr);
    if (gre_fd < 0) {
        fatal("Cannot bind GRE socket, aborting.");
    }

    /* Find an open pty/tty pair. */
    if(launchpppd){
        rc = openpty (&pty_fd, &tty_fd, ttydev, NULL, NULL);
        if (rc < 0) { 
            fatal("Could not find free pty.");
        }

        /* fork and wait. */
        signal(SIGUSR1, do_nothing); /* don't die */
        signal(SIGCHLD, do_nothing); /* don't ignore SIGCHLD */
        parent_pid = getpid();
        switch (child_pid = fork()) {
            case -1:
                fatal("Could not fork pppd process");
            case 0: /* I'm the child! */
                close (tty_fd);
                signal(SIGUSR1, SIG_DFL);
                child_pid = getpid();
                break;
            default: /* parent */
                close (pty_fd);
                /*
                 * There is still a very small race condition here.  If a signal
                 * occurs after signaled is checked but before pause is called,
                 * things will hang.
                 */
                if (!signaled) {
                    pause(); /* wait for the signal */
                }
 
                if (signaled == SIGCHLD)
                    fatal("Child process died");
 
                launch_pppd(ttydev, pppdargc, pppdargv); /* launch pppd */
                perror("Error");
                fatal("Could not launch pppd");
        }
    } else { /* ! launchpppd */
        pty_fd = tty_fd = STDIN_FILENO;
        /* close unused file descriptor, that is redirected to the pty */
        close(STDOUT_FILENO);
        child_pid = getpid();
        parent_pid = 0; /* don't kill pppd */
    }

    do {
        /*
         * Open connection to call manager (Launch call manager if necessary.)
         */
        callmgr_sock = open_callmgr(inetaddr, phonenr, client_hostname, argc,
		argv, envp, pty_fd, gre_fd);
        /* Exchange PIDs, get call ID */
    } while (get_call_id(callmgr_sock, parent_pid, child_pid, 
                &call_id, &peer_call_id) < 0);

    /* Send signal to wake up pppd task */
    if (launchpppd) {
        kill(parent_pid, SIGUSR1);
        sleep(2);
        /* become a daemon */
        if (!debug && daemon(0, 0) != 0) {
            perror("daemon");
        }
    } else {
        /* re-open stderr as /dev/null to release it */
        file2fd("/dev/null", "wb", STDERR_FILENO);
    }

    pty_name = ttyname(pty_fd);
    snprintf(buf, sizeof(buf), "pptp: GRE-to-PPP gateway on %s",
              pty_name ? pty_name : "(null)");
#ifdef PR_SET_NAME
    rc = prctl(PR_SET_NAME, "pptpgw", 0, 0, 0);
    if (rc != 0) perror("prctl");
#endif
    if (sigsetjmp(env, 1)!= 0) goto shutdown;

    signal(SIGINT,  sighandler);
    signal(SIGTERM, sighandler);
    signal(SIGKILL, sighandler);
    signal(SIGCHLD, sighandler);
    signal(SIGUSR1, sigstats);

    /* Do GRE copy until close. */
    pptp_gre_copy(call_id, peer_call_id, pty_fd, gre_fd);

shutdown:
    /* on close, kill all. */
    if(launchpppd)
        kill(parent_pid, SIGTERM);
    close(pty_fd);
    close(callmgr_sock);
    exit(0);
}

/*** get the ipaddress coming from the command line ***************************/
struct in_addr get_ip_address(char *name)
{
    int rc;
    struct in_addr retval;
    struct addrinfo hints, *ai;

    memset(&hints, '\0', sizeof(hints));
    hints.ai_family = AF_INET;
#if defined(__linux__) || defined(__FreeBSD__)
    hints.ai_flags = AI_ADDRCONFIG;     /* Unknown in OpenBSD. */
#endif

    if ( (rc = getaddrinfo(name, NULL, &hints, &ai)) )
        fatal("getaddrinfo(): %s", gai_strerror(rc));

    if (ai->ai_addr->sa_family != AF_INET)       /* Should never happen. */
        fatal("Host '%s' possesses no IPv4 address", name);

    memcpy(&retval.s_addr,
            &(((struct sockaddr_in *) ai->ai_addr)->sin_addr.s_addr),
            sizeof(retval.s_addr));
    freeaddrinfo(ai);

