Hi Prakhar,
On Mon, 2019-05-20 at 17:06 -0700, Prakhar Srivastava wrote:
> Currently during kexec_file_load(soft reboot) the cmdline args
> passed are not measured and the PCR values are not reset.
This patch addresses not measuring the kexec boot cmdline. I don't
see a reason for mentioning anything about the PCR values not being
reset. Keep it simple.
> This results in the new kernel to assume a secure boot was
> followed. The boot args used to launch the new kernel need to be
> measured and carried over to the next kernel to be used for
> attestation. IMA supports only measuring files, no functionality
> exists to measure a buffer(kexec cmdline).
>
> This change adds a new functionality to measure buffers
> process_buffer_measurement which uses the hash of the buffer
> instead of file hash to add an entry in the ima log.
> A new ima hook ima_kexec_cmdline is also defined which calls
> into process_buffer_measurement to add the kexec_cmdline args
> to the log.
>
> A new policy KEXEC_CMDLINE is also defined to control measuring the
> kexec_cmdline buffer.
> This patch only adds IMA_MEASURE as a supported functionality.
>
> - A new ima hook ima_kexec_cmdline is defined to be called by the
> kexec code.
> - A new function process_buffer_measurement is defined to measure
> the buffer hash into the ima log.
> - A new func policy KEXEC_CMDLINE is defined to control the measurement.
Missing is how to verify the digest of the measurement list kexec boot
cmdline entry based on /proc/cmdline. Everything before the "root="
in the /proc entry needs to be removed before calculating the hash.
Please include a sample shell command.
Matthew's patch "IMA: Allow profiles to define the desired IMA
template" will require changes to this patch. Please rebase this
patch set on top of it, once Matthew addresses the comments and re-
posts.
(Reminder: the patch description should be 70 - 75 characters.)
>
> Signed-off-by: Prakhar Srivastava <prsriva02@xxxxxxxxx>
> ---
< snip >
> --- a/security/integrity/ima/ima_main.c
> +++ b/security/integrity/ima/ima_main.c
> @@ -576,6 +576,83 @@ int ima_load_data(enum kernel_load_data_id id)
> return 0;
> }
>
> +/*
> + * process_buffer_measurement - Measure the buffer to ima log.
> + * @buf: pointer to the buffer that needs to be added to the log.
> + * @size: size of buffer(in bytes).
> + * @eventname: event name to be used for the buffer entry.
> + * @cred: a pointer to a credentials structure for user validation.
> + * @secid: the secid of the task to be validated.
> + *
> + * Based on policy, the buffer is measured into the ima log.
> + */
> +static void process_buffer_measurement(const void *buf, int size,
> + const char *eventname, const struct cred *cred,
> + u32 secid)
> +{
> + int ret = 0;
> + struct ima_template_entry *entry = NULL;
> + struct integrity_iint_cache tmp_iint, *iint = &tmp_iint;
> + struct ima_event_data event_data = {iint, NULL, NULL,
> + NULL, 0, NULL};
Thiago's clean up patch initializes only specific variables, as
needed. Please initialize event_data like:
struct ima_event_data event_data = {.iint = iint};
> + struct {
> + struct ima_digest_data hdr;
> + char digest[IMA_MAX_DIGEST_SIZE];
> + } hash;
> + int violation = 0;
> + int pcr = CONFIG_IMA_MEASURE_PCR_IDX;
> + int action = 0;
> +
> + action = ima_get_action(NULL, cred, secid, 0, KEXEC_CMDLINE, &pcr);
> + if (!(action & IMA_MEASURE))
> + goto out;
> +
> + memset(iint, 0, sizeof(*iint));
> + memset(&hash, 0, sizeof(hash));
> +
> + event_data.filename = eventname;
> +
> + iint->ima_hash = &hash.hdr;
> + iint->ima_hash->algo = ima_hash_algo;
> + iint->ima_hash->length = hash_digest_size[ima_hash_algo];
> +
> + ret = ima_calc_buffer_hash(buf, size, iint->ima_hash);
> + if (ret < 0)
> + goto out;
> +
> + ret = ima_alloc_init_template(&event_data, &entry);
> + if (ret < 0)
> + goto out;
> +
> + if (action & IMA_MEASURE)
> + ret = ima_store_template(entry, violation, NULL, buf, pcr);
> +
> + if (ret < 0) {
> + ima_free_template_entry(entry);
> + }
Remove brackets.
Mimi
> +
> +out:
> + return;
> +}
