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 #include <sys/types.h>
38 #include <machine/endian.h>
39
40 #include <sys/types.h>
41 #include <sys/socket.h>
42 #include <sys/wait.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 */
61 int
rcmdsh(ahost,rport,locuser,remuser,cmd,rshprog)62 rcmdsh(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), "%d", ntohs(rport));
91 error = getaddrinfo(*ahost, num, &hints, &res);
92 if (error) {
93 fprintf(stderr, "rcmdsh: getaddrinfo: %s\n",
94 gai_strerror(error));
95 return (-1);
96 }
97 if (res->ai_canonname) {
98 strncpy(hbuf, res->ai_canonname, sizeof(hbuf) - 1);
99 hbuf[sizeof(hbuf) - 1] = '\0';
100 *ahost = hbuf;
101 }
102 freeaddrinfo(res);
103 }
104
105 /* Get a socketpair we'll use for stdin and stdout. */
106 if (socketpair(AF_UNIX, SOCK_STREAM, PF_UNSPEC, sp) == -1) {
107 perror("rcmdsh: socketpair");
108 return (-1);
109 }
110
111 cpid = fork();
112 if (cpid == -1) {
113 perror("rcmdsh: fork failed");
114 return (-1);
115 } else if (cpid == 0) {
116 /*
117 * Child. We use sp[1] to be stdin/stdout, and close sp[0].
118 */
119 (void)close(sp[0]);
120 if (dup2(sp[1], 0) == -1 || dup2(0, 1) == -1) {
121 perror("rcmdsh: dup2 failed");
122 _exit(255);
123 }
124 /* Fork again to lose parent. */
125 cpid = fork();
126 if (cpid == -1) {
127 perror("rcmdsh: fork to lose parent failed");
128 _exit(255);
129 }
130 if (cpid > 0)
131 _exit(0);
132
133 /* In grandchild here. Become local user for rshprog. */
134 if (setuid(pw->pw_uid) == -1) {
135 (void)fprintf(stderr, "rcmdsh: setuid(%u): %s\n",
136 pw->pw_uid, strerror(errno));
137 _exit(255);
138 }
139
140 /*
141 * If remote host is "localhost" and local and remote users
142 * are the same, avoid running remote shell for efficiency.
143 */
144 if (strcmp(*ahost, "localhost") == 0 &&
145 strcmp(locuser, remuser) == 0) {
146 if (pw->pw_shell[0] == '\0')
147 rshprog = _PATH_BSHELL;
148 else
149 rshprog = pw->pw_shell;
150 p = strrchr(rshprog, '/');
151 execlp(rshprog, p ? p + 1 : rshprog, "-c", cmd,
152 (char *)NULL);
153 } else {
154 p = strrchr(rshprog, '/');
155 execlp(rshprog, p ? p + 1 : rshprog, *ahost, "-l",
156 remuser, cmd, (char *)NULL);
157 }
158 (void)fprintf(stderr, "rcmdsh: execlp %s failed: %s\n",
159 rshprog, strerror(errno));
160 _exit(255);
161 } else {
162 /* Parent. close sp[1], return sp[0]. */
163 (void)close(sp[1]);
164 /* Reap child. */
165 (void)wait(NULL);
166 return (sp[0]);
167 }
168 /* NOTREACHED */
169 }
170