Added telegram bot

src/admin/views.rs

@@ -180,6 +180,21 @@ fn config_display_entries(config: &AppConfig, sources: &ConfigSources) -> Vec<Co
             config.swagger_enabled.to_string(),
             defaults.swagger_enabled.to_string()
         ),
+        entry!(
+            telegram_bot_enabled,
+            config.telegram_bot_enabled.to_string(),
+            defaults.telegram_bot_enabled.to_string()
+        ),
+        entry!(
+            telegram_bot_username,
+            config.telegram_bot_username.clone(),
+            defaults.telegram_bot_username.clone()
+        ),
+        entry!(
+            telegram_bot_token,
+            config.telegram_bot_token.clone(),
+            defaults.telegram_bot_token.clone()
+        ),
     ]
 }
 
@@ -283,6 +298,9 @@ pub struct AdminSettingsRequest {
     vpn_dns: String,
     vpn_mtu: u16,
     swagger_enabled: bool,
+    telegram_bot_enabled: bool,
+    telegram_bot_username: String,
+    telegram_bot_token: String,
 }
 
 #[derive(Debug, Serialize)]
@@ -749,15 +767,90 @@ fn settings_fields(config: &AppConfig, sources: &ConfigSources) -> Vec<AdminSett
             config.swagger_enabled.to_string(),
             defaults.swagger_enabled.to_string()
         ),
+        field!(
+            "telegram",
+            "bool",
+            telegram_bot_enabled,
+            config.telegram_bot_enabled.to_string(),
+            defaults.telegram_bot_enabled.to_string()
+        ),
+        field!(
+            "telegram",
+            "text",
+            telegram_bot_username,
+            config.telegram_bot_username.clone(),
+            defaults.telegram_bot_username.clone()
+        ),
+        field!(
+            "telegram",
+            "password",
+            telegram_bot_token,
+            config.telegram_bot_token.clone(),
+            defaults.telegram_bot_token.clone()
+        ),
+        AdminSettingField {
+            key: "telegram_setup_instructions".into(),
+            env_var: String::new(),
+            value: telegram_setup_instructions(config),
+            default_value: String::new(),
+            source: "default",
+            secret: false,
+            kind: "info",
+            section: "telegram",
+        },
     ]
 }
 
+fn telegram_setup_instructions(config: &AppConfig) -> String {
+    let username = config
+        .telegram_bot_username
+        .trim()
+        .trim_start_matches('@')
+        .trim();
+    let username_value = if username.is_empty() {
+        "<BOT_USERNAME>"
+    } else {
+        username
+    };
+    let token_value = if config.telegram_bot_token.trim().is_empty() {
+        "<BOT_TOKEN>"
+    } else {
+        "<configured bot token>"
+    };
+    let bot_link = if username.is_empty() {
+        "https://t.me/<BOT_USERNAME>".to_owned()
+    } else {
+        format!("https://t.me/{username}")
+    };
+    let current_bot = if username.is_empty() {
+        "<BOT_USERNAME>".to_owned()
+    } else if config.telegram_bot_enabled {
+        format!("@{username}")
+    } else {
+        format!("@{username} (disabled)")
+    };
+
+    format!(
+        "Current bot: {current_bot}\n\
+         Bot link: {bot_link}\n\n\
+         Config:\n\
+         AMNEZIA_FELLOW_TELEGRAM_BOT_ENABLED=true\n\
+         AMNEZIA_FELLOW_TELEGRAM_BOT_USERNAME={username_value}\n\
+         AMNEZIA_FELLOW_TELEGRAM_BOT_TOKEN={token_value}\n\n\
+         BotFather:\n\
+         1. Create or reuse this bot and set the Web App URL to https://<APP_HOST>/configs.\n\
+         2. Make the bot reply with the sender numeric Telegram ID.\n\
+         3. Users must open the bot and send /start once before notifications can work."
+    )
+}
+
 async fn save_settings_request(db: &Database, data: &AdminSettingsRequest) -> cot::Result<()> {
     let vpn_mtu = data.vpn_mtu.to_string();
     let auth_password_enabled = data.auth_password_enabled.to_string();
     let auth_sso_enabled = data.auth_sso_enabled.to_string();
     let swagger_enabled = data.swagger_enabled.to_string();
-    let fields: [(&str, &str); 19] = [
+    let telegram_bot_enabled = data.telegram_bot_enabled.to_string();
+    let fields: [(&str, &str); 22] = [
         ("auth_password_enabled", &auth_password_enabled),
         ("auth_sso_enabled", &auth_sso_enabled),
         ("oidc_button_text", &data.oidc_button_text),
@@ -780,6 +873,9 @@ async fn save_settings_request(db: &Database, data: &AdminSettingsRequest) -> co
         ("vpn_dns", &data.vpn_dns),
         ("vpn_mtu", &vpn_mtu),
         ("swagger_enabled", &swagger_enabled),
+        ("telegram_bot_enabled", &telegram_bot_enabled),
+        ("telegram_bot_username", &data.telegram_bot_username),
+        ("telegram_bot_token", &data.telegram_bot_token),
     ];
     for (key, value) in fields {
         let mut entry = ConfigEntry::new(key.to_owned(), value.to_owned());

