tpmdd-devel.lists.sourceforge.net archive mirror
 help / color / mirror / Atom feed
From: Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>
To: Roberto Sassu <roberto.sassu@huawei.com>
Cc: tpmdd-devel@lists.sourceforge.net,
	linux-ima-devel@lists.sourceforge.net,
	linux-security-module@vger.kernel.org, keyrings@vger.kernel.org,
	linux-kernel@vger.kernel.org
Subject: Re: [PATCH v2 1/5] tpm: introduce tpm_pcr_algorithms()
Date: Sat, 20 May 2017 16:00:19 +0300	[thread overview]
Message-ID: <20170520130019.3dw5emkgqjlcvtjp@intel.com> (raw)
In-Reply-To: <d2974dd2-e30d-e8f0-a60a-2147f3290670@huawei.com>

On Mon, May 15, 2017 at 03:18:41PM +0200, Roberto Sassu wrote:
> 
> 
> On 5/15/2017 12:36 PM, Jarkko Sakkinen wrote:
> > On Fri, May 05, 2017 at 04:21:48PM +0200, Roberto Sassu wrote:
> > > This function allows TPM users to know which algorithms the TPM supports.
> > > It stores the algorithms in a static array of 'enum tpm2_algorithms',
> > > allocated by the caller. If the array is not large enough, the function
> > > returns an error. Otherwise, it returns the number of algorithms written
> > > to the array. If the TPM version is 1.2, the function writes TPM2_ALG_SHA1
> > > to first element of the array.
> > > 
> > > Writing the algorithm also for TPM 1.2 has the advantage that callers
> > > can use the API, tpm_pcr_algorithms() and tpm_pcr_extend(), regardless
> > > of the TPM version.
> > > 
> > > A minor change added to this patch was to make available the size of
> > > the active_banks array, member of the tpm_chip structure, outside
> > > the TPM driver. The array size (TPM_ACTIVE_BANKS_MAX) has been exported
> > > to include/linux/tpm.h.
> > > 
> > > With this information, callers of tpm_pcr_algorithms() can provide
> > > a static array with enough room for all the algorithms, instead
> > > of receiving the pointer of a dynamic array that they have to free later.
> > > 
> > > Signed-off-by: Roberto Sassu <roberto.sassu@huawei.com>
> > > ---
> > > v2
> > > 
> > > - tpm_pcr_algorithms() returns supported algorithms also for TPM 1.2
> > > 
> > >  drivers/char/tpm/tpm-interface.c | 46 ++++++++++++++++++++++++++++++++++++++++
> > >  drivers/char/tpm/tpm.h           | 13 +-----------
> > >  include/linux/tpm.h              | 19 +++++++++++++++++
> > >  3 files changed, 66 insertions(+), 12 deletions(-)
> > > 
> > > diff --git a/drivers/char/tpm/tpm-interface.c b/drivers/char/tpm/tpm-interface.c
> > > index 4ed08ab..b90de3d 100644
> > > --- a/drivers/char/tpm/tpm-interface.c
> > > +++ b/drivers/char/tpm/tpm-interface.c
> > > @@ -911,6 +911,52 @@ int tpm_pcr_extend(u32 chip_num, int pcr_idx, const u8 *hash)
> > >  EXPORT_SYMBOL_GPL(tpm_pcr_extend);
> > > 
> > >  /**
> > > + * tpm_pcr_algorithms - get TPM IDs of active PCR banks algorithms
> > 
> > The grammar is incorrect here I believe. Should rather be
> > 
> >   "algorithms of the active PCR banks"
> > 
> > And there is no such thing as "TPM ID".
> > 
> > > + * @chip_num:	tpm idx # or ANY
> > > + * @count:	# of items in algorithms
> > > + * @algorithms:	array of TPM IDs
> > > + *
> > > + * Returns < 0 on error, and the number of active PCR banks on success.
> > > + *
> > > + * TPM 1.2 has always one SHA1 bank.
> > > + */
> > > +int tpm_pcr_algorithms(u32 chip_num, int count,
> > > +		       enum tpm2_algorithms *algorithms)
> >                        unsigned int
> > 
> > In addition the function name is not too greatg,
> > 
> > Your syntax for return value is not correct. In addition after
> > describing the return value there should not be anything. You should
> > study
> > 
> > https://www.kernel.org/doc/Documentation/kernel-doc-nano-HOWTO.txt
> > 
> > Better name for the function would be tpm_get_pcr_algorithms().
> > 
> > > +{
> > > +	struct tpm_chip *chip;
> > > +	int i;
> > > +
> > > +	if (count <= 0 || algorithms == NULL)
> > > +		return -EINVAL;
> > 
> > Is there a legal case where caller would pass these values? Now it
> > looks like that there is.
> > 
> > 'count' should unsigned int and zero should be a legal value for
> > count.
> 
> I wanted to avoid that a negative value returned by tpm_pcr_algorithms()
> is passed to tpm_pcr_extend() as unsigned int.

Why would you pass a negative value? I'm sorry but I have to admit tht I'm
seriously not computing your argument.

