File

-- XEP-0356 (Privileged Entity)
-- Copyright (C) 2015-2022 Jérôme Poisson
--
-- This module is MIT/X11 licensed. Please see the
-- COPYING file in the source package for more information.
--
-- Some parts come from mod_remote_roster (module by Waqas Hussain and Kim Alvefur, see https://code.google.com/p/prosody-modules/)

-- TODO: manage external <presence/> (for "roster" presence permission) when the account with the roster is offline

local jid = require("util.jid")
local set = require("util.set")
local st = require("util.stanza")
local roster_manager = require("core.rostermanager")
local usermanager_user_exists = require "core.usermanager".user_exists
local hosts = prosody.hosts
local full_sessions = prosody.full_sessions

local priv_session = module:shared("/*/privilege/session")

if priv_session.connected_cb == nil then
    -- set used to have connected event listeners
    -- which allows a host to react on events from
    -- other hosts
    priv_session.connected_cb = set.new()
end
local connected_cb = priv_session.connected_cb

-- the folowing sets are used to forward presence stanza
-- the folowing sets are used to forward presence stanza
local presence_man_ent = set.new()
local presence_roster = set.new()

local _ALLOWED_ROSTER = set.new({'none', 'get', 'set', 'both'})
local _ROSTER_GET_PERM = set.new({'get', 'both'})
local _ROSTER_SET_PERM = set.new({'set', 'both'})
local _ALLOWED_MESSAGE = set.new({'none', 'outgoing'})
local _ALLOWED_PRESENCE = set.new({'none', 'managed_entity', 'roster'})
local _PRESENCE_MANAGED = set.new({'managed_entity', 'roster'})
local _TO_CHECK = {roster=_ALLOWED_ROSTER, message=_ALLOWED_MESSAGE, presence=_ALLOWED_PRESENCE}
local _PRIV_ENT_NS = 'urn:xmpp:privilege:2'
local _FORWARDED_NS = 'urn:xmpp:forward:0'
local _MODULE_HOST = module:get_host()


module:log("debug", "Loading privileged entity module ")


--> Permissions management <--

local config_priv = module:get_option("privileged_entities", {})

local function get_session_privileges(session, host)
    if not session.privileges then return nil end
    return session.privileges[host]
end


local function advertise_perm(session, to_jid, perms)
    -- send <message/> stanza to advertise permissions
    -- as expained in § 4.2
    local message = st.message({from=module.host, to=to_jid})
                      :tag("privilege", {xmlns=_PRIV_ENT_NS})

    for _, perm in pairs({'roster', 'message', 'presence'}) do
        if perms[perm] then
            message:tag("perm", {access=perm, type=perms[perm]}):up()
        end
    end
    local iq_perm = perms["iq"]
    if iq_perm ~= nil then
        message:tag("perm", {access="iq"})
        for namespace, ns_perm in pairs(iq_perm) do
                local perm_type
                if ns_perm.set and ns_perm.get then
                    perm_type = "both"
                elseif ns_perm.set then
                    perm_type = "set"
                elseif ns_perm.get then
                    perm_type = "get"
                else
                    perm_type = nil
                end
                message:tag("namespace", {ns=namespace, type=perm_type})
        end
    end
    session.send(message)
end

local function set_presence_perm_set(to_jid, perms)
    -- fill the presence sets according to perms
    if _PRESENCE_MANAGED:contains(perms.presence) then
        presence_man_ent:add(to_jid)
    end
    if perms.presence == 'roster' then
        presence_roster:add(to_jid)
    end
end

local function advertise_presences(session, to_jid, perms)
    -- send presence status for already connected entities
    -- as explained in § 7.1
    -- people in roster are probed only for active sessions
    -- TODO: manage roster load for inactive sessions
    if not perms.presence then return; end
    local to_probe = {}
    for _, user_session in pairs(full_sessions) do
        if user_session.presence and _PRESENCE_MANAGED:contains(perms.presence) then
            local presence = st.clone(user_session.presence)
            presence.attr.to = to_jid
            module:log("debug", "sending current presence for "..tostring(user_session.full_jid))
            session.send(presence)
        end
        if perms.presence == "roster" then
            -- we reset the cache to avoid to miss a presence that just changed
            priv_session.last_presence = nil

            if user_session.roster then
                local bare_jid = jid.bare(user_session.full_jid)
                for entity, item in pairs(user_session.roster) do
                    if entity~=false and entity~="pending" and (item.subscription=="both" or item.subscription=="to") then
                        local _, host = jid.split(entity)
                        if not hosts[host] then -- we don't probe jid from hosts we manage
                            -- using a table with entity as key avoid probing several time the same one
                            to_probe[entity] = bare_jid
                        end
                    end
                end
            end
        end
    end

