Download shared files for agent groups dinamically

[TJOSERAFAEL]

…and agents.

To use this new feature put a "files.yml" inside /var/ossec/etc/shared
This file will be parsed every time we restart the manager.

An example of the files.yml file:

groups:
  default:
    files:
      agent.conf: http://example.com/agent.conf
      rootcheck.txt: https://example.com/rootcheck.txt
      merged.mg: http://example.com/merged.mg
    poll: 15

  mygroup2:
    files:
      agent.conf: http://example.com/agent.conf
    poll: 200

agents:
  001: default
  002: group_test

If a group contains merged.mg file the manager will push it to the agents belonging to the specified group.

In the agents: section we can assign a group to specific agents if the group the belong is the "default" group.
For example when we register an agent at first it belongs to the default group. If we assign the agent to another group in the agents: section, the configuration for that group will be pushed to that agent.

If we have errors on the yaml file, we can spot them by looking at the /var/ossec/logs/ossec.log file

[vikman90]

This PR is related to issue #468.

[vikman90]

• Prevent depending on autoconf, automake or libtool.
• Enable compilation for Windows agents.
• Enable compilation for macOS.
• Enable compilation for BSD.
• Enable compilation for Solaris 11.
• Attempt to reload YML file once per loop, not once per group.
• Try to exclude libyaml and libcurl from agents.

[jesuslinares]

Hi guys,

That syntax is not YML:

• Settings must not be variable ("rootcheck.txt", "merged.mg", etc.).
• List members are denoted by a leading hyphen (-) with one member per line, or enclosed in square brackets ([ ]) and separated by comma space (, ).
• https://en.wikipedia.org/wiki/YAML#Syntax

In addition, it is not descriptive:

• files.yml should be changed for something more auto-descriptive.
• If "merged" is present, the other files will be ignored. I recommend using different settings and show a warning if both settings are used at the same time.

Example:

group-configurations:
  - name: group-default
    download_files:
      - name: agent.conf
        url: http://example.com/agent.conf
      - name: rootcheck.txt
        url: https://example.com/rootcheck.txt
    download_merge: http://example.com/merged.mg
    poll: 15

  - name: group-mygroup2
    download_files:
      - name: agent.conf
        url: http://example.com/agent.conf
    poll: 200

group-assignments:
  - agent_id: 001
    group: default

  - agent_id: 002
    group: group_test

Regards,
Jesus.