Re: [PATCH v5 7/7] tpm: pass an array of tpm_bank_list structures to tpm_pcr_extend()

From: Jarkko Sakkinen
Date: Fri Nov 16 2018 - 10:04:00 EST

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On Wed, Nov 14, 2018 at 04:31:08PM +0100, Roberto Sassu wrote:
> Currently, tpm_pcr_extend() accepts as an input only a SHA1 digest.
>
> This patch modifies the definition of tpm_pcr_extend() to allow other
> kernel subsystems to pass a digest for each algorithm supported by the TPM.
> All digests are processed by the TPM in one operation.
>
> If a tpm_pcr_extend() caller provides a subset of the supported algorithms,
> the TPM driver extends the remaining PCR banks with the first digest
> passed as an argument to the function.

What is the legit use case for this?

> The new tpm_bank_list structure has been preferred to the tpm_digest
> structure, to let the caller specify the size of the digest (which may be
> unknown to the TPM driver).
>
> Due to the API change, ima_pcr_extend() and pcrlock() have been modified.
>
> Signed-off-by: Roberto Sassu <roberto.sassu@xxxxxxxxxx>

Should be dropped from the patch set as it is not taken advatange of
but I can still try to give some feedback.

> ---
> drivers/char/tpm/tpm-interface.c | 24 +++++---------------
> drivers/char/tpm/tpm.h | 6 ++---
> drivers/char/tpm/tpm1-cmd.c | 14 ++++++++----
> drivers/char/tpm/tpm2-cmd.c | 36 +++++++++++++++++++++---------
> include/linux/tpm.h | 13 ++++++++---
> security/integrity/ima/ima_queue.c | 5 ++++-
> security/keys/trusted.c | 5 ++++-
> 7 files changed, 63 insertions(+), 40 deletions(-)
>
> diff --git a/drivers/char/tpm/tpm-interface.c b/drivers/char/tpm/tpm-interface.c
> index f0e1456440d7..5495223d3f7b 100644
> --- a/drivers/char/tpm/tpm-interface.c
> +++ b/drivers/char/tpm/tpm-interface.c
> @@ -478,42 +478,30 @@ EXPORT_SYMBOL_GPL(tpm_pcr_read);
> * tpm_pcr_extend - extend a PCR value in SHA1 bank.
> * @chip: a &struct tpm_chip instance, %NULL for the default chip
> * @pcr_idx: the PCR to be retrieved
> - * @hash: the hash value used to extend the PCR value
> + * @count: number of tpm_bank_list structures
> + * @bank_list: array of tpm_bank_list structures used to extend the PCR value
> *
> * Note: with TPM 2.0 extends also those banks for which no digest was
> * specified in order to prevent malicious use of those PCR banks.
> *
> * Return: same as with tpm_transmit_cmd()
> */
> -int tpm_pcr_extend(struct tpm_chip *chip, u32 pcr_idx, const u8 *hash)
> +int tpm_pcr_extend(struct tpm_chip *chip, u32 pcr_idx, u32 count,
> + const struct tpm_bank_list *bank_list)
> {
> int rc;
> - struct tpm_digest *digest_list;
> - int i;
>
> chip = tpm_find_get_ops(chip);
> if (!chip)
> return -ENODEV;
>
> if (chip->flags & TPM_CHIP_FLAG_TPM2) {
> - digest_list = kcalloc(chip->nr_allocated_banks,
> - sizeof(*digest_list), GFP_KERNEL);
