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<?php
/*
ZeroBin - a zero-knowledge paste bin
Please see project page: http://sebsauvage.net/wiki/doku.php?id=php:zerobin
*/
$VERSION='Alpha 0.19';
if (version_compare(PHP_VERSION, '5.2.6') < 0) die('ZeroBin requires php 5.2.6 or above to work. Sorry.');
require_once "lib/serversalt.php";
require_once "lib/vizhash_gd_zero.php";
// In case stupid admin has left magic_quotes enabled in php.ini:
if (get_magic_quotes_gpc())
{
function stripslashes_deep($value) { $value = is_array($value) ? array_map('stripslashes_deep', $value) : stripslashes($value); return $value; }
$_POST = array_map('stripslashes_deep', $_POST);
$_GET = array_map('stripslashes_deep', $_GET);
$_COOKIE = array_map('stripslashes_deep', $_COOKIE);
}
// trafic_limiter : Make sure the IP address makes at most 1 request every 10 seconds.
// Will return false if IP address made a call less than 10 seconds ago.
function trafic_limiter_canPass($ip)
{
$tfilename='./data/trafic_limiter.php';
if (!is_file($tfilename))
{
file_put_contents($tfilename,"<?php\n\$GLOBALS['trafic_limiter']=array();\n?>", LOCK_EX);
chmod($tfilename,0705);
}
require $tfilename;
$tl=$GLOBALS['trafic_limiter'];
if (!empty($tl[$ip]) && ($tl[$ip]+10>=time()))
{
return false;
// FIXME: purge file of expired IPs to keep it small
}
$tl[$ip]=time();
file_put_contents($tfilename, "<?php\n\$GLOBALS['trafic_limiter']=".var_export($tl,true).";\n?>", LOCK_EX);
return true;
}
// Constant time string comparison.
// (Used to deter time attacks on hmac checking. See section 2.7 of https://defuse.ca/audits/zerobin.htm)
function slow_equals($a, $b)
{
$diff = strlen($a) ^ strlen($b);
for($i = 0; $i < strlen($a) && $i < strlen($b); $i++)
{
$diff |= ord($a[$i]) ^ ord($b[$i]);
}
return $diff === 0;
}
/* Convert paste id to storage path.
The idea is to creates subdirectories in order to limit the number of files per directory.
(A high number of files in a single directory can slow things down.)
eg. "f468483c313401e8" will be stored in "data/f4/68/f468483c313401e8"
High-trafic websites may want to deepen the directory structure (like Squid does).
eg. input 'e3570978f9e4aa90' --> output 'data/e3/57/'
*/
function dataid2path($dataid)
{
return 'data/'.substr($dataid,0,2).'/'.substr($dataid,2,2).'/';
}
/* Convert paste id to discussion storage path.
eg. 'e3570978f9e4aa90' --> 'data/e3/57/e3570978f9e4aa90.discussion/'
*/
function dataid2discussionpath($dataid)
{
return dataid2path($dataid).$dataid.'.discussion/';
}
// Checks if a json string is a proper SJCL encrypted message.
// False if format is incorrect.
function validSJCL($jsonstring)
{
$accepted_keys=array('iv','v','iter','ks','ts','mode','adata','cipher','salt','ct');
// Make sure content is valid json
$decoded = json_decode($jsonstring);
if ($decoded==null) return false;
$decoded = (array)$decoded;
// Make sure required fields are present
foreach($accepted_keys as $k)
{
if (!array_key_exists($k,$decoded)) { return false; }
}
// Make sure some fields are base64 data
if (base64_decode($decoded['iv'],$strict=true)==null) { return false; }
if (base64_decode($decoded['salt'],$strict=true)==null) { return false; }
if (base64_decode($decoded['cipher'],$strict=true)==null) { return false; }
// Make sure no additionnal keys were added.
if (count(array_intersect(array_keys($decoded),$accepted_keys))!=10) { return false; }
// Reject data if entropy is too low
$ct = base64_decode($decoded['ct'], $strict=true);
if (strlen($ct) > strlen(gzdeflate($ct))) return false;
// Make sure some fields have a reasonable size.
if (strlen($decoded['iv'])>24) return false;
if (strlen($decoded['salt'])>14) return false;
return true;
}
// Delete a paste and its discussion.
