Lazy load safety.lua and fix some issues

README.md

@@ -22,14 +22,17 @@ A Minetest mod library to make modifying formspecs easier.
  - `formspec_ast.apply_offset(tree, x, y)`: Shifts all elements in `tree`.
     Similar to `container`.
  - `formspec_ast.flatten(tree)`: Removes all containers and offsets elements
-    that were in containers accordingly. **The use of this function is
+    that were in containers accordingly. Note that `scroll_container[]`
-    discouraged as `scroll_container[]` elements are not flattened.**
+    elements are not flattened.
  - `formspec_ast.show_formspec(player_or_name, formname, formspec)`: Similar
     to `minetest.show_formspec`, however also accepts player objects and will
     pass `formspec` through `formspec_ast.interpret` first.
  - `formspec_ast.safe_parse(string_or_tree)`: Similar to `formspec_ast.parse`,
     however will delete any elements that may crash the client (or any I
-    haven't added to the safe element list).
+    haven't added to the safe element list). The safe element list that this
+    function uses is very limited, it may break complex formspecs.
+ - `formspec_ast.safe_interpret(string_or_tree)`: Equivalent to
+    `formspec_ast.unparse(formspec_ast.safe_parse(string_or_tree))`.
  - `formspec_ast.formspec_escape(text)`: The same as `minetest.formspec_escape`,
     should only be used when formspec_ast is being embedded outside of Minetest.
 

core.lua

@@ -1,12 +1,12 @@
 --
--- formspec_ast: An abstract system tree for formspecs.
+-- formspec_ast: An abstract syntax tree for formspecs.
 --
 -- This does not actually depend on Minetest and could probably run in
 -- standalone Lua.
 --
 -- The MIT License (MIT)
 --
--- Copyright © 2019 by luk3yx.
+-- Copyright © 2019-2022 by luk3yx.
 --
 -- Permission is hereby granted, free of charge, to any person obtaining a copy
 -- of this software and associated documentation files (the "Software"), to
@@ -541,8 +541,8 @@ end
 
 -- Allow other mods to access raw_parse and raw_unparse. Note that these may
 -- change or be removed at any time.
-formspec_ast._raw_parse = raw_parse
+-- formspec_ast._raw_parse = raw_parse
-formspec_ast._raw_unparse = raw_unparse
+-- formspec_ast._raw_unparse = raw_unparse
 
 -- Register custom elements
 parse_mt = {}

helpers.lua

@@ -1,12 +1,12 @@
 --
--- formspec_ast: An abstract system tree for formspecs.
+-- formspec_ast: An abstract syntax tree for formspecs.
 --
 -- This does not actually depend on Minetest and could probably run in
 -- standalone Lua.
 --
 -- The MIT License (MIT)
 --
--- Copyright © 2019 by luk3yx.
+-- Copyright © 2019-2022 by luk3yx.
 --
 -- Permission is hereby granted, free of charge, to any person obtaining a copy
 -- of this software and associated documentation files (the "Software"), to
@@ -29,6 +29,9 @@
 
 local formspec_ast, minetest = formspec_ast, formspec_ast.minetest
 
+-- Expose minetest.formspec_escape for use outside of Minetest
+formspec_ast.formspec_escape = minetest.formspec_escape
+
 -- Parses and unparses plain formspecs and just unparses AST trees.
 function formspec_ast.interpret(spec, custom_handlers)
     local ast = spec

init.lua

@@ -1,12 +1,12 @@
 --
--- formspec_ast: An abstract system tree for formspecs.
+-- formspec_ast: An abstract syntax tree for formspecs.
 --
 -- This does not actually depend on Minetest and could probably run in
 -- standalone Lua.
 --
 -- The MIT License (MIT)
 --
--- Copyright © 2019 by luk3yx.
+-- Copyright © 2019-2022 by luk3yx.
 --
 -- Permission is hereby granted, free of charge, to any person obtaining a copy
 -- of this software and associated documentation files (the "Software"), to
@@ -37,7 +37,6 @@ if minetest then
     modpath = minetest.get_modpath('formspec_ast')
     assert(minetest.get_current_modname() == 'formspec_ast',
            'This mod must be called formspec_ast!')
-    formspec_ast.formspec_escape = minetest.formspec_escape
 else
     -- Probably running outside Minetest.
     modpath = rawget(_G, 'FORMSPEC_AST_PATH') or '.'
@@ -69,13 +68,21 @@ else
         return res
     end
     formspec_ast.minetest = minetest
-    formspec_ast.formspec_escape = minetest.formspec_escape
 end
 
