Description of issue:
This duplication method requires 2 logged in copies of minecraft and preferably an autoreconnect plugin.
- On client #1 prepare the item you wish to duplicate.
- Connect to the server using client #2.
- As the server is about to disconnect you from client #1 drop the item (hit q).
- Reconnect with client #1 and you may have duplicated the item.
Notes:
- Works best on servers that have a low TPS. As an example at 1 TPS duplicating happens virtually every try.
Example Video: https://www.youtube.com/watch?v=zJYmMkhbbGY
You'll note I have 2 items in my hand to begin with, then after disconnect end up with 3.
Plugin list:
DeathMessagesPrime, OldschoolKill, RedstoneClockPreventer, noMe, SimpleAutoBroadcast, NoNetherRoof, DisableJoinMessage, BukkitHiddenSyntaxBlocker, TeaLimit, ChatCo, Random_Spawn, ItemRestrict, ProtocolLib, NoCheatPlus
bukkit.yml, spigot.yml, paper.yml, server.properties
bukkit.yml => http://pastie.org/private/irb2ze7temqydfd1rblkaw
spigot.yml => http://pastie.org/private/rhw1mngrr83azoqyiewaq
paper.yml => http://pastie.org/private/2qpblul1zv94sxx27hqe9g
server.properties => http://pastie.org/private/jryuenrcv30tw0vawmw5q
Paper build number:
924
NerdGuruDevelopers
All 35 comments
Works best on servers that have a low TPS. As an example at 1 TPS duplicating happens virtually every try.
There are a lot of things that go wrong when you have a lot TPS. Try solving that first.
ghost
on 21 Nov 2016
this is a duplicate of #481 and is already fixed
LeafHacker
on 21 Nov 2016
I was able to duplicate this using no plugins with a vanilla client at 10 TPS.
TPS reading: http://nerd.guru/screenshots/javaw_2016-11-20_17-53-28.png
Video Of Duplication: https://www.youtube.com/watch?v=2bXHcqAP09M&edit=vd
@LeafHacker - If it's a duplicate what version was it patched in. I was up to date until like 15 minutes ago and I'm on 924 :P
NerdGuruDevelopers
on 21 Nov 2016
Is this an issue on Spigot, or was this caused by paperspigot in the first place? Would like to know.
cyberpwnn
on 22 Nov 2016
If you're having a hard time reproducing this can I get pointed to the section of code that handles disconnects and player file saving please?
NerdGuruDevelopers
on 24 Nov 2016
Resolving this issue has been proven to be quite a hassle, the provided fix by spigot that would resolve this issue appears to only make it easier.
ghost
on 24 Nov 2016
Interesting. Can you point me toward the section of code you're referencing?
I know nothing about the paper project, but I do program for a living.
NerdGuruDevelopers
on 24 Nov 2016
Dupe still works with paper 933
Same video:
https://www.youtube.com/watch?v=zJYmMkhbbGY
How to reproduce:
- Get WorldEdit (or any means to lower TPS)
- Make a large selection around Y255 (~5 chunks should be more than enough to bring down your TPS)
- //replace air water,lava
- Repeat https://www.youtube.com/watch?v=zJYmMkhbbGY
On client N1 prepare the item you wish to duplicate.
Connect to the server using client N2.
As the server is about to disconnect you from client N1 RAPID CLICK drop button
Reconnect with client N1 and you may have duplicated the item.
guccihub
on 26 Nov 2016
Sounds like this may be related to GH-488
zachbr
on 27 Nov 2016
Zbob750 what makes you think it's related? This doesn't have anything to do with chests. I'd think it'd have more to do with the fact that player save files aren't registering the drop before being loaded up by client #2.
NerdGuruDevelopers
on 27 Nov 2016
Looks like it's been reported here: https://bugs.mojang.com/browse/MC-63 and someone has made a temp patch plugin (untested, use at your own peril): https://github.com/ataranlen/NoDroppingOffline/releases
NerdGuruDevelopers
on 27 Nov 2016
I said it may be related, not that it is.
