| ＜?php $str = "A 'quote' is ＜b＞bold＜/b＞"; // Outputs: A 'quote' is <b>bold</b> echo htmlentities($str); // Outputs: A 'quote' is <b>bold</b> echo htmlentities($str, ENT_QUOTES); ?＞ |
| function RemoveXSS($val) { // remove all non-printable characters. CR(0a) and LF(0b) and TAB(9) are allowed // this prevents some character re-spacing such as ＜java/0script＞ // note that you have to handle splits with /n, /r, and /t later since they *are* allowed in some inputs $val = preg_replace('/([/x00-/x08][/x0b-/x0c][/x0e-/x20])/', '', $val); // straight replacements, the user should never need these since they're normal characters // this prevents like ＜IMG SRC=@avascript:a& _#X6Cert('XSS')＞ $search = 'abcdefghijklmnopqrstuvwxyz'; $search .= 'ABCDEFGHIJKLMNOPQRSTUVWXYZ'; $search .= '1234567890!@#$%^&*()'; $search .= '~`";:? /={}[]-_|/'//'; for ($i = 0; $i ＜ strlen($search); $i ) { // ;? matches the ;, which is optional // 0{0,7} matches any padded zeros, which are optional and go up to 8 chars // @ @ search for the hex values $val = preg_replace('/(&#[x|X]0{0,8}'.dechex(ord($search[$i])).';?)/i', $search[$i], $val); // with a ; // @ @ 0{0,7} matches '0' zero to seven times $val = preg_replace('/(�{0,8}'.ord($search[$i]).';?)/', $search[$i], $val); // with a ; } // now the only remaining whitespace attacks are /t, /n, and /r $ra1 = Array('javascript', 'vbscript', 'expression', 'applet', 'meta', 'xml', 'blink', 'link', 'style', 'script', 'embed', 'object', 'iframe', 'frame', 'frameset', 'ilayer', 'layer', 'bgsound', 'title', 'base'); $ra2 = Array('onabort', 'onactivate', 'onafterprint', 'onafterupdate', 'onbeforeactivate', 'onbeforecopy', 'onbeforecut', 'onbeforedeactivate', 'onbeforeeditfocus', 'onbeforepaste', 'onbeforeprint', 'onbeforeunload', 'onbeforeupdate', 'onblur', 'onbounce', 'oncellchange', 'onchange', 'onclick', 'oncontextmenu', 'oncontrolselect', 'oncopy', 'oncut', 'ondataavailable', 'ondatasetchanged', 'ondatasetcomplete', 'ondblclick', 'ondeactivate', 'ondrag', 'ondragend', 'ondragenter', 'ondragleave', 'ondragover', 'ondragstart', 'ondrop', 'onerror', 'onerrorupdate', 'onfilterchange', 'onfinish', 'onfocus', 'onfocusin', 'onfocusout', 'onhelp', 'onkeydown', 'onkeypress', 'onkeyup', 'onlayoutcomplete', 'onload', 'onlosecapture', 'onmousedown', 'onmouseenter', 'onmouseleave', 'onmousemove', 'onmouseout', 'onmouseover', 'onmouseup', 'onmousewheel', 'onmove', 'onmoveend', 'onmovestart', 'onpaste', 'onpropertychange', 'onreadystatechange', 'onreset', 'onresize', 'onresizeend', 'onresizestart', 'onrowenter', 'onrowexit', 'onrowsdelete', 'onrowsinserted', 'onscroll', 'onselect', 'onselectionchange', 'onselectstart', 'onstart', 'onstop', 'onsubmit', 'onunload'); $ra = array_merge($ra1, $ra2); $found = true; // keep replacing as long as the previous round replaced something while ($found == true) { $val_before = $val; for ($i = 0; $i ＜ sizeof($ra); $i ) { $pattern = '/'; for ($j = 0; $j ＜ strlen($ra[$i]); $j ) { if ($j ＞ 0) { $pattern .= '('; $pattern .= '(&#[x|X]0{0,8}([9][a][b]);?)?'; $pattern .= '|(�{0,8}([9][10][13]);?)?'; $pattern .= ')?'; } $pattern .= $ra[$i][$j]; } $pattern .= '/i'; $replacement = substr($ra[$i], 0, 2).'＜x＞'.substr($ra[$i], 2); // add in ＜＞ to nerf the tag $val = preg_replace($pattern, $replacement, $val); // filter out the hex tags if ($val_before == $val) { // no replacements were made, so exit the loop $found = false; } } } } |
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