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 * $FreeBSD: src/lib/libc/net/rcmdsh.c,v 1.5 2003/02/27 13:40:00 nectar Exp $
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 #ifndef _PATH_RSH
54 #define _PATH_RSH "/usr/bin/rsh"
55 #endif
56
57 /*
58 * This is a replacement rcmd() function that uses the rsh(1)
59 * program in place of a direct rcmd(3) function call so as to
60 * avoid having to be root. Note that rport is ignored.
61 */
62 int
rcmdsh(char ** ahost,int rport,const char * locuser,const char * remuser,const char * cmd,const char * rshprog)63 rcmdsh(char **ahost, int rport, const char *locuser, const char *remuser,
64 const char *cmd, const char *rshprog)
65 {
66 struct addrinfo hints, *res;
67 int sp[2], error;
68 pid_t cpid;
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 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 snprintf(num, sizeof(num), "%u", (unsigned int)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 _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 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, NULL);
152 } else {
153 p = strrchr(rshprog, '/');
154 execlp(rshprog, p ? p + 1 : rshprog, *ahost, "-l",
155 remuser, cmd, NULL);
156 }
157 fprintf(stderr, "rcmdsh: execlp %s failed: %s\n",
158 rshprog, strerror(errno));
159 _exit(255);
160 } else {
161 /* Parent. close sp[1], return sp[0]. */
162 _close(sp[1]);
163 /* Reap child. */
164 _waitpid(cpid, NULL, 0);
165 return (sp[0]);
166 }
167 /* NOTREACHED */
168 }
169