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util/xml.lua @ 12578:10bb58ad5583
executables: Reject Lua 5.1 early
Prevents attempting to load libraries that may no longer be found and
crashing with a traceback.
Platforms like Debian where multiple Lua versions can be installed at
the same time and 'lua' pointing to one of the installed interpreters
via symlinks, there's the possibility that prosody/prosodyctl may be
invoked with Lua 5.1, which will no longer have any of the rest of
Prosody libraries available to be require(), and thus would immediately
fail with an unfriendly traceback.
Checking and aborting early with a friendlier message and reference to
more information is better.
Part of #1600
author | Kim Alvefur <zash@zash.se> |
---|---|
date | Sat, 02 Jul 2022 17:27:39 +0200 (2022-07-02) |
parent | 12270:c78639ee6ccb |
child | 12975:d10957394a3c |
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local st = require "util.stanza"; local lxp = require "lxp"; local t_insert = table.insert; local t_remove = table.remove; local error = error; local _ENV = nil; -- luacheck: std none local parse_xml = (function() local ns_prefixes = { ["http://www.w3.org/XML/1998/namespace"] = "xml"; }; local ns_separator = "\1"; local ns_pattern = "^([^"..ns_separator.."]*)"..ns_separator.."?(.*)$"; return function(xml, options) --luacheck: ignore 212/self local handler = {}; local stanza = st.stanza("root"); local namespaces = {}; local prefixes = {}; function handler:StartNamespaceDecl(prefix, url) if prefix ~= nil then t_insert(namespaces, url); t_insert(prefixes, prefix); end end function handler:EndNamespaceDecl(prefix) if prefix ~= nil then -- we depend on each StartNamespaceDecl having a paired EndNamespaceDecl t_remove(namespaces); t_remove(prefixes); end end function handler:StartElement(tagname, attr) local curr_ns,name = tagname:match(ns_pattern); if name == "" then curr_ns, name = "", curr_ns; end if curr_ns ~= "" then attr.xmlns = curr_ns; end for i=1,#attr do local k = attr[i]; attr[i] = nil; local ns, nm = k:match(ns_pattern); if nm ~= "" then ns = ns_prefixes[ns]; if ns then attr[ns..":"..nm] = attr[k]; attr[k] = nil; end end end local n = {} for i=1,#namespaces do n[prefixes[i]] = namespaces[i]; end stanza:tag(name, attr, n); end function handler:CharacterData(data) stanza:text(data); end function handler:EndElement() stanza:up(); end -- SECURITY: These two handlers, especially the Doctype one, are required to prevent exploits such as Billion Laughs. local function restricted_handler(parser) if not parser.stop or not parser:stop() then error("Failed to abort parsing"); end end handler.StartDoctypeDecl = restricted_handler; if not options or not options.allow_comments then -- NOTE: comments are generally harmless and can be useful when parsing configuration files or other data, even user-provided data handler.Comment = restricted_handler; end if not options or not options.allow_processing_instructions then -- Processing instructions should generally be safe to just ignore handler.ProcessingInstruction = restricted_handler; end local parser = lxp.new(handler, ns_separator); local ok, err, line, col = parser:parse(xml); if ok then ok, err, line, col = parser:parse(); end --parser:close(); if ok then return stanza.tags[1]; else return ok, ("%s (line %d, col %d))"):format(err, line, col); end end; end)(); return { parse = parse_xml; };