q13x-eaglerproxy/eaglerSkin.ts

import {
    encodeULEB128 as encodeVarInt,
    decodeULEB128 as decodeVarInt,
    encodeSLEB128 as encodeSVarInt,
    decodeSLEB128 as decodeSVarInt
} from "@thi.ng/leb128"
import { DecodedCFetchSkin, DecodedSSkinDl, DecodedCSkinReq, DecodedSSkinFetchBuiltin, UnpackedChannelMessage, ProxiedPlayer, ChannelMessageType } from "./types.js"
import uuidBuffer from "uuid-buffer"
import { bufferizeUUID } from "./utils.js"
import { EAGLERCRAFT_SKIN_CHANNEL_NAME, EaglerSkinPacketId, MAGIC_ENDING_S_SKINDL_BI } from "./eaglerPacketDef.js"
import sharp from "sharp"
import request from "request"

export function unpackChannelMessage(message: Buffer): UnpackedChannelMessage {
    if (message[0] != 0x17 && message[0] != 0x3f)
        throw new Error("Invalid packet ID detected")
    const ret: UnpackedChannelMessage = {
        channel: null,
        data: null,
        type: null
    }
    const Iid = decodeVarInt(message)
    const channelNameLen = decodeVarInt(message.subarray(Iid[1])), channelName = message.subarray(Iid[1] + channelNameLen[1], Iid[1] + channelNameLen[1] + Number(channelNameLen[0])).toString()
    ret.type = Number(Iid[0])
    ret.channel = channelName
    ret.data = message.subarray(Iid[1] + channelNameLen[1] + channelName.length)
    return ret
}

export function packChannelMessage(channel: string, type: ChannelMessageType, message: Buffer): Buffer {
    const channelNameLen = encodeVarInt(channel.length), buff = Buffer.alloc(1 + channelNameLen.length + channel.length + message.length)
    buff.set([type,...channelNameLen, ...Buffer.from(channel), ...message])
    return buff
}

export function decodeCFetchSkin(message: Buffer): DecodedCFetchSkin {
    const ret: DecodedCFetchSkin = {
        id: null,
        uuid: null
    }
    const Iid = decodeVarInt(message), uuid = uuidBuffer.toString(message.subarray(Iid[1]))
    ret.id = Number(Iid[0])
    ret.uuid = uuid
    return ret
}

export function encodeFetchSkin(uuid: string | Buffer): Buffer {
    uuid = typeof uuid == 'string' ? bufferizeUUID(uuid) : uuid
    const buff = Buffer.alloc(1 + uuid.length)
    buff.set([EaglerSkinPacketId.C_FETCH_SKIN, ...uuid])
    return buff
}

export function decodeSSkinDlBuiltin(message: Buffer): DecodedSSkinFetchBuiltin {
    const ret: DecodedSSkinFetchBuiltin = {
        id: null,
        uuid: null,
        skinId: null
    }
    const Iid = decodeVarInt(message), uuid = uuidBuffer.toString(message.subarray(Iid[1], Iid[1] + 16))
    ret.id = Number(Iid[0])
    ret.uuid = uuid
    const skinId = decodeVarInt(message.subarray(Iid[1] + 16 + 3))
    ret.skinId = Number(skinId)
    return ret
}

export function encodeSSkinDlBuiltin(uuid: string | Buffer, skinId: number): Buffer {
    uuid = typeof uuid == 'string' ? bufferizeUUID(uuid) : uuid
    const encSkinId = encodeVarInt(skinId)
    const buff = Buffer.alloc(1 + 16 + 3 + encSkinId.length)
    buff.set([EaglerSkinPacketId.S_SKIN_DL_BI, ...uuid, ...Buffer.from(MAGIC_ENDING_S_SKINDL_BI), encSkinId[0]])
    return buff
}

export function decodeSSkinDl(message: Buffer): DecodedSSkinDl {
    const ret: DecodedSSkinDl = {
        id: null,
        uuid: null,
        skin: null
    }
    const Iid = decodeVarInt(message), uuid = uuidBuffer.toString(message.subarray(Iid[1], Iid[1] + 16))
    ret.id = Number(Iid[0])
    ret.uuid = uuid
    const skin = message.subarray(Iid[1] + 16)
    ret.skin = skin
    return ret
}

