/*      $OpenBSD: rcmdsh.c,v 1.7 2002/03/12 00:05:44 millert Exp $      */

/*-
 * SPDX-License-Identifier: BSD-3-Clause
 *
 * Copyright (c) 2001, MagniComp
 * 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 MagniComp 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 COPYRIGHT HOLDERS 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 is an rcmd() replacement originally by
 * Chris Siebenmann <cks@utcc.utoronto.ca>.
 */

#include "namespace.h"
#include <sys/types.h>
#include <sys/socket.h>
#include <sys/wait.h>
#include <arpa/inet.h>

#include <errno.h>
#include <netdb.h>
#include <paths.h>
#include <pwd.h>
#include <stdio.h>
#include <string.h>
#include <unistd.h>
#include "un-namespace.h"

/*
 * This is a replacement rcmd() function that uses the rsh(1)
 * program in place of a direct rcmd(3) function call so as to
 * avoid having to be root.  Note that rport is ignored.
 */
int
rcmdsh(char **ahost, int rport, const char *locuser, const char *remuser,
    const char *cmd, const char *rshprog)
{
        struct addrinfo hints, *res;
        int sp[2], error;
        pid_t cpid;
        char *p;
        struct passwd *pw;
        char num[8];
        static char hbuf[NI_MAXHOST];

        /* What rsh/shell to use. */
        if (rshprog == NULL)
                rshprog = _PATH_RSH;

        /* locuser must exist on this host. */
        if ((pw = getpwnam(locuser)) == NULL) {
                (void)fprintf(stderr, "rcmdsh: unknown user: %s\n", locuser);
                return (-1);
        }

        /* Validate remote hostname. */
        if (strcmp(*ahost, "localhost") != 0) {
                memset(&hints, 0, sizeof(hints));
                hints.ai_flags = AI_CANONNAME;
                hints.ai_family = PF_UNSPEC;
                hints.ai_socktype = SOCK_STREAM;
                (void)snprintf(num, sizeof(num), "%u",
                    (unsigned int)ntohs(rport));
                error = getaddrinfo(*ahost, num, &hints, &res);
                if (error) {
                        fprintf(stderr, "rcmdsh: getaddrinfo: %s\n",
                                gai_strerror(error));
                        return (-1);
                }
                if (res->ai_canonname) {
                        strncpy(hbuf, res->ai_canonname, sizeof(hbuf) - 1);
                        hbuf[sizeof(hbuf) - 1] = '\0';
                        *ahost = hbuf;
                }
                freeaddrinfo(res);
        }

        /* Get a socketpair we'll use for stdin and stdout. */
        if (_socketpair(AF_UNIX, SOCK_STREAM, PF_UNSPEC, sp) == -1) {
                perror("rcmdsh: socketpair");
                return (-1);
        }

        cpid = fork();
        if (cpid == -1) {
                perror("rcmdsh: fork failed");
                return (-1);
        } else if (cpid == 0) {
                /*
                 * Child.  We use sp[1] to be stdin/stdout, and close sp[0].
                 */
                (void)_close(sp[0]);
                if (_dup2(sp[1], 0) == -1 || _dup2(0, 1) == -1) {
                        perror("rcmdsh: dup2 failed");
                        _exit(255);
                }
                /* Fork again to lose parent. */
                cpid = fork();
                if (cpid == -1) {
                        perror("rcmdsh: fork to lose parent failed");
                        _exit(255);
                }
                if (cpid > 0)
                        _exit(0);

                /* In grandchild here.  Become local user for rshprog. */
                if (setuid(pw->pw_uid) == -1) {
                        (void)fprintf(stderr, "rcmdsh: setuid(%u): %s\n",
                            pw->pw_uid, strerror(errno));
                        _exit(255);
                }

                /*
                 * If remote host is "localhost" and local and remote users
                 * are the same, avoid running remote shell for efficiency.
                 */
                if (strcmp(*ahost, "localhost") == 0 &&
                    strcmp(locuser, remuser) == 0) {
                        if (pw->pw_shell[0] == '\0')
                                rshprog = _PATH_BSHELL;
                        else
                                rshprog = pw->pw_shell;
                        p = strrchr(rshprog, '/');
                        execlp(rshprog, p ? p + 1 : rshprog, "-c", cmd,
                            (char *)NULL);
                } else {
                        p = strrchr(rshprog, '/');
                        execlp(rshprog, p ? p + 1 : rshprog, *ahost, "-l",
                            remuser, cmd, (char *)NULL);
                }
                (void)fprintf(stderr, "rcmdsh: execlp %s failed: %s\n",
                    rshprog, strerror(errno));
                _exit(255);
        } else {
                /* Parent. close sp[1], return sp[0]. */
                (void)_close(sp[1]);
                /* Reap child. */
                (void)_waitpid(cpid, NULL, 0);
                return (sp[0]);
        }
        /* NOTREACHED */
}