Archive for the ‘Ubuntu Server’ Category

OpenStack Essex: the last mile

April 4, 2012 1 comment

At the time I’m writing this,  we have final release candidates published for all the components that make up OpenStack 2012.1, codenamed “Essex”:

  • OpenStack Compute (Nova), at RC3
  • OpenStack Image Service (Glance), at RC3
  • OpenStack Identity (Keystone), at RC2
  • OpenStack Dashboard (Horizon), at RC2
  • OpenStack Storage (Swift) at version 1.4.8

Unless a critical, last-minute regression is found today in these proposed packages, they should make up the official OpenStack 2012.1 release tomorrow ! Please check out those tarballs for a last check, and don’t hesitate to ping us on IRC (#openstack-dev @ Freenode) or file bugs (tagged essec-rc-potential) if you think you can convince us to reroll.

Those six months have been a long ride, with 139 features added and 1650 bugs fixed, but this is the last mile.


OpenStack developers meeting at FOSDEM

January 27, 2012 3 comments

Next week, the European free and open source software developers will converge to Brussels for FOSDEM. We took this opportunity to apply for an OpenStack developers gathering in the Virtualization and Cloud devroom.

At 6pm on Saturday (last session of the day), in the Chavanne room, we will have a one-hour town hall meeting. If you’re an existing OpenStack contributor, a developer considering to join us, an upstream project developer, a downstream distribution packager, or just curious about OpenStack, you’re welcome to join us ! I’ll be there, Stefano Maffulli (our community manager) will be there, and several OpenStack core developers will be there.

We’ll openly discuss issues and solutions about integration with upstream projects, packaging, governance, development processes, community or release cycles. In particular, we’ll have a distribution panel where every OpenStack distribution will be able to explain how they support OpenStack and discuss what we can improve to make things better for them.

And at the end of the session we can informally continue the discussion around fine Belgian beers or their famous Carbonade !

Making more solid OpenStack releases

January 18, 2012 3 comments

As we pass the middle of the Essex development cycle, questions about the solidity of this release start to pop up. After all, the previous releases were far from stellar, and with more people betting their business on OpenStack we can’t really afford another half-baked release.

Common thinking (mostly coming from years of traditional software development experience) is that we shouldn’t release until it’s ready, or good enough, and calls early for pushing back the release dates. This assumes the issue is incidental: that we underestimated the time it would take our finite team of internal developers working on bugs to reach a sufficient level of quality.

OpenStack, being an open source project produced by a large community, works differently. We have a near-infinite supply of developers. The issue is, unfortunately, more structural than incidental. The lack of solidity for a release comes from:

  • Lack of focus on generic bugfixes. Developers should work on fixing bugs. Not just the ones they filed or the ones blocking them in their feature-adding frenzy. Fixing identified, targeted, known issues. The bugtracker is full of them, but they don’t get attention.
  • Not enough automated testing to efficiently catch regressions. Even if everyone was working on bug fixes, if half your fixes end up creating a set of regressions, then there is no end to it.
  • Lack of bug triaging resources. Only a few people work on confirming, triaging and prioritizing the flow of incoming bugs. So the bugs that need the most attention are lost in the noise.

For the Diablo cycle, we had less than a handful of people focused on generic bugfixing. The rest of our 150+ authors were busy working on something else. Pushing back the release for a week, a month or a year won’t help OpenStack solidity if the focus doesn’t switch. And if our focus switches, then there will be no need for a costly release delay.

Acting now to make Essex a success

During the Essex cycle, our Project Technical Leads have done their share of the work by using a very early milestone for their feature freeze. Keystone, Glance and Nova will freeze at Essex-3, giving us 10 weeks for bugfixing work (compared to the 4 weeks we had for Diablo). Now we need to take advantage of that long period and really switch our mindset away from feature development and towards generic bug fixing.

Next week we’ll hit feature freeze, so now is the time to switch.  If we could:

  • have some more developers working on increasing our integration and unit test coverage
  • have the rest of the developers really working on generic bug fixing
  • have very active core reviewers that get more anal-retentive as we get closer to release, to avoid introducing regressions that would not be caught by our automated tests

…then I bet that it will lead to a stronger release than any delaying of the release could give you. Note that we’ll also have a bug squashing day on February 2 that will hopefully help us getting on top of old, deprecated and easy fixes, and give us a clear set of targets for the rest of the cycle.

That’s on our ability to switch our focus that hinges the quality of future OpenStack releases. That’s on what we’ll be judged. The world awaits, and the time is now.

