1/*	$OpenBSD: rcmdsh.c,v 1.7 2002/03/12 00:05:44 millert Exp $	*/
2
3/*-
4 * SPDX-License-Identifier: BSD-3-Clause
5 *
6 * Copyright (c) 2001, MagniComp
7 * All rights reserved.
8 *
9 * Redistribution and use in source and binary forms, with or without
10 * modification, are permitted provided that the following conditions
11 * are met:
12 * 1. Redistributions of source code must retain the above copyright
13 *    notice, this list of conditions and the following disclaimer.
14 * 2. Redistributions in binary form must reproduce the above copyright
15 *    notice, this list of conditions and the following disclaimer in
16 *    the documentation and/or other materials provided with the distribution.
17 * 3. Neither the name of the MagniComp nor the names of its contributors may
18 *    be used to endorse or promote products derived from this software
19 *    without specific prior written permission.
20 *
21 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
22 * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
23 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
24 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE FOR
25 * ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
26 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
27 * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
28 * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
29 * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE
30 * USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
31 */
32
33/*
34 * This is an rcmd() replacement originally by
35 * Chris Siebenmann <cks@utcc.utoronto.ca>.
36 */
37
38#include "namespace.h"
39#include <sys/types.h>
40#include <sys/socket.h>
41#include <sys/wait.h>
42#include <arpa/inet.h>
43
44#include <errno.h>
45#include <netdb.h>
46#include <paths.h>
47#include <pwd.h>
48#include <stdio.h>
49#include <string.h>
50#include <unistd.h>
51#include "un-namespace.h"
52
53/*
54 * This is a replacement rcmd() function that uses the rsh(1)
55 * program in place of a direct rcmd(3) function call so as to
56 * avoid having to be root.  Note that rport is ignored.
57 */
58int
59rcmdsh(char **ahost, int rport, const char *locuser, const char *remuser,
60    const char *cmd, const char *rshprog)
61{
62	struct addrinfo hints, *res;
63	int sp[2], error;
64	pid_t cpid;
65	char *p;
66	struct passwd *pw;
67	char num[8];
68	static char hbuf[NI_MAXHOST];
69
70	/* What rsh/shell to use. */
71	if (rshprog == NULL)
72		rshprog = _PATH_RSH;
73
74	/* locuser must exist on this host. */
75	if ((pw = getpwnam(locuser)) == NULL) {
76		(void)fprintf(stderr, "rcmdsh: unknown user: %s\n", locuser);
77		return (-1);
78	}
79
80	/* Validate remote hostname. */
81	if (strcmp(*ahost, "localhost") != 0) {
82		memset(&hints, 0, sizeof(hints));
83		hints.ai_flags = AI_CANONNAME;
84		hints.ai_family = PF_UNSPEC;
85		hints.ai_socktype = SOCK_STREAM;
86		(void)snprintf(num, sizeof(num), "%u",
87		    (unsigned int)ntohs(rport));
88		error = getaddrinfo(*ahost, num, &hints, &res);
89		if (error) {
90			fprintf(stderr, "rcmdsh: getaddrinfo: %s\n",
91				gai_strerror(error));
92			return (-1);
93		}
94		if (res->ai_canonname) {
95			strncpy(hbuf, res->ai_canonname, sizeof(hbuf) - 1);
96			hbuf[sizeof(hbuf) - 1] = '\0';
97			*ahost = hbuf;
98		}
99		freeaddrinfo(res);
100	}
101
102	/* Get a socketpair we'll use for stdin and stdout. */
103	if (_socketpair(AF_UNIX, SOCK_STREAM, PF_UNSPEC, sp) == -1) {
104		perror("rcmdsh: socketpair");
105		return (-1);
106	}
107
108	cpid = fork();
109	if (cpid == -1) {
110		perror("rcmdsh: fork failed");
111		return (-1);
112	} else if (cpid == 0) {
113		/*
114		 * Child.  We use sp[1] to be stdin/stdout, and close sp[0].
115		 */
116		(void)_close(sp[0]);
117		if (_dup2(sp[1], 0) == -1 || _dup2(0, 1) == -1) {
118			perror("rcmdsh: dup2 failed");
119			_exit(255);
120		}
121		/* Fork again to lose parent. */
122		cpid = fork();
123		if (cpid == -1) {
124			perror("rcmdsh: fork to lose parent failed");
125			_exit(255);
126		}
127		if (cpid > 0)
128			_exit(0);
129
130		/* In grandchild here.  Become local user for rshprog. */
131		if (setuid(pw->pw_uid) == -1) {
132			(void)fprintf(stderr, "rcmdsh: setuid(%u): %s\n",
133			    pw->pw_uid, strerror(errno));
134			_exit(255);
135		}
136
137		/*
138		 * If remote host is "localhost" and local and remote users
139		 * are the same, avoid running remote shell for efficiency.
140		 */
141		if (strcmp(*ahost, "localhost") == 0 &&
142		    strcmp(locuser, remuser) == 0) {
143			if (pw->pw_shell[0] == '\0')
144				rshprog = _PATH_BSHELL;
145			else
146				rshprog = pw->pw_shell;
147			p = strrchr(rshprog, '/');
148			execlp(rshprog, p ? p + 1 : rshprog, "-c", cmd,
149			    (char *)NULL);
150		} else {
151			p = strrchr(rshprog, '/');
152			execlp(rshprog, p ? p + 1 : rshprog, *ahost, "-l",
153			    remuser, cmd, (char *)NULL);
154		}
155		(void)fprintf(stderr, "rcmdsh: execlp %s failed: %s\n",
156		    rshprog, strerror(errno));
157		_exit(255);
158	} else {
159		/* Parent. close sp[1], return sp[0]. */
160		(void)_close(sp[1]);
161		/* Reap child. */
162		(void)_waitpid(cpid, NULL, 0);
163		return (sp[0]);
164	}
165	/* NOTREACHED */
166}
167