osquery supports proprietary tables, config plugins, and logger plugins built in C++ (or languages other than C++) through a Thrift-based extensions API. This is helpful if your enterprise or integration uses an internal method for configuration or log collection. You can write your "extension" internally, and ask osquery to depend on the plugins it exposes. To make deployment and management of extensions simple, osqueryd may "autoload", or subprocess, these extension binaries and monitor their performance.
If you are interested in writing extensions please read the SDK and Extensions development article. That wiki article describes the Thrift API and provides example C++ code for an extension. Every extension runs as a separate process and communicates to an osquery process using Thrift and a UNIX domain socket. A single extension may contain arbitrary plugins, each are registered using a setUp API call. At Facebook we deploy an
fb-osquery package and single binary that contains our Facebook-specific tables and internal configuration/logging APIs.
The following CLI flags control extension auto-loading:
--extensions_autoload=/etc/osquery/extensions.load --extensions_timeout=3 --extensions_interval=3
extensions_autoload points to a line-delimited set of paths to executables. When osquery launches, each path is evaluated for "safe permissions" and executed as a monitored child process. Each executable receives 3 argument switches:
interval. An extension process may use these to find the osquery process's Thrift socket, as well as hints on retry/backoff configuration if any latency or errors occur. If the
--verbose flag is passed to osqueryd, the flag will also be received by the executable.
extensions.load file contains a single extension path:
$ cat /etc/osquery/extensions.load /usr/lib/osquery/extensions/fb_osquery.ext $ file /usr/lib/osquery/extensions/fb_osquery.ext /usr/lib/osquery/extensions/fb_osquery.ext: ELF 64-bit LSB executable
The autoload workflow is similar to:
- Check if extensions are enabled.
--extensions_autoloadand check permissions/ownership of each path.
- Checks if the file name extension of the path is .ext. Filename extension must be .ext.
- Fork and execute each path with the switches described above.
- Treat each child process as a "worker" and enforce sane memory/cycle usage.
- Read set config plugin from
- If the config plugin does not exist and at least 1 extension was autoload:
--extensions_timeout * --extensions_intervalfor the extension to register the config plugin.
- Fail if the plugin is not registered or the plugin returns a failed status.
The same dependency check is applied to the logger plugin setting after a valid config is read. Every registered plugin is available throughout the run of the shell or daemon.
Extensions are most useful when used to expose config or logger plugins. Along with auto-loading extensions, you can start daemon services with non-default plugins using
osqueryd initscript or SystemV service on Linux searches for a
/etc/osquery/osquery.flags path containing flags. This is a great place to add non-default extensions options or for replacing plugins:
$ cat /etc/osquery/osquery.flags --config_plugin=custom_plugin --logger_plugin=scribe