// Input: $pasteid : the paste identifier.
function deletePaste($pasteid)
{
// Delete the paste itself
unlink(dataid2path($pasteid).$pasteid);
// Delete discussion if it exists.
$discdir = dataid2discussionpath($pasteid);
if (is_dir($discdir))
{
// Delete all files in discussion directory
$dhandle = opendir($discdir);
while (false !== ($filename = readdir($dhandle)))
{
if (is_file($discdir.$filename)) unlink($discdir.$filename);
}
closedir($dhandle);
// Delete the discussion directory.
rmdir($discdir);
}
}
if (!empty($_POST['data'])) // Create new paste/comment
{
/* POST contains:
data (mandatory) = json encoded SJCL encrypted text (containing keys: iv,salt,ct)
All optional data will go to meta information:
expire (optional) = expiration delay (never,5min,10min,1hour,1day,1week,1month,1year,burn) (default:never)
opendiscusssion (optional) = is the discussion allowed on this paste ? (0/1) (default:0)
syntaxcoloring (optional) = should this paste use syntax coloring when displaying.
nickname (optional) = son encoded SJCL encrypted text nickname of author of comment (containing keys: iv,salt,ct)
parentid (optional) = in discussion, which comment this comment replies to.
pasteid (optional) = in discussion, which paste this comment belongs to.
*/
header('Content-type: application/json');
$error = false;
// Create storage directory if it does not exist.
if (!is_dir('data'))
{
mkdir('data',0705);
file_put_contents('data/.htaccess',"Allow from none\nDeny from all\n", LOCK_EX);
}
// Make sure last paste from the IP address was more than 10 seconds ago.
if (!trafic_limiter_canPass($_SERVER['REMOTE_ADDR']))
{ echo json_encode(array('status'=>1,'message'=>'Please wait 10 seconds between each post.')); exit; }
// Make sure content is not too big.
$data = $_POST['data'];
if (strlen($data)>2000000)
{ echo json_encode(array('status'=>1,'message'=>'Paste is limited to 2 Mb of encrypted data.')); exit; }
// Make sure format is correct.
if (!validSJCL($data))
{ echo json_encode(array('status'=>1,'message'=>'Invalid data.')); exit; }
// Read additional meta-information.
$meta=array();
// Read expiration date
if (!empty($_POST['expire']))
{
$expire=$_POST['expire'];
if ($expire=='5min') $meta['expire_date']=time()+5*60;
elseif ($expire=='10min') $meta['expire_date']=time()+10*60;
elseif ($expire=='1hour') $meta['expire_date']=time()+60*60;
elseif ($expire=='1day') $meta['expire_date']=time()+24*60*60;
elseif ($expire=='1week') $meta['expire_date']=time()+7*24*60*60;
elseif ($expire=='1month') $meta['expire_date']=time()+30*24*60*60; // Well this is not *exactly* one month, it's 30 days.
elseif ($expire=='1year') $meta['expire_date']=time()+365*24*60*60;
}
// Destroy the paste when it is read.
if (!empty($_POST['burnafterreading']))
{
$burnafterreading = $_POST['burnafterreading'];
if ($burnafterreading!='0' && $burnafterreading!='1') { $error=true; }
if ($burnafterreading!='0') { $meta['burnafterreading']=true; }
}
// Read open discussion flag
if (!empty($_POST['opendiscussion']))
{
$opendiscussion = $_POST['opendiscussion'];
if ($opendiscussion!='0' && $opendiscussion!='1') { $error=true; }
if ($opendiscussion!='0') { $meta['opendiscussion']=true; }
}
// Should we use syntax coloring when displaying ?
if (!empty($_POST['syntaxcoloring']))
{
$syntaxcoloring = $_POST['syntaxcoloring'];
if ($syntaxcoloring!='0' && $syntaxcoloring!='1') { $error=true; }
if ($syntaxcoloring!='0') { $meta['syntaxcoloring']=true; }
}
// You can't have an open discussion on a "Burn after reading" paste:
if (isset($meta['burnafterreading'])) unset($meta['opendiscussion']);
// Optional nickname for comments
if (!empty($_POST['nickname']))
{
$nick = $_POST['nickname'];
if (!validSJCL($nick))
{
$error=true;
}
else
{
$meta['nickname']=$nick;
// Generation of the anonymous avatar (Vizhash):
// If a nickname is provided, we generate a Vizhash.
