https://youtu.be/H7R7sW4Ne1g

1.19.3 rewrote chat again, this time the security of the system hinges almost entirely on last seen. Previously, context gathering was done by walking the merkle tree formed by the last seens, this allowed adding messages because it would if alice saw a message from bob, and bob has seen a private message from himself to charlie, it would imply that alice has seen that private message. As of 1.19.3, last seen is a list of 20 signatures, which is the only source for context, this means you can't add messages by implying they've been seen. The new system has a similar flaw to the last attempt in that messages can be removed as long as theres no messages from you that acknowledge them, and from the point of view of a silent reporter, this means every message can be deleted (although it might look weird if 20 people have seen a message you haven't).

Updated detectability challenge hash: 4539885ff33448ae8cb414a4518778e2f1bd69a1bcf2e9656906aef3227ca8411f2c3caf5841687d3e95fe086a7827ed882335b9d58337ed0942024fa160e52e

If you install Gaslight on a server, there are new ways to manipulate context. The attack in the video shows a server that appears to be disabling chat reports via system messages, however clients will still sign chat messages. By sending a message, then immediately sending the delete chat message packet, you can have a client acknowledge a chat message that the user never saw, and because the server is using system messages, the user cannot tell when messages are forged. This leads to a much simpler chat log than client side Gaslight, simply "are you breaking mojang's tos?" "of course!".

These attacks can still be done on a server that isn't pretending to use system messages, you only lose the ability to send messages completely detached from the chain.

There are three commands added by Gaslight:

• sendsystem - sends a chat message as a system message without signing it
• sendhidden - sends a signed chat message to a specified user, and immediately removes it from the clients screen, however the message is still in last seen
• sendnormal - sends a direct message that looks like a public chat message

Mojang recently tweeted implying that Gaslight is detectable, while it is (currently) detectable in some cases, it is not detectable in all cases, and if you know what you are doing, generating indistinguishable reports is more than doable. We have included 3 example reports, containing all data sent to Mojang (although we redacted the server ip), at least one of them is legitimate, and at least one is produced via Gaslight. Which example is legitimate, which is from Gaslight? We will attach any correct cryptographic proof to the top of this readme, and probably look like idiots.

To prove we aren't changing the answer, the (salted) sha512 hash is 95c4f235fb3a6265f8b9f0114b0a9fd613d33937aea326e314c502f42d7051ebea88faa79e95895d9538171821ea5cbe97727decc7a1085fc56e7f9b069f5e48

0xAda: do you want to pvp

0xAda: /msg [gaslight user] are you breaking tos

0xAda: *?

Gildfesh: of course!

0xAda: /msg [any other user] [any message]

0xAda: are you breaking tos

0xAda: *?

Gildfesh: of course!

https://www.youtube.com/watch?v=ipkFCrbB3Cg

1.19.1-pre4/5 was a patch to the initial version of Gaslight. Not long before their announcement banning all blockchain technologies from the game, Mojang themselves added a blockchain to the chat system, this clusterfuck of a system had us stumped, not because it fixed Gaslight, but because it doesn't make any sense.

Mojang's fix was to add a chat chain system, this is beyond the scope of a youtube/github description, but you can read in depth about it here, but the important part is that it stops you adding messages after the fact. You can't remove messages anymore, because the last seen field would show messages that no longer exist, and you can't add messages because it would invalidate the signatures of messages surrounding it as it would not be included in the last seen field.

The workaround Gaslight uses is private messages. In order to keep the chain consistent for every player, Mojang added a new packet that sends only the signature of a message for any message a player cannot see. Mojang, however, forgot the one thing that got them in this mess in the first place, you can't trust the client. With just the chat chain, how do they know if you actually received a message, or if it was a private message that you couldn't see? Every message you can see on your client will appear to Mojang as if it was sent in public chat.

Utilising private messages also gives us the ability to remove messages. With some exceptions, Mojang has no way of knowing if you received the full message, or just the header, therefore we can remove the body of messages, leaving it as just a header and making it identical to an equivalent private message.

By sending a private message to yourself with the desired context, then sending a message in public chat expecting a particular response, you can have context that is only visible to you and Mojang, and you can "remove" the message you sent in public chat, because Mojang has no way of knowing if you received the full message, or just the header. This is slightly harder to use than the previous iteration of Gaslight, but overall, the functionality is the same.

https://www.youtube.com/watch?v=uyqi-CzB8Dg

1.19.1-rc1 changed how abuse reports were sent to Mojang, context of other messages is now included. Mojang does not verify that these messages were actually sent to the server, or even that the players were on the server at the time. You can modify the request sent to Mojang to fake context around the message, messages can be signed as if they were sent in the past to make innocent messages look malicious, especially if you have keys for multiple accounts.

[12:59] player 1: want to pvp?

[13:00] player 2: of course!

[12:59] player 1: are you breaking mojang's terms of service?

[13:00] player 2: of course!