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Comment by cesarb | Hacker News Reader

The first section, on security fixes ("[...] you only need to update a shared library to apply security fixes to all executables that rely on that library"), starts talking about security fixes but then suddenly switches to talking about ABI and API breaks. But that sleight-of-hand hides the fact that many (perhaps even most) security fixes do not break the ABI or API; they are completely contained to the implementation (one obvious exception would be if the security issue was caused by bad API design, but even then often there are ways to fix it without breaking the ABI).

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> But that sleight-of-hand hides the fact that many (perhaps even most) security fixes do not break the ABI or API; they are completely contained to the implementation (one obvious exception would be if the security issue was caused by bad API design, but even then often there are ways to fix it without breaking the ABI).

Right you are. I was also perplexed when I read that non sequitur. The author's reference to DLL Hell also suggests there's some confusion in his analysis of the underlying problem, given that DLL Hell is very specific to windows and at best is only orthogonally related to ABI. The author's references to API changes make even less sense, and definitely cast doubt over his insight into the issue.

And was kind of fixed with application manifests, on XP.

Differentiating DLL and SO hell is getting a bit beyond pedantic as they are implementations of the same fundamental abstraction. Any substantial difference in merely one of implementation details.

> Differentiating DLL and SO hell is getting a bit beyond pedantic (...)

It really isn't. Unlike linking problems, where the problem is focused on how you need to fight your dependencies to be able to resolve symbols, DLL Hell has been for over a decade a dependency resolution problem that is solved at the packaging level.

More importantly, on Windows, where sharing DLLs is not a thing, you can simply drop a DLL in the app dir and be done with it. In fact, it's customary for windows apps to just bundle all their dependencies.

Author here.

Sure, most security fixes do not break the ABI or API. But it only takes one, and then you have a security issue.

So I can understand your sentiment that it was sleight-of-hand, but I argue that it's not.

Also, we only think that most security updates don't break API or ABI because we have no automatic way of checking. It's all thoughts and prayers. I'm a religious person, but thoughts and prayers are not a good way to do computer security.

If a security fix must break the API, you can bump up the SONAME which forces all packages depending on your shared library to recompile against the new version. This is comparable to the requirements under static linking, but you only have to do it when absolutely needed.

> Sure, most security fixes do not break the ABI or API. But it only takes one, and then you have a security issue.

As someone who has been a Unix sysadmin for almost twenty years now, I don't recall every installing a patch or package update that broke the ABI/API.

If one should happen to occur next week, I'll still go with leaning towards linked libraries, as their convenience out-weights (has out-weighted) the once-in-twenty-years occurrence of breakage.

> It's all thoughts and prayers. I'm a religious person, but thoughts and prayers are not a good way to do computer security.

Ditto. But "faith" and "trust" are (almost) synonyms. And I trust the updaters of libraries to be able to get out a security update in short order more than I trust the possibility of all the package maintainers that link to it to be able to coördinate a quick update.

When OpenSSL's Heartbleed occurred it was one package update and restarting of a bunch of processes (helped by the checkrestart utility in the debian-goodies package). That's a lot quicker than updating a bazillion dependents.

Not related to the OP but I’ve had many issues with non standard vendors placing breaking changes in their patch/minor releases. You think you’re updating to a relatively normal version and it actually breaks your entire production.

I’m looking at you, MySQL, docker, Mongodb, or harbor.

I’m not complaining, those are provided free of charge and we are happy when it works, but semver is really all that matters in this: either you adhere and it’s smooth sailing, or you don’t and then please don’t use semver-looking numbering.

There's a difference between vendor provided packages and distro provided packages. Distros pay a lot more attention to breaking changes.

I understand where you are coming from. That's actually why I gave my ideas to get the best from both types of linking.

I've (probably?) found more linker vulnerabilities than anyone else, but don't really understand your argument. I definitely understand library search path vulnerabilities (I've literally found bugs in $ORIGIN parsing, e.g. CVE-2010-3847 was one of mine!).

We think security updates don't break API/ABI because they're backported to all previous major versions that are still actively supported. This isn't "thoughts and prayers", it's work that the packagers and maintainers do. I can't tell you how useful being able to fix a vulnerability in every program is, just think of updating every application that uses libpng on your desktop, or every server application that uses OpenSSL.

I just can't imagine wanting to give that up, because of name mangling ABI issues!

I hope that puts it to rest; I can hope. Unfortunately, my experience is that people who haven't fixed multiple security problems, and probably have never heard of taviso, know a lot more about security than people who have...

I have heard of taviso. That doesn't mean I can't disagree with him.

Sorry, I was talking generally. I try to avoid being personal in posts.

That's why you run a trusted Linux distro in production, like sles or rhel or ubuntu, their core value proposition is _exactly_ this: Provide binary compatible drop in replacement security updates for shared objects over the lifetime of the platform. They even maintain kernel internal abi compatibility for the released and maintained product, so your exotic-hardware.ko module doesn't need to be updated.

Also there is mature tooling around ABI compliance checking: https://lvc.github.io/abi-compliance-checker/

This is used to document the ABI stability of mature projects like so: https://abi-laboratory.pro/index.php?view=tracker

E: re thoughts and prayers, the mature Linux distro all run extensive revalidation for their security updates. Breaking customer binary applications with a security update is the absolute worst case scenario. For yocto or similar cost free projects, or Linux distros that are source, not binary, that may be a different story. But for sles, rhel, ubuntu it's not thoughts and prayers but a maintenance verification and release process on their side and a monthly bill on yours.

> we have no automatic way of checking

I do for Fedora packages I maintain. There can be false positives, like on symbols that shouldn't be exported, but you can look at the API to start with. (The library author should do that, of course.)

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