    -- now we probe peoples for "roster" presence permission
    for probe_to, probe_from in pairs(to_probe) do
        module:log("debug", "probing presence for %s (on behalf of %s)", tostring(probe_to), tostring(probe_from))
        local probe = st.presence({from=probe_from, to=probe_to, type="probe"})
        prosody.core_route_stanza(nil, probe)
    end
end


local function on_auth(event)
    -- Check if entity is privileged according to configuration,
    -- and set session.privileges accordingly

    local session = event.session
    local bare_jid = jid.join(session.username, session.host)
    if not session.privileges then
        session.privileges = {}
    end

    local conf_ent_priv = config_priv[bare_jid]
    local ent_priv = {}
    if conf_ent_priv ~= nil then
        module:log("debug", "Entity is privileged")
        for perm_type, allowed_values in pairs(_TO_CHECK) do
            local value = conf_ent_priv[perm_type]
            if value ~= nil then
                if not allowed_values:contains(value) then
                    module:log('warn', 'Invalid value for '..perm_type..' privilege: ['..value..']')
                    module:log('warn', 'Setting '..perm_type..' privilege to none')
                    ent_priv[perm_type] = nil
                elseif value == 'none' then
                    ent_priv[perm_type] = nil
                else
                    ent_priv[perm_type] = value
                end
            else
                ent_priv[perm_type] = nil
            end
        end
        -- extra checks for presence permission
        if ent_priv.presence == 'roster' and not _ROSTER_GET_PERM:contains(ent_priv.roster) then
            module:log("warn", "Can't allow roster presence privilege without roster \"get\" privilege")
            module:log("warn", "Setting presence permission to none")
            ent_priv.presence = nil
        end
        -- iq permission
        local iq_perm_config = conf_ent_priv["iq"]
        if iq_perm_config ~= nil then
            local iq_perm = {}
            ent_priv["iq"] = iq_perm
            for ns, ns_perm_config in pairs(iq_perm_config) do
                iq_perm[ns] = {
                    ["get"] = ns_perm_config == "get" or ns_perm_config == "both",
                    ["set"] = ns_perm_config == "set" or ns_perm_config == "both"
                }
            end
        else
            ent_priv["iq"] = nil
        end

        if session.type == "component" then
            -- we send the message stanza only for component
            -- it will be sent at first <presence/> for other entities
            advertise_perm(session, bare_jid, ent_priv)
            set_presence_perm_set(bare_jid, ent_priv)
            advertise_presences(session, bare_jid, ent_priv)
        end
    end

    session.privileges[_MODULE_HOST] = ent_priv
end

local function on_presence(event)
    -- Permission are already checked at this point,
    -- we only advertise them to the entity
    local session = event.origin
    local session_privileges = get_session_privileges(session, _MODULE_HOST)
    if session_privileges then
        advertise_perm(session, session.full_jid, session_privileges)
        set_presence_perm_set(session.full_jid, session_privileges)
        advertise_presences(session, session.full_jid, session_privileges)
    end
end

local function on_component_auth(event)
    -- react to component-authenticated event from this host
    -- and call the on_auth methods from all other hosts
    -- needed for the component to get delegations advertising
    for callback in connected_cb:items() do
        callback(event)
    end
end

if module:get_host_type() ~= "component" then
    connected_cb:add(on_auth)
end
module:hook('authentication-success', on_auth)
module:hook('component-authenticated', on_component_auth)
module:hook('presence/initial', on_presence)


--> roster permission <--

-- get
module:hook("iq-get/bare/jabber:iq:roster:query", function(event)
    local session, stanza = event.origin, event.stanza
    if not stanza.attr.to then
        -- we don't want stanzas addressed to /self
        return
    end
    local node, host = jid.split(stanza.attr.to)
    local session_privileges = get_session_privileges(session, host)

    if session_privileges and _ROSTER_GET_PERM:contains(session_privileges.roster) then
        module:log("debug", "Roster get from allowed privileged entity received")
        -- following code is adapted from mod_remote_roster
        local roster = roster_manager.load_roster(node, host)

        local reply = st.reply(stanza):query("jabber:iq:roster")
        for entity_jid, item in pairs(roster) do
            if entity_jid and entity_jid ~= "pending" then
                reply:tag("item", {
                    jid = entity_jid,
                    subscription = item.subscription,
                    ask = item.ask,
                    name = item.name,
                })
                for group in pairs(item.groups) do
                    reply:tag("group"):text(group):up()
                end
                reply:up(); -- move out from item
            end
        end
        -- end of code adapted from mod_remote_roster
        session.send(reply)
    else
        module:log("warn", "Entity "..tostring(session.full_jid).." try to get roster without permission")
        session.send(st.error_reply(stanza, 'auth', 'forbidden'))
    end

    return true
end)

