Understanding and Hardening Linux Containers [pdf]
nccgroup.trust
nccgroup.trust
Granted I realize the title is "Understanding and Hardening Linux Containers".
However, personally, this just illustrates my frustration and the frustration of others with the Linux world.
They exist in their own little echo chamber. Linux was not the first to create "containers" that are secure. There is no inclusion of other solutions outside Linux.
The reason other solutions do not have these problems is because the authors actually thought about the problem. And if the Linux camp would simply look outside their echo chamber long enough to see how others solved these problems before them this paper might not have been written.
It's just simply frustrating to watch Linux reinvent some wheels, poorly, time after time.
Flame on!
Everybody is just flapping on Linux containers. Meanwhile illumos and SmartOS are eating Linux's lunch with techology which has been working reliably in Swiss banks since 2006, and it is free open source software. What's not to love?
There are T-shirts which say "Go away or I will replace you with a very small shell script." Now it's "Go away or I will virtualize your Linux inside of SmartOS." The damn thing runs like a bandit, while Linux containers keep on flapping trying to find a working solution with papers like these. Why bother, the problem has already been solved, go run SmartOS and enjoy a working solution!
Then I tried Linux (Ubuntu) and everything just worked! It was also very easy to find guides on the web for most things Linux.
http://eng.joyent.com/manufacturing/bom.html
SmartOS being descended from Solaris has detailed manual pages built into the operating system, because when one runs a real UNIX, one is entitled to comprehensive documentation with lots of examples.
A lot of the Oracle Solaris documentation, which is also very comprehensive, applies to and can be used on illumos derivatives. The SmartOS wiki and the smartos-discuss mailing list are good sources of SmartOS specific enhancements. Did I mention the built-in man pages yet?
They would be eating Linux's lunch if they were used in any wider scale.
A primary objection to Solaris zones and a reason they're not used widely is that they run on Solaris and not on Linux.
Linux took 20 years to make its way into the enterprises, and well, SmartOS has to start somewhere. We are only at the beginning of the journey, but with one major difference: unlike Linux, which is still maturing, an illumos based operating environment has 37 years of enterprise abuse and hardening behind it.
> A primary objection to Solaris zones and a reason they're not used widely is that they run on Solaris and not on Linux.
What exactly is objectionable about running a Solaris-like operating environment? If it is software, SmartOS provides ~14,000 packages:
https://www.perkin.org.uk/posts/building-packages-at-scale.h...
When SmartOS or generally Solaris-descendants' zones start being anywhere near popular, then we'll talk about eating Linux's lunch. For now the situation doesn't look like that even remotely.
> What exactly is objectionable about running a Solaris-like operating environment?
To me -- not much at first sight. But there is the factor of familiarity, which is very, very important. There are plenty of sysadmins, you know, who can recover Linux from almost any failure, and gaining similar knowledge in different OS takes quite long time. Solaris derivatives (or BSDs, for that matter) are at huge disadvantage to those people.
By eating Linux's lunch I meant how good, reliable and capable the zones and lx-branded zones technology is. It is very reliable and very capable. It works very well while Linux is still trying to find itself within the cloud container paradigm: look at how many competing solutions there are on Linux in that space, and every single one of them exists because the other one lacked something, or did not do it in a satisfctory way. That is what I meant by everybody's flapping on Linux with containers.
Meanwhile, there are no such issues or problems in the illumos and SmartOS communities: the tech used there has been designed from the ground up to be secure and work for large enterprises, and unlike the Linux cloud technology, it has been in heavy use for ten years now. illumos and SmartOS are not trying to still find themsselves, because zones, ZFS, and Crossbow network virtualization already worked for years. Back in 2006 for instance, at a place where I worked, we were already packing eight Oracle databases per 32 GB RAM system, in production. Now it's 2016, and zones have only gotten better with the addition of KVM and Crossbow network virtualization.
> But there is the factor of familiarity, which is very, very important. There are plenty of sysadmins, you know, who can recover Linux from almost any failure, and gaining similar knowledge in different OS takes quite long time. Solaris derivatives (or BSDs, for that matter) are at huge disadvantage to those people.
