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Message-ID: <322eb81b-3f3e-e37e-5fb0-a37aad3d06d7@huawei.com>
Date: Mon, 17 Sep 2018 12:02:56 +0200
From: Roberto Sassu <roberto.sassu@...wei.com>
To: Jarkko Sakkinen <jarkko.sakkinen@...ux.intel.com>
CC: <linux-integrity@...r.kernel.org>,
<linux-security-module@...r.kernel.org>,
<linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2 3/3] tpm: retrieve digest size of unknown algorithms
with PCR read
On 9/16/2018 2:37 PM, Jarkko Sakkinen wrote:
> On Wed, Sep 05, 2018 at 01:42:02PM +0200, Roberto Sassu wrote:
>> Currently, the TPM driver retrieves the digest size from a table mapping
>> TPM algorithms identifiers to identifiers defined by the crypto subsystem.
>> If the algorithm is not defined by the latter, the digest size can be
>> retrieved from the output of the PCR read command.
>>
>> The patch retrieves at TPM startup the digest sizes for each PCR bank and
>> stores them in the new structure tpm_active_bank_info, member of tpm_chip,
>> so that the information can be passed to other kernel subsystems.
>>
>> tpm_active_bank_info contains: the TPM algorithm identifier, necessary to
>> generate the event log as defined by Trusted Computing Group (TCG); the
>> digest size, to pad/truncate a digest calculated with a different
>> algorithm; the crypto subsystem identifier, to calculate the digest of
>> event data.
>>
>> Signed-off-by: Roberto Sassu <roberto.sassu@...wei.com>
>> ---
>> drivers/char/tpm/tpm-interface.c | 11 +++++++---
>> drivers/char/tpm/tpm.h | 4 ++--
>> drivers/char/tpm/tpm2-cmd.c | 47 ++++++++++++++++++++++++++++++----------
>> include/linux/tpm.h | 6 +++++
>> 4 files changed, 51 insertions(+), 17 deletions(-)
>>
>> diff --git a/drivers/char/tpm/tpm-interface.c b/drivers/char/tpm/tpm-interface.c
>> index 81872880b5f1..02dcdcda5a3c 100644
>> --- a/drivers/char/tpm/tpm-interface.c
>> +++ b/drivers/char/tpm/tpm-interface.c
>> @@ -993,7 +993,7 @@ int tpm_pcr_read(struct tpm_chip *chip, int pcr_idx, u32 count,
>> if (!chip)
>> return -ENODEV;
>> if (chip->flags & TPM_CHIP_FLAG_TPM2)
>> - rc = tpm2_pcr_read(chip, pcr_idx, count, digests);
>> + rc = tpm2_pcr_read(chip, pcr_idx, count, digests, NULL);
>> else
>> rc = tpm_pcr_read_dev(chip, pcr_idx, digests[0].digest);
>> tpm_put_ops(chip);
>> @@ -1056,8 +1056,8 @@ int tpm_pcr_extend(struct tpm_chip *chip, int pcr_idx, const u8 *hash)
>> memset(digest_list, 0, sizeof(digest_list));
>>
>> for (i = 0; i < ARRAY_SIZE(chip->active_banks) &&
>> - chip->active_banks[i] != TPM_ALG_ERROR; i++) {
>> - digest_list[i].alg_id = chip->active_banks[i];
>> + chip->active_banks[i].alg_id != TPM_ALG_ERROR; i++) {
>> + digest_list[i].alg_id = chip->active_banks[i].alg_id;
>
> Why not just zero?
Hi Jarkko
sorry, I didn't understand this comment. Did you refer to the code
below (chip->active_banks[0] ...)?
