60 lines
2.6 KiB
JavaScript
60 lines
2.6 KiB
JavaScript
// @ts-check
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const reg = require("../../matrix/read-registration")
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const userRegex = reg.namespaces.users.map(u => new RegExp(u.regex))
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const assert = require("assert").strict
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/** @type {import("xxhash-wasm").XXHashAPI} */ // @ts-ignore
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let hasher = null
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// @ts-ignore
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require("xxhash-wasm")().then(h => hasher = h)
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/**
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* Determine whether an event is the bridged representation of a discord message.
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* Such messages shouldn't be bridged again.
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* @param {string} sender
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*/
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function eventSenderIsFromDiscord(sender) {
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// If it's from a user in the bridge's namespace, then it originated from discord
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// This includes messages sent by the appservice's bot user, because that is what's used for webhooks
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// TODO: It would be nice if bridge system messages wouldn't trigger this check and could be bridged from matrix to discord, while webhook reflections would remain ignored...
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// TODO that only applies to the above todo: But you'd have to watch out for the /icon command, where the bridge bot would set the room avatar, and that shouldn't be reflected into the room a second time.
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if (userRegex.some(x => sender.match(x))) {
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return true
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}
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return false
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}
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/**
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* @param {string} mxc
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* @returns {string?}
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*/
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function getPublicUrlForMxc(mxc) {
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const avatarURLParts = mxc?.match(/^mxc:\/\/([^/]+)\/(\w+)$/)
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if (avatarURLParts) return `${reg.ooye.server_origin}/_matrix/media/r0/download/${avatarURLParts[1]}/${avatarURLParts[2]}`
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else return null
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}
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/**
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* Event IDs are really big and have more entropy than we need.
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* If we want to store the event ID in the database, we can store a more compact version by hashing it with this.
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* Choosing a 64-bit non-cryptographic hash as only a 32-bit hash will see birthday collisions unreasonably frequently: https://en.wikipedia.org/wiki/Birthday_attack#Mathematics
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* xxhash outputs an unsigned 64-bit integer.
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* Converting to a signed 64-bit integer with no bit loss so that it can be stored in an SQLite integer field as-is: https://www.sqlite.org/fileformat2.html#record_format
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* This should give very efficient storage with sufficient entropy.
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* @param {string} eventID
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*/
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function getEventIDHash(eventID) {
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assert(hasher, "xxhash is not ready yet")
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if (eventID[0] === "$" && eventID.length >= 13) {
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eventID = eventID.slice(1) // increase entropy per character to potentially help xxhash
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}
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const unsignedHash = hasher.h64(eventID)
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const signedHash = unsignedHash - 0x8000000000000000n // shifting down to signed 64-bit range
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return signedHash
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}
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module.exports.eventSenderIsFromDiscord = eventSenderIsFromDiscord
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module.exports.getPublicUrlForMxc = getPublicUrlForMxc
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module.exports.getEventIDHash = getEventIDHash
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