evennia/lib/locks/lockfuncs.py

"""
This module provides a set of permission lock functions for use
with Evennia's permissions system.

To call these locks, make sure this module is included in the
settings tuple PERMISSION_FUNC_MODULES then define a lock on the form
'<access_type>:func(args)' and add it to the object's lockhandler.
Run the access() method of the handler to execute the lock check.

Note that accessing_obj and accessed_obj can be any object type
with a lock variable/field, so be careful to not expect
a certain object type.


Appendix: MUX locks

Below is a list nicked from the MUX help file on the locks available
in standard MUX. Most of these are not relevant to core Evennia since
locks in Evennia are considerably more flexible and can be implemented
on an individual command/typeclass basis rather than as globally
available like the MUX ones. So many of these are not available in
basic Evennia, but could all be implemented easily if needed for the
individual game.

MUX Name:      Affects:        Effect:
-------------------------------------------------------------------------------
DefaultLock:   Exits:          controls who may traverse the exit to
                               its destination.
                                 Evennia: "traverse:<lockfunc()>"
               Rooms:          controls whether the player sees the SUCC
                               or FAIL message for the room following the
                               room description when looking at the room.
                                 Evennia: Custom typeclass
               Players/Things: controls who may GET the object.
                                 Evennia: "get:<lockfunc()"
 EnterLock:    Players/Things: controls who may ENTER the object
                                 Evennia:
 GetFromLock:  All but Exits:  controls who may gets things from a given
                               location.
                                 Evennia:
 GiveLock:     Players/Things: controls who may give the object.
                                 Evennia:
 LeaveLock:    Players/Things: controls who may LEAVE the object.
                                 Evennia:
 LinkLock:     All but Exits:  controls who may link to the location if the
                               location is LINK_OK (for linking exits or
                               setting drop-tos) or ABODE (for setting
                               homes)
                                 Evennia:
 MailLock:     Players:        controls who may @mail the player.
                               Evennia:
 OpenLock:     All but Exits:  controls who may open an exit.
                                 Evennia:
 PageLock:     Players:        controls who may page the player.
                                 Evennia: "send:<lockfunc()>"
 ParentLock:   All:            controls who may make @parent links to the
                               object.
                                 Evennia: Typeclasses and "puppet:<lockstring()>"
 ReceiveLock:  Players/Things: controls who may give things to the object.
                                 Evennia:
 SpeechLock:   All but Exits:  controls who may speak in that location
                                 Evennia:
 TeloutLock:   All but Exits:  controls who may teleport out of the
                               location.
                                 Evennia:
 TportLock:    Rooms/Things:   controls who may teleport there
                                 Evennia:
 UseLock:      All but Exits:  controls who may USE the object, GIVE the
                               object money and have the PAY attributes
                               run, have their messages heard and possibly
                               acted on by LISTEN and AxHEAR, and invoke
                               $-commands stored on the object.
                                 Evennia: Commands and Cmdsets.
 DropLock:     All but rooms:  controls who may drop that object.
                                 Evennia:
 VisibleLock:  All:            Controls object visibility when the object
                               is not dark and the looker passes the lock.
                               In DARK locations, the object must also be
                               set LIGHT and the viewer must pass the
                               VisibleLock.
                                 Evennia: Room typeclass with Dark/light script
"""

from django.conf import settings
from src.utils import utils

_PERMISSION_HIERARCHY = [p.lower() for p in settings.PERMISSION_HIERARCHY]


def _to_player(accessing_obj):
    "Helper function. Makes sure an accessing object is a player object"
    if utils.inherits_from(accessing_obj, "src.objects.objects.Object"):
        # an object. Convert to player.
        accessing_obj = accessing_obj.player
    return accessing_obj


# lock functions

def true(*args, **kwargs):
    "Always returns True."
    return True


def all(*args, **kwargs):
    return True


def false(*args, **kwargs):
    "Always returns False"
    return False


def none(*args, **kwargs):
    return False


def self(accessing_obj, accessed_obj, *args, **kwargs):
    """
    Check if accessing_obj is the same as accessed_obj

    Usage:
       self()

    This can be used to lock specifically only to
    the same object that the lock is defined on.
    """
    return accessing_obj == accessed_obj


def perm(accessing_obj, accessed_obj, *args, **kwargs):
    """
    The basic permission-checker. Ignores case.

