/*      $NetBSD: rwhod.c,v 1.41 2018/10/30 21:15:09 kre Exp $   */

/*
 * Copyright (c) 1983, 1993
 *      The Regents of the University of California.  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.
 * 3. Neither the name of the University nor the names of its contributors
 *    may be used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE REGENTS 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 REGENTS 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.
 */

#include <sys/cdefs.h>
#ifndef lint
__COPYRIGHT("@(#) Copyright (c) 1983, 1993\
 The Regents of the University of California.  All rights reserved.");
#endif /* not lint */

#ifndef lint
#if 0
static char sccsid[] = "@(#)rwhod.c     8.1 (Berkeley) 6/6/93";
#else
__RCSID("$NetBSD: rwhod.c,v 1.41 2018/10/30 21:15:09 kre Exp $");
#endif
#endif /* not lint */

#include <sys/param.h>
#include <sys/socket.h>
#include <sys/stat.h>
#include <sys/signal.h>
#include <sys/ioctl.h>
#include <sys/sysctl.h>

#include <net/if.h>
#include <net/if_dl.h>
#include <net/route.h>
#include <netinet/in.h>
#include <protocols/rwhod.h>
#include <arpa/inet.h>

#include <ctype.h>
#include <pwd.h>
#include <err.h>
#include <errno.h>
#include <fcntl.h>
#include <netdb.h>
#include <paths.h>
#include <poll.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <syslog.h>
#include <unistd.h>
#include <util.h>

#include "utmpentry.h"

#define CHECK_INTERVAL (3 * 60)

/* Time interval limit; ruptime will think that we are down > than this */
#define MAX_INTERVAL (11 * 60)


static char     myname[MAXHOSTNAMELEN + 1];

/*
 * We communicate with each neighbor in a list constructed at the time we're
 * started up.  Neighbors are currently directly connected via a hardware
 * interface.
 */
struct neighbor {
        struct  neighbor *n_next;
        char    *n_name;                /* interface name */
        struct  sockaddr *n_addr;       /* who to send to */
        int     n_addrlen;              /* size of address */
        int     n_flags;                /* should forward?, interface flags */
};

static struct   neighbor *neighbors;
static struct   whod mywd;
static struct   servent *sp;
static volatile sig_atomic_t  onsighup;

#define WHDRSIZE        (sizeof(mywd) - sizeof(mywd.wd_we))

static int       configure(int);
static void      getboottime(void);
static void      send_host_information(int);
static void      sighup(int);
static void      handleread(int);
__dead static void       quit(const char *);
static void      rt_xaddrs(void *, void *, struct rt_addrinfo *);
static int       drop_privs(char *);
static void      usage(void) __dead;
static int       verify(const char *);
#ifdef DEBUG
static char     *interval(int, const char *);
static ssize_t   Sendto(int, const void *, size_t, int,
    const struct sockaddr *, socklen_t);
#else
#define  Sendto sendto
#endif

int
main(int argc, char *argv[])
{
        int s, ch;
        int time_interval = 180;        /* Default time (180 seconds) */
        char *cp, *ep;
        socklen_t on = 1;
        struct sockaddr_in sasin;
        struct pollfd pfd[1];
        struct timeval delta, next, now;
        char *newuser = NULL;

        setprogname(argv[0]);

        if (getuid())
                errx(EXIT_FAILURE, "not super user");

        while ((ch = getopt(argc, argv, "i:u:")) != -1) {
                switch (ch) {
                case 'i':
                        time_interval = (int)strtol(optarg, &ep, 10);

                        switch (*ep) {
                        case '\0':
                                break;
                        case 'm':
                        case 'M':
                                /* Time in minutes. */
                                time_interval *= 60;
                                if (ep[1] == '\0')
                                        break;
                                /*FALLTHROUGH*/
                        default:
                                errx(1, "Invalid argument: `%s'", optarg);
                        }

                        if (time_interval <= 0)
                                errx(1, "Interval must be greater than 0");

