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SubjectRe: More file flags
On Tue, 10 Aug 1999, Simon Richter wrote:

> I thought of creating executables that contain the necessary routines
> and the secret key that are protected by a special file flag which
> does the following:
>
> - The flag can be set by any user

Fair. There are reasons why we don't allow this at the moment, though
they may be going away soon.

> - The owner may not change

chattr +i $FILE

> - The file can not be read
> - The file can be executed by the owner
> - The file can not be written to.

chmod 0100 $FILE

> - The file can be renamed by the owner, if the owner is not root.
> - The file can be deleted by the owner, if the owner is not root

# if not root
chown file_owner `dirname $FILE`
chmod og-w `dirname $FILE`

# if root
chattr +i `dirname $FILE`

> - If the flag is set while the file is open for writing, do not allow
> further opening or reading, and let the write()s proceed.

You've already stated that the flag bans writing.

The second half of that really requires a revoke(2) call.

> The last rule is meant for upgrading the software: You ask (with your
> passphrase) that the module appends the secret key to file X. It then
> opens that file in append/exclusive mode, sets the flag, then writes
> the key.

I thought these were executables?

> What do you think? Is this possible?

It's almost already done.

Matthew.


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