Messages in this thread | | | Subject | Re: Ответ: VFS, NFS security bug? Should CAP_MKNOD and CAP_LINUX_IMMUTABLE be added to CAP_FS_MASK? | From | Stephen Smalley <> | Date | Wed, 18 Mar 2009 12:21:27 -0400 |
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On Tue, 2009-03-17 at 13:23 -0500, Serge E. Hallyn wrote: > But in cap_inode_setxattr, any security.* xattrs are controlled by > CAP_SYS_ADMIN. So do you think that this should be changed to a > CAP_XATTR_SECURITY capability which can be added to CAP_FS_MASK?
I think that would be preferable to CAP_SYS_ADMIN, yes.
> Or do you think it's ok that fsuid=0 does not allow you to set > security.selinux (or security.SMACK64, etc) xattrs when selinux is > not compiled in?
Just to be clear, at present fsuid is irrelevant to setting the security.* xattrs since it doesn't affect the CAP_SYS_ADMIN capability at all, so it all depends on the initial capability state prior to using setfsuid(), typically the full capability set.
> (You may have already answered this with your EOPNOTSUPP comment, but > I want to make sure I understand right) > > > > Does anyone know what the trusted xattrs are used for? > > > > Not beyond what attr(5) says about them. > > Well, if attr(5) says CAP_SYS_ADMIN being needed is the very > thing that defines these xattrs, then changing that seems a > bigger deal. That really does seem akin to changing kernel-user > API.
Perhaps, although it isn't clear that this API is in use by anyone or in use in a way that would actually distinguish based on individual capability.
But if you were to add CAP_SYS_ADMIN to CAP_FS_MASK in order to ensure that setfsuid() does in fact affect all filesystem accesses, how much meaningful difference remains between fsuid==0 and euid==0? It obviously takes you far afield of only affecting filesystem accesses.
-- Stephen Smalley National Security Agency
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