Allow login flow to be more like the official PC client

matrix_appservice_kakaotalk/commands/auth.py

@@ -22,9 +22,17 @@ from mautrix.errors import MForbidden
 #from mautrix.util.signed_token import sign_token
 
 from ..kt.client import Client as KakaoTalkClient
-from ..kt.client.errors import DeviceVerificationRequired, IncorrectPasscode, IncorrectPassword, CommandException
+from ..kt.client.errors import (
+    AnotherLogonDetected,
+    CommandException,
+    DeviceVerificationRequired,
+    IncorrectPasscode,
+    IncorrectPassword,
+)
 
 from .. import puppet as pu
+from ..db import LoginCredential
+
 from .typehint import CommandEvent
 
 SECTION_AUTH = HelpSection("Authentication", 10, "")
@@ -46,28 +54,47 @@ send_password = "Please send your password here to log in"
 missing_email = "Please use `$cmdprefix+sp login <email>` to log in here"
 try_again_or_cancel = "Try again, or say `$cmdprefix+sp cancel` to give up."
 
+_CMD_CONTINUE_LOGIN = "continue-login"
+
 
 @command_handler(
     needs_auth=False,
     management_only=True,
     help_section=SECTION_AUTH,
-    help_text="Log in to KakaoTalk",
-    help_args="[_email_]",
+    help_text="Log in to KakaoTalk. Optionally save login credentials & have the bridge use them when needed to automatically restore your login session.",
+    help_args="[--save] [_email_]",
 )
 async def login(evt: CommandEvent) -> None:
     if await evt.sender.is_logged_in():
         await evt.reply("You're already logged in")
         return
 
-    email = evt.args[0] if len(evt.args) > 0 else None
+    save = len(evt.args) > 0 and evt.args[0] == "--save"
+    email = evt.args[0 if not save else 1] if len(evt.args) > 0 else None
 
     if email:
         evt.sender.command_status = {
             "action": "Login",
             "room_id": evt.room_id,
-            "next": enter_password,
+            "next": _enter_password,
             "email": email,
+            "save": save,
+            "forced": evt.sender.force_login,
         }
+        try:
+            creds = await LoginCredential.get_by_mxid(evt.sender.mxid)
+        except:
+            evt.log.exception("Exception while looking for saved password")
+            creds = None
+        if creds and creds.email == email:
+            await evt.reply("Logging in with saved password")
+            await _login_with_password(
+                evt,
+                evt.sender.command_status.pop("email"),
+                creds.password,
+                evt.sender.command_status.pop("forced"),
+            )
+            return
 
     """ TODO Implement web login
     if evt.bridge.public_website:
@@ -94,65 +121,146 @@ async def login(evt: CommandEvent) -> None:
     if not email:
         await evt.reply(f"{missing_email}.")
     else:
-        await evt.reply(f"{send_password}.")
+        save_warning = (
+            " NOTE: When saving your credentials, the bridge will store your KakaoTalk password **unencrypted** until you discard it with `$cmdprefix+sp forget-password`."
+            " If you would rather not have the bridge save your password, type `$cmdprefix+sp cancel`, then `$cmdprefix+sp login [_email_]` without `--save`."
+        ) if save else ""
+        await evt.reply(f"{send_password}.{save_warning}")
 
