From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jarkko Sakkinen Date: Fri, 06 Mar 2020 19:52:47 +0000 Subject: Re: [PATCH v7 3/6] security: keys: trusted: fix TPM2 authorizations Message-Id: <20200306195247.GA11362@linux.intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable List-Id: References: <20200305022744.12492-1-James.Bottomley@HansenPartnership.com> <20200305022744.12492-4-James.Bottomley@HansenPartnership.com> In-Reply-To: <20200305022744.12492-4-James.Bottomley@HansenPartnership.com> To: James Bottomley Cc: linux-integrity@vger.kernel.org, Mimi Zohar , David Woodhouse , keyrings@vger.kernel.org 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. >=20 > so before >=20 > keyctl add trusted kmk "new 32 blobauth=F572d396fae9206628714fb2ce00f72e9= 4f2258f" >=20 > after we will accept both the old hex sha1 form as well as a new > directly supplied password: >=20 > keyctl add trusted kmk "new 32 blobauth=3Dhello keyhandle=81000001" >=20 > 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. >=20 > 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. >=20 > Fixes: 0fe5480303a1 ("keys, trusted: seal/unseal with TPM 2.0 chips") > Signed-off-by: James Bottomley Reviewed-by: Jarkko Sakkinen /Jarkko