rcmdsh.c revision 111618 
1/*	$OpenBSD: rcmdsh.c,v 1.5 1998/04/25 16:23:58 millert Exp $	*/
2
3/*
4 * Copyright (c) 2001, MagniComp
5 * All rights reserved.
6 *
7 * Redistribution and use in source and binary forms, with or without
8 * modification, are permitted provided that the following conditions
9 * are met:
10 * 1. Redistributions of source code must retain the above copyright
11 *    notice, this list of conditions and the following disclaimer.
12 * 2. Redistributions in binary form must reproduce the above copyright
13 *    notice, this list of conditions and the following disclaimer in
14 *    the documentation and/or other materials provided with the distribution.
15 * 3. Neither the name of the MagniComp nor the names of its contributors may
16 *    be used to endorse or promote products derived from this software
17 *    without specific prior written permission.
18 *
19 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
20 * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
21 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
22 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE FOR
23 * ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
24 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
25 * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
26 * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
27 * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE
28 * USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
29 */
30
31/*
32 * This is an rcmd() replacement originally by
33 * Chris Siebenmann <cks@utcc.utoronto.ca>.
34 */
35
36#include <sys/cdefs.h>
37__FBSDID("$FreeBSD: head/lib/libc/net/rcmdsh.c 111618 2003-02-27 13:40:01Z nectar $");
38
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
52#ifndef _PATH_RSH
53#define	_PATH_RSH	"/usr/bin/rsh"
54#endif
55
56/*
57 * This is a replacement rcmd() function that uses the rsh(1)
58 * program in place of a direct rcmd(3) function call so as to
59 * avoid having to be root.  Note that rport is ignored.
60 */
61int
62rcmdsh(ahost, rport, locuser, remuser, cmd, rshprog)
63	char **ahost;
64	int rport;
65	const char *locuser, *remuser, *cmd, *rshprog;
66{
67	struct addrinfo hints, *res;
68	int cpid, sp[2], error;
69	char *p;
70	struct passwd *pw;
71	char num[8];
72	static char hbuf[NI_MAXHOST];
73
74	/* What rsh/shell to use. */
75	if (rshprog == NULL)
76		rshprog = _PATH_RSH;
77
78	/* locuser must exist on this host. */
79	if ((pw = getpwnam(locuser)) == NULL) {
80		(void)fprintf(stderr, "rcmdsh: unknown user: %s\n", locuser);
81		return (-1);
82	}
83
84	/* Validate remote hostname. */
85	if (strcmp(*ahost, "localhost") != 0) {
86		memset(&hints, 0, sizeof(hints));
87		hints.ai_flags = AI_CANONNAME;
88		hints.ai_family = PF_UNSPEC;
89		hints.ai_socktype = SOCK_STREAM;
90		(void)snprintf(num, sizeof(num), "%u",
91		    (unsigned int)ntohs(rport));
92		error = getaddrinfo(*ahost, num, &hints, &res);
93		if (error) {
94			fprintf(stderr, "rcmdsh: getaddrinfo: %s\n",
95				gai_strerror(error));
96			return (-1);
97		}
98		if (res->ai_canonname) {
99			strncpy(hbuf, res->ai_canonname, sizeof(hbuf) - 1);
100			hbuf[sizeof(hbuf) - 1] = '\0';
101			*ahost = hbuf;
102		}
103		freeaddrinfo(res);
104	}
105
106	/* Get a socketpair we'll use for stdin and stdout. */
107	if (socketpair(AF_UNIX, SOCK_STREAM, PF_UNSPEC, sp) == -1) {
108		perror("rcmdsh: socketpair");
109		return (-1);
110	}
111
112	cpid = fork();
113	if (cpid == -1) {
114		perror("rcmdsh: fork failed");
115		return (-1);
116	} else if (cpid == 0) {
117		/*
118		 * Child.  We use sp[1] to be stdin/stdout, and close sp[0].
119		 */
120		(void)close(sp[0]);
121		if (dup2(sp[1], 0) == -1 || dup2(0, 1) == -1) {
122			perror("rcmdsh: dup2 failed");
123			_exit(255);
124		}
125		/* Fork again to lose parent. */
126		cpid = fork();
127		if (cpid == -1) {
128			perror("rcmdsh: fork to lose parent failed");
129			_exit(255);
130		}
131		if (cpid > 0)
132			_exit(0);
133
134		/* In grandchild here.  Become local user for rshprog. */
135		if (setuid(pw->pw_uid) == -1) {
136			(void)fprintf(stderr, "rcmdsh: setuid(%u): %s\n",
137			    pw->pw_uid, strerror(errno));
138			_exit(255);
139		}
140
141		/*
142		 * If remote host is "localhost" and local and remote users
143		 * are the same, avoid running remote shell for efficiency.
144		 */
145		if (strcmp(*ahost, "localhost") == 0 &&
146		    strcmp(locuser, remuser) == 0) {
147			if (pw->pw_shell[0] == '\0')
148				rshprog = _PATH_BSHELL;
149			else
150				rshprog = pw->pw_shell;
151			p = strrchr(rshprog, '/');
152			execlp(rshprog, p ? p + 1 : rshprog, "-c", cmd,
153			    (char *)NULL);
154		} else {
155			p = strrchr(rshprog, '/');
156			execlp(rshprog, p ? p + 1 : rshprog, *ahost, "-l",
157			    remuser, cmd, (char *)NULL);
158		}
159		(void)fprintf(stderr, "rcmdsh: execlp %s failed: %s\n",
160		    rshprog, strerror(errno));
161		_exit(255);
162	} else {
163		/* Parent. close sp[1], return sp[0]. */
164		(void)close(sp[1]);
165		/* Reap child. */
166		(void)wait(NULL);
167		return (sp[0]);
168	}
169	/* NOTREACHED */
170}
171