Re: [PATCH v3 2/2] tpm: enhance TPM 2.0 PCR extend to support multiple banks

From: Jarkko Sakkinen
Date: Thu Jan 12 2017 - 13:21:16 EST

On Thu, Jan 12, 2017 at 11:58:10AM -0500, Nayna Jain wrote:
> The current TPM 2.0 device driver extends only the SHA1 PCR bank
> but the TCG Specification[1] recommends extending all active PCR
> banks, to prevent malicious users from setting unused PCR banks with
> fake measurements and quoting them.
>
> The existing in-kernel interface(tpm_pcr_extend()) expects only a
> SHA1 digest. To extend all active PCR banks with differing
> digest sizes, the SHA1 digest is padded with trailing 0's as needed.
>
> [1] TPM 2.0 Specification referred here is "TCG PC Client Specific
> Platform Firmware Profile for TPM 2.0"
>
> Signed-off-by: Nayna Jain <nayna@xxxxxxxxxxxxxxxxxx>
> ---
> drivers/char/tpm/Kconfig | 1 +
> drivers/char/tpm/tpm-interface.c | 16 +++++++++-
> drivers/char/tpm/tpm.h | 3 +-
> drivers/char/tpm/tpm2-cmd.c | 68 +++++++++++++++++++++++-----------------
> drivers/char/tpm/tpm_eventlog.h | 18 +++++++++++
> 5 files changed, 75 insertions(+), 31 deletions(-)
>
> diff --git a/drivers/char/tpm/Kconfig b/drivers/char/tpm/Kconfig
> index 277186d..af985cc 100644
> --- a/drivers/char/tpm/Kconfig
> +++ b/drivers/char/tpm/Kconfig
> @@ -6,6 +6,7 @@ menuconfig TCG_TPM
> tristate "TPM Hardware Support"
> depends on HAS_IOMEM
> select SECURITYFS
> + select CRYPTO_HASH_INFO

In the commit message you did not mention this.

> ---help---
> If you have a TPM security chip in your system, which
> implements the Trusted Computing Group's specification,
> diff --git a/drivers/char/tpm/tpm-interface.c b/drivers/char/tpm/tpm-interface.c
> index fecdd3f..e037dd2 100644
> --- a/drivers/char/tpm/tpm-interface.c
> +++ b/drivers/char/tpm/tpm-interface.c
> @@ -7,6 +7,7 @@
> * Dave Safford <safford@xxxxxxxxxxxxxx>
> * Reiner Sailer <sailer@xxxxxxxxxxxxxx>
> * Kylene Hall <kjhall@xxxxxxxxxx>
> + * Nayna Jain <nayna@xxxxxxxxxxxxxxxxxx>

Remove.

