From: Mimi Zohar Date: Thu, 07 Nov 2019 20:53:08 +0000 Subject: Re: [PATCH v4 01/10] IMA: Defined an IMA hook to measure keys on key create or update Message-Id: <1573159988.5028.400.camel@linux.ibm.com> MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 8bit List-Id: References: <20191106190116.2578-1-nramas@linux.microsoft.com> <20191106190116.2578-2-nramas@linux.microsoft.com> <1573080189.5028.313.camel@linux.ibm.com> <1573098037.5028.325.camel@linux.ibm.com> <7ce84aa0-729e-c58e-f16a-25490b4e336d@linux.microsoft.com> In-Reply-To: <7ce84aa0-729e-c58e-f16a-25490b4e336d@linux.microsoft.com> To: Lakshmi Ramasubramanian , dhowells@redhat.com, matthewgarrett@google.com, sashal@kernel.org, jamorris@linux.microsoft.com, linux-integrity@vger.kernel.org, linux-security-module@vger.kernel.org, keyrings@vger.kernel.org, linux-kernel@vger.kernel.org On Thu, 2019-11-07 at 10:42 -0800, Lakshmi Ramasubramanian wrote: > On 11/6/2019 7:40 PM, Mimi Zohar wrote: > > >>> I would move the patch that defines the "keyring=" policy option prior > >>> to this one.  Include the call to process_buffer_measurement() in this > >>> patch.  A subsequent patch would add support to defer measuring the > >>> key, by calling a function named something like > >>> ima_queue_key_measurement(). > >>> > >> > >> As I'd stated in the other response, I wanted to isolate all key related > >> code in a separate C file and build it if and only if all CONFIG > >> dependencies are met. > > > > The basic measuring of keys shouldn't be any different than any other > > policy rule, other than it is a key and not a file.  This is the > > reason that I keep saying start out with the basics and then add > > support to defer measuring keys on the trusted keyrings. > > I'll make the changes, rearrange the patches and send an updated set. > > I do have a few questions since I am still not fully understanding the > requirements you are targeting. Appreciate if you could please clarify. > > As you already know, I am using the "public key" of the given asymmetric > key as the "buffer" to measure in process_buffer_measurement(). > > The measurement decision is not based on whether the keyring is a > trusted one or an untrusted one. As long as the IMA policy allows > (through the "keyrings=" option) the key will be measured. We should be able to measure all keys being loaded onto any keyring or onto a specific "keyring=".   This shouldn't be any different than any other policy rule.  Once you have this basic feature working, you would address loading keys during early boot. > > Do you want only trusted keyrings to be allowed in the measurement? > In my opinion, that decision should be deferred to whoever is setting up > the IMA policy. Right, but it shouldn't be limited to just "trusted" keyrings.  This way you can first test loading keys onto any keyring. > > > Only the queueing code needed for measuring keys on the trusted > > keyrings would be in a separate file. > > > > The decision to process key immediately or defer (queue) is based on > whether IMA has been initialized or not. Keyring is not used for this > decision. > > Could you please clarify how queuing is related to keyring's > trustworthiness? > > The check for whether the key is an asymmetric one or not, and > extracting the "public key" if it is an asymmetric key needs to be in a > separate file to handle the CONFIG dependencies in IMA. Queuing the keys should be independent of measuring the keys.  Initially you would start with just measuring the key.  From a high level it would look like: ima_post_key_create_or_update(...) {    "measure key based on policy(key, keyring, ...)" } This requires the IMA "keyring=" policy option support be defined first. Subsequently you would add key queuing support, and then update ima_post_key_create_or_update().  It would look like: ima_post_key_create_or_update(...) { if (custom policy is loaded)    "measure key based on policy(key, keyring, ...)" else "queue key(key, keyring)" } Mimi