[EXTERNAL] Re: Weird issue with file permissions

[Andrey Repin]

Greetings, Lavrentiev, Anton (NIH/NLM/NCBI) [C]!

>> what your test program was actually doing.  But you seem to be assuming that
>> calling fchmod on a socket descriptor should affect the permissions on the
>> socket file (assuming the socket is bound).  Is that documented anywhere?  POSIX
>> says that the behavior of fchmod on a socket descriptor is unspecified

> The socket file descriptor for a bound UNIX sockets refers to an object in a filesystem
> (it's practically a file), which the bind() system call creates.  The access to the socket
> is controlled by the permission bits, when someone actually tries to connect to it,

Which is not necessarily related to the permissions on the file. Windows
socket is an in-memory object, the file is used merely for naming purposes.

> so permissions should be working for these objects (otherwise, there's no other way!)

Does the not? Can you connect to a socket with user that should not have
permissions after you have changed them?

> And fchmod() for a bound Unix socket works on Linux and many other Unix flavors, actually.

"Works", all right. But HOW does it works? Aren't the permissions seen on the
socket file merely a coincidence/convenience?


-- 
With best regards,
Andrey Repin
Sunday, July 3, 2022 00:57:58

Sorry for my terrible english...