errors.py

# -*- coding: utf-8 -*-
# Copyright 2014-2016 OpenMarket Ltd
# Copyright 2018 New Vector Ltd
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
#     http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.

"""Contains exceptions and error codes."""

import logging
import typing
from http import HTTPStatus
from typing import Dict, List, Optional, Union

from twisted.web import http

from synapse.util import json_decoder

if typing.TYPE_CHECKING:
    from synapse.types import JsonDict

logger = logging.getLogger(__name__)


class Codes:
    UNRECOGNIZED = "M_UNRECOGNIZED"
    UNAUTHORIZED = "M_UNAUTHORIZED"
    FORBIDDEN = "M_FORBIDDEN"
    BAD_JSON = "M_BAD_JSON"
    NOT_JSON = "M_NOT_JSON"
    USER_IN_USE = "M_USER_IN_USE"
    ROOM_IN_USE = "M_ROOM_IN_USE"
    BAD_PAGINATION = "M_BAD_PAGINATION"
    BAD_STATE = "M_BAD_STATE"
    UNKNOWN = "M_UNKNOWN"
    NOT_FOUND = "M_NOT_FOUND"
    MISSING_TOKEN = "M_MISSING_TOKEN"
    UNKNOWN_TOKEN = "M_UNKNOWN_TOKEN"
    GUEST_ACCESS_FORBIDDEN = "M_GUEST_ACCESS_FORBIDDEN"
    LIMIT_EXCEEDED = "M_LIMIT_EXCEEDED"
    CAPTCHA_NEEDED = "M_CAPTCHA_NEEDED"
    CAPTCHA_INVALID = "M_CAPTCHA_INVALID"
    MISSING_PARAM = "M_MISSING_PARAM"
    INVALID_PARAM = "M_INVALID_PARAM"
    TOO_LARGE = "M_TOO_LARGE"
    EXCLUSIVE = "M_EXCLUSIVE"
    THREEPID_AUTH_FAILED = "M_THREEPID_AUTH_FAILED"
    THREEPID_IN_USE = "M_THREEPID_IN_USE"
    THREEPID_NOT_FOUND = "M_THREEPID_NOT_FOUND"
    THREEPID_DENIED = "M_THREEPID_DENIED"
    INVALID_USERNAME = "M_INVALID_USERNAME"
    SERVER_NOT_TRUSTED = "M_SERVER_NOT_TRUSTED"
    CONSENT_NOT_GIVEN = "M_CONSENT_NOT_GIVEN"
    CANNOT_LEAVE_SERVER_NOTICE_ROOM = "M_CANNOT_LEAVE_SERVER_NOTICE_ROOM"
    RESOURCE_LIMIT_EXCEEDED = "M_RESOURCE_LIMIT_EXCEEDED"
    UNSUPPORTED_ROOM_VERSION = "M_UNSUPPORTED_ROOM_VERSION"
    INCOMPATIBLE_ROOM_VERSION = "M_INCOMPATIBLE_ROOM_VERSION"
    WRONG_ROOM_KEYS_VERSION = "M_WRONG_ROOM_KEYS_VERSION"
    EXPIRED_ACCOUNT = "ORG_MATRIX_EXPIRED_ACCOUNT"
    PASSWORD_TOO_SHORT = "M_PASSWORD_TOO_SHORT"
    PASSWORD_NO_DIGIT = "M_PASSWORD_NO_DIGIT"
    PASSWORD_NO_UPPERCASE = "M_PASSWORD_NO_UPPERCASE"
    PASSWORD_NO_LOWERCASE = "M_PASSWORD_NO_LOWERCASE"
    PASSWORD_NO_SYMBOL = "M_PASSWORD_NO_SYMBOL"
    PASSWORD_IN_DICTIONARY = "M_PASSWORD_IN_DICTIONARY"
    WEAK_PASSWORD = "M_WEAK_PASSWORD"
    INVALID_SIGNATURE = "M_INVALID_SIGNATURE"
    USER_DEACTIVATED = "M_USER_DEACTIVATED"
    BAD_ALIAS = "M_BAD_ALIAS"


class CodeMessageException(RuntimeError):
    """An exception with integer code and message string attributes.

