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<?php
/* For licensing terms, see /license.txt */
use Chamilo\CoreBundle\Component\HTMLPurifier\Filter\AllowIframes;
use Chamilo\CoreBundle\Component\HTMLPurifier\Filter\RemoveOnAttributes;
use ChamiloSession as Session;
/**
* This is the security library for Chamilo.
*
* This library is based on recommendations found in the PHP5 Certification
* Guide published at PHP|Architect, and other recommendations found on
* http://www.phpsec.org/
* The principles here are that all data is tainted (most scripts of Chamilo are
* open to the public or at least to a certain public that could be malicious
* under specific circumstances). We use the white list approach, whereas we
* consider that data can only be used in the database or in a file if it has
* been filtered.
*
* For session fixation, use ...
* For session hijacking, use get_ua() and check_ua()
* For Cross-Site Request Forgeries, use get_token() and check_token()
* For basic filtering, use filter()
* For files inclusions (using dynamic paths) use check_rel_path() and check_abs_path()
*
* @author Yannick Warnier <ywarnier@beeznest.org>
*/
/**
* Security class.
*
* Include/require it in your code and call Security::function()
* to use its functionalities.
*
* This class can also be used as a container for filtered data, by creating
* a new Security object and using $secure->filter($new_var,[more options])
* and then using $secure->clean['var'] as a filtered equivalent, although
* this is *not* mandatory at all.
*/
class Security
{
public const CHAR_UPPER = 'ABCDEFGHIJKLMNOPQRSTUVWXYZ';
public const CHAR_LOWER = 'abcdefghijklmnopqrstuvwxyz';
public const CHAR_DIGITS = '0123456789';
public const CHAR_SYMBOLS = '!"#$%&\'()*+,-./:;<=>?@[\]^_`{|}~';
public static $clean = [];
/**
* Checks if the absolute path (directory) given is really under the
* checker path (directory).
*
* @param string $abs_path Absolute path to be checked (with trailing slash)
* @param string $checker_path Checker path under which the path
* should be (absolute path, with trailing slash, get it from api_get_path(SYS_COURSE_PATH))
*
* @return bool True if the path is under the checker, false otherwise
*/
public static function check_abs_path(string $abs_path, string $checker_path): bool
{
// The checker path must be set.
if (empty($checker_path)) {
return false;
}
// Clean $abs_path.
$true_path = self::cleanPath($abs_path);
$checker_path = str_replace("\\", '/', realpath($checker_path));
if (empty($checker_path)) {
return false;
}
$found = strpos($true_path.'/', $checker_path);
if ($found === 0) {
return true;
} else {
// Code specific to Windows and case-insensitive behaviour
if (api_is_windows_os()) {
$found = stripos($true_path.'/', $checker_path);
if ($found === 0) {
return true;
}
}
}
return false;
}
public static function cleanPath(string $absPath): string
{
$absPath = str_replace(['//', '../'], ['/', ''], $absPath);
return str_replace("\\", '/', realpath($absPath));
}
/**
* Checks if the relative path (directory) given is really under the
* checker path (directory).
*
* @param string $rel_path Relative path to be checked (relative to the current directory) (with trailing slash)
* @param string $checker_path Checker path under which the path
* should be (absolute path, with trailing slash, get it from api_get_path(SYS_COURSE_PATH))
*
* @return bool True if the path is under the checker, false otherwise
*/
public static function check_rel_path(string $rel_path, string $checker_path): bool
{
// The checker path must be set.
if (empty($checker_path)) {
return false;
}
$current_path = getcwd(); // No trailing slash.
if (substr($rel_path, -1, 1) != '/') {
$rel_path = '/'.$rel_path;
}
$abs_path = $current_path.$rel_path;
$true_path = str_replace("\\", '/', realpath($abs_path));
$found = strpos($true_path.'/', $checker_path);
if ($found === 0) {
return true;
}
return false;
}
/**
* Filters dangerous filenames (*.php[.]?* and .htaccess) and returns it in
* a non-executable form (for PHP and htaccess, this is still vulnerable to
* other languages' files extensions).
*
* @param string $filename Unfiltered filename
*/
public static function filter_filename(string $filename): string
{
return disable_dangerous_file($filename);
}
public static function getTokenFromSession(string $prefix = '')
{
$secTokenVariable = self::generateSecTokenVariable($prefix);
return Session::read($secTokenVariable);
}
/**
* This function checks that the token generated in get_token() has been kept (prevents
* Cross-Site Request Forgeries attacks).
