/*      $NetBSD: comsat.c,v 1.42 2010/05/29 23:12:30 dholland Exp $     */

/*
 * Copyright (c) 1980, 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) 1980, 1993\
 The Regents of the University of California.  All rights reserved.");
#if 0
static char sccsid[] = "from: @(#)comsat.c      8.1 (Berkeley) 6/4/93";
#else
__RCSID("$NetBSD: comsat.c,v 1.42 2010/05/29 23:12:30 dholland Exp $");
#endif
#endif /* not lint */

#include <sys/param.h>
#include <sys/socket.h>
#include <sys/stat.h>
#include <sys/file.h>
#include <sys/wait.h>

#include <netinet/in.h>

#include <errno.h>
#include <netdb.h>
#include <paths.h>
#include <pwd.h>
#include <err.h>
#include <signal.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <syslog.h>
#include <termios.h>
#include <time.h>
#include <vis.h>
#include <unistd.h>
#ifdef SUPPORT_UTMP
#include <utmp.h>
#endif
#ifdef SUPPORT_UTMPX
#include <utmpx.h>
#endif

#include "utmpentry.h"

#if !defined(SUPPORT_UTMP) && !defined(SUPPORT_UTMPX)
        #error "SUPPORT_UTMP and/or SUPPORT_UTMPX must be defined"
#endif

#define dsyslog if (debug) syslog

#define MAXIDLE 120

static int      logging;
static int      debug;
static char     hostname[MAXHOSTNAMELEN + 1];
static int      nutmp;
static struct   utmpentry *utmp = NULL;
static time_t   lastmsgtime;
static volatile sig_atomic_t needupdate;

int main(int, char *[]);
static void jkfprintf(FILE *, const char *, off_t, const char *);
static void mailfor(char *);
static void notify(const struct utmpentry *, off_t);
static void onalrm(int);
static void checkutmp(void);

int
main(int argc, char *argv[])
{
        struct sockaddr_storage from;
        int cc, ch;
        socklen_t fromlen;
        char msgbuf[100];
        sigset_t nsigset, osigset;

        /* verify proper invocation */
        fromlen = sizeof(from);
        if (getsockname(0, (struct sockaddr *)(void *)&from, &fromlen) == -1)
                err(1, "getsockname");

        openlog("comsat", LOG_PID, LOG_DAEMON);
        while ((ch = getopt(argc, argv, "l")) != -1)
                switch (ch) {
                case 'l':
                        logging = 1;
                        break;
                default:
                        syslog(LOG_ERR, "Usage: %s [-l]", getprogname());
                        exit(1);
                }
        if (chdir(_PATH_MAILDIR) == -1) {
                syslog(LOG_ERR, "chdir: %s: %m", _PATH_MAILDIR);
                (void)recv(0, msgbuf, sizeof(msgbuf) - 1, 0);
                exit(1);
        }
        (void)time(&lastmsgtime);
        (void)gethostname(hostname, sizeof(hostname));
        hostname[sizeof(hostname) - 1] = '\0';
        (void)signal(SIGALRM, onalrm);
        (void)signal(SIGTTOU, SIG_IGN);
        (void)signal(SIGCHLD, SIG_IGN);
        (void)sigemptyset(&nsigset);
        (void)sigaddset(&nsigset, SIGALRM);
        if (sigprocmask(SIG_SETMASK, NULL, &osigset) == -1) {
                syslog(LOG_ERR, "sigprocmask get failed (%m)");
                exit(1);
        }
        needupdate = 1;
        for (;;) {
                cc = recv(0, msgbuf, sizeof(msgbuf) - 1, 0);
                if (cc <= 0) {
                        if (errno != EINTR)
                                sleep(1);
                        errno = 0;
                        checkutmp();
                        continue;
                } else
                        checkutmp();
                if (!nutmp)             /* no one has logged in yet */
                        continue;
                if (sigprocmask(SIG_SETMASK, &nsigset, NULL) == -1) {
                        syslog(LOG_ERR, "sigprocmask set failed (%m)");
                        exit(1);
                }
                msgbuf[cc] = '\0';
                (void)time(&lastmsgtime);
                mailfor(msgbuf);
                if (sigprocmask(SIG_SETMASK, &osigset, NULL) == -1) {
                        syslog(LOG_ERR, "sigprocmask restore failed (%m)");
                        exit(1);
                }
        }
}

static void
/*ARGSUSED*/
onalrm(int signo)
{
        needupdate = 1;
}

static void
checkutmp(void)
{
        if (!needupdate)
                return;
        needupdate = 0;

        if (time(NULL) - lastmsgtime >= MAXIDLE)
                exit(0);
        (void)alarm((u_int)15);
        nutmp = getutentries(NULL, &utmp);
}

static void
mailfor(char *name)
{
        struct utmpentry *ep;
        char *cp, *fn;
        off_t offset;
        intmax_t val;

