<gh_stars>0
import functools
import hashlib
import json
import secrets
from decimal import Decimal
from time import time

import boto3
from pyramid.interfaces import ISession, ISessionFactory
from zope.interface import implementer


class RaceConditionException(Exception):
    pass


@implementer(ISessionFactory)
class DynamoDBSessionFactory:
    def __init__(
            self,
            table,
            cookie_name='session_id',
            max_age=None,
            path='/',
            domain=None,
            secure=None,
            httponly=True,
            samesite='Strict',
            timeout=1200,
            reissue_time=120,
    ):
        """
    A Pyramid session factory which will provide DynamoDB-backed
    sessions.

    The DynamoDB table must have a hash key ``sid`` of binary (B) type and a
    time-to-live on the ``exp`` attribute.

    :param table:  The DynamoDB table to use.  Can be a string or a boto3 Table
        object.
    :type table:  ``str`` or ``Table``
    :param cookie_name:  The name of the cookie used to store the session ID.
        Defaults to ``session_id``.
    :type cookie_name: str
    :param max_age:  The expiration time for the cookie in seconds.  Defaults
        to ``None`` (session-only cookie).
    :type max_age:  int
    :param path:  The path for the cookie.  Defaults to ``/``.
    :type path:  str
    :param domain:  The domain for the cookie.  Defaults to no domain.
    :type domain:  str
    :param secure:  If true, sets the ``secure`` flag for the cookie.  Defaults
        to ``None``, which will set the flag if the request is made via HTTPS.
    :type secure:  bool
    :param httponly:  If true, hide the cookie from Javascript by setting the
        ``HttpOnly`` flag.  Defaults to true.
    :type httponly:  bool
    :param samesite:  The SameSite property for the cookie, or ``None`` to
        disable the SameSite option.  Defaults to ``Strict``.
    :type samesite:  str
    :param timeout:  The number of seconds of inactivity before the session
        times out.  Defaults to ``1200``.  (20 minutes)
    :type timeout:  int
    :param reissue_time:  The number of seconds before the session is
        "reissued," meaning that the activity timeout is reset.  Reissuing
        performs a write to DynamoDB, so it is recommended to set this to a
        reasonably high value, such as 1/10 of the timeout.  Defaults to
        ``120``.  (2 minutes)
    :type reissue_time:  int

    """
        if isinstance(table, str):
            dynamodb = boto3.resource('dynamodb')
            table = dynamodb.Table(table)
        self.table = table

        self.cookie_name = cookie_name
        self.max_age = int(max_age) if max_age is not None else None
        self.path = path
        self.domain = domain
        self.secure = secure
        self.httponly = httponly
        self.samesite = samesite
        self.timeout = int(timeout) if timeout is not None else None
        self.reissue_time = (
            int(reissue_time) if reissue_time is not None else None
        )

    def __call__(self, request):
        session = self._load(request)
        callback = functools.partial(self._response_callback, session)
        request.add_response_callback(callback)
        return session

    def _hashed_id(self, session_id):
        return hashlib.sha256(session_id.encode('utf8')).digest()

    def _load(self, request):
        cookie_val = request.cookies.get(self.cookie_name)
        if not cookie_val:
            return DynamoDBSession.new_session()
        split = cookie_val.split('/')
        if len(split) < 2:
            return DynamoDBSession.new_session()
        session_id = split[0]
        version = Decimal(split[1])
        r = self.table.get_item(
            Key={'sid': self._hashed_id(session_id)},
            ConsistentRead=False,
        )
        if 'Item' not in r or r['Item']['ver'] < version:
            # If read fails, try again as a consistent read.
            r = self.table.get_item(
                Key={'sid': self._hashed_id(session_id)},
                ConsistentRead=True,
            )
        if 'Item' not in r:
            return DynamoDBSession.new_session()
        if r['Item']['exp'] < time():
            return DynamoDBSession.new_session()
        version = r['Item']['ver']
        issued_at = int(r['Item']['iss'])
        state = json.loads(r['Item']['dat'])
        return DynamoDBSession(session_id, state, version, issued_at)

    def _response_callback(self, session, request, response):
        if session.dirty:
            if session.new:
                self._create(session)
            else:
                self._update(session)
            self._set_cookie(request, response, session)
        elif not session.new and (
            self.reissue_time is None
            or time() - session.issued_at > self.reissue_time
        ):
            self._reissue(session)
            self._set_cookie(request, response, session)

    def _set_cookie(self, request, response, session):
        val = '/'.join([
            session.session_id,
            str(session.version),
        ])
        if self.secure is None:
            secure = request.scheme == 'https'
        else:
            secure = self.secure
        response.set_cookie(
            self.cookie_name,
            value=val,
            max_age=self.max_age,
            path=self.path,
            domain=self.domain,
            secure=secure,
            httponly=self.httponly,
            samesite=self.samesite,
        )

