/*
 * Copyright 2005 Sun Microsystems, Inc.  All rights reserved.
 * Use is subject to license terms.
 */

/*
 * Copyright (c) 1983, 1984, 1985, 1986, 1987, 1988, 1989 AT&T
 * All Rights Reserved.
 */

/*
 * Copyright (c) 1980 Regents of the University of California.
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms are permitted provided
 * that: (1) source distributions retain this entire copyright notice and
 * comment, and (2) distributions including binaries display the following
 * acknowledgement: ``This product includes software developed by the
 * University of California, Berkeley and its contributors'' in the
 * documentation or other materials provided with the distribution and in
 * all advertising materials mentioning features or use of this software.
 * 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 ``AS IS'' AND WITHOUT ANY EXPRESS OR IMPLIED
 * WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED WARRANTIES OF
 * MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE.
 */

#include <sys/types.h>
#include <sys/socket.h>
#include <sys/stat.h>
#include <sys/wait.h>
#include <sys/file.h>
#include <fcntl.h>
#include <ctype.h>
#include <string.h>

#include <netinet/in.h>

#include <stdio.h>
#include <sys/ttold.h>
#include <utmpx.h>
#include <signal.h>
#include <errno.h>
#include <sys/param.h>  /* for MAXHOSTNAMELEN */
#include <netdb.h>
#include <syslog.h>
#include <sys/ioctl.h>
#include <pwd.h>

/*
 * comsat
 */


#ifndef UTMPX_FILE
#define UTMPX_FILE "/etc/utmpx"
#endif  /* UTMPX_FILE */

int     debug = 0;
#define dsyslog if (debug) syslog

struct  sockaddr_in sin = { AF_INET };

char    hostname[MAXHOSTNAMELEN];
struct  utmpx *utmp = NULL;
int     nutmp;
int     uf;
unsigned utmpmtime = 0;                 /* last modification time for utmp */
unsigned utmpsize = 0;                  /* last malloced size for utmp */
time_t  lastmsgtime;

#ifndef SYSV
int     reapchildren();
#else

#define rindex strrchr
#define index strchr
#define signal(s, f)    sigset((s), (f))

#ifndef sigmask
#define sigmask(m)      (1 << ((m)-1))
#endif

#define set2mask(setp)  ((setp)->__sigbits[0])
#define mask2set(mask, setp) \
        ((mask) == -1 ? sigfillset(setp) : (((setp)->__sigbits[0]) = (mask)))

static int
sigsetmask(int mask)
{
        sigset_t oset;
        sigset_t nset;

        (void) sigprocmask(0, (sigset_t *)0, &nset);
        mask2set(mask, &nset);
        (void) sigprocmask(SIG_SETMASK, &nset, &oset);
        return (set2mask(&oset));
}

static int
sigblock(int mask)
{
        sigset_t oset;
        sigset_t nset;

        (void) sigprocmask(0, (sigset_t *)0, &nset);
        mask2set(mask, &nset);
        (void) sigprocmask(SIG_BLOCK, &nset, &oset);
        return (set2mask(&oset));
}

#endif /* SYSV */


#define MAXIDLE 120
#define NAMLEN (sizeof (uts[0].ut_name) + 1)

void jkfprintf(FILE *tp, char *name, int mbox, int offset);
void mailfor(char *name);
void notify(struct utmpx *utp, int offset);
void onalrm(int sig);

int
main(int argc, char *argv[])
{
        int cc;
        char buf[BUFSIZ];
        char msgbuf[100];
        struct sockaddr_in from;
        socklen_t fromlen;
        int c;
        extern int optind;
        extern int getopt();
        extern char *optarg;

        openlog("comsat", 0, LOG_DAEMON);

        while ((c = getopt(argc, argv, "d")) != -1) {
                switch ((char)c) {
                case'd':
                        debug++;
                        break;
                default:
                        syslog(LOG_ERR, "invalid argument %s", argv[optind]);
                        exit(1);
                }
        }

        /* verify proper invocation */
        fromlen = (socklen_t)sizeof (from);
        if (getsockname(0, (struct sockaddr *)&from, &fromlen) < 0) {
                fprintf(stderr, "%s: ", argv[0]);
                perror("getsockname");
                _exit(1);
        }