As for those people, they had to learn Linux too; they can go back to the roots and learn a real UNIX the correct way now, and be glad that they have the opportunity to do so.
If one truly knows UNIX, one understands Linux on a much deeper level.
Could you then use idioms in their proper meaning, please? Because I only protested against claim that zones have taken a market share of Linux containers, which is very untrue, and at the same time not the claim you have made.
> As for those people, they had to learn Linux too; they can go back to the roots and learn a real UNIX the correct way now, and be glad that they have the opportunity to do so.
So, zones provide better platform because people can go back and learn Solaris? Or what?
Zones need to provide something tangible over containers for people to invest in learning different platform. Having just another tool, which merely does what one already can do with containers, only slightly slicker, but severly limited in applicability because parent platform is not familiar to all the colleagues, doesn't look like a good trade.
And note that we were only talking about familiarity. There are still other reasons, like little developers working on a given Solaris derivative, which doesn't give much confidence that any bugs that occur would be fixed, or a concern that the supported hardware list will be long enough.
eat lunch
eat someone's lunch
Sl. to best someone; to defeat, outwit, or win against someone.
http://idioms.thefreedictionary.com/eat+lunch
...It can refer to market share like you argue, but in a broader sense, this is at least how I understood the term eating someone's lunch.
> So, zones provide better platform because people can go back and learn Solaris? Or what?
No, Solaris (well, illumos, since nobody cares about Solaris any more) provides a better platform for learning and understanding UNIX. And with that comes the insight of writing better code in general, especially on Linux. For example, one is able to write completely portable shell code and deliver cleanly packaged software on Linux if one understands UNIX (in /opt, /etc/opt/, and /var/opt instead of /usr[/local] -- and that is just one trivial example).
zones are a fully working solution because they provide full security isolation, while running as regular processes with their own init(1M), instead of being forced to run Docker inside of KVM or XEN virtual machines to achieve that. And because processes inside of zones are just regular processes in the global zone, they only use as much resources as they need, and no more. With zones, one does not have to hard partition and preallocate memory and CPU to achieve full isolation, as is very often the case with running Docker inside of a virtual machine.
https://www.youtube.com/watch?v=0T2XFSALOaU
And because zones' storage is backed by ZFS, the data is guaranteed end-to-end integrity, and self-healing if the zpool is redundant (RAID1+0, RAIDZ, RAIDZ2).
Writing filesystems is hard: https://danluu.com/file-consistency/
For its part, illumos is the reference system as it is fully POSIX, XPG4, and SUS / UNIX03 compliant, so learning it means learning and mastering the standards.
And, once spoiled by all the nice features in illumos / SmartOS, going back to Linux feels like going back to skins and stone knives.
> ...It can refer to market share like you argue, but in a broader sense, this is at least how I understood the term eating someone's lunch.
It's still a far stretch to claim that zones win against containers. They could if we limited the field to just technical level, and then again, I would need to see some arguments why they actually are better.
>> So, zones provide better platform because people can go back and learn Solaris? Or what?
> No, Solaris [...] provides a better platform for learning and understanding UNIX.
You're confusing here learning unix with using it.
If one was at the stage of learning, Solaris could be fine, except there's much less material about it for newbies (especially about rough corners and stupid troubles, like "I ran `chmod -R 777 /'" or "I deleted my kernel"), and much, much less knowledgable people accessible to those newbies to learn from.
Now look at professional Linux sysadmins and programmers. They already have some knowledge about their OS and they're not likely to do a hard turn for different OS just for the sake of "understanding UNIX", as it would require quite large effort to just get to the point where they are already with Linux. Solaris would need to provide a really compelling function or feature to justify this effort, and all you said is "portability" (which most probably won't be necessary in most cases) and vague notion of "understanding UNIX".
EDIT: It was a little dishonest on my side to suggest that main selling points of Solaris derivatives were "understanding UNIX" and "writing portabile code". Solaris introduced ZFS and DTrace. But while it is said that ZFS with zones work well together, it still needs explaining why is it a significantly better combination than what Linux provides, and DTrace seems like a very distant benefit, less compelling each time a tool like Sysdig shows up.