src/api/mod.rs

@@ -1,4 +1,5 @@
 use std::collections::HashMap;
+use std::time::Duration;
 
 use cot::db::Database;
 use cot::json::Json;
@@ -15,7 +16,7 @@ use serde::{Deserialize, Serialize};
 
 use crate::config::AppConfig;
 use crate::user::User;
-use crate::{auth, vpn};
+use crate::{auth, telegram, vpn};
 
 // ---------------------------------------------------------------------------
 // JSON error helper
@@ -143,6 +144,33 @@ struct ClientPath {
     id: i64,
 }
 
+#[derive(Debug, Serialize, JsonSchema)]
+struct TelegramLinkStatusResponse {
+    enabled: bool,
+    bot_username: String,
+    bot_url: String,
+    linked: bool,
+    declined: bool,
+    telegram_id: Option<String>,
+}
+
+#[derive(Debug, Serialize, JsonSchema)]
+struct TelegramLinkResponse {
+    status: TelegramLinkStatusResponse,
+}
+
+#[derive(Debug, Deserialize, JsonSchema)]
+struct TelegramWebAppLinkRequest {
+    init_data: String,
+}
+
+#[derive(Debug, Deserialize, JsonSchema)]
+struct TelegramManualLinkRequest {
+    telegram_id: String,
+}
+
+const TELEGRAM_INIT_DATA_MAX_AGE: Duration = Duration::from_secs(86_400);
+
 async fn vpn_clients_handler(
     session: Session,
     db: Database,
@@ -206,6 +234,129 @@ async fn vpn_status_handler(
     Json(status).into_response()
 }
 
