/*      $NetBSD: rsh.c,v 1.39 2021/04/13 06:25:49 mrg Exp $     */

/*-
 * Copyright (c) 1983, 1990, 1993, 1994
 *      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) 1983, 1990, 1993, 1994\
 The Regents of the University of California.  All rights reserved.");
#endif /* not lint */

#ifndef lint
#if 0
static char sccsid[] = "@(#)rsh.c       8.4 (Berkeley) 4/29/95";
#else
__RCSID("$NetBSD: rsh.c,v 1.39 2021/04/13 06:25:49 mrg Exp $");
#endif
#endif /* not lint */

#include <sys/types.h>
#include <sys/socket.h>
#include <sys/ioctl.h>
#include <sys/file.h>
#include <poll.h>

#include <netinet/in.h>
#include <netinet/tcp.h>
#include <netdb.h>

#include <err.h>
#include <errno.h>
#include <limits.h>
#include <pwd.h>
#include <signal.h>
#include <stdarg.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>

#include "pathnames.h"
#include "getport.h"


/*
 * rsh - remote shell
 */
int     remerr;

static int sigs[] = { SIGINT, SIGTERM, SIGQUIT };

static char   *copyargs(char **);
static void     sendsig(int);
static int      checkfd(struct pollfd *, int);
static void     talk(int, sigset_t *, pid_t, int);
__dead static void      usage(void);
#ifdef IN_RCMD
int      orcmd(char **, int, const char *,
    const char *, const char *, int *);
int      orcmd_af(char **, int, const char *,
    const char *, const char *, int *, int);
static int      relay_signal;
#endif

int
main(int argc, char **argv)
{
        struct passwd *pw;
        struct servent *sp;
        sigset_t oset, nset;
        struct protoent *proto;

#ifdef IN_RCMD
        char    *locuser = 0, *loop, *relay;
#endif /* IN_RCMD */
        int argoff, asrsh, ch, dflag, nflag, one, rem;
        size_t i;
        int family = AF_UNSPEC;
        pid_t pid;
        uid_t uid;
        char *args, *host, *p, *user, *name;

        argoff = asrsh = dflag = nflag = 0;
        one = 1;
        host = user = NULL;
        sp = NULL;

#ifndef IN_RCMD
        /*
         * If called as something other than "rsh" use it as the host name,
         * only for rsh.
         */
        if (strcmp(getprogname(), "rsh") == 0)
                asrsh = 1;
        else {
                host = strdup(getprogname());
                if (host == NULL)
                        err(1, NULL);
        }
#endif /* IN_RCMD */

        /* handle "rsh host flags" */
        if (!host && argc > 2 && argv[1][0] != '-') {
                host = argv[1];
                argoff = 1;
        }

#ifdef IN_RCMD
        if ((relay = getenv("RCMD_RELAY_SIGNAL")) && strcmp(relay, "YES") == 0)
                relay_signal = 1;
        if ((loop = getenv("RCMD_LOOP")) && strcmp(loop, "YES") == 0)
                warnx("rcmd appears to be looping!");

        setenv("RCMD_LOOP", "YES", 1);

#  define       OPTIONS "468KLdel:np:u:w"

#else /* IN_RCMD */

#  define       OPTIONS "468KLdel:np:w"

#endif /* IN_RCMD */

        if (!(pw = getpwuid(uid = getuid())))
                errx(1, "unknown user id");

        if ((name = strdup(pw->pw_name)) == NULL)
                err(1, "malloc");
        while ((ch = getopt(argc - argoff, argv + argoff, OPTIONS)) != -1)
                switch (ch) {
                case '4':
                        family = AF_INET;
                        break;
                case '6':
                        family = AF_INET6;
                        break;
                case 'K':
                        break;
                case 'L':       /* -8Lew are ignored to allow rlogin aliases */
                case 'e':
                case 'w':
                case '8':
                        break;
                case 'd':
                        dflag = 1;
                        break;
                case 'l':
                        user = optarg;
                        break;
                case 'n':
                        nflag = 1;
                        break;
                case 'p':
                        sp = getport(optarg, "tcp");
                        break;
#ifdef IN_RCMD
                case 'u':
                        if (getuid() != 0 && optarg && name &&
                            strcmp(name, optarg) != 0)
                                errx(1,"only super user can use the -u option");
                        locuser = optarg;
                        break;
#endif /* IN_RCMD */
                case '?':
                default:
                        usage();
                }
        optind += argoff;