*
* @param string $requestType The array in which to get the token ('get' or 'post')
* @param ?FormValidator $form
*
* @return bool True if it's the right token, false otherwise
*/
public static function check_token(string $requestType = 'post', FormValidator $form = null, string $prefix = ''): bool
{
$secTokenVariable = self::generateSecTokenVariable($prefix);
$sessionToken = Session::read($secTokenVariable);
switch ($requestType) {
case 'request':
if (!empty($sessionToken) && isset($_REQUEST[$secTokenVariable]) && $sessionToken === $_REQUEST[$secTokenVariable]) {
return true;
}
return false;
case 'get':
if (!empty($sessionToken) && isset($_GET[$secTokenVariable]) && $sessionToken === $_GET[$secTokenVariable]) {
return true;
}
return false;
case 'post':
if (!empty($sessionToken) && isset($_POST[$secTokenVariable]) && $sessionToken === $_POST[$secTokenVariable]) {
return true;
}
return false;
case 'form':
$token = $form->getSubmitValue('protect_token');
if (!empty($sessionToken) && !empty($token) && $sessionToken === $token) {
return true;
}
return false;
default:
if (!empty($sessionToken) && isset($requestType) && $sessionToken === $requestType) {
return true;
}
}
return false; // Just in case, don't let anything slip.
}
/**
* Checks the user agent of the client as recorder by get_ua() to prevent
* most session hijacking attacks.
*
* @return bool True if the user agent is the same, false otherwise
*/
public static function check_ua(): bool
{
$security = Session::read('sec_ua');
$securitySeed = Session::read('sec_ua_seed');
if ($security === $_SERVER['HTTP_USER_AGENT'].$securitySeed) {
return true;
}
return false;
}
/**
* Clear the security token from the session.
*/
public static function clear_token(string $prefix = '')
{
$secTokenVariable = self::generateSecTokenVariable($prefix);
Session::erase($secTokenVariable);
}
/**
* This function sets a random token to be included in a form as a hidden field
* and saves it into the user's session. Returns an HTML form element
* This later prevents Cross-Site Request Forgeries by checking that the user is really
* the one that sent this form in knowingly (this form hasn't been generated from
* another website visited by the user at the same time).
* Check the token with check_token().
*
* @return string Hidden-type input ready to insert into a form
*/
public static function get_HTML_token(string $prefix = ''): string
{
$secTokenVariable = self::generateSecTokenVariable($prefix);
$token = md5(uniqid(rand(), true));
$string = '<input type="hidden" name="'.$secTokenVariable.'" value="'.$token.'" />';
Session::write($secTokenVariable, $token);
return $string;
}
/**
* This function sets a random token to be included in a form as a hidden field
* and saves it into the user's session.
* This later prevents Cross-Site Request Forgeries by checking that the user is really
* the one that sent this form in knowingly (this form hasn't been generated from
* another website visited by the user at the same time).
* Check the token with check_token().
*
* @return string Token
*/
public static function get_token($prefix = ''): string
{
$secTokenVariable = self::generateSecTokenVariable($prefix);
$token = md5(uniqid(rand(), true));
Session::write($secTokenVariable, $token);
return $token;
}
public static function get_existing_token(string $prefix = ''): string
{
$secTokenVariable = self::generateSecTokenVariable($prefix);
$token = Session::read($secTokenVariable);
if (!empty($token)) {
return $token;
} else {
return self::get_token($prefix);
}
}
/**
* Gets the user agent in the session to later check it with check_ua() to prevent
* most cases of session hijacking.
*/
public static function get_ua()
{
$seed = uniqid(rand(), true);
Session::write('sec_ua_seed', $seed);
Session::write('sec_ua', $_SERVER['HTTP_USER_AGENT'].$seed);
}
/**
* This function returns a variable from the clean array. If the variable doesn't exist,
* it returns null.
*
* @param string $varname Variable name
*
* @return mixed Variable or NULL on error
*/
public static function get(string $varname)
{
if (isset(self::$clean[$varname])) {
return self::$clean[$varname];
}
return null;
}
/**
* This function tackles the XSS injections.
* Filtering for XSS is very easily done by using the htmlentities() function.
* This kind of filtering prevents JavaScript snippets to be understood as such.
*
* @param string|array $var The variable to filter for XSS, this params can be a string or an array (example : array(x,y))
* @param ?int $user_status The user status,constant allowed (STUDENT, COURSEMANAGER, ANONYMOUS, COURSEMANAGERLOWSECURITY)
*
* @return mixed Filtered string or array
*/
public static function remove_XSS($var, int $user_status = null, bool $filter_terms = false)
{
if ($filter_terms) {
$var = self::filter_terms($var);
}
if (empty($user_status)) {
if (api_is_anonymous()) {
$user_status = ANONYMOUS;
} else {
if (api_is_allowed_to_edit()) {
$user_status = COURSEMANAGER;
} else {
$user_status = STUDENT;
}
}
}
if ($user_status == COURSEMANAGERLOWSECURITY) {
return $var; // No filtering.