                        if (time_interval > MAX_INTERVAL)
                                errx(1, "Interval cannot be greater than"
                                    " %d minutes", MAX_INTERVAL / 60);
                        break;

                case 'u':
                        newuser = optarg;
                        break;
                        
                default:
                        usage();        
                }
        }

        sp = getservbyname("who", "udp");
        if (sp == NULL)
                errx(EXIT_FAILURE, "udp/who: unknown service");
#ifndef DEBUG
        (void)daemon(1, 0);
        (void)pidfile(NULL);
#endif
        if (chdir(_PATH_RWHODIR) < 0)
                err(EXIT_FAILURE, "%s", _PATH_RWHODIR);
        (void)signal(SIGHUP, sighup);
        openlog(getprogname(), LOG_PID, LOG_DAEMON);
        /*
         * Establish host name as returned by system.
         */
        if (gethostname(myname, sizeof(myname) - 1) < 0) {
                syslog(LOG_ERR, "gethostname: %m");
                exit(EXIT_FAILURE);
        }
        myname[sizeof(myname) - 1] = '\0';
        if ((cp = strchr(myname, '.')) != NULL)
                *cp = '\0';
        (void)strncpy(mywd.wd_hostname, myname, sizeof(mywd.wd_hostname) - 1);
        getboottime();
        if ((s = socket(AF_INET, SOCK_DGRAM, 0)) < 0) {
                syslog(LOG_ERR, "socket: %m");
                exit(EXIT_FAILURE);
        }
        if (setsockopt(s, SOL_SOCKET, SO_BROADCAST, &on, sizeof(on)) < 0) {
                syslog(LOG_ERR, "setsockopt SO_BROADCAST: %m");
                exit(EXIT_FAILURE);
        }
        (void)memset(&sasin, 0, sizeof(sasin));
        sasin.sin_family = AF_INET;
        sasin.sin_port = sp->s_port;
        if (bind(s, (struct sockaddr *)&sasin, sizeof(sasin)) < 0) {
                syslog(LOG_ERR, "bind: %m");
                exit(EXIT_FAILURE);
        }
        if (!configure(s))
                exit(EXIT_FAILURE);

        if (newuser)
                if (!drop_privs(newuser))
                        exit(EXIT_FAILURE);

        send_host_information(s);
        delta.tv_sec = time_interval;
        delta.tv_usec = 0;
        gettimeofday(&now, NULL);
        timeradd(&now, &delta, &next);

        pfd[0].fd = s;
        pfd[0].events = POLLIN;

        for (;;) {
                int n;

                n = poll(pfd, 1, 1000);

                if (onsighup) {
                        onsighup = 0;
                        getboottime();
                }

                if (n == 1)
                        handleread(s);

                (void)gettimeofday(&now, NULL);
                if (timercmp(&now, &next, >)) {
                        send_host_information(s);
                        timeradd(&now, &delta, &next);
                }
        }

        /* NOTREACHED */
        return 0;
}

static void
sighup(int signo __unused)
{
        onsighup = 1;
}

static void
handleread(int s)
{
        struct sockaddr_in from;
        struct stat st;
        char path[64];
        struct whod wd;
        int cc, whod;
        socklen_t len = sizeof(from);

        cc = recvfrom(s, (char *)&wd, sizeof(struct whod), 0,
                (struct sockaddr *)&from, &len);
        if (cc <= 0) {
                if (cc < 0 && errno != EINTR)
                        syslog(LOG_WARNING, "recv: %m");
                return;
        }
        if (from.sin_port != sp->s_port) {
                syslog(LOG_WARNING, "%d: bad from port",
                        ntohs(from.sin_port));
                return;
        }
        if (cc < (int)WHDRSIZE) {
                syslog(LOG_WARNING, "Short packet from %s",
                        inet_ntoa(from.sin_addr));
                return;
        }

        if (wd.wd_vers != WHODVERSION)
                return;
        if (wd.wd_type != WHODTYPE_STATUS)
                return;
        /*
         * Ensure null termination of the name within the packet.
         * Otherwise we might overflow or read past the end.
         */
        wd.wd_hostname[sizeof(wd.wd_hostname)-1] = 0;
        if (!verify(wd.wd_hostname)) {
                syslog(LOG_WARNING, "malformed host name from %s",
                    inet_ntoa(from.sin_addr));
                return;
        }
        (void)snprintf(path, sizeof(path), "whod.%s", wd.wd_hostname);
        /*
         * Rather than truncating and growing the file each time,
         * use ftruncate if size is less than previous size.
         */
        whod = open(path, O_WRONLY | O_CREAT, 0644);
        if (whod < 0) {
                syslog(LOG_WARNING, "%s: %m", path);
                return;
        }
#if ENDIAN != BIG_ENDIAN
        {
                int i, n = (cc - WHDRSIZE) / sizeof(struct whoent);
                struct whoent *we;