+async fn telegram_link_status_handler(
+    session: Session,
+    db: Database,
+) -> cot::Result<cot::response::Response> {
+    let user = match api_user_record(&session, &db).await? {
+        Ok(user) => user,
+        Err(response) => return Ok(response),
+    };
+    let (config, _) = AppConfig::load_with_db(&db).await;
+
+    Json(telegram_status_response(&config, &user)).into_response()
+}
+
+async fn telegram_link_webapp_handler(
+    session: Session,
+    db: Database,
+    Json(request): Json<TelegramWebAppLinkRequest>,
+) -> cot::Result<cot::response::Response> {
+    let mut user = match api_user_record(&session, &db).await? {
+        Ok(user) => user,
+        Err(response) => return Ok(response),
+    };
+    let (config, _) = AppConfig::load_with_db(&db).await;
+    if !config.telegram_bot_enabled {
+        return Ok(json_error_typed(
+            cot::http::StatusCode::CONFLICT,
+            "telegram_disabled",
+            "Telegram is disabled",
+            "Telegram integration is disabled by the administrator.",
+            "",
+        ));
+    }
+
+    let telegram_user = match telegram::validate_web_app_init_data(
+        &request.init_data,
+        &config.telegram_bot_token,
+        TELEGRAM_INIT_DATA_MAX_AGE,
+    ) {
+        Ok(user) => user,
+        Err(e) => {
+            return Ok(json_error_typed(
+                cot::http::StatusCode::BAD_REQUEST,
+                "telegram_webapp_auth_failed",
+                "Telegram verification failed",
+                "Could not verify Telegram Web App data.",
+                &e.to_string(),
+            ));
+        }
+    };
+    let telegram_id = telegram_user.id.to_string();
+    if let Some(response) = link_telegram_id(&db, &mut user, &telegram_id).await? {
+        return Ok(response);
+    }
+
+    Json(TelegramLinkResponse {
+        status: telegram_status_response(&config, &user),
+    })
+    .into_response()
+}
+
+async fn telegram_link_manual_handler(
+    session: Session,
+    db: Database,
+    Json(request): Json<TelegramManualLinkRequest>,
+) -> cot::Result<cot::response::Response> {
+    let mut user = match api_user_record(&session, &db).await? {
+        Ok(user) => user,
+        Err(response) => return Ok(response),
+    };
+    let (config, _) = AppConfig::load_with_db(&db).await;
+    if !config.telegram_bot_enabled {
+        return Ok(json_error_typed(
+            cot::http::StatusCode::CONFLICT,
+            "telegram_disabled",
+            "Telegram is disabled",
+            "Telegram integration is disabled by the administrator.",
+            "",
+        ));
+    }
+
+    let telegram_id = match normalize_manual_telegram_id(&request.telegram_id) {
+        Ok(value) => value,
+        Err(response) => return Ok(response),
+    };
+    if let Some(response) = link_telegram_id(&db, &mut user, &telegram_id).await? {
+        return Ok(response);
+    }
+
+    Json(TelegramLinkResponse {
+        status: telegram_status_response(&config, &user),
+    })
+    .into_response()
+}
+
+async fn telegram_link_decline_handler(
+    session: Session,
+    db: Database,
+) -> cot::Result<cot::response::Response> {
+    let mut user = match api_user_record(&session, &db).await? {
+        Ok(user) => user,
+        Err(response) => return Ok(response),
+    };
+    let (config, _) = AppConfig::load_with_db(&db).await;
+    if !config.telegram_bot_enabled {
+        return Ok(json_error_typed(
+            cot::http::StatusCode::CONFLICT,
+            "telegram_disabled",
+            "Telegram is disabled",
+            "Telegram integration is disabled by the administrator.",
+            "",
+        ));
+    }
+
+    user.set_telegram_id(&db, Some(""))
+        .await
+        .map_err(|e| cot::Error::internal(format!("failed to save Telegram preference: {e}")))?;
+
+    Json(TelegramLinkResponse {
+        status: telegram_status_response(&config, &user),
+    })
+    .into_response()
+}
+
 async fn create_vpn_client_handler(
     session: Session,
     db: Database,
@@ -446,6 +597,101 @@ fn client_view_with_owner(
     view
 }
 
