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

[Tushar Sugandhi]

On 2020-08-31 11:23 a.m., Mimi Zohar wrote:
> > 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
As I responded in patch 2, I can ignore the result of 
process_buffer_measurement() in ima_measure_critical_data(), and make
ima_measure_critical_data() return type as "void".

But that’s the only place where the results of p_b_m() are being used.
So I might as well just revert the return type of p_b_m() to the
original "void".

> > +}