    Usage:
       perm(<permission>)

    where <permission> is the permission accessing_obj must
    have in order to pass the lock.

    If the given permission is part of settings.PERMISSION_HIERARCHY,
    permission is also granted to all ranks higher up in the hierarchy.

    If accessing_object is an Object controlled by a Player, the
    permissions of the Player is used unless the Attribute _quell
    is set to True on the Object. In this case however, the
    LOWEST hieararcy-permission of the Player/Object-pair will be used
    (this is order to avoid Players potentially escalating their own permissions
    by use of a higher-level Object)

    """
    # this allows the perm_above lockfunc to make use of this function too
    gtmode = kwargs.pop("_greater_than", False)

    try:
        perm = args[0].lower()
        perms_object = [p.lower() for p in accessing_obj.permissions.all()]
    except (AttributeError, IndexError):
        return False

    if utils.inherits_from(accessing_obj, "src.objects.objects.Object") and accessing_obj.player:
        player = accessing_obj.player
        perms_player = [p.lower() for p in player.permissions.all()]
        is_quell = player.attributes.get("_quell")

        if perm in _PERMISSION_HIERARCHY:
            # check hierarchy without allowing escalation obj->player
            hpos_target = _PERMISSION_HIERARCHY.index(perm)
            hpos_player = [hpos for hpos, hperm in enumerate(_PERMISSION_HIERARCHY) if hperm in perms_player]
            hpos_player = hpos_player and hpos_player[-1] or -1
            if is_quell:
                hpos_object = [hpos for hpos, hperm in enumerate(_PERMISSION_HIERARCHY) if hperm in perms_object]
                hpos_object = hpos_object and hpos_object[-1] or -1
                if gtmode:
                    return hpos_target < min(hpos_player, hpos_object)
                else:
                    return hpos_target <= min(hpos_player, hpos_object)
            elif gtmode:
                return gtmode and hpos_target < hpos_player
            else:
                return hpos_target <= hpos_player
        elif not is_quell and perm in perms_player:
            # if we get here, check player perms first, otherwise
            # continue as normal
            return True

    if perm in perms_object:
        # simplest case - we have direct match
        return True
    if perm in _PERMISSION_HIERARCHY:
        # check if we have a higher hierarchy position
        hpos_target = _PERMISSION_HIERARCHY.index(perm)
        return any(1 for hpos, hperm in enumerate(_PERMISSION_HIERARCHY)
                   if hperm in perms_object and hpos_target < hpos)
    return False


def perm_above(accessing_obj, accessed_obj, *args, **kwargs):
    """
    Only allow objects with a permission *higher* in the permission
    hierarchy than the one given. If there is no such higher rank,
    it's assumed we refer to superuser. If no hierarchy is defined,
    this function has no meaning and returns False.
    """
    kwargs["_greater_than"] = True
    return perm(accessing_obj, accessed_obj, *args, **kwargs)


def pperm(accessing_obj, accessed_obj, *args, **kwargs):
    """
    The basic permission-checker only for Player objects. Ignores case.

    Usage:
       pperm(<permission>)

    where <permission> is the permission accessing_obj must
    have in order to pass the lock. If the given permission
    is part of _PERMISSION_HIERARCHY, permission is also granted
    to all ranks higher up in the hierarchy.
    """
    return perm(_to_player(accessing_obj), accessed_obj, *args, **kwargs)


def pperm_above(accessing_obj, accessed_obj, *args, **kwargs):
    """
    Only allow Player objects with a permission *higher* in the permission
    hierarchy than the one given. If there is no such higher rank,
    it's assumed we refer to superuser. If no hierarchy is defined,
    this function has no meaning and returns False.
    """
    return perm_above(_to_player(accessing_obj), accessed_obj, *args, **kwargs)


def dbref(accessing_obj, accessed_obj, *args, **kwargs):
    """
    Usage:
      dbref(3)