 
-async def enter_password(evt: CommandEvent) -> None:
+async def _enter_password(evt: CommandEvent) -> None:
     try:
         await evt.az.intent.redact(evt.room_id, evt.event_id)
     except MForbidden:
-        pass
-
+        await evt.mark_read()
     assert evt.sender.command_status
+    await _login_with_password(
+        evt,
+        evt.sender.command_status.pop("email"),
+        evt.content.body,
+        evt.sender.command_status.pop("forced"),
+    )
+
+async def _login_with_password(evt: CommandEvent, email: str, password: str, forced: bool) -> None:
     req = {
         "uuid": await evt.sender.get_uuid(),
         "form": {
-            "email": evt.sender.command_status["email"],
-            "password": evt.content.body,
-        }
+            "email": email,
+            "password": password,
+        },
+        "forced": forced,
     }
+    await _try_login(evt, req)
+
+async def _try_login(evt: CommandEvent, req: dict) -> None:
+    save = (
+        evt.sender.command_status.get("save", False)
+        if evt.sender.command_status
+        else False
+    )
     try:
-        await _do_login(evt, req)
-    except DeviceVerificationRequired:
-        await evt.reply(
-            "Open KakaoTalk on your smartphone. It should show a device registration passcode. "
-            "Enter that passcode here."
-        )
+        await _do_login(evt, req, save)
+    except DeviceVerificationRequired as e:
+        if evt.sender.command_status and evt.sender.command_status.get("next") != _enter_dv_code:
+            await evt.reply(
+                "Open KakaoTalk on your smartphone. It should show a device registration passcode. "
+                "Enter that passcode here."
+            )
+            evt.sender.command_status = {
+                "action": "Login",
+                "room_id": evt.room_id,
+                "next": _enter_dv_code,
+                "save": save,
+                "req": req,
+            }
+        else:
+            evt.log.error("Device registration still required after having just registered")
+            await _handle_login_failure(evt, e)
+    except AnotherLogonDetected as e:
+        if not req["forced"]:
+            await evt.reply(
+                 "You are currently logged in to KakaoTalk on a PC or another bridge. "
+                 "In order to log in to this bridge, you will be forced to log out from your other session. "
+                f"To proceed, type `$cmdprefix+sp {_CMD_CONTINUE_LOGIN}`. Otherwise, type `$cmdprefix+sp cancel`."
+            )
+            evt.sender.command_status = {
+                "action": "Login",
+                "room_id": evt.room_id,
+                "next": _force_login,
+                "save": save,
+                "req": req,
+            }
+        else:
+            evt.log.error("Failed to force-login while logged in elsewhere")
+            await _handle_login_failure(evt, e)
+    except IncorrectPassword:
+        await evt.reply(f"Incorrect password. {try_again_or_cancel}")
         evt.sender.command_status = {
             "action": "Login",
             "room_id": evt.room_id,
-            "next": enter_dv_code,
-            "req": req,
+            "next": _enter_password,
+            "email": req["form"]["email"],
+            "save": save,
+            "forced": req["forced"],
         }
-    except IncorrectPassword:
-        await evt.reply(f"Incorrect password. {try_again_or_cancel}")
     #except OAuthException as e:
     #    await evt.reply(f"Error from KakaoTalk:\n\n> {e}")
     except Exception as e:
         await _handle_login_failure(evt, e)
 
 
-async def enter_dv_code(evt: CommandEvent) -> None:
+async def _enter_dv_code(evt: CommandEvent) -> None:
     assert evt.sender.command_status
-    req: dict = evt.sender.command_status["req"]
+    req: dict = evt.sender.command_status.pop("req")
     passcode = evt.content.body
     await evt.mark_read()
     try:
         await KakaoTalkClient.register_device(passcode, **req)
-        await _do_login(evt, req)
     except IncorrectPasscode:
         await evt.reply(f"Incorrect device registration passcode. {try_again_or_cancel}")
     #except OAuthException as e:
     #    await evt.reply(f"Error from KakaoTalk:\n\n> {e}")
     except Exception as e:
         await _handle_login_failure(evt, e)
+    else:
+        await _try_login(evt, req)
 
 
-async def _do_login(evt: CommandEvent, req: dict) -> None:
+async def _force_login(evt: CommandEvent) -> None:
+    command = evt.content.body
+    if command != _CMD_CONTINUE_LOGIN:
+        await evt.reply(
+            f"Unknown action `{command}`. "
+            f"Use `$cmdprefix+sp {_CMD_CONTINUE_LOGIN}` or `$cmdprefix+sp cancel`."
+        )
+        return
+    assert evt.sender.command_status
+    evt.sender.command_status["forced"] = True
+    await evt.mark_read()
+    await _try_login(evt, evt.sender.command_status.pop("req"))
+
+
+async def _do_login(evt: CommandEvent, req: dict, save: bool) -> None:
     oauth_credential = await KakaoTalkClient.login(**req)
     await evt.sender.on_logged_in(oauth_credential)
     evt.sender.command_status = None
     await evt.reply("Successfully logged in")
+    try:
+        if save:
+            email = req["form"]["email"]
+            password = req["form"]["password"]
+            creds = await LoginCredential.get_by_mxid(evt.sender.mxid)
+            if creds:
+                evt.log.warning("Found pre-existing login credentials, so updating them now")
+                creds.email = email
+                creds.password = password
+                await creds.save()
+            else:
+                await LoginCredential(evt.sender.mxid, email, password).insert()
+        else:
+            await LoginCredential.delete_by_mxid(evt.sender.mxid)
+    except:
+        evt.log.exception("Error updating saved credentials after successful login")
 
