340 lines
11 KiB
PHP
340 lines
11 KiB
PHP
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<?php
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/*
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Does emit a CAPTCHA graphic and form fields, which allows to tell real
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people from bots.
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Though a textual description is generated as well, this sort of access
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restriction will knock out visually impaired users, and frustrate all
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others anyhow. Therefore this should only be used as last resort for
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defending against spambots. Because of the readable text and the used
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colorspaces this is a weak implementation, not completely OCR-secure.
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captcha::form() will return a html string to be inserted into textarea/
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[save] <forms> and alike. User input is veryfied with captcha::check().
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You should leave the sample COLLEGE.ttf next to this script, else you
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have to define the _FONT_DIR constant correctly. Use only 1 font type.
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Creates temporary files, which however get purged automatically after
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four hours.
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Public Domain, available via http://freshmeat.net/p/captchaphp
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*/
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#-- config
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define("EWIKI_FONT_DIR", dirname(__FILE__)); // which fonts to use
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define("CAPTCHA_INVERSE", 0); // white or black(=1)
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define("CAPTCHA_TIMEOUT", 5000); // in seconds (=max 4 hours)
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define("CAPTCHA_MAXSIZE", 4500); // preferred image size
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define("CAPTCHA_COOKIE", "captcha_solved"); // to unlock captcha protection
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define("CAPTCHA_DATA_URLS", 0); // RFC2397-URLs exclude MSIE users
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define("CAPTCHA_TEMP_DIR", "/tmp/captcha");
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define("CAPTCHA_BASE_URL", "http://$_SERVER[SERVER_NAME]:$_SERVER[SERVER_PORT]/" . substr(realpath(__FILE__), strlen($_SERVER["DOCUMENT_ROOT"])));
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/* static - (you could instantiate it, but...) */
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class captcha {
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/* gets parameter from $_REQUEST[] array (POST vars) and so can
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verify input, @returns boolean
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*/
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function check() {
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$to = (int)(time()/1000000);
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if ($_COOKIE[CAPTCHA_COOKIE] == $to) {
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return(true);
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}
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if (($hash = $_REQUEST["captcha_hash"])
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and ($pw = trim($_REQUEST["captcha_input"]))) {
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$r = (captcha::hash($pw)==$hash) || (captcha::hash($pw,-1)==$hash);
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if ($r) {
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setcookie(CAPTCHA_COOKIE, $to, time()+1000000);
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}
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return($r);
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}
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}
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/* yields <input> fields html string (no complete form), with captcha
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image already embedded as data:-URI
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*/
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function form($title="→ retype that here", $more="<small>Enter the correct letters and numbers from the image into the text box. This small test serves as access restriction against malicious bots. Simply reload the page if this graphic is too hard to read.</small>") {
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#-- stop if user already verified
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if ($_COOKIE[CAPTCHA_COOKIE] == (int)(time()/1000000)) {
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return "";
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}
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#-- prepare image text
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$pw = captcha::mkpass();
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$hash = captcha::hash($pw);
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$alt = htmlentities(captcha::textual_riddle($pw));
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#-- image
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$img = captcha::image($pw, 200, 60, CAPTCHA_INVERSE, CAPTCHA_MAXSIZE);
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if (CAPTCHA_DATA_URLS && !strpos("MSIE", $_SERVER["HTTP_USER_AGENT"])) {
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$img_fn = "data:image/jpeg;base64," . base64_encode($img);
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}
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else {
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$img_fn = CAPTCHA_BASE_URL . "?_tcf=" . captcha::store_image($img);
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}
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#-- emit html form
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$html =
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'<table border="0" summary="captcha input"><tr>'
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. '<td><img name="captcha_image" id="captcha_image" src="' .$img_fn. '" height="60" width="200" alt="'.$alt. '" /></td>'
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. '<td>'.$title. '<br/><input name="captcha_hash" type="hidden" value="'.$hash. '" />'
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. '<input name="captcha_input" type="text" size="7" maxlength="16" style="height:46px; font-size:34px; font-weight:450;" />'
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. '</td><td>'.$more.'</td>'
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. '</tr></table>';
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$html = "<div class=\"captcha\">$html</div>";
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return($html);
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}
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/* generates alternative (non-graphic), human-understandable
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representation of the passphrase
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*/
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function textual_riddle($phrase) {
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$symbols0 = '"\'-/_:';
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$symbols1 = array("\n,", "\n;", ";", "\n&", "\n-", ",", ",", "\nand then", "\nfollowed by", "\nand", "\nand not a\n\"".chr(65+rand(0,26))."\",\nbut");
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$s = "Guess the letters and numbers\n(passphrase riddle)\n--\n";
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for ($p=0; $p<strlen($phrase); $p++) {
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$c = $phrase[$p];