    This lock type checks if the checking object
    has a particular dbref. Note that this only
    works for checking objects that are stored
    in the database (e.g. not for commands)
    """
    if not args:
        return False
    try:
        dbref = int(args[0].strip().strip('#'))
    except ValueError:
        return False
    if hasattr(accessing_obj, 'dbid'):
        return dbref == accessing_obj.dbid
    return False


def pdbref(accessing_obj, accessed_obj, *args, **kwargs):
    """
    Same as dbref, but making sure accessing_obj is a player.
    """
    return dbref(_to_player(accessing_obj), accessed_obj, *args, **kwargs)


def id(accessing_obj, accessed_obj, *args, **kwargs):
    "Alias to dbref"
    return dbref(accessing_obj, accessed_obj, *args, **kwargs)


def pid(accessing_obj, accessed_obj, *args, **kwargs):
    "Alias to dbref, for Players"
    return dbref(_to_player(accessing_obj), accessed_obj, *args, **kwargs)


# this is more efficient than multiple if ... elif statments
CF_MAPPING = {'eq': lambda val1, val2: val1 == val2 or int(val1) == int(val2),
              'gt': lambda val1, val2: int(val1) > int(val2),
              'lt': lambda val1, val2: int(val1) < int(val2),
              'ge': lambda val1, val2: int(val1) >= int(val2),
              'le': lambda val1, val2: int(val1) <= int(val2),
              'ne': lambda val1, val2: int(val1) != int(val2),
              'default': lambda val1, val2: False}


def attr(accessing_obj, accessed_obj, *args, **kwargs):
    """
    Usage:
      attr(attrname)
      attr(attrname, value)
      attr(attrname, value, compare=type)

    where compare's type is one of (eq,gt,lt,ge,le,ne) and signifies
    how the value should be compared with one on accessing_obj (so
    compare=gt means the accessing_obj must have a value greater than
    the one given).

    Searches attributes *and* properties stored on the checking
    object. The first form works like a flag - if the
    attribute/property exists on the object, the value is checked for
    True/False. The second form also requires that the value of the
    attribute/property matches. Note that all retrieved values will be
    converted to strings before doing the comparison.
    """
    # deal with arguments
    if not args:
        return False
    attrname = args[0].strip()
    value = None
    if len(args) > 1:
        value = args[1].strip()
    compare = 'eq'
    if kwargs:
        compare = kwargs.get('compare', 'eq')

    def valcompare(val1, val2, typ='eq'):
        "compare based on type"
        try:
            return CF_MAPPING.get(typ, 'default')(val1, val2)
        except Exception:
            # this might happen if we try to compare two things
            # that cannot be compared
            return False

    # first, look for normal properties on the object trying to gain access
    if hasattr(accessing_obj, attrname):
        if value:
            return valcompare(str(getattr(accessing_obj, attrname)), value, compare)
        # will return Fail on False value etc
        return bool(getattr(accessing_obj, attrname))
    # check attributes, if they exist
    if (hasattr(accessing_obj, 'attributes') and accessing_obj.attributes.has(attrname)):
        if value:
            return (hasattr(accessing_obj, 'attributes')
                    and valcompare(accessing_obj.attributes.get(attrname), value, compare))
        # fails on False/None values
        return bool(accessing_obj.attributes.get(attrname))
    return False


def objattr(accessing_obj, accessed_obj, *args, **kwargs):
    """
    Usage:
      objattr(attrname)
      objattr(attrname, value)
      objattr(attrname, value, compare=type)

    Works like attr, except it looks for an attribute on
    accessing_obj.obj, if such an entity exists. Suitable
    for commands.

    """
    if hasattr(accessing_obj, "obj"):
        return attr(accessing_obj.obj, accessed_obj, *args, **kwargs)


def locattr(accessing_obj, accessed_obj, *args, **kwargs):
    """
    Usage:
      locattr(attrname)
      locattr(attrname, value)
      locattr(attrname, value, compare=type)

    Works like attr, except it looks for an attribute on
    accessing_obj.location, if such an entity exists.

