type: intercept category: antispam priority: optional This library provides a CAPTCHA for safeguarding form submissions from spam bots and alike. It is easy to hook into existing web sites and scripts. And it comes with "smart" defaults, and some user-friendliness built in. While the operation logic and identifier processing are extremley safe, this is a "weak" implementation. Specifically targetted and tweaked OCR software could overcome the visual riddle. And if enabled, the textual or mathematical riddles are rather simple to overcome, if attacked. Generic spambots are however blocked already with the default settings. PRINT captcha::form() emits the img and input fields for inclusion into your submit
IF (captcha::solved()) tests for a correctly entered solution on submit, returns true if ok Temporary files are created for tracking, verification and basic data storage, but will get automatically removed once a CAPTCHA was solved to prevent replay attacks. Additionally this library has "AJAX" super powers to enhance user interaction. And a short-lasting session cookie is also added site-wide, so users may only have to solve the captcha once (can be disabled, because that's also just security by obscurity). This code is Public Domain. */ // @define("CAPTCHA_BASE_URL", "http://$_SERVER[SERVER_NAME]:$_SERVER[SERVER_PORT]" . dirname($_SERVER['SCRIPT_NAME']) . '/captcha.php'); // @define("C_TRIGGER_URL", (strtok('http://'.$_SERVER['SERVER_NAME'].':'.$_SERVER['SERVER_PORT'].$_SERVER['REQUEST_URI'], '?'))); /* Mike O'Connell The definition of CAPTCHA_BASE_URL was incorrect, as well as the test to see if the script was being called directly. Here is what worked for me. The Request URI and script name is the URL path rather than the actual server side directory you were using before ($_SERVER['DOCUMENT_ROOT']). */ #-- behaviour @define("CAPTCHA_PERSISTENT", 1); // cookie-pass after it's solved once (does not work if headers were already sent on innovocation of captcha::solved() check) @define("CAPTCHA_NEW_URLS", 0); // force captcha only when URLs submitted @define("CAPTCHA_AJAX", 1); // visual feedback while entering letters @define("CAPTCHA_LOG", 0); // create /tmp/captcha/log file @define("CAPTCHA_NOTEXT", 0); // disables the accessible text/math riddle #-- look @define("CAPTCHA_IMAGE_TYPE", 1); // 1=wave, 2=whirly @define("CAPTCHA_INVERSE", 0); // white(=0) or black(=1) @define("CAPTCHA_IMAGE_SIZE", "200x60"); // randomly adapted a little @define("CAPTCHA_INPUT_STYLE", "height:46px; font-size:34px; font-weight:500;"); @define("CAPTCHA_PIXEL", 1); // set to 2 for smoother 2x2 grayscale pixel transform @define("CAPTCHA_ONCLICK_HIRES", 1); // use better/slower drawing mode on reloading #-- solving @define("CAPTCHA_FUZZY", 0.65); // easier solving: accept 1 or 2 misguessed letters @define("CAPTCHA_TRIES", 5); // maximum failures for solving the captcha @define("CAPTCHA_AJAX_TRIES", 25); // AJAX testing limit (prevents brute-force cracking via check API) @define("CAPTCHA_MAXPASSES", 2); // 2 passes prevent user annoyment with caching/reload failures @define("CAPTCHA_TIMEOUT", 5000); // (in seconds/2) = 3:00 hours to solve a displayed captcha @define("CAPTCHA_MIN_CHARS", 5); // how many letters to use @define("CAPTCHA_MAX_CHARS", 7); #-- operation @define("CAPTCHA_TEMP_DIR", easy_captcha_utility::tmp() . "/captcha/"); // storage directory for captcha handles @define("CAPTCHA_PARAM_ID", "__ec_i"); @define("CAPTCHA_PARAM_INPUT", "__ec_s"); @define("CAPTCHA_BGCOLOR", 0xFFFFFF); // initial background color (non-inverse, white) @define("CAPTCHA_SALT", ",e?c:7<"); #define("CAPTCHA_DATA_URLS", 