You can't trust macOS Privacy and Security settings
eclecticlight.co375 points by zdw 6 hours ago
375 points by zdw 6 hours ago
I think I’m probably being dumb, but the gotcha here seems to be - ‘if I give an application permission to access a folder, it has access to the files in that folder’ - which is what I would expect??
Yes, you need to read more carefully. In particular:
“8. Confirm that Documents access for Insent is still disabled in Files & Folders.
“9. Whatever you do now, the app retains full access to Documents, no matter what is shown or set in Files & Folders.”
[…]
“Access restrictions shown in Privacy & Security settings, specifically those to protected locations in Files & Folders, aren’t an accurate or trustworthy reflection of those that are actually applied. It’s possible for an app to have unrestricted access to one or more protected folders while its listing in Files & Folders shows it being blocked from access, or for it to have no entry at all in that list.”
"6. Click on Open from folder and select your Documents folder there. Confirm that works as expected and displays the name and contents of one of the text files in Documents."
It's because in step 6 the user explicitly selected the Documents folder.
The app can access the Documents folder because the user chose that directory in the native file browse dialog during the same run of the app. IMO that's a reasonable trade-off.
The problem is that this given permission doesn’t show in Files & Folders, and after turning it on and off there it still persists. The only way to revoke it is using some CLI command and restart the computer.
That's not what's happening here. Forget about the first 5 steps. If you install the app and start from step 6, the behaviour will be the same. If the user chooses the Documents folder in the browse window in an app, the app can use the contents of the Documents folder without the need for that permission in the Settings page.
The Privacy settings applies only to access to the Documents folder without the user interaction.
I think the issue here though is that the permission for access remains even after you're not using the open/save dialog and that's not obvious (or controllable from the UI) after the fact.
I think it's reasonable to expect that an application gets access to a file you access through open/save, but the fact that the access to the directory and all the items in that directory persists after that isn't necessarily expected. Especially given that the near equivalent workflow on iOS doesn't behave like this and that's what a lot of users would probably expect. On iOS an app can ask for access to your photos, which you can allow, or limit to specific photos or deny. If you allow access to specific photos and then the photo selector appears, even if you chose an album, the app will only get and retain access to the specific individual photos you gave it access to. It can not read the contents or even the names of any of the other photos in your library.
It seems pretty reasonable to expect that if the "Documents" folder permission is turned off for an app on macOS and you have given the application access to a specific document inside your documents folder, that the application would not also get (and retain) access to read from all the other folders and files within your documents folder.
I agree that this is the default behavior of most desktop OSes (including macOS), but it's also something that seems reasonable for Apple to change given how important sandboxing is to them in general, and how important it is in the broader context of always connected computers with multitudes of arbitrarily networked applications running.
Isn’t it exactly the same on iOS? If you select a folder, the app gets a security scoped URL for the folder and can read/write the entire tree. The app can also then create a bookmark to persist the security scoped url and use it whenever in the future.
> That's not what's happening here.
No, it is, the comment you're replying to is correct in what it said to you.
> The Privacy settings applies only to access to the Documents folder without the user interaction.
Yes, BUT, the user interaction is irrevocable. There are two user interactions here, one is "please access Documents this one time" and the second is "please don't let this app access Documents again."
Of course, if the stakes were higher you wouldn't even think to defend this behavior. Like if you were dealing with a nuclear weapon launcher and there was a big panel saying "TARGETING SYSTEMS: 0 targets (Permission Lock sandbox excluding 450 potential targets needing approval)" and then you poked around and found out "uh... why can I still go into the interface and target Milan and the big glowy 'launch missiles' light then starts lighting up and presumably I can launch a nuclear strike on Milan?!" and someone says, "oh yeah, that's because back when we were demoing it, the general had us punch in a random city to show what the targeting UI looked like, and we randomly chose Milan... it's okay, to fix it someone just needs to go and manually remove the warhead and put in a different one and then we'll restart the system and it'll forget all its targeting data for the old warhead" -- that'd strike you as unsustainable.
But this is very low-stakes for us so it seems less outrageous, but fundamentally it is a solid buggy behavior, "The UI makes it sound like there is only one system at play here, but there are actually two and the other system can override a specific revocation that's placed at the level the UI controls." Even if there are going to be two systems, you expect that their security controls will both be followed, or that the second one will know enough to be able to say "I say no, but I am being overruled" in its status panel.
The point is that (a) it’s misleading that the app has access to the folder while the settings claim that it doesn’t, and (b) there is no reasonable way for the user to revoke the implicitly given permission.
You don't need that permission if the user gives their implicit consent by selecting the Documents directory in the browse window. That's why most apps don't even show up in the Privacy Settings at all. Most apps don't need that, because they don't try to access that directory on their own. They only do it when the user selects the directory.
I guess the improvement can be to show the implicit consent in the privacy settings page as well, and have a way to revoke it.
Yeah, it's less of a "GOTCHA!" and more of a weird use case that Apple engineers probably didn't think through all the way. Doesn't seem like a difficult fix at all.
If the app opens a window and prompts the user to select a directory to save a file or load a file, should that access be recorded in the privacy settings page? I'd argue that maybe there should be a verbose version of the privacy settings page, where if you _really_ want to you can see every dir that every app has ever accessed, but the vast majority of users don't care.[0]
I'm less caffeinated this morning though so maybe I misread the whole argument.
[0] edit: And whether the app still has access to that dir. Which maybe that was the point of the article. I am just skeptical generally of these kinds of exposés because while they're generally pretty fair, they'll inevitably get picked up by the geniuses on r/pcmasterrace who will spin it into "Apple Privacy and Security Settings Let Terrorists Invade Your Family Photos"
I don't think any long-term implicit consent is acceptable. I would not expect that after opening one document in a folder without being shown any permission prompt, that permissions have been permanently altered. I would never even go look to see if it was "implicitly permitted".
Without a prompt or notice, I would expect only that the app has access to the file or directory I chose until the app is closed/quit.
Why should the permission even persist that long? You might leave that app running for the next two years.
Shouldn't a temporary access be temporary? Possibly scoped by time? Possibly scoped to a single access?