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rshrcmd.c

/*
 * This is an rcmd() replacement originally by 
 * Chris Siebenmann <cks@utcc.utoronto.ca>.
 */

#ifndef lint
static const char rcsid[] =
  "$FreeBSD$";
#endif /* not lint */

#include    "defs.h"

#if   !defined(DIRECT_RCMD)

#include      <sys/socket.h>
#include      <sys/wait.h>
#include      <signal.h>
#include      <netdb.h>

static char *
xbasename(s)
      char *s;
{
      char *ret;

      ret = strrchr(s, '/');
      if (ret && ret[1])
            return (ret + 1);
      return s;
}


/*
 * This is a replacement rcmd() function that uses the rsh(1c)
 * program in place of a direct rcmd() function call so as to
 * avoid having to be root.
 */
int
rshrcmd(ahost, port, luser, ruser, cmd, fd2p)
      char        **ahost;
      u_short     port;
      char  *luser, *ruser, *cmd;
      int   *fd2p;
{
      int             cpid;
      struct hostent  *hp;
      int             sp[2];

      /* insure that we are indeed being used as we thought. */
      if (fd2p != 0)
            return -1;
      /* validate remote hostname. */
      hp = gethostbyname(*ahost);
      if (hp == 0) {
            error("%s: unknown host", *ahost);
            return -1;
      }
      /* *ahost = hp->h_name; *//* This makes me nervous. */

      /* get a socketpair we'll use for stdin and stdout. */
      if (socketpair(AF_UNIX, SOCK_STREAM, 0, sp) < 0) {
            error("socketpair(AF_UNIX, SOCK_STREAM, 0) failed: %s.", 
                  strerror(errno));
            return -1;
      }

      cpid = fork();
      if (cpid < 0) {
            error("fork failed: %s.", strerror(errno));
            return -1;      /* error. */
      }
      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) {
                  error("dup2 failed: %s.", strerror(errno));
                  _exit(255);
            }
            /* fork again to lose parent. */
            cpid = fork();
            if (cpid < 0) {
                  error("fork to lose parent failed: %s.", strerror(errno));
                  _exit(255);
            }
            if (cpid > 0)
                  _exit(0);
            /* in grandchild here. */

            /*
             * If we are rdist'ing to "localhost" as the same user
             * as we are, then avoid running remote shell for efficiency.
             */
            if (strcmp(*ahost, "localhost") == 0 &&
                strcmp(luser, ruser) == 0) {
                  execlp(_PATH_BSHELL, xbasename(_PATH_BSHELL), "-c",
                         cmd, (char *) NULL);
                  error("execlp %s failed: %s.", _PATH_BSHELL, strerror(errno));
            } else {
                  execlp(path_rsh, xbasename(path_rsh), 
                         *ahost, "-l", ruser, cmd, (char *) NULL);
                  error("execlp %s failed: %s.", path_rsh,
                        strerror(errno));
            }
            _exit(255);
      }
      if (cpid > 0) {
            /* parent. close sp[1], return sp[0]. */
            (void) close(sp[1]);
            /* reap child. */
            (void) wait(0);
            return sp[0];
      }
      /*NOTREACHED*/
      return (-1);
}

#endif      /* !DIRECT_RCMD */

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