linux-kernel - Re: [PATCH v6 2/3] add a new ima template field buf

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Date:   Fri, 24 May 2019 11:12:02 -0400
From:   Mimi Zohar <zohar@...ux.ibm.com>
To:     Prakhar Srivastava <prsriva02@...il.com>,
        linux-integrity@...r.kernel.org,
        linux-security-module@...r.kernel.org, linux-kernel@...r.kernel.org
Cc:     mjg59@...gle.com, roberto.sassu@...wei.com, vgoyal@...hat.com
Subject: Re: [PATCH v6 2/3] add a new ima template field buf

On Mon, 2019-05-20 at 17:06 -0700, Prakhar Srivastava wrote:
> A buffer(cmdline args) measured into ima cannot be appraised
> without already being aware of the buffer contents.Since we
> don't know what cmdline args will be passed (or need to validate
> what was passed) it is not possible to appraise it. 
> 
> Since hashs are non reversible the raw buffer is needed to 
> recompute the hash.
> To regenrate the hash of the buffer and appraise the same
> the contents of the buffer need to be available.
> 
> A new template field buf is added to the existing ima template
> fields, which can be used to store/read the buffer itself.
> Two new fields are added to the ima_event_data to carry the
> buf and buf_len whenever necessary.
> 
> Updated the process_buffer_measurement call to add the buf
> to the ima_event_data.
> process_buffer_measurement added in "Add a new ima hook 
> ima_kexec_cmdline to measure cmdline args"
> 
> - Add a new template field 'buf' to be used to store/read
> the buffer data.
> - Added two new fields to ima_event_data to hold the buf and
> buf_len [Suggested by Roberto]
> -Updated process_buffer_meaurement to add the buffer to
> ima_event_data

This patch description can be written more concisely.

Patch 1/3 in this series introduces measuring the kexec boot command
line.  This patch defines a new template field for storing the kexec
boot command line in the measurement list in order for a remote
attestation server to verify.

As mentioned, the first patch description should include a shell
command for verifying the digest in the kexec boot command line
measurement list record against /proc/cmdline.  This patch description
should include a shell command showing how to verify the digest based
on the new field.  Should the new field in the ascii measurement list
be displayed as a string, not hex?

Mimi