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From: Jerry Snitselaar <jsnitsel@redhat.com>
To: James Bottomley <James.Bottomley@HansenPartnership.com>,
	Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>,
	Mimi Zohar <zohar@linux.ibm.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: Fri, 4 Oct 2019 13:11:34 -0700	[thread overview]
Message-ID: <20191004201134.nuesk6hxtxajnxh2@cantor> (raw)
In-Reply-To: <20191004200728.xoj6jlgbhv57gepc@cantor>

On Fri Oct 04 19, Jerry Snitselaar wrote:
>On Fri Oct 04 19, James Bottomley wrote:
>>On Fri, 2019-10-04 at 11:33 -0700, Jerry Snitselaar wrote:
>>>On Fri Oct 04 19, James Bottomley wrote:
>>>> On Fri, 2019-10-04 at 21:22 +0300, Jarkko Sakkinen wrote:
>>>> > On Thu, Oct 03, 2019 at 04:59:37PM -0700, James Bottomley wrote:
>>>> > > I think the principle of using multiple RNG sources for strong
>>>> > > keys is a sound one, so could I propose a compromise:  We have
>>>> > > a tpm subsystem random number generator that, when asked for
>>>> > > <n> random bytes first extracts <n> bytes from the TPM RNG and
>>>> > > places it into the kernel entropy pool and then asks for <n>
>>>> > > random bytes from the kernel RNG? That way, it will always have
>>>> > > the entropy to satisfy the request and in the worst case, where
>>>> > > the kernel has picked up no other entropy sources at all it
>>>> > > will be equivalent to what we have now (single entropy source)
>>>> > > but usually it will be a much better mixed entropy source.
>>>> >
>>>> > I think we should rely the existing architecture where TPM is
>>>> > contributing to the entropy pool as hwrng.
>>>>
>>>> That doesn't seem to work: when I trace what happens I see us
>>>> inject 32 bytes of entropy at boot time, but never again.  I think
>>>> the problem is the kernel entropy pool is push not pull and we have
>>>> no triggering event in the TPM to get us to push.  I suppose we
>>>> could set a timer to do this or perhaps there is a pull hook and we
>>>> haven't wired it up correctly?
>>>>
>>>> James
>>>>
>>>
>>>Shouldn't hwrng_fillfn be pulling from it?
>>
>>It should, but the problem seems to be it only polls the "current" hw
>>rng ... it doesn't seem to have a concept that there may be more than
>>one.  What happens, according to a brief reading of the code, is when
>>multiple are registered, it determines what the "best" one is and then
>>only pulls from that.  What I think it should be doing is filling from
>>all of them using the entropy quality to adjust how many bits we get.
>>
>>James
>>
>
>Most of them don't even set quality, including the tpm, so they end up
>at the end of the list. For the ones that do I'm not sure how they determined
>the value. For example virtio-rng sets quality to 1000.

I should have added that I like that idea though.

  reply	other threads:[~2019-10-04 20:11 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 [this message]
2019-10-04 22:11                               ` James Bottomley
2019-10-06  0:38                                 ` Mimi Zohar
2019-10-06 23:52                                   ` Jarkko Sakkinen
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

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