0); // RFC2397-URLs exclude MSIE users @define("CAPTCHA_FONT_DIR", dirname(__FILE__)); @define("CAPTCHA_BASE_URL", (empty($_SERVER['HTTPS'])? "http": "https") . "://$_SERVER[SERVER_NAME]:$_SERVER[SERVER_PORT]/" . substr(realpath(__FILE__), strlen(realpath($_SERVER["DOCUMENT_ROOT"])))); #-- texts @define("CAPTCHA_PROMPT_TEXT", 'please enter the letters you recognize in the CAPTCHA image to the left'); @define("CAPTCHA_WHATIS_TEXT", 'What is %s = '); @define("CAPTCHA_REDRAW_TEXT", 'click on image to redraw'); /* simple API */ class captcha { #-- tests submitted CAPTCHA solution against tracking data function solved() { $c = new easy_captcha(); return $c->solved(); } function check() { return captcha::solved(); } #-- returns string with " and " fields for display in your function form($text="") { $c = new easy_captcha(); return $c->form("$text"); } } #-- init (triggered if *this* script is called directly) if ((basename($_SERVER["SCRIPT_FILENAME"]) == basename(__FILE__)) or (easy_captcha_utility::canonical_path("http://ignored.xxx/$_SERVER[REQUEST_URI]") == easy_captcha_utility::canonical_path(CAPTCHA_BASE_URL))) { easy_captcha_utility::API(); } /* base logic and data storare */ class easy_captcha { #-- init data function easy_captcha($id=NULL, $ignore_expiration=0) { #-- load if (($this->id = $id) or ($this->id = preg_replace("/[^-,.\w]+/", "", @$_REQUEST[CAPTCHA_PARAM_ID]))) { $this->load(); } #-- create new if (empty($this->id) || !$ignore_expiration && !$this->is_valid() && $this->log("new()", "EXPIRED", "regenerating store")) { $this->generate(); } } #-- create solutions function generate() { #-- init srand(microtime() + time()/2 - 21017); if ($this->id) { $this->prev[] = $this->id; } $this->id = $this->new_id(); #-- meta informations $this->created = time(); $this->{'created$'} = gmdate("r", $this->created); $this->expires = $this->created + CAPTCHA_TIMEOUT; //$this->tries = 0; $this->passed = 0; #-- captcha processing info $this->sent = 0; $this->tries = CAPTCHA_TRIES; // 5 $this->ajax_tries = CAPTCHA_AJAX_TRIES; // 25 $this->passed = 0; $this->maxpasses = CAPTCHA_MAXPASSES; // 2 $this->failures = 0; $this->shortcut = array(); $this->grant = 0; // unchecked access #-- mk IMAGE/GRAPHIC $this->image = (CAPTCHA_IMAGE_TYPE <= 1) ? new easy_captcha_graphic_image_waved() : new easy_captcha_graphic_image_disturbed(); //$this->image = new easy_captcha_graphic_cute_ponys(); #-- mk MATH/TEXT riddle $this->text = (CAPTCHA_NOTEXT >= 1) ? new easy_captcha_text_disable() : new easy_captcha_text_math_formula(); //$this->text = new easy_captcha_text_riddle(); #-- process granting cookie if (CAPTCHA_PERSISTENT) $this->shortcut[] = new easy_captcha_persistent_grant(); #-- spam-check: no URLs submitted if (CAPTCHA_NEW_URLS) $this->shortcut[] = new easy_captcha_spamfree_no_new_urls(); #-- store record $this->save(); } #-- examine if captcha data is fresh function is_valid() { return isset($this->id) && ($this->created) && ($this->expires > time()) && ($this->tries > 0) && ($this->failures < 500) && ($this->passed < $this->maxpasses) || $this->delete() || $this->log("is_valid", "EXPIRED", "and deleted") && false; } #-- new captcha tracking/storage id function new_id() { return "ec." . time() . "." . md5( $_SERVER["SERVER_NAME"] . CAPTCHA_SALT . rand(0,1<<30) ); } #-- check backends for correctness of solution function solved($in=NULL/*parameter only used in subclasses*/) { $ok = false; #-- failure if ((0 >= $this->tries--) || !