/*
 * CDDL HEADER START
 *
 * The contents of this file are subject to the terms of the
 * Common Development and Distribution License, Version 1.0 only
 * (the "License").  You may not use this file except in compliance
 * with the License.
 *
 * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
 * or http://www.opensolaris.org/os/licensing.
 * See the License for the specific language governing permissions
 * and limitations under the License.
 *
 * When distributing Covered Code, include this CDDL HEADER in each
 * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
 * If applicable, add the following below this CDDL HEADER, with the
 * fields enclosed by brackets "[]" replaced with your own identifying
 * information: Portions Copyright [yyyy] [name of copyright owner]
 *
 * CDDL HEADER END
 */
/*      Copyright (c) 1984, 1986, 1987, 1988, 1989 AT&T */
/*        All Rights Reserved   */


/*
 * Copyright 2004 Sun Microsystems, Inc.  All rights reserved.
 * Use is subject to license terms.
 * Copyright (c) 2016 by Delphix. All rights reserved.
 * Copyright (c) 2018, Joyent, Inc.
 */

#include        <ctype.h>
#include        <string.h>
#include        <stdio.h>
#include        <signal.h>
#include        <sys/wait.h>
#include        <sys/types.h>
#include        <sys/stat.h>
#include        <sys/utsname.h>
#include        <stdlib.h>
#include        <unistd.h>
#include        <time.h>
#include        <utmpx.h>
#include        <pwd.h>
#include        <fcntl.h>
#include        <stdarg.h>
#include        <locale.h>
#include        <stdlib.h>
#include        <limits.h>
#include        <wctype.h>
#include        <errno.h>
#include        <syslog.h>

#define         TRUE    1
#define         FALSE   0
#define         FAILURE -1
#define         DATE_FMT        "%a %b %e %H:%M:%S"
#define         UTMP_HACK  /* work around until utmpx is world writable */
/*
 *      DATE-TIME format
 *  %a  abbreviated weekday name
 *  %b  abbreviated month name
 *  %e  day of month
 *  %H  hour - 24 hour clock
 *  %M  minute
 *  %S  second
 *
 */

static int permit1(int);
static int permit(char *);
static int readcsi(int, char *, int);
static void setsignals();
static void shellcmd(char *);
static void openfail();
static void eof();

static struct   utsname utsn;

static FILE     *fp;    /* File pointer for receipient's terminal */
static char *rterm, *receipient; /* Pointer to receipient's terminal & name */
static char *thissys;

int
main(int argc, char **argv)
{
        int i;
        struct utmpx *ubuf;
        static struct utmpx self;
        char ownname[sizeof (self.ut_user) + 1];
        static char rterminal[sizeof ("/dev/") + sizeof (self.ut_line)] =
            "/dev/";
        extern char *rterm, *receipient;
        char *terminal, *ownterminal, *oterminal;
        short count;
        extern FILE *fp;
        char input[134+MB_LEN_MAX];
        char *ptr;
        time_t tod;
        char time_buf[40];
        struct passwd *passptr;
        char badterm[20][20];
        int bad = 0;
        uid_t   myuid;
        char *bp;
        int n;
        wchar_t wc;
        int c;
        int newline;

        (void) setlocale(LC_ALL, "");
#if !defined(TEXT_DOMAIN)
#define TEXT_DOMAIN "SYS_TEST"
#endif
        (void) textdomain(TEXT_DOMAIN);

        while ((c = getopt(argc, argv, "")) != EOF)
                switch (c) {
                        case '?':
                                (void) fprintf(stderr, "Usage: write %s\n",
                                gettext("user_name [terminal]"));
                                exit(2);
                }
        myuid = geteuid();
        uname(&utsn);
        thissys = utsn.nodename;

/*      Set "rterm" to location where receipient's terminal will go.    */

        rterm = &rterminal[sizeof ("/dev/") - 1];
        terminal = NULL;

        if (--argc <= 0) {
            (void) fprintf(stderr, "Usage: write %s\n",
                gettext("user_name [terminal]"));
            exit(1);
            }
        else
            {
            receipient = *++argv;
            }

/*      Was a terminal name supplied?  If so, save it.                  */

        if (--argc > 1) {
            (void) fprintf(stderr, "Usage: write %s\n",
                gettext("user_name [terminal]"));
            exit(1);
        } else {
            terminal = *++argv;
        }

/*      One of the standard file descriptors must be attached to a      */
/*      terminal in "/dev".                                             */

        if ((ownterminal = ttyname(fileno(stdin))) == NULL &&
            (ownterminal = ttyname(fileno(stdout))) == NULL &&
            (ownterminal = ttyname(fileno(stderr))) == NULL) {
                (void) fprintf(stderr,
                        gettext("I cannot determine your terminal name."
                                        " No reply possible.\n"));
                ownterminal = "/dev/???";
        }