How about no priority 1 incidents at 02:03 in the morning, resulting in sleepless nights until 07:30 - 08:30 every day during one's on call, wasted on stupid problems like ext3 filesystem corruption caused by lost writes (again: http://danluu.com/file-consistency/)? Is that a compelling enough reason?
No incidents at dead hours of the night. A programming environment fully supporting standards. Same software which runs on Linux. Guaranteed application binary interface backward compatibility: compile on oldest SunOS 5.# you can find, run on all the versions newer than that one. Change schedulers on the fly, as you need them. Realtime subsystem. kdb and mdb: the best post mortem analysis tools in the industry (what are those system administrators going to do when the kernel crashes so bad that it locks up and doesn't dump a stack trace?) Full security isolation and bare metal performance with zones.
Exhaustive documentation ("he who can read is clearly at an advantage"), much of it applicable to illumos / SmartOS:
http://docs.oracle.com/cd/E19253-01/817-1985/
Should I go on?
I won't have calls about corrupted ext3, because I use XFS, so not much of a point.
"No priority 1 incidents" is not a function of an operating system, so it can't be a compelling reason to switch. You would still need to elaborate why exactly Linux doesn't work, especially when it works well enough in most admins' perception.
> A programming environment fully supporting standards.
Becasue Linux doesn't support a very important standard of... Could you help me here? Nothing comes to my mind.
> Same software which runs on Linux.
Sweet. I should learn Solaris, so I can run the same software as I currently can on Linux.
Do you hear how ridiculous this point is?
> Guaranteed application binary interface backward compatibility: compile on oldest SunOS 5. you can find, run on all the versions newer than that one.
Only ABI of kernel and (probably) OS-supplied libraries, which is not that much when it comes to what most of the companies run.
> Change schedulers on the fly, as you need them. Realtime subsystem.
Of course, because Linux doesn't allow to change schedulers and has no realtime subsystem.
> kdb and mdb: the best post mortem analysis tools in the industry (what are those system administrators going to do when the kernel crashes so bad that it locks up and doesn't dump a stack trace?)
This is a very distant benefit. One needs to be accustomed with kernel-level code in the first place to make any use of these.
> Full security isolation and bare metal performance with zones.
You get bare metal performance with Linux containers as well, so not a strong point. Only the "full security isolation" could be a sensible reason, but then, it should be proven by close scrutiny. I haven't heard too much about people analyzing Solaris zones, so I'm not likely to be convinced out of thin air that this argument applies.
> Exhaustive documentation ("he who can read is clearly at an advantage"), much of it applicable to illumos / SmartOS:
> http://docs.oracle.com/cd/E19253-01/817-1985/
OK, let's go to booting chapter: http://docs.oracle.com/cd/E19253-01/817-1985/hboverview-2546...
This is barely enough for a trained sysadmin to learn how booting works and where to nudge when things go awry or how to do less standard tasks (e.g. I'm not sure how much time would it take me if I needed to build a custom live CD image; probably quite a lot, judging from boot(1M) man page).
Even if it's exhaustive, it suffers from not having much between step-by-step-and-don't-think instructions and deep documentation that requires prior understanding of the system.
> Should I go on?
You haven't provided many arguments that would be sensible reasons (let alone being strong reasons) to invest in migrating to Solaris.
I think we should disengage from this discussion. If I was in (what I believe is) your state of mind, I couldn't muster any good argument that would convince my interlocutor.
Thanks! It was a lot of hard work, I'm glad it's being well received and seems like people are generally finding it useful- the main point of writing it.
I would have liked to talk a lot more about other non-Linux solutions, but that's where most of the NCC Group consulting work has been, which was a main driver for why this info needs to be out there (companies not understanding container security or not "turning it up to 11" in places it needs to be). My background is also mainly Linux, so I stuck to what I know.
Hopefully someone else will release a similar paper on non-Linux solutions/unikernels/hybrid platforms?
There's plenty of room for someone to make a document specific to other platforms for a different audience. There's even room for someone to make a comparison of all platforms. It depends on your goal, your knowledge, and your intended audience.