        /* if haven't gotten a host yet, do so */
        if (!host && !(host = argv[optind++]))
                usage();

        /* if no further arguments, must have been called as rlogin. */
        if (!argv[optind]) {
#ifdef IN_RCMD
                usage();
#else
                if (asrsh)
                        *argv = __UNCONST("rlogin");
                setuid(uid);
                execv(_PATH_RLOGIN, argv);
                err(1, "can't exec %s", _PATH_RLOGIN);
#endif
        }

        argc -= optind;
        argv += optind;

        /* Accept user1@host format, though "-l user2" overrides user1 */
        p = strchr(host, '@');
        if (p) {
                *p = '\0';
                if (!user && p > host)
                        user = host;
                host = p + 1;
                if (*host == '\0')
                        usage();
        }
        if (!user)
                user = name;


        args = copyargs(argv);

        if (sp == NULL)
                sp = getservbyname("shell", "tcp");
        if (sp == NULL)
                errx(1, "shell/tcp: unknown service");


#ifdef IN_RCMD
        rem = orcmd_af(&host, sp->s_port, locuser ? locuser :
#else
        rem = rcmd_af(&host, sp->s_port,
#endif
            name, user, args, &remerr, family);
        (void)free(name);

        if (rem < 0)
                exit(1);

        if (remerr < 0)
                errx(1, "can't establish stderr");
        if (dflag) {
                if (setsockopt(rem, SOL_SOCKET, SO_DEBUG, &one,
                    sizeof(one)) < 0)
                        warn("setsockopt remote");
                if (setsockopt(remerr, SOL_SOCKET, SO_DEBUG, &one,
                    sizeof(one)) < 0)
                        warn("setsockopt stderr");
        }
        proto = getprotobyname("tcp");
        setsockopt(rem, proto->p_proto, TCP_NODELAY, &one, sizeof(one));
        setsockopt(remerr, proto->p_proto, TCP_NODELAY, &one, sizeof(one));


        (void)setuid(uid);

        (void)sigemptyset(&nset);
        for (i = 0; i < sizeof(sigs) / sizeof(sigs[0]); i++)
                (void)sigaddset(&nset, sigs[i]);

        (void)sigprocmask(SIG_BLOCK, &nset, &oset);

#ifdef IN_RCMD
        if (!relay_signal)
#endif
                for (i = 0; i < sizeof(sigs) / sizeof(sigs[0]); i++) {
                        struct sigaction sa;

                        if (sa.sa_handler != SIG_IGN) {
                                sa.sa_handler = sendsig;
                                (void)sigaction(sigs[i], &sa, NULL);
                        }
                }

        if (!nflag) {
                pid = fork();
                if (pid < 0)
                        err(1, "fork");
        }
        else
                pid = -1;

        (void)ioctl(remerr, FIONBIO, &one);
        (void)ioctl(rem, FIONBIO, &one);

        talk(nflag, &oset, pid, rem);

        if (!nflag)
                (void)kill(pid, SIGKILL);
        exit(0);
}

static int
checkfd(struct pollfd *fdp, int outfd)
{
        int nr, nw;
        char buf[BUFSIZ];

        if (fdp->revents & (POLLNVAL|POLLERR|POLLHUP))
                return -1;

        if ((fdp->revents & POLLIN) == 0)
                return 0;

        errno = 0;
        nr = read(fdp->fd, buf, sizeof buf);

        if (nr <= 0) {
                if (errno != EAGAIN)
                        return -1;
                else
                        return 0;
        }
        else {
                char *bc = buf;
                while (nr) {
                        if ((nw = write(outfd, bc, nr)) <= 0)
                                return -1;
                        nr -= nw;
                        bc += nw;
                }
                return 0;
        }
}

static void
talk(int nflag, sigset_t *oset, __pid_t pid, int rem)
{
        int nr, nw, nfds;
        struct pollfd fds[3], *fdp = &fds[0];
        char *bp, buf[BUFSIZ];

        if (!nflag && pid == 0) {
                (void)close(remerr);

                fdp->events = POLLOUT|POLLNVAL|POLLERR|POLLHUP;
                fdp->fd = rem;
                nr = 0;
                bp = buf;

                for (;;) {
                        errno = 0;