        /*
         * Set "ownterminal" past the "/dev/" at the beginning of
         * the device name.
         */
        oterminal = ownterminal + sizeof ("/dev/")-1;

        /*
         * Scan through the "utmpx" file for your own entry and the
         * entry for the person we want to send to.
         */
        for (self.ut_pid = 0, count = 0; (ubuf = getutxent()) != NULL; ) {
        /* Is this a USER_PROCESS entry? */

            if (ubuf->ut_type == USER_PROCESS) {
/*      Is it our entry?  (ie.  The line matches ours?)                 */

                if (strncmp(&ubuf->ut_line[0], oterminal,
                    sizeof (ubuf->ut_line)) == 0) self = *ubuf;

/*      Is this the person we want to send to?                          */

                if (strncmp(receipient, &ubuf->ut_user[0],
                    sizeof (ubuf->ut_user)) == 0) {
/*      If a terminal name was supplied, is this login at the correct   */
/*      terminal?  If not, ignore.  If it is right place, copy over the */
/*      name.                                                           */

                    if (terminal != NULL) {
                        if (strncmp(terminal, &ubuf->ut_line[0],
                            sizeof (ubuf->ut_line)) == 0) {
                            strlcpy(rterm, &ubuf->ut_line[0],
                                sizeof (rterminal) - (rterm - rterminal));
                            if (myuid && !permit(rterminal)) {
                                bad++;
                                rterm[0] = '\0';
                            }
                            }
                    }

/*      If no terminal was supplied, then take this terminal if no      */
/*      other terminal has been encountered already.                    */

                    else
                    {
/*      If this is the first encounter, copy the string into            */
/*      "rterminal".                                                    */

                        if (*rterm == '\0') {
                            strlcpy(rterm, &ubuf->ut_line[0],
                                sizeof (rterminal) - (rterm - rterminal));
                            if (myuid && !permit(rterminal)) {
                                if (bad < 20) {
                                        strlcpy(badterm[bad++], rterm,
                                            sizeof (badterm[bad++]));
                                }
                                rterm[0] = '\0';
                            } else if (bad > 0) {
                                (void) fprintf(stderr,
                                gettext(
                                "%s is logged on more than one place.\n"
        "You are connected to \"%s\".\nOther locations are:\n"),
                                    receipient, rterm);
                                for (i = 0; i < bad; i++)
                                    (void) fprintf(stderr, "%s\n", badterm[i]);
                            }
                        }

/*      If this is the second terminal, print out the first.  In all    */
/*      cases of multiple terminals, list out all the other terminals   */
/*      so the user can restart knowing what their choices are.         */

                        else if (terminal == NULL) {
                            if (count == 1 && bad == 0) {
                                (void) fprintf(stderr,
                                gettext(
                                "%s is logged on more than one place.\n"
        "You are connected to \"%s\".\nOther locations are:\n"),
                                    receipient, rterm);
                            }
                            fwrite(&ubuf->ut_line[0], sizeof (ubuf->ut_line),
                                1, stderr);
                            (void) fprintf(stderr, "\n");
                            }

                        count++;
                    }                   /* End of "else" */
                    }                   /* End of "else if (strncmp" */
            }                   /* End of "if (USER_PROCESS" */
            }           /* End of "for(count=0" */

/*      Did we find a place to talk to?  If we were looking for a       */
/*      specific spot and didn't find it, complain and quit.            */

        if (terminal != NULL && *rterm == '\0') {
            if (bad > 0) {
                (void) fprintf(stderr, gettext("Permission denied.\n"));
                exit(1);
                } else {
#ifdef UTMP_HACK
                if (strlcat(rterminal, terminal, sizeof (rterminal)) >=
                    sizeof (rterminal)) {
                        (void) fprintf(stderr,
                            gettext("Terminal name too long.\n"));
                        exit(1);
                }
                if (self.ut_pid == 0) {
                        if ((passptr = getpwuid(getuid())) == NULL) {
                            (void) fprintf(stderr,
                                gettext("Cannot determine who you are.\n"));
                            exit(1);
                        }
                        (void) strlcpy(&ownname[0], &passptr->pw_name[0],
                            sizeof (ownname));
                } else {
                        (void) strlcpy(&ownname[0], self.ut_user,
                            sizeof (self.ut_user));
                }
                if (!permit(rterminal)) {
                        (void) fprintf(stderr,
                                gettext("%s permission denied\n"), terminal);
                        exit(1);
                }
#else
                (void) fprintf(stderr, gettext("%s is not at \"%s\".\n"),
                        receipient, terminal);
                exit(1);
#endif  /* UTMP_HACK */
            }
            }