#ifdef SYSV
        chdir("/var/mail");
#else
        chdir("/var/spool/mail");
#endif /* SYSV */
        if ((uf = open(UTMPX_FILE, 0)) < 0) {
                syslog(LOG_ERR, "%s: %m", UTMPX_FILE);
                (void) recv(0, msgbuf, sizeof (msgbuf) - 1, 0);
                exit(1);
        }
        (void) time(&lastmsgtime);
        (void) gethostname(hostname, sizeof (hostname));
        onalrm(0);
        (void) signal(SIGALRM, onalrm);
        (void) signal(SIGTTOU, SIG_IGN);
#ifndef SYSV
        (void) signal(SIGCHLD, reapchildren);
#else
        (void) signal(SIGCHLD, SIG_IGN); /* no zombies */
#endif /* SYSV */
        for (;;) {
                cc = recv(0, msgbuf, sizeof (msgbuf) - 1, 0);
                if (cc <= 0) {
                        if (errno != EINTR)
                                sleep(1);
                        errno = 0;
                        continue;
                }
                if (nutmp == 0)                 /* no users (yet) */
                        continue;
                sigblock(sigmask(SIGALRM));
                msgbuf[cc] = 0;
                (void) time(&lastmsgtime);
                mailfor(msgbuf);
                sigsetmask(0);
        }
}

#ifndef SYSV
reapchildren()
{

        while (wait3((struct wait *)0, WNOHANG, (struct rusage *)0) > 0)
                ;
}
#endif /* SYSV */

/* ARGSUSED */
void
onalrm(int sig)
{
        struct stat statbf;
        time_t now;

        (void) time(&now);
        if ((ulong_t)now - (ulong_t)lastmsgtime >= MAXIDLE)
                exit(0);
        dsyslog(LOG_DEBUG, "alarm\n");
        alarm(15);
        fstat(uf, &statbf);
        if (statbf.st_mtime > utmpmtime) {
                dsyslog(LOG_DEBUG, " changed\n");
                utmpmtime = statbf.st_mtime;
                if (statbf.st_size > utmpsize) {
                        utmpsize = statbf.st_size + 10 * sizeof (struct utmpx);
                        if (utmp)
                                utmp = (struct utmpx *)realloc(utmp, utmpsize);
                        else
                                utmp = (struct utmpx *)malloc(utmpsize);
                        if (! utmp) {
                                dsyslog(LOG_DEBUG, "malloc failed\n");
                                exit(1);
                        }
                }
                lseek(uf, 0, 0);
                nutmp = read(uf, utmp, statbf.st_size)/sizeof (struct utmpx);
        } else
                dsyslog(LOG_DEBUG, " ok\n");
}

void
mailfor(char *name)
{
        struct utmpx *utp = &utmp[nutmp];
        char *cp;
        char *rindex();
        int offset;

        /*
         * Don't bother doing anything if nobody is
         * logged into the system.
         */
        if (utmp == NULL || nutmp == 0)
                return;
        dsyslog(LOG_DEBUG, "mailfor %s\n", name);
        cp = name;
        while (*cp && *cp != '@')
                cp++;
        if (*cp == 0) {
                dsyslog(LOG_DEBUG, "bad format\n");
                return;
        }
        *cp = 0;
        offset = atoi(cp+1);
        while (--utp >= utmp)
                if (utp->ut_type == USER_PROCESS &&
                    strncmp(utp->ut_name, name, sizeof (utmp[0].ut_name)) == 0)
                        notify(utp, offset);
}

char    *cr;

void
notify(struct utmpx *utp, int offset)
{
        FILE *tp;
        struct sgttyb gttybuf;
        char tty[sizeof (utmp[0].ut_line) + 5];
        char name[sizeof (utmp[0].ut_name) + 1];
        struct stat stb, stl;
        time_t timep[2];
        struct passwd *pwd;
        int fd, mbox;


        strcpy(tty, "/dev/");
        strncat(tty, utp->ut_line, sizeof (utp->ut_line));
        dsyslog(LOG_DEBUG, "notify %s on %s\n", utp->ut_name, tty);
        if (stat(tty, &stb) == -1) {
                dsyslog(LOG_DEBUG, "can't stat tty\n");
                return;
        }
        if ((stb.st_mode & 0100) == 0) {
                dsyslog(LOG_DEBUG, "wrong mode\n");
                return;
        }
        if (fork())
                return;
        signal(SIGALRM, SIG_DFL);
        alarm(30);

        strncpy(name, utp->ut_name, sizeof (utp->ut_name));
        name[sizeof (name) - 1] = '\0';

        /*
         * Do all operations that check protections as the user who
         * will be getting the biff.
         */
        if ((pwd = getpwnam(name)) == (struct passwd *)-1) {
                dsyslog(LOG_DEBUG, "getpwnam failed\n");
                exit(1);
        }
        if (setuid(pwd->pw_uid) == -1) {
                dsyslog(LOG_DEBUG, "setuid failed\n");
                exit(1);
        }