Virtualization & Cloud devroom at FOSDEM

January 13, 2012 Leave a comment

The Free and Open source Software Developers’ European Meeting, or FOSDEM, is an institution that happens every year in Brussels. A busy, free and open event that gets a lot of developers together for two days of presentations and cross-pollination. There are typically the FOSDEM main tracks (a set of presentations chosen by the FOSDEM organization) and a set of devrooms, which are topic-oriented or project-oriented and can organize their own schedule freely.

This year, FOSDEM will host an unusual devroom, the Virtualization and Cloud devroom. It will happen in the Chavanne room, a 550-seat auditorium that was traditionally used for main tracks. And it will last for two whole days, while other devrooms typically last for a day or a half-day.

The Virtualization and Cloud devroom is the result of the merging of three separate devroom requests: Virtualization, Xen and OpenStack devrooms. It gives us a larger space and a lot of potential for cross-pollination across projects ! We had a lot of talks proposed, and here is an overview of what you’ll be able to see there.

Saturday, February 4

Saturday will  be the “cloud” day. We will start with a set of talks about OpenStack, past, present and future. I will do an introduction and retrospective of what happened last year in the project, Soren Hansen will guide new developers to Nova, and Debo Dutta will look into future work on application scheduling and Donabe. Next we’ll have a session on various cloud-related technologies: libguestfs, pacemaker-cloud and OpenNebula. The afternoon will start with a nice session on cloud interoperability, including presentations on the Aeolus, CompatibleOne and Deltacloud efforts. We’ll continue with a session on cloud deployment, with a strong OpenStack focus: Ryan Lane will talk about how Wikimedia maintains infrastructure like an open source project, Mike McClurg will look into Ubuntu+XCP+OpenStack deployments, and Dave Walker will introduce the Orchestra project. The day will end with a town hall meeting for all OpenStack developers, including a panel of distribution packagers: I will blog more about that one in the next weeks.

Sunday, February 5

Sunday is more “virtualization” day ! The day will start early with two presentations by Hans de Goede about Spice and USB redirection over the network. Then we’ll have a session on virtualization management, with Guido Trotter giving more Ganeti news and three talks about oVirt. In the afternoon we’ll have a more technical session around virtualization in development: Antti Kantee will introduce ultralightweight kernel service virtualization with rump kernels, Renzo Davoli will lead a workshop on tracing and virtualization, and Dan Berrange will show how to build application sandboxes on top of LXC and KVM with libvirt. The day will end with another developers meeting, this time the Xen developers will meet around Ian Campbell and his Xen deployment troubleshooting workshop.

All in all, that’s two days packed with very interesting presentations, in a devroom large enough to accomodate a good crowd, so we hope to see you there !

Ending the year well: OpenStack Essex-2 milestone

December 20, 2011 1 comment

2011 is almost finished, and what a year it has been. We started it with two core projects and one release behind us. During 2011, we got three releases out of the door, grew from 60 code contributors to about 200, added three new core projects, and met for two design summits.

The Essex-2 milestone was released last week. Here is our now-regular overview of the work that made it to OpenStack core projects since the previous milestone.

Nova was the busiest project. Apart from my work on a new secure root wrapper (detailed on previous articles of this blog), we added a pair of OpenStack API extensions to support the creation of snapshots and backups of volumes, the metadata service can now run separately from the API node, network limits can now be set using a per-network base and a per-flavor multiplier, and a small usability feature lets you retrieve the last error that occurred using nova-manage. But Essex is not about new features, it’s more about consistency and stability. On the consistency front, the HA network mode was extended to support XenServer, KVM compute nodes now report capabilities to zones like Xen ones, and the Quantum network manager now supports NAT. Under the hood, VM state transitions have been strengthened, the network data model has been overhauled, internal interfaces now support UUID instance references, and unused callbacks have been removed from the virt driver.

The other projects were all busy starting larger transitions (Keystone’s RBAC, Horizon new user experience, and Glance 2.0 API), leaving less room for essex-2 features. Glance still saw the addition of  a custom directory for data buffering. Keystone introduced global endpoints templates and swauth-like ACL enforcement. Horizon added UI support for downloading RC files, while migrating under the hood from jquery-ui to bootstrap, and adding a versioning scheme for environment/dependencies.

The next milestone is in a bit more than a month: January 26th, 2012. Happy new year and holidays to all !

Improving Nova privilege escalation model, part 3

November 30, 2011 8 comments

In the previous two posts of this series, we explored the deficiencies of the current model and the features of an alternative implementation. In this last post, we’ll discuss the advantages of a Python implementation and open discussion on how to secure it properly.

