From: Sumit Garg <sumit.garg@linaro.org>
To: James Bottomley <James.Bottomley@hansenpartnership.com>
Cc: Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>,
"Safford, David (GE Global Research, US)" <david.safford@ge.com>,
Ken Goldman <kgold@linux.ibm.com>,
Mimi Zohar <zohar@linux.ibm.com>,
"linux-integrity@vger.kernel.org"
<linux-integrity@vger.kernel.org>,
"stable@vger.kernel.org" <stable@vger.kernel.org>,
"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: Thu, 17 Oct 2019 18:22:17 +0530 [thread overview]
Message-ID: <CAFA6WYNNNTWXDrp_R3M60srGJYjJdRoaNpSnP54V_BinYYXTMA@mail.gmail.com> (raw)
In-Reply-To: <1571253029.17520.5.camel@HansenPartnership.com>
On Thu, 17 Oct 2019 at 00:40, James Bottomley
<James.Bottomley@hansenpartnership.com> wrote:
>
> On Wed, 2019-10-16 at 19:25 +0300, Jarkko Sakkinen wrote:
> > On Wed, Oct 16, 2019 at 08:34:12AM -0400, James Bottomley wrote:
> > > reversible ciphers are generally frowned upon in random number
> > > generation, that's why the krng uses chacha20. In general I think
> > > we shouldn't try to code our own mixing and instead should get the
> > > krng to do it for us using whatever the algorithm du jour that the
> > > crypto guys have blessed is. That's why I proposed adding the TPM
> > > output to the krng as entropy input and then taking the output of
> > > the krng.
> >
> > It is already registered as hwrng. What else?
>
> It only contributes entropy once at start of OS.
>
Why not just configure quality parameter of TPM hwrng as follows? It
would automatically initiate a kthread during hwrng_init() to feed
entropy from TPM to kernel random numbers pool (see:
drivers/char/hw_random/core.c +142).
diff --git a/drivers/char/tpm/tpm-chip.c b/drivers/char/tpm/tpm-chip.c
index 3d6d394..fcc3817 100644
--- a/drivers/char/tpm/tpm-chip.c
+++ b/drivers/char/tpm/tpm-chip.c
@@ -548,6 +548,7 @@ static int tpm_add_hwrng(struct tpm_chip *chip)
"tpm-rng-%d", chip->dev_num);
chip->hwrng.name = chip->hwrng_name;
chip->hwrng.read = tpm_hwrng_read;
+ chip->hwrng.quality = 1024; /* Here we assume TPM provides
full entropy */
return hwrng_register(&chip->hwrng);
}
> > Was the issue that it is only used as seed when the rng is init'd
> > first? I haven't at this point gone to the internals of krng.
>
> Basically it was similar to your xor patch except I got the kernel rng
> to do the mixing, so it would use the chacha20 cipher at the moment
> until they decide that's unsafe and change it to something else:
>
> https://lore.kernel.org/linux-crypto/1570227068.17537.4.camel@HansenPartnership.com/
>
> It uses add_hwgenerator_randomness() to do the mixing. It also has an
> unmixed source so that read of the TPM hwrng device works as expected.
Above suggestion is something similar to yours but utilizing the
framework already provided via hwrng core.
-Sumit
>
> James
>
>
>
>
>
next prev parent reply other threads:[~2019-10-17 12:52 UTC|newest]
Thread overview: 58+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-09-26 17:16 [PATCH] KEYS: asym_tpm: Switch to get_random_bytes() 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
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 [this message]
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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