 async def _handle_login_failure(evt: CommandEvent, e: Exception) -> None:
     evt.sender.command_status = None
@@ -165,6 +273,24 @@ async def _handle_login_failure(evt: CommandEvent, e: Exception) -> None:
     await evt.reply(f"{message}: {e}")
 
 
+@command_handler(
+    needs_auth=True,
+    management_only=True,
+    help_section=SECTION_AUTH,
+    help_text="Delete saved login credentials, if they were saved"
+)
+async def forget_password(evt: CommandEvent) -> None:
+    creds = await LoginCredential.get_by_mxid(evt.sender.mxid)
+    if not creds:
+        await evt.reply("The bridge wasn't storing your login credentials, so there was nothing to forget.")
+    else:
+        await creds.delete()
+        await evt.reply(
+            "This bridge is no longer storing your login credentials. "
+            "If you get logged out unexpectedly, you will have to manually log back in."
+        )
+
+
 @command_handler(
     needs_auth=True,
     help_section=SECTION_AUTH,
@@ -206,3 +332,30 @@ async def reset_device(evt: CommandEvent) -> None:
             "Your next login will use a different device ID.\n\n"
             "The old device must be manually de-registered from the KakaoTalk app."
         )
+
+
+@command_handler(
+    needs_auth=False,
+    help_section=SECTION_AUTH,
+    help_text="When logging in, automatically log out of any other existing KakaoTalk session"
+)
+async def enable_forced_login(evt: CommandEvent) -> None:
+    if evt.sender.force_login:
+        await evt.reply("Forced login is already enabled.")
+        return
+    evt.sender.force_login = True
+    await evt.sender.save()
+    await evt.reply("Forced login is now enabled.")
+
+@command_handler(
+    needs_auth=False,
+    help_section=SECTION_AUTH,
+    help_text="When logging in, ask before logging out of another existing KakaoTalk session, if one exists"
+)
+async def disable_forced_login(evt: CommandEvent) -> None:
+    if not evt.sender.force_login:
+        await evt.reply("Forced login is already disabled.")
+        return
+    evt.sender.force_login = False
+    await evt.sender.save()
+    await evt.reply("Forced login is now disabled.")

matrix_appservice_kakaotalk/commands/conn.py

@@ -45,6 +45,12 @@ async def disconnect(evt: CommandEvent) -> None:
     if not evt.sender.is_connected:
         await evt.reply("You are already disconnected from KakaoTalk chats")
         return
+    if not evt.sender.config["bridge.remain_logged_in_on_disconnect"]:
+        await evt.reply(
+            "This instance of the KakaoTalk bridge does not allow being disconnected from KakaoTalk chats while logged in. "
+            "So, to disconnect, you must log out entirely with the `logout` command."
+        )
+        return
     await evt.mark_read()
     await evt.sender.client.disconnect()
     await evt.reply("Successfully disconnected from KakaoTalk chats. To reconnect, use the `sync` command.")

matrix_appservice_kakaotalk/config.py

@@ -104,6 +104,9 @@ class Config(BaseBridgeConfig):
         copy("bridge.periodic_reconnect.min_connected_time")
         """
         copy("bridge.resync_max_disconnected_time")
+        copy("bridge.remain_logged_in_on_disconnect")
+        copy("bridge.allow_token_relogin")
+        copy("bridge.reconnect_on_token_relogin")
         copy("bridge.sync_on_startup")
         copy("bridge.temporary_disconnect_notices")
         copy("bridge.disable_bridge_notices")

matrix_appservice_kakaotalk/db/__init__.py

@@ -20,10 +20,11 @@ from .portal import Portal
 from .puppet import Puppet
 from .upgrade import upgrade_table
 from .user import User
+from .login_credential import LoginCredential
 
 
 def init(db: Database) -> None:
-    for table in (Portal, Message, User, Puppet):
+    for table in (Portal, Message, User, Puppet, LoginCredential):
         table.db = db
 
