linux-kernel - Re: [PATCH v1.3 4/4] keys: add new key-type encrypted

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Date:	Mon, 15 Nov 2010 16:18:54 +0000
From:	David Howells <dhowells@...hat.com>
To:	Mimi Zohar <zohar@...ux.vnet.ibm.com>
Cc:	dhowells@...hat.com, linux-kernel@...r.kernel.org,
	linux-security-module@...r.kernel.org, keyrings@...ux-nfs.org,
	linux-crypto@...r.kernel.org,
	Jason Gunthorpe <jgunthorpe@...idianresearch.com>,
	James Morris <jmorris@...ei.org>,
	David Safford <safford@...son.ibm.com>,
	Rajiv Andrade <srajiv@...ux.vnet.ibm.com>,
	Mimi Zohar <zohar@...ibm.com>
Subject: Re: [PATCH v1.3 4/4] keys: add new key-type encrypted

Mimi Zohar <zohar@...ux.vnet.ibm.com> wrote:

> > I thought that might be the case.  In which case, it might be better to
> > allow someone to add a trusted key, supplying both encrypted and
> > unencrypted versions of the data so that the TPM need not be consulted.
> > You might want to mark such a key so that it can be seen when it is
> > dumped.
> 
> At least to me, the name 'trusted' implies some form of HW. 

In many ways, I think that the type and description describe the purpose of
the key, not its source or derivation.

> > But if you're going to use a user-defined key, you really need to prefix
> > the description with something suitable.
> 
> Agreed. So instead of: 
> 	keyctl add encrypted name "new master-key-name keylen" ring
> 
> the description would be prefixed with the key type like:	
> 	keyctl add encrypted name "new trusted|user master-key-name keylen" ring

I don't think you understood what I meant.  If you look at the following
function:

+static struct key *request_master_key(struct encrypted_key_payload *epayload,
+	       	   			void **master_key,
+					unsigned int *master_keylen)
+{
+	struct key *mkey;
+
+	mkey = request_trusted_key(epayload->master_desc,
+				   master_key, master_keylen);
+	if (IS_ERR(mkey)) {
+		mkey = request_user_key(epayload->master_desc,
+					master_key, master_keylen);
+		if (IS_ERR(mkey)) {
+			pr_info("encrypted_key: trusted/user key %s not found",
+				epayload->master_desc);
+			return mkey;
+		}
+	}
+	dump_master_key(*master_key, *master_keylen);
+	return mkey;
+}

In the bit where you go for a user key (having failed to get a trusted key),
you should prefix the description here (or in request_user_key()) with
something like "trusted:".  Then you don't need to change the user interface.

David
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