osquery

traviscj

- 4 minutes read - 662 words

I’ve known about [osquery][] for a while, but recently spent some time digging around in it. [osquery]: https://osquery.io The basic idea is to provide a consistent SQL interface to a bunch of system data, instead of learning idiosyncrasies of individual commands (which themselves vary across operating systems). My hacker buddy Sharvil has worked on osquery a fair bit and explained to me a couple years ago that it actually uses [sqlite][]’s [virtual table functionality][vtab] to provide the interface – it’s a fascinating and brilliant project! [sqlite]: https://sqlite.org/ [vtab]: https://sqlite.org/vtab.html

Concretely, instead of running [uptime]uptime and getting either

osx ➜ uptime
 8:48  up 17:27, 10 users, load averages: 4.57 4.74 5.08
linux ➜ uptime
 16:52:12 up 192 days,  9:59,  1 user,  load average: 0.00, 0.00, 0.00

you can run: [uptime]: https://linux.die.net/man/1/uptime

osquery> SELECT * FROM uptime;
+------+-------+---------+---------+---------------+
| days | hours | minutes | seconds | total_seconds |
+------+-------+---------+---------+---------------+
| 2    | 1     | 18      | 38      | 177518        |
+------+-------+---------+---------+---------------+

We can also query for system information (shown here in line mode)

osquery> .mode line
osquery> SELECT * FROM system_info;
          hostname = traviscj.local
              uuid = [redacted]
          cpu_type = x86_64h
       cpu_subtype = Intel x86-64h Haswell
         cpu_brand = Intel(R) Core(TM) i7-4850HQ CPU @ 2.30GHz
cpu_physical_cores = 4
 cpu_logical_cores = 8
   physical_memory = 17179869184
   hardware_vendor = Apple Inc.
    hardware_model = MacBookPro11,2
  hardware_version = 1.0
   hardware_serial = [redacted]
     computer_name = traviscj
    local_hostname = traviscj

and even perform HTTP requests with the curl table:

osquery> SELECT url, response_code FROM curl WHERE url IN ('https://traviscj.com/_status.json', 'https://pauljoos.com/_status.json');
+-----------------------------------+---------------+
| url                               | response_code |
+-----------------------------------+---------------+
| https://pauljoos.com/_status.json | 200           |
| https://traviscj.com/_status.json | 200           |
+-----------------------------------+---------------+

I tried to reproduce a simple ps wrapper I have:

#!/bin/sh
# a simple script to show java processes without extremely long classpaths

ps aux | grep '[b]in/java' | grep -v $0 | awk '{ print $2" "$11" "$NF }'

and ended up with

SELECT pid
     , SUBSTR(cmdline, 
         (WITH char_index(i, ch) AS (values(1, '') UNION ALL SELECT i+1, substr(cmdline, i, 1) AS r FROM char_index WHERE r != '')
         SELECT MAX(i) FROM char_index WHERE char_index.ch = ' ')
       ) as java_main_class
FROM processes WHERE name = 'java';

which produces

osquery> SELECT pid, SUBSTR(cmdline, (WITH char_index(i, ch) AS (
    ...>     values(1, '')
    ...>     UNION ALL SELECT i+1, substr(cmdline, i, 1) AS r FROM char_index WHERE r != ''
    ...> )
    ...> SELECT MAX(i) FROM char_index WHERE char_index.ch = ' ')) as java_main_class FROM processes WHERE name = 'java';
+-------+----------------------------+
| pid   | java_main_class            |
+-------+----------------------------+
| 2736  | com.company.app1.FirstApp  |
| 2737  | com.company.app2.SecondApp |
+-------+----------------------------+

This is, to me, some world-class SQL trickery. Stepping through, the WITH ... SELECT clause works like this.

osquery> WITH char_index(i, ch) AS (
    ...>   values(1, '')
    ...>   UNION ALL SELECT i+1, SUBSTR("foo bar baz", i, 1) as r FROM char_index WHERE r != ''
    ...> ) SELECT * FROM char_index;
+----+----+
| i  | ch |
+----+----+
| 1  |    |
| 2  | f  |
| 3  | o  |
| 4  | o  |
| 5  |    |
| 6  | b  |
| 7  | a  |
| 8  | r  |
| 9  |    |
| 10 | b  |
| 11 | a  |
| 12 | z  |
+----+----+

Adding the WHERE char_index.ch = ' ' gets us just the spaces:

osquery> WITH char_index(i, ch) AS (
    ...>   values(1, '')
    ...>   UNION ALL SELECT i+1, SUBSTR("foo bar baz", i, 1) as r FROM char_index WHERE r != ''
    ...> ) SELECT * FROM char_index WHERE char_index.ch = ' ';
+---+----+
| i | ch |
+---+----+
| 5 |    |
| 9 |    |
+---+----+

and of course adding MAX(i) gives the highest such index, 9. My expression then passes that entire thing into a SUBSTR(var, idx) clause to get the last element, and applies it to cmdline instead of a static string.

There’s an extensive schema listing on OSQuery’s website describing all the tables available in the latest version of OSQuery.