usr/src/libexec/rshd/rshd.c

/*
 * Copyright (c) 1983 Regents of the University of California.
 * All rights reserved.  The Berkeley software License Agreement
 * specifies the terms and conditions for redistribution.
 */

#ifndef lint
char copyright[] =
"@(#) Copyright (c) 1983 Regents of the University of California.\n\
 All rights reserved.\n";
#endif not lint

#ifndef lint
static char sccsid[] = "@(#)rshd.c      5.5 (Berkeley) %G%";
#endif not lint

/*
 * remote shell server:
 *      remuser\0
 *      locuser\0
 *      command\0
 *      data
 */
#include <sys/ioctl.h>
#include <sys/param.h>
#include <sys/socket.h>
#include <sys/wait.h>

#include <netinet/in.h>

#include <arpa/inet.h>

#include <stdio.h>
#include <errno.h>
#include <pwd.h>
#include <signal.h>
#include <netdb.h>
#include <syslog.h>

int     errno;
char    *index(), *rindex();
/* VARARGS 1 */
int     error();

main(argc, argv)
        int argc;
        char **argv;
{
        struct linger linger;
        int on = 1, fromlen;
        struct sockaddr_in from;

        openlog("rsh", LOG_PID | LOG_ODELAY, LOG_DAEMON);
        fromlen = sizeof (from);
        if (getpeername(0, &from, &fromlen) < 0) {
                fprintf(stderr, "%s: ", argv[0]);
                perror("getpeername");
                _exit(1);
        }
        if (setsockopt(0, SOL_SOCKET, SO_KEEPALIVE, &on, sizeof (on)) < 0) {
                syslog(LOG_WARNING, "setsockopt (SO_KEEPALIVE): %m");
        }
        linger.l_onoff = 1;
        linger.l_linger = 60;                   /* XXX */
        if (setsockopt(0, SOL_SOCKET, SO_LINGER, &linger, sizeof (linger)) < 0) {
                syslog(LOG_WARNING, "setsockopt (SO_LINGER): %m");
        }
        doit(dup(0), &from);
}

char    username[20] = "USER=";
char    homedir[64] = "HOME=";
char    shell[64] = "SHELL=";
char    *envinit[] =
            {homedir, shell, "PATH=:/usr/ucb:/bin:/usr/bin", username, 0};
char    **environ;

doit(f, fromp)
        int f;
        struct sockaddr_in *fromp;
{
        char cmdbuf[NCARGS+1], *cp;
        char locuser[16], remuser[16];
        struct passwd *pwd;
        int s, backoff;
        struct hostent *hp;
        struct hostent hostent;
        short port;
        int pv[2], pid, ready, readfrom, cc;
        char buf[BUFSIZ], sig;
        int one = 1;