+async fn api_user_record(
+    session: &Session,
+    db: &Database,
+) -> cot::Result<Result<User, cot::response::Response>> {
+    let Some(auth_user) = auth::get_session_user(session, db).await else {
+        return Ok(Err(json_error(
+            cot::http::StatusCode::UNAUTHORIZED,
+            "not authenticated",
+        )));
+    };
+    let Some(user) = User::get_by_id(db, auth_user.id)
+        .await
+        .map_err(|e| cot::Error::internal(format!("failed to load user: {e}")))?
+    else {
+        return Ok(Err(json_error(
+            cot::http::StatusCode::UNAUTHORIZED,
+            "not authenticated",
+        )));
+    };
+    Ok(Ok(user))
+}
+
+fn telegram_status_response(config: &AppConfig, user: &User) -> TelegramLinkStatusResponse {
+    let bot_username = normalized_telegram_bot_username(&config.telegram_bot_username);
+    let telegram_id = user.telegram_id().map(str::to_owned);
+    let linked = telegram_id
+        .as_deref()
+        .is_some_and(|value| !value.is_empty());
+    let declined = telegram_id.as_deref() == Some("");
+
+    TelegramLinkStatusResponse {
+        enabled: config.telegram_bot_enabled,
+        bot_url: telegram_bot_url(&bot_username),
+        bot_username,
+        linked,
+        declined,
+        telegram_id: linked.then_some(telegram_id).flatten(),
+    }
+}
+
+fn normalized_telegram_bot_username(username: &str) -> String {
+    username.trim().trim_start_matches('@').trim().to_owned()
+}
+
+fn telegram_bot_url(username: &str) -> String {
+    if username.is_empty() {
+        String::new()
+    } else {
+        format!("https://t.me/{username}")
+    }
+}
+
+fn normalize_manual_telegram_id(telegram_id: &str) -> Result<String, cot::response::Response> {
+    let telegram_id = telegram_id.trim();
+    if telegram_id.is_empty()
+        || telegram_id.len() > 32
+        || !telegram_id.bytes().all(|byte| byte.is_ascii_digit())
+    {
+        return Err(json_error_typed(
+            cot::http::StatusCode::BAD_REQUEST,
+            "telegram_id_invalid",
+            "Telegram ID is invalid",
+            "Paste the numeric Telegram ID returned by the bot.",
+            "",
+        ));
+    }
+    Ok(telegram_id.to_owned())
+}
+
+async fn link_telegram_id(
+    db: &Database,
+    user: &mut User,
+    telegram_id: &str,
+) -> cot::Result<Option<cot::response::Response>> {
+    if let Some(existing) = User::get_by_telegram_id(db, telegram_id)
+        .await
+        .map_err(|e| cot::Error::internal(format!("failed to check Telegram ID: {e}")))?
+    {
+        if existing.id_val() != user.id_val() {
+            return Ok(Some(json_error_typed(
+                cot::http::StatusCode::CONFLICT,
+                "telegram_id_taken",
+                "Telegram ID is already linked",
+                "This Telegram ID is already connected to another account.",
+                "",
+            )));
+        }
+    }
+
+    user.set_telegram_id(db, Some(telegram_id))
+        .await
+        .map_err(|e| cot::Error::internal(format!("failed to save Telegram ID: {e}")))?;
+    Ok(None)
+}
+
 async fn sync_after_client_mutation(
     db: &Database,
     config: &AppConfig,
@@ -541,6 +787,26 @@ impl App for ApiApp {
                 api_get(vpn_status_handler),
                 "api_vpn_status",
             ),
+            Route::with_api_handler_and_name(
+                "/telegram-link/status",
+                api_get(telegram_link_status_handler),
+                "api_telegram_link_status",
+            ),
+            Route::with_api_handler_and_name(
+                "/telegram-link/webapp",
+                api_post(telegram_link_webapp_handler),
+                "api_telegram_link_webapp",
+            ),
+            Route::with_api_handler_and_name(
+                "/telegram-link/manual",
+                api_post(telegram_link_manual_handler),
+                "api_telegram_link_manual",
+            ),
+            Route::with_api_handler_and_name(
+                "/telegram-link/decline",
+                api_post(telegram_link_decline_handler),
+                "api_telegram_link_decline",
+            ),
             Route::with_api_handler_and_name(
                 "/vpn-clients/sync",
                 api_post(sync_vpn_clients_handler),

src/config.rs

@@ -107,6 +107,9 @@ pub struct ConfigSources {
     pub vpn_dns: ConfigSource,
     pub vpn_mtu: ConfigSource,
     pub swagger_enabled: ConfigSource,
+    pub telegram_bot_enabled: ConfigSource,
+    pub telegram_bot_username: ConfigSource,
+    pub telegram_bot_token: ConfigSource,
 }
 
 impl Default for ConfigSources {
@@ -133,6 +136,9 @@ impl Default for ConfigSources {
             vpn_dns: ConfigSource::Default,
             vpn_mtu: ConfigSource::Default,
             swagger_enabled: ConfigSource::Default,
+            telegram_bot_enabled: ConfigSource::Default,
+            telegram_bot_username: ConfigSource::Default,
+            telegram_bot_token: ConfigSource::Default,
         }
     }
 }
@@ -230,6 +236,12 @@ pub struct AppConfig {
     pub vpn_mtu: u16,
     /// Whether the Swagger UI is served at /swagger/.
     pub swagger_enabled: bool,
+    /// Whether Telegram bot/Web App integration is enabled.
+    pub telegram_bot_enabled: bool,
+    /// Public bot username, without or with the leading @.
+    pub telegram_bot_username: String,
+    /// Bot token used to verify Telegram Web App initData.
+    pub telegram_bot_token: String,
 }
 
