linux-integrity.vger.kernel.org archive mirror
 help / color / mirror / Atom feed
From: Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>
To: Mimi Zohar <zohar@linux.ibm.com>
Cc: James Bottomley <James.Bottomley@HansenPartnership.com>,
	Jerry Snitselaar <jsnitsel@redhat.com>,
	David Safford <david.safford@ge.com>,
	linux-integrity@vger.kernel.org, stable@vger.kernel.org,
	David Howells <dhowells@redhat.com>,
	Herbert Xu <herbert@gondor.apana.org.au>,
	"David S. Miller" <davem@davemloft.net>,
	"open list:ASYMMETRIC KEYS" <keyrings@vger.kernel.org>,
	"open list:CRYPTO API" <linux-crypto@vger.kernel.org>,
	open list <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH] KEYS: asym_tpm: Switch to get_random_bytes()
Date: Mon, 7 Oct 2019 02:52:38 +0300	[thread overview]
Message-ID: <20191006235238.GA16641@linux.intel.com> (raw)
In-Reply-To: <1570322333.5046.145.camel@linux.ibm.com>

On Sat, Oct 05, 2019 at 08:38:53PM -0400, Mimi Zohar wrote:
> On Fri, 2019-10-04 at 15:11 -0700, James Bottomley wrote:
> 
> > +
> > +/**
> > + * tpm_get_random() - get random bytes influenced by the TPM's RNG
> > + * @chip:	a &struct tpm_chip instance, %NULL for the default chip
> > + * @out:	destination buffer for the random bytes
> > + * @max:	the max number of bytes to write to @out
> > + *
> > + * Uses the TPM as a source of input to the kernel random number
> > + * generator and then takes @max bytes directly from the kernel.  In
> > + * the worst (no other entropy) case, this will return the pure TPM
> > + * random number, but if the kernel RNG has any entropy at all it will
> > + * return a mixed entropy output which doesn't rely on a single
> > + * source.
> > + *
> > + * Return: number of random bytes read or a negative error value.
> > + */
> > +int tpm_get_random(struct tpm_chip *chip, u8 *out, size_t max)
> > +{
> > +	int rc;
> > +
> > +	rc = __tpm_get_random(chip, out, max);
> > +	if (rc <= 0)
> > +		return rc;
> > +	/*
> > +	 * assume the TPM produces pure randomness, so the amount of
> > +	 * entropy is the number of bits returned
> > +	 */
> > +	add_hwgenerator_randomness(out, rc, rc * 8);
> > +	get_random_bytes(out, rc);
> 
> Using the TPM as a source of input to the kernel random number
> generator is fine, but please don't change the meaning of trusted
> keys.  The trusted-encrypted keys documentation clearly states
> "Trusted Keys use a TPM both to generate and to seal the keys."
> 
> If you really want to use a different random number source instead of
> the TPM, then define a new trusted key option (eg. rng=kernel), with
> the default being the TPM.

I'll add a patch that updates the documentation because it is clearly
not a good practice to use TPM to generate keys that are not keys
residing inside the TPM.

With TEE coming in, TPM is not the only hardware measure anymore sealing
the keys and we don't want a mess where every hardware asset does their
own proprietary key generation. The proprietary technology should only
take care of the sealing part.

/Jarkko

  reply	other threads:[~2019-10-06 23:52 UTC|newest]

