Fingerprints

Checks of the fields a client sends in initConnection, the tz_offset Telegram Desktop adds, the TL layer and msg ids. The messages are character for character those of the Python package.

validate.mjs


import { generate, issuesMessage, validateInitParams } from 'opentele2'
 
const device = generate('TelegramDesktop', 'account-42', 'windows')
const issues = validateInitParams(device, null, 'strict')
console.log(issues.length === 0 ? 'clean' : issuesMessage(issues))

Validation

index.d.ts


function validateInitParams(profile: ApiProfile, versions?: Versions | null,
  mode?: 'off' | 'warn' | 'strict'): Array<Issue>
function checkVersions(profile: ApiProfile, versions?: Versions | null): Array<Issue>
function issuesMessage(issues: Array<Issue>): string
 
interface Issue {
  kind: 'UnknownLangPack' | 'ShortLangCode' | 'MissingRegion' | 'EmptyDeviceModel'
    | 'EmptySystemVersion' | 'EmptyAppVersion' | 'ApiIdMismatch' | 'AppVersionMajor'
    | 'AndroidSdkRange'
  severity: 'note' | 'warning' | 'error'
  message: string
}

Function	Description
`validateInitParams(profile, versions, mode)`	The findings of `validate_init_connection_params` for `profile`, strict exactly when `mode` is `'strict'` (default `'warn'`); each finding has the severity of `mode`. `versions` overrides the offline versions the strict check compares with.
`checkVersions(profile, versions)`	The version findings alone, each an `'error'`: the app version major of Android, iOS, Telegram Desktop and macOS profiles, and the Android SDK range.
`issuesMessage(issues)`	The message `validate_params` warns or raises with: a header line, then one `-` line per issue.

Severity 'note' is returned only (mode 'off'), 'warning' is warned about ('warn') and 'error' is raised ('strict').

`FingerprintConfig`

index.d.ts


function fingerprintConfig(options?: FingerprintConfigOptions | null): FingerprintConfig
function validateFingerprint(config: FingerprintConfig, profile: ApiProfile, versions?: Versions | null): Array<Issue>
function effectiveLayer(config: FingerprintConfig): number
 
interface FingerprintConfig {
  strictMode: 'off' | 'warn' | 'strict'
  autoValidate: boolean
  preferredTransport: string
  warnOnLayerMismatch: boolean
  layerOverride?: number
  randomizeMsgIdOffset: boolean
  msgIdOffset: number
}
 
interface FingerprintConfigOptions {
  strictMode?: 'off' | 'warn' | 'strict'
  autoValidate?: boolean
  preferredTransport?: string
  warnOnLayerMismatch?: boolean
  layerOverride?: number
  randomizeMsgIdOffset?: boolean
  msgIdOffset?: number
}

Function	Description
`fingerprintConfig(options)`	A config with the defaults (`'warn'`, auto validation, `'obfuscated'`, layer mismatch warnings, no layer override, a randomized offset), each replaced by the option given; without `msgIdOffset` the offset is drawn from the OS random source.
`validateFingerprint(config, profile, versions)`	The issues `validate_params` would surface: none with `autoValidate` off or mode `'off'`, else `validateInitParams` under the configured mode.
`effectiveLayer(config)`	`layerOverride` when set, else `LAYER`. Pass the MTProto library’s layer as the override to match the Python package, which answers with Telethon’s layer.

Layer, time zone and msg ids

index.d.ts


const LAYER: number           // 230
const LAYER_TOLERANCE: number // 15
const MSG_ID_OFFSET_MAX: number
function tzOffset(offsetSeconds: number): number
function msgIdOffset(): number
function isValidMsgId(msgId: bigint | number, fromClient: boolean, nowUnix: number): boolean

Name	Description
`LAYER`	The TL schema layer opentele2 advertises: the layer of the `api.tl` shipped by Telegram Desktop 7.3.1.
`LAYER_TOLERANCE`	The largest distance from `LAYER` the `layer_match` check passes.
`tzOffset(offsetSeconds)`	The `tz_offset` for a local UTC offset: wrapped by whole days into -12 h..+14 h, then rounded to a multiple of 900 seconds, halves away from zero. Pass `-new Date().getTimezoneOffset() * 60` for the local offset.
`msgIdOffset()`	A random msg id offset in `0..=0xFFFF` from the OS CSPRNG.
`MSG_ID_OFFSET_MAX`	The largest offset `msgIdOffset` draws.
`isValidMsgId(msgId, fromClient, nowUnix)`	Whether `msgId` is plausible at `nowUnix`: positive, odd from the client and even otherwise, its upper 32 bits within 300 seconds of `nowUnix`.

initConnectionOptions in opentele2/mtcute turns a profile into the options mtcute sends, with tz_offset for the tdesktop lang pack.