/*      $OpenBSD: wall.c,v 1.37 2023/03/08 04:43:12 guenther Exp $      */
/*      $NetBSD: wall.c,v 1.6 1994/11/17 07:17:58 jtc Exp $     */

/*
 * Copyright (c) 1988, 1990, 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.
 */

/*
 * This program is not related to David Wall, whose Stanford Ph.D. thesis
 * is entitled "Mechanisms for Broadcast and Selective Broadcast".
 */

#include <sys/queue.h>
#include <sys/stat.h>
#include <sys/time.h>
#include <sys/uio.h>

#include <ctype.h>
#include <err.h>
#include <grp.h>
#include <limits.h>
#include <paths.h>
#include <pwd.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <utmp.h>

struct wallgroup {
        gid_t   gid;
        char    *name;
        char    **mem;
        struct wallgroup *next;
} *grouplist;

struct utmptty {
        char    *tty;
        SLIST_ENTRY(utmptty) next;
};

void    makemsg(char *);
void    addgroup(struct group *, char *);
char   *ttymsg(struct iovec *, int, char *, int);
__dead  void usage(void);
static int isu8cont(unsigned char);

int nobanner;
int mbufsize;
char *mbuf;

int
main(int argc, char **argv)
{
        FILE *fp;
        int ch, ingroup;
        struct iovec iov;
        struct utmp utmp;
        char *p, **mem;
        char line[sizeof(utmp.ut_line) + 1];
        char username[sizeof(utmp.ut_name) + 1];
        struct passwd *pw;
        struct group *grp;
        struct wallgroup *g;
        struct utmptty *un;
        SLIST_HEAD(,utmptty) utmphead;
        SLIST_INIT(&utmphead);

        while ((ch = getopt(argc, argv, "ng:")) != -1)
                switch (ch) {
                case 'n':
                        /* undoc option for shutdown: suppress banner */
                        pw = getpwnam("nobody");
                        if (geteuid() == 0 || (pw && getuid() == pw->pw_uid))
                                nobanner = 1;
                        break;
                case 'g':
                        if ((grp = getgrnam(optarg)) == NULL)
                                errx(1, "unknown group `%s'", optarg);
                        addgroup(grp, optarg);
                        break;
                default:
                        usage();
                }
        argc -= optind;
        argv += optind;
        if (argc > 1)
                usage();

        makemsg(*argv);

        if (unveil(_PATH_UTMP, "r") == -1)
                err(1, "unveil %s", _PATH_UTMP);
        if (unveil(_PATH_DEV, "w") == -1)
                err(1, "unveil %s", _PATH_DEV);
        if (unveil(_PATH_DEVDB, "r") == -1)
                err(1, "unveil %s", _PATH_DEVDB);
        if (pledge("stdio rpath wpath getpw proc", NULL) == -1)
                err(1, "pledge");

        if (!(fp = fopen(_PATH_UTMP, "r")))
                err(1, "cannot read %s", _PATH_UTMP);
        iov.iov_base = mbuf;
        iov.iov_len = mbufsize;

        while (fread(&utmp, sizeof(utmp), 1, fp) == 1) {
                if (!utmp.ut_name[0])
                        continue;
                if (grouplist) {
                        ingroup = 0;
                        strncpy(username, utmp.ut_name, sizeof(utmp.ut_name));
                        username[sizeof(utmp.ut_name)] = '\0';
                        pw = getpwnam(username);
                        if (!pw)
                                continue;
                        for (g = grouplist; g && ingroup == 0; g = g->next) {
                                if (g->gid == pw->pw_gid)
                                        ingroup = 1;
                                for (mem = g->mem; *mem && ingroup == 0; mem++)
                                        if (strcmp(username, *mem) == 0)
                                                ingroup = 1;
                        }
                        if (ingroup == 0)
                                continue;
                }
                strncpy(line, utmp.ut_line, sizeof(utmp.ut_line));
                line[sizeof(utmp.ut_line)] = '\0';
                un = malloc(sizeof(struct utmptty));
                if (un == NULL)
                        err(1, "malloc");
                un->tty = strndup(line, sizeof(utmp.ut_line));
                if (un->tty == NULL)
                        err(1, "strndup");
                SLIST_INSERT_HEAD(&utmphead, un, next);
        }
        fclose(fp);

        if (pledge("stdio rpath wpath proc", NULL) == -1)
                err(1, "pledge");

