usr/src/lib/libwrap/shell_cmd.c

   1 /*
   2  * Copyright 2004 Sun Microsystems, Inc.  All rights reserved.
   3  * Use is subject to license terms.
   4  */
   5
   6 #pragma ident   "%Z%%M% %I%     %E% SMI"
   7
   8  /*
   9   * shell_cmd() takes a shell command after %<character> substitutions. The
  10   * command is executed by a /bin/sh child process, with standard input,
  11   * standard output and standard error connected to /dev/null.
  12   *
  13   * Diagnostics are reported through syslog(3).
  14   *
  15   * Author: Wietse Venema, Eindhoven University of Technology, The Netherlands.
  16   */
  17
  18 #ifndef lint
  19 static char sccsid[] = "@(#) shell_cmd.c 1.5 94/12/28 17:42:44";
  20 #endif
  21
  22 /* System libraries. */
  23
  24 #include <sys/types.h>
  25 #include <sys/param.h>
  26 #include <signal.h>
  27 #include <stdio.h>
  28 #include <stdlib.h>
  29 #include <unistd.h>
  30 #include <wait.h>
  31 #include <fcntl.h>
  32 #include <syslog.h>
  33 #include <string.h>
  34
  35 extern void exit();
  36
  37 /* Local stuff. */
  38
  39 #include "tcpd.h"
  40
  41 /* Forward declarations. */
  42
  43 static void do_child();
  44
  45 /* shell_cmd - execute shell command */
  46
  47 void    shell_cmd(command)
  48 char   *command;
  49 {
  50     int     child_pid;
  51     int     wait_pid;
  52
  53     /*
  54      * Most of the work is done within the child process, to minimize the
  55      * risk of damage to the parent.
  56      */
  57
  58     switch (child_pid = fork()) {
  59     case -1:                                    /* error */
  60         tcpd_warn("cannot fork: %m");
  61         break;
  62     case 00:                                    /* child */
  63         do_child(command);
  64         /* NOTREACHED */
  65     default:                                    /* parent */
  66         while ((wait_pid = wait((int *) 0)) != -1 && wait_pid != child_pid)
  67              /* void */ ;
  68     }
  69 }
  70
  71 /* do_child - exec command with { stdin, stdout, stderr } to /dev/null */
  72
  73 static void do_child(command)
  74 char   *command;
  75 {
  76     char   *error;
  77     int     tmp_fd;
  78
  79     /*
  80      * Systems with POSIX sessions may send a SIGHUP to grandchildren if the
  81      * child exits first. This is sick, sessions were invented for terminals.
  82      */
  83
  84     signal(SIGHUP, SIG_IGN);
  85
  86     /* Set up new stdin, stdout, stderr, and exec the shell command. */
  87
  88     for (tmp_fd = 0; tmp_fd < 3; tmp_fd++)
  89         (void) close(tmp_fd);
  90     if (open("/dev/null", 2) != 0) {
  91         error = "open /dev/null: %m";
  92     } else if (dup(0) != 1 || dup(0) != 2) {
  93         error = "dup: %m";
  94     } else {
  95         (void) execl("/bin/sh", "sh", "-c", command, (char *) 0);
  96         error = "execl /bin/sh: %m";
  97     }
  98
  99     /* Something went wrong. We MUST terminate the child process. */
 100
 101     tcpd_warn(error);
 102     _exit(0);
 103 }