From: David Howells <dhowells@redhat.com>
To: Casey Schaufler <casey@schaufler-ca.com>
Cc: dhowells@redhat.com, linux-unionfs@vger.kernel.org,
selinux@tycho.nsa.gov, linux-fsdevel@vger.kernel.org,
linux-security-module@vger.kernel.org,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH 1/7] Security: Provide copy-up security hooks for unioned files
Date: Fri, 07 Nov 2014 14:49:14 +0000 [thread overview]
Message-ID: <29644.1415371754@warthog.procyon.org.uk> (raw)
In-Reply-To: <545BB3DD.1010607@schaufler-ca.com>
Casey Schaufler <casey@schaufler-ca.com> wrote:
> > + * @inode_copy_up:
> > + * Generate the secid associated with the destination inode when a unioned
>
> NAK.
>
> You can't just deal with the access label, nor can you assume that there
> is exactly one. Don't use secids. ...
Okay, I've changed the documentation to:
* @inode_copy_up:
* Appropriately label the destination inode when a unioned file is copied
* up from a lower layer to the union/overlay layer.
* @src indicates the file that is being copied up.
* @dst indicates the file that has being created by the copy up.
* Returns 0 on success or a negative error code on error.
> > + * @inode_copy_up_xattr:
> > + * Filter/modify the xattrs being copied up when a unioned file is copied
> > + * up from a lower layer to the union/overlay layer.
> > + * @src indicates the file that is being copied up.
> > + * @dst indicates the file that has being created by the copy up.
> > + * @name indicates the name of the xattr.
> > + * @value, *@size indicate the payload of the xattr.
> > + * Returns 0 to accept the xattr, 1 to discard the xattr or a negative
> > + * error code to abort the copy up. The xattr buffer must be at least
> > + * XATTR_SIZE_MAX in capacity and the contents may be modified and *@size
> > + * changed appropriately.
>
> Who is going to call this?
Anyone that copies up a file from the lower layer in a union to an upper
layer. Overlayfs for example. Unionmount for another.
> How are is the caller going to know all the xattr names that matter?
The caller has no idea. That's why it presents them all here.
> > +static int cap_inode_copy_up_xattr(struct dentry *src, struct dentry *dst,
> > + const char *name, void *value, size_t *size)
> > +{
> > + return 0;
> > +}
> > +
>
> Does this mean that without LSM help no xattrs ever get copied?
No. This is merely a filter. The caller reads the xattr, presents them to
this hook and then, if not asked to discard, writes the xattr. I've added a
bit to the end of the comment to this effect.
David
WARNING: multiple messages have this Message-ID (diff)
From: David Howells <dhowells@redhat.com>
To: Casey Schaufler <casey@schaufler-ca.com>
Cc: linux-unionfs@vger.kernel.org, linux-kernel@vger.kernel.org,
dhowells@redhat.com, linux-security-module@vger.kernel.org,
selinux@tycho.nsa.gov, linux-fsdevel@vger.kernel.org
Subject: Re: [PATCH 1/7] Security: Provide copy-up security hooks for unioned files
Date: Fri, 07 Nov 2014 14:49:14 +0000 [thread overview]
Message-ID: <29644.1415371754@warthog.procyon.org.uk> (raw)
In-Reply-To: <545BB3DD.1010607@schaufler-ca.com>
Casey Schaufler <casey@schaufler-ca.com> wrote:
> > + * @inode_copy_up:
> > + * Generate the secid associated with the destination inode when a unioned
>
> NAK.
>
> You can't just deal with the access label, nor can you assume that there
> is exactly one. Don't use secids. ...
Okay, I've changed the documentation to:
* @inode_copy_up:
* Appropriately label the destination inode when a unioned file is copied
* up from a lower layer to the union/overlay layer.
* @src indicates the file that is being copied up.
* @dst indicates the file that has being created by the copy up.
* Returns 0 on success or a negative error code on error.
> > + * @inode_copy_up_xattr:
> > + * Filter/modify the xattrs being copied up when a unioned file is copied
> > + * up from a lower layer to the union/overlay layer.
> > + * @src indicates the file that is being copied up.
> > + * @dst indicates the file that has being created by the copy up.
> > + * @name indicates the name of the xattr.
> > + * @value, *@size indicate the payload of the xattr.
> > + * Returns 0 to accept the xattr, 1 to discard the xattr or a negative
> > + * error code to abort the copy up. The xattr buffer must be at least
> > + * XATTR_SIZE_MAX in capacity and the contents may be modified and *@size
> > + * changed appropriately.
>
> Who is going to call this?
Anyone that copies up a file from the lower layer in a union to an upper
layer. Overlayfs for example. Unionmount for another.
> How are is the caller going to know all the xattr names that matter?
The caller has no idea. That's why it presents them all here.
> > +static int cap_inode_copy_up_xattr(struct dentry *src, struct dentry *dst,
> > + const char *name, void *value, size_t *size)
> > +{
> > + return 0;
> > +}
> > +
>
> Does this mean that without LSM help no xattrs ever get copied?
No. This is merely a filter. The caller reads the xattr, presents them to
this hook and then, if not asked to discard, writes the xattr. I've added a
bit to the end of the comment to this effect.
