利用PHP编程防范XSS跨站脚本攻击_PHP教程

＜?php$str = "A 'quote' is ＜b＞bold＜/b＞";// Outputs: A 'quote' is boldecho htmlentities($str);// Outputs: A 'quote' is boldecho 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 ＜javascript＞ 　// note that you have to handle splits with n, r, and t later sincethey *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; } 　} } }