<?php
//============================================================================
// Name : keyLib.php
// Author : Patrick Reipschläger, Lucas Woltmann
// Version : 2.0
// Date : 01-2017
// Description : Provides several functions for creating and handling keys
// for the ESE evaluation for students and tutors.
//============================================================================
// Constant for the file which contains the keys, should be used by all other scripts so it can easily be changed
define ("KEYFILE", "db/eseeva.db");
// Constants for the different key states that are possible, should always be used when altering or checking the state of a key
define ("KEYSTATE_NONEXISTENT", "nonexistent");
define ("KEYSTATE_UNISSUED", "unissued");
define ("KEYSTATE_ISSUED", "issued");
define ("KEYSTATE_ACTIVATED", "activated");
define ("KEYSTATE_USED", "used");
/**
* Generates a key from the specified hash value.
*
* @return string
*/
function GenerateKey()
{
// create a hash using a unique id based on the servers system time and the sha1 hashing algorithm
$hash = strtoupper(hash("sha1", uniqid()));
// extract the desired number of digits out of the hash to generate the key
return substr($hash, 0, 4) . "-" . substr($hash, 4, 4) . "-" . substr($hash, 8, 4) . "-" . substr($hash, 12, 4);
//return substr($hash, 0, 2) . "-" . substr($hash, 2, 2) . "-" . substr($hash, 4, 2) . "-" . substr($hash, 6, 2);
}
/**
* Generates the specified amount of keys. Be aware that this function just
* creates an array of keys with no state assigned.
*
* @param integer $amount The amount of keys that should be generated
* @return array
*/
function GenerateKeys($amount)
{
$keys = array();
for ($i = 0; $i < $amount; $i++)
{
array_push($keys, GenerateKey());
usleep(1);
}
return array_unique($keys);
}
/**
* Generates a new keys in the database.
* Returns true if the key file was created successfully, otherwise false.
*
* @param integer $keyAmount The amount of keys that should be generated.
* @param string $fileName The name of the key database that should be created.
*/
function CreateKeys($keyAmount, $fileName)
{
$handle = new SQLite3($fileName);
if (!$handle)
return false;
$handle->exec("DROP TABLE IF EXISTS answers;");
$handle->exec("CREATE TABLE IF NOT EXISTS 'answers'(KeyId text primary key,Status text,Student int,Answer);");
$keys = GenerateKeys($keyAmount);
$count = count($keys);
for ($i = 0; $i < $count; $i++)
{
$stmt = $handle->prepare("INSERT INTO answers (KeyId, Status) VALUES (:key,:status);");
if ($stmt)
{
$stmt->bindValue(':key', $keys[$i], SQLITE3_TEXT);
$stmt->bindValue(':status', KEYSTATE_UNISSUED, SQLITE3_TEXT);
$result = $stmt->execute();
}
else
{
$handle->close();
return false;
}
}
$handle->close();
return true;
}
function AppendKeys($keyAmount, $fileName)
{
$handle = new SQLite3($fileName, SQLITE3_OPEN_READWRITE);
if (!$handle)
return false;
$keys = GenerateKeys($keyAmount);
$count = count($keys);
for ($i = 0; $i < $count; $i++)
{
$stmt = $handle->prepare("INSERT INTO answers (KeyId, Status) VALUES (:key,:status);");
if ($stmt)
{
$stmt->bindValue(':key', $keys[$i], SQLITE3_TEXT);
$stmt->bindValue(':status', KEYSTATE_UNISSUED, SQLITE3_TEXT);
$result = $stmt->execute();
}
else
{
$handle->close();
return false;
}
}
$handle->close();
return true;
}
/**
* Opens the database with the specified name and reads all key data that the database contains.
* The resulting data type will be an array of arrays consisting of the key and its state.
* Returns null if the key file could not be found or read.
*
* @param string $fileName The database which should be read.
* @return array
*/
function ReadKeys($fileName)
{
if (!file_exists($fileName))
return null;
$handle = new SQLite3($fileName, SQLITE3_OPEN_READONLY);
if (!$handle)
return null;
$data = $handle->query("SELECT KeyId, Status FROM answers;");
$data = PrepareResult($data);
$handle->close();
if ($data)
{
return $data;
}
return array();
}
/**
* Get the current state of the specified key from the database, which will be one of the defines
* KEYSTATE constants.
*
* @param array $fileName The database with the keys.
* @param string $key The key which state should be got. Passed by reference.
* @return integer
*/
function GetKeyState($fileName, &$key)
{
if (!file_exists($fileName))
return null;
$handle = new SQLite3($fileName, SQLITE3_OPEN_READONLY);
if (!$handle)
return null;
$stmt = $handle->prepare("SELECT Status FROM answers WHERE KeyId=:keyid;");
if ($stmt)
{
$stmt->bindValue(':keyid', $key, SQLITE3_TEXT);
$result = $stmt->execute();
$result = $result->fetchArray(SQLITE3_ASSOC);
$handle->close();
return $result["Status"];
}
$handle->close();
return KEYSTATE_NONEXISTENT;
}
/**
* Set the state of the specified key to the specified state.
* Returns true if the key was found within the key data and the state has been changed, otherwise false.
*
* @param array $fileName The database in which the key should be found.
* @param string $key The key which state should be changed.
* @param integer $newState The new state of the specified key. Must be on of the KEYSTATE constants.
* @return boolean
*/
function SetKeyState($fileName, &$key, $newState)
{
if (!file_exists($fileName))
return false;
$handle = new SQLite3($fileName, SQLITE3_OPEN_READWRITE);
if (!$handle)
return false;
//secure override by checking if key has been uesed already
$stmt = $handle->prepare("UPDATE answers SET Status=:status WHERE KeyId=:keyid AND Status!=:status;");
if ($stmt)
{
$stmt->bindValue(':keyid', $key, SQLITE3_TEXT);
$stmt->bindValue(':status', $newState, SQLITE3_TEXT);
$result = $stmt->execute();
$handle->close();
return true;
}
$handle->close();
return false;
}
/**
* Deletes a single key in the database if it has not been used yet.
* Returns true if the key was deleted, otherwise false.
*
* @param array $fileName The database in which the key should be found.
* @param string $key The key which should be deleted.
* @return boolean
*/
function DeleteKey($fileName, &$key)
{
if (!file_exists($fileName))
return false;
$handle = new SQLite3($fileName, SQLITE3_OPEN_READWRITE);
if (!$handle)
return false;
//secure deleting by checking if key has been uesed already
$stmt = $handle->prepare("DELETE FROM answers WHERE KeyId=:keyid AND Answer IS NULL;");
if ($stmt)
{
$stmt->bindValue(':keyid', $key, SQLITE3_TEXT);
$result = $stmt->execute();
$handle->close();
return true;
}
$handle->close();
return false;
}
/**
* Prepares the results from the database to an array of keys with their state.
*
* @param array $resultSet Cursor from the sqlite database. Passed by reference.
* @return array
*/
function PrepareResult(&$resultSet)
{
$result = array();
$i = 0;
while($res = $resultSet->fetchArray(SQLITE3_ASSOC))
{
foreach ($res as $key => $value) {
$result[$i][$key] = $value;
}
$i++;
}
return $result;
}
?>