Comment by bkor | Hacker News Reader

Comment by bkor | Hacker News Reader

Systemd makes it easy to add additional limitations to every service you're running. More easily restrict all your services (NTP client, DNS caching server, etc).

It adds an easy to use method to restrict all of the daemons and services that someone might be running. Further, because the unit files are often shipped with the daemon/service, it'll do this by default on every install. Not just to the ones which have been looked at by a sysadmin. So a standard RHEL server by default has more restrictions than before.

The examples are pretty unconvincing IMO. The article talks about an email server. Systemd will provide an easy method to not have one service read the other one. In the examples it talks about email server and a web server. But completely ignores that someone will not just target that specific service, you could just as well compromise the NTP client and then move from there to another service.

Obviously systemd is just one small layer and security is not a yes/no thing. But why then talk specifically about systemd? The article seems to suggest that it's better to not use these abilities. This goes against the usual defence in depth security IMO.

> Obviously systemd is just one small layer and security is not a yes/no thing. But why then talk specifically about systemd? The article seems to suggest that it's better to not use these abilities.

The claim is not that it's better not to use these capabilities (which in any case do not require systemd; there are any number of ways to achieve the same thing). The claim is simply that systemd does not offer a substantial enhancement to system security, and that perhaps the increased attack surface offered by systemd itself outweighs any security benefit it provides to the services running under it.

Stating that his claim is something else doesn't make it true. If you read the article he's saying things such as:

1. Things should be written in different (safer) languages.

2. That a compromise in a mail server is already bad so having systemd protect the mail server according to him does NOT help

At least 50% is spend on those bits. Those are poor arguments to make. Systemd adds additional capabilities to make the overall system safer. You can do both. He stated nothing about an increased attack surface.

Of course I read the article. Maybe you didn't?

> 2. That a compromise in a mail server is already bad so having systemd protect the mail server according to him does NOT help

Right, the point of which is, as I said: systemd does not offer a substantial enhancement to system security

> He stated nothing about an increased attack surface.

He made reference to "baggage" which could mean many things. But either way the argument runs the same: systemd may offer some enhancement to security, but not a substantial one, not one that can only be achieved by using systemd, and not one that's worth the cost of using systemd.

This is exactly my argument! Thank you.

>Systemd makes it easy to add additional limitations to every service you're running

So does chroot. And so does jails. And posix capabilities. And cgroups...

I think he is being downvoted because he is factual wrong. Could someone please elaborate with details?

one of the arguments against systemd is that it consolidates several scriptable and bug-prone isolated scripts into a binary. This is introducing it's own risks that require upstream interaction to fix a small issue normally a sysadmin without knowledge of C can hot-fix locally. Considering the non existence of a systemd developer community, it's pretty risky.

There are similar arguments (pro/against) docker where 2 camps, one saying it's poison & bloat the other the best thing since tabbed browsing.

People get so riled up because they're unwilling to acknowledge that they're just tools that make lot sense for solving specific issues. Everyone keeps looking for silver bullets. Problems start when one camp tries to become the de-facto standard (not just the tool but also the processes that come with it). Also people are way to scared of code-forks IMHO. The "fail quick, fail fast" mentality should apply here too. Some healthy competition and a willingness to let certain projects just wither and die should be a good thing ...

> Considering the non existence of a systemd developer community, it's pretty risky.

There's also the fact that it's written in C. Writing security-sensitive software in C in 2016 is, in general, a grievous mistake. No, other languages are not perfect; yes, other languages have their own issues; regardless, C is worse than most. Buffer overflows, memory management, lack of type safety — Just Say No™.

It's an acceptable language for writing the piece of software that init is supposed to be. However, systemd is for more complicated and integrated and unsafe than that piece of software.

> It's an acceptable language for writing the piece of software that init is supposed to be.

Is it though? Although I can't think of a lot of vulnerabilities to be concerned of in PID 1, I can think of a few (perhaps something to do with reaping zombies?). Why even allow for that possibility? I see no reason why init(1) couldn't be written in Lisp, or Python (although the speed might not be great), or Go, or Rust, or Haskell, or ML.

PID 1 shouldn't have anything complicated about it. A comp sci student should be able to write it in 10 minutes. This is a solved problem[1].