 impl Default for AppConfig {
@@ -256,6 +268,9 @@ impl Default for AppConfig {
             vpn_dns: "1.1.1.1, 8.8.8.8".into(),
             vpn_mtu: 1376,
             swagger_enabled: false,
+            telegram_bot_enabled: false,
+            telegram_bot_username: String::new(),
+            telegram_bot_token: String::new(),
         }
     }
 }
@@ -282,6 +297,9 @@ impl_env_overrides!(
     vpn_dns,
     vpn_mtu,
     swagger_enabled,
+    telegram_bot_enabled,
+    telegram_bot_username,
+    telegram_bot_token,
 );
 
 impl AppConfig {
@@ -357,6 +375,9 @@ impl AppConfig {
         apply_db_field!(vpn_dns);
         apply_db_field!(vpn_mtu);
         apply_db_field!(swagger_enabled);
+        apply_db_field!(telegram_bot_enabled);
+        apply_db_field!(telegram_bot_username);
+        apply_db_field!(telegram_bot_token);
     }
 }
 

src/i18n/phrases.rs

@@ -61,6 +61,11 @@ translations! {
     // Kubernetes / VPN settings
     settings_kubernetes:     "Kubernetes"                    , "Kubernetes";
     settings_vpn:            "VPN"                           , "VPN";
+    settings_telegram:       "Telegram"                      , "Telegram";
+    settings_telegram_enabled: "Telegram bot enabled"         , "Telegram-бот включён";
+    settings_telegram_username: "Bot username"                , "Username бота";
+    settings_telegram_token:  "Bot token"                     , "Токен бота";
+    settings_telegram_setup_instructions: "Bot setup guide"   , "Инструкция настройки бота";
 
     // User management
     nav_users:                "Users"                       , "Пользователи";
@@ -155,6 +160,22 @@ translations! {
     notice_server_list_error_title: "Server list unavailable" , "Список серверов недоступен";
     notice_server_list_error_message: "Could not load VPN servers." , "Не удалось загрузить VPN-серверы.";
     notice_detail:           "Detail"                      , "Детали";
+    telegram_link_title:      "Connect Telegram"             , "Подключить Telegram";
+    telegram_webapp_message:  "Save this Telegram account for VPN notifications and bot control." , "Сохранить этот Telegram-аккаунт для уведомлений и управления через бота.";
+    telegram_manual_message:  "You can connect Telegram once and manage VPN keys from the bot." , "Можно один раз подключить Telegram и управлять VPN-ключами через бота.";
+    telegram_connect:         "Connect"                     , "Подключить";
+    telegram_skip:            "Do not ask again"            , "Больше не предлагать";
+    telegram_guide_title:     "How to get your Telegram ID" , "Как узнать Telegram ID";
+    telegram_open_bot:        "Open bot"                    , "Открыть бота";
+    telegram_guide_start:     "Open the bot and send /start once." , "Откройте бота и один раз отправьте /start.";
+    telegram_guide_get_id:    "Ask the bot for your ID; it will reply with only the number." , "Напишите боту, он ответит только номером вашего ID.";
+    telegram_guide_paste:     "Paste that number here and save it." , "Вставьте этот номер сюда и сохраните.";
+    telegram_id_label:        "Telegram ID"                 , "Telegram ID";
+    telegram_id_placeholder:  "Only digits"                 , "Только цифры";
+    telegram_save:            "Save Telegram"               , "Сохранить Telegram";
+    telegram_saved:           "Telegram connected."         , "Telegram подключён.";
+    telegram_declined:        "Telegram prompt disabled."   , "Предложение Telegram отключено.";
+    telegram_bot_unconfigured: "bot is not configured"      , "бот не настроен";
 
     // VPN server management
     servers_empty:            "No registered servers."      , "Нет зарегистрированных серверов.";

src/main.rs

@@ -4,6 +4,7 @@ mod auth;
 mod config;
 mod i18n;
 mod oidc;
+mod telegram;
 mod user;
 mod vpn;
 