It's that the paper, while describing the security short comings of the various solutions, illustrates the echo chamber I refer to.
"We have these security issues, that others do not have, but we are not going to look at how they solved these issues because, well, Linux!"
The paper, IMO, would have better served the audience had it included ideas and/or solutions people outside Linux-land developed to solve some of these issues that were written before Linux even attempted a "container".
You are free to disagree.
and how do you know the others solutions
are really secure? Linux is going to get
the most eyes, critics, scrutiny on this
because is way more widely used ...
1 - http://www.amazon.com/Facts-Fallacies-Software-Engineering-R...
[1] https://us-east.manta.joyent.com/bcantrill/public/ppwl-cantr...
Spender talks about it for a long time: https://grsecurity.net/~spender/interview_notes.txt
Linux developers fix security bugs in irresponsible ways, saying nothing about the attack vector or CVE's involved. Sometimes multiple vulnerabilities are addressed in the same patch, making hard to track the fix.
For more information see the exploit below: https://grsecurity.net/~spender/exploits/64bit_dos.c
The list of kernel vulnerabilities involving namespaces is bigger each day, as the paper shows, but the industry still uses "container" and "security" in the same quotes.
Out of curiosity, why do you think that Linux got such traction and the BSDs didn't? I keep hearing from the BSD camp that the BSDs are better than Linux at, well, pretty much everything, but there must be some reason why BSDs were not as performant for people than Linux distros.
Out of curiosity, why do you think that
Linux got such traction and the BSDs didn't?
Right around the same time, one Mr. Linus Torvalds was making his own OS.
1 - https://en.wikipedia.org/wiki/UNIX_System_Laboratories,_Inc.....
Complexity at scale: Orchestration frameworks (Rancher, MESOS/Aurora, Docker Swarm, LXD, OpenStack Containers, Kubernetes/Borg, etc) are only recently catching up to the container craze, there are too many competing models to list. Many have questionable or unaudited security or leave major requirements out, such as secret management. While containers may be easy to get working within a workstation or a few servers, scaling them up to production deployment is another challenge altogether, even assuming your application stack can be properly ``containerized''
From my understanding Google was one of the main contributors of the core features that have allowed containers on Linux. Specifically cgroups and LXC. And they have have been running containers for 10 years: https://research.google.com/pubs/pub43438.html
I'm not sure what you consider new, but it's definitely not super new to Google. I'm guessing your issue is that it's fairly new to being used in production across many companies, so security researchers are just starting to work on finding holes in it.
There's a distinction between containers the concept and Linux containers, of course, but yes. You've got it right.
The concept is not new.
This was made possible by the work done by Serge Hallyn, Stephane Graber, and others at Canonical. They delivered LXC and its integration with AppArmor, which in turn stood on top of the cgroups/namespaces work that Google contributed to the kernel. Ubuntu 12.04 was the release where the ability to securely run containers at scale became available to mere mortals.
This document is more an indictment of the current state of the Linux container ecosystem, rather than containers themselves. Don't conflate the two.
And I do not see how a generic container deployment solution can help with this as distribution of secrets are way too deployment/application specific.
If you want to have a large pool of generic hosts that can run any image, then you've just reduced the size of the pool for some images.
If you choose instead to make every secret available to every host, then you've just spread your individual application secrets across many hosts.
Also, how is secret management a major requirement? That term doesn't even exist outside of open source Silicon Valley trendsters, btw. In the enterprise, only people with regulatory requirements use it, and then it's just called password management or credential management. More important requirements are typically the configuration of the services on the network, basic network security & access control, application security, and the security and training of internal users.
Kubernetes does have a reasonable solution here: http://kubernetes.io/docs/user-guide/secrets/
But yes, since there's only one entropy pool, attackers can drain /dev/random, causing other programs that rely on /dev/random to block.
All I can say is: on newer kernels, attackers can still drain the pool by using the getrandom syscall, so unless you block that syscall, not mounting /dev/random does not increase the security.
Yes, that is what I was trying to say. I'll clarify it in a future version.
