rcmdsh.c revision 94789 
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 94789 2002-04-15 18:45:20Z ume $");
38
39#include <sys/types.h>
40#include <sys/socket.h>
41#include <sys/wait.h>
42
43#include <errno.h>
44#include <netdb.h>
45#include <paths.h>
46#include <pwd.h>
47#include <stdio.h>
48#include <string.h>
49#include <unistd.h>
50
51#ifndef _PATH_RSH
52#define	_PATH_RSH	"/usr/bin/rsh"
53#endif
54
55/*
56 * This is a replacement rcmd() function that uses the rsh(1)
57 * program in place of a direct rcmd(3) function call so as to
58 * avoid having to be root.  Note that rport is ignored.
59 */
60int
61rcmdsh(ahost, rport, locuser, remuser, cmd, rshprog)
62	char **ahost;
63	int rport;
64	const char *locuser, *remuser, *cmd, *rshprog;
65{
66	struct addrinfo hints, *res;
67	int cpid, sp[2], error;
68	char *p;
69	struct passwd *pw;
70	char num[8];
71	static char hbuf[NI_MAXHOST];
72
73	/* What rsh/shell to use. */
74	if (rshprog == NULL)
75		rshprog = _PATH_RSH;
76
77	/* locuser must exist on this host. */
78	if ((pw = getpwnam(locuser)) == NULL) {
79		(void)fprintf(stderr, "rcmdsh: unknown user: %s\n", locuser);
80		return (-1);
81	}
82
83	/* Validate remote hostname. */
84	if (strcmp(*ahost, "localhost") != 0) {
85		memset(&hints, 0, sizeof(hints));
86		hints.ai_flags = AI_CANONNAME;
87		hints.ai_family = PF_UNSPEC;
88		hints.ai_socktype = SOCK_STREAM;
89		(void)snprintf(num, sizeof(num), "%d", ntohs(rport));
90		error = getaddrinfo(*ahost, num, &hints, &res);
91		if (error) {
92			fprintf(stderr, "rcmdsh: getaddrinfo: %s\n",
93				gai_strerror(error));
94			return (-1);
95		}
96		if (res->ai_canonname) {
97			strncpy(hbuf, res->ai_canonname, sizeof(hbuf) - 1);
98			hbuf[sizeof(hbuf) - 1] = '\0';
99			*ahost = hbuf;
100		}
101		freeaddrinfo(res);
102	}
103
104	/* Get a socketpair we'll use for stdin and stdout. */
105	if (socketpair(AF_UNIX, SOCK_STREAM, PF_UNSPEC, sp) == -1) {
106		perror("rcmdsh: socketpair");
107		return (-1);
108	}
109
110	cpid = fork();
111	if (cpid == -1) {
112		perror("rcmdsh: fork failed");
113		return (-1);
114	} else if (cpid == 0) {
115		/*
116		 * Child.  We use sp[1] to be stdin/stdout, and close sp[0].
117		 */
118		(void)close(sp[0]);
119		if (dup2(sp[1], 0) == -1 || dup2(0, 1) == -1) {
120			perror("rcmdsh: dup2 failed");
121			_exit(255);
122		}
123		/* Fork again to lose parent. */
124		cpid = fork();
125		if (cpid == -1) {
126			perror("rcmdsh: fork to lose parent failed");
127			_exit(255);
128		}
129		if (cpid > 0)
130			_exit(0);
131
132		/* In grandchild here.  Become local user for rshprog. */
133		if (setuid(pw->pw_uid) == -1) {
134			(void)fprintf(stderr, "rcmdsh: setuid(%u): %s\n",
135			    pw->pw_uid, strerror(errno));
136			_exit(255);
137		}
138
139		/*
140		 * If remote host is "localhost" and local and remote users
141		 * are the same, avoid running remote shell for efficiency.
142		 */
143		if (strcmp(*ahost, "localhost") == 0 &&
144		    strcmp(locuser, remuser) == 0) {
145			if (pw->pw_shell[0] == '\0')
146				rshprog = _PATH_BSHELL;
147			else
148				rshprog = pw->pw_shell;
149			p = strrchr(rshprog, '/');
150			execlp(rshprog, p ? p + 1 : rshprog, "-c", cmd,
151			    (char *)NULL);
152		} else {
153			p = strrchr(rshprog, '/');
154			execlp(rshprog, p ? p + 1 : rshprog, *ahost, "-l",
155			    remuser, cmd, (char *)NULL);
156		}
157		(void)fprintf(stderr, "rcmdsh: execlp %s failed: %s\n",
158		    rshprog, strerror(errno));
159		_exit(255);
160	} else {
161		/* Parent. close sp[1], return sp[0]. */
162		(void)close(sp[1]);
163		/* Reap child. */
164		(void)wait(NULL);
165		return (sp[0]);
166	}
167	/* NOTREACHED */
168}
169