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$add = "";
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#-- asis
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if (!rand(0,3)) {
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$i = $symbols0[rand(0,strlen($symbols0)-1)];
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$add = "$i$c$i";
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}
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#-- letter
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elseif ($c >= 'A') {
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$type = ($c >= 'a' ? "small " : "");
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do {
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$n = rand(-3,3);
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$c2 = chr((ord($c) & 0x5F) + $n);
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}
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while (($c2 < 'A') || ($c2 > 'Z'));
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if ($n < 0) {
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$n = -$n;
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$add .= "$type'$c2' +$n letters";
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}
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else {
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$add .= "$n chars before $type$c2";
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}
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}
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#-- number
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else {
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$add = "???";
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$n = (int) $c;
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do {
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do { $x = rand(1, 10); } while (!$x);
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$op = rand(0,11);
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if ($op <= 2) {
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$add = "($add * $x)"; $n *= $x;
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}
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elseif ($op == 3) {
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$x = 2 * rand(1,2);
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$add = "($add / $x)"; $n /= $x;
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}
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elseif ($sel % 2) {
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$add = "($add + $x)"; $n += $x;
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}
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else {
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$add = "($add - $x)"; $n -= $x;
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}
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}
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while (rand(0,1));
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$add .= " = $n";
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}
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$s .= "$add";
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$s .= $symbols1[rand(0,count($symbols1)-1)] . "\n";
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}
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return($s);
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}
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/* returns jpeg file stream with unscannable letters encoded
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in front of colorful disturbing background
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*/
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function image($phrase, $width=200, $height=60, $inverse=0, $maxsize=0xFFFFF) {
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#-- initialize in-memory image with gd library
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srand(microtime()*21017);
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$img = imagecreatetruecolor($width, $height);
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$R = $inverse ? 0xFF : 0x00;
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imagefilledrectangle($img, 0,0, $width,$height, captcha::random_color($img, 222^$R, 255^$R));
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$c1 = rand(150^$R, 185^$R);
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$c2 = rand(195^$R, 230^$R);
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#-- configuration
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$fonts = array(
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// "COLLEGE.ttf",
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);
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$fonts += glob(EWIKI_FONT_DIR."/*.ttf");
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#-- encolour bg
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$wd = 20;
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$x = 0;
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while ($x < $width) {
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imagefilledrectangle($img, $x, 0, $x+=$wd, $height, captcha::random_color($img, 222^$R, 255^$R));
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$wd += max(10, rand(0, 20) - 10);
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}
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#-- make interesting background I, lines
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$wd = 4;
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$w1 = 0;
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$w2 = 0;
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for ($x=0; $x<$width; $x+=(int)$wd) {
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if ($x < $width) { // verical
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imageline($img, $x+$w1, 0, $x+$w2, $height-1, captcha::random_color($img,$c1,$c2));
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}
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if ($x < $height) { // horizontally ("y")
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imageline($img, 0, $x-$w2, $width-1, $x-$w1, captcha::random_color($img,$c1,$c2));
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}
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$wd += rand(0,8) - 4;
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if ($wd < 1) { $wd = 2; }
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$w1 += rand(0,8) - 4;
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$w2 += rand(0,8) - 4;
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if (($x > $height) && ($y > $height)) {
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break;
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}
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}
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#-- more disturbing II, random letters
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$limit = rand(30,90);
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for ($n=0; $n<$limit; $n++) {
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$letter = "";
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do {
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$letter .= chr(rand(31,125)); // random symbol
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} while (rand(0,1));
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$size = rand(5, $height/2);
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$half = (int) ($size / 2);
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$x = rand(-$half, $width+$half);
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$y = rand(+$half, $height);
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$rotation = rand(60, 300);
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$c1 = captcha::random_color($img, 130^$R, 240^$R);
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$font = $fonts[rand(0, count($fonts)-1)];
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imagettftext($img, $size, $rotation, $x, $y, $c1, $font, $letter);
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}
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#-- add the real text to it
