Excessive Smilies overloading Servers
 

One of my over-zealous (read: bored) users demonstrated an exploit / flaw in vB earlier this evening that I'd like to share with the rest of you to see if: (a) this has been solved; (b) there is a hack which corrects it; or (c) if any of you have come across the issues and have implemented a fix.

This applies to vBulletin 2.2.6, though I suspect it may apply to all previous versions as well.

Problem: When a user enters nothing but a bunch of smilies in the entire "Message:" field of a post, the server's load rises above 5.00 (much higher at times) while processing the smilies. The post is then not made, and the server executes a cold flush of the system RAM.

I've repeated this test several times, and the results seem fairly consistent. Flood a vBulletin with enough smilies and you can basically take it out of commission.

Possible Solution: Eliminate the use of smilies on the forums in question, or implement an algorithm that limits the number of smilies that a user can enter into the Message field. The question is - how exactly would one eliminate the smilies? Just remove them from the list of smilies in the vBulletin Control Panel?

Thoughts on this anyone?

No one is concerned about this? :p

Kaelon

This is already built in to vB. It's in Posting code allowances in vBulletin Options in the admin cp.

That's incorrect. The vBulletin Posting Code Allowances section only permits limiting how one inserts smilies, not how many smilies one can have in the text. What we need to correct this flaw is a setting that would limit the maximum number of smilies (and run a check before the post is processed).

Maximum images per post/signature
Maximum number of images to allow in posts / signatures. Set this to 0 to have no effect.

this affects also smilies

Interesting. Then there is something wrong with your board. It does limit the number of smilies on my board and any other I've ever seen.

Yep, but that doesn't solve the problem, because the smilies are still processed even before the post is rejected - taking up server resources. We need to figure out a way to pre-determine whether the number of smilies in the submitted text exceeds a certain number, before actually processing the thread and converting smilies into image links. The conversion process is surprisingly very server-intensive.

Kaelon

when you click on send posting it'll be preparsed.
newreply.php:as you can see in functions.php:
this code runs just once for each sending process, so lets say if you have set 20 smilies this lineis executet 20 times when someone sends a reply.
not really server intesive.

after that preparsing it counts the ammount of "<img" segments, and if its to high, the post is refused, it'll never be added to the post table so it wouldn't be added to the thread.

if your board doesn't use that behavor of checking max smilies you must have hacked it and made something wrong

I think hes talking like 1000 smilies in one post and in that case he is correct.

Yes, that's right, PPN.

Basically, my server (which has 2 gigs of RAM, Dual P3's) doesn't even blink when a post has something like 20 or even 100 smilies. But, as I have tested personally, if you get a malicious user to come in and start spamming with a post of thousands of smilies - your server will basically come to a grinding halt.

The worst part about this, is that the post is not even processed after the server-intensive issue - so you can never figure out who it was that did this to you to take disciplinary sanctions against the abusive user.

Kaelon

hmm, but i think you cannot do anything against.

as i said before the str_replace function is executet just 20times/post
but if someone uses the same smilie 1000 times or more often it's the str_replace function which increases the server-time.
so i'd say the problem is php not vb

I have confirmed this myself too... I basicly put 10000 bytes of smiles (ie 5000 smilies) into a new post... It loads for a while and then it just stops loading. Nothing happens...

I even tried letting PHP use up to 75MB of ram, and 120 max execution time.

This board handled it easily, though...
https://vborg.vbsupport.ru/showthrea...threadid=41507

That post WILL most likely bog your browser down for a little while...

Yeah it took a whole 4 seconds to load :(

Here is a fix for you:

edit function.php, find:

Before that add:

You can change 1000 with any numbers your server can handle.. This code will first count the smilie number in the post before attempting to process (replace) them and if the number is too high, it will exit and not let str_replace to run to get the server on its knees. FYI "substr_count" works VERY FAST so you dont need to worry about its performance..

BTW congratulate your "bored" members for me, it was a good catch..

Enjoy.. ;)
Logician

Using Logician's idea, here's what I used:
I didn't want to automatically ban the member or anything, in case it was an honest mistake. And I only used 50, because I have a low max image setting, anyway.

normally then you should use that:
good idea logician :)

Thanks, Logician!

