linux-kernel - Re: [Linux-ima-devel] [PATCH v2 4/5] keys, trusted: modify arguments of tpm_pcr

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Date:   Tue, 30 May 2017 09:36:13 +0200
From:   Roberto Sassu <roberto.sassu@...wei.com>
To:     Mimi Zohar <zohar@...ux.vnet.ibm.com>,
        <tpmdd-devel@...ts.sourceforge.net>
CC:     <linux-ima-devel@...ts.sourceforge.net>,
        <linux-security-module@...r.kernel.org>,
        <keyrings@...r.kernel.org>, <linux-kernel@...r.kernel.org>
Subject: Re: [Linux-ima-devel] [PATCH v2 4/5] keys, trusted: modify arguments
 of tpm_pcr_extend()

On 5/30/2017 5:35 AM, Mimi Zohar wrote:
> On Fri, 2017-05-05 at 16:21 +0200, Roberto Sassu wrote:
>> pcrlock() has been modified to pass the correct arguments
>> to tpm_pcr_extend(): the pointer of a tpm2_digest structure containing
>> a random value generated by tpm_get_random() and the size of the array (1).
>
> If the number of arguments is wrong, that means the patch that
> introduced the change is not bi-sect safe.  (This comment is
> applicable to patch 5/5 too.)

Jarkko (the TPM driver maintainer) asked me to not introduce
a new function to pass multiple digests, but to modify
the parameters of tpm_pcr_extend().

Roberto


>
> Mimi
>
>> Signed-off-by: Roberto Sassu <roberto.sassu@...wei.com>
>> ---
>>  security/keys/trusted.c | 6 +++---
>>  1 file changed, 3 insertions(+), 3 deletions(-)
>>
>> diff --git a/security/keys/trusted.c b/security/keys/trusted.c
>> index 2ae31c5..3eb89e6 100644
>> --- a/security/keys/trusted.c
>> +++ b/security/keys/trusted.c
>> @@ -377,15 +377,15 @@ static int trusted_tpm_send(const u32 chip_num, unsigned char *cmd,
>>   */
>>  static int pcrlock(const int pcrnum)
>>  {
>> -	unsigned char hash[SHA1_DIGEST_SIZE];
>> +	struct tpm2_digest digestarg = {.alg_id = TPM2_ALG_SHA1};
>>  	int ret;
>>
>>  	if (!capable(CAP_SYS_ADMIN))
>>  		return -EPERM;
>> -	ret = tpm_get_random(TPM_ANY_NUM, hash, SHA1_DIGEST_SIZE);
>> +	ret = tpm_get_random(TPM_ANY_NUM, digestarg.digest, SHA1_DIGEST_SIZE);
>>  	if (ret != SHA1_DIGEST_SIZE)
>>  		return ret;
>> -	return tpm_pcr_extend(TPM_ANY_NUM, pcrnum, hash) ? -EINVAL : 0;
>> +	return tpm_pcr_extend(TPM_ANY_NUM, pcrnum, 1, &digestarg) ? -EINVAL : 0;
>>  }
>>
>>  /*
>