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From: James Bottomley <James.Bottomley@HansenPartnership.com>
To: linux-integrity@vger.kernel.org
Cc: linux-crypto@vger.kernel.org,
	linux-security-module@vger.kernel.org,
	Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>
Subject: [PATCH v6 10/12] tpm: add the null key name as a tpm2 sysfs variable
Date: Mon, 09 Sep 2019 13:24:27 +0100
Message-ID: <1568031867.6613.39.camel@HansenPartnership.com> (raw)
In-Reply-To: <1568031408.6613.29.camel@HansenPartnership.com>

This is the last component of encrypted tpm2 session handling that
allows us to verify from userspace that the key derived from the NULL
seed genuinely belongs to the TPM and has not been spoofed.

The procedure for doing this involves creating an attestation identity
key (which requires verification of the TPM EK certificate) and then
using that AIK to sign a certification of the Elliptic Curve key over
the NULL seed.  Userspace must create this EC Key using the parameters
prescribed in TCG TPM v2.0 Provisioning Guidance for the SRK ECC; if
this is done correctly the names will match and the TPM can then run a
TPM2_Certify operation on this derived primary key using the newly
created AIK.

Signed-off-by: James Bottomley <James.Bottomley@HansenPartnership.com>
---
 drivers/char/tpm/tpm-sysfs.c | 27 ++++++++++++++++++++++++++-
 1 file changed, 26 insertions(+), 1 deletion(-)

diff --git a/drivers/char/tpm/tpm-sysfs.c b/drivers/char/tpm/tpm-sysfs.c
index d9caedda075b..07aa8f427b96 100644
--- a/drivers/char/tpm/tpm-sysfs.c
+++ b/drivers/char/tpm/tpm-sysfs.c
@@ -309,6 +309,19 @@ static ssize_t timeouts_show(struct device *dev, struct device_attribute *attr,
 }
 static DEVICE_ATTR_RO(timeouts);
 
+static ssize_t null_name_show(struct device *dev, struct device_attribute *attr,
+			      char *buf)
+{
+	struct tpm_chip *chip = to_tpm_chip(dev);
+	int size = TPM2_NAME_SIZE;
+
+	bin2hex(buf, chip->tpmkeyname, size);
+	size *= 2;
+	buf[size++] = '\n';
+	return size;
+}
+static DEVICE_ATTR_RO(null_name);
+
 static struct attribute *tpm_dev_attrs[] = {
 	&dev_attr_pubek.attr,
 	&dev_attr_pcrs.attr,
@@ -323,17 +336,29 @@ static struct attribute *tpm_dev_attrs[] = {
 	NULL,
 };
 
+static struct attribute *tpm2_dev_attrs[] = {
+	&dev_attr_null_name.attr,
+	NULL,
+};
+
 static const struct attribute_group tpm_dev_group = {
 	.attrs = tpm_dev_attrs,
 };
 
+static const struct attribute_group tpm2_dev_group = {
+	.attrs = tpm2_dev_attrs,
+};
+
 void tpm_sysfs_add_device(struct tpm_chip *chip)
 {
 	/* XXX: If you wish to remove this restriction, you must first update
 	 * tpm_sysfs to explicitly lock chip->ops.
 	 */
-	if (chip->flags & TPM_CHIP_FLAG_TPM2)
+	if (chip->flags & TPM_CHIP_FLAG_TPM2) {
+		WARN_ON(chip->groups_cnt != 0);
+		chip->groups[chip->groups_cnt++] = &tpm2_dev_group;
 		return;
+	}
 
 	/* The sysfs routines rely on an implicit tpm_try_get_ops, device_del
 	 * is called before ops is null'd and the sysfs core synchronizes this
-- 
2.16.4


  parent reply index

Thread overview: 27+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-09-09 12:16 [PATCH v6 00/12] add integrity and security to TPM2 transactions James Bottomley
2019-09-09 12:17 ` [PATCH v6 01/12] tpm-buf: move from static inlines to real functions James Bottomley
2019-09-20 14:06   ` Jarkko Sakkinen
2019-09-20 14:06     ` Jarkko Sakkinen
2019-09-20 15:53       ` James Bottomley
2019-09-09 12:18 ` [PATCH v6 02/12] tpm-buf: add handling for TPM2B types James Bottomley
2019-09-20 14:18   ` Jarkko Sakkinen
2019-09-24 11:12     ` James Bottomley
2019-09-25 12:34       ` Jarkko Sakkinen
2019-09-25 12:34         ` Jarkko Sakkinen
2019-09-09 12:19 ` [PATCH v6 03/12] tpm-buf: add cursor based functions for response parsing James Bottomley
2019-09-09 12:19 ` [PATCH v6 04/12] tpm2-space: export the context save and load commands James Bottomley
2019-09-09 12:20 ` [PATCH v6 05/12] tpm2-sessions: Add full HMAC and encrypt/decrypt session handling James Bottomley
2019-09-20 14:34   ` Jarkko Sakkinen
2019-09-20 14:35     ` Jarkko Sakkinen
2019-09-24 11:18       ` James Bottomley
2019-09-09 12:21 ` [PATCH v6 06/12] tpm-buf: add tpm_buf_parameters() James Bottomley
2019-09-09 12:22 ` [PATCH v6 07/12] tpm2: add hmac checks to tpm2_pcr_extend() James Bottomley
2019-09-09 12:22 ` [PATCH v6 08/12] tpm2: add session encryption protection to tpm2_get_random() James Bottomley
2019-09-09 12:23 ` [PATCH v6 09/12] trusted keys: Add session encryption protection to the seal/unseal path James Bottomley
2019-09-09 12:24 ` James Bottomley [this message]
2019-09-09 12:25 ` [PATCH v6 11/12] Documentation: add tpm-security.rst James Bottomley
2019-09-09 12:26 ` [PATCH v6 12/12] tpm2-sessions: NOT FOR COMMITTING add sessions testing James Bottomley
2019-09-10 16:21 ` [PATCH v6 00/12] add integrity and security to TPM2 transactions Jarkko Sakkinen
2019-09-10 16:29   ` James Bottomley
2019-09-11  8:42   ` Jarkko Sakkinen
2019-09-11  9:40     ` Jarkko Sakkinen

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