A run control system, which should be a completely separate project, could easily be written in a higher-level language than C. For instance, the traditional Linux RC system is written in sh, and the official GNU RC system[2] is written in scheme.

Daemon run control isn't a domain where performance is crucial; transparency is much more important there, so the argument for using a higher level language to control daemons is pretty strong.

[1] http://git.suckless.org/sinit/

[2] https://www.gnu.org/software/shepherd/

Yep. Pretty much. The setup is that you have your init, which handles startup, shutdown, reaping, and runs your RC. From there, you'll run process montoring for daemons (this is sometimes integrated into rc, sometimes spun out, resulting in runit, s6, and the rest of the daemontools family). This is sometimes mashed together into one program. Sometimes RC and init are the same, and process monitoring is spun out. But that's the pattern. Most RCs and process managers also have the ability to run as PID 1 if you want them to, and many do. But it's not necessary, and it is a security liability (although not as much of one as systemd, which does so much more than all of this, and which people are trying to expose to the internet directly).

> which people are trying to expose to the internet directly

[citation needed].

Bows

Gladly, good sir.

https://cfp.systemd.io/en/systemdconf_2016/public/events/21

Sit back, and witness the insanity.

That's funny, because that's the same link referenced in the blog post, where david says:

> That presentation is from the Cockpit project, which isn’t part of systemd and doesn’t even share its main developers. It’s as much “remote access to systemd” as using SSH and then invoking systemctl.

and then further states in the 2nd blog post:

> I certainly don’t buy his original argument (which he hasn’t repeated in his second post) that tools like Cockpit should change the view of systemd. Just like SSH or Remote Desktop in Windows, Cockpit is the tool providing the remote, privileged access; systemd is just on the server listening locally. Blaming systemd for a Cockpit-based compromise is like blaming the “dnf” utility for removing the web server packages after someone gets root over SSH. (Cockpit is neither developed by the systemd team nor installed by default in any distributions.)

So..

> Sit back, and witness the insanity.

Who is acting insane here? A systemd developer, or people spreading FUD?

First off, this doesn't defeat my point: people are trying to connect systemd to the browser. Secondly, no, I wasn't aware it was a separate project, because it didn't initially appear to be. Ordinarily, I'd assume it was, but frankly, at this point, I can totally see Lennart doing this.

So yes, systemd isn't at fault, and I did miss it, and, to some degree, spread FUD, for which I am sorry. However, it's still a very silly idea.

No need for you to apologize - you never said systemd was at fault. (Neither did I - the point is that systemd has to be careful with its inputs, since they won't necessarily be coming from someone with root shell access.)

All init should do, arguably, is start the RC, start up the system, shut down the system, and reap zombies. Shutdown should be handled by the RC, and then passed back through to init, which does the kill and actually properly shuts down the system. As such, it should be exposed via a pipe, or other mechanism to only that trusted program. That handoff would happen during boot. Reaping zombies and startup only receive input from the kernel, or indirectly from the user in the form of processes.

If you want your init to integrate RC or process management (many do), sure, write it in a more complex language (but depend on external libraries minimally, and make sure it's statically linked!), but for the idea, minimal init, C is perfectly fine.

Systemd was started in 2010, not 2016. That would be before Go or Rust were viable options, and probably before C++ would have been a palatable alternative.

It seems you skipped the bit where I said that those restrictions are often shipped by upstream and as such applied to everyone by default? It's one thing to lock down your machine(s), systemd allows to lock down loads of services for everyone.

It's not perfect, it doesn't do everything. But is your suggestion really not to make use of systemd abilities because maybe something else could be used? How does this not go against the defence in depth theory?

Try and use (filesystem) capabilities. Now apply that security fix: capability is gone. Further, that was just a change made to your machine(s).

It seems much easier to improve the security on all fronts instead of going for some idealistic super safe solution that either takes ages or doesn't happen.

Example: pretty nice to restrict that Jabber daemon written in Java from accessing too much of the filesystem.

Well, posix capabilities can be packaged upstream do that. So can Capsicum, for that matter. And so can chroot...

If only there were a free POSIX-ish OS that did privilege separation and chroot for daemons by default. Perhaps some enterprising Canadian developer could base it on the BSD kernel.

Well then, there's your proof.

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