That's a good point, I'll include that! Thanks.
e.g. http://www.onkarjoshi.com/blog/191/device-dev-random-vs-uran... or http://security.stackexchange.com/a/14293/37
I'd say that's not entirely correct. At all.
> Joanna is also a core contributor and author of the high security Xen hypervisor desktop "CubesOS".
it's Qubes, not Cubes. Spelled correctly right in the URL the paper link to.
I agree with this part. Most containers aren't running as an unprivileged user. Those environments that do support it only support it in a very limited set of os/kernel/whatever versions. Somewhat concerning since containers are getting traction almost everywhere.
Appreciate your efforts. It is good to know that there are people pushing to get this working.
http://regex.info/i/pic/2005-09-06_16:03.28__00002.jpg
Ideas: Cross-linked polymer? Switch to glass? Too heavy. Carbon fiber, epoxy resin composite?
It's weird and wonderful that such technology infrastructure arose and such innovation happens. I'm curious how.
Too bad that Docker and other container solutions defaults to rather broad set of capabilities requiring to use things like
--cap-drop=ALL --cap-add=NET_BIND_SERVICE ...
Honest question: Are illumos zones or FreeBSD jails better designed or is just nobody looking for kernel bugs there? From a usability perspective both win (IMHO) against this Linux mess.
This document is really great through.
As Bryan Catrill has said in one of his talks:
"we walked the trail if tears since our customers were very large companies; if they had a problem, we had a problem!"
The illumos and smartos mailing lists are hyperactive, with bugs being fixed, and new functionality added, which even Oracle Solaris doesn't have -- just subscribe to those two mailing lists and see for yourself. I warn you in advance: be prepared to be buried under the vortex of e-mails.
Also, Illumos was forked off Solaris, and I'm sure that you know of Solaris' security.
Looking forward to your amendment and revised paper.
Trust me people have been looking for kernel bugs in FreeBSD to exploit jails since it was created. The record their speaks for itself. It's not a lack of eyeballs.
https://docs.docker.com/engine/security/trust/content_trust/
> Content trust is currently only available for users of the public Docker Hub. It is currently not available for the Docker Trusted Registry or for private registries.
> Currently, content trust is disabled by default. You must enable it by setting the DOCKER_CONTENT_TRUST environment variable.
How is the complete lack of image verification until explicitly enabled, and only on public images, a "strong default"?
I'm also mystified by the row for SELinux, where rkt has Optional in scary yellow for some reason, and the other two do not. I suspect that table was the whole point of the independent review and it is fulfilling its purpose handily for Docker. I haven't even read the report and I can identify four suspicious discrepancies in that table alone.
ETA: Compare how the author describes Docker to rkt (it's rkt, not Rkt, too): http://imgur.com/a/D6nEw
- For the table w/ SELinux row, Rkt is optional "scary" yellow because it only supports a single MAC implementation, it isn't very portable, and it's not enabled by default, vs LXC and Docker which both have quite strong MAC policies by default. Trying to parse all the info down into a table was honestly quite difficult (balancing being able to read it without a million footnotes for each point). Hopefully readers don't take all their take-aways from the table, and read the paper in full.
- I used Rkt for the name and rkt for the command. Seemed to help consistency.
Thanks for your feedback.
I'm a little confused around the SELinux issue. SELinux is inherently unportable - each distribution has its own policy (generally based on refpolicy, but sometimes fairly divergent), and it's basically impossible for an application to ship a policy that's compatible with more than one distribution. Rkt's SELinux design inherits from SVirt in such a way that in most cases it'll just work with a distribution's existing SELinux policy. It's fair to say that the number of distributions that ship policy that works with Docker is larger than for rkt, but this is fundamentally about distribution priorities rather than technological choices. On Fedora, rkt should provide identical SELinux confinement to Docker - on CoreOS it'll be better, since we support SELinux on overlayfs as well. Whether SELinux is enabled or not is (again) a distribution choice. Fedora ship with SELinux enabled by default, and both rkt and Docker will use it as a result.
And Docker simply screenshot the table, so noble goal, but...