> - if (!digest_list)
> - return -ENOMEM;
> -
> - for (i = 0; i < chip->nr_allocated_banks; i++) {
> - digest_list[i].alg_id = chip->allocated_banks[i].alg_id;
> - memcpy(digest_list[i].digest, hash, TPM_DIGEST_SIZE);
> - }
> -
> - rc = tpm2_pcr_extend(chip, pcr_idx, chip->nr_allocated_banks,
> - digest_list);
> - kfree(digest_list);
> + rc = tpm2_pcr_extend(chip, pcr_idx, count, bank_list);
> tpm_put_ops(chip);
> return rc;
> }
>
> - rc = tpm1_pcr_extend(chip, pcr_idx, hash,
> + rc = tpm1_pcr_extend(chip, pcr_idx, count, bank_list,
> "attempting extend a PCR value");
> tpm_put_ops(chip);
> return rc;
> diff --git a/drivers/char/tpm/tpm.h b/drivers/char/tpm/tpm.h
> index 023ddf42038b..4296c720ebb4 100644
> --- a/drivers/char/tpm/tpm.h
> +++ b/drivers/char/tpm/tpm.h
> @@ -504,8 +504,8 @@ int tpm1_auto_startup(struct tpm_chip *chip);
> int tpm1_do_selftest(struct tpm_chip *chip);
> int tpm1_get_timeouts(struct tpm_chip *chip);
> unsigned long tpm1_calc_ordinal_duration(struct tpm_chip *chip, u32 ordinal);
> -int tpm1_pcr_extend(struct tpm_chip *chip, u32 pcr_idx, const u8 *hash,
> - const char *log_msg);
> +int tpm1_pcr_extend(struct tpm_chip *chip, u32 pcr_idx, u32 count,
> + const struct tpm_bank_list *bank_list, const char *log_msg);
> int tpm1_pcr_read(struct tpm_chip *chip, u32 pcr_idx, u8 *res_buf);
> ssize_t tpm1_getcap(struct tpm_chip *chip, u32 subcap_id, cap_t *cap,
> const char *desc, size_t min_cap_length);
> @@ -551,7 +551,7 @@ int tpm2_get_timeouts(struct tpm_chip *chip);
> int tpm2_pcr_read(struct tpm_chip *chip, u32 pcr_idx,
> struct tpm_digest *digest_struct, u16 *digest_size_ptr);
> int tpm2_pcr_extend(struct tpm_chip *chip, u32 pcr_idx, u32 count,
> - struct tpm_digest *digests);
> + const struct tpm_bank_list *bank_list);
> int tpm2_get_random(struct tpm_chip *chip, u8 *dest, size_t max);
> void tpm2_flush_context_cmd(struct tpm_chip *chip, u32 handle,
> unsigned int flags);
> diff --git a/drivers/char/tpm/tpm1-cmd.c b/drivers/char/tpm/tpm1-cmd.c
> index 8b70a7f884a7..439ac749517c 100644
> --- a/drivers/char/tpm/tpm1-cmd.c
> +++ b/drivers/char/tpm/tpm1-cmd.c
> @@ -449,12 +449,19 @@ int tpm1_get_timeouts(struct tpm_chip *chip)
> }
>
> #define TPM_ORD_PCR_EXTEND 20
> -int tpm1_pcr_extend(struct tpm_chip *chip, u32 pcr_idx, const u8 *hash,
> - const char *log_msg)
> +int tpm1_pcr_extend(struct tpm_chip *chip, u32 pcr_idx, u32 count,
> + const struct tpm_bank_list *bank_list, const char *log_msg)
> {
> struct tpm_buf buf;
> + u8 dummy_hash[TPM_DIGEST_SIZE] = { 0 };
> + const u8 *hash;
> int rc;
>
> + hash = dummy_hash;
> + if (count)
> + memcpy(dummy_hash, bank_list[0].extend_array,
> + min(bank_list[0].digest_size, (u16)sizeof(dummy_hash)));
> +
> rc = tpm_buf_init(&buf, TPM_TAG_RQU_COMMAND, TPM_ORD_PCR_EXTEND);

This is probably mistake? I mean dummy_hash is not used.