David
next prev parent reply other threads:[~2014-11-07 14:49 UTC|newest]
Thread overview: 89+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-11-05 15:42 [PATCH 0/7] Security: Provide unioned file support David Howells
2014-11-05 15:42 ` [PATCH 1/7] Security: Provide copy-up security hooks for unioned files David Howells
2014-11-06 17:46 ` Casey Schaufler
2014-11-07 14:49 ` David Howells [this message]
2014-11-07 14:49 ` David Howells
2014-11-07 21:22 ` Paul Moore
2014-11-07 21:22 ` Paul Moore
2014-11-07 22:10 ` David Howells
2014-11-07 22:10 ` David Howells
2014-11-10 15:28 ` Paul Moore
2014-11-10 15:28 ` Paul Moore
2014-11-05 15:42 ` [PATCH 2/7] Overlayfs: Use copy-up security hooks David Howells
2014-11-07 21:39 ` Paul Moore
2014-11-07 21:39 ` Paul Moore
2014-11-07 22:05 ` David Howells
2014-11-07 22:05 ` David Howells
2014-11-10 15:45 ` Paul Moore
2014-11-10 15:45 ` Paul Moore
2014-11-05 15:42 ` [PATCH 3/7] SELinux: Stub in copy-up handling David Howells
2014-11-07 21:44 ` Paul Moore
2014-11-07 21:44 ` Paul Moore
2014-11-07 22:08 ` David Howells
2014-11-07 22:08 ` David Howells
2014-11-10 15:47 ` Paul Moore
2014-11-10 15:47 ` Paul Moore
2014-11-05 15:42 ` [PATCH 4/7] Security: Pass the union-layer file path into security_file_open() David Howells
2014-11-05 15:43 ` [PATCH 5/7] SELinux: Handle opening of a unioned file David Howells
2014-11-05 16:35 ` Stephen Smalley
2014-11-06 12:03 ` David Howells
2014-11-06 12:03 ` David Howells
2014-11-06 13:13 ` Stephen Smalley
2014-11-06 13:13 ` Stephen Smalley
2014-11-06 13:34 ` David Howells
2014-11-06 13:34 ` David Howells
2014-11-27 14:15 ` David Howells
2014-11-27 14:15 ` David Howells
2014-11-06 12:27 ` David Howells
2014-11-06 12:27 ` David Howells
2014-11-06 12:27 ` David Howells
2014-11-27 17:25 ` David Howells
2014-11-27 17:25 ` David Howells
2015-06-12 15:30 ` David Howells
2015-06-12 15:30 ` David Howells
2015-06-15 12:57 ` Stephen Smalley
2015-06-15 12:57 ` Stephen Smalley
2015-06-16 9:41 ` David Howells
2015-06-16 9:41 ` David Howells
2015-06-16 16:49 ` David Howells
2015-06-16 16:49 ` David Howells
2015-06-16 17:20 ` Stephen Smalley
2015-06-16 17:20 ` Stephen Smalley
2015-06-16 21:34 ` David Howells
2015-06-16 21:34 ` David Howells
2015-06-17 14:44 ` Stephen Smalley
2015-06-17 14:44 ` Stephen Smalley
2015-06-18 10:15 ` David Howells
2015-06-18 10:15 ` David Howells
2015-06-18 12:48 ` Stephen Smalley
2015-06-18 12:48 ` Stephen Smalley
2015-06-18 15:26 ` David Howells
2015-06-18 15:26 ` David Howells
2015-06-18 10:32 ` David Howells
2015-06-18 10:32 ` David Howells
2015-06-18 12:16 ` Stephen Smalley
2015-06-18 12:16 ` Stephen Smalley
2014-11-05 15:43 ` [PATCH 6/7] SELinux: The copy-up operation must have read permission on the lower file David Howells
2014-11-05 16:43 ` Stephen Smalley
2014-11-05 17:54 ` Stephen Smalley
2014-11-06 13:39 ` Stephen Smalley
2014-11-27 14:17 ` David Howells
2014-11-27 14:17 ` David Howells
2014-11-27 14:21 ` David Howells
2014-11-27 14:21 ` David Howells
2014-11-27 14:21 ` David Howells
2014-11-05 15:43 ` [PATCH 7/7] SELinux: Check against union and lower labels for file ops on lower files David Howells
2014-11-06 17:35 ` [PATCH 0/7] Security: Provide unioned file support Casey Schaufler
2014-11-06 17:35 ` Casey Schaufler
2014-11-06 17:58 ` David Howells
2014-11-06 17:58 ` David Howells
2014-11-06 18:40 ` Casey Schaufler
2014-11-06 18:40 ` Casey Schaufler
2014-11-07 15:21 ` David Howells
2014-11-07 15:21 ` David Howells
2014-11-07 18:54 ` Daniel J Walsh
2014-11-07 18:54 ` Daniel J Walsh
2014-11-09 1:31 ` Casey Schaufler
2014-11-09 1:31 ` Casey Schaufler
2014-11-10 13:59 ` Daniel J Walsh
2014-11-10 13:59 ` Daniel J Walsh
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