    Attributes:
        code: HTTP error code
        msg: string describing the error
    """

    def __init__(self, code: Union[int, HTTPStatus], msg: str):
        super().__init__("%d: %s" % (code, msg))

        # Some calls to this method pass instances of http.HTTPStatus for `code`.
        # While HTTPStatus is a subclass of int, it has magic __str__ methods
        # which emit `HTTPStatus.FORBIDDEN` when converted to a str, instead of `403`.
        # This causes inconsistency in our log lines.
        #
        # To eliminate this behaviour, we convert them to their integer equivalents here.
        self.code = int(code)
        self.msg = msg


class RedirectException(CodeMessageException):
    """A pseudo-error indicating that we want to redirect the client to a different
    location

    Attributes:
        cookies: a list of set-cookies values to add to the response. For example:
           b"sessionId=a3fWa; Expires=Wed, 21 Oct 2015 07:28:00 GMT"
    """

    def __init__(self, location: bytes, http_code: int = http.FOUND):
        """

        Args:
            location: the URI to redirect to
            http_code: the HTTP response code
        """
        msg = "Redirect to %s" % (location.decode("utf-8"),)
        super().__init__(code=http_code, msg=msg)
        self.location = location

        self.cookies = []  # type: List[bytes]


class SynapseError(CodeMessageException):
    """A base exception type for matrix errors which have an errcode and error
    message (as well as an HTTP status code).

    Attributes:
        errcode: Matrix error code e.g 'M_FORBIDDEN'
    """

    def __init__(self, code: int, msg: str, errcode: str = Codes.UNKNOWN):
        """Constructs a synapse error.

        Args:
            code: The integer error code (an HTTP response code)
            msg: The human-readable error message.
            errcode: The matrix error code e.g 'M_FORBIDDEN'
        """
        super().__init__(code, msg)
        self.errcode = errcode

    def error_dict(self):
        return cs_error(self.msg, self.errcode)


class ProxiedRequestError(SynapseError):
    """An error from a general matrix endpoint, eg. from a proxied Matrix API call.

    Attributes:
        errcode: Matrix error code e.g 'M_FORBIDDEN'
    """

    def __init__(
        self,
        code: int,
        msg: str,
        errcode: str = Codes.UNKNOWN,
        additional_fields: Optional[Dict] = None,
    ):
        super().__init__(code, msg, errcode)
        if additional_fields is None:
            self._additional_fields = {}  # type: Dict
        else:
            self._additional_fields = dict(additional_fields)

    def error_dict(self):
        return cs_error(self.msg, self.errcode, **self._additional_fields)


class ConsentNotGivenError(SynapseError):
    """The error returned to the client when the user has not consented to the
    privacy policy.
    """

    def __init__(self, msg: str, consent_uri: str):
        """Constructs a ConsentNotGivenError

        Args:
            msg: The human-readable error message
            consent_url: The URL where the user can give their consent
        """
        super().__init__(
            code=HTTPStatus.FORBIDDEN, msg=msg, errcode=Codes.CONSENT_NOT_GIVEN
        )
        self._consent_uri = consent_uri

    def error_dict(self):
        return cs_error(self.msg, self.errcode, consent_uri=self._consent_uri)


class UserDeactivatedError(SynapseError):
    """The error returned to the client when the user attempted to access an
    authenticated endpoint, but the account has been deactivated.
    """

    def __init__(self, msg: str):
        """Constructs a UserDeactivatedError

        Args:
            msg: The human-readable error message
        """
        super().__init__(
            code=HTTPStatus.FORBIDDEN, msg=msg, errcode=Codes.USER_DEACTIVATED
        )


class FederationDeniedError(SynapseError):
    """An error raised when the server tries to federate with a server which
    is not on its federation whitelist.

    Attributes:
        destination: The destination which has been denied
    """

    def __init__(self, destination: Optional[str]):
        """Raised by federation client or server to indicate that we are
        are deliberately not attempting to contact a given server because it is
        not on our federation whitelist.

        Args:
            destination: the domain in question
        """

        self.destination = destination

        super().__init__(
            code=403,
            msg="Federation denied with %s." % (self.destination,),
            errcode=Codes.FORBIDDEN,
        )


class InteractiveAuthIncompleteError(Exception):
    """An error raised when UI auth is not yet complete

    (This indicates we should return a 401 with 'result' as the body)

    Attributes:
        session_id: The ID of the ongoing interactive auth session.
        result: the server response to the request, which should be
            passed back to the client
    """

    def __init__(self, session_id: str, result: "JsonDict"):
        super().__init__("Interactive auth not yet complete")
        self.session_id = session_id
        self.result = result


class UnrecognizedRequestError(SynapseError):
    """An error indicating we don't understand the request you're trying to make"""

    def __init__(self, *args, **kwargs):
        if "errcode" not in kwargs:
            kwargs["errcode"] = Codes.UNRECOGNIZED
        if len(args) == 0:
            message = "Unrecognized request"
        else:
            message = args[0]
        super().__init__(400, message, **kwargs)


class NotFoundError(SynapseError):
    """An error indicating we can't find the thing you asked for"""

    def __init__(self, msg: str = "Not found", errcode: str = Codes.NOT_FOUND):
        super().__init__(404, msg, errcode=errcode)


class AuthError(SynapseError):
    """An error raised when there was a problem authorising an event, and at various
    other poorly-defined times.
    """

    def __init__(self, *args, **kwargs):
        if "errcode" not in kwargs:
            kwargs["errcode"] = Codes.FORBIDDEN
        super().__init__(*args, **kwargs)


class InvalidClientCredentialsError(SynapseError):
    """An error raised when there was a problem with the authorisation credentials
    in a client request.

