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 */
59 int
rcmdsh(char ** ahost,int rport,const char * locuser,const char * remuser,const char * cmd,const char * rshprog)60 rcmdsh(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