Only problem - I tried using

But even if I inserted one smiley, the error_toomanyimages template would be displayed. When I hardcoded "10" instead of $maximages, everything seemed to work fine.

Thanks again, gang.

Kaelon

oh sorry that was my fault

a few lines above you find this code:
replace it with

where exactly am i looking for this? cause there is no function.php file only admin/functions.php and its not in that file.

i am using vb 2.2.6 btw.

yes admin/functions.php

its line 658 in a unhacked functions.php

oh yeah your right so it is, sorry a find did not find it :( hmmmm.

oops wrong thread

Good job Logician and Xenon. :)

I really need this as we are getting spammed badly. I added the hack but it still posts the message and then You cant get into the thread it just says there was too many images inthe previous post so the thread effectively gets ruined by the spammer as noone can open it.

Is there a way to check before it actually posts the message?

My code above checks the message before it is inserted into the database so it shouldnt behave like you said if you applied the code correctly and used "exit" command as I suggested.

If it's a common problem, the best practise will be changing the spammer's usergroup to banned/ moderated or restricted users inside the code to get rid of them easy and quick.

Don't forget to use "exit" command, otherwise the script will not stop and it will write the post to the database which will cause problems like you mentioned..

hmm, standarderror has included the exit since a few versions pal :)

but i have to agree, banning those users who abuse their rights is the better way :)

I tried the code above but for some reason it posts the message and then brings up the error message. If you try and then go into the thread aferwards it just syays ' you last post had too many blah blah' so I'm not sure why this is not working for us.

ok then there is one possibility left and that is your "Maximum images per post/signature" settings in Admin CP/vb settings is set to 0.

Change it to any value except 0 and the hack will work.. ;)

Glad I stumbled on to this thread. I see the geniuses are hard at work again. :)

What code would I need to warn someone with a PM telling them that they will be banned if it happens again? And can I do it for a particular user if he does it more than once?

You can play with this code:

However one important warning here:
bbcodeparse and bbcodeparse2 functions are called from many parts of vb code, not only when someone posts a message. Therefore if you apply a hack there you have to make sure, the conditional the hack depends will not be TRUE when the function is called from somewhere else in vb code.

Let's discuss on an example:
If you apply send PM hack above in this function and make sure it runs when a post has more than 1000 smilies, the poster who will snd a post with 1000 smilies will receive your PM. But if you don't clear all existing posts with 1000 smilies, someone who accidently visited such a post will also receive this PM because the same function will be called and the condition will prove TRUE in showthread.php too.

Bottom line is: Before applying such hacks into this function, make sure you cleared all existing posts/PMs from your database in the first place. Then you can be sure the hack will only apply to new posters only as it should..

no easy way. You have to form a structure that will track warning of the users..

Thanks, Sinan. :) I'll play around with it and let you know what I come up with.

By this:

do you mean if I have "Moderate posts" turned on? Because I don't.

No.. I mean whatever max.smilie number you specified in this hack, you make sure you don't have existing posts in your database which have that many smilies in them. If any, delete them before applying the hack.

Otherwise the hack code will apply to visitors of these threads too, not only new posters..

oh, ok, that makes a little more sense now. Thank for explaining that to me. :)

By the way, where do I set these variables?

$greeter="enter senders id";
$receiver="enter receivers id";
$title2="PM title";

I ckecked that and it's still doing it. It posts the post and then renders the thread useless.

Hmm my windows server seems to be safe against this our at least at the moment. When i add a ton of smilies im guessing near 1000 or so then it says my script did not return a complete set of headers. But if i go to like 900 then my server just flies to the to many images page in under a second.

Upon checking this, vBulletin 2.30 still shares this vulnerability, so I recommend that users apply this patch promptly.

Kaelon

vBulletin 2.3.2 still, furthermore, still has this vulnerability. I would recommend it be included in vBulletin 3.

Just curious: Have you ever reported it as a bug in vb.com? I think it deserves to be accepted as a "bug" so I think it would be corrected if reported in vb.com.

logician is the man!