I suppose I could remark upon MESOS, Rkt, and so on, and how getting names right is important because it characterizes the rest of your thoughts and analysis of the things you're studying, but I'll stick with the question I started with here.
What makes you think this? It is 100%, patently false. Private notary servers can be deployed alongside private registry servers without problem. See here for docs on how to do it: https://github.com/docker/notary/blob/master/docs/running_a_...
The docs I linked and quoted, written by your own organization and helpfully pasted into the point I made?
I'm glad to see it's possible (if cumbersome), but I ruled Docker out for this purpose based on the exact link I just pasted. I also followed up and didn't see a "hey, you can sign private registries" bullet in your blog post responding to this paper, or much of anywhere, and Googling "docker sign private registries" doesn't go anywhere.
I'm still unsure why I'd stand up several daemons to accomplish signing a file, but that's a side point.
----
ETA: I can no longer reply because I've burned my precious HN comment budget commenting upon this paper (sorry, blame HN), so here's what I would reply to you downthread:
> 1. We have to host the signatures somewhere, so we host them in a store we call the notary server.
We've had this solved for a long time with .asc files, and Docker is already shipping an HTTP server or six. Shit, extend the Docker format and put the signature on each layer. There's a lot of prior art from RPM and dpkg in particular on how this can be done without writing yet another Docker daemon to run.
I'm sorry, I have to call bullshit, here. Docker is a very strong daemon-for-everything engineering culture, and that's the only reason it exists. It's also why folks are competing with you, because there are three or four different daemons in the Docker ecosystem that simply should not exist. Including dockerd.
> Think serving an outdated container with known-vulnerable software. Sadly, most artifact signing systems do not mitigate this attack today,
Because it's out of scope of a signature. That is conflating a signature with content revocation, which is a different problem altogether. A signature is an attestation of certain properties of data, and "is no longer valid content because circumstances changed after it was signed" is not one of them. The validity of the content is orthogonal to its signature. That known-vulnerable container is still a valid signature, and it's overreaching to expect a signature system to solve that problem. That is solvable in other ways.
Known-bad OpenSSL is still signed in repositories. And valid. And that's fine, because it's a separation of concerns; you get non-repudiation, integrity, all that stuff from a signature scheme. Upgrading to gatekeeping content on top of signatures indicates to me a fundamental misunderstanding of the problem ("can I run this?" instead of "this is an authenticated, intact image that came from where I expect"), which concerns me. You can solve the problem you present in other ways.
Mixing in the term "replay attack" is extremely confusing and I think diluting your point, because it is baffling me and really does not apply to what you are saying.
Most of your points are a criticism of TUF, of which Notary and Docker Content Trust are an implementation. Based on your comments I believe you're not familiar with TUF and the scope of problems it solves. Here's a good resource to learn more about it: https://theupdateframework.github.io
You clearly are not a fan of Docker and I respect your opinion, I don't really want to engage in that aspect of the discussion. Now, on the specific topic of secure content distribution, I hope you won't let your bias against Docker get in the way of understanding the benefits of TUF. It does improve the state of the art in secure content distribution, and you should really take the time to understand it and perhaps revisit some of your opinions. We're leveraging it in Docker and sharing our implementation, but you don't have to use Docker to use Notary or TUF.
If after reading about TUF you have specific criticism of it, I would be interested to hear about it.
Let's write a spec:
- Verify integrity and authenticity of a Docker image
The logical implementation:
- Digital signatures, detached or otherwise
Your implementation:
- Multiple complex, daemonic systems to reinvent software updating and, incidentally, signatures based on TUF
Your rationale:
- Digital signatures are not useful alone
So those of us who are aware of the limitations are left out in the cold, because we can't point gpg at a Docker image and just get the problem done. We have to learn this entire system Docker has created that's going to bring a grand unified software updating future. Maybe I have my own Omaha updater already. Maybe I just want dockerd to validate a signature. It is your prerogative to steer Docker toward crafting novel daemon engineering for every possible scenario, but that's the criticism I'm going to levy, whether you want to engage it or not.