 
@@ -34,4 +35,5 @@ __all__ = [
     "Portal",
     "Puppet",
     "User",
+    "LoginCredential",
 ]

matrix_appservice_kakaotalk/db/login_credential.py

@@ -0,0 +1,68 @@
+# matrix-appservice-kakaotalk - A Matrix-KakaoTalk puppeting bridge.
+# Copyright (C) 2022 Tulir Asokan, Andrew Ferrazzutti
+#
+# This program is free software: you can redistribute it and/or modify
+# it under the terms of the GNU Affero General Public License as published by
+# the Free Software Foundation, either version 3 of the License, or
+# (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU Affero General Public License for more details.
+#
+# You should have received a copy of the GNU Affero General Public License
+# along with this program.  If not, see <https://www.gnu.org/licenses/>.
+from __future__ import annotations
+
+from typing import TYPE_CHECKING, ClassVar
+
+from asyncpg import Record
+from attr import dataclass
+
+from mautrix.types import UserID
+from mautrix.util.async_db import Database
+
+fake_db = Database.create("") if TYPE_CHECKING else None
+
+
+@dataclass
+class LoginCredential:
+    db: ClassVar[Database] = fake_db
+
+    mxid: UserID
+    email: str
+    password: str
+
+    @classmethod
+    async def get_by_mxid(cls, mxid: UserID) -> LoginCredential | None:
+        q = "SELECT mxid, email, password FROM login_credential WHERE mxid=$1"
+        row = await cls.db.fetchrow(q, mxid)
+        return cls(**row) if row else None
+
+    @classmethod
+    async def delete_by_mxid(cls, mxid: UserID) -> None:
+        await cls.db.execute("DELETE FROM login_credential WHERE mxid=$1", mxid)
+
+    async def insert(self) -> None:
+        q = """
+            INSERT INTO login_credential (mxid, email, password)
+            VALUES ($1, $2, $3)
+        """
+        await self.db.execute(q, self.mxid, self.email, self.password)
+
+    def get_form(self) -> dict[str, str]:
+        return {
+            "email": self.email,
+            "password": self.password,
+        }
+
+    async def delete(self) -> None:
+        await self.delete_by_mxid(self.mxid)
+
+    async def save(self) -> None:
+        q = """
+            UPDATE login_credential SET email=$2, password=$3 
+            WHERE mxid=$1
+        """
+        await self.db.execute(q, self.mxid, self.email, self.password)

matrix_appservice_kakaotalk/db/upgrade/__init__.py

@@ -19,3 +19,4 @@ upgrade_table = UpgradeTable()
 
 from . import v01_initial_revision
 from . import v02_channel_meta
+from . import v03_user_connection

matrix_appservice_kakaotalk/db/upgrade/v03_user_connection.py

@@ -0,0 +1,38 @@
+# matrix-appservice-kakaotalk - A Matrix-KakaoTalk puppeting bridge.
+# Copyright (C) 2022 Tulir Asokan, Andrew Ferrazzutti
+#
+# This program is free software: you can redistribute it and/or modify
+# it under the terms of the GNU Affero General Public License as published by
+# the Free Software Foundation, either version 3 of the License, or
+# (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU Affero General Public License for more details.
+#
+# You should have received a copy of the GNU Affero General Public License
+# along with this program.  If not, see <https://www.gnu.org/licenses/>.
+from mautrix.util.async_db import Connection
+
+from . import upgrade_table
+
+
+@upgrade_table.register(description="Track login credentials, connections, and force-login preferences")
+async def upgrade_v3(conn: Connection) -> None:
+    await conn.execute('ALTER TABLE "user" ADD COLUMN force_login BOOLEAN NOT NULL DEFAULT false')
+    await conn.execute('ALTER TABLE "user" ADD COLUMN was_connected BOOLEAN NOT NULL DEFAULT false')
+    # Just for now, assume that logged in = connected
+    await conn.execute('UPDATE "user" SET was_connected=true WHERE access_token IS NOT NULL')
+
+    await conn.execute(
+        """CREATE TABLE login_credential (
+            mxid        TEXT PRIMARY KEY,
+            email       TEXT NOT NULL,
+            password    TEXT NOT NULL,
+
+            FOREIGN KEY (mxid)
+                REFERENCES "user" (mxid)
+                ON DELETE CASCADE
+        )"""
+    )