> if (rc)
> return rc;
> @@ -743,7 +750,6 @@ int tpm1_auto_startup(struct tpm_chip *chip)
> */
> int tpm1_pm_suspend(struct tpm_chip *chip, u32 tpm_suspend_pcr)
> {
> - u8 dummy_hash[TPM_DIGEST_SIZE] = { 0 };
> struct tpm_buf buf;
> unsigned int try;
> int rc;
> @@ -751,7 +757,7 @@ int tpm1_pm_suspend(struct tpm_chip *chip, u32 tpm_suspend_pcr)
>
> /* for buggy tpm, flush pcrs with extend to selected dummy */
> if (tpm_suspend_pcr)
> - rc = tpm1_pcr_extend(chip, tpm_suspend_pcr, dummy_hash,
> + rc = tpm1_pcr_extend(chip, tpm_suspend_pcr, 0, NULL,
> "extending dummy pcr before suspend");
>
> rc = tpm_buf_init(&buf, TPM_TAG_RQU_COMMAND, TPM_ORD_SAVESTATE);
> diff --git a/drivers/char/tpm/tpm2-cmd.c b/drivers/char/tpm/tpm2-cmd.c
> index 974465f04b78..40eb1a044451 100644
> --- a/drivers/char/tpm/tpm2-cmd.c
> +++ b/drivers/char/tpm/tpm2-cmd.c
> @@ -248,21 +248,22 @@ struct tpm2_null_auth_area {
> *
> * @chip: TPM chip to use.
> * @pcr_idx: index of the PCR.
> - * @count: number of digests passed.
> - * @digests: list of pcr banks and corresponding digest values to extend.
> + * @count: number of tpm_bank_list passed.
> + * @bank_list: array of tpm_bank_list with digest values to extend.
> *
> * Return: Same as with tpm_transmit_cmd.
> */
> int tpm2_pcr_extend(struct tpm_chip *chip, u32 pcr_idx, u32 count,
> - struct tpm_digest *digests)
> + const struct tpm_bank_list *bank_list)
> {
> struct tpm_buf buf;
> struct tpm2_null_auth_area auth_area;
> + const struct tpm_bank_list *item;
> + u8 dummy_hash[SHA512_DIGEST_SIZE] = { 0 };
> + const u8 *hash;
> int rc;
> int i;
> -
> - if (count > chip->nr_allocated_banks)
> - return -EINVAL;
> + int j;
>
> rc = tpm_buf_init(&buf, TPM2_ST_SESSIONS, TPM2_CC_PCR_EXTEND);
> if (rc)
> @@ -278,11 +279,26 @@ int tpm2_pcr_extend(struct tpm_chip *chip, u32 pcr_idx, u32 count,
> tpm_buf_append_u32(&buf, sizeof(struct tpm2_null_auth_area));
> tpm_buf_append(&buf, (const unsigned char *)&auth_area,
> sizeof(auth_area));
> - tpm_buf_append_u32(&buf, count);
> + tpm_buf_append_u32(&buf, chip->nr_allocated_banks);
> +
> + if (count)
> + memcpy(dummy_hash, bank_list[0].extend_array,
> + bank_list[0].digest_size);
> +
> + for (i = 0; i < chip->nr_allocated_banks; i++) {
> + tpm_buf_append_u16(&buf, chip->allocated_banks[i].alg_id);
> +
> + hash = dummy_hash;
> + for (j = 0; j < count; j++) {
> + item = bank_list + j;
> +
> + if (item->alg_id == chip->allocated_banks[i].alg_id) {
> + hash = item->extend_array;
> + break;
> + }
> + }
>
> - for (i = 0; i < count; i++) {
> - tpm_buf_append_u16(&buf, digests[i].alg_id);
> - tpm_buf_append(&buf, (const unsigned char *)&digests[i].digest,
> + tpm_buf_append(&buf, hash,
> chip->allocated_banks[i].digest_size);
> }
>
> diff --git a/include/linux/tpm.h b/include/linux/tpm.h
> index fcdd33ae9969..16e5ff1f0294 100644
> --- a/include/linux/tpm.h
> +++ b/include/linux/tpm.h
> @@ -52,6 +52,12 @@ struct tpm_bank_info {
> u16 crypto_id;
> };
>
> +struct tpm_bank_list {
> + u8 alg_id;
> + u16 digest_size;
> + const u8 *extend_array;
> +};

You should document this structure.