    def _update(self, session):
        old_version = session.version
        session.version += 1
        session.issued_at = Decimal(int(time()))
        try:
            self.table.put_item(
                Item={
                    'sid': self._hashed_id(session.session_id),
                    'dat': json.dumps(session.state),
                    'ver': session.version,
                    'iss': session.issued_at,
                    'exp': session.issued_at + self.timeout,
                },
                Expected={
                    'ver': {'Value': old_version},
                },
            )
        except(
                self.table.meta.client.exceptions
                .ConditionalCheckFailedException
        ):
            raise RaceConditionException(
                'Session was updated since last read.'
            )

    def _create(self, session):
        session.session_id = secrets.token_urlsafe()
        session.version = Decimal('1')
        session.issued_at = Decimal(int(time()))
        self.table.put_item(
            Item={
                'sid': self._hashed_id(session.session_id),
                'dat': json.dumps(session.state),
                'ver': session.version,
                'iss': session.issued_at,
                'exp': session.issued_at + self.timeout,
            },
            Expected={
                'sid': {'Exists': False},
            },
        )

    def _reissue(self, session):
        self.table.update_item(
            Key={'sid': self._hashed_id(session.session_id)},
            AttributeUpdates={
                'iss': {'Value': int(time())},
                'exp': {'Value': int(time()) + self.timeout},
            },
        )


def proxy(func):
    "Proxy dict functions to state dictionary."
    @functools.wraps(func)
    def wrapped(self, *args, **kwargs):
        return func(self.state, *args, **kwargs)

    return wrapped


def proxy_persist(func):
    "Proxy dict functions and mark session as dirty."
    @functools.wraps(func)
    def wrapped(self, *args, **kwargs):
        self.dirty = True
        return func(self.state, *args, **kwargs)

    return wrapped


@implementer(ISession)
class DynamoDBSession:
    def __init__(self, session_id, state, version, issued_at):
        self.session_id = session_id
        self.version = version
        self.issued_at = issued_at
        self.state = state
        self.dirty = False

    @classmethod
    def new_session(cls):
        return cls(None, dict(), None, None)

    @property
    def new(self):
        return self.session_id is None

    def changed(self):
        self.dirty = True

    def invalidate(self):
        self.dirty = True
        self.state = dict()

    # non-modifying dictionary methods
    get = proxy(dict.get)
    __getitem__ = proxy(dict.__getitem__)
    items = proxy(dict.items)
    values = proxy(dict.values)
    keys = proxy(dict.keys)
    __contains__ = proxy(dict.__contains__)
    __len__ = proxy(dict.__len__)
    __iter__ = proxy(dict.__iter__)

    # modifying dictionary methods
    clear = proxy_persist(dict.clear)
    update = proxy_persist(dict.update)
    setdefault = proxy_persist(dict.setdefault)
    pop = proxy_persist(dict.pop)
    popitem = proxy_persist(dict.popitem)
    __setitem__ = proxy_persist(dict.__setitem__)
    __delitem__ = proxy_persist(dict.__delitem__)

    # flash API methods
    def flash(self, msg, queue='', allow_duplicate=True):
        storage = self.setdefault('_f_' + queue, [])
        if allow_duplicate or (msg not in storage):
            storage.append(msg)

    def pop_flash(self, queue=''):
        # We check if the queue is in the session first, because we don't want
        # to needlessly mutate the session.
        name = '_f_' + queue
        if name in self:
            return self.pop(name)
        else:
            return []

    def peek_flash(self, queue=''):
        return self.get('_f_' + queue, [])

    # CSRF API methods
    def new_csrf_token(self):
        token = secrets.token_hex()
        self['_csrft_'] = token
        return token

    def get_csrf_token(self):
        token = self.get('_csrft_', None)
        if token is None:
            token = self.new_csrf_token()
        return token

import functools
import hashlib
import json
import secrets
from decimal import Decimal
from time import time

import boto3
from pyramid.interfaces import ISession, ISessionFactory
from zope.interface import implementer


class RaceConditionException(Exception):
    pass


@implementer(ISessionFactory)
class DynamoDBSessionFactory:
    def __init__(
            self,
            table,
            cookie_name='session_id',
            max_age=None,
            path='/',
            domain=None,
            secure=None,
            httponly=True,
            samesite='Strict',
            timeout=1200,
            reissue_time=120,
    ):
        """
    A Pyramid session factory which will provide DynamoDB-backed
    sessions.

    The DynamoDB table must have a hash key ``sid`` of binary (B) type and a
    time-to-live on the ``exp`` attribute.