    https://matrix.org/docs/spec/client_server/r0.5.0#using-access-tokens:

    When credentials are required but missing or invalid, the HTTP call will
    return with a status of 401 and the error code, M_MISSING_TOKEN or
    M_UNKNOWN_TOKEN respectively.
    """

    def __init__(self, msg: str, errcode: str):
        super().__init__(code=401, msg=msg, errcode=errcode)


class MissingClientTokenError(InvalidClientCredentialsError):
    """Raised when we couldn't find the access token in a request"""

    def __init__(self, msg: str = "Missing access token"):
        super().__init__(msg=msg, errcode="M_MISSING_TOKEN")


class InvalidClientTokenError(InvalidClientCredentialsError):
    """Raised when we didn't understand the access token in a request"""

    def __init__(
        self, msg: str = "Unrecognised access token", soft_logout: bool = False
    ):
        super().__init__(msg=msg, errcode="M_UNKNOWN_TOKEN")
        self._soft_logout = soft_logout

    def error_dict(self):
        d = super().error_dict()
        d["soft_logout"] = self._soft_logout
        return d


class ResourceLimitError(SynapseError):
    """
    Any error raised when there is a problem with resource usage.
    For instance, the monthly active user limit for the server has been exceeded
    """

    def __init__(
        self,
        code: int,
        msg: str,
        errcode: str = Codes.RESOURCE_LIMIT_EXCEEDED,
        admin_contact: Optional[str] = None,
        limit_type: Optional[str] = None,
    ):
        self.admin_contact = admin_contact
        self.limit_type = limit_type
        super().__init__(code, msg, errcode=errcode)

    def error_dict(self):
        return cs_error(
            self.msg,
            self.errcode,
            admin_contact=self.admin_contact,
            limit_type=self.limit_type,
        )


class EventSizeError(SynapseError):
    """An error raised when an event is too big."""

    def __init__(self, *args, **kwargs):
        if "errcode" not in kwargs:
            kwargs["errcode"] = Codes.TOO_LARGE
        super().__init__(413, *args, **kwargs)


class EventStreamError(SynapseError):
    """An error raised when there a problem with the event stream."""

    def __init__(self, *args, **kwargs):
        if "errcode" not in kwargs:
            kwargs["errcode"] = Codes.BAD_PAGINATION
        super().__init__(*args, **kwargs)


class LoginError(SynapseError):
    """An error raised when there was a problem logging in."""

    pass


class StoreError(SynapseError):
    """An error raised when there was a problem storing some data."""

    pass


class InvalidCaptchaError(SynapseError):
    def __init__(
        self,
        code: int = 400,
        msg: str = "Invalid captcha.",
        error_url: Optional[str] = None,
        errcode: str = Codes.CAPTCHA_INVALID,
    ):
        super().__init__(code, msg, errcode)
        self.error_url = error_url

    def error_dict(self):
        return cs_error(self.msg, self.errcode, error_url=self.error_url)


class LimitExceededError(SynapseError):
    """A client has sent too many requests and is being throttled."""

    def __init__(
        self,
        code: int = 429,
        msg: str = "Too Many Requests",
        retry_after_ms: Optional[int] = None,
        errcode: str = Codes.LIMIT_EXCEEDED,
    ):
        super().__init__(code, msg, errcode)
        self.retry_after_ms = retry_after_ms

    def error_dict(self):
        return cs_error(self.msg, self.errcode, retry_after_ms=self.retry_after_ms)


class RoomKeysVersionError(SynapseError):
    """A client has tried to upload to a non-current version of the room_keys store"""

    def __init__(self, current_version: str):
        """
        Args:
            current_version: the current version of the store they should have used
        """
        super().__init__(403, "Wrong room_keys version", Codes.WRONG_ROOM_KEYS_VERSION)
        self.current_version = current_version


class UnsupportedRoomVersionError(SynapseError):
    """The client's request to create a room used a room version that the server does
    not support."""

    def __init__(self, msg: str = "Homeserver does not support this room version"):
        super().__init__(
            code=400,
            msg=msg,
            errcode=Codes.UNSUPPORTED_ROOM_VERSION,
        )


class ThreepidValidationError(SynapseError):
    """An error raised when there was a problem authorising an event."""

    def __init__(self, *args, **kwargs):
        if "errcode" not in kwargs:
            kwargs["errcode"] = Codes.FORBIDDEN
        super().__init__(*args, **kwargs)


class IncompatibleRoomVersionError(SynapseError):
    """A server is trying to join a room whose version it does not support.

