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("$FreeBSD$");
38
39#include "namespace.h"
40#include <sys/types.h>
41#include <sys/socket.h>
42#include <sys/wait.h>
43#include <arpa/inet.h>
44
45#include <errno.h>
46#include <netdb.h>
47#include <paths.h>
48#include <pwd.h>
49#include <stdio.h>
50#include <string.h>
51#include <unistd.h>
52#include "un-namespace.h"
53
54/*
55 * This is a replacement rcmd() function that uses the rsh(1)
56 * program in place of a direct rcmd(3) function call so as to
57 * avoid having to be root.  Note that rport is ignored.
58 */
59int
60rcmdsh(char **ahost, int rport, const char *locuser, const char *remuser,
61    const char *cmd, const char *rshprog)
62{
63	struct addrinfo hints, *res;
64	int sp[2], error;
65	pid_t cpid;
66	char *p;
67	struct passwd *pw;
68	char num[8];
69	static char hbuf[NI_MAXHOST];
70
71	/* What rsh/shell to use. */
72	if (rshprog == NULL)
73		rshprog = _PATH_RSH;
74
75	/* locuser must exist on this host. */
76	if ((pw = getpwnam(locuser)) == NULL) {
77		(void)fprintf(stderr, "rcmdsh: unknown user: %s\n", locuser);
78		return (-1);
79	}
80
81	/* Validate remote hostname. */
82	if (strcmp(*ahost, "localhost") != 0) {
83		memset(&hints, 0, sizeof(hints));
84		hints.ai_flags = AI_CANONNAME;
85		hints.ai_family = PF_UNSPEC;
86		hints.ai_socktype = SOCK_STREAM;
87		(void)snprintf(num, sizeof(num), "%u",
88		    (unsigned int)ntohs(rport));
89		error = getaddrinfo(*ahost, num, &hints, &res);
90		if (error) {
91			fprintf(stderr, "rcmdsh: getaddrinfo: %s\n",
92				gai_strerror(error));
93			return (-1);
94		}
95		if (res->ai_canonname) {
96			strncpy(hbuf, res->ai_canonname, sizeof(hbuf) - 1);
97			hbuf[sizeof(hbuf) - 1] = '\0';
98			*ahost = hbuf;
99		}
100		freeaddrinfo(res);
101	}
102
103	/* Get a socketpair we'll use for stdin and stdout. */
104	if (_socketpair(AF_UNIX, SOCK_STREAM, PF_UNSPEC, sp) == -1) {
105		perror("rcmdsh: socketpair");
106		return (-1);
107	}
108
109	cpid = fork();
110	if (cpid == -1) {
111		perror("rcmdsh: fork failed");
112		return (-1);
113	} else if (cpid == 0) {
114		/*
115		 * Child.  We use sp[1] to be stdin/stdout, and close sp[0].
116		 */
117		(void)_close(sp[0]);
118		if (_dup2(sp[1], 0) == -1 || _dup2(0, 1) == -1) {
119			perror("rcmdsh: dup2 failed");
120			_exit(255);
121		}
122		/* Fork again to lose parent. */
123		cpid = fork();
124		if (cpid == -1) {
125			perror("rcmdsh: fork to lose parent failed");
126			_exit(255);
127		}
128		if (cpid > 0)
129			_exit(0);
130
131		/* In grandchild here.  Become local user for rshprog. */
132		if (setuid(pw->pw_uid) == -1) {
133			(void)fprintf(stderr, "rcmdsh: setuid(%u): %s\n",
134			    pw->pw_uid, strerror(errno));
135			_exit(255);
136		}
137
138		/*
139		 * If remote host is "localhost" and local and remote users
140		 * are the same, avoid running remote shell for efficiency.
141		 */
142		if (strcmp(*ahost, "localhost") == 0 &&
143		    strcmp(locuser, remuser) == 0) {
144			if (pw->pw_shell[0] == '\0')
145				rshprog = _PATH_BSHELL;
146			else
147				rshprog = pw->pw_shell;
148			p = strrchr(rshprog, '/');
149			execlp(rshprog, p ? p + 1 : rshprog, "-c", cmd,
150			    (char *)NULL);
151		} else {
152			p = strrchr(rshprog, '/');
153			execlp(rshprog, p ? p + 1 : rshprog, *ahost, "-l",
154			    remuser, cmd, (char *)NULL);
155		}
156		(void)fprintf(stderr, "rcmdsh: execlp %s failed: %s\n",
157		    rshprog, strerror(errno));
158		_exit(255);
159	} else {
160		/* Parent. close sp[1], return sp[0]. */
161		(void)_close(sp[1]);
162		/* Reap child. */
163		(void)_waitpid(cpid, NULL, 0);
164		return (sp[0]);
165	}
166	/* NOTREACHED */
167}
168