On Wed, 2003-10-15 at 14:31, Thorsten Kukuk wrote:
> Ok, since I copy always all attributes if I modify /etc/passwd and
> /etc/shadow (to make sure to preserve ACLs and security attributes),
> I don't need it.

The problem with simply preserving attributes via setxattr is that you cannot create the new file immediately with the desired attributes, so there is a window where the new file exists with the default attribute value, typically inherited from the parent directory. Note that this is particularly a concern for /etc/passwd and /etc/shadow, since they live in the same parent directory but have differing protection requirements.

The SELinux setfscreatecon() interface (implemented via the /proc/pid/attr/fscreate API) allows a process to set the desired security context for subsequent file creations, similar to the umask. You'll notice that many of the SELinux patches use this interface to set the desired context prior to creating the new file, so that files are immediately created with the right context and are protected accordingly. This is one of the reasons we don't just use the EA patch for coreutils and instead have our own.

-- 
Stephen Smalley <sds@epoch.ncsc.mil>
National Security Agency


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