// (We assume that if the user did not enter a nickname, he/she wants
// to be anonymous and we will not generate the vizhash.)
$vz = new vizhash16x16();
$pngdata = $vz->generate($_SERVER['REMOTE_ADDR']);
if ($pngdata!='') $meta['vizhash'] = 'data:image/png;base64,'.base64_encode($pngdata);
// Once the avatar is generated, we do not keep the IP address, nor its hash.
}
}
if ($error)
{
echo json_encode(array('status'=>1,'message'=>'Invalid data.'));
exit;
}
// Add post date to meta.
$meta['postdate']=time();
// We just want a small hash to avoid collisions: Half-MD5 (64 bits) will do the trick.
$dataid = substr(hash('md5',$data),0,16);
$is_comment = (!empty($_POST['parentid']) && !empty($_POST['pasteid'])); // Is this post a comment ?
$storage = array('data'=>$data);
if (count($meta)>0) $storage['meta'] = $meta; // Add meta-information only if necessary.
if ($is_comment) // The user posts a comment.
{
$pasteid = $_POST['pasteid'];
$parentid = $_POST['parentid'];
if (!preg_match('/\A[a-f\d]{16}\z/',$pasteid)) { echo json_encode(array('status'=>1,'message'=>'Invalid data.')); exit; }
if (!preg_match('/\A[a-f\d]{16}\z/',$parentid)) { echo json_encode(array('status'=>1,'message'=>'Invalid data.')); exit; }
unset($storage['expire_date']); // Comment do not expire (it's the paste that expires)
unset($storage['opendiscussion']);
unset($storage['syntaxcoloring']);
// Make sure paste exists.
$storagedir = dataid2path($pasteid);
if (!is_file($storagedir.$pasteid)) { echo json_encode(array('status'=>1,'message'=>'Invalid data.')); exit; }
// Make sure the discussion is opened in this paste.
$paste=json_decode(file_get_contents($storagedir.$pasteid));
if (!$paste->meta->opendiscussion) { echo json_encode(array('status'=>1,'message'=>'Invalid data.')); exit; }
$discdir = dataid2discussionpath($pasteid);
$filename = $pasteid.'.'.$dataid.'.'.$parentid;
if (!is_dir($discdir)) mkdir($discdir,$mode=0705,$recursive=true);
if (is_file($discdir.$filename)) // Oups... improbable collision.
{
echo json_encode(array('status'=>1,'message'=>'You are unlucky. Try again.'));
exit;
}
file_put_contents($discdir.$filename,json_encode($storage), LOCK_EX);
echo json_encode(array('status'=>0,'id'=>$dataid)); // 0 = no error
exit;
}
else // a standard paste.
{
$storagedir = dataid2path($dataid);
if (!is_dir($storagedir)) mkdir($storagedir,$mode=0705,$recursive=true);
if (is_file($storagedir.$dataid)) // Oups... improbable collision.
{
echo json_encode(array('status'=>1,'message'=>'You are unlucky. Try again.'));
exit;
}
// New paste
file_put_contents($storagedir.$dataid,json_encode($storage), LOCK_EX);
// Generate the "delete" token.
// The token is the hmac of the pasteid signed with the server salt.
// The paste can be delete by calling http://myserver.com/zerobin/?pasteid=<pasteid>&deletetoken=<deletetoken>
$deletetoken = hash_hmac('sha1', $dataid , getServerSalt());
echo json_encode(array('status'=>0,'id'=>$dataid,'deletetoken'=>$deletetoken)); // 0 = no error
exit;
}
echo json_encode(array('status'=>1,'message'=>'Server error.'));
exit;
}
/* Process a paste deletion request.
Returns an array ('',$ERRORMESSAGE,$STATUS)
*/
function processPasteDelete($pasteid,$deletetoken)
{
if (preg_match('/\A[a-f\d]{16}\z/',$pasteid)) // Is this a valid paste identifier ?
