From: Mimi Zohar <zohar@linux.ibm.com>
To: James Bottomley <James.Bottomley@HansenPartnership.com>,
Jerry Snitselaar <jsnitsel@redhat.com>,
Jarkko Sakkinen <jarkko.sakkinen@linux.intel.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: Sat, 05 Oct 2019 20:38:53 -0400 [thread overview]
Message-ID: <1570322333.5046.145.camel@linux.ibm.com> (raw)
In-Reply-To: <1570227068.17537.4.camel@HansenPartnership.com>
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.
Mimi
> +
> + return rc;
> +}
> EXPORT_SYMBOL_GPL(tpm_get_random);
next prev parent reply other threads:[~2019-10-06 0:39 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 [this message]
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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