 formspec_ast.modpath = modpath
 
 dofile(modpath .. '/core.lua')
 dofile(modpath .. '/helpers.lua')
-dofile(modpath .. '/safety.lua')
+
+-- Lazy load safety.lua because I don't think anything actually uses it
+function formspec_ast.safe_parse(...)
+    dofile(modpath .. '/safety.lua')
+    return formspec_ast.safe_parse(...)
+end
+
+function formspec_ast.safe_interpret(tree)
+    return formspec_ast.unparse(formspec_ast.safe_parse(tree))
+end
 
 formspec_ast.modpath, formspec_ast.minetest = nil, nil

safety.lua

@@ -1,12 +1,12 @@
 --
--- formspec_ast: An abstract system tree for formspecs.
+-- formspec_ast: An abstract syntax tree for formspecs.
 --
 -- This verifies that formspecs from untrusted sources are safe(-ish) to
 -- display, provided they are passed through formspec_ast.interpret.
 --
 -- The MIT License (MIT)
 --
--- Copyright © 2019 by luk3yx.
+-- Copyright © 2019-2022 by luk3yx.
 --
 -- Permission is hereby granted, free of charge, to any person obtaining a copy
 -- of this software and associated documentation files (the "Software"), to
@@ -27,8 +27,8 @@
 -- IN THE SOFTWARE.
 --
 
--- Similar to ast.walk(), however returns {} and then exits if walk() would
+-- Similar to ast.walk(), however returns nil if walk() would crash. Use this
--- crash. Use this for untrusted formspecs, otherwise use walk() for speed.
+-- for untrusted formspecs, otherwise use walk() for speed.
 local function safe_walk(tree)
     local walk = formspec_ast.walk(tree)
     local seen = {}
@@ -36,13 +36,9 @@ local function safe_walk(tree)
         if not walk or not seen then return end
 
         local good, msg = pcall(walk)
-        if good and (type(msg) == 'table' or msg == nil) and not seen[msg] then
+        if good and type(msg) == 'table' and not seen[msg] then
-            if msg then
+            seen[msg] = true
-                seen[msg] = true
-            end
             return msg
-        else
-            return {}
         end
     end
 end
@@ -52,7 +48,7 @@ local function safe_flatten(tree)
     local res = {formspec_version = 1}
     if type(tree.formspec_version) == 'number' and
             tree.formspec_version > 1 then
-        res.formspec_version = 2
+        res.formspec_version = math.min(math.floor(tree.formspec_version), 6)
     end
     for elem in safe_walk(table.copy(tree)) do
         if elem.type == 'container' then
@@ -76,16 +72,40 @@ function ensure.string(obj)
 end
 
 function ensure.number(obj, max, min)
+    if obj == nil then return end
+
     local res = tonumber(obj)
     assert(res ~= nil and res == res)
     assert(res <= (max or 100) and res >= (min or 0))
     return res
 end
 
+function ensure.boolean(bool)
+    assert(type(bool) == "boolean" or bool == nil)
+    return bool
+end
+
 function ensure.integer(obj)
     return math.floor(ensure.number(obj))
 end
 
+function ensure.texture(obj)
+    return ensure.string(obj):match("^[^%[]+")
+end
+
+function ensure.list(items)
+    assert(type(items) == 'table')
+    for k, v in pairs(items) do
+        assert(type(k) == 'number' and type(v) == 'string')
+    end
+    return items
+end
+
+function ensure.inventory_location(location)
+    assert(location == 'current_node' or location == 'current_player')
+    return location
+end
+
 local validate
 local function validate_elem(obj)
     local template = validate[obj.type]
@@ -95,15 +115,11 @@ local function validate_elem(obj)
         if k == 'type' then
             func = ensure.string
         else
-            local type_ = template[k]
+            local value_type = template[k]
-            if type(type_) == 'string' then
+            if value_type and value_type:sub(-1) == '?' then
-                if type_:sub(#type_) == '?' then
+                value_type = value_type:sub(1, -2)
-                    type_ = type_:sub(1, #type_ - 1)
-                end
-                func = ensure[type_]
-            elseif type(type_) == 'function' then
-                func = type_
             end
+            func = ensure[value_type]
         end
 