    :param table:  The DynamoDB table to use.  Can be a string or a boto3 Table
        object.
    :type table:  ``str`` or ``Table``
    :param cookie_name:  The name of the cookie used to store the session ID.
        Defaults to ``session_id``.
    :type cookie_name: str
    :param max_age:  The expiration time for the cookie in seconds.  Defaults
        to ``None`` (session-only cookie).
    :type max_age:  int
    :param path:  The path for the cookie.  Defaults to ``/``.
    :type path:  str
    :param domain:  The domain for the cookie.  Defaults to no domain.
    :type domain:  str
    :param secure:  If true, sets the ``secure`` flag for the cookie.  Defaults
        to ``None``, which will set the flag if the request is made via HTTPS.
    :type secure:  bool
    :param httponly:  If true, hide the cookie from Javascript by setting the
        ``HttpOnly`` flag.  Defaults to true.
    :type httponly:  bool
    :param samesite:  The SameSite property for the cookie, or ``None`` to
        disable the SameSite option.  Defaults to ``Strict``.
    :type samesite:  str
    :param timeout:  The number of seconds of inactivity before the session
        times out.  Defaults to ``1200``.  (20 minutes)
    :type timeout:  int
    :param reissue_time:  The number of seconds before the session is
        "reissued," meaning that the activity timeout is reset.  Reissuing
        performs a write to DynamoDB, so it is recommended to set this to a
        reasonably high value, such as 1/10 of the timeout.  Defaults to
        ``120``.  (2 minutes)
    :type reissue_time:  int

    """
        if isinstance(table, str):
            dynamodb = boto3.resource('dynamodb')
            table = dynamodb.Table(table)
        self.table = table

        self.cookie_name = cookie_name
        self.max_age = int(max_age) if max_age is not None else None
        self.path = path
        self.domain = domain
        self.secure = secure
        self.httponly = httponly
        self.samesite = samesite
        self.timeout = int(timeout) if timeout is not None else None
        self.reissue_time = (
            int(reissue_time) if reissue_time is not None else None
        )

    def __call__(self, request):
        session = self._load(request)
        callback = functools.partial(self._response_callback, session)
        request.add_response_callback(callback)
        return session

    def _hashed_id(self, session_id):
        return hashlib.sha256(session_id.encode('utf8')).digest()

    def _load(self, request):
        cookie_val = request.cookies.get(self.cookie_name)
        if not cookie_val:
            return DynamoDBSession.new_session()
        split = cookie_val.split('/')
        if len(split) < 2:
            return DynamoDBSession.new_session()
        session_id = split[0]
        version = Decimal(split[1])
        r = self.table.get_item(
            Key={'sid': self._hashed_id(session_id)},
            ConsistentRead=False,
        )
        if 'Item' not in r or r['Item']['ver'] < version:
            # If read fails, try again as a consistent read.
            r = self.table.get_item(
                Key={'sid': self._hashed_id(session_id)},
                ConsistentRead=True,
            )
        if 'Item' not in r:
            return DynamoDBSession.new_session()
        if r['Item']['exp'] < time():
            return DynamoDBSession.new_session()
        version = r['Item']['ver']
        issued_at = int(r['Item']['iss'])
        state = json.loads(r['Item']['dat'])
        return DynamoDBSession(session_id, state, version, issued_at)

    def _response_callback(self, session, request, response):
        if session.dirty:
            if session.new:
                self._create(session)
            else:
                self._update(session)
            self._set_cookie(request, response, session)
        elif not session.new and (
            self.reissue_time is None
            or time() - session.issued_at > self.reissue_time
        ):
            self._reissue(session)
            self._set_cookie(request, response, session)

    def _set_cookie(self, request, response, session):
        val = '/'.join([
            session.session_id,
            str(session.version),
        ])
        if self.secure is None:
            secure = request.scheme == 'https'
        else:
            secure = self.secure
        response.set_cookie(
            self.cookie_name,
            value=val,
            max_age=self.max_age,
            path=self.path,
            domain=self.domain,
            secure=secure,
            httponly=self.httponly,
            samesite=self.samesite,
        )

    def _update(self, session):
        old_version = session.version
        session.version += 1
        session.issued_at = Decimal(int(time()))
        try:
            self.table.put_item(
                Item={
                    'sid': self._hashed_id(session.session_id),
                    'dat': json.dumps(session.state),
                    'ver': session.version,
                    'iss': session.issued_at,
                    'exp': session.issued_at + self.timeout,
                },
                Expected={
                    'ver': {'Value': old_version},
                },
            )
        except(
                self.table.meta.client.exceptions
                .ConditionalCheckFailedException
        ):
            raise RaceConditionException(
                'Session was updated since last read.'
            )

    def _create(self, session):
        session.session_id = secrets.token_urlsafe()
        session.version = Decimal('1')
        session.issued_at = Decimal(int(time()))
        self.table.put_item(
            Item={
                'sid': self._hashed_id(session.session_id),
                'dat': json.dumps(session.state),
                'ver': session.version,
                'iss': session.issued_at,
                'exp': session.issued_at + self.timeout,
            },
            Expected={
                'sid': {'Exists': False},
            },
        )