    Unlike UnsupportedRoomVersionError, it is specific to the case of the make_join
    failing.
    """

    def __init__(self, room_version: str):
        super().__init__(
            code=400,
            msg="Your homeserver does not support the features required to "
            "join this room",
            errcode=Codes.INCOMPATIBLE_ROOM_VERSION,
        )

        self._room_version = room_version

    def error_dict(self):
        return cs_error(self.msg, self.errcode, room_version=self._room_version)


class PasswordRefusedError(SynapseError):
    """A password has been refused, either during password reset/change or registration."""

    def __init__(
        self,
        msg: str = "This password doesn't comply with the server's policy",
        errcode: str = Codes.WEAK_PASSWORD,
    ):
        super().__init__(
            code=400,
            msg=msg,
            errcode=errcode,
        )


class RequestSendFailed(RuntimeError):
    """Sending a HTTP request over federation failed due to not being able to
    talk to the remote server for some reason.

    This exception is used to differentiate "expected" errors that arise due to
    networking (e.g. DNS failures, connection timeouts etc), versus unexpected
    errors (like programming errors).
    """

    def __init__(self, inner_exception, can_retry):
        super().__init__(
            "Failed to send request: %s: %s"
            % (type(inner_exception).__name__, inner_exception)
        )
        self.inner_exception = inner_exception
        self.can_retry = can_retry


def cs_error(msg: str, code: str = Codes.UNKNOWN, **kwargs):
    """Utility method for constructing an error response for client-server
    interactions.

    Args:
        msg: The error message.
        code: The error code.
        kwargs: Additional keys to add to the response.
    Returns:
        A dict representing the error response JSON.
    """
    err = {"error": msg, "errcode": code}
    for key, value in kwargs.items():
        err[key] = value
    return err


class FederationError(RuntimeError):
    """This class is used to inform remote homeservers about erroneous
    PDUs they sent us.

    FATAL: The remote server could not interpret the source event.
        (e.g., it was missing a required field)
    ERROR: The remote server interpreted the event, but it failed some other
        check (e.g. auth)
    WARN: The remote server accepted the event, but believes some part of it
        is wrong (e.g., it referred to an invalid event)
    """

    def __init__(
        self,
        level: str,
        code: int,
        reason: str,
        affected: str,
        source: Optional[str] = None,
    ):
        if level not in ["FATAL", "ERROR", "WARN"]:
            raise ValueError("Level is not valid: %s" % (level,))
        self.level = level
        self.code = code
        self.reason = reason
        self.affected = affected
        self.source = source

        msg = "%s %s: %s" % (level, code, reason)
        super().__init__(msg)

    def get_dict(self):
        return {
            "level": self.level,
            "code": self.code,
            "reason": self.reason,
            "affected": self.affected,
            "source": self.source if self.source else self.affected,
        }


class HttpResponseException(CodeMessageException):
    """
    Represents an HTTP-level failure of an outbound request

    Attributes:
        response: body of response
    """

    def __init__(self, code: int, msg: str, response: bytes):
        """

        Args:
            code: HTTP status code
            msg: reason phrase from HTTP response status line
            response: body of response
        """
        super().__init__(code, msg)
        self.response = response

    def to_synapse_error(self):
        """Make a SynapseError based on an HTTPResponseException

        This is useful when a proxied request has failed, and we need to
        decide how to map the failure onto a matrix error to send back to the
        client.

        An attempt is made to parse the body of the http response as a matrix
        error. If that succeeds, the errcode and error message from the body
        are used as the errcode and error message in the new synapse error.

        Otherwise, the errcode is set to M_UNKNOWN, and the error message is
        set to the reason code from the HTTP response.

        Returns:
            SynapseError:
        """
        # try to parse the body as json, to get better errcode/msg, but
        # default to M_UNKNOWN with the HTTP status as the error text
        try:
            j = json_decoder.decode(self.response.decode("utf-8"))
        except ValueError:
            j = {}

        if not isinstance(j, dict):
            j = {}

        errcode = j.pop("errcode", Codes.UNKNOWN)
        errmsg = j.pop("error", self.msg)

        return ProxiedRequestError(self.code, errmsg, errcode, j)


class ShadowBanError(Exception):
    """
    Raised when a shadow-banned user attempts to perform an action.

    This should be caught and a proper "fake" success response sent to the user.
    """