$this->is_valid()) { // log, this is either a frustrated user or a bot knocking $this->log("::solved", "INVALID", "tries exhausted ($this->tries) or expired(?) captcha"); } #-- test elseif ($this->sent) { $in = @$_REQUEST[CAPTCHA_PARAM_INPUT]; // might be empty string #-- check individual modules $ok = $this->grant; foreach ($this->shortcut as $test) { $ok = $ok || $test->solved($in); // cookie & nourls } $ok = $ok // either letters or math formula submitted || isset($this->image) && $this->image->solved($in) || isset($this->text) && $this->text->solved($in); #-- update state if ($ok) { $this->passed++; $this->log("::solved", "OKAY", "captcha passed ($in) for image({$this->image->solution}) and text({$this->text->solution})"); #-- set cookie on success if (CAPTCHA_PERSISTENT) { $this->shortcut[0/*FIXME*/]->grant(); $this->log("::solved", "PERSISTENT", "cookie granted"); } } else { $this->failures++; $this->log("::solved", "WRONG", "solution failure ($in) for image({$this->image->solution}) and text({$this->text->solution})"); } } #-- remove if done if (!$this->is_valid() /*&& !$this->delete()*/) { $this->generate(); // ensure object instance can be reused - for quirky form processing logic } #-- store state/result else { $this->save(); } #-- return result return($ok); } #-- combines ->image and ->text data into form fields function form($add_text="→ ") { #-- store object data $this->sent++; $this->save(); #-- check for errors $errors = array( "invalid object created" => !$this->is_valid(), "captcha_id storage could not be saved" => !$this->saved, "no ->id present" => empty($this->id), "no ->created timestamp" => empty($this->created), ); if (array_sum($errors)) { return '
*' . implode("
*", array_keys(array_filter($errors))) . '
'; } #-- prepare output vars $p_id = CAPTCHA_PARAM_ID; $p_input = CAPTCHA_PARAM_INPUT; $base_url = CAPTCHA_BASE_URL . '?' . CAPTCHA_PARAM_ID . '='; $id = htmlentities($this->id); $img_url = $base_url . $id; $alt_text = htmlentities($this->text->question); $new_urls = CAPTCHA_NEW_URLS ? 0 : 1; $onClick = CAPTCHA_ONCLICK_HIRES ? 'onClick="this.src += this.src.match(/hires/) ? \'.\' : \'hires=1&\';"' : 'onClick="this.src += \'.\';"'; $onKeyDown = CAPTCHA_AJAX ? 'onKeyUp="captcha_check_solution()"' : ''; $javascript = CAPTCHA_AJAX ? '' : ''; $error = function_exists('imagecreatetruecolor') ? '' : '
PHP setup lacks GD. No image drawing possible
'; #-- assemble $HTML = //'' . // workaround for double instantiations '
' . $error . '' . ''.$alt_text.'' . ' ' . $add_text . '' . $javascript . '
'; return($HTML); } #-- noteworthy stuff goes here function log($error, $category, $message) { // append to text file if (CAPTCHA_LOG) { file_put_contents( CAPTCHA_TEMP_DIR . "/captcha.log", "[$error] -$category- \"$message\" $_SERVER[REMOTE_ADDR] id={$this->id} tries={$this->tries} failures={$this->failures} created/time/expires=$this->created/".time()."/$this->expires \n", FILE_APPEND|LOCK_EX ); } return(TRUE); // for if-chaining } #-- load object from saved captcha tracking data function load() { $fn = $this->data_file(); if (file_exists($fn)) { $saved = (array)@unserialize(fread(fopen($fn, "r"), 1<<20)); foreach ($saved as $i=>$v) { $this->{$i} = $v; } } else { $this->log("captcha file does not exist $fn"); } } #-- save $this captcha state function save() { $this->straighten_temp_dir(); if ($fn = $this->data_file()) { $this->saved = file_put_contents($fn, serialize($this), LOCK_EX); } } #-- remove $this data file function delete() { // delete current and all previous data files $this->prev[] = $this->id; if (isset($this->prev)) { foreach ($this->prev as $id) { @unlink($this->data_file($id)); } } // clean object foreach ((array)$this as $name=>$val) { unset($this->{$name}); } return(FALSE); // far if-chaining in ->is_valid() } #-- clean-up or init temporary directory function straighten_temp_dir() { // create dir if (!file_exists($dir=CAPTCHA_TEMP_DIR)) { mkdir($dir); } // clean up old files if ((rand(0,100) <= 5) && ($dh = opendir($dir))) { $t_kill = time() - CAPTCHA_TIMEOUT * 1.2; while(false !