Tuf: Ensure We Do Not Inherit File Permissions For Written Key Files

[vladimir-v-diaz]

For example: https://github.com/theupdateframework/tuf/blob/develop/tuf/repository_lib.py#L806

[lukpueh]

Based on the date, above link most likely pointed to a call to TempFile's move method, which was used to persist files (here a cryptographic key) to disk, and has been replaced by securesystemslib.util. persist_temp_file (in sslib#181).

But it is hard to guess what the OP meant by "do not inherit file permissions" (maybe use a custom umask?), and if so, what umask that should be (probably a restrictive one, since it talks about keys?).

I wonder if this request is still valid, or if this is just not in the scope of TUF.

cc @mnm678, @trishankatdatadog, @JustinCappos

[mnm678]

As the method in question has been replaced, I think we can close this issue, and reopen if it becomes an issue with the persist_temp_file method.

[trishankatdatadog]

I guess he meant private keys should be written with umask 600, like how OpenSSH restricts the reading and writing of private keys to the user.

[lukpueh]

@trishankatdatadog, do you think it's worth keeping this (now clarified) feature request around? If so I can re-open it on the securesystemslib repo.

[trishankatdatadog]

Yes, I think so, please

[lukpueh]

Will be fixed in secure-systems-lab/securesystemslib#222