Re: [PATCH 1/2] ima: use the IMA configured hash algo to calculate the boot aggregate

[Jerry Snitselaar]

On Mon Jan 27 20, Mimi Zohar wrote:
> The boot aggregate is a cumulative SHA1 hash over TPM registers 0 - 7.
> NIST has depreciated the usage of SHA1 in most instances.  Instead of
> continuing to use SHA1 to calculate the boot_aggregate, use the
> configured IMA default hash algorithm.
>
> Although the IMA measurement list boot_aggregate template data contains
> the hash algorithm followed by the digest, allowing verifiers (e.g.
> attesttaion servers) to calculate and verify the boot_aggregate, the
> verifiers might not have the knowledge of what constitutes a good value
> based on a different hash algorithm.
>
> Signed-off-by: Mimi Zohar <zohar@xxxxxxxxxxxxx>
> ---
> security/integrity/ima/ima_init.c | 8 ++++----
> 1 file changed, 4 insertions(+), 4 deletions(-)
>
> diff --git a/security/integrity/ima/ima_init.c b/security/integrity/ima/ima_init.c
> index 195cb4079b2b..b1b334fe0db5 100644
> --- a/security/integrity/ima/ima_init.c
> +++ b/security/integrity/ima/ima_init.c
> @@ -27,7 +27,7 @@ struct tpm_chip *ima_tpm_chip;
> /* Add the boot aggregate to the IMA measurement list and extend
>  * the PCR register.
>  *
> - * Calculate the boot aggregate, a SHA1 over tpm registers 0-7,
> + * Calculate the boot aggregate, a hash over tpm registers 0-7,
>  * assuming a TPM chip exists, and zeroes if the TPM chip does not
>  * exist.  Add the boot aggregate measurement to the measurement
>  * list and extend the PCR register.
> @@ -51,14 +51,14 @@ static int __init ima_add_boot_aggregate(void)
> 	int violation = 0;
> 	struct {
> 		struct ima_digest_data hdr;
> -		char digest[TPM_DIGEST_SIZE];
> +		char digest[TPM_MAX_DIGEST_SIZE];
> 	} hash;
>
> 	memset(iint, 0, sizeof(*iint));
> 	memset(&hash, 0, sizeof(hash));
> 	iint->ima_hash = &hash.hdr;
> -	iint->ima_hash->algo = HASH_ALGO_SHA1;
> -	iint->ima_hash->length = SHA1_DIGEST_SIZE;
> +	iint->ima_hash->algo = ima_hash_algo;
> +	iint->ima_hash->length = hash_digest_size[ima_hash_algo];
>
> 	if (ima_tpm_chip) {
> 		result = ima_calc_boot_aggregate(&hash.hdr);
> --
> 2.7.5

Tested the patches on the Dell and no longer spits out the error messages on boot.
/sys/kernel/security/ima/ascii_runtime_measurements shows the boot aggregate.

Is there something else I should look at to verify it is functioning properly?

Regards,
Jerry