@@ -319,6 +320,11 @@ impl Project for AmneziaFellowProject {
                 "  API:\n",
                 "    AMNEZIA_FELLOW_SWAGGER_ENABLED   Enable Swagger UI at /swagger/ (default: false)\n",
                 "\n",
+                "  Telegram:\n",
+                "    AMNEZIA_FELLOW_TELEGRAM_BOT_ENABLED   Enable Telegram bot/Web App integration (default: false)\n",
+                "    AMNEZIA_FELLOW_TELEGRAM_BOT_USERNAME  Telegram bot username, with or without @\n",
+                "    AMNEZIA_FELLOW_TELEGRAM_BOT_TOKEN     Telegram bot token for Web App initData verification\n",
+                "\n",
                 "QUICK START\n",
                 "  export AMNEZIA_FELLOW_DATABASE_URL=sqlite://amnezia-fellow.sqlite3?mode=rwc\n",
                 "  amnezia-fellow --listen 127.0.0.1:8000",

src/telegram.rs

@@ -0,0 +1,212 @@
+use std::time::{Duration, SystemTime, UNIX_EPOCH};
+
+use hmac::{Hmac, Mac};
+use serde::Deserialize;
+use sha2::Sha256;
+use url::form_urlencoded;
+
+type HmacSha256 = Hmac<Sha256>;
+
+#[derive(Debug, Clone, Deserialize, PartialEq, Eq)]
+pub struct TelegramWebAppUser {
+    pub id: i64,
+    pub username: Option<String>,
+    pub first_name: Option<String>,
+    pub last_name: Option<String>,
+}
+
+#[derive(Debug, Clone, PartialEq, Eq)]
+pub enum TelegramAuthError {
+    MissingHash,
+    MissingAuthDate,
+    MissingUser,
+    InvalidHash,
+    InvalidSignature,
+    InvalidAuthDate,
+    Expired,
+    FromFuture,
+    InvalidUser,
+    EmptyBotToken,
+}
+
+impl std::fmt::Display for TelegramAuthError {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        let message = match self {
+            Self::MissingHash => "Telegram initData is missing hash",
+            Self::MissingAuthDate => "Telegram initData is missing auth_date",
+            Self::MissingUser => "Telegram initData is missing user",
+            Self::InvalidHash => "Telegram initData hash is invalid",
+            Self::InvalidSignature => "Telegram initData signature does not match bot token",
+            Self::InvalidAuthDate => "Telegram initData auth_date is invalid",
+            Self::Expired => "Telegram initData is too old",
+            Self::FromFuture => "Telegram initData auth_date is in the future",
+            Self::InvalidUser => "Telegram initData user payload is invalid",
+            Self::EmptyBotToken => "Telegram bot token is not configured",
+        };
+        f.write_str(message)
+    }
+}
+
+impl std::error::Error for TelegramAuthError {}
+
+pub fn validate_web_app_init_data(
+    init_data: &str,
+    bot_token: &str,
+    max_age: Duration,
+) -> Result<TelegramWebAppUser, TelegramAuthError> {
+    let now = SystemTime::now()
+        .duration_since(UNIX_EPOCH)
+        .map_err(|_| TelegramAuthError::InvalidAuthDate)?
+        .as_secs();
+    validate_web_app_init_data_at(init_data, bot_token, max_age, now)
+}
+
+fn validate_web_app_init_data_at(
+    init_data: &str,
+    bot_token: &str,
+    max_age: Duration,
+    now: u64,
+) -> Result<TelegramWebAppUser, TelegramAuthError> {
+    if bot_token.trim().is_empty() {
+        return Err(TelegramAuthError::EmptyBotToken);
+    }
+
+    let mut params = form_urlencoded::parse(init_data.as_bytes())
+        .into_owned()
+        .collect::<Vec<_>>();
+    let hash = params
+        .iter()
+        .find_map(|(key, value)| (key == "hash").then_some(value.as_str()))
+        .ok_or(TelegramAuthError::MissingHash)?;
+    let expected_hash = hex::decode(hash).map_err(|_| TelegramAuthError::InvalidHash)?;
+
+    params.retain(|(key, _)| key != "hash");
+    params.sort_by(|left, right| left.0.cmp(&right.0));
+    let data_check_string = params
+        .iter()
+        .map(|(key, value)| format!("{key}={value}"))
+        .collect::<Vec<_>>()
+        .join("\n");
+
+    verify_signature(bot_token, &data_check_string, &expected_hash)?;
+
+    let auth_date = params
+        .iter()
