<?php
require_once 'ykval-common.php';
require_once 'ykval-config.php';
require_once 'ykval-synclib.php';

$apiKey = '';

header("content-type: text/plain");


$myLog = new Log('ykval-sync');
$myLog->addField('ip', $_SERVER['REMOTE_ADDR']);

if(empty($_SERVER['QUERY_STRING'])) {
  sendResp(S_MISSING_PARAMETER, $myLog, $apiKey);
  exit;
}

$myLog->log(LOG_INFO, "Request: " . $_SERVER['QUERY_STRING']);

$sync = new SyncLib('ykval-sync:synclib');
$sync->addField('ip', $_SERVER['REMOTE_ADDR']);

if (! $sync->isConnected()) {
  sendResp(S_BACKEND_ERROR, $myLog, $apiKey);
  exit;
 }

#
# Verify that request comes from valid server
#

$myLog->log(LOG_INFO, 'Received request from ' . $_SERVER['REMOTE_ADDR']);
$allowed=False;
foreach ($baseParams['__YKVAL_ALLOWED_SYNC_POOL__'] as $server) {
  if ($_SERVER['REMOTE_ADDR'] == $server) {
    $allowed=True;
    break;
  }
}
if (!$allowed) {
  $myLog->log(LOG_NOTICE, 'Operation not allowed from IP ' . $_SERVER['REMOTE_ADDR']);
  $myLog->log(LOG_DEBUG, 'Remote IP ' . $_SERVER['REMOTE_ADDR'] . ' not listed in allowed sync pool : ' .
	      implode(', ', $baseParams['__YKVAL_ALLOWED_SYNC_POOL__']));
  sendResp(S_OPERATION_NOT_ALLOWED, $myLog, $apiKey);
  exit;
 }

#
# Define requirements on protocoll
#

$syncParams=array('modified'=>Null,
		  'otp'=>Null,
		  'nonce'=>Null,
		  'yk_publicname'=>Null,
		  'yk_counter'=>Null,
		  'yk_use'=>Null,
		  'yk_high'=>Null,
		  'yk_low'=>Null);

#
# Extract values from HTTP request
#

$tmp_log = "Received ";
foreach ($syncParams as $param=>$value) {
  $value = getHttpVal($param, Null);
  if ($value==Null) {
    $myLog->log(LOG_NOTICE, "Received request with parameter[s] (" . $param . ") missing value");
    sendResp(S_MISSING_PARAMETER, $myLog, $apiKey);
    exit;
  }
  $syncParams[$param]=$value;
  $tmp_log .= "$param=$value ";
}
$myLog->log(LOG_INFO, $tmp_log);

#
# At this point we should have to otp so let's add it to the logging module
#
$myLog->addField('otp', $syncParams['otp']);
$sync->addField('otp', $syncParams['otp']);

#
# Verify correctness of input parameters
#

foreach (array('modified') as $param) {
  if (preg_match("/^[0-9]+$/", $syncParams[$param])==0) {
    $myLog->log(LOG_NOTICE, 'Input parameters ' . $param . ' not correct');
    sendResp(S_MISSING_PARAMETER, $myLog, $apiKey);
    exit;
  }
}

foreach (array('yk_counter', 'yk_use', 'yk_high', 'yk_low') as $param) {
  if (preg_match("/^(-1|[0-9]+)$/", $syncParams[$param])==0) {
    $myLog->log(LOG_NOTICE, 'Input parameters ' . $param . ' not correct');
    sendResp(S_MISSING_PARAMETER, $myLog, $apiKey);
    exit;
  }
}




#
# Get local counter data
#

$yk_publicname = $syncParams['yk_publicname'];
$localParams = $sync->getLocalParams($yk_publicname);
if (!$localParams) {
  $myLog->log(LOG_NOTICE, 'Invalid Yubikey ' . $yk_publicname);
  sendResp(S_BACKEND_ERROR, $myLog, $apiKey);
  exit;
 }

/* Conditional update local database */
$sync->updateDbCounters($syncParams);

$myLog->log(LOG_DEBUG, 'Local params ' , $localParams);
$myLog->log(LOG_DEBUG, 'Sync request params ' , $syncParams);

#
# Compare sync and local counters and generate warnings according to
#
# https://github.com/Yubico/yubikey-val/wiki/ServerReplicationProtocol
#



if ($sync->countersHigherThan($localParams, $syncParams)) {
  $myLog->log(LOG_WARNING, 'Remote server out of sync.');
 }


if ($sync->countersEqual($localParams, $syncParams)) {

  if ($syncParams['modified']==$localParams['modified'] &&
      $syncParams['nonce']==$localParams['nonce']) {
    /* This is not an error. When the remote server received an OTP to verify, it would
     * have sent out sync requests immediately. When the required number of responses had
     * been received, the current implementation discards all additional responses (to
     * return the result to the client as soon as possible). If our response sent last
     * time was discarded, we will end up here when the background ykval-queue processes
     * the sync request again.
     */
    $myLog->log(LOG_INFO, 'Sync request unnecessarily sent');
  }

  if ($syncParams['modified']!=$localParams['modified'] &&
      $syncParams['nonce']==$localParams['nonce']) {
    $deltaModified = $syncParams['modified'] - $localParams['modified'];
    if($deltaModified < -1 || $deltaModified > 1) {
      $myLog->log(LOG_WARNING, 'We might have a replay. 2 events at different times have generated the same counters. The time difference is ' . $deltaModified . ' seconds');
    }
  }

  if ($syncParams['nonce']!=$localParams['nonce']) {
    $myLog->log(LOG_WARNING, 'Remote server has received a request to validate an already validated OTP ');
  }
 }

if ($localParams['active'] != 1) {
  /* The remote server has accepted an OTP from a YubiKey which we would not.
   * We still needed to update our counters with the counters from the OTP though.
   */
  $myLog->log(LOG_WARNING, 'Received sync-request for de-activated Yubikey ' . $yk_publicname .
	      ' - check database synchronization!!!');
  sendResp(S_BAD_OTP, $myLog, $apiKey);
  exit;
}

$extra=array('modified'=>$localParams['modified'],
	     'nonce'=>$localParams['nonce'],
	     'yk_publicname'=>$yk_publicname,
	     'yk_counter'=>$localParams['yk_counter'],
	     'yk_use'=>$localParams['yk_use'],
	     'yk_high'=>$localParams['yk_high'],
	     'yk_low'=>$localParams['yk_low']);

sendResp(S_OK, $myLog, $apiKey, $extra);

?>