source-viewer.php

<?php 
	 /* Known Vulnerabilities
	 * 
	 * Page itself is a vulnerability which shows source code. Very bad idea.
	 * Filename injection (Insecure Direct Object Reference)
	 * SQL Injection, (Fix: Use Schematized Stored Procedures)
	 * Cross Site Scripting, (Fix: Encode all output)
	 * Cross Site Request Forgery, (Fix: Tokenize transactions)
	 * Insecure Direct Object Reference, (Fix: Tokenize Object References)
	 * Denial of Service, (Fix: Truncate Log Queries)
	 * Loading of Local Files, (Fix: Tokenize Object Reference - Filename references in this case)
	 * Improper Error Handling, (Fix: Employ custom error handler)
	 * SQL Exception, (Fix: Employ custom error handler)
	 * HTTP Parameter Pollution (Fix: Scope request variables)
	 */
	try {	    	
		switch ($_SESSION["security-level"]){
	   		case "0": // This code is insecure
	   			$lEnableHTMLControls = FALSE;
	   			$lValidateAndTokenize = FALSE;
	   			$lEncodeOutput = FALSE;
	   		break;
	   			 
	   		case "1": // This code is insecure 
				$lEnableHTMLControls = TRUE;
	   			$lValidateAndTokenize = FALSE;
				$lEncodeOutput = FALSE;
	   		break;
	    		
			case "2":
			case "3":
			case "4":
	   		case "5": // This code is fairly secure
				$lEnableHTMLControls = TRUE;
	   			$lValidateAndTokenize = TRUE;
				$lEncodeOutput = TRUE;
	   		break;
	   	}// end switch ($_SESSION["security-level"])
	   	
	   	if ($lEnableHTMLControls) {
	   		$lHTMLControlAttributes='required="required"';
	   	}else{
	   		$lHTMLControlAttributes="";
	   	}// end if

	}catch(Exception $e){
		echo $CustomErrorHandler->FormatError($e, "Error in text file viewer. Cannot load file.");
	}// end try
	
	//initialize custom error handler
    require_once 'classes/DirectoryIterationHandler.php';
	if (!isset($DirectoryIterationHandler)){
		$DirectoryIterator = new DirectoryIterationHandler(".");
	}// end if
?>

<div class="page-title">Source Code Viewer</div>

<?php include_once (__ROOT__.'/includes/back-button.inc');?>
<?php include_once (__ROOT__.'/includes/hints/hints-menu-wrapper.inc'); ?>

<form 	action="index.php?page=source-viewer.php" 
		method="post" 
		enctype="application/x-www-form-urlencoded">
		
	<table>
		<tr id="id-bad-cred-tr" style="display: none;">
			<td colspan="2" class="error-message">
				Validation Error: Bad Selection
			</td>
		</tr>
		<tr><td></td></tr>
		<tr>
			<td colspan="2" class="form-header">To see the source of the file, choose and click "View File".<br />Note that not all files are listed.</td>
		</tr>
		<tr><td></td></tr>
		<tr>
			<td class="label">Source File Name</td>
			<td>
				<input type="hidden" name="page" value="<?php echo $_REQUEST['page']?>">
				<select name="phpfile" id="id_file_select" autofocus="autofocus" <?php echo $lHTMLControlAttributes ?>>
				<?php 
					$_SESSION['source-viewer-files-array'] = "";						
					if(!$lValidateAndTokenize){
						// Just print raw filenames as values
						foreach ($DirectoryIterator as $fileInfo) {
							$lPHPFileName = $fileInfo->getFilename();
							if ($fileInfo->GetExtension() == "php" and !$fileInfo->isDot()) {
						   		echo '<option value="' . $lPHPFileName . '">' . $lPHPFileName . "</option>";
							}// end if
						}// end for each
					}else{
						// Tokenization Defense
						$aAllowedPHPFiles = array();
						$lCounter = 0;
						foreach ($DirectoryIterator as $fileInfo) {
							$lPHPFileName = $fileInfo->getFilename();
							if ($fileInfo->GetExtension() == "php" and !$fileInfo->isDot()) {
						   		echo '<option value="' . $lCounter . '">' . $lPHPFileName . "</option>";
								$aAllowedPHPFiles[$lCounter]=$lPHPFileName;
								$lCounter += 1;							
							}// end if
						}// end for each
						$_SESSION['source-viewer-files-array'] = $aAllowedPHPFiles;
					}// end if
				?>
				</select>
			</td>
		</tr>
		<tr><td></td></tr>
		<tr>
			<td colspan="2" style="text-align:center;">
				<input name="source-file-viewer-php-submit-button" class="button" type="submit" value="View File" />
			</td>
		</tr>
		<tr><td></td></tr>
	</table>
</form>

<?php
	try {	    	
		if (isset($_POST['source-file-viewer-php-submit-button'])){

			if (!$lValidateAndTokenize) {
	   			/* This code is insecure. Direct object references in the form of the "file"
	   			 parameter give the user complete control of the input. Contrary to popular belief, 
	   			 input validation, blacklisting, etc is not the best defense. The best defenses are 
	   			 provably secure 100% of the time. For direct object references, there are two defenses.
	   			 Authorization via ACL or Entitlements is used when transaction requires authentication.
	   			 This transaction (forwarding URL) does not require authentication so the other method is used;
	   			 mapping. Mapping substitutes a harmless token for the direct object. The direct object in 
	   			 this case is the page the user is being forwarded to. We will use mapping to secure this code.
	   			 
