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An answer to the question "Allowing a regular user to listen to a port below 1024", specified giving an executable additional permissions using setcap such that the program could bind to ports smaller than 1024:

setcap 'cap_net_bind_service=+ep' /path/to/program

What is the correct way to undo these permissions?

2 Answers 2

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To remove capabilities from a file use the -r flag

setcap -r /path/to/program

This will result in the program having no capabilities.

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  • Well, that was a lot more evident after re-reading that short man page >.> Aug 15, 2016 at 2:07
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    How can I confirm that the setcap -r command worked as intended? Jan 28, 2022 at 13:39
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    @dotnetCarpenter Use getcap Jan 31, 2022 at 18:00
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What @stephen-harris posted is right. But it removes all capabilities added to the program in one shot. To remove a specific capability, this should work (following the example in the question):

setcap 'cap_net_bind_service=-ep' /path/to/program

Notice the '-' sign. You can verify the capabilities of an executable as follows:

getcap /path/to/program

In case of setcap -r, all capabilities will be gone and the result of getcap will be empty where as the '-ep' just removes what you added with '+ep'.

This comes in handy when you gave multiple capabilities and want to selectively remove them.

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