+        .find_map(|(key, value)| (key == "auth_date").then_some(value.as_str()))
+        .ok_or(TelegramAuthError::MissingAuthDate)?
+        .parse::<u64>()
+        .map_err(|_| TelegramAuthError::InvalidAuthDate)?;
+    if auth_date > now.saturating_add(300) {
+        return Err(TelegramAuthError::FromFuture);
+    }
+    if now.saturating_sub(auth_date) > max_age.as_secs() {
+        return Err(TelegramAuthError::Expired);
+    }
+
+    let user_json = params
+        .iter()
+        .find_map(|(key, value)| (key == "user").then_some(value.as_str()))
+        .ok_or(TelegramAuthError::MissingUser)?;
+    serde_json::from_str(user_json).map_err(|_| TelegramAuthError::InvalidUser)
+}
+
+fn verify_signature(
+    bot_token: &str,
+    data_check_string: &str,
+    expected_hash: &[u8],
+) -> Result<(), TelegramAuthError> {
+    let mut secret_mac =
+        HmacSha256::new_from_slice(b"WebAppData").expect("HMAC accepts any key length");
+    secret_mac.update(bot_token.as_bytes());
+    let secret_key = secret_mac.finalize().into_bytes();
+
+    let mut data_mac =
+        HmacSha256::new_from_slice(&secret_key).expect("HMAC accepts any key length");
+    data_mac.update(data_check_string.as_bytes());
+    data_mac
+        .verify_slice(expected_hash)
+        .map_err(|_| TelegramAuthError::InvalidSignature)
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    fn signed_init_data(bot_token: &str, auth_date: u64, user_json: &str) -> String {
+        let data_check_string =
+            format!("auth_date={auth_date}\nquery_id=AAEAAAE\nuser={user_json}");
+
+        let mut secret_mac =
+            HmacSha256::new_from_slice(b"WebAppData").expect("HMAC accepts any key length");
+        secret_mac.update(bot_token.as_bytes());
+        let secret_key = secret_mac.finalize().into_bytes();
+
+        let mut data_mac =
+            HmacSha256::new_from_slice(&secret_key).expect("HMAC accepts any key length");
+        data_mac.update(data_check_string.as_bytes());
+        let hash = hex::encode(data_mac.finalize().into_bytes());
+
+        let mut serializer = form_urlencoded::Serializer::new(String::new());
+        serializer.append_pair("query_id", "AAEAAAE");
+        serializer.append_pair("user", user_json);
+        serializer.append_pair("auth_date", &auth_date.to_string());
+        serializer.append_pair("hash", &hash);
+        serializer.finish()
+    }
+
+    #[test]
+    fn validates_signed_web_app_init_data() {
+        let token = "123456:fake-token";
+        let init_data = signed_init_data(
+            token,
+            1_700_000_000,
+            r#"{"id":42,"first_name":"Alice","username":"alice"}"#,
+        );
+
+        let user = validate_web_app_init_data_at(
+            &init_data,
+            token,
+            Duration::from_secs(86_400),
+            1_700_000_001,
+        )
+        .unwrap();
+
+        assert_eq!(user.id, 42);
+        assert_eq!(user.username.as_deref(), Some("alice"));
+    }
+
+    #[test]
+    fn rejects_wrong_bot_token() {
+        let init_data = signed_init_data(
+            "123456:fake-token",
+            1_700_000_000,
+            r#"{"id":42,"first_name":"Alice"}"#,
+        );
+
+        let err = validate_web_app_init_data_at(
+            &init_data,
+            "123456:other-token",
+            Duration::from_secs(86_400),
+            1_700_000_001,
+        )
+        .unwrap_err();
+
+        assert_eq!(err, TelegramAuthError::InvalidSignature);
+    }
+
+    #[test]
+    fn rejects_expired_init_data() {
+        let token = "123456:fake-token";
+        let init_data = signed_init_data(token, 1_700_000_000, r#"{"id":42}"#);
+
+        let err = validate_web_app_init_data_at(
+            &init_data,
+            token,
+            Duration::from_secs(60),
+            1_700_000_061,
+        )
+        .unwrap_err();
+
+        assert_eq!(err, TelegramAuthError::Expired);
+    }
+}

