Create sysfs per hash groups with 24 PCR files in them one group,
named pcr-<hash>, for each agile hash of the TPM. The files are
plugged in to a PCR read function which is TPM version agnostic, so
this works also for TPM 1.2 but the hash is only sha1 in that case.
Note: the macros used to create the hashes emit spurious checkpatch
warnings. Do not try to "fix" them as checkpatch recommends, otherwise
they'll break.
Signed-off-by: James Bottomley <James.Bottomley@xxxxxxxxxxxxxxxxxxxxx>
Reviewed-by: Jerry Snitselaar <jsnitsel@xxxxxxxxxx>
Tested-by: Thiago Jung Bauermann <bauerman@xxxxxxxxxxxxx>
---
v2: fix TPM 1.2 legacy links failure
v3: fix warn on and add note to tpm_algorithms
v4: reword commit and add tested-by
v5: algorithm spelling fix WARN->dev_err
---
drivers/char/tpm/tpm-sysfs.c | 179 +++++++++++++++++++++++++++++++++++
include/linux/tpm.h | 9 +-
2 files changed, 187 insertions(+), 1 deletion(-)
diff --git a/drivers/char/tpm/tpm-sysfs.c b/drivers/char/tpm/tpm-sysfs.c
index e2ff0b273a0f..63f03cfb8e6a 100644
--- a/drivers/char/tpm/tpm-sysfs.c
+++ b/drivers/char/tpm/tpm-sysfs.c
@@ -337,11 +337,190 @@ static const struct attribute_group tpm2_dev_group = {
.attrs = tpm2_dev_attrs,
};
+struct tpm_pcr_attr {
+ int alg_id;
+ int pcr;
+ struct device_attribute attr;
+};
+
+#define to_tpm_pcr_attr(a) container_of(a, struct tpm_pcr_attr, attr)
+
+static ssize_t pcr_value_show(struct device *dev,
+ struct device_attribute *attr,
+ char *buf)
+{
+ struct tpm_pcr_attr *ha = to_tpm_pcr_attr(attr);
+ struct tpm_chip *chip = to_tpm_chip(dev);
+ struct tpm_digest digest;
+ int i;
+ int digest_size = 0;
+ int rc;
+ char *str = buf;
+
+ for (i = 0; i < chip->nr_allocated_banks; i++)
+ if (ha->alg_id == chip->allocated_banks[i].alg_id)
+ digest_size = chip->allocated_banks[i].digest_size;
+ /* should never happen */
+ if (!digest_size)
+ return -EINVAL;
+
+ digest.alg_id = ha->alg_id;
+ rc = tpm_pcr_read(chip, ha->pcr, &digest);
+ if (rc)
+ return rc;
+ for (i = 0; i < digest_size; i++)
+ str += sprintf(str, "%02X", digest.digest[i]);
+ str += sprintf(str, "\n");
+
+ return str - buf;
+}
+
+/*
+ * The following set of defines represents all the magic to build
+ * the per hash attribute groups for displaying each bank of PCRs.
+ * The only slight problem with this approach is that every PCR is
+ * hard coded to be present, so you don't know if an PCR is missing
+ * until a cat of the file returns -EINVAL
+ *
+ * Also note you must ignore checkpatch warnings in this macro
+ * code. This is deep macro magic that checkpatch.pl doesn't
+ * understand.
+ */
+
+/* Note, this must match TPM2_PLATFORM_PCR which is fixed at 24. */
+#define _TPM_HELPER(_alg, _hash, F) \
+ F(_alg, _hash, 0) \
+ F(_alg, _hash, 1) \
+ F(_alg, _hash, 2) \
+ F(_alg, _hash, 3) \
+ F(_alg, _hash, 4) \
+ F(_alg, _hash, 5) \
+ F(_alg, _hash, 6) \
+ F(_alg, _hash, 7) \
+ F(_alg, _hash, 8) \
+ F(_alg, _hash, 9) \
+ F(_alg, _hash, 10) \
+ F(_alg, _hash, 11) \
+ F(_alg, _hash, 12) \
+ F(_alg, _hash, 13) \
+ F(_alg, _hash, 14) \
+ F(_alg, _hash, 15) \
+ F(_alg, _hash, 16) \
+ F(_alg, _hash, 17) \
+ F(_alg, _hash, 18) \
+ F(_alg, _hash, 19) \
+ F(_alg, _hash, 20) \
+ F(_alg, _hash, 21) \
+ F(_alg, _hash, 22) \
+ F(_alg, _hash, 23)
+
+/* ignore checkpatch warning about trailing ; in macro. */
+#define PCR_ATTR(_alg, _hash, _pcr) \
+ static struct tpm_pcr_attr dev_attr_pcr_##_hash##_##_pcr = { \
+ .alg_id = _alg, \
+ .pcr = _pcr, \
+ .attr = { \
+ .attr = { \
+ .name = __stringify(_pcr), \
+ .mode = 0444 \
+ }, \
+ .show = pcr_value_show \
+ } \
+ };
+
+#define PCR_ATTRS(_alg, _hash) \
+ _TPM_HELPER(_alg, _hash, PCR_ATTR)
+
+/* ignore checkpatch warning about trailing , in macro. */
+#define PCR_ATTR_VAL(_alg, _hash, _pcr) \
+ &dev_attr_pcr_##_hash##_##_pcr.attr.attr,
+
+#define PCR_ATTR_GROUP_ARRAY(_alg, _hash) \
+ static struct attribute *pcr_group_attrs_##_hash[] = { \
+ _TPM_HELPER(_alg, _hash, PCR_ATTR_VAL) \
+ NULL \
+ }
+
+#define PCR_ATTR_GROUP(_alg, _hash) \
+ static struct attribute_group pcr_group_##_hash = { \
+ .name = "pcr-" __stringify(_hash), \
+ .attrs = pcr_group_attrs_##_hash \
+ }
+
+#define PCR_ATTR_BUILD(_alg, _hash) \
+ PCR_ATTRS(_alg, _hash) \
+ PCR_ATTR_GROUP_ARRAY(_alg, _hash); \
+ PCR_ATTR_GROUP(_alg, _hash)
+/*
+ * End of macro structure to build an attribute group containing 24
+ * PCR value files for each supported hash algorithm
+ */
+
+/*
+ * The next set of macros implements the cleverness for each hash to
+ * build a static attribute group called pcr_group_<hash> which can be
+ * added to chip->groups[].
