Secure PHP Development- P125 docx

The getDiskInfofunction returns an array called $diskInfo, which returns each mount point file system in the system and the usage per-centage.. For each mount point returned in $diskInfo

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array_push($headers,

“Content-Type: text/plain\r\n”);

$body = implode(‘’, $message);

$search = array_keys($info);

$replace = array_values($info);

$body = preg_replace($search,

$replace,

$body);

$subject = preg_replace($search,

$replace,

$subject);

$headerStr = implode(‘’, $headers);

if (DEBUG) echo “Sending mail to: $to ($subject)\n”;

mail($to, $subject, $body, $headerStr);

}

function getDiskInfo($fs = null) {

$info = array();

foreach($fs as $disk) {

$mountPoint = $disk[‘mount’];

$percent = $disk[‘percent’];

// remove % sign

$info[$mountPoint] = substr($percent,

0, strlen($percent) -1);

} return $info;

}

?>

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This script works as follows:

1 It requires the class.Linux.inc.phpand common_functions.php

classes

2 It creates a sysinfoobject called $system, which is used to retrieve host name, IP address, and kernel information, using the chostname(),

ip_addr(), and kernel()methods

3 It calls the getDiskInfo()function with an array of disk information returned by the filesystems()method of the $systemobject

4 The getDiskInfo()function returns an array called $diskInfo, which returns each mount point (file system) in the system and the usage per-centage

5 For each mount point returned in $diskInfo, the usage percentage is compared against the maximum allowed usage percentage stored in $MAX-SIZE(from the hdmonitor.conf file)

6 If current usage is greater than or equal to the $MAXSIZEusage specified for that mount point, an alert record is appended in $alertInfo[‘/

<%DISK_STATUS%>/’] The alert count $alertis incremented

7 If disk usage alerts (i.e., $alert> 0) are found, then sendAlert()is called to e-mail the alert information stored in the $alertInfoarray Listing 16-12 shows the alert message template The To:, From:, Subject:, and Content-Type: headers are used in creating the e-mail message headers There are custom tags such as <%HOST%>, <%IP_ADDR%>, <%KERNEL%>, and <%DISK_STATUS%> These are replaced with the $alertInfo contents The following message is in HTML, but you can use plain text as well by setting the Content-Type: header to text/plain and removing HTML tags from the message body as needed

Listing 16-12: hdmonitor_mail.txt

To: kabir@example.com From: THE REDEYE GROUP <admin@example.com>

Subject: Disk(s) on <%HOST%> need your attention Content-Type: text/html

<html>

<body>

The following disk(s) have exceeded set limit in hdmonitor.conf:

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<table border=0 cellpadding=1 cellspacing=0 width=”400”

bgcolor=”#000000”>

<tr>

<td>

bgcolor=”red”>

<tr> <td> <font color=”black”> <strong> Disk Information

</strong> </font> </td> </tr>

</table>

</td>

</tr>

</table>

<br>

bgcolor=”#000000”>

<tr>

<td>

bgcolor=”#cccccc”>

<tr> <td colspan=2> System Information </td></tr>

<tr> <td>Hostname </td><td> <%HOST%></td></tr>

<tr> <td>Kernel </td><td> <%KERNEL%></td></tr>

</table>

</td>

</tr>

</table>

<br>

Thanks,

<br>

The Wheel Group

<br>

</body>

</html>

The hdmonitor.php script contains the following functions

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This function sends an e-mail message by loading the message template from the hdmonitor.conf configuration variable $GLOBALS[‘MAIL_TEMPLATE’] Each line of this message is parsed for e-mail headers such as To:, From:, Cc:, Bcc:, Subject:, and Content-Type:, which are stored in variables needed for the mail()function The lines constituting the body of the message are stored in $messages, which is later imploded into the $bodystring

The $body string is searched for special tags stored in $alertInfo, which is passed to the sendAlert()function as an associative array called $info The keys

of the $infoarray are stored in $searchusing the array_keys()function, and the values are stored in $replace using the array_values() function The $search

array contains tags such as <%HOST%>, <%IP_ADDR%>, <%DISK_STATUS%>, and so on, which were inserted into $info(i.e., $alertInfo) prior to calling the sendAlert()

function

These tags are replaced with their values in the $body string using the

preg_replace() function The fully expanded template body is e-mailed along with the $headersusing mail()

getDiskInfo()

This function returns an associative array called $infowith mount points as keys and their usage percentage as values The function is called with disk statistics as a parameter

Installing the hdmonitor tool as a cron job

To set up hdmonitor.phpas a cron job under Linux, do the following:

1 As root, create a symbolic link in /etc/cron.daily as follows:

ln -s /path/to/hdmonitor.php

For example, if you kept hdmonitor.phpand hdmonitor.confin the

/usr/local/src/hdmonitordirectory, you could run the following com-mands as root to create the link:

cd /etc/cron.daily

ln -s /usr/local/src/hdmonitor/hdmonitor.php

2 Once the symlink is created, run /etc/cron.daily/hdmonitor.php as a test

If you get an error message that hdmonitor.conf was not found, or

that any of the classes were not found (class.Linux.inc.phpor

common_functions.php), you need to edit hdmonitor.php to change

require_once(‘hdmonitor.conf’), require_once(‘class.

Linux.inc.php’), and require_once(‘common_functions.php’);

to require_once(‘/path/to/hdmonitor/hdmonitor.conf’),

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require_once(‘/path/to/hdmonitor/class.Linux.inc.php), and require_once(‘/path/to/hdmonitor/common_functions.php’), respectively For our example case, this would be require_once(‘/usr/

local/src/hdmonitor/hdmonitor.conf’), require_once(‘/usr/

local/src/hdmonitor/class.Linux.inc.php’), and require_once (‘/usr/local/src/hdmonitor/common_functions.php ‘).

3 Make sure hdmonitor.phpis executable You can run

chown root:root hdmonitor.* \

class.Linux.inc.php \ common_functions.php chmod 700 hdmonitor.php

from the directory of the script to allow root to own and be able to exe-cute the hdmonitorscripts If your cron daemon does not run as root, make sure you replace root:rootwith the appropriate user and group names that enable cron to execute the script

4 Configure the hdmonitor.conf file to reflect what mount points you want

to monitor and at what level In addition, customize the mail template as needed

5 Let cron run the job at the regularly scheduled time and you should

receive disk alert messages when any of your mount points exceeds the

$MAXSIZElimit

6 To test your installation, you can set the $MAXSIZElimits to a very low number, which will trigger an alert the next time hdmonitor.phpis run

by cron If you do not receive an alert that you expect to receive, check the var/log/cronfile for possible file execute permission issues

Building a CPU Load Monitoring Utility

In this section, we will develop a system load-average monitoring tool that will enable us to monitor a Linux system’s load average automatically, and when the load average exceeds a specified limit, an alert message will be sent out to administrators

We define multiple levels of alert so that an administrator can take appropriate actions based on the alert levels indicated

Like the hdmonitor script, this script requires the class.Linux.inc.php and common_functions.php classes from the phpSysInfo project, which is located at

http://phpsysinfo.sourceforge.net/project

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