Thread overview: 58+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-09-26 17:16 Jarkko Sakkinen
2019-09-28 18:05 ` Jerry Snitselaar
2019-10-01 20:54   ` Jarkko Sakkinen
2019-10-02 14:00 ` Mimi Zohar
2019-10-03 11:41   ` Jarkko Sakkinen
2019-10-03 11:43     ` Jarkko Sakkinen
2019-10-03 13:02     ` Mimi Zohar
2019-10-03 17:58       ` Jarkko Sakkinen
2019-10-03 18:53         ` Mimi Zohar
2019-10-03 21:51           ` Jarkko Sakkinen
2019-10-03 21:57             ` Jarkko Sakkinen
2019-10-03 22:08               ` Mimi Zohar
2019-10-03 23:59                 ` James Bottomley
2019-10-04 18:22                   ` Jarkko Sakkinen
2019-10-04 18:24                     ` James Bottomley
2019-10-04 18:33                       ` Jerry Snitselaar
2019-10-04 18:42                         ` James Bottomley
2019-10-04 20:07                           ` Jerry Snitselaar
2019-10-04 20:11                             ` Jerry Snitselaar
2019-10-04 22:11                               ` James Bottomley
2019-10-06  0:38                                 ` Mimi Zohar
2019-10-06 23:52                                   ` Jarkko Sakkinen [this message]
2019-10-07 18:08                                     ` Mimi Zohar
2019-10-04 18:20                 ` Jarkko Sakkinen
2019-10-03 22:10               ` Jarkko Sakkinen
2019-10-04 13:26           ` Safford, David (GE Global Research, US)
2019-10-04 18:27             ` Jarkko Sakkinen
2019-10-04 18:30               ` Jarkko Sakkinen
2019-10-04 19:56               ` Safford, David (GE Global Research, US)
2019-10-07  0:05                 ` Jarkko Sakkinen
2019-10-07 22:13                   ` Ken Goldman
2019-10-08 23:49                     ` Jarkko Sakkinen
2019-10-08 23:53                       ` Jarkko Sakkinen
2019-10-09  7:10                         ` Pascal Van Leeuwen
2019-10-09  7:33                         ` Jarkko Sakkinen
2019-10-09  7:41                           ` Jarkko Sakkinen
2019-10-09  8:09                             ` Pascal Van Leeuwen
2019-10-14 19:11                               ` Jarkko Sakkinen
2019-10-09  8:02                           ` Pascal Van Leeuwen
2019-10-09 12:11                         ` Safford, David (GE Global Research, US)
2019-10-14 19:00                           ` Jarkko Sakkinen
2019-10-14 19:29                             ` Jarkko Sakkinen
2019-10-14 19:29                             ` James Bottomley
2019-10-16 11:00                               ` Jarkko Sakkinen
2019-10-16 12:34                                 ` James Bottomley
2019-10-16 16:25                                   ` Jarkko Sakkinen
2019-10-16 19:10                                     ` James Bottomley
2019-10-17 12:52                                       ` Sumit Garg
2019-10-17 12:58                                         ` James Bottomley
2019-10-17 18:04                                       ` Jarkko Sakkinen
2019-10-21 11:39                                         ` Jarkko Sakkinen
2019-10-29  8:42                                           ` Jarkko Sakkinen
2019-10-29 14:58                                             ` James Bottomley
2019-10-31 21:03                                               ` Jarkko Sakkinen
2019-10-18  7:32                                   ` Janne Karhunen
2019-10-03 18:02       ` Jarkko Sakkinen
2019-10-03 18:15         ` Jarkko Sakkinen
2019-10-07 10:33     ` Janne Karhunen

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=20191006235238.GA16641@linux.intel.com \
    --to=jarkko.sakkinen@linux.intel.com \
    --cc=James.Bottomley@HansenPartnership.com \
    --cc=davem@davemloft.net \
    --cc=david.safford@ge.com \
    --cc=dhowells@redhat.com \
    --cc=herbert@gondor.apana.org.au \
    --cc=jsnitsel@redhat.com \
    --cc=keyrings@vger.kernel.org \
    --cc=linux-crypto@vger.kernel.org \
    --cc=linux-integrity@vger.kernel.org \
    --cc=linux-kernel@vger.kernel.org \
    --cc=stable@vger.kernel.org \
    --cc=zohar@linux.ibm.com \
    --subject='Re: [PATCH] KEYS: asym_tpm: Switch to get_random_bytes()' \
    /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

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).