linux-kernel - Re: [PATCH v9 6/6] tpm: pass an array of tpm_extend_digest structures to tpm_pcr

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Message-Id: <1549048506.6993.73.camel@linux.ibm.com>
Date:   Fri, 01 Feb 2019 14:15:06 -0500
From:   Mimi Zohar <zohar@...ux.ibm.com>
To:     Roberto Sassu <roberto.sassu@...wei.com>,
        jarkko.sakkinen@...ux.intel.com, david.safford@...com,
        monty.wiseman@...com, matthewgarrett@...gle.com
Cc:     linux-integrity@...r.kernel.org,
        linux-security-module@...r.kernel.org, keyrings@...r.kernel.org,
        linux-kernel@...r.kernel.org, silviu.vlasceanu@...wei.com
Subject: Re: [PATCH v9 6/6] tpm: pass an array of tpm_extend_digest
 structures to tpm_pcr_extend()

Hi Roberto,

Sorry for the delayed review.  A few comments inline below, minor
suggestions.

> diff --git a/security/integrity/ima/ima.h b/security/integrity/ima/ima.h
> index cc12f3449a72..e6b2dcb0846a 100644
> --- a/security/integrity/ima/ima.h
> +++ b/security/integrity/ima/ima.h
> @@ -56,6 +56,7 @@ extern int ima_policy_flag;
>  extern int ima_hash_algo;
>  extern int ima_appraise;
>  extern struct tpm_chip *ima_tpm_chip;
> +extern struct tpm_digest *digests;
>  
>  /* IMA event related data */
>  struct ima_event_data {
> diff --git a/security/integrity/ima/ima_init.c b/security/integrity/ima/ima_init.c
> index 6bb42a9c5e47..296a965b11ef 100644
> --- a/security/integrity/ima/ima_init.c
> +++ b/security/integrity/ima/ima_init.c
> @@ -27,6 +27,7 @@
>  /* name for boot aggregate entry */
>  static const char boot_aggregate_name[] = "boot_aggregate";
>  struct tpm_chip *ima_tpm_chip;
> +struct tpm_digest *digests;

"digests" is used in the new ima_init_digests() and in
ima_pcr_extend().  It's nice that the initialization routines are
grouped together here in ima_init.c, but wouldn't it better to define
"digests" in ima_queued.c, where it is currently being used?
 "digests" could then be defined as static.

>  
>  /* Add the boot aggregate to the IMA measurement list and extend
>   * the PCR register.
> @@ -104,6 +105,24 @@ void __init ima_load_x509(void)
>  }
>  #endif
>  
> +int __init ima_init_digests(void)
> +{
> +	int i;
> +
> +	if (!ima_tpm_chip)
> +		return 0;
> +
> +	digests = kcalloc(ima_tpm_chip->nr_allocated_banks, sizeof(*digests),
> +			  GFP_NOFS);
> +	if (!digests)
> +		return -ENOMEM;
> +
> +	for (i = 0; i < ima_tpm_chip->nr_allocated_banks; i++)
> +		digests[i].alg_id = ima_tpm_chip->allocated_banks[i].alg_id;
> +
> +	return 0;
> +}
> +
>  int __init ima_init(void)
>  {
>  	int rc;
> @@ -125,6 +144,9 @@ int __init ima_init(void)
>  
>  	ima_load_kexec_buffer();
>  
> +	rc = ima_init_digests();

Ok. Getting the tpm chip is at the beginning of this function.
 Deferring allocating "digests" to here, avoids having to free memory
on failure.

ima_load_kexec_buffer() restores prior measurements, but doesn't
extend the TPM.  For anyone reading the code, a short comment above
ima_load_kexec_buffer() would make sense.

Mimi
   
> +	if (rc != 0)
> +		return rc;
>  	rc = ima_add_boot_aggregate();	/* boot aggregate must be first entry */
>  	if (rc != 0)
>  		return rc;
> diff --git a/security/integrity/ima/ima_queue.c b/security/integrity/ima/ima_queue.c
> index 0e41dc1df1d4..719e88ca58f6 100644
> --- a/security/integrity/ima/ima_queue.c
> +++ b/security/integrity/ima/ima_queue.c
> @@ -140,11 +140,15 @@ unsigned long ima_get_binary_runtime_size(void)
>  static int ima_pcr_extend(const u8 *hash, int pcr)
>  {
>  	int result = 0;
> +	int i;
>  
>  	if (!ima_tpm_chip)
>  		return result;
>  
> -	result = tpm_pcr_extend(ima_tpm_chip, pcr, hash);
> +	for (i = 0; i < ima_tpm_chip->nr_allocated_banks; i++)
> +		memcpy(digests[i].digest, hash, TPM_DIGEST_SIZE);
> +
> +	result = tpm_pcr_extend(ima_tpm_chip, pcr, digests);
>  	if (result != 0)
>  		pr_err("Error Communicating to TPM chip, result: %d\n", result);
>  	return result;
>