| http://captchas.net |
|
This module can be downloaded here
<?php
//
// PHP module for easy utilization of the free captchas.net CAPTCHA service
//
// For documentation look at http://captchas.net/sample/php/
//
// Written by
// Sebastian Wilhelmi <seppi@seppi.de> and
// Felix Holderied <felix@holderied.de>
// This file is in the public domain.
//
// ChangeLog:
//
// 2006-08-16: New optional features integrated
//
// 2006-03-01: Only delete the random string from the repository in
// case of a successful verification.
//
// 2006-02-14: Add new image() method returning an HTML/JavaScript
// snippet providing a fault tolerant service.
//
// 2005-06-02: Initial version.
//
class CaptchasDotNet
{
function CaptchasDotNet ($client, $secret,
$random_repository = '/tmp/captchasnet-random-strings',
$cleanup_time = 3600,
$alphabet = 'abcdefghijklmnopqrstuvwxyz',
$letters = 6,
$width = 240,
$height = 80
)
{
$this->__client = $client;
$this->__secret = $secret;
$this->__random_repository = $random_repository;
$this->__cleanup_time = $cleanup_time;
$this->__time_stamp_file = $random_repository . '/__time_stamp__';
$this->__alphabet = $alphabet;
$this->__letters = $letters;
$this->__width = $width;
$this->__height = $height;
}
function __random_string ()
{
// The random string shall consist of small letters, big letters
// and digits.
$letters = "abcdefghijklmnopqrstuvwxyz";
$letters .= strtoupper ($letters) + "0123456789";
// The random starts out empty, then 40 random possible characters
// are appended.
$random_string = '';
for ($i = 0; $i < 40; $i++)
{
$random_string .= $letters{rand (0, strlen ($letters) - 1)};
}
// Return the random string.
return $random_string;
}
// Create a new random string and register it.
function random ()
{
// If the repository directory is does not yet exist, create it.
if (!is_dir ($this->__random_repository))
{
mkdir ($this->__random_repository);
}
// If the time stamp file does not yet exist, create it.
if (!is_file ($this->__time_stamp_file))
{
touch ($this->__time_stamp_file);
}
// Get the current time.
$now = time ();
// Determine the time, before which to remove random strings.
$cleanup_time = $now - $this->__cleanup_time;
// If the last cleanup is older than specified, cleanup the
// directory.
if (filemtime ($this->__time_stamp_file) < $cleanup_time)
{
$handle = opendir ($this->__random_repository);
while (true)
{
$filename = readdir ($handle);
if (!$filename)
{
break;
}
if ($filename != '.' && $filename != '..')
{
$filename = $this->__random_repository . '/' . $filename;
if (filemtime ($filename) < $cleanup_time)
{
unlink ($filename);
}
}
}
closedir ($handle);
touch ($this->__time_stamp_file);
}
// loop until a valid random string has been found and registered,
// but at most 20 times. If no valid random has been found during
// that time, there is something really wrong. Also show the error
// in the last run.
for ($remaining = 20; $remaining > 0; $remaining--)
{
// generate a new random string.
$random = $this->__random_string ();
// open a file with the corresponding name in the repository
// directory in such a way, that the creation fails, when the
// file already exists. That should be near to impossible with
// good seeding of the random number generator, but it's better
// to play safe. If this is the last run, show the possible
// error message.
$filename = $this->__random_repository . '/' . $random;
if ($remaining == 1)
{
$file = fopen ($filename, 'x');
}
else
{
$file = @fopen ($filename, 'x');
}
if ($file)
{
fclose ($file);
break;
}
// if the file already existed, rerun the loop to try the next
// string.
}
// return the successfully registered random string.