         if func then
@@ -114,7 +130,7 @@ local function validate_elem(obj)
     end
 
     for k, v in pairs(template) do
-        if type(v) ~= 'string' or v:sub(#v) ~= '?' then
+        if v:sub(-1) ~= '?' then
             assert(obj[k] ~= nil, k .. ' does not exist!')
         end
     end
@@ -124,16 +140,16 @@ validate = {
     size = {w = 'number', h = 'number'},
     label = {x = 'number', y = 'number', label = 'string'},
     image = {x = 'number', y = 'number', w = 'number', h = 'number',
-        texture_name = 'string'},
+        texture_name = 'texture'},
     button = {x = 'number', y = 'number', w = 'number', h = 'number',
         name = 'string', label = 'string'},
     image_button = {x = 'number', y = 'number', w = 'number', h = 'number',
-        name = 'string', label = 'string', texture_name = 'string',
+        name = 'string', label = 'string', texture_name = 'texture',
         noclip = 'string', drawborder = 'string',
-        pressed_texture_name = 'string'},
+        pressed_texture_name = 'texture'},
     item_image_button = {x = 'number', y = 'number', w = 'number',
         h = 'number', name = 'string', label = 'string',
-        texture_name = 'string'},
+        texture_name = 'texture'},
     field = {x = 'number', y = 'number', w = 'number', h = 'number',
         name = 'string', label = 'string', default = 'string'},
     pwdfield = {x = 'number', y = 'number', w = 'number', h = 'number',
@@ -142,14 +158,13 @@ validate = {
     textarea = {x = 'number', y = 'number', w = 'number', h = 'number',
         name = 'string', label = 'string', default = 'string'},
     dropdown = {
-        x = 'number', y = 'number', w = 'number', name = 'string',
+        x = 'number', y = 'number', w = 'number', h = 'number?',
-        items = function(items)
+        name = 'string', items = 'list', selected_idx = 'integer',
-            assert(type(items) == 'list')
+    },
-            for k, v in pairs(items) do
+    textlist = {
-                assert(type(k) == 'number' and type(v) == 'string')
+        x = 'number', y = 'number', w = 'number', h = 'number?',
-            end
+        name = 'string', listelems = 'list', selected_idx = 'integer?',
-        end,
+        transparent = 'boolean?',
-        selected_idx = 'integer',
     },
     checkbox = {x = 'number', y = 'number', name = 'string', label = 'string',
         selected = 'string'},
@@ -157,12 +172,9 @@ validate = {
         color = 'string'},
 
     list = {
-        inventory_location = function(location)
+        inventory_location = 'inventory_location', list_name = 'string',
-            assert(location == 'current_node' or location == 'current_player')
+        x = 'number', y = 'number', w = 'number', h = 'number',
-            return location
+        starting_item_index = 'number?',
-        end,
-        list_name = 'string', x = 'number', y = 'number', w = 'number',
-        h = 'number', starting_item_index = 'number?',
     },
     listring = {},
 }
@@ -196,7 +208,3 @@ function formspec_ast.safe_parse(tree, custom_handlers)
 
     return res
 end
-
-function formspec_ast.safe_interpret(tree)
-    return formspec_ast.unparse(formspec_ast.safe_parse(tree))
-end

tests.lua

@@ -562,4 +562,20 @@ assert_equal(assert(formspec_ast.interpret('label[1,2;abc\\')),
 assert_equal(assert(formspec_ast.interpret('label[1,2;abc\\\\')),
     'label[1,2;abc\\\\]')
 
+assert_equal(formspec_ast.formspec_escape('label[1,2;abc\\def]'),
+    'label\\[1\\,2\\;abc\\\\def\\]')
+
+assert_equal(
+    formspec_ast.safe_interpret([[
+        formspec_version[5.1]
+        size[3,3]
+        label[0,0;Hi]
+        image[1,2;3,4;a^b\[c]
+        formspec_ast:crash[]
+        textlist[1,2;3,4;test;a,b,c]
+    ]]),
+    'formspec_version[5]size[3,3]label[0,0;Hi]image[1,2;3,4;a^b]' ..
+    'textlist[1,2;3,4;test;a,b,c]'
+)
+
 print('Tests pass')