{
$filename = dataid2path($pasteid).$pasteid;
if (!is_file($filename)) // Check that paste exists.
{
return array('','Paste does not exist, has expired or has been deleted.','');
}
}
else
{
return array('','Invalid data','');
}
if (!slow_equals($deletetoken, hash_hmac('sha1', $pasteid , getServerSalt()))) // Make sure token is valid.
{
return array('','Wrong deletion token. Paste was not deleted.','');
}
// Paste exists and deletion token is valid: Delete the paste.
deletePaste($pasteid);
return array('','','Paste was properly deleted.');
}
/* Process a paste fetch request.
Returns an array ($CIPHERDATA,$ERRORMESSAGE,$STATUS)
*/
function processPasteFetch($pasteid)
{
if (preg_match('/\A[a-f\d]{16}\z/',$pasteid)) // Is this a valid paste identifier ?
{
$filename = dataid2path($pasteid).$pasteid;
if (!is_file($filename)) // Check that paste exists.
{
return array('','Paste does not exist, has expired or has been deleted.','');
}
}
else
{
return array('','Invalid data','');
}
// Get the paste itself.
$paste=json_decode(file_get_contents($filename));
// See if paste has expired.
if (isset($paste->meta->expire_date) && $paste->meta->expire_date<time())
{
deletePaste($pasteid); // Delete the paste
return array('','Paste does not exist, has expired or has been deleted.','');
}
// We kindly provide the remaining time before expiration (in seconds)
if (property_exists($paste->meta, 'expire_date')) $paste->meta->remaining_time = $paste->meta->expire_date - time();
$messages = array($paste); // The paste itself is the first in the list of encrypted messages.
// If it's a discussion, get all comments.
if (property_exists($paste->meta, 'opendiscussion') && $paste->meta->opendiscussion)
{
$comments=array();
$datadir = dataid2discussionpath($pasteid);
if (!is_dir($datadir)) mkdir($datadir,$mode=0705,$recursive=true);
$dhandle = opendir($datadir);
while (false !== ($filename = readdir($dhandle)))
{
if (is_file($datadir.$filename))
{
$comment=json_decode(file_get_contents($datadir.$filename));
// Filename is in the form pasteid.commentid.parentid:
// - pasteid is the paste this reply belongs to.
// - commentid is the comment identifier itself.
// - parentid is the comment this comment replies to (It can be pasteid)
$items=explode('.',$filename);
$comment->meta->commentid=$items[1]; // Add some meta information not contained in file.
$comment->meta->parentid=$items[2];
$comments[$comment->meta->postdate]=$comment; // Store in table
}
}
closedir($dhandle);
ksort($comments); // Sort comments by date, oldest first.
$messages = array_merge($messages, $comments);
}
$CIPHERDATA = json_encode($messages);
// If the paste was meant to be read only once, delete it.
if (property_exists($paste->meta, 'burnafterreading') && $paste->meta->burnafterreading) deletePaste($pasteid);
return array($CIPHERDATA,'','');
}
$CIPHERDATA='';
$ERRORMESSAGE='';
$STATUS='';
if (!empty($_GET['deletetoken']) && !empty($_GET['pasteid'])) // Delete an existing paste
{
list ($CIPHERDATA, $ERRORMESSAGE, $STATUS) = processPasteDelete($_GET['pasteid'],$_GET['deletetoken']);
}
else if (!empty($_SERVER['QUERY_STRING'])) // Return an existing paste.
{
list ($CIPHERDATA, $ERRORMESSAGE, $STATUS) = processPasteFetch($_SERVER['QUERY_STRING']);
}
require_once "lib/rain.tpl.class.php";
header('Content-Type: text/html; charset=utf-8');
$page = new RainTPL;
$page->assign('CIPHERDATA',htmlspecialchars($CIPHERDATA,ENT_NOQUOTES)); // We escape it here because ENT_NOQUOTES can't be used in RainTPL templates.
$page->assign('VERSION',$VERSION);
$page->assign('ERRORMESSAGE',$ERRORMESSAGE);
$page->assign('STATUS',$STATUS);
$page->draw('page');
?>
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