>> memcpy(digest_list[i].digest, hash, TPM_DIGEST_SIZE);
>> count++;
>> }
>> @@ -1158,6 +1158,11 @@ int tpm1_auto_startup(struct tpm_chip *chip)
>> goto out;
>> }
>>
>> + chip->active_banks[0].alg_id = TPM_ALG_SHA1;
>> + chip->active_banks[0].digest_size = hash_digest_size[HASH_ALGO_SHA1];
>> + chip->active_banks[0].crypto_id = HASH_ALGO_SHA1;
>> + chip->active_banks[1].alg_id = TPM_ALG_ERROR;
>
> Then you could drop the last line here.
This code has the same behavior of tpm2_get_pcr_allocation(). If some
banks are not used, set the algorithm of the first unused to
TPM_ALG_ERROR.
>> +
>> return rc;
>> out:
>> if (rc > 0)
>> diff --git a/drivers/char/tpm/tpm.h b/drivers/char/tpm/tpm.h
>> index 9479e1ae1b4c..385843b49c17 100644
>> --- a/drivers/char/tpm/tpm.h
>> +++ b/drivers/char/tpm/tpm.h
>> @@ -237,7 +237,7 @@ struct tpm_chip {
>> const struct attribute_group *groups[3];
>> unsigned int groups_cnt;
>>
>> - u16 active_banks[7];
>> + struct tpm_active_bank_info active_banks[7];
>> #ifdef CONFIG_ACPI
>> acpi_handle acpi_dev_handle;
>> char ppi_version[TPM_PPI_VERSION_LEN + 1];
>> @@ -565,7 +565,7 @@ static inline u32 tpm2_rc_value(u32 rc)
>> }
>>
>> int tpm2_pcr_read(struct tpm_chip *chip, int pcr_idx, u32 count,
>> - struct tpm_digest *digests);
>> + struct tpm_digest *digests, u16 *sizes);
>> int tpm2_pcr_extend(struct tpm_chip *chip, int pcr_idx, u32 count,
>> struct tpm_digest *digests);
>> int tpm2_get_random(struct tpm_chip *chip, u8 *dest, size_t max);
>> diff --git a/drivers/char/tpm/tpm2-cmd.c b/drivers/char/tpm/tpm2-cmd.c
>> index 601d67c76c1e..51d2454c5329 100644
>> --- a/drivers/char/tpm/tpm2-cmd.c
>> +++ b/drivers/char/tpm/tpm2-cmd.c
>> @@ -181,11 +181,12 @@ struct tpm2_pcr_read_out {
>> * @pcr_idx: index of the PCR to read.
>> * @count: number of digests passed.
>> * @digests: list of pcr banks and buffers current PCR values are written to.
>> + * @sizes: list of digest sizes.
>> *
>> * Return: Same as with tpm_transmit_cmd.
>> */
>> int tpm2_pcr_read(struct tpm_chip *chip, int pcr_idx, u32 count,
>> - struct tpm_digest *digests)
>> + struct tpm_digest *digests, u16 *sizes)
>> {
>> int rc;
>> struct tpm_buf buf;
>> @@ -215,6 +216,9 @@ int tpm2_pcr_read(struct tpm_chip *chip, int pcr_idx, u32 count,
>> out = (struct tpm2_pcr_read_out *)&buf.data[TPM_HEADER_SIZE];
>> memcpy(digests[0].digest, out->digest,
>> be16_to_cpu(out->digest_size));
>> +
>> + if (sizes)
>> + sizes[0] = be16_to_cpu(out->digest_size);
>> }
>>
>> tpm_buf_destroy(&buf);
>> @@ -245,7 +249,6 @@ int tpm2_pcr_extend(struct tpm_chip *chip, int pcr_idx, u32 count,
>> struct tpm2_null_auth_area auth_area;
>> int rc;
>> int i;
>> - int j;
>>
>> if (count > ARRAY_SIZE(chip->active_banks))
>> return -EINVAL;
>> @@ -267,14 +270,9 @@ int tpm2_pcr_extend(struct tpm_chip *chip, int pcr_idx, u32 count,