    """
    if hasattr(accessing_obj, "location"):
        return attr(accessing_obj.location, accessed_obj, *args, **kwargs)


def attr_eq(accessing_obj, accessed_obj, *args, **kwargs):
    """
    Usage:
       attr_gt(attrname, 54)
    """
    return attr(accessing_obj, accessed_obj, *args, **kwargs)


def attr_gt(accessing_obj, accessed_obj, *args, **kwargs):
    """
    Usage:
       attr_gt(attrname, 54)

    Only true if access_obj's attribute > the value given.
    """
    return attr(accessing_obj, accessed_obj, *args, **{'compare': 'gt'})


def attr_ge(accessing_obj, accessed_obj, *args, **kwargs):
    """
    Usage:
       attr_gt(attrname, 54)

    Only true if access_obj's attribute >= the value given.
    """
    return attr(accessing_obj, accessed_obj, *args, **{'compare': 'ge'})


def attr_lt(accessing_obj, accessed_obj, *args, **kwargs):
    """
    Usage:
       attr_gt(attrname, 54)

    Only true if access_obj's attribute < the value given.
    """
    return attr(accessing_obj, accessed_obj, *args, **{'compare': 'lt'})


def attr_le(accessing_obj, accessed_obj, *args, **kwargs):
    """
    Usage:
       attr_gt(attrname, 54)

    Only true if access_obj's attribute <= the value given.
    """
    return attr(accessing_obj, accessed_obj, *args, **{'compare': 'le'})


def attr_ne(accessing_obj, accessed_obj, *args, **kwargs):
    """
    Usage:
       attr_gt(attrname, 54)

    Only true if access_obj's attribute != the value given.
    """
    return attr(accessing_obj, accessed_obj, *args, **{'compare': 'ne'})


def inside(accessing_obj, accessed_obj, *args, **kwargs):
    """
    Usage:
       inside()

    Only true if accessing_obj is "inside" accessed_obj
    """
    return accessing_obj.location == accessed_obj


def holds(accessing_obj, accessed_obj, *args, **kwargs):
    """
    Usage:
      holds()            checks if accessed_obj or accessed_obj.obj
                         is held by accessing_obj
      holds(key/dbref)   checks if accessing_obj holds an object
                          with given key/dbref
      holds(attrname, value)   checks if accessing_obj holds an
                               object with the given attrname and value

    This is passed if accessed_obj is carried by accessing_obj (that is,
    accessed_obj.location == accessing_obj), or if accessing_obj itself holds
    an object matching the given key.
    """
    try:
        # commands and scripts don't have contents, so we are usually looking
        # for the contents of their .obj property instead (i.e. the object the
        # command/script is attached to).
        contents = accessing_obj.contents
    except AttributeError:
        try:
            contents = accessing_obj.obj.contents
        except AttributeError:
            return False

    def check_holds(objid):
        # helper function. Compares both dbrefs and keys/aliases.
        objid = str(objid)
        dbref = utils.dbref(objid, reqhash=False)
        if dbref and any((True for obj in contents if obj.dbid == dbref)):
            return True
        objid = objid.lower()
        return any((True for obj in contents
                    if obj.key.lower() == objid or objid in [al.lower() for al in obj.aliases.all()]))
    if not args:
        # holds() - check if accessed_obj or accessed_obj.obj is held by accessing_obj
        try:
            if check_holds(accessed_obj.dbid):
                return True
        except Exception:
            pass
        return hasattr(accessed_obj, "obj") and check_holds(accessed_obj.obj.dbid)
    if len(args) == 1:
        # command is holds(dbref/key) - check if given objname/dbref is held by accessing_ob
        return check_holds(args[0])
    elif len(args = 2):
        # command is holds(attrname, value) check if any held object has the given attribute and value
        for obj in contents:
            if obj.attributes.get(args[0]) == args[1]:
                return True


def superuser(*args, **kwargs):
    """
    Only accepts an accesing_obj that is superuser (e.g. user #1)

    Since a superuser would not ever reach this check (superusers
    bypass the lock entirely), any user who gets this far cannot be a
    superuser, hence we just return False. :)
    """
    return False


def serversetting(accessing_obj, accessed_obj, *args, **kwargs):
    """
    Only returns true if the Evennia settings exists, alternatively has
    a certain value.

    Usage:
      serversetting(IRC_ENABLED)
      serversetting(BASE_SCRIPT_PATH, [game.gamesrc.scripts])

    A given True/False or integers will be converted properly.
    """
    if not args or not args[0]:
        return False
    if len(args) < 2:
        setting = args[0]
        val = "True"
    else:
        setting, val = args[0], args[1]
    # convert
    if val == 'True':
        val = True
    elif val == 'False':
        val = False
    elif val.isdigit():
        val = int(val)
    if setting in settings._wrapped.__dict__:
        return settings._wrapped.__dict__[setting] == val
    return False