rwalld.c

/*-
 * SPDX-License-Identifier: BSD-3-Clause
 *
 * Copyright (c) 1993 Christopher G. Demetriou
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. The name of the author may not be used to endorse or promote
 *    products derived from this software without specific prior written
 *    permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS
 * OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
 * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY
 * DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 */

#include <sys/cdefs.h>
#include <err.h>
#include <pwd.h>
#include <signal.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <syslog.h>
#include <arpa/inet.h>
#include <rpc/rpc.h>
#include <rpcsvc/rwall.h>
#include <sys/socket.h>
#include <sys/types.h>
#include <sys/wait.h>
#include <unistd.h>

#ifdef OSF
#define WALL_CMD "/usr/sbin/wall"
#else
#define WALL_CMD "/usr/bin/wall -n"
#endif

void wallprog_1(struct svc_req *rqstp, SVCXPRT *transp);
void possess(void);
void killkids(int sig);
static void usage(void) __dead2;

int nodaemon = 0;
int from_inetd = 1;

int
main(int argc, char *argv[])
{
	SVCXPRT *transp;
	socklen_t salen;
	int ok;
	struct sockaddr_storage sa;

	if (argc == 2 && !strcmp(argv[1], "-n"))
		nodaemon = 1;
	if (argc != 1 && !nodaemon)
		usage();

	if (geteuid() == 0) {
		struct passwd *pep = getpwnam("nobody");
		if (pep)
			setuid(pep->pw_uid);
		else
			setuid(getuid());
	}

        /*
         * See if inetd started us
         */
	salen = sizeof(sa);
        if (getsockname(0, (struct sockaddr *)&sa, &salen) < 0) {
                from_inetd = 0;
        }

        if (!from_inetd) {
                if (!nodaemon)
                        possess();

		(void)rpcb_unset(WALLPROG, WALLVERS, NULL);
        }

	(void)signal(SIGCHLD, killkids);

	openlog("rpc.rwalld", LOG_CONS|LOG_PID, LOG_DAEMON);

	/* create and register the service */
	if (from_inetd) {
		transp = svc_tli_create(0, NULL, NULL, 0, 0);
		if (transp == NULL) {
			syslog(LOG_ERR, "couldn't create udp service.");
			exit(1);
		}
		ok = svc_reg(transp, WALLPROG, WALLVERS,
			     wallprog_1, NULL);
	} else
		ok = svc_create(wallprog_1,
				WALLPROG, WALLVERS, "udp");
	if (!ok) {
		syslog(LOG_ERR, "unable to register (WALLPROG, WALLVERS, %s)", (!from_inetd)?"udp":"(inetd)");
		exit(1);
	}
	svc_run();
	syslog(LOG_ERR, "svc_run returned");
	exit(1);
}

static void
usage(void)
{
	fprintf(stderr, "usage: rpc.rwalld [-n]\n");
	exit(1);
}

void
possess(void)
{
	daemon(0, 0);
}

void
killkids(int sig __unused)
{
	while(wait4(-1, NULL, WNOHANG, NULL) > 0)
		;
}

void *
wallproc_wall_1_svc(wrapstring *s, struct svc_req *rqstp __unused)
{
	static void		*dummy = NULL;

	/* fork, popen wall with special option, and send the message */
	if (fork() == 0) {
		FILE *pfp;

		pfp = popen(WALL_CMD, "w");
		if (pfp != NULL) {
			fprintf(pfp, "\007\007%s", *s);
			pclose(pfp);
			exit(0);
		}
	}
	return(&dummy);
}

void
wallprog_1(struct svc_req *rqstp, SVCXPRT *transp)
{
	union {
		char *wallproc_wall_1_arg;
	} argument;
	void *result;
	xdrproc_t xdr_argument, xdr_result;
	typedef void *(svc_cb)(void *arg, struct svc_req *rqstp);
	svc_cb *local;

	switch (rqstp->rq_proc) {
	case NULLPROC:
		(void)svc_sendreply(transp, (xdrproc_t)xdr_void, NULL);
		goto leave;

	case WALLPROC_WALL:
		xdr_argument = (xdrproc_t)xdr_wrapstring;
		xdr_result = (xdrproc_t)xdr_void;
		local = (svc_cb *)wallproc_wall_1_svc;
		break;

	default:
		svcerr_noproc(transp);
		goto leave;
	}
	bzero(&argument, sizeof(argument));
	if (!svc_getargs(transp, xdr_argument, &argument)) {
		svcerr_decode(transp);
		goto leave;
	}
	result = (*local)(&argument, rqstp);
	if (result != NULL &&
	    !svc_sendreply(transp, xdr_result, result)) {
		svcerr_systemerr(transp);
	}
	if (!svc_freeargs(transp, xdr_argument, &argument)) {
		syslog(LOG_ERR, "unable to free arguments");
		exit(1);
	}
leave:
        if (from_inetd)
                exit(0);
}