/*      If we were just looking for anyplace to talk and didn't find    */
/*      one, complain and quit.                                         */
/*      If permissions prevent us from sending to this person - exit    */

        else if (*rterm == '\0') {
            if (bad > 0)
                (void) fprintf(stderr, gettext("Permission denied.\n"));
            else
                (void) fprintf(stderr,
                        gettext("%s is not logged on.\n"), receipient);
            exit(1);
            }

/*      Did we find our own entry?                                      */

        else if (self.ut_pid == 0) {
/*      Use the user id instead of utmp name if the entry in the        */
/*      utmp file couldn't be found.                                    */

            if ((passptr = getpwuid(getuid())) == (struct passwd *)NULL) {
                (void) fprintf(stderr,
                        gettext("Cannot determine who you are.\n"));
                exit(1);
            }
            strncpy(&ownname[0], &passptr->pw_name[0], sizeof (ownname));
            }
        else
            {
            strncpy(&ownname[0], self.ut_user, sizeof (self.ut_user));
            }
        ownname[sizeof (ownname)-1] = '\0';

        if (!permit1(1))
                (void) fprintf(stderr,
                gettext("Warning: You have your terminal set to \"mesg -n\"."
                    " No reply possible.\n"));
/*      Close the utmpx files.                                          */

        endutxent();

/*      Try to open up the line to the receipient's terminal.           */

        signal(SIGALRM, openfail);
        alarm(5);
        fp = fopen(&rterminal[0], "w");
        alarm(0);

/*      Make sure executed subshell doesn't inherit this fd - close-on-exec */

        if (fcntl(fileno(fp), F_SETFD, FD_CLOEXEC) < 0)  {
                perror("fcntl(F_SETFD)");
                exit(1);
        }

/*      Catch signals SIGHUP, SIGINT, SIGQUIT, and SIGTERM, and send    */
/*      <EOT> message to receipient before dying away.                  */

        setsignals(eof);

/*      Get the time of day, convert it to a string and throw away the  */
/*      year information at the end of the string.                      */

        time(&tod);
        (void) strftime(time_buf, sizeof (time_buf),
            dcgettext(NULL, DATE_FMT, LC_TIME), localtime(&tod));

        (void) fprintf(fp,
        gettext("\n\007\007\007\tMessage from %s on %s (%s) [ %s ] ...\n"),
            &ownname[0], thissys, oterminal, time_buf);
        fflush(fp);
        (void) fprintf(stderr, "\007\007");

/*      Get input from user and send to receipient unless it begins     */
/*      with a !, when it is to be a shell command.                     */
        newline = 1;
        while ((i = readcsi(0, &input[0], sizeof (input))) > 0) {
                ptr = &input[0];
/*      Is this a shell command?                                        */

                if ((newline) && (*ptr == '!'))
                        shellcmd(++ptr);

/*      Send line to the receipient.                                    */

                else {
                        if (myuid && !permit1(fileno(fp))) {
                                (void) fprintf(stderr,
                        gettext("Can no longer write to %s\n"), rterminal);
                                break;
                        }

/*
 * All non-printable characters are displayed using a special notation:
 * Control characters  shall be displayed using the two character
 * sequence of ^ (carat) and the ASCII character - decimal 64 greater
 * that the character being encoded - eg., a \003 is displayed ^C.
 * Characters with the eighth bit set shall be displayed using
 * the three or four character meta notation - e.g., \372 is
 * displayed M-z and \203 is displayed M-^C.
 */

                        newline = 0;
                        for (bp = &input[0]; --i >= 0; bp++) {
                        if (*bp == '\n') {
                                newline = 1;
                                putc('\r', fp);
                        }
                        if (*bp == ' ' ||
                                 *bp == '\t' || *bp == '\n' ||
                                 *bp == '\r' || *bp == '\013' ||
                                 *bp == '\007') {
                                        putc(*bp, fp);
                        } else if (((n = mbtowc(&wc, bp, MB_CUR_MAX)) > 0) &&
                                iswprint(wc)) {
                                for (; n > 0; --n, --i, ++bp)
                                        putc(*bp, fp);
                                bp--, ++i;
                        } else {
                                if (!isascii(*bp)) {
                                        fputs("M-", fp);
                                        *bp = toascii(*bp);
                                }
                                if (iscntrl(*bp)) {
                                        putc('^', fp);
/*      add decimal 64 to the control character                 */
                                        putc(*bp + 0100, fp);
                                }
                                else
                                        putc(*bp, fp);
                        }
                        if (*bp == '\n')
                                fflush(fp);
                        if (ferror(fp) || feof(fp)) {
                                printf(gettext(
                                "\n\007Write failed (%s logged out?)\n"),
                                receipient);
                                exit(1);
                        }
                        } /* for */
                        fflush(fp);
        } /* else */
        } /* while */