    return retval;
}

/*** start the call manager ***************************************************/
int open_callmgr(struct in_addr inetaddr, char *phonenr, char *client_hostname,
        int argc, char **argv, char **envp, int pty_fd, int gre_fd)
{
    /* Try to open unix domain socket to call manager. */
    union {
        struct sockaddr a;
        struct sockaddr_un u;
    } where;
    const int NUM_TRIES = 3;
    int i, fd;
    pid_t pid;
    int status;
    /* Open socket */
    if ((fd = socket(AF_UNIX, SOCK_STREAM, 0)) < 0) {
        fatal("Could not create unix domain socket: %s", strerror(errno));
    }
    /* Make address */
    callmgr_name_unixsock(&where.u, inetaddr, localbind);
    for (i = 0; i < NUM_TRIES; i++) {
        if (connect(fd, &where.a, sizeof(where)) < 0) {
            /* couldn't connect.  We'll have to launch this guy. */

            unlink (where.u.sun_path); /* FIXME: potential race condition */

            /* fork and launch call manager process */
            switch (pid = fork()) {
                case -1: /* failure */
                    fatal("fork() to launch call manager failed.");
                case 0: /* child */
                {
                    close (fd);
                    /* close the pty and gre in the call manager */
                    close(pty_fd);
                    close(gre_fd);
                    launch_callmgr(inetaddr, phonenr, client_hostname, argc,
                        argv, envp);
                }
                default: /* parent */
                    waitpid(pid, &status, 0);
                    if (WEXITSTATUS(status) != 0)
                        fatal("Call manager exited with error %d", status);
                    break;
            }
            sleep(1);
        }
        else return fd;
    }
    close(fd);
    fatal("Could not launch call manager after %d tries.", i);
    return -1;   /* make gcc happy */
}

/*** call the call manager main ***********************************************/
void launch_callmgr(struct in_addr inetaddr, char *phonenr, char *client_hostname,
        int argc __attribute__ ((unused)), char**argv, char**envp)
{
      char *my_argv[4] = { argv[0], inet_ntoa(inetaddr), phonenr, client_hostname };
      char buf[128];
      snprintf(buf, sizeof(buf), "pptp: call manager for %s", my_argv[1]);
#ifdef PR_SET_NAME
      int rc;
      rc = prctl(PR_SET_NAME, "pptpcm", 0, 0, 0);
      if (rc != 0) perror("prctl");
#endif
      exit(callmgr_main(3, my_argv, envp));
}

/*** exchange data with the call manager  *************************************/
/* XXX need better error checking XXX */
int get_call_id(int sock, pid_t gre, pid_t pppd, 
		 u_int16_t *call_id, u_int16_t *peer_call_id)
{
    u_int16_t m_call_id, m_peer_call_id;
    /* write pid's to socket */
    /* don't bother with network byte order, because pid's are meaningless
     * outside the local host.
     */
    int rc;
    rc = write(sock, &gre, sizeof(gre));
    if (rc != sizeof(gre))
        return -1;
    rc = write(sock, &pppd, sizeof(pppd));
    if (rc != sizeof(pppd))
        return -1;
    rc = read(sock,  &m_call_id, sizeof(m_call_id));
    if (rc != sizeof(m_call_id))
        return -1;
    rc = read(sock,  &m_peer_call_id, sizeof(m_peer_call_id));
    if (rc != sizeof(m_peer_call_id))
        return -1;
    /*
     * XXX FIXME ... DO ERROR CHECKING & TIME-OUTS XXX
     * (Rhialto: I am assuming for now that timeouts are not relevant
     * here, because the read and write calls would return -1 (fail) when
     * the peer goes away during the process. We know it is (or was)
     * running because the connect() call succeeded.)
     * (James: on the other hand, if the route to the peer goes away, we
     * wouldn't get told by read() or write() for quite some time.)
     */
    *call_id = m_call_id;
    *peer_call_id = m_peer_call_id;
    return 0;
}

/*** execvp pppd **************************************************************/
void launch_pppd(char *ttydev, int argc, char **argv)
{
    char *new_argv[argc + 4];/* XXX if not using GCC, hard code a limit here. */
    char str_pppd[] = PPPD_BINARY;
    char str_direct[] __attribute__ ((unused)) = "-direct";
    char str_38400[] = "38400";
    int i = 0, j;
    new_argv[i++] = str_pppd;
#ifdef USER_PPP
    new_argv[i++] = str_direct;
    /* ppp expects to have stdin connected to ttydev */
    if ((j = open(ttydev, O_RDWR)) == -1)
        fatal("Cannot open %s: %s", ttydev, strerror(errno));
    if (dup2(j, 0) == -1)
        fatal("dup2 failed: %s", strerror(errno));
    close(j);
#else
    new_argv[i++] = ttydev;
    new_argv[i++] = str_38400;
#endif
    for (j = 0; j < argc; j++)
        new_argv[i++] = argv[j];
    new_argv[i] = NULL;
    execvp(new_argv[0], new_argv);
}