> +
> enum TPM_OPS_FLAGS {
> TPM_OPS_AUTO_STARTUP = BIT(0),
> };
> @@ -79,7 +85,8 @@ struct tpm_class_ops {
> extern int tpm_is_tpm2(struct tpm_chip *chip);
> extern int tpm_pcr_read(struct tpm_chip *chip, u32 pcr_idx,
> struct tpm_digest *digest_struct);
> -extern int tpm_pcr_extend(struct tpm_chip *chip, u32 pcr_idx, const u8 *hash);
> +extern int tpm_pcr_extend(struct tpm_chip *chip, u32 pcr_idx, u32 count,
> + const struct tpm_bank_list *bank_list);
> extern int tpm_send(struct tpm_chip *chip, void *cmd, size_t buflen);
> extern int tpm_get_random(struct tpm_chip *chip, u8 *data, size_t max);
> extern int tpm_seal_trusted(struct tpm_chip *chip,
> @@ -101,8 +108,8 @@ static inline int tpm_pcr_read(struct tpm_chip *chip, int pcr_idx,
> return -ENODEV;
> }
>
> -static inline int tpm_pcr_extend(struct tpm_chip *chip, u32 pcr_idx,
> - const u8 *hash)
> +static inline int tpm_pcr_extend(struct tpm_chip *chip, u32 pcr_idx, u32 count,
> + const struct tpm_bank_list *bank_list)
> {
> return -ENODEV;
> }
> diff --git a/security/integrity/ima/ima_queue.c b/security/integrity/ima/ima_queue.c
> index b186819bd5aa..24024edef316 100644
> --- a/security/integrity/ima/ima_queue.c
> +++ b/security/integrity/ima/ima_queue.c
> @@ -140,12 +140,15 @@ unsigned long ima_get_binary_runtime_size(void)
>
> static int ima_pcr_extend(const u8 *hash, int pcr)
> {
> + struct tpm_bank_list bank_item = { .alg_id = TPM_ALG_SHA1,
> + .digest_size = TPM_DIGEST_SIZE,
> + .extend_array = hash };

Item is a list?

> int result = 0;
>
> if (!ima_tpm_chip)
> return result;
>
> - result = tpm_pcr_extend(ima_tpm_chip, pcr, hash);
> + result = tpm_pcr_extend(ima_tpm_chip, pcr, 1, &bank_item);
> if (result != 0)
> pr_err("Error Communicating to TPM chip, result: %d\n", result);
> return result;
> diff --git a/security/keys/trusted.c b/security/keys/trusted.c
> index ff6789365a12..d2a3129a95f9 100644
> --- a/security/keys/trusted.c
> +++ b/security/keys/trusted.c
> @@ -380,6 +380,9 @@ EXPORT_SYMBOL_GPL(trusted_tpm_send);
> static int pcrlock(const int pcrnum)
> {
> unsigned char hash[SHA1_DIGEST_SIZE];
> + struct tpm_bank_list bank_item = { .alg_id = TPM_ALG_SHA1,
> + .digest_size = sizeof(hash),
> + .extend_array = hash }
> int ret;
>
> if (!capable(CAP_SYS_ADMIN))
> @@ -387,7 +390,7 @@ static int pcrlock(const int pcrnum)
> ret = tpm_get_random(NULL, hash, SHA1_DIGEST_SIZE);
> if (ret != SHA1_DIGEST_SIZE)
> return ret;
> - return tpm_pcr_extend(NULL, pcrnum, hash) ? -EINVAL : 0;
> + return tpm_pcr_extend(NULL, pcrnum, 1, &bank_item) ? -EINVAL : 0;
> }
>
> /*
> --
> 2.17.1
>

/Jarkko

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