Software /
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prosody
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util/format.lua @ 12518:73ee3855f970
mod_smacks: Factor out some convenience functions
Those lines are long and the risk of mistakes if another one needs to be
added seems high, but lower when factored out like this.
author | Kim Alvefur <zash@zash.se> |
---|---|
date | Fri, 11 Feb 2022 16:09:42 +0100 |
parent | 12261:f7946c8e502f |
child | 12573:0f4feaf9ca64 |
line wrap: on
line source
-- -- A string.format wrapper that gracefully handles invalid arguments since -- certain format string and argument combinations may cause errors or other -- issues like log spoofing -- -- Provides some protection from e.g. CAPEC-135, CWE-117, CWE-134, CWE-93 local tostring = tostring; local unpack = table.unpack or unpack; -- luacheck: ignore 113/unpack local pack = require "util.table".pack; -- TODO table.pack in 5.2+ local valid_utf8 = require "util.encodings".utf8.valid; local type = type; local dump = require "util.serialization".new("debug"); local num_type = math.type or function (n) return n % 1 == 0 and n <= 9007199254740992 and n >= -9007199254740992 and "integer" or "float"; end -- In Lua 5.3+ these formats throw an error if given a float local expects_integer = { c = true, d = true, i = true, o = true, u = true, X = true, x = true, }; -- In Lua 5.2 these throw an error given a negative number local expects_positive = { o = true; u = true; x = true; X = true }; -- Printable Unicode replacements for control characters local control_symbols = { -- 0x00 .. 0x1F --> U+2400 .. U+241F, 0x7F --> U+2421 ["\000"] = "\226\144\128", ["\001"] = "\226\144\129", ["\002"] = "\226\144\130", ["\003"] = "\226\144\131", ["\004"] = "\226\144\132", ["\005"] = "\226\144\133", ["\006"] = "\226\144\134", ["\007"] = "\226\144\135", ["\008"] = "\226\144\136", ["\009"] = "\226\144\137", ["\010"] = "\226\144\138", ["\011"] = "\226\144\139", ["\012"] = "\226\144\140", ["\013"] = "\226\144\141", ["\014"] = "\226\144\142", ["\015"] = "\226\144\143", ["\016"] = "\226\144\144", ["\017"] = "\226\144\145", ["\018"] = "\226\144\146", ["\019"] = "\226\144\147", ["\020"] = "\226\144\148", ["\021"] = "\226\144\149", ["\022"] = "\226\144\150", ["\023"] = "\226\144\151", ["\024"] = "\226\144\152", ["\025"] = "\226\144\153", ["\026"] = "\226\144\154", ["\027"] = "\226\144\155", ["\028"] = "\226\144\156", ["\029"] = "\226\144\157", ["\030"] = "\226\144\158", ["\031"] = "\226\144\159", ["\127"] = "\226\144\161", }; local supports_p = pcall(string.format, "%p", ""); -- >= Lua 5.4 local supports_a = pcall(string.format, "%a", 0.0); -- > Lua 5.1 local function format(formatstring, ...) local args = pack(...); local args_length = args.n; -- format specifier spec: -- 1. Start: '%%' -- 2. Flags: '[%-%+ #0]' -- 3. Width: '%d?%d?' -- 4. Precision: '%.?%d?%d?' -- 5. Option: '[cdiouxXaAeEfgGqs%%]' -- -- The options c, d, E, e, f, g, G, i, o, u, X, and x all expect a number as argument, whereas q and s expect a string. -- This function does not accept string values containing embedded zeros, except as arguments to the q option. -- a and A are only in Lua 5.2+ -- Lua 5.4 adds a p format that produces a pointer -- process each format specifier local i = 0; formatstring = formatstring:gsub("%%[^cdiouxXaAeEfgGpqs%%]*[cdiouxXaAeEfgGpqs%%]", function(spec) if spec == "%%" then return end i = i + 1; local arg = args[i]; if arg == nil then args[i] = "nil"; return "(%s)"; end local option = spec:sub(-1); local t = type(arg); if option == "s" and t == "string" and not arg:find("[%z\1-\31\128-\255]") then -- No UTF-8 or control characters, assumed to be the common case. return elseif t == "number" then if option == "g" or (option == "d" and num_type(arg) == "integer") then return end elseif option == "s" and t ~= "string" then arg = tostring(arg); t = "string"; end if option ~= "s" and option ~= "q" and option ~= "p" then -- all other options expect numbers if t ~= "number" then -- arg isn't number as expected? arg = tostring(arg); option = "s"; spec = "[%s]"; t = "string"; elseif expects_integer[option] and num_type(arg) ~= "integer" then args[i] = tostring(arg); return "[%s]"; elseif expects_positive[option] and arg < 0 then args[i] = tostring(arg); return "[%s]"; elseif (option == "a" or option == "A") and not supports_a then return "%x"; else return -- acceptable number end end if option == "p" and not supports_p then arg = tostring(arg); option = "s"; spec = "[%s]"; t = "string"; end if t == "string" and option ~= "p" then if not valid_utf8(arg) then option = "q"; elseif option ~= "q" then -- gets fully escaped in the next block -- Prevent funny things with ASCII control characters and ANSI escape codes (CWE-117) -- Also ensure embedded newlines can't look like another log line (CWE-93) args[i] = arg:gsub("[%z\1-\8\11-\31\127]", control_symbols):gsub("\n\t?", "\n\t"); return spec; end end if option == "q" then args[i] = dump(arg); return "%s"; end if option == "p" and (t == "boolean" or t == "number") then args[i] = tostring(arg); return "[%s]"; end end); -- process extra args while i < args_length do i = i + 1; local arg = args[i]; if arg == nil then args[i] = "(nil)"; else args[i] = tostring(arg):gsub("[%z\1-\8\11-\31\127]", control_symbols):gsub("\n\t?", "\n\t"); end formatstring = formatstring .. " [%s]" end return formatstring:format(unpack(args)); end return { format = format; };