    def _reissue(self, session):
        self.table.update_item(
            Key={'sid': self._hashed_id(session.session_id)},
            AttributeUpdates={
                'iss': {'Value': int(time())},
                'exp': {'Value': int(time()) + self.timeout},
            },
        )


def proxy(func):
    "Proxy dict functions to state dictionary."
    @functools.wraps(func)
    def wrapped(self, *args, **kwargs):
        return func(self.state, *args, **kwargs)

    return wrapped


def proxy_persist(func):
    "Proxy dict functions and mark session as dirty."
    @functools.wraps(func)
    def wrapped(self, *args, **kwargs):
        self.dirty = True
        return func(self.state, *args, **kwargs)

    return wrapped


@implementer(ISession)
class DynamoDBSession:
    def __init__(self, session_id, state, version, issued_at):
        self.session_id = session_id
        self.version = version
        self.issued_at = issued_at
        self.state = state
        self.dirty = False

    @classmethod
    def new_session(cls):
        return cls(None, dict(), None, None)

    @property
    def new(self):
        return self.session_id is None

    def changed(self):
        self.dirty = True

    def invalidate(self):
        self.dirty = True
        self.state = dict()

    # non-modifying dictionary methods
    get = proxy(dict.get)
    __getitem__ = proxy(dict.__getitem__)
    items = proxy(dict.items)
    values = proxy(dict.values)
    keys = proxy(dict.keys)
    __contains__ = proxy(dict.__contains__)
    __len__ = proxy(dict.__len__)
    __iter__ = proxy(dict.__iter__)

    # modifying dictionary methods
    clear = proxy_persist(dict.clear)
    update = proxy_persist(dict.update)
    setdefault = proxy_persist(dict.setdefault)
    pop = proxy_persist(dict.pop)
    popitem = proxy_persist(dict.popitem)
    __setitem__ = proxy_persist(dict.__setitem__)
    __delitem__ = proxy_persist(dict.__delitem__)

    # flash API methods
    def flash(self, msg, queue='', allow_duplicate=True):
        storage = self.setdefault('_f_' + queue, [])
        if allow_duplicate or (msg not in storage):
            storage.append(msg)

    def pop_flash(self, queue=''):
        # We check if the queue is in the session first, because we don't want
        # to needlessly mutate the session.
        name = '_f_' + queue
        if name in self:
            return self.pop(name)
        else:
            return []

    def peek_flash(self, queue=''):
        return self.get('_f_' + queue, [])

    # CSRF API methods
    def new_csrf_token(self):
        token = secrets.token_hex()
        self['_csrft_'] = token
        return token

    def get_csrf_token(self):
        token = self.get('_csrft_', None)
        if token is None:
            token = self.new_csrf_token()
        return token
A Pyramid session factory which will provide DynamoDB-backed     sessions.      The DynamoDB table must have a hash key ``sid`` of binary (B) type and a     time-to-live on the ``exp`` attribute.      :param table:  The DynamoDB table to use.  Can be a string or a boto3 Table         object.     :type table:  ``str`` or ``Table``     :param cookie_name:  The name of the cookie used to store the session ID.         Defaults to ``session_id``.     :type cookie_name: str     :param max_age:  The expiration time for the cookie in seconds.  Defaults         to ``None`` (session-only cookie).     :type max_age:  int     :param path:  The path for the cookie.  Defaults to ``/``.     :type path:  str     :param domain:  The domain for the cookie.  Defaults to no domain.     :type domain:  str     :param secure:  If true, sets the ``secure`` flag for the cookie.  Defaults         to ``None``, which will set the flag if the request is made via HTTPS.     :type secure:  bool     :param httponly:  If true, hide the cookie from Javascript by setting the         ``HttpOnly`` flag.  Defaults to true.     :type httponly:  bool     :param samesite:  The SameSite property for the cookie, or ``None`` to         disable the SameSite option.  Defaults to ``Strict``.     :type samesite:  str     :param timeout:  The number of seconds of inactivity before the session         times out.  Defaults to ``1200``.  (20 minutes)     :type timeout:  int     :param reissue_time:  The number of seconds before the session is         "reissued," meaning that the activity timeout is reset.  Reissuing         performs a write to DynamoDB, so it is recommended to set this to a         reasonably high value, such as 1/10 of the timeout.  Defaults to         ``120``.  (2 minutes)     :type reissue_time:  int # If read fails, try again as a consistent read. # non-modifying dictionary methods # modifying dictionary methods # flash API methods # We check if the queue is in the session first, because we don't want # to needlessly mutate the session. # CSRF API methods