On Thu Oct 24 19, Mimi Zohar wrote:
On Thu, 2019-10-24 at 14:38 -0700, Jerry Snitselaar wrote:
On Thu Oct 24 19, Jarkko Sakkinen wrote:
>On Thu, Oct 24, 2019 at 02:18:48PM +0200, Petr Vorel wrote:
>> Hi all,
>>
>> I wonder what to do with this patch "ima: skip verifying TPM 2.0 PCR values" [1].
>> Is it a correct way to differentiate between TPM 1.2 and TPM 2.0?
>> Or something else should be applied?
>>
>> How is the work on TPM 2.0 Linux sysfs interface?
>> But even it's done in near future, we'd still need some way for older kernels.
>>
>> Kind regards,
>> Petr
>>
>> [1] https://patchwork.ozlabs.org/patch/1100733/
>
>version_major sysfs file would be acceptable if someone wants to proceed
>and send such patch.
>
>Also replicants for durations and timeouts files would make sense for
>TPM 2.0.
>
>/Jarkko
Is it as simple as doing this?
diff --git a/drivers/char/tpm/tpm-sysfs.c b/drivers/char/tpm/tpm-sysfs.c
index edfa89160010..fd8eb8d8945c 100644
--- a/drivers/char/tpm/tpm-sysfs.c
+++ b/drivers/char/tpm/tpm-sysfs.c
@@ -309,7 +309,17 @@ static ssize_t timeouts_show(struct device *dev, struct device_attribute *attr,
}
static DEVICE_ATTR_RO(timeouts);
-static struct attribute *tpm_dev_attrs[] = {
+static ssize_t version_major_show(struct device *dev,
+ struct device_attribute *attr, char *buf)
+{
+ struct tpm_chip *chip = to_tpm_chip(dev);
+
+ return sprintf(buf, "TPM%s\n", chip->flags & TPM_CHIP_FLAG_TPM2
+ ? "2.0" : "1.2");
+}
+static DEVICE_ATTR_RO(version_major);
+
+static struct attribute *tpm12_dev_attrs[] = {
&dev_attr_pubek.attr,
&dev_attr_pcrs.attr,
&dev_attr_enabled.attr,
@@ -320,18 +330,28 @@ static struct attribute *tpm_dev_attrs[] = {
&dev_attr_cancel.attr,
&dev_attr_durations.attr,
&dev_attr_timeouts.attr,
+ &dev_attr_version_major.attr,
NULL,
};
The TPM version seems to be included in "dev_attr_caps.attr".
-static const struct attribute_group tpm_dev_group = {
- .attrs = tpm_dev_attrs,
+static struct attribute *tpm20_dev_attrs[] = {
+ &dev_attr_version_major.attr,
+ NULL
+};
This should work, but wouldn't exporting this information under
security/tpmX, like the binary_bios_measurements, be a lot easier to
find and use?
Mimi
/sys/kernel/security/tpmX/major_version (on fedora and rhel at least, is it elsewhere on other distros?)
versus
/sys/class/tpm/tpmX/major_version
I don't know that it is any easier to find.
+
+static const struct attribute_group tpm12_dev_group = {
+ .attrs = tpm12_dev_attrs,
+};
+
+static const struct attribute_group tpm20_dev_group = {
+ .attrs = tpm20_dev_attrs,
};
void tpm_sysfs_add_device(struct tpm_chip *chip)
{
- if (chip->flags & TPM_CHIP_FLAG_TPM2)
- return;
-
WARN_ON(chip->groups_cnt != 0);
- chip->groups[chip->groups_cnt++] = &tpm_dev_group;
+ if (chip->flags & TPM_CHIP_FLAG_TPM2)
+ chip->groups[chip->groups_cnt++] = &tpm20_dev_group;
+ else
+ chip->groups[chip->groups_cnt++] = &tpm12_dev_group;
}
Did a quick test on 2 systems here.
