Subject: Re: [PATCH v6 5/9] powerpc/ima: add measurement rules to ima arch specific policy

From: Mimi Zohar <[email-masked]>
Date: Sun, 29 Sep 2019 00:20:38 -0400

On Fri, 2019-09-27 at 10:25 -0400, Nayna Jain wrote:
> This patch adds the measurement rules to the arch specific policies for the
> systems with trusted boot.
> 

on trusted boot enabled systems.

> Signed-off-by: Nayna Jain <[email-masked]>

Minor comment correction below.

Reviewed-by: Mimi Zohar <[email-masked]>

> ---
>  arch/powerpc/kernel/ima_arch.c | 44 +++++++++++++++++++++++++++++++---
>  1 file changed, 41 insertions(+), 3 deletions(-)
> 
> diff --git a/arch/powerpc/kernel/ima_arch.c b/arch/powerpc/kernel/ima_arch.c
> index 39401b67f19e..77c61b142042 100644
> --- a/arch/powerpc/kernel/ima_arch.c
> +++ b/arch/powerpc/kernel/ima_arch.c
> @@ -12,8 +12,18 @@ bool arch_ima_get_secureboot(void)
>  	return is_powerpc_os_secureboot_enabled();
>  }
>  
> -/* Defines IMA appraise rules for secureboot */
> +/*
> + * The "arch_rules" contains both the securebot and trustedboot rules for adding
> + * the kexec kernel image and kernel modules file hashes to the IMA measurement
> + * list and verifying the file signatures against known good values.
> + *
> + * The "appraise_type=imasig|modsig" option allows the good signature to be
> + * stored as an xattr or as an appended signature. The "template=ima-modsig"
> + * option includes the appended signature in the IMA measurement list.

includes the appended signature, when available, in the IMA
measurement list. 

> + */
>  static const char *const arch_rules[] = {
> +	"measure func=KEXEC_KERNEL_CHECK template=ima-modsig",
> +	"measure func=MODULE_CHECK template=ima-modsig",
>  	"appraise func=KEXEC_KERNEL_CHECK appraise_type=imasig|modsig",
>  #if !IS_ENABLED(CONFIG_MODULE_SIG)
>  	"appraise func=MODULE_CHECK appraise_type=imasig|modsig",
> @@ -22,12 +32,40 @@ static const char *const arch_rules[] = {
>  };
>  
>  /*
> - * Returns the relevant IMA arch policies based on the system secureboot state.
> + * The "measure_rules" are enabled only on "trustedboot" enabled systems.
> + * These rules add the kexec kernel image and kernel modules file hashes to
> + * the IMA measurement list.
> + */
> +static const char *const measure_rules[] = {
> +	"measure func=KEXEC_KERNEL_CHECK",
> +	"measure func=MODULE_CHECK",
> +	NULL
> +};
> +
> +/*
> + * Returns the relevant IMA arch policies based on the system secureboot
> + * and trustedboot state.
>   */
>  const char *const *arch_get_ima_policy(void)
>  {
> -	if (is_powerpc_os_secureboot_enabled())
> +	const char *const *rules;
> +	int offset = 0;
> +
> +	for (rules = arch_rules; *rules != NULL; rules++) {
> +		if (strncmp(*rules, "appraise", 8) == 0)
> +			break;
> +		offset++;
> +	}
> +
> +	if (is_powerpc_os_secureboot_enabled()
> +	    && is_powerpc_trustedboot_enabled())
>  		return arch_rules;
>  
> +	if (is_powerpc_os_secureboot_enabled())
> +		return arch_rules + offset;
> +
> +	if (is_powerpc_trustedboot_enabled())
> +		return measure_rules;
> +
>  	return NULL;
>  }