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Comment by pohl | Hacker News Reader

macOS had granular directory permissions way back when it was NeXTSTEP, long before SIP was introduced. Where are you suggesting they disappeared to?

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It still has them, of course, but the concern is that after ~8 years of SIP basically ~everywhere, platform security decisions have been made assuming it is present.

This concern is definitely not totally unfounded, back in 2019 Chrome shipped an update that rendered systems with SIP disabled unbootable: https://support.google.com/chrome/thread/15235262?hl=en

The "varsectomy" bug in Chrome isn't the example you think it is, because disabling SIP was not sufficient conditions for it. There were 3 other conditions that had to be met, the most notable of which is that "/" had to be writeable by tho logged-in user, which is not the default.

This is an example of defense-in-depth being present, and defense-in-depth still failing for some users who gave escalated permissions to some installers, allowing them to run roughshod over their filesystem permissions, leaving them vulnerable to a subsequent varsectomy. If one did the same thing to their Linux system, the same thing could happen.

https://arstechnica.com/information-technology/2019/09/no-it...

The two other conditions listed in the page you link basically amount to "the buggy code has to run". Related, I think SSV [1], introduced last year, would also have blocked this bug even with SIP disabled. But none of that invalidates concern that areas of the OS we don't know about might not have the level of defence in depth that we would like - it's not like Apple has never cut corners or shipped bugs to hit a date.

1: https://support.apple.com/en-gb/guide/security/secd698747c9/...

One can have vague, general concerns about any operating system if one lets their imagination run wild, though, and one doesn't care about the presence or absence of specific examples supporting the suggestion that the "permissions system...makes assumption[s]" about SIP existing.

I think we have a rather specific example of a Chrome bug hosing OS installs. Had SIP not existed, there's virtually zero chance that bug wouldn't have been caught before shipping.

Here's a better one: https://gist.github.com/ChiChou/e3a50f00853b2fbfb1debad46e50...

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