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tpm: add sysfs exports for all banks of PCR registers 

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@HansenPartnership.com>
Reviewed-by: Jerry Snitselaar <jsnitsel@redhat.com>
Tested-by: Thiago Jung Bauermann <bauerman@linux.ibm.com>
Tested-by: Jarkko Sakkinen <jarkko@kernel.org>
Reviewed-by: Jarkko Sakkinen <jarkko@kernel.org>
Signed-off-by: Jarkko Sakkinen <jarkko@kernel.org>
This commit is contained in:
James Bottomley 2021-01-13 15:26:33 -08:00 committed by Jarkko Sakkinen
parent 40d32b59e3
commit aab73d9524
2 changed files with 187 additions and 1 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

179
drivers/char/tpm/tpm-sysfs.c
View File

@ -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);
}

9
include/linux/tpm.h
View File

@ -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;