}
static $purifier = [];
if (!isset($purifier[$user_status])) {
$cache_dir = api_get_path(SYS_ARCHIVE_PATH).'Serializer';
if (!file_exists($cache_dir)) {
$mode = api_get_permissions_for_new_directories();
mkdir($cache_dir, $mode);
}
$config = HTMLPurifier_Config::createDefault();
$config->set('Cache.SerializerPath', $cache_dir);
$config->set('Core.Encoding', api_get_system_encoding());
$config->set('HTML.Doctype', 'XHTML 1.0 Transitional');
$config->set('HTML.MaxImgLength', '2560');
$config->set('HTML.TidyLevel', 'light');
$config->set('Core.ConvertDocumentToFragment', false);
$config->set('Core.RemoveProcessingInstructions', true);
$customFilters = [
new RemoveOnAttributes(),
];
if (api_get_setting('enable_iframe_inclusion') == 'true') {
$customFilters[] = new AllowIframes();
}
if ($customFilters) {
$config->set('Filter.Custom', $customFilters);
}
// Shows _target attribute in anchors
$config->set('Attr.AllowedFrameTargets', ['_blank', '_top', '_self', '_parent']);
if ($user_status == STUDENT) {
global $allowed_html_student;
$config->set('HTML.SafeEmbed', true);
$config->set('HTML.SafeObject', true);
$config->set('Filter.YouTube', true);
$config->set('HTML.FlashAllowFullScreen', true);
$config->set('HTML.Allowed', $allowed_html_student);
} elseif ($user_status == COURSEMANAGER) {
global $allowed_html_teacher;
$config->set('HTML.SafeEmbed', true);
$config->set('HTML.SafeObject', true);
$config->set('Filter.YouTube', true);
$config->set('HTML.FlashAllowFullScreen', true);
$config->set('HTML.Allowed', $allowed_html_teacher);
} else {
global $allowed_html_anonymous;
$config->set('HTML.Allowed', $allowed_html_anonymous);
}
// We need it for example for the flv player (ids of surrounding div-tags have to be preserved).
$config->set('Attr.EnableID', true);
$config->set('CSS.AllowImportant', true);
// We need for the flv player the css definition display: none;
$config->set('CSS.AllowTricky', true);
$config->set('CSS.Proprietary', true);
// Allow uri scheme.
$config->set('URI.AllowedSchemes', [
'http' => true,
'https' => true,
'mailto' => true,
'ftp' => true,
'nntp' => true,
'news' => true,
'data' => true,
]);
// Allow <video> tag
//$config->set('HTML.Doctype', 'HTML 4.01 Transitional');
$config->set('HTML.SafeIframe', true);
// Set some HTML5 properties
$config->set('HTML.DefinitionID', 'html5-definitions'); // unqiue id
$config->set('HTML.DefinitionRev', 1);
if ($def = $config->maybeGetRawHTMLDefinition()) {
// https://html.spec.whatwg.org/dev/media.html#the-video-element
$def->addElement(
'video',
'Block',
'Optional: (source, Flow) | (Flow, source) | Flow',
'Common',
[
'src' => 'URI',
'type' => 'Text',
'width' => 'Length',
'height' => 'Length',
'poster' => 'URI',
'preload' => 'Enum#auto,metadata,none',
'controls' => 'Bool',
]
);
// https://html.spec.whatwg.org/dev/media.html#the-audio-element
$def->addElement(
'audio',
'Block',
'Optional: (source, Flow) | (Flow, source) | Flow',
'Common',
[
'autoplay' => 'Bool',
'src' => 'URI',
'loop' => 'Bool',
'preload' => 'Enum#auto,metadata,none',
'controls' => 'Bool',
'muted' => 'Bool',
]
);
$def->addElement(
'source',
'Block',
'Flow',
'Common',
['src' => 'URI', 'type' => 'Text']
);
}
$purifier[$user_status] = new HTMLPurifier($config);
}
if (is_array($var)) {
return $purifier[$user_status]->purifyArray($var);
} else {
return $purifier[$user_status]->purify($var);
}
}
/**
* Filter content.