The fundamental problem here is composability versus platform. My critique is not of TUF, of which I am not only familiar but excited. My critique is that organizationally at Docker, you take a problem like "sign an image," which is a perfectly useful primitive in every software distribution system on the planet, and say "that's not enough. We need a platform." You are dictating how my updating infrastructure works and then saying you've solved signatures. Which is technically accurate, I suppose.
I'm also pretty much over critique of Docker being cast as my not getting and/or understanding it. Believe me, Solomon, I get it, and I understand that you want to caricature everyone who disagrees with your strategy as biased against you. (That's actually the third time I can recall you making my criticism of Docker personal. I have no anti-Docker bias. I believe others are implementing what you're working on better and you've simply got the warchest, which is vastly different than having a bias. I used the shit out of ZeroRPC and I've respected a whole lot of your work since then. Come on.)[0]
We're talking about signing a file. Signing. A file. Which I cannot do without a whole shitload of infrastructure that I do not want (including MySQL, apparently), which is a systemic issue with Docker all the way back to dockerd.
Edit: [0]: 484 days ago we discussed exactly this, and here we are again, condescending criticism: https://news.ycombinator.com/item?id=8789181
Notary, the underlying project that implements Docker's Content Trust feature, is an implementation of The Update Framework (TUF). Generally, you want a software update system to deal with a whole host of issues. Just solving "is this content signed" actually achieves very little. Survivable key compromise, freshness guarantees, resilience against mix-and-match attacks are all critical to building a system that actually meets real-world use cases and attacks. Threshold signing and signing delegation are additional features that you get when using TUF, which help with splitting the ability to sign across multiple individuals or systems.
You seem to be interested in this topic. I recommend you read a couple of papers to get some more background on why TUF exists and what problems it solves. A key point would be to understand why TUF deals with signed collections of software instead of just individual signed objects.
Start here to get an overview of The Update Framework:
1. Overview: https://theupdateframework.github.io/
2. Specification: https://github.com/theupdateframework/tuf/blob/develop/docs/...
Existing package managers and their shortcomings are covered in these two papers:
1. https://isis.poly.edu/~jcappos/papers/cappos_pmsec_tr08-02.p...
2. https://isis.poly.edu/~jcappos/papers/cappos_mirror_ccs_08.p...
1. We have to host the signatures somewhere, so we host them in a store we call the notary server.
2. Notary has a concept of timestamping, so we spin up a timestamping server alongside a notary server that can guarantee the freshness of the data. We use a separate server so that folks can segment the timestamp signing functionality from the signature metadata serving functionality. This helps allow separation of concerns.
Timestamping is important because it can help prevent replay attacks where old, validly signed data is served to clients. Think serving an outdated container with known-vulnerable software. Sadly, most artifact signing systems do not mitigate this attack today, but we wanted to make sure ours would.
Open invitation to anyone here: Our implementation of TUF via notary has been serving us well. If you decide to try it out and run in to any snags let me know and I can help you with getting it up and running. Contact info can be found in my profile.
I found six inaccuracies in as many minutes after opening the PDF and scrolling to random pages. So I'm not sure that's true. I'm also not the only one making that claim, `spender has too:
https://twitter.com/grsecurity/status/722935691114512385?lan...
I don't want to knock the paper too hard without actually sitting down and reading it (which I'm going to do tonight, and I won't dump raw notes on HN until I've given the paper a serious chance), but I'm not encouraged right off the bat. I've been deep in the rkt integration hole and a lot of stuff referring to rkt is very rough and surface-level and, in five of the cases I mentioned, blatantly factually inaccurate. Same with Docker, too, actually, though the paper is quite obviously partisan (see http://imgur.com/a/D6nEw for example).
I tried extremely hard to not be "partisan", and I don't think I am kind to any container platform, but it's hard to argue where Docker is vs Rkt in terms of security (apart from possibly hw virtualization in Rkt Stage 1). I agree some of the Rkt stuff is higher level, mostly because after a large number of container assessments at some major companies, I have yet to come across Rkt. Most of my research comes from my own brief analysis, and the analysis of some peers. Maybe a future version will cover it more in-depth.