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Lua Sandbox Library {#mainpage}

Overview

Sandboxes provide a dynamic and isolated execution environment for data parsing, transformation, and analysis. They allow access to data without jeopardizing the integrity or performance of the processing infrastructure. This broadens the audience that the data can be exposed to and facilitates new uses of the data (i.e. debugging, monitoring, dynamic provisioning, SLA analysis, intrusion detection, ad-hoc reporting, etc.)

The Lua sandbox is library allowing customized control over the Lua execution environment including functionality like global data preservation/restoration on shutdown/startup, output collection in textual, binary or [Heka protobuf format] (https://hekad.readthedocs.org/en/latest/sandbox/index.html#sample-lua-message-structure) and an array of parsers for various data types (Nginx, Apache, Syslog, MySQL and many RFC grammars)

Features

  • small - memory requirements are as little as 6 KiB for a basic sandbox
  • fast - microsecond execution times
  • stateful - ability to resume where it left off after a restart/reboot
  • isolated - failures are contained and malfunctioning sandboxes are terminated. Containment is defined in terms of restriction to the operating system, file system, libraries, memory use, Lua instruction use, and output size.

Installation

Prerequisites

Optional (used for documentation)

CMake Build Instructions

git clone https://github.com/mozilla-services/lua_sandbox.git
cd lua_sandbox
mkdir release
cd release

# UNIX
cmake -DCMAKE_BUILD_TYPE=release ..
make

# Windows Visual Studio 2013
cmake -DCMAKE_BUILD_TYPE=release -G "NMake Makefiles" ..
nmake

# Windows MinGW
cmake -DCMAKE_BUILD_TYPE=release -G "MinGW Makefiles" ..
mingw32-make

ctest

Sandbox API

Lua functions exposed to C by the core sandbox

There are no functions exposed by default, see lsb_pcall_setup() and lsb_pcall_teardown() when defining an API.

Functions exposed to Lua by the core sandbox

require(libraryName)

By default only the base library is loaded additional libraries must be loaded with require().

Arguments

  • libraryName (string)
    • base library
      • The require() function has been modified to not expose any of the package table to the sandbox.
      • Disabled functions (default): collectgarbage, coroutine, dofile, load, loadfile, loadstring, newproxy, print.
    • bloom_filter Test whether an element is a member of a set
    • circular_buffer In memory time series data base and analysis
    • cjson JSON parser with the following modifications:
      • Loads the cjson module in a global cjson table
      • The encode buffer is limited to the sandbox output_limit.
      • The decode buffer will be roughly limited to one half of the sandbox memory_limit.
      • The NULL value is not decoded to cjson.null it is simply discarded. If the original behavior is desired use cjson.decode_null(true) to enable NULL decoding.
      • The new() function has been disabled so only a single cjson parser can be created.
      • The encode_keep_buffer() function has been disabled (the buffer is always reused).
    • cuckoo_filter Bloom filter alternative supporting deletions
    • hyperloglog Efficiently count the number of elements in a set
    • lpeg Lua Parsing Expression Grammar Library
    • re Regex syntax for LPEG
    • math
    • os
      • The local timezone is set to UTC in all sandboxes.
      • Disabled functions (default): getenv, execute, exit, remove, rename, setlocale, tmpname.
    • sax Symbolic time series data analysis based on Symbolic Aggregate approXimation.
    • string
    • struct Converts data to/from C structs
    • table
    • Grammar Libraries
      • cbufd - Parses the circular buffer library delta output (use for data aggregation)
      • common_log_format - Nginx and Apache meta grammar generators (creates a grammar based on the log_format configuration)
      • data_time - RFC3339, RFC3164, strftime, common log format, MySQL and Postgres timestamps
      • ip_address - IPv4 and IPv6 address
      • mysql - MySQL and MariaDB slow query and short slow query parsers
      • postfix - Postfix messages
      • syslog - Rsyslog meta grammar generator (creates a grammar based on the template configuration)
      • syslog_message - Syslog messages
    • user provided (lua, so/dll)

Return

  • a table - For non user provided libraries the table is also globally registered with the library name. User provided libraries may implement there own semantics i.e. the grammar libraries return a table but do not globally register the table name (see the individual module documentation for the correct usage).

output(arg0, arg1, ...argN) lsb_appends data to the output buffer, which cannot exceed the output_limit configuration parameter. See lsb_get_output() to connect the output to the host application.

Arguments

  • arg (number, string, bool, nil, circular_buffer) Lua variable or literal to be appended the output buffer

Return

  • none

Note: To extend the function set exposed to Lua see lsb_add_function()

How to interact with the sandbox (creating an API)

The best place to start is with some examples:

Unit Test API

Unit Test Source Code

Lua Functions Exposed to C

  • int process (double)
    • exposes a process function that takes a test case number as its argument and returns and integer result code.
  • void report (double)
    • exposes a report function that takes a test case number as its argument and returns nothing.

C Functions Exposed to Lua

  • void write_output (optionalArg1, optionalArg2, optionalArgN)
    • captures whatever is in the output buffer for use by the host application, appending any optional arguments (optional arguments have the same restriction as output).
  • void write_message (table)
    • serializes the Lua table into a Heka protobuf message and captures the output.
    • the table must use the following schema.

Heka Sandbox API

Heka Sandbox