*
* @param string $text to be filtered
*/
public static function filter_terms(string $text): string
{
static $bad_terms = [];
if (empty($bad_terms)) {
$list = api_get_setting('filter_terms');
if (!empty($list)) {
$list = explode("\n", $list);
$list = array_filter($list);
if (!empty($list)) {
foreach ($list as $term) {
$term = str_replace(["\r\n", "\r", "\n", "\t"], '', $term);
$html_entities_value = api_htmlentities($term, ENT_QUOTES, api_get_system_encoding());
$bad_terms[] = $term;
if ($term != $html_entities_value) {
$bad_terms[] = $html_entities_value;
}
}
}
$bad_terms = array_filter($bad_terms);
}
}
$replace = '***';
if (!empty($bad_terms)) {
// Fast way
$new_text = str_ireplace($bad_terms, $replace, $text);
$text = $new_text;
}
return $text;
}
/**
* This method provides specific protection (against XSS and other kinds of attacks)
* for static images (icons) used by the system.
* Image paths are supposed to be given by programmers - people who know what they do, anyway,
* this method encourages a safe practice for generating icon paths, without using heavy solutions
* based on HTMLPurifier for example.
*
* @param string $image_path the input path of the image, it could be relative or absolute URL
*
* @return string returns sanitized image path or an empty string when the image path is not secure
*
* @author Ivan Tcholakov, March 2011
*/
public static function filter_img_path(string $image_path): string
{
static $allowed_extensions = ['png', 'gif', 'jpg', 'jpeg', 'svg', 'webp'];
$image_path = htmlspecialchars(trim($image_path)); // No html code is allowed.
// We allow static images only, query strings are forbidden.
if (strpos($image_path, '?') !== false) {
return '';
}
if (($pos = strpos($image_path, ':')) !== false) {
// Protocol has been specified, let's check it.
if (stripos($image_path, 'javascript:') !== false) {
// Javascript everywhere in the path is not allowed.
return '';
}
// We allow only http: and https: protocols for now.
//if (!preg_match('/^https?:\/\//i', $image_path)) {
// return '';
//}
if (stripos($image_path, 'http://') !== 0 && stripos($image_path, 'https://') !== 0) {
return '';
}
}
// We allow file extensions for images only.
//if (!preg_match('/.+\.(png|gif|jpg|jpeg)$/i', $image_path)) {
// return '';
//}
if (($pos = strrpos($image_path, '.')) !== false) {
if (!in_array(strtolower(substr($image_path, $pos + 1)), $allowed_extensions)) {
return '';
}
} else {
return '';
}
return $image_path;
}
/**
* Get password requirements
* It checks config value 'password_requirements' or uses the "classic"
* Chamilo password requirements.
*/
public static function getPasswordRequirements(): array
{
// Default
$requirements = [
'min' => [
'lowercase' => 0,
'uppercase' => 0,
'numeric' => 2,
'length' => 5,
'specials' => 1,
],
];
$passwordRequirements = api_get_configuration_value('password_requirements');
if (!empty($passwordRequirements)) {
$requirements = $passwordRequirements;
}
return ['min' => $requirements['min']];
}
/**
* Gets password requirements in the platform language using get_lang
* based in platform settings. See function 'self::getPasswordRequirements'.
*/
public static function getPasswordRequirementsToString(array $evaluatedConditions = []): string
{
$output = '';
$setting = self::getPasswordRequirements();
$passedIcon = Display::returnFontAwesomeIcon(
'check',
'',
true,
'text-success',
get_lang('PasswordRequirementPassed')
);
$pendingIcon = Display::returnFontAwesomeIcon(
'times',
'',
true,
'text-danger',
get_lang('PasswordRequirementPending')
);
foreach ($setting as $type => $rules) {
foreach ($rules as $rule => $parameter) {
if (empty($parameter)) {
continue;
}
$evaluatedCondition = $type.'_'.$rule;
$icon = $passedIcon;
if (array_key_exists($evaluatedCondition, $evaluatedConditions)
&& false === $evaluatedConditions[$evaluatedCondition]
) {
$icon = $pendingIcon;
}
$output .= empty($evaluatedConditions) ? '' : $icon;
$output .= sprintf(
get_lang(
'NewPasswordRequirement'.ucfirst($type).'X'.ucfirst($rule)
),
$parameter
);
$output .= '<br />';
}
}
return $output;
}
/**
* Sanitize a string, so it can be used in the exec() command without
* "jail-breaking" to execute other commands.
*
* @param string $param The string to filter
*/
public static function sanitizeExecParam(string $param): string
{
$param = preg_replace('/[`;&|]/', '', $param);
return escapeshellarg($param);
}
private static function generateSecTokenVariable(string $prefix = ''): string
{
if (empty($prefix)) {
return 'sec_token';
}
return $prefix.'_sec_token';
}
}
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