matrix_appservice_kakaotalk/db/user.py

@@ -33,6 +33,8 @@ class User:
     db: ClassVar[Database] = fake_db
 
     mxid: UserID
+    force_login: bool
+    was_connected: bool
     ktid: Long | None = field(converter=to_optional_long)
     uuid: str | None
     access_token: str | None
@@ -47,7 +49,7 @@ class User:
     def _from_optional_row(cls, row: Record | None) -> User | None:
         return cls._from_row(row) if row is not None else None
 
-    _columns = "mxid, ktid, uuid, access_token, refresh_token, notice_room"
+    _columns = "mxid, force_login, was_connected, ktid, uuid, access_token, refresh_token, notice_room"
 
     @classmethod
     async def all_logged_in(cls) -> List[User]:
@@ -76,6 +78,8 @@ class User:
     def _values(self):
         return (
             self.mxid,
+            self.force_login,
+            self.was_connected,
             self.ktid,
             self.uuid,
             self.access_token,
@@ -85,8 +89,8 @@ class User:
 
     async def insert(self) -> None:
         q = """
-            INSERT INTO "user" (mxid, ktid, uuid, access_token, refresh_token, notice_room) 
-            VALUES ($1, $2, $3, $4, $5, $6)
+            INSERT INTO "user" (mxid, force_login, was_connected, ktid, uuid, access_token, refresh_token, notice_room) 
+            VALUES ($1, $2, $3, $4, $5, $6, $7, $8)
         """
         await self.db.execute(q, *self._values)
 
@@ -95,7 +99,7 @@ class User:
 
     async def save(self) -> None:
         q = """
-            UPDATE "user" SET ktid=$2, uuid=$3, access_token=$4, refresh_token=$5, notice_room=$6 
+            UPDATE "user" SET force_login=$2, was_connected=$3, ktid=$4, uuid=$5, access_token=$6, refresh_token=$7, notice_room=$8 
             WHERE mxid=$1
         """
         await self.db.execute(q, *self._values)

matrix_appservice_kakaotalk/example-config.yaml

@@ -191,7 +191,18 @@ bridge:
     # Set to 0 to always re-sync, or -1 to never re-sync automatically.
     # TODO Actually use this setting
     resync_max_disconnected_time: 5
-    # Should the bridge do a resync on startup?
+    # Should users remain logged in after being disconnected from chatroom updates?
+    # This is a convenience feature, but might make the bridge look more suspicious to KakaoTalk.
+    remain_logged_in_on_disconnect: true
+    # May the bridge restore user logins with session tokens instead of requiring a password?
+    # This is a convenience feature, but might make the bridge look more suspicious to KakaoTalk.
+    # Note that password-based login will be tried first for users who have saved their password.
+    allow_token_relogin: true
+    # Should the bridge connect users to chatroom updates after a token-based login?
+    # This will disconnect any KakaoTalk PC/bridge sessions that were started since the last connection.
+    # This is a convenience feature, but might make the bridge look more suspicious to KakaoTalk.
+    reconnect_on_token_relogin: true
+    # Should the bridge do a resync for connected users on startup?
     sync_on_startup: true
     # Whether or not temporary disconnections should send notices to the notice room.
     # If this is false, disconnections will never send messages and connections will only send

matrix_appservice_kakaotalk/kt/client/client.py

@@ -137,13 +137,19 @@ class Client:
         return cls._api_request_void("register_device", passcode=passcode, **req)
 
     @classmethod
-    def login(cls, **req: JSON) -> Awaitable[OAuthCredential]:
+    def login(cls, uuid: str, form: JSON, forced: bool) -> Awaitable[OAuthCredential]:
         """
         Obtain a session token by logging in with user-provided credentials.
         Must have first called register_device with these credentials.
         """
         # NOTE Actually returns an auth LoginData, but this only needs an OAuthCredential
-        return cls._api_request_result(OAuthCredential, "login", **req)
+        return cls._api_request_result(
+            OAuthCredential,
+            "login",
+            uuid=uuid,
+            form=form,
+            forced=forced,
+        )
 
