Kiwipycon command line

Giving your website a command line interface
Michael Hudson-Doyle
michael.hudson@linaro.org

Linaro and its mission
Linaro aims to make Linux work better on ARM processors

The Problem
The ARM ecosystem is very fragmented, and the kernel has a lot of copy and paste code
"Gaah. Guys, this whole ARM thing is a f*cking pain in the ass."
— Linus Torvalds, 17 Mar 2011
https://lwn.net/Articles/437170/

Enter Linaro!
"Linaro is a not-for-profit software engineering company investing in core Linux software and tools for ARM SoCs."
Also about educating the members in how to do open source development...

LAVA - Linaro Automated Validation
A bit part of Linaro is about automated validation:
Find regressions earlier
Also benchmark toolchain improvements
Maybe even power management changes too...

LAVA
We have a bunch of hardware

LAVA
Some scripts and tricks that can boot a board with a new kernel and run some tests.
Quick Demo
(ever the optimist)

LAVA
And a website that lets you see whats going on

The Problem (finally!)
We want to do things like trigger test runs when a kernel build finishes.
This basically means some kind of Remote Procedure Call (RPC).

Paranoia
For a bunch of reasons, we need some kind of security in our system:
The boards in our lab are a limited resource
Some risk of mischief
Eventually may have test results from unreleased hardware or benchmarks with licenses that forbid publication of results

Protocol Choices
We use XML-RPC
We didn't think about this very hard but it is well supported in most languages
Will probably add JSON-RPC support at some point for easier browser access

First idea: OAuth
An open protocol to allow secure API authorization in a simple and standard method from desktop and web applications.
– http://oauth.net/

The great thing about standards...
<bob2> kennethreitz: oauth
is a font of villany
and dispair
-- #python, Jun 09 11:55:08

Also doesn't solve our problem
OAuth specifies that various aspects of the request are signed, but not, crucially for us, the body of the request – an important detail, because in XML-RPC the body of the request is where all the important stuff is.

Transport Layer Security, here we come
If you're going as far as to cryptographically sign something, it's not much further to go to actually just encrypt it!

And what does everyone know about encryption?
Don't implement it yourself
(i.e. use HTTPS)

Back to Basic
And if you're operating over HTTPS, you might as well just just good old RFC 2617 Basic Authentication...
... but with tokens rather than passwords

Tokens > Passwords
Because we expect the RPC to be invoked from build systems and so on, there is a moderate chance of the token being leaked – so it should not let you take over the owning user's account.
In the future, a token might only let you access some APIs.

Also, we use SSO...
In addition we use Launchpad's SSO service for authentication, so most users don't have a LAVA password!

Show me the code!
On the server side, we've built a library that lets you add a authenticating XML-RPC to a Django project:
https://launchpad.net/linaro-django-xmlrpc
It includes views and models (and very very simple templates) for creating and managing tokens.

Server side code
example/api.py:
from linaro_django_xmlrpc.models import ExposedAPI
from linaro_django_xmlrpc.globals import mapper
class ExampleAPI(ExposedAPI):
def whoami(self):
if self.user:
return self.user.username
else:
return None
mapper.register(ExampleAPI)
in your urlconf:
url(r'', include('linaro_django_xmlrpc.urls')),

Client side library
This isn't properly factored yet really (it's it all mashed up with our toolkit for doing command line tools), but the code is in "lava-tool":
https://launchpad.net/lava-tool
It uses python-keyring for token management.

Client-side code
from lava_tool.authtoken import
AuthenticatingServerProxy, KeyringAuthBackend
auth_backend = KeyringAuthBackend()
auth_backend.add_token(
"user", "http://server/RPC2/", token)
sp = AuthenticatingServerProxy(
"http://user@server/RPC2/",
auth_backend=auth_backend)
print server.whoami()

Demo
(assuming the first one wasn't a disaster)

Conclusion
The lesson:
Don't try to be clever – just use HTTPS and Basic auth.
The code:
lp:linaro-django-xmlrpc
lp:lava-tool

Thanks for listening!
Any Questions?

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Kiwipycon command line

by Michael Hudson-Doyle

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