        /*
         * We need to make sure that the tty listed in the utmp
         * file really is a tty device so that a corrupted utmp
         * file doesn't cause us to over-write a real file.
         */
        if ((fd = open(tty, O_RDWR)) == -1) {
                dsyslog(LOG_DEBUG, "can't open tty");
                exit(1);
        }
        if (isatty(fd) == 0) {
                dsyslog(LOG_DEBUG, "line listed in utmp file is not a tty\n");
                exit(1);
        }

        /*
         * For the case where the user getting the biff is root,
         * we need to make sure that the tty we will be sending
         * the biff to is also owned by root.
         *
         * Check after open, to prevent race on open.
         */

        if (fstat(fd, &stb) != 0 || stb.st_uid != pwd->pw_uid) {
                dsyslog(LOG_DEBUG,
                    "tty is not owned by user getting the biff\n");
                exit(1);
        }

        /*
         * Prevent race by doing fdopen on fd, not fopen
         * Fopen opens w/ O_CREAT, which is dangerous too
         */
        if ((tp = fdopen(fd, "w")) == 0) {
                dsyslog(LOG_DEBUG, "fdopen failed\n");
                exit(-1);
        }

        if (ioctl(fd, TIOCGETP, &gttybuf) == -1) {
                dsyslog(LOG_DEBUG, "ioctl TIOCGETP failed\n");
                exit(1);
        }
        cr = (gttybuf.sg_flags&CRMOD) && !(gttybuf.sg_flags&RAW) ? "" : "\r";
        fprintf(tp, "%s\n\007New mail for %s@%.*s\007 has arrived:%s\n",
            cr, name, sizeof (hostname), hostname, cr);
        fprintf(tp, "----%s\n", cr);

        if ((mbox = open(name, O_RDONLY)) == -1) {
                dsyslog(LOG_DEBUG, "can't open mailbox for %s", name);
                exit(1);
        }
        /*
         * In case of a worldwritable mail spool directory, we must take
         * care we don't open and read from the wrong file.
         */
        if (fstat(mbox, &stb) == -1 || lstat(name, &stl) == -1) {
                dsyslog(LOG_DEBUG, "stat() failed on mail file\n");
                exit(1);
        }

        /*
         * Here we make sure that the file wasn't a hardlink or softlink
         * while we opened it and that it wasn't changed afterwards
         */
        if (!S_ISREG(stl.st_mode) ||
            stl.st_dev != stb.st_dev ||
            stl.st_ino != stb.st_ino ||
            stl.st_uid != pwd->pw_uid ||
            stb.st_nlink != 1) {
                dsyslog(LOG_DEBUG, "mail spool file must be plain file\n");
                exit(1);
        }

        timep[0] = stb.st_atime;
        timep[1] = stb.st_mtime;
        jkfprintf(tp, name, mbox, offset);
        utime(name, timep);
        exit(0);
}

void
jkfprintf(FILE *tp, char *name, int mbox, int offset)
{
        FILE *fi;
        int linecnt, charcnt;
        char line[BUFSIZ];
        int inheader;

        dsyslog(LOG_DEBUG, "HERE %s's mail starting at %d\n",
            name, offset);
        if ((fi = fdopen(mbox, "r")) == NULL) {
                dsyslog(LOG_DEBUG, "Cant read the mail\n");
                return;
        }

        fseek(fi, offset, L_SET);

        /*
         * Print the first 7 lines or 560 characters of the new mail
         * (whichever comes first).  Skip header crap other than
         * From, Subject, To, and Date.
         */
        linecnt = 7;
        charcnt = 560;
        inheader = 1;


        while (fgets(line, sizeof (line), fi) != NULL) {
                char *cp;
                char *index();
                int cnt;
                int i;

                if (linecnt <= 0 || charcnt <= 0) {
                        fprintf(tp, "...more...%s\n", cr);
                        return;
                }
                if (strncmp(line, "From ", 5) == 0)
                        continue;
                if (inheader && (line[0] == ' ' || line[0] == '\t'))
                        continue;
                cp = index(line, ':');
                if (cp == 0 || (index(line, ' ') && index(line, ' ') < cp))
                        inheader = 0;
                else
                        cnt = cp - line;
                if (inheader &&
                    strncmp(line, "Date", cnt) &&
                    strncmp(line, "From", cnt) &&
                    strncmp(line, "Subject", cnt) &&
                    strncmp(line, "To", cnt))
                        continue;
                cp = index(line, '\n');
                if (cp)
                        *cp = '\0';

                for (i = strlen(line); i-- > 0; )
                        if (!isprint(line[i]))
                                line[i] = ' ';


                fprintf(tp, "%s%s\n", line, cr);
                linecnt--, charcnt -= strlen(line);
        }
        fprintf(tp, "----%s\n", cr);
}