/*      $OpenBSD: fingerd.c,v 1.42 2021/07/12 15:09:18 beck 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/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <errno.h>

#include <err.h>
#include <unistd.h>
#include <syslog.h>
#include <netdb.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <stdarg.h>
#include <limits.h>
#include "pathnames.h"

__dead void logerr(const char *, ...);
__dead void usage(void);

void
usage(void)
{
        syslog(LOG_ERR,
            "usage: fingerd [-lMmpSsu] [-P filename]");
        exit(2);
}


int
main(int argc, char *argv[])
{
        FILE *fp;
        int ch, ac = 2;
        int p[2], logging, secure, user_required, short_list;
#define ENTRIES 50
        char **comp, *prog;
        char **ap, *av[ENTRIES + 1], line[8192], *lp, *hname;
        char hostbuf[HOST_NAME_MAX+1];

        prog = _PATH_FINGER;
        logging = secure = user_required = short_list = 0;
        openlog("fingerd", LOG_PID, LOG_DAEMON);
        opterr = 0;
        while ((ch = getopt(argc, argv, "sluSmMpP:")) != -1)
                switch (ch) {
                case 'l':
                        logging = 1;
                        break;
                case 'P':
                        prog = optarg;
                        break;
                case 's':
                        secure = 1;
                        break;
                case 'u':
                        user_required = 1;
                        break;
                case 'S':
                        if (ac < ENTRIES) {
                                short_list = 1;
                                av[ac++] = "-s";
                        }
                        break;
                case 'm':
                        if (ac < ENTRIES)
                                av[ac++] = "-m";
                        break;
                case 'M':
                        if (ac < ENTRIES)
                                av[ac++] = "-M";
                        break;
                case 'p':
                        if (ac < ENTRIES)
                                av[ac++] = "-p";
                        break;
                default:
                        usage();
                }

        if (unveil(prog, "x") == -1)
                err(1, "unveil %s", prog);
        if (pledge("stdio inet dns proc exec", NULL) == -1)
                err(1, "pledge");

        if (logging) {
                struct sockaddr_storage ss;
                struct sockaddr *sa;
                socklen_t sval;

                sval = sizeof(ss);
                if (getpeername(0, (struct sockaddr *)&ss, &sval) == -1)
                        err(1, "getpeername");
                sa = (struct sockaddr *)&ss;

                if (pledge("stdio dns proc exec", NULL) == -1)
                        err(1, "pledge");

                if (getnameinfo(sa, sa->sa_len, hostbuf, sizeof(hostbuf),
                    NULL, 0, 0) != 0) {
                        strlcpy(hostbuf, "?", sizeof(hostbuf));
                }
                hname = hostbuf;
        }

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

        if (fgets(line, sizeof(line), stdin) == NULL) {
                if (logging)
                        syslog(LOG_NOTICE, "query from %s: %s", hname,
                            feof(stdin) ? "EOF" : strerror(errno));
                exit(1);
        }

        if (logging)
                syslog(LOG_NOTICE, "query from %s: `%.*s'", hname,
                    (int)strcspn(line, "\r\n"), line);

        /*
         * Note: we assume that finger(1) will treat "--" as end of
         * command args (ie: that it uses getopt(3)).
         */
        av[ac++] = "--";
        comp = &av[1];
        for (lp = line, ap = &av[ac]; ac < ENTRIES;) {
                size_t len;

                if ((*ap = strtok(lp, " \t\r\n")) == NULL)
                        break;
                lp = NULL;
                if (secure && strchr(*ap, '@')) {
                        (void) puts("forwarding service denied\r");
                        exit(1);
                }

                len = strlen(*ap);
                while (len > 0 && (*ap)[len - 1] == '@')
                        (*ap)[--len] = '\0';
                if (**ap == '\0')
                        continue;

                /* RFC1196: "/[Ww]" == "-l" */
                if ((*ap)[0] == '/' && ((*ap)[1] == 'W' || (*ap)[1] == 'w')) {
                        if (!short_list) {
                                av[1] = "-l";
                                comp = &av[0];
                        }
                } else {
                        ap++;
                        ac++;
                }
        }
        av[ENTRIES - 1] = NULL;

        if ((lp = strrchr(prog, '/')))
                *comp = ++lp;
        else
                *comp = prog;

        if (user_required) {
                for (ap = comp + 1; strcmp("--", *(ap++)); )
                        ;
                if (*ap == NULL) {
                        (void) puts("must provide username\r");
                        exit(1);
                }
        }

        if (pipe(p) == -1)
                logerr("pipe: %s", strerror(errno));

        switch (vfork()) {
        case 0:
                (void) close(p[0]);
                if (p[1] != 1) {
                        (void) dup2(p[1], 1);
                        (void) close(p[1]);
                }
                execv(prog, comp);
                syslog(LOG_ERR, "execv: %s: %s", prog, strerror(errno));
                _exit(1);
        case -1:
                logerr("fork: %s", strerror(errno));
        }
        if (pledge("stdio", NULL) == -1)
                err(1, "pledge");

        (void) close(p[1]);
        if (!(fp = fdopen(p[0], "r")))
                logerr("fdopen: %s", strerror(errno));
        while ((ch = getc(fp)) != EOF) {
                if (ch == '\n')
                        putchar('\r');
                putchar(ch);
        }
        exit(0);
}

void
logerr(const char *fmt, ...)
{
        va_list ap;

        va_start(ap, fmt);
        (void) vsyslog(LOG_ERR, fmt, ap);
        va_end(ap);
        exit(1);
}