> > That said I think the whole design is wrong as you could calculate
> > array for algs only one time and pass a const reference to it on
> > request.
> 
> Ok. If I understood it correctly, you are saying to pass a const
> reference of chip->active_banks. Then, I should also:
> 
> - add a new field (e.g. active_banks_num) in the tpm_chip structure
>   to store the number of algorithms supported by the TPM (unless,
>   I should determine it every time tpm_pcr_algorithms() is called)
> - initialize chip->active_banks and chip->active_banks_num
>   respectively to TPM2_ALG_SHA1 and 1 in tpm1_auto_startup()
> 
> Roberto

Something along those lines.

Doing precalcuation makes the code more stable as you can only fall to
an error conditio when the driver is initialized.

/Jarkko

  parent reply	other threads:[~2017-05-20 13:00 UTC|newest]

Thread overview: 31+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2017-05-05 14:21 [PATCH v2 0/5] Updated API for TPM 2.0 PCR extend Roberto Sassu
2017-05-05 14:21 ` [PATCH v2 1/5] tpm: introduce tpm_pcr_algorithms() Roberto Sassu
2017-05-15 10:36   ` Jarkko Sakkinen
     [not found]     ` <20170515103623.sumyo2vyldezual2-ral2JQCrhuEAvxtiuMwx3w@public.gmane.org>
2017-05-15 13:18       ` Roberto Sassu
     [not found]         ` <d2974dd2-e30d-e8f0-a60a-2147f3290670-hv44wF8Li93QT0dZR+AlfA@public.gmane.org>
2017-05-17  8:42           ` Roberto Sassu
2017-05-20 13:18             ` Jarkko Sakkinen
     [not found]               ` <20170520131846.e3niqiknlrttbdf4-ral2JQCrhuEAvxtiuMwx3w@public.gmane.org>
2017-05-22  9:07                 ` Roberto Sassu
2017-05-24 17:35                   ` Jarkko Sakkinen
     [not found]                     ` <20170524173521.yiiohct7brkcozyk-ral2JQCrhuEAvxtiuMwx3w@public.gmane.org>
2017-05-30  8:44                       ` Roberto Sassu
     [not found]                         ` <1cf4fbb1-5683-ceb4-2d5b-8ade25a91e83-hv44wF8Li93QT0dZR+AlfA@public.gmane.org>
2017-05-31 11:39                           ` Jarkko Sakkinen
2017-05-20 13:00         ` Jarkko Sakkinen [this message]
2017-05-05 14:21 ` [PATCH v2 2/5] tpm: introduce tpm_pcr_algo_to_crypto() and tpm_pcr_algo_from_crypto() Roberto Sassu
     [not found]   ` <20170505142152.29795-3-roberto.sassu-hv44wF8Li93QT0dZR+AlfA@public.gmane.org>
2017-05-15 11:16     ` Jarkko Sakkinen
     [not found]       ` <20170515111629.urjvbhqzohv4vakc-ral2JQCrhuEAvxtiuMwx3w@public.gmane.org>
2017-05-15 14:22         ` Roberto Sassu
2017-05-20 13:22           ` Jarkko Sakkinen
     [not found]             ` <20170520132217.t7n7l2pjn7i63hbm-ral2JQCrhuEAvxtiuMwx3w@public.gmane.org>
2017-05-22  7:21               ` Roberto Sassu
2017-05-24 17:33                 ` Jarkko Sakkinen
2017-05-24 20:25                   ` Jarkko Sakkinen
2017-05-30 10:24                     ` Roberto Sassu
2017-05-31 11:40                       ` Jarkko Sakkinen
2017-05-05 14:21 ` [PATCH v2 3/5] tpm: pass multiple digests to tpm_pcr_extend() Roberto Sassu
     [not found]   ` <20170505142152.29795-4-roberto.sassu-hv44wF8Li93QT0dZR+AlfA@public.gmane.org>
2017-05-30  3:29     ` [Linux-ima-devel] " Mimi Zohar
2017-05-30  7:28       ` Roberto Sassu
2017-05-30 11:25         ` Mimi Zohar
     [not found]           ` <1496143547.3841.517.camel-23VcF4HTsmIX0ybBhKVfKdBPR1lH4CV8@public.gmane.org>
2017-05-30 13:25             ` Roberto Sassu
2017-05-05 14:21 ` [PATCH v2 4/5] keys, trusted: modify arguments of tpm_pcr_extend() Roberto Sassu
2017-05-30  3:35   ` [Linux-ima-devel] " Mimi Zohar
     [not found]     ` <1496115337.3841.485.camel-23VcF4HTsmIX0ybBhKVfKdBPR1lH4CV8@public.gmane.org>
2017-05-30  7:36       ` Roberto Sassu
2017-05-30 12:06         ` Mimi Zohar
     [not found]           ` <1496145961.3841.537.camel-23VcF4HTsmIX0ybBhKVfKdBPR1lH4CV8@public.gmane.org>
2017-05-30 13:41             ` Roberto Sassu
2017-05-05 14:21 ` [PATCH v2 5/5] ima: " Roberto Sassu

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=20170520130019.3dw5emkgqjlcvtjp@intel.com \
    --to=jarkko.sakkinen@linux.intel.com \
    --cc=keyrings@vger.kernel.org \
    --cc=linux-ima-devel@lists.sourceforge.net \
    --cc=linux-kernel@vger.kernel.org \
    --cc=linux-security-module@vger.kernel.org \
    --cc=roberto.sassu@huawei.com \
    --cc=tpmdd-devel@lists.sourceforge.net \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).