export function encodeSSkinDl(uuid: string | Buffer, skin: Buffer, isFetched: boolean): Buffer {
    uuid = typeof uuid == 'string' ? bufferizeUUID(uuid) : uuid
    // eaglercraft clients always expect a 16385 byte long byte array for the skin
    if (!isFetched) skin = skin.length !== 16384 ? skin.length < 16384 ? Buffer.concat([Buffer.alloc(16384 - skin.length), skin]) : skin.subarray(16383) : skin
    else skin = skin.length !== 16384 ? skin.length < 16384 ? Buffer.concat([skin, Buffer.alloc(16384 - skin.length)]) : skin.subarray(16383) : skin
    const skinLen = encodeVarInt(skin.length), buff = Buffer.alloc(1 + 16 + 1 + skin.length)
    buff.set([EaglerSkinPacketId.S_SKIN_DL, ...uuid, 0xff,...skin])
    return buff
}

export function decodeCSkinReq(message: Buffer): DecodedCSkinReq {
    const ret: DecodedCSkinReq = {
        id: null,
        uuid: null,
        url: null
    }
    const Iid = decodeVarInt(message), uuid = uuidBuffer.toString(message.subarray(Iid[1], Iid[1] + 16))
    ret.id = Number(Iid[0])
    ret.uuid = uuid
    const urlLen = decodeVarInt(message.subarray(Iid[1] + 16 + 1)), url = message.subarray(Iid[1] + 16 + 1 + urlLen[1]).toString()
    ret.url = url
    return ret

}

export function encodeCSkinReq(uuid: string | Buffer, url: string): Buffer {
    uuid = typeof uuid == 'string' ? bufferizeUUID(uuid) : uuid
    const urlLen = encodeVarInt(url.length), eUrl = Buffer.from(url)
    const buff = Buffer.alloc(1 + 1 + 16 + urlLen.length + eUrl.length)
    buff.set([EaglerSkinPacketId.C_REQ_SKIN, ...uuid, 0x00, ...urlLen, ...eUrl])
    return buff
}

// TODO: fix broken custom skins

export async function fetchSkin(url: string): Promise<Buffer> {
    return new Promise<Buffer>((res, rej) => {
        let body = []
        request({ url: url, encoding: null }, (err, response, body) => {
            if (err) {
                rej(err)
            } else {
                sharp(body)
                    .resize(64, 64)
                    .raw({ depth: 'char' })
                    .toBuffer()
                    .then(res)
                    .catch(rej)
            }
        })
    })
}

export function getPlayerWithUUID(uuid: string): ProxiedPlayer {
    for (const [username, plr] of PROXY.players) {
        if (plr.uuid == uuid)
            return plr
    }
    return null
}

export async function processClientReqPacket(decodedMessage: UnpackedChannelMessage, client: ProxiedPlayer) {
    if (decodedMessage.type == ChannelMessageType.SERVER)
        throw new Error("Server message was passed to client message handler")
    switch(decodedMessage.data[0] as EaglerSkinPacketId) {
        default:
            throw new Error("Unknown operation")
            break
        case EaglerSkinPacketId.C_REQ_SKIN:
            const reqSkinPck = decodeCSkinReq(decodedMessage.data)
            if (getPlayerWithUUID(reqSkinPck.uuid)) {
                client.ws.send(packChannelMessage(EAGLERCRAFT_SKIN_CHANNEL_NAME, ChannelMessageType.SERVER, encodeSSkinDl(reqSkinPck.uuid, getPlayerWithUUID(reqSkinPck.uuid).skin.customSkin, false)))
            } else {
                try {
                    const skin = await fetchSkin(reqSkinPck.url)
                    const resPck = encodeSSkinDl(reqSkinPck.uuid, skin, true)
                    client.ws.send(packChannelMessage(EAGLERCRAFT_SKIN_CHANNEL_NAME, ChannelMessageType.SERVER, resPck))
                } catch {}
            }
            break
        case EaglerSkinPacketId.C_FETCH_SKIN:
            const fetchSkinPlrPck = decodeCFetchSkin(decodedMessage.data)
            const plr = getPlayerWithUUID(fetchSkinPlrPck.uuid)
            if (plr) {
                if (plr.skin.type == 'BUILTIN') {
                    client.ws.send(packChannelMessage(EAGLERCRAFT_SKIN_CHANNEL_NAME, ChannelMessageType.SERVER, encodeSSkinDlBuiltin(plr.uuid, plr.skin.skinId)))
                } else {
                    client.ws.send(packChannelMessage(EAGLERCRAFT_SKIN_CHANNEL_NAME, ChannelMessageType.SERVER, encodeSSkinDl(plr.uuid, plr.skin.customSkin, false)))
                }
            }
    }
}