$this->__random = $random;
return $random;
}
//
// Generates image-URL Parameters are only atached if different from default
//
function image_url ($random = False, $base = 'http://image.captchas.net/')
{
if (!$random)
{
$random = $this->__random;
}
$image_url = $base;
$image_url .= '?client=' . $this->__client;
$image_url .= '&random=' . $random;
if ($this->__alphabet!='abcdefghijklmnopqrstuvwxyz') {$image_url .= '&alphabet=' . $this->__alphabet;};
if ($this->__letters!=6) {$image_url .= '&letters=' . $this->__letters;};
if ($this->__width!=240) {$image_url .= '&width=' . $this->__width;};
if ($this->__height!=80) {$image_url .= '&height=' . $this->__height;};
return $image_url;
}
//
// Same as image_url but without width and height
//
function audio_url ($random = False, $base = 'http://audio.captchas.net/')
{
if (!$random)
{
$random = $this->__random;
}
$audio_url = $base;
$audio_url .= '?client=' . $this->__client;
$audio_url .= '&random=' . $random;
if ($this->__alphabet!='abcdefghijklmnopqrstuvwxyz') {$audio_url .= '&alphabet=' . $this->__alphabet;};
if ($this->__letters!=6) {$audio_url .= '&letters=' . $this->__letters;};
return $audio_url;
}
//
// Generates complete html-sample with javascript to reload image from
// backup server
//
function image ($random = False, $id = 'captchas.net')
{
$image = <<<EOT
<a href="http://captchas.net"><img
style="border: none; vertical-align: bottom"
id="@ID@" src="@URL@" width="@WIDTH@" height="@HEIGHT@"
alt="The Captcha image" /></a>
<script type="text/javascript">
<!--
function captchas_image_error (image)
{
if (!image.timeout) return true;
image.src = image.src.replace (/^http:\/\/image\.captchas\.net/,
'http://image.backup.captchas.net');
return captchas_image_loaded (image);
}
function captchas_image_loaded (image)
{
if (!image.timeout) return true;
window.clearTimeout (image.timeout);
image.timeout = false;
return true;
}
var image = document.getElementById ('@ID@');
image.onerror = function() {return captchas_image_error (image);};
image.onload = function() {return captchas_image_loaded (image);};
image.timeout
= window.setTimeout(
"captchas_image_error (document.getElementById ('@ID@'))",
10000);
image.src = image.src;
//-->
</script>
EOT;
$image = str_replace ('@HEIGHT@', $this->__height, $image);
$image = str_replace ('@WIDTH@', $this->__width, $image);
$image = str_replace ('@ID@', $id, $image);
$image = str_replace ('@URL@', $this->image_url (), $image);
return $image;
}
function validate ($random)
{
$this->__random = $random;
$file_name = $this->__random_repository . '/' . $random;
// Find out, whether the file exists
$result = is_file ($file_name);
// if the file exists, remember it.
if ($result)
{
$this->__random_file = $file_name;
}
// the random string was valid, if and only if the corresponding
// file existed.
return $result;
}
function verify ($input, $random = False)
{
if (!$random)
{
$random = $this->__random;
}
$password_letters = $this->__alphabet;
$password_length = $this->__letters;
// If the user input has the wrong lenght, it can't be correct.
if (strlen ($input) != $password_length)
{
return False;
}
// Calculate the MD5 digest of the concatenation of secret key and
// random string. The digest is a hex string.
$encryption_base = $this->__secret . $random;
// This extension is needed for secure use of optional parameters
// In case of standard use we do not append the values, to be
// compatible to existing implementations
if(($password_letters != 'abcdefghijklmnopqrstuvwxyz') || ($password_length != '6'))
{
$encryption_base = $encryption_base . ':' . $password_letters . ':' . $password_length;
}
$digest = md5 ($encryption_base);
// Check the password according to the rules from the first
// positions of the digest.
for ($pos = 0; $pos < $password_length; $pos++)
{
$letter_num
= hexdec (substr ($digest, 2 * $pos, 2)) % strlen ($password_letters);
// If the letter at the current position is wrong, the user
// input isn't correct.
if ($input[$pos] != $password_letters[$letter_num])
{
return False;
}
}
// if the file exists, remove it.
if ($this->__random_file)
{
unlink ($this->__random_file);
unset ($this->__random_file);
}
// The user input was correct.
return True;
}
}
?>
| XHTML 1.1 compliant | A service of Felix Holderied and Sebastian Wilhelmi (Contact) | mail@captchas.net |