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/* $OpenBSD: rcmdsh.c,v 1.6 2002/01/02 20:18:32 deraadt Exp $ */
/*
* This is an rcmd() replacement originally by
* Chris Siebenmann <cks@utcc.utoronto.ca>.
*/
#if defined(LIBC_SCCS) && !defined(lint)
static char *rcsid = "$OpenBSD: rcmdsh.c,v 1.6 2002/01/02 20:18:32 deraadt Exp $";
#endif /* LIBC_SCCS and not lint */
#include <sys/types.h>
#include <sys/socket.h>
#include <sys/wait.h>
#include <signal.h>
#include <errno.h>
#include <netdb.h>
#include <stdio.h>
#include <string.h>
#include <pwd.h>
#include <paths.h>
#include <unistd.h>
/*
* This is a replacement rcmd() function that uses the rsh(1)
* program in place of a direct rcmd(3) function call so as to
* avoid having to be root. Note that rport is ignored.
*/
/* ARGSUSED */
int
rcmdsh(ahost, rport, locuser, remuser, cmd, rshprog)
char **ahost;
int rport;
const char *locuser, *remuser, *cmd;
char *rshprog;
{
struct hostent *hp;
int sp[2];
pid_t cpid;
char *p;
struct passwd *pw;
/* What rsh/shell to use. */
if (rshprog == NULL)
rshprog = _PATH_RSH;
/* locuser must exist on this host. */
if ((pw = getpwnam(locuser)) == NULL) {
(void) fprintf(stderr, "rcmdsh: unknown user: %s\n", locuser);
return(-1);
}
/* Validate remote hostname. */
if (strcmp(*ahost, "localhost") != 0) {
if ((hp = gethostbyname(*ahost)) == NULL) {
herror(*ahost);
return(-1);
}
*ahost = hp->h_name;
}
/* Get a socketpair we'll use for stdin and stdout. */
if (socketpair(AF_UNIX, SOCK_STREAM, PF_UNSPEC, sp) < 0) {
perror("rcmdsh: socketpair");
return(-1);
}
cpid = fork();
if (cpid < 0) {
perror("rcmdsh: fork failed");
return(-1);
} else if (cpid == 0) {
/*
* Child. We use sp[1] to be stdin/stdout, and close sp[0].
*/
(void) close(sp[0]);
if (dup2(sp[1], 0) < 0 || dup2(0, 1) < 0) {
perror("rcmdsh: dup2 failed");
_exit(255);
}
/* Fork again to lose parent. */
cpid = fork();
if (cpid < 0) {
perror("rcmdsh: fork to lose parent failed");
_exit(255);
}
if (cpid > 0)
_exit(0);
/* In grandchild here. Become local user for rshprog. */
if (setuid(pw->pw_uid)) {
(void) fprintf(stderr, "rcmdsh: setuid(%u): %s\n",
pw->pw_uid, strerror(errno));
_exit(255);
}
/*
* If remote host is "localhost" and local and remote user
* are the same, avoid running remote shell for efficiency.
*/
if (!strcmp(*ahost, "localhost") && !strcmp(locuser, remuser)) {
if (pw->pw_shell[0] == '\0')
rshprog = _PATH_BSHELL;
else
rshprog = pw->pw_shell;
p = strrchr(rshprog, '/');
execlp(rshprog, p ? p+1 : rshprog, "-c", cmd,
(char *) NULL);
} else {
p = strrchr(rshprog, '/');
execlp(rshprog, p ? p+1 : rshprog, *ahost, "-l",
remuser, cmd, (char *) NULL);
}
(void) fprintf(stderr, "rcmdsh: execlp %s failed: %s\n",
rshprog, strerror(errno));
_exit(255);
} else {
/* Parent. close sp[1], return sp[0]. */
(void) close(sp[1]);
/* Reap child. */
(void) wait(NULL);
return(sp[0]);
}
/* NOTREACHED */
}
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