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$len = strlen($phrase);
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$w1 = 10;
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$w2 = $width / ($len+1);
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for ($p=0; $p<$len; $p++) {
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$letter = $phrase[$p];
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$size = rand(18, $height/2.2);
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$half = (int) $size / 2;
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$rotation = rand(-33, 33);
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$y = rand($size+3, $height-3);
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$x = $w1 + $w2*$p;
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$w1 += rand(-$width/90, $width/40); // @BUG: last char could be +30 pixel outside of image
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$font = $fonts[rand(0, count($fonts)-1)];
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$r=rand(30,99); $g=rand(30,99); $b=rand(30,99); // two colors for shadow
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$c1 = imagecolorallocate($img, $r*1^$R, $g*1^$R, $b*1^$R);
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$c2 = imagecolorallocate($img, $r*2^$R, $g*2^$R, $b*2^$R);
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imagettftext($img, $size, $rotation, $x+1, $y, $c2, $font, $letter);
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imagettftext($img, $size, $rotation, $x, $y-1, $c1, $font, $letter);
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}
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#-- let JFIF stream be generated
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$quality = 67;
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$s = array();
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do {
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ob_start(); ob_implicit_flush(0);
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imagejpeg($img, "", (int)$quality);
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$jpeg = ob_get_contents(); ob_end_clean();
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$size = strlen($jpeg);
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$s_debug[] = ((int)($quality*10)/10) . "%=$size";
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$quality = $quality * ($maxsize/$size) * 0.93 - 1.7; // -($quality/7.222)*
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}
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while (($size > $maxsize) && ($quality >= 16));
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imagedestroy($img);
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#print_r($s_debug);
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return($jpeg);
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}
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/* helper code */
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function random_color($img, $a,$b) {
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return imagecolorallocate($img, rand($a,$b), rand($a,$b), rand($a,$b));
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}
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/* creates temporary file, returns basename */
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function store_image($data) {
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$dir = CAPTCHA_TEMP_DIR;
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$id = md5($data);
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#-- create temp dir
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if (!file_exists($dir)) {
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mkdir($dir) && chmod($dir, 0777);
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}
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#-- remove stale files
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if ($dh = opendir($dir)) {
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$t_kill = time() - CAPTCHA_TIMEOUT;
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while($fn = readdir($dh)) if ($fn[0] != ".") {
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if (filemtime("$dir/$fn") < $t_kill) {
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unlink("$dir/$fn");
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}
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}
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}
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#-- store file
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fwrite($f = fopen("$dir/$id", "wb"), $data) && fclose($f);
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return($id);
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}
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/* sends it */
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function get_image($id) {
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$dir = CAPTCHA_TEMP_DIR;
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$fn = "$dir/$id";
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#-- find it
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if (preg_match('/^\w+$/', $id) && file_exists($fn)) {
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header("Content-Type: image/jpeg");
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header("Content-Length: " . filesize($fn));
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header("Last-Modified: " . gmstrftime("%a, %d %b %G %T %Z", filemtime($fn)));
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if (isset($_SERVER["HTTP_IF_MODIFIED_SINCE"])) {
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header("Status: 304 Unmodified");
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}
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else {
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readfile($fn);
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}
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exit;
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}
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}
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/* unreversable hash from passphrase, with time() slice encoded */
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function hash($text, $dtime=0) {
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$text = strtolower($text);
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$pfix = (int) (time() / CAPTCHA_TIMEOUT) + $dtime;
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return md5("captcha::$pfix:$text::".__FILE__.":$_SERVER[SERVER_NAME]:80");
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}
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/* makes string of random letters for embedding into image and for
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encoding as hash, later verification
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*/
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function mkpass() {
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$s = "";
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for ($n=0; $n<10; $n++) {
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$s .= chr(rand(0, 255));
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}
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$s = base64_encode($s); // base64-set, but filter out unwanted chars
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$s = preg_replace("/[+\/=IG0ODQR]/i", "", $s); // (depends on YOUR font)
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$s = substr($s, 0, rand(5,7));
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return($s);
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}
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}
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#-- IE workaround
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if (isset($_REQUEST["_tcf"])) {
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captcha::get_image($_REQUEST["_tcf"]);
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}
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?>
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