-- set
module:hook("iq-set/bare/jabber:iq:roster:query", function(event)
    local session, stanza = event.origin, event.stanza
    if not stanza.attr.to then
        -- we don't want stanzas addressed to /self
        return
    end
    local from_node, from_host = jid.split(stanza.attr.to)
    local session_privileges = get_session_privileges(session, from_host)

    if session_privileges and _ROSTER_SET_PERM:contains(session_privileges.roster) then
        module:log("debug", "Roster set from allowed privileged entity received")
        -- following code is adapted from mod_remote_roster
        if not(usermanager_user_exists(from_node, from_host)) then return; end
        local roster = roster_manager.load_roster(from_node, from_host)
        if not(roster) then return; end

        local query = stanza.tags[1]
        for _, item in ipairs(query.tags) do
            if item.name == "item"
                and item.attr.xmlns == "jabber:iq:roster" and item.attr.jid
                    -- Protection against overwriting roster.pending, until we move it
                and item.attr.jid ~= "pending" then

                local item_jid = jid.prep(item.attr.jid)
                local _, host, resource = jid.split(item_jid)
                if not resource then
                    if item_jid ~= stanza.attr.to then -- not self-item_jid
                        if item.attr.subscription == "remove" then
                            local r_item = roster[item_jid]
                            if r_item then
                                roster[item_jid] = nil
                                if roster_manager.save_roster(from_node, from_host, roster) then
                                    session.send(st.reply(stanza))
                                    roster_manager.roster_push(from_node, from_host, item_jid)
                                else
                                    roster[item_jid] = item
                                    session.send(st.error_reply(stanza, "wait", "internal-server-error", "Unable to save roster"))
                                end
                            else
                                session.send(st.error_reply(stanza, "modify", "item-not-found"))
                            end
                        else
                            local subscription = item.attr.subscription
                            if subscription ~= "both" and subscription ~= "to" and subscription ~= "from" and subscription ~= "none" then -- TODO error on invalid
                                subscription = roster[item_jid] and roster[item_jid].subscription or "none"
                            end
                            local r_item = {name = item.attr.name, groups = {}}
                            if r_item.name == "" then r_item.name = nil; end
                            r_item.subscription = subscription
                            if subscription ~= "both" and subscription ~= "to" then
                                r_item.ask = roster[item_jid] and roster[item_jid].ask
                            end
                            for _, child in ipairs(item) do
                                if child.name == "group" then
                                    local text = table.concat(child)
                                    if text and text ~= "" then
                                        r_item.groups[text] = true
                                    end
                                end
                            end
                            local olditem = roster[item_jid]
                            roster[item_jid] = r_item
                            if roster_manager.save_roster(from_node, from_host, roster) then -- Ok, send success
                                session.send(st.reply(stanza))
                                -- and push change to all resources
                                roster_manager.roster_push(from_node, from_host, item_jid)
                            else -- Adding to roster failed
                                roster[item_jid] = olditem
                                session.send(st.error_reply(stanza, "wait", "internal-server-error", "Unable to save roster"))
                            end
                        end
                    else -- Trying to add self to roster
                        session.send(st.error_reply(stanza, "cancel", "not-allowed"))
                    end
                else -- Invalid JID added to roster
                    module:log("warn", "resource: %s , host: %s", tostring(resource), tostring(host))
                    session.send(st.error_reply(stanza, "modify", "bad-request")); -- FIXME what's the correct error?
                end
            else -- Roster set didn't include a single item, or its name wasn't  'item'
                session.send(st.error_reply(stanza, "modify", "bad-request"))
            end
        end -- for loop end
        -- end of code adapted from mod_remote_roster
    else -- The permission is not granted
        module:log("warn", "Entity "..tostring(session.full_jid).." try to set roster without permission")
        session.send(st.error_reply(stanza, 'auth', 'forbidden'))
    end

    return true
end)