== ($fn = readdir($dh))) if ($fn[0] != ".") { if (filemtime("$dir/$fn") < $t_kill) { @unlink("$dir/$fn"); } } } } #-- where's the storage? function data_file($id=NULL) { return CAPTCHA_TEMP_DIR . "/" . preg_replace("/[^-,.\w]/", "", ($id?$id:$this->id)) . ".a()"; } #-- unreversable hash from passphrase, with time() slice encoded function hash($text, $dtime=0, $length=1) { $text = strtolower($text); $pfix = (int) (time() / $length*CAPTCHA_TIMEOUT) + $dtime; return md5("captcha::$pfix:$text::".__FILE__.":$_SERVER[SERVER_NAME]:80"); } } #-- checks the supplied solution, allows differences (incorrectly guessed letters) class easy_captcha_fuzzy extends easy_captcha { #-- ratio of letters that may differ between solution and real password var $fuzzy = CAPTCHA_FUZZY; #-- compare function solved($in = null) { if ($in) { $pw = strtolower($this->solution); $in = strtolower($in); $diff = levenshtein($pw, $in); $maxdiff = strlen($pw) * (1 - $this->fuzzy); return ($pw == $in) or ($diff <= $maxdiff); // either matches, or allows around 2 divergent letters } } } #-- image captchas, base and utility code class easy_captcha_graphic extends easy_captcha_fuzzy { #-- config function easy_captcha_graphic($x=NULL, $y=NULL) { if (!$y) { $x = strtok(CAPTCHA_IMAGE_SIZE, "x,|/*;:"); $y = strtok(",."); $x = rand($x * 0.9, $x * 1.2); $y = rand($y - 5, $y + 15); } $this->width = $x; $this->height = $y; $this->inverse = CAPTCHA_INVERSE; $this->bg = CAPTCHA_BGCOLOR; $this->maxsize = 0xFFFFF; $this->quality = 66; $this->solution = $this->mkpass(); } #-- return a single .ttf font filename function font() { $fonts = array(/*"FreeMono.ttf"*/); $fonts += glob(CAPTCHA_FONT_DIR."/*.ttf"); return $fonts[rand(0,count($fonts)-1)]; } #-- makes string of random letters (for embedding into image) function mkpass() { $s = ""; for ($n=0; $n<10; $n++) { $s .= chr(rand(0, 255)); } $s = base64_encode($s); // base64-set, but filter out unwanted chars $s = preg_replace("/[+\/=IG0ODQR]/i", "", $s); // strips hard to discern letters, depends on used font type $s = substr($s, 0, rand(CAPTCHA_MIN_CHARS, CAPTCHA_MAX_CHARS)); return($s); } #-- return GD color function random_color($a,$b) { $R = $this->inverse ? 0xFF : 0x00; return imagecolorallocate($this->img, rand($a,$b)^$R, rand($a,$b)^$R, rand($a,$b)^$R); } function rgb ($r,$g,$b) { $R = $this->inverse ? 0xFF : 0x00; return imagecolorallocate($this->img, $r^$R, $g^$R, $b^$R); } #-- generate JPEG output function output() { ob_start(); ob_implicit_flush(0); imagejpeg($this->img, "", $this->quality); $jpeg = ob_get_contents(); ob_end_clean(); imagedestroy($this->img); unset($this->img); return($jpeg); } } #-- waived captcha image II class easy_captcha_graphic_image_waved extends easy_captcha_graphic { /* returns jpeg file stream with unscannable letters encoded in front of colorful disturbing background */ function jpeg() { #-- step by step $this->img = $this->create(); $this->text(); //$this->debug_grid(); $this->fog(); $this->distort(); return $this->output(); } #-- initialize in-memory image with gd library function create() { $img = imagecreatetruecolor($this->width, $this->height); // imagealphablending($img, TRUE); imagefilledrectangle($img, 