[Bro-Dev] Proposal: Operating the Bro package manager offline

[Robin Sommer]

At BroCon several people pointed out a need to install Bro packages on
machines that do not have a direct external connection. One idea would
be some kind of proxy scheme where an intermediary git repository
mirrors packages locally; bro-pkg would then pull from there. However,
I don't think any of us really liked that idea much. After a few
rounds of discussions, Seth and I came up with a different idea that
seems easier to manage: extending bro-pkg to bundle packages into
deployment files that can be easily pushed to Bro systems simply by
copying them over. 

I’ve tried to flesh this out a bit more, and would be interested to
hear what you all think about this approach. And @Jon: Do you think
this would be doable that way?

Here’s the idea:

1. Generally, one first uses bro-pkg as usual to install packages onto
   a local Bro system that does have external Internet connectivity
   (this could be just a dummy Bro installation). One installs new
   packages there, updates existing ones, etc., until reaching a state
   that one wants to push out to the actual Bro system.

2. We add a new “bundle” command to bro-pkg that serializes the
   current state of packages into a single file on disk, a “package
   bundle”. The bundle contains the complete content of all currently
   installed packages, using some kind of suitable container format
   (could be just a ZIP file, or whatever works; the internal
   representation doesn’t really matter).

3. Users create such a bundle on the local system and then simply copy
   that bundle file over to all target Bro machines that do not have a
   external connectivity themselves, using whatever mechanism they
   have available (e.g., just scp; or maybe through some configuration
   management system like Ansible etc.).

4. On the target machine, one runs a corresponding “bro-pkg unbundle”
   command on that bundle file. That command will completely replace
   the system’s current set of packages with the bundle’s content. As
   a result, that machine will now have exactly the same packages
   installed as the original system.

This would be the general scheme. A couple of people I talked to at
BroCon confirmed that this would offer a viable solution for them, and
that they would indeed much prefer copying files around over
maintaining local git mirrors.

Some additional thoughts on variations/extensions of this basic scheme:

- I’m not quite sure if the bundle should contain just the packages
  themselves or further bro-pkg state as well, such as which packages
  are currently loaded. Right now I’m learning towards saying “just
  the packages”; that would basically treat bundles just as a
  transport mechanism to get packages over to another box. The actual
  Bro machines would still keep control over which packages to
  actually load, etc.

- As it is described above, Step 1 would require having a local Bro
  installation into which packages get installed before they can be
  bundled up. It would be nice to have a mode where bro-pkg can
  operate without having a Bro around at all, just downloading
  packages locally somewhere for bundling them up. I could also see
  offering an even simpler mode where one simply lists packages to
  bundle on the command-line: “bro-pkg bundle <pkg1> <pkg2> <pkg3>”.
  That would be particularly useful with configuration management
  systems I think.

- It would be neat if bro-pkg's Python library exposed operations to
  inspect & retrieve the content of a bundle, such as iterating over
  the packages inside a bundle and iterating over the files inside a
  package. That way one could easily build target-side scripts that
  process and validate bundles before going ahead and installing them
  (e.g., imposing custom restrictions on what kind of packages one
  allows to put in place; or ensuring that a bundle always contains a
  set of packages the site deems mandatory, to avoid configuration
  mistakes; or even just logging what gets pushed out).

What do you guys think about this?

Robin

-- 
Robin Sommer * ICSI/LBNL * robin at icir.org * www.icir.org/robin