--> message permission <--

local function clean_xmlns(node)
    -- Recursively remove "jabber:client" attribute from node.
    -- In Prosody internal routing, xmlns should not be set.
    -- Keeping xmlns would lead to issues like mod_smacks ignoring the outgoing stanza,
    -- so we remove all xmlns attributes with a value of "jabber:client"
    if node.attr.xmlns == 'jabber:client' then
        for childnode in node:childtags() do
            clean_xmlns(childnode)
        end
        node.attr.xmlns = nil
    end
end

module:hook("message/host", function(event)
    local session, stanza = event.origin, event.stanza
    local privilege_elt = stanza:get_child('privilege', _PRIV_ENT_NS)
    if privilege_elt==nil then return; end
    local _, to_host = jid.split(stanza.attr.to)
    local session_privileges = get_session_privileges(session, to_host)

    if session_privileges and session_privileges.message=="outgoing" then
        if #privilege_elt.tags==1 and privilege_elt.tags[1].name == "forwarded"
            and privilege_elt.tags[1].attr.xmlns==_FORWARDED_NS then
            local message_elt = privilege_elt.tags[1]:get_child('message', 'jabber:client')
            if message_elt ~= nil then
                local username, from_host, from_resource = jid.split(message_elt.attr.from)
                if from_resource == nil and hosts[from_host] then -- we only accept bare jids from one of the server hosts
                    clean_xmlns(message_elt);  -- needed do to proper routing
                    local session = {
                        username = username;
                        host = from_host;
                        type = "c2s";
                        log = module._log;
                    }
                    -- at this point everything should be alright, we can send the message
                    prosody.core_post_stanza(session, message_elt, true)
                else -- trying to send a message from a forbidden entity
                    module:log("warn", "Entity "..tostring(session.full_jid).." try to send a message from "..tostring(message_elt.attr.from))
                    session.send(st.error_reply(stanza, 'auth', 'forbidden'))
                end
            else -- incorrect message child
                session.send(st.error_reply(stanza, "modify", "bad-request", "invalid forwarded <message/> element"))
            end
        else -- incorrect forwarded child
            session.send(st.error_reply(stanza, "modify", "bad-request", "invalid <forwarded/> element"))
        end
    else -- The permission is not granted
        module:log("warn", "Entity "..tostring(session.full_jid).." try to send message without permission")
        session.send(st.error_reply(stanza, 'auth', 'forbidden'))
    end

    return true
end)


--> presence permission <--

local function same_tags(tag1, tag2)
    -- check if two tags are equivalent

    if tag1.name ~= tag2.name then return false; end

    if #tag1 ~= #tag2 then return false; end

    for name, value in pairs(tag1.attr) do
        if tag2.attr[name] ~= value then return false; end
    end

    for i=1,#tag1 do
        if type(tag1[i]) == "string" then
            if tag1[i] ~= tag2[i] then return false; end
        else
            if not same_tags(tag1[i], tag2[i]) then return false; end
        end
    end

    return true
end

local function same_presences(presence1, presence2)
    -- check that 2 <presence/> stanzas are equivalent (except for "to" attribute)
    -- /!\ if the id change but everything else is equivalent, this method return false
    -- this behaviour may change in the future
    if presence1.attr.from ~= presence2.attr.from or presence1.attr.id ~= presence2.attr.id
        or presence1.attr.type ~= presence2.attr.type then
        return false
    end

    if presence1.attr.id and presence1.attr.id == presence2.attr.id then return true; end

    if #presence1 ~= #presence2 then return false; end

    for i=1,#presence1 do
        if type(presence1[i]) == "string" then
            if presence1[i] ~= presence2[i] then return false; end
        else
            if not same_tags(presence1[i], presence2[i]) then return false; end
        end
    end

    return true
end

local function forward_presence(presence, to_jid)
    local presence_fwd = st.clone(presence)
    presence_fwd.attr.to = to_jid
    module:log("debug", "presence forwarded to "..to_jid..": "..tostring(presence_fwd))
    module:send(presence_fwd)
    -- cache used to avoid to send several times the same stanza
    priv_session.last_presence = presence
end

module:hook("presence/bare", function(event)
    if presence_man_ent:empty() and presence_roster:empty() then return; end

    local stanza = event.stanza
    if stanza.attr.type == nil or stanza.attr.type == "unavailable" then
        if not stanza.attr.to then
            for entity in presence_man_ent:items() do
                if stanza.attr.from ~= entity then forward_presence(stanza, entity); end
            end
        else -- directed presence
            -- we ignore directed presences from our own host, as we already have them
            local _, from_host = jid.split(stanza.attr.from)
            if hosts[from_host] then return; end