src/user.rs

@@ -17,6 +17,7 @@ pub struct User {
     email: Option<String>,
     display_name: Option<String>,
     avatar_url: Option<String>,
+    telegram_id: Option<String>,
     role: LimitedString<32>,
     is_active: bool,
 }
@@ -53,6 +54,7 @@ impl User {
             email: email.map(str::to_owned),
             display_name: display_name.map(str::to_owned),
             avatar_url: None,
+            telegram_id: None,
             role: LimitedString::new(role).unwrap(),
             is_active: true,
         };
@@ -75,6 +77,7 @@ impl User {
             email: email.map(str::to_owned),
             display_name: display_name.map(str::to_owned),
             avatar_url: None,
+            telegram_id: None,
             role: LimitedString::new(role).unwrap(),
             is_active: true,
         };
@@ -117,6 +120,21 @@ impl User {
         cot::db::query!(User, $email == Some(email)).get(db).await
     }
 
+    /// Find a user linked to a non-empty Telegram ID.
+    pub async fn get_by_telegram_id(
+        db: &Database,
+        telegram_id: &str,
+    ) -> cot::db::Result<Option<Self>> {
+        let telegram_id = telegram_id.trim();
+        if telegram_id.is_empty() {
+            return Ok(None);
+        }
+        let telegram_id = telegram_id.to_owned();
+        cot::db::query!(User, $telegram_id == Some(telegram_id))
+            .get(db)
+            .await
+    }
+
     /// Count all users in the database.
     pub async fn count_all(db: &Database) -> cot::db::Result<u64> {
         Self::objects().count(db).await
@@ -140,6 +158,16 @@ impl User {
         self.save(db).await
     }
 
+    /// Store a Telegram link state. `Some("")` means the user declined linking.
+    pub async fn set_telegram_id(
+        &mut self,
+        db: &Database,
+        telegram_id: Option<&str>,
+    ) -> cot::db::Result<()> {
+        self.telegram_id = telegram_id.map(str::to_owned);
+        self.save(db).await
+    }
+
     /// Delete this user by primary key.
     pub async fn delete_by_id(db: &Database, user_id: i64) -> cot::db::Result<()> {
         cot::db::query!(User, $id == Auto::Fixed(user_id))
@@ -165,6 +193,10 @@ impl User {
         self.display_name.clone().unwrap_or_default()
     }
 
+    pub fn telegram_id(&self) -> Option<&str> {
+        self.telegram_id.as_deref()
+    }
+
     pub fn role_str(&self) -> &str {
         &self.role
     }
@@ -391,9 +423,41 @@ pub mod db_migrations {
             &[Operation::custom(create_oidc_link_indexes).build()];
     }
 
+    // -- M0007: Telegram link state on amnezia_fellow__user ----------------
+
+    #[cot::db::migrations::migration_op]
+    async fn add_user_telegram_id(ctx: migrations::MigrationContext<'_>) -> cot::db::Result<()> {
+        ctx.db
+            .raw("ALTER TABLE amnezia_fellow__user ADD COLUMN telegram_id TEXT")
+            .await?;
+        ctx.db
+            .raw(
+                "CREATE UNIQUE INDEX idx_amnezia_fellow_user_telegram_id \
+                     ON amnezia_fellow__user (telegram_id) \
+                     WHERE telegram_id IS NOT NULL AND telegram_id != ''",
+            )
+            .await?;
+        Ok(())
+    }
+
+    #[derive(Debug, Copy, Clone)]
+    pub struct M0007UserTelegramId;
+
+    impl migrations::Migration for M0007UserTelegramId {
+        const APP_NAME: &'static str = "amnezia_fellow";
+        const MIGRATION_NAME: &'static str = "m_0007_user_telegram_id";
+        const DEPENDENCIES: &'static [migrations::MigrationDependency] =
+            &[migrations::MigrationDependency::migration(
+                "amnezia_fellow",
+                "m_0004_oidc_link_indexes",
+            )];
+        const OPERATIONS: &'static [Operation] = &[Operation::custom(add_user_telegram_id).build()];
+    }
+
     pub const MIGRATIONS: &[&SyncDynMigration] = &[
         &M0002CreateUser,
         &M0003CreateOidcLink,
         &M0004OidcLinkIndexes,
+        &M0007UserTelegramId,
     ];
 }