Messages in this thread | | | Subject | Re: [PATCH v5 6/7] IMA: add critical_data to the built-in policy rules | From | Lakshmi Ramasubramanian <> | Date | Fri, 6 Nov 2020 07:37:16 -0800 |
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On 11/6/20 7:24 AM, Mimi Zohar wrote:
Hi Mimi,
Thanks for reviewing the patches.
> Hi Lakshmi, Tushar, > > This patch defines a new critical_data builtin policy. Please update > the Subject line. > > On Sun, 2020-11-01 at 14:26 -0800, Tushar Sugandhi wrote: >> From: Lakshmi Ramasubramanian <nramas@linux.microsoft.com> >> >> The IMA hook to measure kernel critical data, namely >> ima_measure_critical_data(), could be called before a custom IMA policy >> is loaded. For example, SELinux calls ima_measure_critical_data() to >> measure its state and policy when they are initialized. This occurs >> before a custom IMA policy is loaded, and hence IMA hook will not >> measure the data. A built-in policy is therefore needed to measure >> critical data provided by callers before a custom IMA policy is loaded. > > ^Define a new critical data builtin policy to allow measuring early > kernel integrity critical data before a custom IMA policy is loaded.
I will add the above line in the patch description.
> > Either remove the references to SELinux or move this patch after the > subsequent patch which measures SELinux critical data.
I will remove the reference to SELinux. I think it would be better to have this patch before the SELinux measurement patch.
> >> >> Add CRITICAL_DATA to built-in IMA rules if the kernel command line >> contains "ima_policy=critical_data". Set the IMA template for this rule >> to "ima-buf" since ima_measure_critical_data() measures a buffer. >> >> Signed-off-by: Lakshmi Ramasubramanian <nramas@linux.microsoft.com> > >> --- >> security/integrity/ima/ima_policy.c | 32 +++++++++++++++++++++++++++++ >> 1 file changed, 32 insertions(+) >> >> diff --git a/security/integrity/ima/ima_policy.c b/security/integrity/ima/ima_policy.c >> index ec99e0bb6c6f..dc8fe969d3fe 100644 >> --- a/security/integrity/ima/ima_policy.c >> +++ b/security/integrity/ima/ima_policy.c > >> @@ -875,6 +884,29 @@ void __init ima_init_policy(void) >> ARRAY_SIZE(default_appraise_rules), >> IMA_DEFAULT_POLICY); >> >> + if (ima_use_critical_data) { >> + template = lookup_template_desc("ima-buf"); >> + if (!template) { >> + ret = -EINVAL; >> + goto out; >> + } >> + >> + ret = template_desc_init_fields(template->fmt, >> + &(template->fields), >> + &(template->num_fields)); > > The default IMA template when measuring buffer data is "ima_buf". Is > there a reason for allocating and initializing it here and not > deferring it until process_buffer_measurement()? >
You are right - good catch. I will remove the above and validate.
thanks, -lakshmi
> >> + if (ret) >> + goto out; >> + >> + critical_data_rules[0].template = template; >> + add_rules(critical_data_rules, >> + ARRAY_SIZE(critical_data_rules), >> + IMA_DEFAULT_POLICY); >> + } >> + >> +out: >> + if (ret) >> + pr_err("%s failed, result: %d\n", __func__, ret); >> + >> ima_update_policy_flag(); >> } >> >
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