[v5,1/2] tpm: add sysfs exports for all banks of PCR registers

Message ID	20210113232634.23242-2-James.Bottomley@HansenPartnership.com (mailing list archive)
State	New, archived
Headers	show Return-Path: <linux-integrity-owner@kernel.org> From: James Bottomley <James.Bottomley@HansenPartnership.com> To: linux-integrity@vger.kernel.org Cc: Mimi Zohar <zohar@linux.ibm.com>, Jarkko Sakkinen <jarkko@kernel.org>, linux-api@vger.kernel.org Subject: [PATCH v5 1/2] tpm: add sysfs exports for all banks of PCR registers Date: Wed, 13 Jan 2021 15:26:33 -0800 Message-Id: <20210113232634.23242-2-James.Bottomley@HansenPartnership.com> In-Reply-To: <20210113232634.23242-1-James.Bottomley@HansenPartnership.com> References: <20210113232634.23242-1-James.Bottomley@HansenPartnership.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Precedence: bulk
Series	add sysfs exports for TPM 2 PCR registers \| expand [v5,0/2] add sysfs exports for TPM 2 PCR registers [v5,1/2] tpm: add sysfs exports for all banks of PCR registers [v5,2/2] ABI: add sysfs description for tpm exports of PCR registers

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;

[v5,1/2] tpm: add sysfs exports for all banks of PCR registers

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