/*      Since "end of file" received, send <EOT> message to receipient. */

        eof();
        return (0);
}


static void
setsignals(catch)
void (*catch)();
{
        signal(SIGHUP, catch);
        signal(SIGINT, catch);
        signal(SIGQUIT, catch);
        signal(SIGTERM, catch);
}


static void
shellcmd(command)
char *command;
{
        register pid_t child;
        extern void eof();

        if ((child = fork()) == (pid_t)FAILURE)
            {
            (void) fprintf(stderr,
            gettext("Unable to fork.  Try again later.\n"));
            return;
            } else if (child == (pid_t)0) {
/*      Reset the signals to the default actions and exec a shell.      */

            if (setgid(getgid()) < 0)
                exit(1);
            execl("/usr/bin/sh", "sh", "-c", command, 0);
            exit(0);
            }
        else
            {
/*      Allow user to type <del> and <quit> without dying during        */
/*      commands.                                                       */

            signal(SIGINT, SIG_IGN);
            signal(SIGQUIT, SIG_IGN);

/*      As parent wait around for user to finish spunoff command.       */

            while (wait(NULL) != child);

/*      Reset the signals to their normal state.                        */

            setsignals(eof);
            }
        (void) fprintf(stdout, "!\n");
}

static void
openfail()
{
        extern char *rterm, *receipient;

        (void) fprintf(stderr,
                gettext("Timeout trying to open %s's line(%s).\n"),
            receipient, rterm);
        exit(1);
}

static void
eof()
{
        extern FILE *fp;

        (void) fprintf(fp, "%s\n", gettext("<EOT>"));
        exit(0);
}

/*
 * permit: check mode of terminal - if not writable by all disallow writing to
 * (even the user cannot therefore write to their own tty)
 */

static int
permit(term)
char *term;
{
        struct stat buf;
        int fildes;

        if ((fildes = open(term, O_WRONLY|O_NOCTTY)) < 0)
                return (0);
        /* check if the device really is a tty */
        if (!isatty(fildes)) {
                (void) fprintf(stderr,
                    gettext("%s in utmpx is not a tty\n"), term);
                openlog("write", 0, LOG_AUTH);
                syslog(LOG_CRIT, "%s in utmpx is not a tty\n", term);
                closelog();
                close(fildes);
                return (0);
        }
        fstat(fildes, &buf);
        close(fildes);
        return (buf.st_mode & (S_IWGRP|S_IWOTH));
}



/*
 * permit1: check mode of terminal - if not writable by all disallow writing
 * to (even the user themself cannot therefore write to their own tty)
 */

/* this is used with fstat (which is faster than stat) where possible */

static int
permit1(fildes)
int fildes;
{
        struct stat buf;

        fstat(fildes, &buf);
        return (buf.st_mode & (S_IWGRP|S_IWOTH));
}


/*
 * Read a string of multi-byte characters from specified file.
 * The requested # of bytes are attempted to read.
 * readcsi() tries to complete the last multibyte character
 * by calling mbtowc(), if the leftovers form mbtowc(),
 * left the last char imcomplete, moves into delta_spool to use later,
 * next called. The caller must reserve
 * nbytereq+MB_LEN_MAX bytes for the buffer.  When the attempt
 * is failed, it truncate the last char.
 * Returns the number of bytes that constitutes the valid multi-byte characters.
 */


static int readcsi(d, buf, nbytereq)
int     d;
char    *buf;
int     nbytereq;
{
        static char     delta_pool[MB_LEN_MAX * 2];
        static char     delta_size;
        char    *cp, *nextp, *lastp;
        int     n;
        int     r_size;

        if (delta_size) {
                memcpy(buf, delta_pool, delta_size);
                cp = buf + delta_size;
                r_size = nbytereq - delta_size;
        } else {
                cp = buf;
                r_size = nbytereq;
        }

        if ((r_size = read(d, cp, r_size)) < 0)
                r_size = 0;
        if ((n = delta_size + r_size) <= 0)
                return (n);

        /* Scan the result to test the completeness of each EUC characters. */
        nextp = buf;
        lastp = buf + n; /* Lastp points to the first junk byte. */
        while (nextp < lastp) {
                if ((n = (lastp - nextp)) > (unsigned int)MB_CUR_MAX)
                        n = (unsigned int)MB_CUR_MAX;
                if ((n = mbtowc((wchar_t *)0, nextp, n)) <= 0) {
                        if ((lastp - nextp) < (unsigned int)MB_CUR_MAX)
                                break;
                        n = 1;
                }
                nextp += n;
        }
        /* How many bytes needed to complete the last char? */
        delta_size = lastp - nextp;
        if (delta_size > 0) {
                if (nextp[delta_size - 1] != '\n') {
                        /* the remnants store into delta_pool */
                        memcpy(delta_pool, nextp, delta_size);
                } else
                        nextp = lastp;
        }
        *nextp = '\0';
        return (nextp-buf); /* Return # of bytes. */
}