	   			 Note: Some sites try to use validation to defend against Insecure Direct Object References.
	   			 Validation fails in many cases due to weak validators.
	   			
	   			 Note: For static links, the best defense is to simply hardcode the links in an anchor tag.
	   			 This exercise will use mapping to show how it works, but it should be recognized that 
	   			 for giving the user links to click, hardcoding is the best defense.
	   			*/
	   			
	   			/* insecure: $_REQUEST would take input from GET or POST. This can result in an HTTP Parameter Polution
	   			 * attack. If a site uses POST, then grab input from _POST. Use _GET for gets. HPP can
	   			 * occur more easily when input is ambiguous.
	   			 * 
	   			 * Also, the web is weakly typed. All data is strings. It doesnt matter what the developers
	   			 * thinks the input is (int, string, char, etc.). The fact is that HTTP is text. if the 
	   			 * "phpfile" is expected to be integer, it should be validated as such. If string, then 
	   			 * validate as string.
	   			 * 
	   			 *  Definition of validation. Perform all of:
	   			 *  
	   			 *  check data type
	   			 *  check data length
	   			 *  check character set
	   			 *  check pattern
	   			 *  check range
	   			 */

				// Grab inputs
				$pPHPFile = $_REQUEST['phpfile'];
				
				// Insecure Mode: Skip validation
				$lFilename = $pPHPFile;

				$LogHandler->writeToLog("Page source-viewer.php loaded file: " . $lFilename);

			}elseif ($lValidateAndTokenize){
	   			/* The "phpfile" is expected to be integer, so validate as such. Also,
	   			 * dont use _REQUEST as this would allow a POSTed "phpfile" to be sent 
	   			 * along with a URL query parameter "phpfile" as well. This type of sloppy
	   			 * variable fetching can result in HTTP Parameter Pollution. 
	   			 */
	   			$pPHPFile=$Encoder->encodeForHTML($_POST["phpfile"]);
	   			
	   			$laAllowedPHPFiles = $_SESSION['source-viewer-files-array'];
	   			$lArrayCount = count($laAllowedPHPFiles);
	   			
	   			if (!is_array($laAllowedPHPFiles)){
	   				throw new Exception('Validation Failed: Did not receive allowed values array.');
	   			}// end if

	   			if (!($lArrayCount > 0)){
	   				throw new Exception('Validation Failed: Array is empty.');
	   			}// end if
	   			
	   			/* We expect small int. validate positive integer between 0-9.
	   			 * Regex pattern makes sure the user doesnt send in characters that
	   			 * are not actually digits but can be cast to digits.
	   			 */	
	   			$isDigits = (preg_match("/\d{1,4}/", $pPHPFile) == 1);    			
	   			if (!($isDigits && $pPHPFile >= 0 && $pPHPFile < $lArrayCount)){
	   				throw(new Exception("Expected integer input. Cannot process request. Support team alerted."));
	   			}// end if

	   			/* Insecure Direct Object References are patched
				 * by removing the direct object reference all together.
				 * Web applications are "fronts" for services. Some web
				 * sites offer web pages, some offer XML, SOAP, or other
				 * services. In any case, the web site should not "give away"
				 * information about internal objects such as database IDs,
				 * redirection URLs, system file names, or application
				 * paths/configuration.
				 * 
				 * Offer the user harmless tokens instead of actual 
				 * objects. In this case, we use integers to map to
				 * the direct object, which is the forwarding URL.
				 */ 
				$lFilename = $laAllowedPHPFiles[$pPHPFile];

				$LogHandler->writeToLog("Page source-viewer.php loaded file: " . $lFilename);				
		   	}// end if $lValidateAndTokenize
		   	
		   	// try to display the file
		   	try {
	   			echo '<span class="label">File: '.$lFilename.'</span>';
	   			echo '<pre>';
				highlight_file($lFilename);
				echo '</pre>';
			}catch(Exception $e){
				echo $CustomErrorHandler->FormatError($e, "Error trying to print file. Cannot load file.");
			}// end try
					   	
		}// end if (isset($_POST['source-file-viewer-php-submit-button']))
	}catch(Exception $e){
		echo $CustomErrorHandler->FormatError($e, "Error in source file viewer. Cannot load file.");
	}// end try
?>