1 /* $OpenBSD: rcmdsh.c,v 1.7 2002/03/12 00:05:44 millert Exp $ */
2
3 /*-
4 * SPDX-License-Identifier: BSD-3-Clause
5 *
6 * Copyright (c) 2001, MagniComp
7 * All rights reserved.
8 *
9 * Redistribution and use in source and binary forms, with or without
10 * modification, are permitted provided that the following conditions
11 * are met:
12 * 1. Redistributions of source code must retain the above copyright
13 * notice, this list of conditions and the following disclaimer.
14 * 2. Redistributions in binary form must reproduce the above copyright
15 * notice, this list of conditions and the following disclaimer in
16 * the documentation and/or other materials provided with the distribution.
17 * 3. Neither the name of the MagniComp nor the names of its contributors may
18 * be used to endorse or promote products derived from this software
19 * without specific prior written permission.
20 *
21 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
22 * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
23 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
24 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE FOR
25 * ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
26 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
27 * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
28 * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
29 * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE
30 * USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
31 */
32
33 /*
34 * This is an rcmd() replacement originally by
35 * Chris Siebenmann <cks@utcc.utoronto.ca>.
36 */
37
38 #include "namespace.h"
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 #include "un-namespace.h"
52
53 /*
54 * This is a replacement rcmd() function that uses the rsh(1)
55 * program in place of a direct rcmd(3) function call so as to
56 * avoid having to be root. Note that rport is ignored.
57 */
58 int
rcmdsh(char ** ahost,int rport,const char * locuser,const char * remuser,const char * cmd,const char * rshprog)59 rcmdsh(char **ahost, int rport, const char *locuser, const char *remuser,
60 const char *cmd, const char *rshprog)
61 {
62 struct addrinfo hints, *res;
63 int sp[2], error;
64 pid_t cpid;
65 char *p;
66 struct passwd *pw;
67 char num[8];
68 static char hbuf[NI_MAXHOST];
69
70 /* What rsh/shell to use. */
71 if (rshprog == NULL)
72 rshprog = _PATH_RSH;
73
74 /* locuser must exist on this host. */
75 if ((pw = getpwnam(locuser)) == NULL) {
76 (void)fprintf(stderr, "rcmdsh: unknown user: %s\n", locuser);
77 return (-1);
78 }
79
80 /* Validate remote hostname. */
81 if (strcmp(*ahost, "localhost") != 0) {
82 memset(&hints, 0, sizeof(hints));
83 hints.ai_flags = AI_CANONNAME;
84 hints.ai_family = PF_UNSPEC;
85 hints.ai_socktype = SOCK_STREAM;
86 (void)snprintf(num, sizeof(num), "%u",
87 (unsigned int)ntohs(rport));
88 error = getaddrinfo(*ahost, num, &hints, &res);
89 if (error) {
90 fprintf(stderr, "rcmdsh: getaddrinfo: %s\n",
91 gai_strerror(error));
92 return (-1);
93 }
94 if (res->ai_canonname) {
95 strncpy(hbuf, res->ai_canonname, sizeof(hbuf) - 1);
96 hbuf[sizeof(hbuf) - 1] = '\0';
97 *ahost = hbuf;
98 }
99 freeaddrinfo(res);
100 }
101
102 /* Get a socketpair we'll use for stdin and stdout. */
103 if (_socketpair(AF_UNIX, SOCK_STREAM, PF_UNSPEC, sp) == -1) {
104 perror("rcmdsh: socketpair");
105 return (-1);
106 }
107
108 cpid = fork();
109 if (cpid == -1) {
110 perror("rcmdsh: fork failed");
111 return (-1);
112 } else if (cpid == 0) {
113 /*
114 * Child. We use sp[1] to be stdin/stdout, and close sp[0].
115 */
116 (void)_close(sp[0]);
117 if (_dup2(sp[1], 0) == -1 || _dup2(0, 1) == -1) {
118 perror("rcmdsh: dup2 failed");
119 _exit(255);
120 }
121 /* Fork again to lose parent. */
122 cpid = fork();
123 if (cpid == -1) {
124 perror("rcmdsh: fork to lose parent failed");
125 _exit(255);
126 }
127 if (cpid > 0)
128 _exit(0);
129
130 /* In grandchild here. Become local user for rshprog. */
131 if (setuid(pw->pw_uid) == -1) {
132 (void)fprintf(stderr, "rcmdsh: setuid(%u): %s\n",
133 pw->pw_uid, strerror(errno));
134 _exit(255);
135 }
136
137 /*
138 * If remote host is "localhost" and local and remote users
139 * are the same, avoid running remote shell for efficiency.
140 */
141 if (strcmp(*ahost, "localhost") == 0 &&
142 strcmp(locuser, remuser) == 0) {
143 if (pw->pw_shell[0] == '\0')
144 rshprog = _PATH_BSHELL;
145 else
146 rshprog = pw->pw_shell;
147 p = strrchr(rshprog, '/');
148 execlp(rshprog, p ? p + 1 : rshprog, "-c", cmd,
149 (char *)NULL);
150 } else {
151 p = strrchr(rshprog, '/');
152 execlp(rshprog, p ? p + 1 : rshprog, *ahost, "-l",
153 remuser, cmd, (char *)NULL);
154 }
155 (void)fprintf(stderr, "rcmdsh: execlp %s failed: %s\n",
156 rshprog, strerror(errno));
157 _exit(255);
158 } else {
159 /* Parent. close sp[1], return sp[0]. */
160 (void)_close(sp[1]);
161 /* Reap child. */
162 (void)_waitpid(cpid, NULL, 0);
163 return (sp[0]);
164 }
165 /* NOTREACHED */
166 }
167