     # endregion
 

matrix_appservice_kakaotalk/kt/client/error_helper.py

@@ -14,13 +14,13 @@
 # You should have received a copy of the GNU Affero General Public License
 # along with this program.  If not, see <https://www.gnu.org/licenses/>.
 """Internal helpers for error handling."""
-
 from __future__ import annotations
 
 from typing import NoReturn, Type
 
 from .errors import (
     CommandException,
+    AnotherLogonDetected,
     AuthenticationRequired,
     DeviceVerificationRequired,
     IncorrectPasscode,
@@ -61,7 +61,7 @@ _error_code_class_map: dict[KnownAuthStatusCode | KnownDataStatusCode | int, Typ
     #KnownAuthStatusCode.EXCEED_DAILY_REQUEST_LIMIT_VOICECALL: "Daily voicecall limit exceeded",
     #KnownAuthStatusCode.EXCEED_DAILY_REQUEST_LIMIT_WITHOUT_TOKEN: "Daily tokenless request limit exceeded",
     KnownAuthStatusCode.DEVICE_NOT_REGISTERED: DeviceVerificationRequired,
-    #KnownAuthStatusCode.ANOTHER_LOGON: "Another logon detected",
+    KnownAuthStatusCode.ANOTHER_LOGON: AnotherLogonDetected,
     #KnownAuthStatusCode.DEVICE_REGISTER_FAILED: "Device registration failed",
     #KnownAuthStatusCode.INVALID_DEVICE_REGISTER: "Invalid device",
     KnownAuthStatusCode.INVALID_PASSCODE: IncorrectPasscode,

matrix_appservice_kakaotalk/kt/client/errors.py

@@ -14,7 +14,6 @@
 # You should have received a copy of the GNU Affero General Public License
 # along with this program.  If not, see <https://www.gnu.org/licenses/>.
 """Helper functions & types for status codes for the KakaoTalk API."""
-
 from __future__ import annotations
 
 from ..types.api.auth_api_client import KnownAuthStatusCode
@@ -48,6 +47,9 @@ class OAuthException(CommandException):
 class DeviceVerificationRequired(OAuthException):
     pass
 
+class AnotherLogonDetected(OAuthException):
+    pass
+
 class IncorrectPassword(OAuthException):
     pass
 

matrix_appservice_kakaotalk/user.py

@@ -35,10 +35,16 @@ from mautrix.util.simple_lock import SimpleLock
 
 from . import portal as po, puppet as pu
 from .config import Config
-from .db import User as DBUser
+from .db import User as DBUser, LoginCredential
 