Chests are containers, player inventories are containers. There's a lot of shared code there.
If someone can verify the linked plugin fixes the issue, that's a pretty simple thing to add as a mitigating step, until someone fixes the root issue.
zachbr
on 27 Nov 2016
Integrating said plugin into paper is a really hacky solution IMO
ghost
on 27 Nov 2016
I'm not thrilled about it either, if you're aware of a better solution feel free to submit a PR @Chnkr
zachbr
on 27 Nov 2016
Can do 馃憤 will look into something tomorrow.
ghost
on 27 Nov 2016
sgdc3
on 27 Nov 2016
Update your servers, Paper now follows most every other game server software out there by not processing packets from players who already disconnected, which should resolve the issue.
zachbr
on 27 Nov 2016
Unfortunately it does not appear patched on version 959. The plugin does not seem to work either. Same exact reproduction procedures.
NerdGuruDevelopers
on 5 Dec 2016
Not re-opening this issue without multiple confirmations from multiple parties.
zachbr
on 5 Dec 2016
I am unable to replicate
KurtisAD
on 5 Dec 2016
Appears to still work- I run a survival anarchy server called 2b2t and am running latest build from git.
rbreslow
on 5 Dec 2016
Confirmed working on 2b2t.net
starcraft66
on 5 Dec 2016
At this point, PRs welcome. I don't have time to look into this any further right now.
zachbr
on 6 Dec 2016
I wrote a plugin to temporarily stop this until someone comes up with a better way.
https://github.com/NerdGuruDevelopers/NoDupe
Confirmed working on 9b9t.
NerdGuruDevelopers
on 6 Dec 2016
@NerdGuruDevelopers that is a terrible way to stop it, because it'll still work with that plugin, the entire dupe relies on the fact that your inventory is serialized too late / too early.
ghost
on 6 Dec 2016
It also relies on users being able to disconnect by users knowing when exactly they'll be kicked. Like I said temporary patch until someone figures out a better way to stop it.
NerdGuruDevelopers
on 6 Dec 2016
No, it does not. There are so much more ways you can execute this duplication glitch, none of the provided patches or plugins resolve the issue, and as of right now it still works in Vanilla, Spigot & Paperspigot.
Mojang knows about it, but it's highly unlikely that this will be patched anytime soon.
ghost
on 6 Dec 2016
I can confirm this issue still persists in 1.11.2 using Paper 992, NoCheatPlus 1046 and ProtocolLib 345. Do we have any progress on a fix? An entire server is duping and I cannot find a way to stop it.
FirstReplay
on 26 Dec 2016
Wurst clients cause an "Interacted with Self" disconnect message that can be caught on a bungeecord level, You can use a ServerKickEvent listener to deal with the offending players, I haven't seen that disconnect message by vanilla means yet. Its not a fool proof solution, but it should at least catch the bad dupers.
NachtRaben
on 26 Dec 2016
This doesn't have anything to do with hacked clients @NachtRaben as it is being done on Vanilla clients by simply following the OPs method. That kick dupe you mention is still fixed AFAIK.
FirstReplay
on 26 Dec 2016
Another "bandaid" for the issue is to simply return on interacting with self instead of kicking, teleport the player to the correct location instead of kicking for flying, and such until players cannot reliably get themselves kicked.
AlfieC
on 26 Dec 2016
I've pulled @AlfieC 's PR. See if this is still possible with build 997+
aikar
on 27 Dec 2016
Both @prplz and I have tested this extensively and have so far been unable to replicate with my PR - but when we revert to the one without the PR, we can get it usually 50% of the time (when we run the server at 1-2tps).
AlfieC
on 27 Dec 2016
going to mark this closed then. Please reopen a new ticket if it can be done again.
aikar
on 2 Jan 2017
Can confirm patch seems to solve it.
NerdGuruDevelopers
on 2 Jan 2017
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Most helpful comment
Update your servers, Paper now follows most every other game server software out there by not processing packets from players who already disconnected, which should resolve the issue.