0,0, $this->width,$this->height, $this->inverse ? $this->bg ^ 0xFFFFFF : $this->bg); //$this->rgb(255,255,255) if (function_exists("imageantialias")) { imageantialias($img, true); } return($img); } #-- add the real text to it function text() { $w = $this->width; $h = $this->height; $SIZE = rand(30,36); $DEG = rand(-2,9); $LEN = strlen($this->solution); $left = $w - $LEN * 25; $top = ($h - $SIZE - abs($DEG*2)); imagettftext($this->img, $SIZE, $DEG, rand(5,$left-5), $h-rand(3, $top-3), $this->rgb(0,0,0), $this->font(), $this->solution); } #-- to visualize the sinus waves function debug_grid() { for ($x=0; $x<250; $x+=10) { imageline($this->img, $x, 0, $x, 70, 0x333333); imageline($this->img, 0, $x, 250, $x, 0x333333); } } #-- add lines function fog() { $num = rand(10,25); $x = $this->width; $y = $this->height; $s = rand(0,270); for ($n=0; $n<$num; $n++) { imagesetthickness($this->img, rand(1,2)); imagearc($this->img, rand(0.1*$x, 0.9*$x), rand(0.1*$y, 0.9*$y), //x,y rand(0.1*$x, 0.3*$x), rand(0.1*$y, 0.3*$y), //w,h $s, rand($s+5, $s+90), // s,e rand(0,1) ? 0xFFFFFF : 0x000000 // col ); } imagesetthickness($this->img, 1); } #-- distortion: wave-transform function distort() { #-- init $single_pixel = (CAPTCHA_PIXEL<=1); // very fast $greyscale2x2 = (CAPTCHA_PIXEL<=2); // quicker than exact smooth 2x2 copy $width = $this->width; $height = $this->height; $i = & $this->img; $dest = $this->create(); #-- URL param ?hires=1 influences used drawing scheme if (isset($_GET["hires"])) { $single_pixel = 0; } #-- prepare distortion $wave = new easy_captcha_dxy_wave($width, $height); // $spike = new easy_captcha_dxy_spike($width, $height); #-- generate each new x,y pixel individually from orig $img for ($y = 0; $y < $height; $y++) { for ($x = 0; $x < $width; $x++) { #-- pixel movement list($dx, $dy) = $wave->dxy($x, $y); // x- and y- sinus wave // list($qx, $qy) = $spike->dxy($x, $y); #-- if not out of bounds if (($dx+$x>=0) && ($dy+$y>=0) && ($dx+$x<$width) && ($dy+$y<$height)) { #-- get source pixel(s), paint dest if ($single_pixel) { // single source dot: one-to-one duplicate (unsmooth, hard edges) imagesetpixel($dest, $x, $y, @imagecolorat($i, (int)$dx+$x, (int)$dy+$y)); } elseif ($greyscale2x2) { // merge 2x2 simple/greyscale (3 times as slow) $cXY = $this->get_2x2_greyscale($i, (int)$dx+$x, (int)$dy+$y); imagesetpixel($dest, $x,$y, imagecolorallocate($dest, $cXY, $cXY, $cXY)); } else { // exact and smooth transformation (5 times as slow) list($cXY_R, $cXY_G, $cXY_B) = $this->get_2x2_smooth($i, $x+$dx, $y+$dy); imagesetpixel($dest, $x,$y, imagecolorallocate($dest, (int)$cXY_R, (int)$cXY_G, (int)$cXY_B)); } } } } #-- simply overwrite ->img imagedestroy($i); $this->img = $dest; } #-- get 4 pixels from source image, merges BLUE value simply function get_2x2_greyscale(&$i, $x, $y) { // this is a pretty simplistic method, actually adds more artefacts // than it "smoothes" // it just merges the brightness from 4 adjoining pixels into one $cXY = (@imagecolorat($i, $x+$dx, $y+$dy) & 0xFF) + (@imagecolorat($i, $x+$dx, $y+$dy+1) & 0xFF) + (@imagecolorat($i, $x+$dx+1, $y+$dy) & 0xFF) + (@imagecolorat($i, $x+$dx+1, $y+$dy+1) & 0xFF); $cXY = (int) ($cXY / 4); return $cXY; } #-- smooth pixel reading (with x,y being reals, not integers) function get_2x2_smooth(&$i, $x, $y) { // get R,G,B values from 2x2 source area $c00 = $this->get_RGB($i, $x, $y); // +------+------+ $c01 = $this->get_RGB($i, $x, $y+1); // |dx,dy | x1,y0| $c10 = $this->get_RGB($i, $x+1, $y); // | rx-> | | $c11 = $this->get_RGB($i, $x+1, $y+1); // +----##+------+ // weighting by $dx/$dy fraction part // | ##|<-ry | $rx = $x - floor($x); $rx_ = 1 - $rx; // |x0,y1 | x1,y1| $ry = $y - floor($y); $ry_ = 1 - $ry; // +------+------+ // this is extremely slow, but necessary for correct color merging, // the source pixel lies somewhere in the 2x2 quadrant, that's why // RGB values are added proportionately (rx/ry/_) // we use no for-loop because that would slow it even further $cXY_R = (int) (($c00[0]) * $rx_ * $ry_) + (int) (($c01[0]) * $rx_ * $ry) // division by 4 not necessary, + (int) (($c10[0]) * $rx * $ry_) // because rx/ry/rx_/ry_ add up + (int) (($c11[0]) * $rx * $ry); // to 255 (=1.0) at most $cXY_G = (int) (($c00[1]) * $rx_ * $ry_) + (int) (($c01[1]) * $rx_ * $ry) + (int) (($c10[1]) * $rx * $ry_) + (int) (($c11[1]) * $rx * $ry); $cXY_B = (int) (($c00[2]) * $rx_ * $ry_) + (int) (($c01[2]) * $rx_ * $ry) + (int) (($c10[2]) * $rx * $ry_) + (int) (($c11[2]) * $rx * $ry); return array($cXY_R, $cXY_G, $cXY_B); } #-- imagegetcolor from current ->$img split up into RGB array function get_RGB(&$img, $x, $y) { $rgb = @imagecolorat($img, $x, $y); return array(($rgb >> 16) &0xFF, ($rgb >>8) &0xFF, ($rgb) &0xFF); } } #-- xy-wave deviation (works best for around 200x60) # cos(x,y)-idea taken from imagemagick class easy_captcha_dxy_wave { #-- init params function easy_captcha_dxy_wave($max_x, $max_y) { $this->dist_x = $this->real_rand(2.5, 3.5); // max +-x/y delta distance $this->dist_y = $this->real_rand(2.5, 3.5); $this->slow_x = $this->real_rand(7.5, 20.0); // =wave-width in pixel/3 $this->slow_y = $this->real_rand(7.5, 15.0); } #-- calculate source pixel position with overlapping sinus x/y-displacement function dxy($x, $y) { #-- adapting params $this->dist_x *= 1.000035; $this->dist_y *= 1.000015; #-- dest pixels (with x+y together in each of the sin() calcs you get more deformation, else just yields y-ripple effect) $dx = $this->dist_x * cos(($x/$this->slow_x) - ($y/1.1/$this->slow_y)); $dy = $this->dist_y * sin(($y/$this->slow_y) - ($x/0.9/$this->slow_x)); #-- result return array($dx, $dy); } #-- array of values with random start/end values function from_to_rand($max, $a, $b) { $BEG = $this->real_rand($a, $b); $DIFF = $this->real_rand($a, $b) - $BEG; $r = array(); for ($i = 0; $i <= $max; $i++) { $r[$i] = $BEG + $DIFF * $i / $max; } return($r); } #-- returns random value in given interval function real_rand($a, $b) { $r = rand(0, 1<<30); return( $r / (1<<30) * ($b-$a) + $a ); // base + diff * (0..1) } } #-- with spike class easy_captcha_dxy_spike { function dxy($x,$y) { #-- centre spike $y += 0.0; return array($x,$y); } } #-- colorful captcha image I class easy_captcha_graphic_image_disturbed extends easy_captcha_graphic { /* returns jpeg file stream with unscannable letters encoded in front of colorful disturbing background */ function jpeg() { #-- step by step $this->create(); $this->background_lines(); $this->background_letters(); $this->text(); return $this->output(); } #-- initialize in-memory image with gd library function create() { $this->img = imagecreatetruecolor($this->width, $this->height); imagefilledrectangle($this->img, 0,0, $this->width,$this->height, $this->random_color(222, 255)); #-- encolour bg $wd = 20; $x = 0; while ($x < $this->width) { imagefilledrectangle($this->img, $x, 0, $x+=$wd, $this->height, $this->random_color(222, 255)); $wd += max(10, rand(0, 20) - 10); } } #-- make interesting background I, lines function background_lines() { $c1 = rand(150, 185); $c2 = rand(195, 230); $wd = 4; $w1 = 0; $w2 = 0; for ($x=0; $x<$this->width; $x+=(int)$wd) { if ($x < $this->width) { // verical imageline($this->img, $x+$w1, 0, $x+$w2, $this->height-1, $this->random_color($c1++,$c2)); } if ($x < $this->height) { // horizontally ("y") imageline($this->img, 0, $x-$w2, $this->width-1, $x-$w1, $this->random_color($c1,$c2--)); } $wd += rand(0,8) - 4; if ($wd < 1) { $wd = 2; } $w1 += rand(0,8) - 4; $w2 += rand(0,8) - 4; if (($x > $this->height) && ($y > $this->height)) { break; } } } #-- more disturbing II, random letters function background_letters() { $limit = rand(30,90); for ($n=0; $n<$limit; $n++) { $letter = ""; do { $letter .