 from .kt.client import Client
-from .kt.client.errors import AuthenticationRequired, ResponseError
+from .kt.client.errors import (
+    AuthenticationRequired,
+    AnotherLogonDetected,
+    IncorrectPassword,
+    OAuthException,
+    ResponseError,
+)
 from .kt.client.types import PortalChannelInfo, SettingsStruct
 from .kt.types.bson import Long
 from .kt.types.channel.channel_info import ChannelInfo, NormalChannelInfo, NormalChannelData
@@ -107,6 +113,8 @@ class User(DBUser, BaseUser):
     def __init__(
         self,
         mxid: UserID,
+        force_login: bool,
+        was_connected: bool,
         ktid: Long | None = None,
         uuid: str | None = None,
         access_token: str | None = None,
@@ -115,6 +123,8 @@ class User(DBUser, BaseUser):
     ) -> None:
         super().__init__(
             mxid=mxid,
+            force_login=force_login,
+            was_connected=was_connected,
             ktid=ktid,
             uuid=uuid,
             access_token=access_token,
@@ -277,7 +287,51 @@ class User(DBUser, BaseUser):
     async def _load_session(self, is_startup: bool) -> bool:
         if self._is_logged_in and is_startup:
             return True
-        elif not self.has_state:
+        if not self.was_connected and not self.config["bridge.remain_logged_in_on_disconnect"]:
+            self.log.warning("Not logging in because last session was disconnected, and login+disconnection is forbidden by config")
+            await self.push_bridge_state(
+                BridgeStateEvent.LOGGED_OUT,
+                error="logged-out",
+            )
+            return False
+        latest_exc: Exception | None = None
+        password_ok = False
+        try:
+            creds = await LoginCredential.get_by_mxid(self.mxid)
+        except Exception as e:
+            self.log.exception("Exception while looking for saved password")
+            creds = None
+        if creds:
+            uuid = await self.get_uuid()
+            form = creds.get_form()
+            oauth_credential = None
+            try:
+                oauth_credential = await Client.login(uuid=uuid, form=form, forced=False)
+            except IncorrectPassword as e:
+                latest_exc = e
+            except AnotherLogonDetected as e:
+                if self.force_login:
+                    try:
+                        # Wait a moment to make it look like a user-initiated response
+                        await asyncio.sleep(2)
+                        oauth_credential = await Client.login(uuid=uuid, form=form, forced=True)
+                    except OAuthException as e:
+                        latest_exc = e
+            if oauth_credential:
+                self.oauth_credential = oauth_credential
+                await self.save()
+                password_ok = True
+            else:
+                try:
+                    await creds.delete()
+                except:
+                    self.log.exception("Exception while deleting incorrect password")
+        if password_ok or self.config["bridge.allow_token_relogin"] and self.has_state:
+            if not password_ok:
+                self.log.warning("Using token-based relogin after password-based relogin failed")
+        elif latest_exc:
+            raise latest_exc
+        else:
             # If we have a user in the DB with no state, we can assume
             # KT logged us out and the bridge has restarted
             await self.push_bridge_state(
@@ -295,10 +349,10 @@ class User(DBUser, BaseUser):
         self._track_metric(METRIC_LOGGED_IN, True)
         self._is_logged_in = True
         self.is_connected = None
-        asyncio.create_task(self.post_login(is_startup=is_startup))
+        asyncio.create_task(self.post_login(is_startup=is_startup, is_token_login=not password_ok))
         return True
 
-    async def _send_reset_notice(self, e: AuthenticationRequired, edit: EventID | None = None) -> None:
+    async def _send_reset_notice(self, e: OAuthException, edit: EventID | None = None) -> None:
         await self.send_bridge_notice(
             "Got authentication error from KakaoTalk:\n\n"
             f"> {e.message}\n\n"
@@ -333,8 +387,13 @@ class User(DBUser, BaseUser):
         self, event_id: EventID | None = None, retries: int = 3, is_startup: bool = False
     ) -> None:
         try:
-            await self._load_session(is_startup=is_startup)
-        except AuthenticationRequired as e:
+            if not await self._load_session(is_startup=is_startup) and self.has_state:
+                await self.send_bridge_notice(
+                    "Logged out of KakaoTalk. Must use the `login` command to log back in.",
+                    important=True,
+                )
+                await self.logout(remove_ktid=False)
+        except OAuthException as e:
             await self._send_reset_notice(e, edit=event_id)
         # TODO Throw a ResponseError on network failures
         except ResponseError as e:
@@ -383,6 +442,7 @@ class User(DBUser, BaseUser):
 
         self._is_logged_in = False
         self.is_connected = None
+        self.was_connected = False
         self._client = None
 
         if self.ktid and remove_ktid:
@@ -392,7 +452,7 @@ class User(DBUser, BaseUser):
 
         await self.save()
 
-    async def post_login(self, is_startup: bool) -> None:
+    async def post_login(self, is_startup: bool, is_token_login: bool) -> None:
         self.log.info("Running post-login actions")
         assert self.ktid
         self._add_to_cache()
@@ -406,13 +466,19 @@ class User(DBUser, BaseUser):
         except Exception:
             self.log.exception("Failed to automatically enable custom puppet")
 
