-- XEP-0071: XHTML-IM sanitizing local assert = assert; local st = require "util.stanza"; local url = require "socket.url"; local no_styles = module:get_option_boolean("strip_xhtml_style", true); -- Tables from XEP-0071 local xeptables = [[
class, id, title; style
profile
version
class, id, title; style class, id, title; style
class, id, title; style
class, id, title; style; cite
class, id, title; style
class, id, title; style
class, id, title; style
class, id, title; style
class, id, title; style class, id, title; style
class, id, title; style
class, id, title; style
class, id, title; style
class, id, title; style
class, id, title; style
class, id, title; style class, id, title; style
class, id, title; style
class, id, title; style class, id, title; style; cite class, id, title; style class, id, title; style class, id, title; style class, id, title; style class, id, title; style; accesskey, charset, href, hreflang, rel, rev, tabindex, type
class, id, title; style
class, id, title; style
class, id, title; style
class, id, title; style
class, id, title; style
class, id, title; style class, id, title; style; alt, height, longdesc, src, width ]]; -- map of whitelisted tag names to set of allowed attributes local tags = {}; -- { string : { string : boolean } } for tag, attrs in xeptables:gmatch("<(%w+)/>([^\n]*)") do tags[tag] = { xmlns = true, ["xml:lang"] = true }; for attr in attrs:gmatch("%w+") do tags[tag][attr] = true; end if no_styles then tags[tag]["style"] = nil; end end -- module:log("debug", "tags = %s;", require "util.serialization".serialize(tags)); -- TODO Decide if disallowed tags should be bounced or silently discarded. -- XEP says "ignore" and replace tag with text content, but that would -- need a different transform which can't use `maptags`. if not module:get_option_boolean("bounce_invalid_xhtml", false) then assert = function (x) return x end end local function sanitize_xhtml(tag) -- module:log("debug", "sanitize_xhtml(<{%s}%s>)", tag.attr.xmlns, tag.name); if tag.attr.xmlns == "http://www.w3.org/1999/xhtml" then local allowed = assert(tags[tag.name], tag.name); if allowed then for attr, value in pairs(tag.attr) do if not allowed[attr] then -- module:log("debug", "Removing disallowed attribute %q from <%s>", attr, tag.name); tag.attr[attr] = nil; elseif attr == "src" or attr == "href" then local urlattr = url.parse(value); local scheme = urlattr and urlattr.scheme; if scheme ~= "http" and scheme ~= "https" and scheme ~= "mailto" and scheme ~= "xmpp" and scheme ~= "cid" then tag.attr[attr] = "https://url.was.invalid/"; end end end else tag.name = "span" tag.attr = { xmlns = "http://www.w3.org/1999/xhtml" } end -- Check child tags tag:maptags(sanitize_xhtml); -- This tag is clean! return tag; end -- Not xhtml, probably best to discard it return nil; end -- Check for xhtml-im, sanitize if exists local function message_handler(event) local stanza = event.stanza; if stanza:get_child("html", "http://jabber.org/protocol/xhtml-im") then stanza = st.clone(stanza); if pcall(function() -- try stanza:get_child("html", "http://jabber.org/protocol/xhtml-im"):maptags(sanitize_xhtml); end) then event.stanza = stanza; else -- catch if stanza.attr.type ~= "error" then event.origin.send(st.error_reply(stanza, "modify", "not-acceptable", "Stanza contained illegal XHTML-IM tag")); end return true; end end end -- Stanzas received from clients module:hook("pre-message/bare", message_handler, 71); module:hook("pre-message/full", message_handler, 71); module:hook("pre-message/host", message_handler, 71); -- Stanzas about to be delivered to clients module:hook("message/bare", message_handler, 71); module:hook("message/full", message_handler, 71);