Another attempt to inflate a gzip file in Lua with output size restrictions

gistfile1.lua

-- Debian package nginx-extras and lzlib (https://github.com/LuaDist/lzlib) required

MAX_BUFFER_SIZE = 1048576

function inflate_body (data)
	local inflate = require("zlib").inflate(data)

	local buffer = ""

	repeat
		chunk = inflate:read(10240)
		if chunk ~= nil then
			buffer = buffer .. chunk
		end

		if buffer:len() > MAX_BUFFER_SIZE then
			inflate:close()
			create_error_response(4005, "Inflated body exceeded limits")
		end
	until chunk == nil

	inflate:close()

	return buffer
end

function create_error_response (code, description)
	local message = string.format('{"status":400,"statusReason":"Bad Request","code":%d,"exception":"","description":"%s","message":"HTTP 400 Bad Request"}', code, description)
	ngx.status = ngx.HTTP_BAD_REQUEST
	ngx.header.content_type = "application/json"
	ngx.say(message)
	ngx.exit(ngx.HTTP_OK)
end

local content_encoding = ngx.req.get_headers()["Content-Encoding"]

if content_encoding == "gzip" then
	ngx.req.read_body()
	local data = ngx.req.get_body_data()

	local status, buffer = pcall(inflate_body, data)

	if not status then
		-- Corrupted GZIP body
		create_error_response(4001, "Corrupted GZIP body")
	end

	ngx.log(ngx.ERR, buffer:len())

	ngx.req.clear_header("Content-Encoding")
	ngx.req.clear_header("Content-Length")
	ngx.req.set_body_data(buffer)
end