        (void) signal(SIGINT, SIG_DFL);
        (void) signal(SIGQUIT, SIG_DFL);
        (void) signal(SIGTERM, SIG_DFL);
#ifdef DEBUG
        { int t = open("/dev/tty", 2);
          if (t >= 0) {
                ioctl(t, TIOCNOTTY, (char *)0);
                (void) close(t);
          }
        }
#endif
        fromp->sin_port = ntohs((u_short)fromp->sin_port);
        if (fromp->sin_family != AF_INET ||
            fromp->sin_port >= IPPORT_RESERVED) {
                syslog(LOG_ERR, "malformed from address\n");
                exit(1);
        }
        (void) alarm(60);
        port = 0;
        for (;;) {
                char c;
                if (read(f, &c, 1) != 1) {
                        syslog(LOG_ERR, "read: %m");
                        shutdown(f, 1+1);
                        exit(1);
                }
                if (c == 0)
                        break;
                port = port * 10 + c - '0';
        }
        (void) alarm(0);
        if (port != 0) {
                int lport = IPPORT_RESERVED - 1, retryshift;
                s = rresvport(&lport);
                if (s < 0) {
                        syslog(LOG_ERR, "can't get stderr port: %m");
                        exit(1);
                }
                if (port >= IPPORT_RESERVED) {
                        syslog(LOG_ERR, "2nd port not reserved\n");
                        exit(1);
                }
                fromp->sin_port = htons((u_short)port);
                if (connect(s, fromp, sizeof (*fromp), 0) < 0) {
                        syslog(LOG_ERR, "connect: %m");
                        exit(1);
                }
        }
        dup2(f, 0);
        dup2(f, 1);
        dup2(f, 2);
        hp = gethostbyaddr(&fromp->sin_addr, sizeof (struct in_addr),
                fromp->sin_family);
        if (hp == 0) {
                /*
                 * Only the name is used below
                 */
                hp = &hostent;
                hp->h_name = inet_ntoa(fromp->sin_addr);
        }
        getstr(remuser, sizeof(remuser), "remuser");
        getstr(locuser, sizeof(locuser), "locuser");
        getstr(cmdbuf, sizeof(cmdbuf), "command");
        setpwent();
        pwd = getpwnam(locuser);
        if (pwd == NULL) {
                error("Login incorrect.\n");
                exit(1);
        }
        endpwent();
        if (chdir(pwd->pw_dir) < 0) {
                chdir("/");
#ifdef notdef
                error("No remote directory.\n");
                exit(1);
#endif
        }
        if (pwd->pw_passwd != 0 && *pwd->pw_passwd != '\0' &&
            ruserok(hp->h_name, pwd->pw_uid == 0, remuser, locuser) < 0) {
                error("Permission denied.\n");
                exit(1);
        }
        (void) write(2, "\0", 1);
        if (port) {
                if (pipe(pv) < 0) {
                        error("Can't make pipe.\n");
                        exit(1);
                }
                pid = fork();
                if (pid == -1)  {
                        error("Try again.\n");
                        exit(1);
                }
                if (pid) {
                        (void) close(0); (void) close(1); (void) close(2);
                        (void) close(f); (void) close(pv[1]);
                        readfrom = (1<<s) | (1<<pv[0]);
                        ioctl(pv[1], FIONBIO, (char *)&one);
                        /* should set s nbio! */
                        do {
                                ready = readfrom;
                                if (select(16, &ready, 0, 0, 0) < 0)
                                        break;
                                if (ready & (1<<s)) {
                                        if (read(s, &sig, 1) <= 0)
                                                readfrom &= ~(1<<s);
                                        else
                                                killpg(pid, sig);
                                }
                                if (ready & (1<<pv[0])) {
                                        errno = 0;
                                        cc = read(pv[0], buf, sizeof (buf));
                                        if (cc <= 0) {
                                                shutdown(s, 1+1);
                                                readfrom &= ~(1<<pv[0]);
                                        } else
                                                (void) write(s, buf, cc);
                                }
                        } while (readfrom);
                        exit(0);
                }
                setpgrp(0, getpid());
                (void) close(s); (void) close(pv[0]);
                dup2(pv[1], 2);
        }
        if (*pwd->pw_shell == '\0')
                pwd->pw_shell = "/bin/sh";
        (void) close(f);
        (void) setgid(pwd->pw_gid);
        initgroups(pwd->pw_name, pwd->pw_gid);
        (void) setuid(pwd->pw_uid);
        environ = envinit;
        strncat(homedir, pwd->pw_dir, sizeof(homedir)-6);
        strncat(shell, pwd->pw_shell, sizeof(shell)-7);
        strncat(username, pwd->pw_name, sizeof(username)-6);
        cp = rindex(pwd->pw_shell, '/');
        if (cp)
                cp++;
        else
                cp = pwd->pw_shell;
        execl(pwd->pw_shell, cp, "-c", cmdbuf, 0);
        perror(pwd->pw_shell);
        exit(1);
protofail:
        error("rsh: protocol failure detected by remote\n");
        exit(1);
}

/* VARARGS 1 */
error(fmt, a1, a2, a3)
        char *fmt;
        int a1, a2, a3;
{
        char buf[BUFSIZ];

        buf[0] = 1;
        (void) sprintf(buf+1, fmt, a1, a2, a3);
        (void) write(2, buf, strlen(buf));
}

getstr(buf, cnt, err)
        char *buf;
        int cnt;
        char *err;
{
        char c;

        do {
                if (read(0, &c, 1) != 1)
                        exit(1);
                *buf++ = c;
                if (--cnt == 0) {
                        error("%s too long\n", err);
                        exit(1);
                }
        } while (c != 0);
}