        SLIST_FOREACH(un, &utmphead, next) {
                if ((p = ttymsg(&iov, 1, un->tty, 60*5)) != NULL)
                        warnx("%s", p);
        }

        exit(0);
}

void
makemsg(char *fname)
{
        int cnt;
        struct tm *lt;
        struct passwd *pw;
        struct stat sbuf;
        time_t now;
        FILE *fp;
        int fd;
        char *p, *whom, hostname[HOST_NAME_MAX+1], lbuf[100], tmpname[PATH_MAX];
        char *ttynam;
        unsigned char ch;

        snprintf(tmpname, sizeof(tmpname), "%s/wall.XXXXXXXXXX", _PATH_TMP);
        if ((fd = mkstemp(tmpname)) >= 0) {
                (void)unlink(tmpname);
                fp = fdopen(fd, "r+");
        }
        if (fd == -1 || fp == NULL)
                err(1, "can't open temporary file");

        if (!nobanner) {
                if (!(whom = getlogin()))
                        whom = (pw = getpwuid(getuid())) ? pw->pw_name : "???";
                (void)gethostname(hostname, sizeof(hostname));
                (void)time(&now);
                lt = localtime(&now);
                if ((ttynam = ttyname(STDERR_FILENO)) == NULL)
                        ttynam = "(not a tty)";

                /*
                 * all this stuff is to blank out a square for the message;
                 * we wrap message lines at column 79, not 80, because some
                 * terminals wrap after 79, some do not, and we can't tell.
                 * Which means that we may leave a non-blank character
                 * in column 80, but that can't be helped.
                 */
                (void)fprintf(fp, "\r%79s\r\n", " ");
                (void)snprintf(lbuf, sizeof lbuf,
                    "Broadcast Message from %s@%s", whom, hostname);
                (void)fprintf(fp, "%-79.79s\007\007\r\n", lbuf);
                (void)snprintf(lbuf, sizeof lbuf,
                    "        (%s) at %d:%02d ...", ttynam,
                    lt->tm_hour, lt->tm_min);
                (void)fprintf(fp, "%-79.79s\r\n", lbuf);
        }
        (void)fprintf(fp, "%79s\r\n", " ");

        if (fname) {
                gid_t egid = getegid();

                setegid(getgid());
                if (freopen(fname, "r", stdin) == NULL)
                        err(1, "can't read %s", fname);
                setegid(egid);
        }
        cnt = 0;
        while (fgets(lbuf, sizeof(lbuf), stdin))
                for (p = lbuf; (ch = *p) != '\0'; ++p, ++cnt) {
                        if (cnt == 79 || ch == '\n') {
                                for (; cnt < 79; ++cnt)
                                        putc(' ', fp);
                                putc('\r', fp);
                                putc('\n', fp);
                                cnt = -1;
                                if (ch != '\n')
                                        p--;
                        } else if (!isu8cont(ch))
                                putc(isprint(ch) || isspace(ch) || ch == '\a' ?
                                    ch : '?', fp);
                }
        (void)fprintf(fp, "%79s\r\n", " ");
        rewind(fp);

        if (fstat(fd, &sbuf))
                err(1, "can't stat temporary file");
        mbufsize = sbuf.st_size;
        mbuf = malloc((u_int)mbufsize);
        if (mbuf == NULL)
                err(1, NULL);
        if (fread(mbuf, sizeof(*mbuf), mbufsize, fp) != mbufsize)
                err(1, "can't read temporary file");
        (void)close(fd);
}

void
addgroup(struct group *grp, char *name)
{
        int i;
        struct wallgroup *g;

        for (i = 0; grp->gr_mem[i]; i++)
                ;

        g = malloc(sizeof *g);
        if (g == NULL)
                err(1, NULL);
        g->gid = grp->gr_gid;
        g->name = name;
        g->mem = calloc(i + 1, sizeof(char *));
        if (g->mem == NULL)
                err(1, NULL);
        for (i = 0; grp->gr_mem[i] != NULL; i++) {
                g->mem[i] = strdup(grp->gr_mem[i]);
                if (g->mem[i] == NULL)
                        err(1, NULL);
        }
        g->mem[i] = NULL;
        g->next = grouplist;
        grouplist = g;
}

void
usage(void)
{
        extern char *__progname;

        (void)fprintf(stderr, "usage: %s [-g group] [file]\n", __progname);
        exit(1);
}

static int
isu8cont(unsigned char c)
{
        return (c & (0x80 | 0x40)) == 0x80;
}