            -- we don't send several time the same presence, as recommended in §7 #2
            if priv_session.last_presence and same_presences(priv_session.last_presence, stanza) then
               return
            end

            for entity in presence_roster:items() do
                if stanza.attr.from ~= entity then forward_presence(stanza, entity); end
            end
        end
    end
end, 150)

--> IQ permission <--

module:hook("iq/bare/".._PRIV_ENT_NS..":privileged_iq", function(event)
    local session, stanza = event.origin, event.stanza
    if not stanza.attr.to then
        -- we don't want stanzas addressed to /self
        return
    end
    local from_node, from_host, from_resource = jid.split(stanza.attr.to)

    if from_resource ~= nil or not usermanager_user_exists(from_node, from_host) then
        session.send(
            st.error_reply(
                stanza,
                "auth",
                "forbidden",
                "wrapping <IQ> stanza recipient must be a bare JID of a local user"
            )
        )
        return true
    end

    local session_privileges = get_session_privileges(session, from_host)

    if session_privileges == nil then
        session.send(
            st.error_reply(
                stanza,
                "auth",
                "forbidden",
                "no privilege granted"
            )
        )
        return true
    end

    local iq_privileges = session_privileges["iq"]
    if iq_privileges == nil then
        session.send(
            session.send(st.error_reply(stanza, "auth", "forbidden", "you are not allowed to send privileged <IQ> stanzas"))
        )
        return true
    end

    local privileged_iq = stanza:get_child("privileged_iq", _PRIV_ENT_NS)

    local wrapped_iq = privileged_iq.tags[1]
    if wrapped_iq == nil then
        session.send(
            st.error_reply(stanza, "auth", "forbidden", "missing <IQ> stanza to send")
        )
        return true
    end

    if wrapped_iq.attr.xmlns ~= "jabber:client" then
        session.send(
            st.error_reply(
                stanza,
                "auth",
                "forbidden",
                'wrapped <IQ> must have a xmlns of "jabber:client"'
                )
        )
        return true
    end

    clean_xmlns(wrapped_iq)

    if #wrapped_iq.tags ~= 1 then
        session.send(
            st.error_reply(
                stanza,
                "auth",
                "forbidden",
                'invalid payload in wrapped <IQ>'
                )
        )
        return true
    end

    local payload = wrapped_iq.tags[1]

    local priv_ns = payload.attr.xmlns
    if priv_ns == nil then
        session.send(
            st.error_reply(stanza, "auth", "forbidden", "xmlns not set in privileged <IQ>")
        )
        return true
    end

    local ns_perms = iq_privileges[priv_ns]
    local iq_type = stanza.attr.type
    if ns_perms == nil or iq_type == nil or not ns_perms[iq_type] then
        session.send(
            session.send(st.error_reply(
                stanza,
                "auth",
                "forbidden",
                "you are not allowed to send privileged <IQ> stanzas of this type and namespace")
            )
        )
        return true
    end

    if wrapped_iq.attr.from ~= nil and wrapped_iq.attr.from ~= stanza.attr.to then
        session.send(
            st.error_reply(
                stanza,
                "auth",
                "forbidden",
                'wrapped <IQ> "from" attribute is inconsistent with main <IQ> "to" attribute'
            )
        )
        return true
    end

    wrapped_iq.attr.from = stanza.attr.to


    if wrapped_iq.attr.type ~= iq_type then
        session.send(
            st.error_reply(
                stanza,
                "auth",
                "forbidden",
                'invalid wrapped <IQ>: type mismatch'
            )
        )
        return true
    end

    if wrapped_iq.attr.id == nil then
        session.send(
            st.error_reply(
                stanza,
                "auth",
                "forbidden",
                'invalid wrapped <IQ>: missing "id" attribute'
            )
        )
        return true
    end

    -- at this point, wrapped_iq is considered valid, and privileged entity is allowed to send it
    local username, from_host, _ = jid.split(wrapped_iq.attr.from)
    local newsession = {
        username = username;
        host = from_host;
	    full_jid = stanza.attr.to;
        type = "c2s";
        log = module._log;
    }

    module:send_iq(wrapped_iq,newsession)
        :next(function (response)
            local reply = st.reply(stanza);
            response.stanza.attr.xmlns = 'jabber:client'
            reply:tag("privilege", {xmlns = _PRIV_ENT_NS})
            :tag("forwarded", {xmlns = _FORWARDED_NS})
            :add_child(response.stanza)
            session.send(reply)
        end,
        function(response)
            module:log("error", "Error while sending privileged <IQ>: %s", response);
            session.send(
                st.error_reply(
                    stanza,
                    "cancel",
                    "internal-server-error"
                )
            )
        end)

    return true
end)