= chr(rand(31,125)); // random symbol } while (rand(0,1)); $size = rand(5, $this->height/2); $half = (int) ($size / 2); $x = rand(-$half, $this->width+$half); $y = rand(+$half, $this->height); $rotation = rand(60, 300); imagettftext($this->img, $size, $rotation, $x, $y, $this->random_color(130, 240), $this->font(), $letter); } } #-- add the real text to it function text() { $phrase = $this->solution; $len = strlen($phrase); $w1 = 10; $w2 = $this->width / ($len+1); for ($p=0; $p<$len; $p++) { $letter = $phrase[$p]; $size = rand(18, $this->height/2.2); $half = (int) $size / 2; $rotation = rand(-33, 33); $y = rand($size+3, $this->height-3); $x = $w1 + $w2*$p; $w1 += rand(-$this->width/90, $this->width/40); // @BUG: last char could be +30 pixel outside of image $font = $this->font(); list($r,$g,$b) = array(rand(30,99), rand(30,99), rand(30,99)); imagettftext($this->img, $size, $rotation, $x+1, $y, $this->rgb($r*2,$g*2,$b*2), $font, $letter); imagettftext($this->img, $size, $rotation, $x, $y-1, $this->rgb($r,$g,$b), $font, $letter); } } } #-- arithmetic riddle class easy_captcha_text_math_formula extends easy_captcha { var $question = "1+1"; var $solution = "2"; #-- set up function easy_captcha_text_math_formula() { $this->question = sprintf(CAPTCHA_WHATIS_TEXT, $this->create_formula()); $this->solution = $this->calculate_formula($this->question); // we could do easier with iterated formula+result generation here, of course // but I had this code handy already ;) and it's easier to modify } #-- simple IS-EQUAL check function solved($result = null) { return (int)$this->solution == (int)$result; } #-- make new captcha formula string function create_formula() { $formula = array( rand(20,100) . " / " . rand(2,10), rand(50,150) . " - " . rand(2,100), rand( 2,100) . " + " . rand(2,100), rand( 2, 15) . " * " . rand(2,12), rand( 5, 10) . " * " . rand(5,10) . " - " . rand(1,20), rand(30,100) . " + " . rand(5,99) . " - " . rand(1,50), // rand(20,100) . " / " . rand(2,10) . " + " . rand(1,50), ); return $formula[rand(0,count($formula)-1)]; } #-- remove non-arithmetic characters function clean($s) { return preg_replace("/[^-+*\/\d]/", "", $s); } #-- "solve" simple calculations function calculate_formula($formula) { preg_match("#^(\d+)([-+/*])(\d+)([-+/*])?(\d+)?$#", $this->clean($formula), $uu); @list($uu, $X, $op1, $Y, $op2, $Z) = $uu; if ($Y) $calc = array( "/" => $X / $Y, // PHP+ZendVM catches division by zero already, and CAPTCHA "attacker" would get no advantage herefrom anyhow "*" => $X * $Y, "+" => $X + $Y, "-" => $X - $Y, "*-" => $X * $Y - $Z, "+-" => $X + $Y - $Z, "/+" => $X / $Y + $Z, ); return( $calc[$op1.$op2] ? $calc[$op1.