                        if (nr == 0) {
                                if ((nr = read(0, buf, sizeof buf)) == 0)
                                        goto done;
                                if (nr == -1) {
                                        if (errno == EIO)
                                                goto done;
                                        if (errno == EINTR) {
                                                nr = 0;
                                                continue;
                                        }
                                        err(1, "read");
                                }
                                bp = buf;
                        }

rewrite:                if (poll(fdp, 1, INFTIM) == -1) {
                                if (errno != EINTR)
                                        err(1, "poll");
                                goto rewrite;
                        }

                        if (fdp->revents & (POLLNVAL|POLLERR|POLLHUP))
                                err(1, "poll");

                        if ((fdp->revents & POLLOUT) == 0)
                                goto rewrite;

                        nw = write(rem, bp, nr);

                        if (nw < 0) {
                                if (errno == EAGAIN)
                                        continue;
                                err(1, "write");
                        }
                        bp += nw;
                        nr -= nw;
                }
done:
                (void)shutdown(rem, 1);
                exit(0);
        }

        fdp = &fds[1];
        nfds = 2;
        fds[0].events = 0;
#ifdef IN_RCMD
        if (relay_signal) {
                fdp = &fds[0];
                nfds = 3;
                fds[0].events = POLLIN|POLLNVAL|POLLERR|POLLHUP;
                fds[0].fd = 2;
        } else
#endif
                (void)sigprocmask(SIG_SETMASK, oset, NULL);
        fds[1].events = fds[2].events = POLLIN|POLLNVAL|POLLERR|POLLHUP;
        fds[1].fd = remerr;
        fds[2].fd = rem;
        do {
                if (poll(fdp, nfds, INFTIM) == -1) {
                        if (errno != EINTR)
                                err(1, "poll");
                        continue;
                }
                if ((fds[1].events != 0 && checkfd(&fds[1], 2) == -1)
#ifdef IN_RCMD
                    || (fds[0].events != 0 && checkfd(&fds[0], remerr) == -1)
#endif
                    ) {
                        nfds--;
                        fds[1].events = 0;
#ifdef IN_RCMD
                        if (relay_signal) {
                                nfds--;
                                fds[0].events = 0;
                        }
#endif
                        fdp = &fds[2];
                }
                if (fds[2].events != 0 && checkfd(&fds[2], 1) == -1) {
                        nfds--;
                        fds[2].events = 0;
                }
        }
        while (nfds);
}

static void
sendsig(int sig)
{
        char signo;

        signo = sig;
        (void)write(remerr, &signo, 1);
}

static char *
copyargs(char **argv)
{
        int cc;
        char **ap, *args, *p, *ep;

        cc = 0;
        for (ap = argv; *ap; ++ap)
                cc += strlen(*ap) + 1;
        if (cc == 0)
                usage();
        if (!(args = malloc((u_int)cc)))
                err(1, "malloc");
        ep = args + cc;
        for (p = args, *p = '\0', ap = argv; *ap; ++ap) {
                (void)strlcpy(p, *ap, ep - p);
                p += strlen(p);
                if (ap[1])
                        *p++ = ' ';
        }
        *p = '\0';
        return (args);
}

static void
usage(void)
{

        (void)fprintf(stderr,
            "usage: %s [-46dn] [-l login] [-p port]%s [login@]host command\n",
            getprogname(),
#ifdef IN_RCMD
            " [-u locuser]"
#else
            ""
#endif
            );
        exit(1);
}