yubikey-val/verify.php

<?php
require_once 'common.php';

header("content-type: text/plain");

if (!isset ($trace)) {
	$trace = 0;
}

//// Extract values from HTTP request
//
$client = getHttpVal('id', 0);
if ($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;
}
$otp = strtolower($otp);

//// Get Client info from DB
//
$cd = getClientData($client);
if ($cd == null) {
	debug('Invalid client id ' . $client);
	sendResp(S_NO_SUCH_CLIENT, $client);
	exit;
}
debug($cd);

//// Check client signature
//
$apiKey = base64_decode($cd['secret']);
$h = getHttpVal('h', '');

if ($cd['chk_sig'] && $h == '') {
	sendResp(S_MISSING_PARAMETER, 'h');
	debug('Signature missing');
	exit;
} else if ($cd['chk_sig'] || $h != '') {
	// Create the signature using the API key
	$a = array ();
	$a['id'] = $client;
	$a['otp'] = $otp;
	$hmac = sign($a, $apiKey);

	// Compare it
	if ($hmac != $h) {
		sendResp(S_BAD_SIGNATURE);
		debug('client hmac=' . $h . ', server hmac=' . $hmac);
		exit;
	}
	debug('signature ok h=' . $h);
}

//// Get Yubikey from DB
//
$devId = substr($otp, 0, 12);
$ad = getAuthData($devId);

if ($ad == null) {
	debug('Invalid Yubikey ' . $devId);
	sendResp(S_BAD_OTP, $otp);
	exit;
} else {
	debug($ad);
}

$k = b64ToModhex($ad['secret']);
//debug('aes key in modhex = '.$k);
$key16 = ModHex :: Decode($k);
//debug('aes key in hex = ['.$key16.'], length = '.strlen($key16));

//// Decode OTP from input
//
debug('OTP validation req:');
$decoded_token = Yubikey :: Decode($otp, $key16);
debug($decoded_token);
if (!is_array($decoded_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 session use
//
$sessionUse = $decoded_token["session_use"]; // From the req
$seenSessionUse = $ad['sessionUse']; // From DB
$sucDiff = $seenSessionUse - $sessionUse;
if ($sucDiff > 0) {
	debug("Replayed session use=" . $sessionUse . ', seen=' . $seenSessionUse);
	sendResp(S_REPLAYED_OTP);
	exit;
} else {
	debug("Session counter OK (" . $sessionCounter . ")");
}

//// Check the time stamp
//
if ($scDiff == 0) { // Same use session, check time stamp diff
	$ts = $decoded_token['timestamp'];
	$seenTs = ($ad['high'] << 16) + $ad['low'];
	$tsDiff = $ts - $seenTs;
	if ($tsDiff <= 0) {
		debug("Replayed time stamp=" . $ts . ', seen=' . $seenTs);
		sendResp(S_REPLAYED_OTP);
		exit;
	} else {
		updDB($ad['id'], $decoded_token, $client);
		$tsDelta = $tsDiff * TS_SEC;
		debug("Timestamp OK (" . $ts . ") delta count=" . $tsDiff .
		'-> delta secs=' . $tsDelta);
	}

	//// Check the real time
	//
	
	if ($ad['chk_time']) {
		$lastTime = strtotime($ad['accessed']);
		debug('Last accessed: '.$ad['accessed'].', '.$lastTime.', '.date("F j, Y, g:i a", $lastTime));
		$elapsed = time() - $lastTime;
		debug('Elapsed time from last validation: ' . $elapsed . ' secs');
		$deviation = abs($elapsed - $tsDelta);
		$percent = truncate(100*$deviation/$elapsed, 8) . '%';
		debug("Key time deviation vs. elapsed time=".$deviation.' secs ('.
			$percent.')');
		if ($deviation > TS_TOLERANCE * $elapsed) {
			debug("Is the OTP generated from a real crypto key?");
			sendResp(S_PHISHED_OTP);
			exit;
		}
	}
} // End check time stamp

//// 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, $client)) {
	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;
	}

	$a['status'] = $status;
	#$a['info'] = $info;
	$a['t'] = getUTCTimeStamp();
	$h = sign($a, $apiKey);

	echo "h=" . $h . "\r\n";
	echo "t=" . ($a['t']) . "\r\n";
	echo "status=" . ($a['status']) . "\r\n";
	if ($a['info'] != null) {
		echo "info=" . ($a['info']) . "\r\n";
	}
	echo "\r\n";

} // End sendResp

function updDB($keyid, $new, $client) {
	$stmt = 'UPDATE yubikeys SET ' .
	'accessed=NOW(),' .
	'counter=' . $new['session_counter'] . ',' .
	'sessionUse=' . $new['session_use'] . ',' .
	'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;
}
?>