<?php require_once '../yubiphpbase/appinclude.php';
	  require_once '../yubiphpbase/yubi_lib.php';
	  require_once 'common.php';
	  
header("content-type: text/plain");

if (!isset($trace)) { $trace = 0; }

$client = getHttpVal('id', 0);
if ($client <= 0) {
	debug('Client ID is missing');
	sendResp(S_MISSING_PARAMETER, 'id');
	exit;
}

$otp = getHttpVal('otp', '');
if ($otp == '') {
	debug('OTP is missing');
	sendResp(S_MISSING_PARAMETER, 'otp');
	exit;
}

//// Get Yubikey from DB
//
$devId = substr($otp, 0, 12);
$ad = getAuthData($devId);
debug('Auth Data from DB:');

if ($ad == null) {
	debug('Invalid Yubikey '.$devId);
	sendResp(S_BAD_OTP, $otp);
	exit;
} else {
	debug($ad);
}

//// Check the client ID
//
// TODO - This may be too strict. Since our database doesn't keep track of that

//if ($ad['client_id'] != $client) {
//	debug('Client-'.$client.' is not the owner of the Yubikey! The key will be suspended with excessive failed attempts.');
//	sendResp(S_BAD_CLIENT, 'Not owner of the Yubikey');
//	exit;
//}

$k = b64ToModhex($ad['secret']);
//debug('aes key in modhex = '.$k);
$key16 = ModHex::Decode($k);
//debug('aes key in hex = ['.$key16.'], length = '.strlen($key16));
$apiKey = base64_decode($ad['c_secret']);
	
//// Check signature
//
if ($ad['chk_sig']) {
	// Create the signature using the API key
	$a = array();
	$a['id']=$client;
	$a['otp']=$otp;
	$hmac = sign($a, $apiKey);

	if (($h = getHttpVal('h', '')) == '') {
		sendResp(S_MISSING_PARAMETER, 'h');
		debug('signature missing, hmac='.$hmac);
		exit;
	} else if ($hmac != $h) {
		sendResp(S_BAD_SIGNATURE);
		debug('h='.$h.', hmac='.$hmac);
		exit;
	}
}


//// Decode OTP from input
//
debug('From the OTP validation request:');
$decoded_token = Yubikey::Decode($otp, $key16);
debug($decoded_token);
if ( ! is_array($decoded_token) ) {
	sendResp(S_BAD_OTP, $otp);
	exit;
}

//// Sanity check key status
//
if ($ad['active'] < 1) {
	sendResp(S_BAD_OTP, 'Suspended');
	exit;
}

//// Sanity check client status
//
if ($ad['c_active'] < 1) {
	sendResp(S_BAD_CLIENT);
	exit;
}

//// Sanity check token ID
//
if (strlen($decoded_token["public_id"]) == 12 ) {
	debug("Token ID OK (".$decoded_token["public_id"].")");
} else { 
	debug("TOKEN ID FAILED, ".$decoded_token["public_id"]); 
	sendResp(S_BAD_OTP, $otp);
	exit;
}

//// Sanity check the OTP
//
if ( strlen($decoded_token["token"]) != 32) {
	debug("Wrong OTP length,".strlen($decoded_token["token"]));
	sendResp(S_BAD_OTP, $otp);
	exit;	 
}

//// Check the session counter
//
$sessionCounter = $decoded_token["session_counter"]; // From the req
$seenSessionCounter = $ad['counter']; // From DB
$scDiff = $seenSessionCounter - $sessionCounter;
if ($scDiff > 0) {
	debug("Replayed session counter=".$sessionCounter.', seen='.$seenSessionCounter);
	sendResp(S_REPLAYED_OTP);
	exit;
} else {
	debug("Session counter OK (".$sessionCounter.")");
}

//// Check the high counter
//
$hi = $decoded_token["high"]; // From the req
$seenHi = $ad['high']; // From DB
$hiDiff = $seenHi - $hi;
if ($scDiff == 0 && $hiDiff > 0) {
	debug("Replayed hi counter=".$hi.', seen='.$seenHi);
	sendResp(S_REPLAYED_OTP);
	exit;
} else {
	debug("Hi counter OK (".$hi.")");
}

//// Check the low counter
//
$lo = $decoded_token["low"]; // From the req
$seenLo = $ad['low']; // From DB
$loDiff = $seenLo - $lo;
if ($scDiff == 0 && $hiDiff == 0 && $loDiff >= 0) {
	debug("Replayed low counter=".$lo.', seen='.$seenLo);
	sendResp(S_REPLAYED_OTP);
	exit;
} else {
	debug("Lo counter OK (".$lo.")");
}

//// Update the DB only upon validation success
//
if (updDB($ad['id'], $decoded_token)) {
	debug('Validation database updated');	
	sendResp(S_OK);
} else {
	debug('Failed to update validation database');
	sendResp(S_BACKEND_ERROR);
}

//////////////////////////
// 		Functions
//////////////////////////

function sendResp($status, $info=null) {
	global $ad, $apiKey;

	if ($status == null) {
		$status = S_BACKEND_ERROR;
	}

	echo 'status='.($a['status'] = $status).PHP_EOL;
	if ($info != null) {
		echo 'info='.($a['info'] = $info).PHP_EOL;
	}
	echo 't='.($a['t']=getUTCTimeStamp()).PHP_EOL;
	$h = sign($a, $apiKey);
	echo 'h='.$h.PHP_EOL;
	echo PHP_EOL;

} // End sendResp

function updDB($keyid, $new) {
	$stmt = 'UPDATE yubikeys SET '.
		'accessed=NOW(),'.
		'counter='.$new['session_counter'].','.
		'low='.$new['low'].','.
		'high='.$new['high'].
		' WHERE id='.$keyid;
	if (!query($stmt)) {
		$err = 'Failed to update validation data of key: '.$keyid.' by '.$stmt;
		debug($err);
		writeLog($err);
		return false;
	}
	return true;
}

?>