69 lines
2.6 KiB
PHP
69 lines
2.6 KiB
PHP
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<?php
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/***********************************************
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* Comment Key Generation System
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***********************************************
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* By Starbeamrainbowlabs <feedback@starbeamrainbowlabs.com>
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*
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* A set of functions to protect low-value comment boxes, contact us
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* forms, etc. from spam.
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*
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* It works by recording the time the page the form is on was loaded,
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* and then checking to make sure that it was loaded for at least
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* 10 - 15 seconds, and not more than 24 hours.
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*
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* This is done by taking the current UNIX timestamp, running it through
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* a number of (arbitrary) reversible transformations, and then
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* embedding it in the form as a hidden field. When the form is
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* submitted, the transformations are reversed and the time the page
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* was loaded checked.
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*
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* Note that this is not suitable for high-value targets, as it can very
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* easily be bypassed and reverse-engineered by any determined human.
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*
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***********************************************
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* Changelog:
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* 30th January 2018:
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* Initial Release.
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*/
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/**
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* Generates a new comment key.
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* Note that the 'encryption' used is not secure - it's just simple XOR!
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* It's mainly to better support verification in complex setups and
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* serve as a nother annoying hurdle for spammers.
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* TODO: Swap out the XOR for openssl AES symmetric encryption
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* @param string $pass The password to transform it with. Should be a pre-selected random string.
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* @return string A new comment key stamped at the current time.
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*/
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function key_generate($pass) {
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$new_key = strval(time());
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// Repeat the key so that it's long enough to XOR the key with
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$pass_enc = str_repeat($pass, (strlen($new_key) / strlen($pass)) + 1);
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$new_key = $new_key ^ $pass_enc;
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return base64_encode(strrev($new_key));
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}
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/**
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* Decodes the given key.
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* @param string $key The key to decode.
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* @param string $pass The password to decode it with.
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* @return int The time that the key was generated.
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*/
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function key_decode($key, $pass) {
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$key_dec = strrev(base64_decode($key));
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// Repeat the key so that it's long enough to XOR the key with
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$pass_dec = str_repeat($pass, (strlen($key_dec) / strlen($pass)) + 1);
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return intval($key_dec ^ $pass_dec);
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}
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/**
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* Verifies a key.
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* @param string $key The key to decode and verify.
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* @param string $pass The password to decode the key with.
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* @param int $min_age The minimum required age for the key.
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* @param int $max_age The maximum allowed age for the key.
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* @return bool Whether the key is valid or not.
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*/
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function key_verify($key, $pass, $min_age, $max_age) {
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$age = time() - key_decode($key, $pass);
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return $age >= $min_age && $age <= $max_age;
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}
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