+ *
+ * The first argument is the TPM algorithm id and the second is the
+ * hash used as both the suffix and the group name. Note: the group
+ * name is a directory in the top level tpm class with the name
+ * pcr-<hash>, so it must not clash with any other names already
+ * in the sysfs directory.
+ */
+PCR_ATTR_BUILD(TPM_ALG_SHA1, sha1);
+PCR_ATTR_BUILD(TPM_ALG_SHA256, sha256);
+PCR_ATTR_BUILD(TPM_ALG_SHA384, sha384);
+PCR_ATTR_BUILD(TPM_ALG_SHA512, sha512);
+PCR_ATTR_BUILD(TPM_ALG_SM3_256, sm3);
+
+
void tpm_sysfs_add_device(struct tpm_chip *chip)
{
+ int i;
+
WARN_ON(chip->groups_cnt != 0);
+
if (chip->flags & TPM_CHIP_FLAG_TPM2)
chip->groups[chip->groups_cnt++] = &tpm2_dev_group;
else
chip->groups[chip->groups_cnt++] = &tpm1_dev_group;
+
+ /* add one group for each bank hash */
+ for (i = 0; i < chip->nr_allocated_banks; i++) {
+ switch (chip->allocated_banks[i].alg_id) {
+ case TPM_ALG_SHA1:
+ chip->groups[chip->groups_cnt++] = &pcr_group_sha1;
+ break;
+ case TPM_ALG_SHA256:
+ chip->groups[chip->groups_cnt++] = &pcr_group_sha256;
+ break;
+ case TPM_ALG_SHA384:
+ chip->groups[chip->groups_cnt++] = &pcr_group_sha384;
+ break;
+ case TPM_ALG_SHA512:
+ chip->groups[chip->groups_cnt++] = &pcr_group_sha512;
+ break;
+ case TPM_ALG_SM3_256:
+ chip->groups[chip->groups_cnt++] = &pcr_group_sm3;
+ break;
+ default:
+ /*
+ * If triggers, send a patch to add both a
+ * PCR_ATTR_BUILD() macro above for the
+ * missing algorithm as well as an additional
+ * case in this switch statement.
+ */
+ dev_err(&chip->dev,
+ "TPM with unsupported bank algorithm 0x%04x",
+ chip->allocated_banks[i].alg_id);
+ break;
+ }
+ }
+
+ /*
+ * This will only trigger if someone has added an additional
+ * hash to the tpm_algorithms enum without incrementing
+ * TPM_MAX_HASHES.
+ */
+ WARN_ON(chip->groups_cnt > TPM_MAX_HASHES + 1);
}
diff --git a/include/linux/tpm.h b/include/linux/tpm.h
index df56d7fbe78f..c4ca52138e8b 100644
--- a/include/linux/tpm.h
+++ b/include/linux/tpm.h
@@ -31,6 +31,7 @@ struct tpm_chip;
struct trusted_key_payload;
struct trusted_key_options;
+/* if you add a new hash to this, increment TPM_MAX_HASHES below */
enum tpm_algorithms {
TPM_ALG_ERROR = 0x0000,
TPM_ALG_SHA1 = 0x0004,
@@ -42,6 +43,12 @@ enum tpm_algorithms {
TPM_ALG_SM3_256 = 0x0012,
};
+/*
+ * maximum number of hashing algorithms a TPM can have. This is
+ * basically a count of every hash in tpm_algorithms above
+ */
+#define TPM_MAX_HASHES 5
+
struct tpm_digest {
u16 alg_id;
u8 digest[TPM_MAX_DIGEST_SIZE];
@@ -146,7 +153,7 @@ struct tpm_chip {
struct dentry *bios_dir[TPM_NUM_EVENT_LOG_FILES];
- const struct attribute_group *groups[3];
+ const struct attribute_group *groups[3 + TPM_MAX_HASHES];
unsigned int groups_cnt;
u32 nr_allocated_banks;
--
2.26.2