                /* undo header byte swapping before writing to file */
                wd.wd_sendtime = ntohl(wd.wd_sendtime);
                for (i = 0; i < 3; i++)
                        wd.wd_loadav[i] = ntohl(wd.wd_loadav[i]);
                wd.wd_boottime = ntohl(wd.wd_boottime);
                we = wd.wd_we;
                for (i = 0; i < n; i++) {
                        we->we_idle = ntohl(we->we_idle);
                        we->we_utmp.out_time =
                            ntohl(we->we_utmp.out_time);
                        we++;
                }
        }
#endif
        wd.wd_recvtime = time(NULL);
        (void)write(whod, (char *)&wd, cc);
        if (fstat(whod, &st) < 0 || st.st_size > cc)
                (void)ftruncate(whod, cc);
        (void)close(whod);
}

/*
 * Check out host name for unprintables
 * and other funnies before allowing a file
 * to be created.  Sorry, but blanks aren't allowed.
 */
static int
verify(const char *name)
{
        int size = 0;

        while (*name) {
                if (!isascii((unsigned char)*name) ||
                    !(isalnum((unsigned char)*name) ||
                    ispunct((unsigned char)*name)))
                        return 0;
                name++, size++;
        }
        return size > 0;
}

static void
send_host_information(int s)
{
        struct neighbor *np;
        struct whoent *we = mywd.wd_we, *wlast;
        int i, cc, utmpent = 0;
        struct stat stb;
        double avenrun[3];
        time_t now;
        static struct utmpentry *ohead = NULL;
        struct utmpentry *ep;
        static int count = 0;

        now = time(NULL);
        if (count % 10 == 0)
                getboottime();
        count++;

        (void)getutentries(NULL, &ep);
        /* XXX probably should expose utmp mtime, check that instead */
        if (ep != ohead) {
                wlast = &mywd.wd_we[1024 / sizeof(struct whoent) - 1];
                for (; ep; ep = ep->next) {
                        (void)strncpy(we->we_utmp.out_line, ep->line,
                            sizeof(we->we_utmp.out_line));
                        (void)strncpy(we->we_utmp.out_name, ep->name,
                            sizeof(we->we_utmp.out_name));
                        we->we_utmp.out_time = htonl(ep->tv.tv_sec);
                        if (we >= wlast)
                                break;
                        we++;
                }
                utmpent = we - mywd.wd_we;
        }

        /*
         * The test on utmpent looks silly---after all, if no one is
         * logged on, why worry about efficiency?---but is useful on
         * (e.g.) compute servers.
         */
        if (utmpent && chdir(_PATH_DEV)) {
                syslog(LOG_ERR, "chdir(%s): %m", _PATH_DEV);
                exit(EXIT_FAILURE);
        }
        we = mywd.wd_we;
        for (i = 0; i < utmpent; i++) {
                if (stat(we->we_utmp.out_line, &stb) >= 0)
                        we->we_idle = htonl(now - stb.st_atime);
                we++;
        }
        (void)getloadavg(avenrun, sizeof(avenrun)/sizeof(avenrun[0]));
        for (i = 0; i < 3; i++)
                mywd.wd_loadav[i] = htonl((u_long)(avenrun[i] * 100));
        cc = (char *)we - (char *)&mywd;
        mywd.wd_sendtime = htonl(time(0));
        mywd.wd_vers = WHODVERSION;
        mywd.wd_type = WHODTYPE_STATUS;
        for (np = neighbors; np != NULL; np = np->n_next)
                (void)Sendto(s, (char *)&mywd, cc, 0,
                                np->n_addr, np->n_addrlen);
        if (utmpent && chdir(_PATH_RWHODIR)) {
                syslog(LOG_ERR, "chdir(%s): %m", _PATH_RWHODIR);
                exit(EXIT_FAILURE);
        }
}

static void
getboottime(void)
{
        int mib[2];
        size_t size;
        struct timespec tm;

        mib[0] = CTL_KERN;
        mib[1] = KERN_BOOTTIME;
        size = sizeof(tm);
        if (sysctl(mib, 2, &tm, &size, NULL, 0) == -1) {
                syslog(LOG_ERR, "cannot get boottime: %m");
                exit(EXIT_FAILURE);
        }
        mywd.wd_boottime = htonl(tm.tv_sec);
}

static void
quit(const char *msg)
{
        syslog(LOG_ERR, "%s", msg);
        exit(EXIT_FAILURE);
}

