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