rcmdsh.c revision 85342 
1/*	$OpenBSD: rcmdsh.c,v 1.5 1998/04/25 16:23:58 millert Exp $	*/
2
3/*
4 * This is an rcmd() replacement originally by
5 * Chris Siebenmann <cks@utcc.utoronto.ca>.
6 *
7 * $FreeBSD: head/lib/libc/net/rcmdsh.c 85342 2001-10-23 06:22:15Z imp $
8 */
9
10#if defined(LIBC_SCCS) && !defined(lint)
11static char *rcsid = "$FreeBSD: head/lib/libc/net/rcmdsh.c 85342 2001-10-23 06:22:15Z imp $"
12#endif /* LIBC_SCCS and not lint */
13
14#include      <sys/types.h>
15#include      <sys/socket.h>
16#include      <sys/wait.h>
17#include      <signal.h>
18#include      <errno.h>
19#include      <netdb.h>
20#include      <stdio.h>
21#include      <string.h>
22#include      <pwd.h>
23#include      <paths.h>
24#include      <unistd.h>
25
26#ifndef _PATH_RSH
27#define _PATH_RSH "/usr/bin/rsh"
28#endif
29
30/*
31 * This is a replacement rcmd() function that uses the rsh(1)
32 * program in place of a direct rcmd(3) function call so as to
33 * avoid having to be root.  Note that rport is ignored.
34 */
35/* ARGSUSED */
36int
37rcmdsh(ahost, rport, locuser, remuser, cmd, rshprog)
38	char **ahost;
39	int rport;
40	const char *locuser, *remuser, *cmd;
41	char *rshprog;
42{
43	struct hostent *hp;
44	int cpid, sp[2];
45	char *p;
46	struct passwd *pw;
47
48	/* What rsh/shell to use. */
49	if (rshprog == NULL)
50		rshprog = _PATH_RSH;
51
52	/* locuser must exist on this host. */
53	if ((pw = getpwnam(locuser)) == NULL) {
54		(void) fprintf(stderr, "rcmdsh: unknown user: %s\n", locuser);
55		return(-1);
56	}
57
58	/* Validate remote hostname. */
59	if (strcmp(*ahost, "localhost") != 0) {
60		if ((hp = gethostbyname(*ahost)) == NULL) {
61			herror(*ahost);
62			return(-1);
63		}
64		*ahost = hp->h_name;
65	}
66
67	/* Get a socketpair we'll use for stdin and stdout. */
68	if (socketpair(AF_UNIX, SOCK_STREAM, PF_UNSPEC, sp) < 0) {
69		perror("rcmdsh: socketpair");
70		return(-1);
71	}
72
73	cpid = fork();
74	if (cpid < 0) {
75		perror("rcmdsh: fork failed");
76		return(-1);
77	} else if (cpid == 0) {
78		/*
79		 * Child.  We use sp[1] to be stdin/stdout, and close sp[0].
80		 */
81		(void) close(sp[0]);
82		if (dup2(sp[1], 0) < 0 || dup2(0, 1) < 0) {
83			perror("rcmdsh: dup2 failed");
84			_exit(255);
85		}
86		/* Fork again to lose parent. */
87		cpid = fork();
88		if (cpid < 0) {
89			perror("rcmdsh: fork to lose parent failed");
90			_exit(255);
91		}
92		if (cpid > 0)
93			_exit(0);
94
95		/* In grandchild here.  Become local user for rshprog. */
96		if (setuid(pw->pw_uid)) {
97			(void) fprintf(stderr, "rcmdsh: setuid(%u): %s\n",
98				       pw->pw_uid, strerror(errno));
99			_exit(255);
100		}
101
102		/*
103		 * If remote host is "localhost" and local and remote user
104		 * are the same, avoid running remote shell for efficiency.
105		 */
106		if (!strcmp(*ahost, "localhost") && !strcmp(locuser, remuser)) {
107			if (pw->pw_shell[0] == '\0')
108				rshprog = _PATH_BSHELL;
109			else
110				rshprog = pw->pw_shell;
111			p = strrchr(rshprog, '/');
112			execlp(rshprog, p ? p+1 : rshprog, "-c", cmd,
113			       (char *) NULL);
114		} else {
115			p = strrchr(rshprog, '/');
116			execlp(rshprog, p ? p+1 : rshprog, *ahost, "-l",
117			       remuser, cmd, (char *) NULL);
118		}
119		(void) fprintf(stderr, "rcmdsh: execlp %s failed: %s\n",
120			       rshprog, strerror(errno));
121		_exit(255);
122	} else {
123		/* Parent. close sp[1], return sp[0]. */
124		(void) close(sp[1]);
125		/* Reap child. */
126		(void) wait(NULL);
127		return(sp[0]);
128	}
129	/* NOTREACHED */
130}
131