#define ROUNDUP(a) \
        ((a) > 0 ? (1 + (((a) - 1) | (sizeof(long) - 1))) : sizeof(long))
#define ADVANCE(x, n) ((char *)(x) + ROUNDUP((n)->sa_len))

static void
rt_xaddrs(void *cp, void *cplim, struct rt_addrinfo *rtinfo)
{
        struct sockaddr *sa;
        int i;

        (void)memset(rtinfo->rti_info, 0, sizeof(rtinfo->rti_info));
        for (i = 0; (i < RTAX_MAX) && (cp < cplim); i++) {
                if ((rtinfo->rti_addrs & (1 << i)) == 0)
                        continue;
                rtinfo->rti_info[i] = sa = (struct sockaddr *)cp;
                cp = ADVANCE(cp, sa);
        }
}

/*
 * Figure out device configuration and select
 * networks which deserve status information.
 */
static int
configure(int s)
{
        struct neighbor *np;
        struct if_msghdr *ifm;
        struct ifa_msghdr *ifam;
        struct sockaddr_dl *sdl;
        size_t needed;
        int mib[6], flags = 0, len;
        char *buf, *lim, *next;
        struct rt_addrinfo info;
        struct sockaddr_in dstaddr;

        mib[0] = CTL_NET;
        mib[1] = PF_ROUTE;
        mib[2] = 0;
        mib[3] = AF_INET;
        mib[4] = NET_RT_IFLIST;
        mib[5] = 0;
        if (sysctl(mib, 6, NULL, &needed, NULL, 0) < 0)
                quit("route-sysctl-estimate");
        if ((buf = malloc(needed)) == NULL)
                quit("malloc");
        if (sysctl(mib, 6, buf, &needed, NULL, 0) < 0)
                quit("actual retrieval of interface table");
        lim = buf + needed;

        sdl = NULL;             /* XXX just to keep gcc -Wall happy */
        for (next = buf; next < lim; next += ifm->ifm_msglen) {
                ifm = (struct if_msghdr *)next;
                if (ifm->ifm_type == RTM_IFINFO) {
                        sdl = (struct sockaddr_dl *)(ifm + 1);
                        flags = ifm->ifm_flags;
                        continue;
                }
                if ((flags & IFF_UP) == 0 ||
                    (flags & (IFF_BROADCAST|IFF_POINTOPOINT)) == 0)
                        continue;
                if (ifm->ifm_type != RTM_NEWADDR)
                        quit("out of sync parsing NET_RT_IFLIST");
                ifam = (struct ifa_msghdr *)ifm;
                info.rti_addrs = ifam->ifam_addrs;
                rt_xaddrs((ifam + 1), ifam->ifam_msglen + (char *)ifam, &info);
                /* gag, wish we could get rid of Internet dependencies */
                if (info.rti_info[RTAX_BRD] == NULL ||
                    info.rti_info[RTAX_BRD]->sa_family != AF_INET)
                        continue;
                (void)memcpy(&dstaddr, info.rti_info[RTAX_BRD],
                    sizeof(dstaddr));
#define IPADDR_SA(x) ((struct sockaddr_in *)(x))->sin_addr.s_addr
#define PORT_SA(x) ((struct sockaddr_in *)(x))->sin_port
                PORT_SA(&dstaddr) = sp->s_port;
                for (np = neighbors; np != NULL; np = np->n_next)
                        if (memcmp(sdl->sdl_data, np->n_name,
                                   sdl->sdl_nlen) == 0 &&
                            IPADDR_SA(np->n_addr) == IPADDR_SA(&dstaddr))
                                break;
                if (np != NULL)
                        continue;
                len = sizeof(*np) + dstaddr.sin_len + sdl->sdl_nlen + 1;
                np = (struct neighbor *)malloc(len);
                if (np == NULL)
                        quit("malloc of neighbor structure");
                (void)memset(np, 0, len);
                np->n_flags = flags;
                np->n_addr = (struct sockaddr *)(np + 1);
                np->n_addrlen = dstaddr.sin_len;
                np->n_name = np->n_addrlen + (char *)np->n_addr;
                np->n_next = neighbors;
                neighbors = np;
                (void)memcpy(np->n_addr, &dstaddr, np->n_addrlen);
                (void)memcpy(np->n_name, sdl->sdl_data, sdl->sdl_nlen);
        }
        free(buf);
        return (1);
}