$op2] : rand(0,1<<23) ); } } #-- to disable textual captcha part class easy_captcha_text_disable extends easy_captcha { var $question = ""; function solved($in = null) { return false; } } #-- shortcut, allow access for an user if captcha was previously solved # (should be identical in each instantiation, cookie is time-bombed) class easy_captcha_persistent_grant extends easy_captcha { function easy_captcha_persistent_grant() { } #-- give ok, if captach had already been solved recently function solved($ignore=0) { if (CAPTCHA_PERSISTENT && isset($_COOKIE[$this->cookie()])) { return in_array($_COOKIE[$this->cookie()], array($this->validity_token(), $this->validity_token(-1))); } } #-- set captcha persistence cookie function grant() { if (!headers_sent()) { setcookie($this->cookie(), $this->validity_token(), time() + 175*CAPTCHA_TIMEOUT); } else { // $this->log("::grant", "COOKIES", "too late for cookies"); } } #-- pseudo password (time-bombed) function validity_token($deviation=0) { return easy_captcha::hash("PERSISTENCE", $deviation, $length=100); } function cookie() { return "captcha_pass"; } } #-- simply check if no URLs were submitted - that's what most spambots do, # and simply grant access then class easy_captcha_spamfree_no_new_urls { #-- you have to adapt this, to check for newly added URLs only, in Wikis e.g. # - for simple comment submission forms, this default however suffices: function solved($ignore=0) { $r = !preg_match("#(https?://\w+[^/,.]+)#ims", serialize($_GET+$_POST), $uu); return $r; } } #-- "AJAX" and utility code # @static class easy_captcha_utility { #-- determine usable temp directory function tmp() { return current( array_filter( // filter by writability array_filter( // filter empty entries @array( $_SERVER['TMPDIR'], $_SERVER['REDIRECT_TMPDIR'], $_SERVER['TEMP'], ini_get('upload_tmp_dir'), $_SERVER['TMP'], $_SERVER['TEMPDIR'], function_exists("sys_get_temp_dir") ? sys_get_temp_dir() : "", '/tmp' ) ), "is_writable" ) ); } #-- script was called directly function API() { #-- load data if ($id = @$_GET[CAPTCHA_PARAM_ID]) { #-- special case if ($id == 'base.js') { easy_captcha_utility::js_base(); } else { $c = new easy_captcha($id=NULL, $ignore_expiration=1); $expired = !$c->is_valid(); #-- JS-RPC request, check entered solution on the fly if ($test = @$_REQUEST[CAPTCHA_PARAM_INPUT]) { #-- check if ($expired || empty($c->image)) { die(easy_captcha_utility::js_header('alert("captcha error: request invalid (wrong storage id) / or expired");')); } if (0 >= $c->ajax_tries--) { $c->log("::API", "JS-RPC", "ajax_tries exhausted ($c->ajax_tries)"); } $ok = $c->image->solved($test) || $c->text->solved($test); #-- sendresult easy_captcha_utility::js_rpc($ok); } #-- generate and send image file else { if ($expired) { $type = "image/png"; $bin = easy_captcha_utility::expired_png(); } else { $type = "image/jpeg"; $bin = $c->image->jpeg(); } header("Pragma: no-cache"); header("Cache-Control: no-cache, no-store, must-revalidate, private"); header("Expires: " . gmdate("r", time())); header("Content-Length: " . strlen($bin)); header("Content-Type: $type"); print $bin; } } exit; } } #-- hardwired error img function expired_png() { return base64_decode("iVBORw0KGgoAAAANSUhEUgAAADwAAAAUAgMAAACsbba6AAAADFBMVEUeEhFcMjGgWFf9jIrTTikpAAAACXBIWXMAAAsTAAALEwEAmpwYAAAA3UlEQVQY01XPzwoBcRAH8F9RjpSTm9xR9qQwtnX/latX0DrsA3gC8QDK0QO4bv7UOtmM+x4oZ4X5FQc1hlb41dR8mm/9ZhT/P7X/dDcpZPU3FYft9kWbLuWp4Bgt9v1oGG07Ja8ojfjxQFym02DVmoixkV/m2JI/TUtefR7nD9rkrhkC+6D77/8mUhDvw0ymLPwxf8esghEFRq8hqKcu2iG16Vlun1zYTO7RwCeFyoJqAgC3LQwzYiCokDj0MWRxb+Z6R8mPJb8Q77zlPbuCoJE8a/t7P773uv36tdcTmsXfRycoRJ8AAAAASUVORK5CYII="); } #-- send base javascript function js_base() { $captcha_new_urls = $_GET["captcha_new_urls"] ? 0 : 1; $BASE_URL = CAPTCHA_BASE_URL; $PARAM_ID = CAPTCHA_PARAM_ID; $PARAM_INPUT = CAPTCHA_PARAM_INPUT; $COLOR_CALC = CAPTCHA_INVERSE ? "32 +" : "224 -"; easy_captcha_utility::js_header(); print<<= 4) { inf.style.border = "2px solid #FF9955"; } // if enough letters entered if (len >= 4) { // remove old