rcmdsh.c revision 286910 
1/*	$OpenBSD: rcmdsh.c,v 1.7 2002/03/12 00:05:44 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 286910 2015-08-18 22:37:25Z delphij $");
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/*
53 * This is a replacement rcmd() function that uses the rsh(1)
54 * program in place of a direct rcmd(3) function call so as to
55 * avoid having to be root.  Note that rport is ignored.
56 */
57int
58rcmdsh(char **ahost, int rport, const char *locuser, const char *remuser,
59    const char *cmd, const char *rshprog)
60{
61	struct addrinfo hints, *res;
62	int sp[2], error;
63	pid_t cpid;
64	char *p;
65	struct passwd *pw;
66	char num[8];
67	static char hbuf[NI_MAXHOST];
68
69	/* What rsh/shell to use. */
70	if (rshprog == NULL)
71		rshprog = _PATH_RSH;
72
73	/* locuser must exist on this host. */
74	if ((pw = getpwnam(locuser)) == NULL) {
75		(void)fprintf(stderr, "rcmdsh: unknown user: %s\n", locuser);
76		return (-1);
77	}
78
79	/* Validate remote hostname. */
80	if (strcmp(*ahost, "localhost") != 0) {
81		memset(&hints, 0, sizeof(hints));
82		hints.ai_flags = AI_CANONNAME;
83		hints.ai_family = PF_UNSPEC;
84		hints.ai_socktype = SOCK_STREAM;
85		(void)snprintf(num, sizeof(num), "%u",
86		    (unsigned int)ntohs(rport));
87		error = getaddrinfo(*ahost, num, &hints, &res);
88		if (error) {
89			fprintf(stderr, "rcmdsh: getaddrinfo: %s\n",
90				gai_strerror(error));
91			return (-1);
92		}
93		if (res->ai_canonname) {
94			strncpy(hbuf, res->ai_canonname, sizeof(hbuf) - 1);
95			hbuf[sizeof(hbuf) - 1] = '\0';
96			*ahost = hbuf;
97		}
98		freeaddrinfo(res);
99	}
100
101	/* Get a socketpair we'll use for stdin and stdout. */
102	if (socketpair(AF_UNIX, SOCK_STREAM, PF_UNSPEC, sp) == -1) {
103		perror("rcmdsh: socketpair");
104		return (-1);
105	}
106
107	cpid = fork();
108	if (cpid == -1) {
109		perror("rcmdsh: fork failed");
110		return (-1);
111	} else if (cpid == 0) {
112		/*
113		 * Child.  We use sp[1] to be stdin/stdout, and close sp[0].
114		 */
115		(void)close(sp[0]);
116		if (dup2(sp[1], 0) == -1 || dup2(0, 1) == -1) {
117			perror("rcmdsh: dup2 failed");
118			_exit(255);
119		}
120		/* Fork again to lose parent. */
121		cpid = fork();
122		if (cpid == -1) {
123			perror("rcmdsh: fork to lose parent failed");
124			_exit(255);
125		}
126		if (cpid > 0)
127			_exit(0);
128
129		/* In grandchild here.  Become local user for rshprog. */
130		if (setuid(pw->pw_uid) == -1) {
131			(void)fprintf(stderr, "rcmdsh: setuid(%u): %s\n",
132			    pw->pw_uid, strerror(errno));
133			_exit(255);
134		}
135
136		/*
137		 * If remote host is "localhost" and local and remote users
138		 * are the same, avoid running remote shell for efficiency.
139		 */
140		if (strcmp(*ahost, "localhost") == 0 &&
141		    strcmp(locuser, remuser) == 0) {
142			if (pw->pw_shell[0] == '\0')
143				rshprog = _PATH_BSHELL;
144			else
145				rshprog = pw->pw_shell;
146			p = strrchr(rshprog, '/');
147			execlp(rshprog, p ? p + 1 : rshprog, "-c", cmd,
148			    (char *)NULL);
149		} else {
150			p = strrchr(rshprog, '/');
151			execlp(rshprog, p ? p + 1 : rshprog, *ahost, "-l",
152			    remuser, cmd, (char *)NULL);
153		}
154		(void)fprintf(stderr, "rcmdsh: execlp %s failed: %s\n",
155		    rshprog, strerror(errno));
156		_exit(255);
157	} else {
158		/* Parent. close sp[1], return sp[0]. */
159		(void)close(sp[1]);
160		/* Reap child. */
161		(void)wait(NULL);
162		return (sp[0]);
163	}
164	/* NOTREACHED */
165}
166