#### Anti-spam ruleset ###########################################
#
# This script provides some foundational anti-spam rules. It aims
# to PASS stanzas that are definitely not spam, and DROP stanzas
# that are very likely spam.
#
# It does not do any form of content filtering,
# but this can be implemented by other scripts and
# modules as desired using the chains documented below.
#
#
# The following chains are available as extension
# points:
#
# ::user/spam_check_custom
#   Apply additional rules to all stanzas before they are checked.
#   Mainly useful to PASS stanzas that you do not want to be
#   filtered.
#
# ::user/spam_check_message_custom
#   Apply additional rules to messages from strangers, aiming to
#   PASS stanzas that are not spam and jump to ::user/spam_reject
#   for stanzas that are considered spam.
#
# ::user/spam_check_message_content_custom
#   Apply additional rules to messages that may be spam, based on
#   message content rules. These may contain more intensive rules,
#   so are executed after all other checks. Rules should jump to
#   ::user/spam_reject if a message is considered spam.
#
# ::user/spam_check_presence_custom
#   Apply additional rules to presence that may be spam.
#
# ::user/spam_check_subscription_request_custom
#   Apply additional rules to subscription requests.
#
# ::user/spam_handle_unknown_custom
#   Override default handling of stanzas that weren't explicitly
#   passed or rejected by the anti-spam checks.
#
# ::user/spam_reject_custom
#   Override default handling of stanzas that have
#   been recognised as spam (default is to bounce
#   a policy-violation error). 
#
##################################################################

#### Entry point for all incoming stanzas ########################
::deliver

# Override this if you want to prevent certain stanzas going through
# the normal spam_check chain
JUMP_CHAIN=user/spam_check_custom

# Run the default spam_check chain
JUMP_CHAIN=user/spam_check

##################################################################

#### General spam-checking rules (all stanzas) ###################
::user/spam_check

# Pass stanzas that a user sends to their own account
TO SELF?
PASS.

# Pass stanzas that are addressed to a valid full JID
TO FULL JID?
PASS.

# Pass stanzas from contacts
SUBSCRIBED?
PASS.

# Run extra rules that apply to messages only
KIND: message
JUMP CHAIN=user/spam_check_message

# Run extra rules that apply to presence stanzas only
KIND: presence
JUMP CHAIN=user/spam_check_presence

JUMP CHAIN=user/spam_handle_unknown

# Default is to allow, override this with
# the 'user/spam_handle_unknown' chain
PASS.

#### Rules for messages ##########################################
::user/spam_check_message

JUMP CHAIN=user/spam_check_message_custom

# Type 'groupchat' messages addressed to an offline full JID are harmless,
# and should be routed normally to handle MUC 'ghosts' correctly
TO: <*>@<*>/<*>
TYPE: groupchat
PASS.

# Mediated MUC invitations are naturally from 'strangers' and have special
# handling. We lean towards accepting them, unless overridden by custom rules.
NOT FROM FULL JID?
INSPECT: {http://jabber.org/protocol/muc#user}x/invite
JUMP CHAIN=user/spam_check_muc_invite

# Non-chat message types often generate pop-ups in clients,
# so we won't accept them from strangers
NOT TYPE: chat
JUMP CHAIN=user/spam_reject

JUMP CHAIN=user/spam_check_message_content

# This chain can be used by other scripts
# and modules that analyze message content
JUMP CHAIN=user/spam_check_message_content_custom

##################################################################

#### Rules for presence stanzas ##################################
::user/spam_check_presence

JUMP CHAIN=user/spam_check_presence_custom

# Presence to offline full JIDs is harmless, and should be routed
# normally to handle MUC 'ghosts' correctly
TO: <*>@<*>/<*>
PASS.

# These may be received if rosters get out of sync and are harmless
# because they will not be routed to the client unless necessary
TYPE: unsubscribe|unsubscribed
PASS.

# We don't want to receive presence from random strangers,
# but still allow subscription requests
NOT TYPE: subscribe|subscribed
DROP.

# This chain can be used by other scripts
# and modules to filter subscription requests
JUMP CHAIN=user/spam_check_subscription_request

JUMP CHAIN=user/spam_check_subscription_request_custom

##################################################################

#### Rules for MUC invitations ###################################

::user/spam_check_muc_invite

# This chain can be used to inspect the invitation and determine
# the appropriate action. Otherwise, we proceed with the default
# action below.
JUMP CHAIN=user/spam_check_muc_invite_custom

# Allow mediated MUC invitations by default
PASS.

#### Stanzas reaching this chain will be rejected ################
::user/spam_reject

# This chain can be used by other scripts
# and modules to override the default behaviour
# when rejecting spam stanzas
JUMP CHAIN=user/spam_reject_custom

LOG=Rejecting suspected spam: $(stanza:top_tag())
BOUNCE=policy-violation

##################################################################

#### Stanzas that may be spam, but we're not sure either way #####
::user/spam_handle_unknown

# This chain can be used by other scripts
# and modules to apply additional checks, or to
# override the default behaviour
JUMP CHAIN=user/spam_handle_unknown_custom

#LOG=[debug] Spam check allowing: $(stanza:top_tag())

##################################################################