From: Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>
To: James Bottomley <James.Bottomley@HansenPartnership.com>
Cc: linux-integrity@vger.kernel.org, Mimi Zohar <zohar@linux.ibm.com>,
David Woodhouse <dwmw2@infradead.org>,
keyrings@vger.kernel.org
Subject: Re: [PATCH v7 3/6] security: keys: trusted: fix TPM2 authorizations
Date: Fri, 6 Mar 2020 21:52:47 +0200 [thread overview]
Message-ID: <20200306195247.GA11362@linux.intel.com> (raw)
In-Reply-To: <20200305022744.12492-4-James.Bottomley@HansenPartnership.com>
On Wed, Mar 04, 2020 at 06:27:41PM -0800, James Bottomley wrote:
> In TPM 1.2 an authorization was a 20 byte number. The spec actually
> recommended you to hash variable length passwords and use the sha1
> hash as the authorization. Because the spec doesn't require this
> hashing, the current authorization for trusted keys is a 40 digit hex
> number. For TPM 2.0 the spec allows the passing in of variable length
> passwords and passphrases directly, so we should allow that in trusted
> keys for ease of use. Update the 'blobauth' parameter to take this
> into account, so we can now use plain text passwords for the keys.
>
> so before
>
> keyctl add trusted kmk "new 32 blobauth=f572d396fae9206628714fb2ce00f72e94f2258f"
>
> after we will accept both the old hex sha1 form as well as a new
> directly supplied password:
>
> keyctl add trusted kmk "new 32 blobauth=hello keyhandle=81000001"
>
> Since a sha1 hex code must be exactly 40 bytes long and a direct
> password must be 20 or less, we use the length as the discriminator
> for which form is input.
>
> Note this is both and enhancement and a potential bug fix. The TPM
> 2.0 spec requires us to strip leading zeros, meaning empyty
> authorization is a zero length HMAC whereas we're currently passing in
> 20 bytes of zeros. A lot of TPMs simply accept this as OK, but the
> Microsoft TPM emulator rejects it with TPM_RC_BAD_AUTH, so this patch
> makes the Microsoft TPM emulator work with trusted keys.
>
> Fixes: 0fe5480303a1 ("keys, trusted: seal/unseal with TPM 2.0 chips")
> Signed-off-by: James Bottomley <James.Bottomley@HansenPartnership.com>
Reviewed-by: Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>
/Jarkko
next prev parent reply other threads:[~2020-03-06 19:52 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-03-05 2:27 [PATCH v7 0/6] TPM 2.0 trusted keys with attached policy James Bottomley
2020-03-05 2:27 ` [PATCH v7 1/6] lib: add ASN.1 encoder James Bottomley
2020-03-05 16:20 ` James Bottomley
2020-03-06 19:10 ` Jarkko Sakkinen
2020-03-05 2:27 ` [PATCH v7 2/6] oid_registry: Add TCG defined OIDS for TPM keys James Bottomley
2020-03-05 2:27 ` [PATCH v7 3/6] security: keys: trusted: fix TPM2 authorizations James Bottomley
2020-03-06 19:52 ` Jarkko Sakkinen [this message]
2020-03-05 2:27 ` [PATCH v7 4/6] security: keys: trusted: use ASN.1 TPM2 key format for the blobs James Bottomley
2020-03-06 20:03 ` Jarkko Sakkinen
2020-03-07 22:00 ` Jarkko Sakkinen
2020-03-09 13:59 ` James Bottomley
2020-03-09 22:08 ` James Bottomley
2020-03-05 2:27 ` [PATCH v7 5/6] security: keys: trusted: add ability to specify arbitrary policy James Bottomley
2020-03-05 2:27 ` [PATCH v7 6/6] security: keys: trusted: implement counter/timer policy James Bottomley
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