#ifdef DEBUG
static ssize_t
Sendto(int s, const void *buf, size_t cc, int flags, const struct sockaddr *to,
    socklen_t tolen)
{
        struct whod *w = (struct whod *)buf;
        struct whoent *we;
        struct sockaddr_in *sasin = (struct sockaddr_in *)to;
        ssize_t ret;

        ret = sendto(s, buf, cc, flags, to, tolen);

        printf("sendto %s.%d\n", inet_ntoa(sasin->sin_addr),
            ntohs(sasin->sin_port));
        printf("hostname %s %s\n", w->wd_hostname,
           interval(ntohl(w->wd_sendtime) - ntohl(w->wd_boottime), "  up"));
        printf("load %4.2f, %4.2f, %4.2f\n",
            ntohl(w->wd_loadav[0]) / 100.0, ntohl(w->wd_loadav[1]) / 100.0,
            ntohl(w->wd_loadav[2]) / 100.0);
        cc -= WHDRSIZE;
        for (we = w->wd_we, cc /= sizeof(struct whoent); cc > 0; cc--, we++) {
                time_t t = ntohl(we->we_utmp.out_time);
                printf("%-8.8s %s:%s %.12s", we->we_utmp.out_name,
                    w->wd_hostname, we->we_utmp.out_line, ctime(&t)+4);
                we->we_idle = ntohl(we->we_idle) / 60;
                if (we->we_idle) {
                        if (we->we_idle >= 100*60)
                                we->we_idle = 100*60 - 1;
                        if (we->we_idle >= 60)
                                printf(" %2d", we->we_idle / 60);
                        else
                                printf("   ");
                        printf(":%02d", we->we_idle % 60);
                }
                printf("\n");
        }
        return ret;
}

static char *
interval(int time, const char *updown)
{
        static char resbuf[32];
        int days, hours, minutes;

        if (time < 0 || time > 3*30*24*60*60) {
                (void)snprintf(resbuf, sizeof(resbuf), "   %s ??:??", updown);
                return (resbuf);
        }
        minutes = (time + 59) / 60;             /* round to minutes */
        hours = minutes / 60; minutes %= 60;
        days = hours / 24; hours %= 24;
        if (days)
                (void)snprintf(resbuf, sizeof(resbuf), "%s %2d+%02d:%02d",
                    updown, days, hours, minutes);
        else
                (void)snprintf(resbuf, sizeof(resbuf), "%s    %2d:%02d",
                    updown, hours, minutes);
        return resbuf;
}
#endif

static int
drop_privs(char *newuser)
{
        struct passwd *pw;
        gid_t gidset[1];
        
        pw = getpwnam(newuser);
        if (pw == NULL) {
                syslog(LOG_ERR, "no user %.100s", newuser);
                return 0;
        }

        endpwent();     

        gidset[0] = pw->pw_gid;
        if (setgroups(1, gidset) == -1) {
                syslog(LOG_ERR, "setgroups: %m");
                return 0;
        }

        if (setgid(pw->pw_gid) == -1) {
                syslog(LOG_ERR, "setgid: %m");
                return 0;
        }

        if (setuid(pw->pw_uid) == -1) {
                syslog(LOG_ERR, "setuid: %m");
                return 0;
        }

        return 1;
}

static void
usage(void)
{
        (void)fprintf(stderr, "Usage: %s [-i interval] [-u user]\n", getprogname());
        exit(EXIT_FAILURE);
}