Python implementation

It’s quite easy to implement the features that were mentioned in the previous post in Python. The main advantage of doing so is that the code can happily live inside Nova code, in particular the filters definition files can be implemented as Python modules that are loaded if present. That solves the issue of shipping definitions within Nova and also the separation of allowed commands based on locally-deployed nodes. The code is simple and easy to review. The trick is to make sure that no malicious code can be injected in the elevated rights process. This is why I’d like to present a model and open it for comments in the community.

Proposed security model

The idea would be to have Nova code optionally use “sudo nova-rootwrap” instead of “sudo” as the root_helper. A generic sudoers file would allow the nova user to run /usr/bin/nova-rootwrap as root, while stripping environment variables like PYTHONPATH. To load its filters definitions, nova-rootwrap would try to import a set of predefined modules (like nova.rootwrap.compute), but if those aren’t present, it should ignore them. Can this model be abused ?

The obvious issue is to make sure sys.path (the set of directories from which Python imports its modules) is secure, so that nobody can insert their own modules in the process. I’ve given some thoughts to various checks, but actually there is no way around trusting the default sys.path you’re given when you start python as root from a cleaned env. If that’s compromised, you’re toasted the moment you “import sys” anyway. So using sudo to only allow /usr/bin/nova-rootwrap and cleaning the environment should be enough. Or am I missing something ?

Insecure mode ?

One thing we could do is check that sys.path all belongs to root and refuse to run in the case it’s not. That would tell the user that his setup is insecure (potentially allowing him to bypass that by running “sudo nova-rootwrap –insecure” as the root_helper). But that’s a convenience to detect insecure setups, not a security addition (the fact that it doesn’t complain doesn’t mean you’re safe, it could mean you’re already compromised).

Test mode ?

For tests, it’s convenient to allow to run code from branches. To allow this (unsafe) mode, you would tweak sudoers to allow it to run $BRANCH/bin/nova-rootwrap as root, and prepend “..” to sys.path in order to allow modules to be loaded from $BRANCH (maybe requiring –insecure mode for good measure). It sounds harmless, since if you run from /usr/bin/nova-rootwrap you can assume that /usr is safe… Or should that idea be abandoned altogether ?


Nothing beats peer review when it comes to secure design. I call all Python module-loading experts and security white-hats out there: would this work ? Are those safe assumptions ? How much do you like insecure and test modes ? Would you suggest something else ? If you’re one of those that can’t think in words but require code, you can get a glimpse of work in progress here. It will all be optional (and not used by default), so it can be added to Nova without much damage, but I’d rather do it right from the beginning 🙂 Please comment !

Improving Nova privilege escalation model, part 2

November 25, 2011 5 comments

In the previous post in this series we explored the current privilege escalation model used in OpenStack Compute (Nova), and discussed its limitations. Now that we are able to plug an alternative model (thanks to the root_helper option), we’ll discuss in this post what features this one should have. If you think we need more, please comment !

Command filters

The most significant issue with the current model is that sudoers filters the executable used, but not the arguments. To fix that, our alternative model should allow precise argument filtering so that only very specific commands are allowed. It should use lists of filters: if one matches, the command is executed.

The basic CommandFilter would just check that the executable name matches (which is what sudoers does). A more advanced RegexpFilter would check that the number of arguments is right and that they all match provided regular expressions.

Taking that concept a step further, you should be able to plug any type of advanced filter. You may want to check that the argument to the command is an existing directory. Or one that is owned by a specific user. The framework should allow developers to define their own CommandFilter subclasses, to be as precise as they want when filtering the most destructive commands.

Running as

In some cases, Nova runs, as root, commands that it should just run as a different user. For example, it runs kill with root rights to interact with dnsmasq processes (owned by the nobody user). It doesn’t really need to run kill with root rights at all. Filters should therefore also allow to specify a lower-privileged user a specific matching command should run under.

Shipping filters in Nova code

Filter lists should live within Nova code and be deployed by packaging, rather than live in packaging. That allows people adding a new escalated command to add the corresponding filter in the same commit.

Limiting commands based on deployed nodes

As mentioned in the previous post, nova-api nodes don’t actually need to run any command as root, but in the current model their nova user is still allowed to run plenty of them. The solution for that is to separate the command filters based on the type of node that is allowed to run them, in different files. Then deploy the nova-compute filters file only on nova-compute nodes, the nova-volume filters file only on nova-volume nodes… A pure nova-api node will end up with no filters being deployed at all, effectively not being allowed any command as root. So this can be solved by smart packaging of filter files.

Missing features ?

Those are the features that I found useful for our alternative privilege escalation model. If you see others, please comment here ! I’d like to make sure all the useful features are included. In the next post, we’ll discuss a proposed Python implementation of this framework, and the challenges around securing it.