Re: [PATCH 2/3 v5] add a new template field buf to contain the buffer

From: prakhar srivastava <prsriva02@gmail.com>
To: Roberto Sassu <roberto.sassu@huawei.com>
Cc: linux-integrity@vger.kernel.org,
	inux-security-module@vger.kernel.org,
	linux-kernel@vger.kernel.org, Mimi Zohar <zohar@linux.ibm.com>,
	ebiederm@xmission.com, vgoyal@redhat.com,
	Prakhar Srivastava <prsriva@microsoft.com>
Subject: Re: [PATCH 2/3 v5] add a new template field buf to contain the buffer
Date: Mon, 13 May 2019 22:07:08 -0700	[thread overview]
Message-ID: <CAEFn8qJVvNivP6Lmx+nVewPcHjH=V2OrR_HyHR6nOeuVQW0A4w@mail.gmail.com> (raw)
In-Reply-To: <45344b2f-d9ea-f7df-e45f-18037e2ba5ca@huawei.com>

On Mon, May 13, 2019 at 6:48 AM Roberto Sassu <roberto.sassu@huawei.com> wrote:
>
> On 5/11/2019 12:37 AM, Prakhar Srivastava wrote:
> > From: Prakhar Srivastava <prsriva02@gmail.com>
> >
> > The buffer(cmdline args) added to the ima log cannot be attested
> > without having the actual buffer. Thus to make the measured buffer
> > available to store/read a new ima template (buf) is added.
>
> Hi Prakhar
>
> please fix the typos. More comments below.
>
>
> > +     buffer_event_data->type = IMA_XATTR_BUFFER;
> > +     buffer_event_data->buf_length = size;
> > +     memcpy(buffer_event_data->buf, buf, size);
> > +
> > +     event_data.xattr_value = (struct evm_ima_xattr_data *)buffer_event_data;
> > +     event_data.xattr_len = alloc_length;
>
> I would prefer that you introduce two new fields in the ima_event_data
> structure. You can initialize them directly with the parameters of
> process_buffer_measurement().
I will make the edits, this will definitely save the kzalloc in this code
path.
>
> ima_write_template_field_data() will make
> a copy.
>
Since event_data->type is used to distinguish what the template field
 should contain.
Removing the type and subsequent check in the template_init,
 buf template fmt will result in the whole event_Data structure
being added to the log, which is not the expected output.
For buffer entries, the buf templet fmt will contains the buffer itself.

>
> > +      .field_show = ima_show_template_buf},
>
> Please update Documentation/security/IMA-templates.rst
Will update the documentation.

Thanks,
Prakhar Srivastava
>
> Thanks
>
> Roberto