-        # TODO Check if things break when a live message comes in during syncing
-        if self.config["bridge.sync_on_startup"] or not is_startup:
-            sync_count = self.config["bridge.initial_chat_sync"]
+        if not is_token_login or self.was_connected and self.config["bridge.reconnect_on_token_relogin"]:
+            # TODO Check if things break when a live message comes in during syncing
+            if self.config["bridge.sync_on_startup"] or not is_startup:
+                sync_count = self.config["bridge.initial_chat_sync"]
+            else:
+                sync_count = None
+            await self.connect_and_sync(sync_count)
         else:
-            sync_count = None
-        # TODO Don't auto-connect on startup if user's last state was disconnected
-        await self.connect_and_sync(sync_count)
+            await self.send_bridge_notice(
+                f"Logged into KakaoTalk. To connect to chatroom updates, use the `sync` command."
+            )
+            self.was_connected = False
+            await self.save()
 
     async def get_direct_chats(self) -> dict[UserID, list[RoomID]]:
         return {
@@ -645,14 +711,16 @@ class User(DBUser, BaseUser):
         if self.temp_disconnect_notices:
             await self.send_bridge_notice("Connected to KakaoTalk chats")
         await self.push_bridge_state(BridgeStateEvent.CONNECTED)
+        self.was_connected = True
+        await self.save()
 
     async def on_disconnect(self, res: KickoutRes | None) -> None:
         self.is_connected = False
         self._track_metric(METRIC_CONNECTED, False)
+        logout = not self.config["bridge.remain_logged_in_on_disconnect"]
         if res:
-            logout = False
             if res.reason == KnownKickoutType.LOGIN_ANOTHER:
-                reason_str = "Logged in from another desktop client."
+                reason_str = "Logged in on a PC or another bridge."
             elif res.reason == KnownKickoutType.CHANGE_SERVER:
                 # TODO Reconnect automatically instead
                 reason_str = "KakaoTalk backend server changed."
@@ -661,12 +729,19 @@ class User(DBUser, BaseUser):
                 logout = True
             else:
                 reason_str = f"Unknown reason ({res.reason})."
+        else:
+            reason_str = None
+        if not logout:
+            # TODO What bridge state to push?
+            self.was_connected = False
+            await self.save()
+        else:
+            await self.logout()
+        if reason_str:
             if not logout:
-                reason_suffix = " To reconnect, use the `sync` command."
-                # TODO What bridge state to push?
+                reason_suffix = "To reconnect, use the `sync` command."
             else:
-                reason_suffix = " You are now logged out."
-                await self.logout()
+                reason_suffix = "You are now logged out. To log back in, use the `login` command."
             await self.send_bridge_notice(f"Disconnected from KakaoTalk: {reason_str} {reason_suffix}")
 
     async def on_error(self, error: JSON) -> None:
@@ -681,7 +756,7 @@ class User(DBUser, BaseUser):
         self.is_connected = False
         self._track_metric(METRIC_CONNECTED, False)
         self._client = None
-        if self._is_logged_in:
+        if self._is_logged_in and self.was_connected:
             if self.temp_disconnect_notices:
                 await self.send_bridge_notice(
                     "Disconnected from KakaoTalk: backend helper module exited. "
@@ -702,7 +777,7 @@ class User(DBUser, BaseUser):
         #      Should also catch unlikely authentication errors
         self._logged_in_info = await self._client.start()
         self._logged_in_info_time = time.monotonic()
-        asyncio.create_task(self.post_login(is_startup=True))
+        asyncio.create_task(self.post_login(is_startup=True, is_token_login=False))
 
     @async_time(METRIC_CHAT)
     async def on_chat(self, chat: Chatlog, channel_id: Long, channel_type: ChannelType) -> None:

node/src/client.js

@@ -520,6 +520,7 @@ export default class PeerClient {
 	 * @param {Object} req
 	 * @param {string} req.uuid
 	 * @param {Object} req.form
+	 * @param {boolean} req.forced
 	 * @returns The response of the login attempt, including obtained
 	 * credentials for subsequent token-based login. If a required device passcode
 	 * request failed, its status is stored here.
@@ -527,7 +528,7 @@ export default class PeerClient {
 	handleLogin = async (req) => {
 		// TODO Look for a logout API call
 		const authClient = await this.#createAuthClient(req.uuid)
-		const loginRes = await authClient.login(req.form, true)
+		const loginRes = await authClient.login(req.form, req.forced)
 		if (loginRes.status === KnownAuthStatusCode.DEVICE_NOT_REGISTERED) {
 			const passcodeRes = await authClient.requestPasscode(req.form)
 			if (!passcodeRes.success) {