        if (!(cp = strchr(name, '@')))
                return;
        *cp = '\0';
        errno = 0;
        offset = val = strtoimax(cp + 1, &fn, 10);
        if (errno == ERANGE || offset != val)
                return;
        if (fn && *fn && *fn != '\n') {
                /*
                 * Procmail sends messages to comsat with a trailing colon
                 * and a pathname to the folder where the new message was
                 * deposited.  Since we can't reliably open only regular
                 * files, we need to ignore these.  With one exception:
                 * if it mentions the user's system mailbox.
                 */
                char maildir[MAXPATHLEN];
                int l = snprintf(maildir, sizeof(maildir), ":%s/%s",
                    _PATH_MAILDIR, name);
                if (l >= (int)sizeof(maildir) || strcmp(maildir, fn) != 0)
                        return;
        }
        for (ep = utmp; ep != NULL; ep = ep->next)
                if (strcmp(ep->name, name) == 0)
                        notify(ep, offset);
}

static void
notify(const struct utmpentry *ep, off_t offset)
{
        FILE *tp;
        struct passwd *p;
        struct stat stb;
        struct termios ttybuf;
        char tty[sizeof(_PATH_DEV) + sizeof(ep->line) + 1];
        const char *cr = ep->line;

        if (strncmp(cr, "pts/", 4) == 0)
                cr += 4;
        if (strchr(cr, '/')) {
                /* A slash is an attempt to break security... */
                syslog(LOG_AUTH | LOG_NOTICE, "Unexpected `/' in `%s'",
                    ep->line);
                return;
        }
        (void)snprintf(tty, sizeof(tty), "%s%s", _PATH_DEV, ep->line);
        if (stat(tty, &stb) == -1 || !(stb.st_mode & S_IEXEC)) {
                dsyslog(LOG_DEBUG, "%s: wrong mode on %s", ep->name, tty);
                return;
        }
        dsyslog(LOG_DEBUG, "notify %s on %s", ep->name, tty);
        switch (fork()) {
        case -1:
                syslog(LOG_NOTICE, "fork failed (%m)");
                return;
        case 0:
                break;
        default:
                return;
        }
        (void)signal(SIGALRM, SIG_DFL);
        (void)alarm(30);
        if ((tp = fopen(tty, "w")) == NULL) {
                dsyslog(LOG_ERR, "open `%s' (%s)", tty, strerror(errno));
                _exit(1);
        }
        if (tcgetattr(fileno(tp), &ttybuf) == -1) {
                dsyslog(LOG_ERR, "tcgetattr `%s' (%s)", tty, strerror(errno));
                _exit(1);
        }
        cr = (ttybuf.c_oflag & ONLCR) && (ttybuf.c_oflag & OPOST) ?
            "\n" : "\n\r";
        /* Set uid/gid/groups to user's in case mail drop is on nfs */
        if ((p = getpwnam(ep->name)) == NULL ||
            initgroups(p->pw_name, p->pw_gid) == -1 ||
            setgid(p->pw_gid) == -1 ||
            setuid(p->pw_uid) == -1)
                _exit(1);

        if (logging)
                syslog(LOG_INFO, "biff message for %s", ep->name);

        (void)fprintf(tp, "%s\007New mail for %s@%.*s\007 has arrived:%s----%s",
            cr, ep->name, (int)sizeof(hostname), hostname, cr, cr);
        jkfprintf(tp, ep->name, offset, cr);
        (void)fclose(tp);
        _exit(0);
}

static void
jkfprintf(FILE *tp, const char *name, off_t offset, const char *cr)
{
        FILE *fi;
        int linecnt, charcnt, inheader;
        char line[BUFSIZ], visline[BUFSIZ * 4 + 1], *nl;

        if ((fi = fopen(name, "r")) == NULL)
                return;

        (void)fseeko(fi, offset, SEEK_SET);
        /*
         * Print the first 7 lines or 560 characters of the new mail
         * (whichever comes first).  Skip header crap other than
         * From and Subject.
         */
        linecnt = 7;
        charcnt = 560;
        inheader = 1;
        while (fgets(line, sizeof(line), fi) != NULL) {
                line[sizeof(line) - 1] = '\0';
                if (inheader) {
                        if (line[0] == '\n') {
                                inheader = 0;
                                continue;
                        }
                        if (line[0] == ' ' || line[0] == '\t' ||
                            (strncasecmp(line, "From:", 5) &&
                            strncasecmp(line, "Subject:", 8)))
                                continue;
                }
                if (strncmp(line, "From ", 5) == 0) {
                        (void)fprintf(tp, "----%s", cr);
                        (void)fclose(fi);
                        return;
                }
                if (linecnt <= 0 || charcnt <= 0) {
                        (void)fprintf(tp, "...more...%s", cr);
                        (void)fclose(fi);
                        return;
                }
                if ((nl = strchr(line, '\n')) != NULL)
                        *nl = '\0';
                /* strip weird stuff so can't trojan horse stupid terminals */
                (void)strvis(visline, line, VIS_CSTYLE);
                (void)fputs(visline, tp);
                (void)fputs(cr, tp);
                --linecnt;
        }
        (void)fprintf(tp, "----%s\n", cr);
        (void)fclose(fi);
}