linux-kernel - Re: [PATCH v3 5/6] IMA: add hook to measure critical data from kernel components

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Date:   Mon, 31 Aug 2020 14:23:55 -0400
From:   Mimi Zohar <zohar@...ux.ibm.com>
To:     Tushar Sugandhi <tusharsu@...ux.microsoft.com>,
        stephen.smalley.work@...il.com, casey@...aufler-ca.com,
        agk@...hat.com, snitzer@...hat.com, gmazyland@...il.com
Cc:     tyhicks@...ux.microsoft.com, sashal@...nel.org, jmorris@...ei.org,
        nramas@...ux.microsoft.com, linux-integrity@...r.kernel.org,
        selinux@...r.kernel.org, linux-security-module@...r.kernel.org,
        linux-kernel@...r.kernel.org, dm-devel@...hat.com
Subject: Re: [PATCH v3 5/6] IMA: add hook to measure critical data from
 kernel components

> diff --git a/security/integrity/ima/ima_main.c b/security/integrity/ima/ima_main.c
> index 52cbbc1f7ea2..a889bf40cb7e 100644
> --- a/security/integrity/ima/ima_main.c
> +++ b/security/integrity/ima/ima_main.c
> @@ -869,6 +869,30 @@ void ima_kexec_cmdline(int kernel_fd, const void *buf, int size)
>  	fdput(f);
>  }
>  
> +/**
> + * ima_measure_critical_data - measure critical data
> + * @event_name: name for the given data
> + * @event_data_source: name of the event data source
> + * @buf: pointer to buffer containing data to measure
> + * @buf_len: length of buffer(in bytes)
> + * @measure_buf_hash: if set to true - will measure hash of the buf,
> + *                    instead of buf
> + *
> + * Buffers can only be measured, not appraised.
> + */
> +int ima_measure_critical_data(const char *event_name,
> +			      const char *event_data_source,
> +			      const void *buf, int buf_len,
> +			      bool measure_buf_hash)
> +{
> +	if (!event_name || !event_data_source || !buf || !buf_len)
> +		return -EINVAL;
> +
> +	return process_buffer_measurement(NULL, buf, buf_len, event_name,
> +					  CRITICAL_DATA, 0, event_data_source,
> +					  measure_buf_hash);

This is exactly what I'm concerned about.  Failure to measure data may
be audited, but should never fail.

Mimi

> +}