>> tpm_buf_append_u32(&buf, count);
>>
>> for (i = 0; i < count; i++) {
>> - for (j = 0; j < ARRAY_SIZE(tpm2_hash_map); j++) {
>> - if (digests[i].alg_id != tpm2_hash_map[j].tpm_id)
>> - continue;
>> - tpm_buf_append_u16(&buf, digests[i].alg_id);
>> - tpm_buf_append(&buf, (const unsigned char
>> - *)&digests[i].digest,
>> - hash_digest_size[tpm2_hash_map[j].crypto_id]);
>> - }
>> + tpm_buf_append_u16(&buf, digests[i].alg_id);
>> + tpm_buf_append(&buf, (const unsigned char *)&digests[i].digest,
>> + chip->active_banks[i].digest_size);
>> }
>>
>> rc = tpm_transmit_cmd(chip, NULL, buf.data, PAGE_SIZE, 0, 0,
>> @@ -851,6 +849,26 @@ int tpm2_probe(struct tpm_chip *chip)
>> }
>> EXPORT_SYMBOL_GPL(tpm2_probe);
>>
>> +static int tpm2_init_active_bank_info(struct tpm_chip *chip,
>> + struct tpm_active_bank_info *active_bank)
>> +{
>> + struct tpm_digest digest = {.alg_id = active_bank->alg_id};
>> + int i;
>> +
>> + for (i = 0; i < ARRAY_SIZE(tpm2_hash_map); i++) {
>> + enum hash_algo crypto_algo = tpm2_hash_map[i].crypto_id;
>> +
>> + if (active_bank->alg_id != tpm2_hash_map[i].tpm_id)
>> + continue;
>> +
>> + active_bank->digest_size = hash_digest_size[crypto_algo];
>> + active_bank->crypto_id = crypto_algo;
>> + return 0;
>> + }
>> +
>> + return tpm2_pcr_read(chip, 0, 1, &digest, &active_bank->digest_size);
>> +}
>> +
>> struct tpm2_pcr_selection {
>> __be16 hash_alg;
>> u8 size_of_select;
>> @@ -905,7 +923,12 @@ static ssize_t tpm2_get_pcr_allocation(struct tpm_chip *chip)
>> }
>>
>> memcpy(&pcr_selection, marker, sizeof(pcr_selection));
>> - chip->active_banks[i] = be16_to_cpu(pcr_selection.hash_alg);
>> + chip->active_banks[i].alg_id =
>> + be16_to_cpu(pcr_selection.hash_alg);
>> + rc = tpm2_init_active_bank_info(chip, &chip->active_banks[i]);
>> + if (rc)
>> + break;
>> +
>> sizeof_pcr_selection = sizeof(pcr_selection.hash_alg) +
>> sizeof(pcr_selection.size_of_select) +
>> pcr_selection.size_of_select;
>> @@ -914,7 +937,7 @@ static ssize_t tpm2_get_pcr_allocation(struct tpm_chip *chip)
>>
>> out:
>> if (i < ARRAY_SIZE(chip->active_banks))
>> - chip->active_banks[i] = TPM_ALG_ERROR;
>> + chip->active_banks[i].alg_id = TPM_ALG_ERROR;
>>
>> tpm_buf_destroy(&buf);
>>
>> diff --git a/include/linux/tpm.h b/include/linux/tpm.h
>> index ac9fc47f4494..c8372ff582c3 100644
>> --- a/include/linux/tpm.h
>> +++ b/include/linux/tpm.h
>> @@ -46,6 +46,12 @@ struct tpm_digest {
>> u8 digest[SHA512_DIGEST_SIZE];
>> } __packed;
>>
>> +struct tpm_active_bank_info {
>> + u16 alg_id;
>> + u16 digest_size;
>> + u16 crypto_id;
>> +};
>
> Why not just tpm_bank_info? Will there be also tpm_inactive_bank_info
> at some point?
It derived from chip->active_banks. I will rename the structure.
Thanks
Roberto
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