> *
> * Maintained by: <tpmdd-devel@xxxxxxxxxxxxxxxxxxxxx>
> *
> @@ -759,6 +760,7 @@ static const struct tpm_input_header pcrextend_header = {
> int tpm_pcr_extend(u32 chip_num, int pcr_idx, const u8 *hash)
> {
> struct tpm_cmd_t cmd;
> + int i;
> int rc;
> struct tpm_chip *chip;
>
> @@ -767,7 +769,19 @@ int tpm_pcr_extend(u32 chip_num, int pcr_idx, const u8 *hash)
> return -ENODEV;
>
> if (chip->flags & TPM_CHIP_FLAG_TPM2) {
> - rc = tpm2_pcr_extend(chip, pcr_idx, hash);
> + struct tpml_digest_values d_values;
> +
> + memset(&d_values, 0, sizeof(d_values));
> +
> + for (i = 0; (chip->active_banks[i] != 0) &&
> + (i < ARRAY_SIZE(chip->active_banks)); i++) {
> + d_values.digests[i].alg_id = chip->active_banks[i];
> + memcpy(d_values.digests[i].digest, hash,
> + TPM_DIGEST_SIZE);
> + d_values.count++;
> + }
> +
> + rc = tpm2_pcr_extend(chip, pcr_idx, &d_values);
> tpm_put_ops(chip);
> return rc;
> }
> diff --git a/drivers/char/tpm/tpm.h b/drivers/char/tpm/tpm.h
> index dddd573..dd82d58 100644
> --- a/drivers/char/tpm/tpm.h
> +++ b/drivers/char/tpm/tpm.h
> @@ -533,7 +533,8 @@ static inline void tpm_add_ppi(struct tpm_chip *chip)
> #endif
>
> int tpm2_pcr_read(struct tpm_chip *chip, int pcr_idx, u8 *res_buf);
> -int tpm2_pcr_extend(struct tpm_chip *chip, int pcr_idx, const u8 *hash);
> +int tpm2_pcr_extend(struct tpm_chip *chip, int pcr_idx,
> + struct tpml_digest_values *digests);
> int tpm2_get_random(struct tpm_chip *chip, u8 *out, size_t max);
> int tpm2_seal_trusted(struct tpm_chip *chip,
> struct trusted_key_payload *payload,
> diff --git a/drivers/char/tpm/tpm2-cmd.c b/drivers/char/tpm/tpm2-cmd.c
> index 87388921..5027a54 100644
> --- a/drivers/char/tpm/tpm2-cmd.c
> +++ b/drivers/char/tpm/tpm2-cmd.c
> @@ -64,9 +64,7 @@ struct tpm2_pcr_extend_in {
> __be32 pcr_idx;
> __be32 auth_area_size;
> struct tpm2_null_auth_area auth_area;
> - __be32 digest_cnt;
> - __be16 hash_alg;
> - u8 digest[TPM_DIGEST_SIZE];
> + struct tpml_digest_values digests;
> } __packed;
>
> struct tpm2_get_tpm_pt_in {
> @@ -296,46 +294,58 @@ int tpm2_pcr_read(struct tpm_chip *chip, int pcr_idx, u8 *res_buf)
> return rc;
> }
>
> -#define TPM2_GET_PCREXTEND_IN_SIZE \
> - (sizeof(struct tpm_input_header) + \
> - sizeof(struct tpm2_pcr_extend_in))
> -
> -static const struct tpm_input_header tpm2_pcrextend_header = {
> - .tag = cpu_to_be16(TPM2_ST_SESSIONS),
> - .length = cpu_to_be32(TPM2_GET_PCREXTEND_IN_SIZE),
> - .ordinal = cpu_to_be32(TPM2_CC_PCR_EXTEND)
> -};
> -
> /**
> * tpm2_pcr_extend() - extend a PCR value
> *
> * @chip: TPM chip to use.
> * @pcr_idx: index of the PCR.
> - * @hash: hash value to use for the extend operation.
> + * @digests: list of pcr banks and corresponding hash values to be extended.
> *
> * Return: Same as with tpm_transmit_cmd.
> */
> -int tpm2_pcr_extend(struct tpm_chip *chip, int pcr_idx, const u8 *hash)
> +int tpm2_pcr_extend(struct tpm_chip *chip, int pcr_idx,
> + struct tpml_digest_values *digests)
> {
> - struct tpm2_cmd cmd;
> + struct tpm_buf buf;
> + struct tpm2_null_auth_area auth_area;
> int rc;
> + int i;
> + int j;
>
> - cmd.header.in = tpm2_pcrextend_header;
> - cmd.params.pcrextend_in.pcr_idx = cpu_to_be32(pcr_idx);
> - cmd.params.pcrextend_in.auth_area_size =
> - cpu_to_be32(sizeof(struct tpm2_null_auth_area));
> - cmd.params.pcrextend_in.auth_area.handle =
> - cpu_to_be32(TPM2_RS_PW);
> - cmd.params.pcrextend_in.auth_area.nonce_size = 0;
> - cmd.params.pcrextend_in.auth_area.attributes = 0;
> - cmd.params.pcrextend_in.auth_area.auth_size = 0;
> - cmd.params.pcrextend_in.digest_cnt = cpu_to_be32(1);
> - cmd.params.pcrextend_in.hash_alg = cpu_to_be16(TPM2_ALG_SHA1);
> - memcpy(cmd.params.pcrextend_in.digest, hash, TPM_DIGEST_SIZE);
> + rc = tpm_buf_init(&buf, TPM2_ST_SESSIONS, TPM2_CC_PCR_EXTEND);
> + if (rc)
> + return rc;
>
> - rc = tpm_transmit_cmd(chip, &cmd, sizeof(cmd), 0,
> + tpm_buf_append_u32(&buf, pcr_idx);
> +
> + auth_area.handle = cpu_to_be32(TPM2_RS_PW);
> + auth_area.nonce_size = 0;
> + auth_area.attributes = 0;
> + auth_area.auth_size = 0;
> +
> + 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, digests->count);
> +
> + for (i = 0; i < digests->count; i++) {
> + for (j = 0; j < ARRAY_SIZE(tpm2_hash_map); j++) {
> + if (digests->digests[i].alg_id !=
> + tpm2_hash_map[j].tpm_id)
> + continue;
> +
> + tpm_buf_append_u16(&buf, digests->digests[i].alg_id);
> + tpm_buf_append(&buf, (const unsigned char
> + *)&digests->digests[i].digest,
> + hash_digest_size[tpm2_hash_map[j].crypto_id]);
> + }
> + }
> +
> + rc = tpm_transmit_cmd(chip, buf.data, tpm_buf_length(&buf), 0,
> "attempting extend a PCR value");
>
> + tpm_buf_destroy(&buf);
> +
> return rc;
> }
>
> diff --git a/drivers/char/tpm/tpm_eventlog.h b/drivers/char/tpm/tpm_eventlog.h
> index 1660d74..2e47f4d 100644
> --- a/drivers/char/tpm/tpm_eventlog.h
> +++ b/drivers/char/tpm/tpm_eventlog.h
> @@ -2,9 +2,12 @@
> #ifndef __TPM_EVENTLOG_H__
> #define __TPM_EVENTLOG_H__
>
> +#include <crypto/hash_info.h>
> +
> #define TCG_EVENT_NAME_LEN_MAX 255
> #define MAX_TEXT_EVENT 1000 /* Max event string length */
> #define ACPI_TCPA_SIG "TCPA" /* 0x41504354 /'TCPA' */
> +#define TPM2_ACTIVE_PCR_BANKS 3
>
> #ifdef CONFIG_PPC64
> #define do_endian_conversion(x) be32_to_cpu(x)
> @@ -73,6 +76,21 @@ enum tcpa_pc_event_ids {
> HOST_TABLE_OF_DEVICES,
> };
>
> +/**
> + * Digest structures for TPM 2.0 as defined in document
> + * Trusted Platform Module Library Part 2: Structures, Family "2.0".
> + */

Please remove this comment

> +
> +struct tpmt_ha {
> + u16 alg_id;
> + u8 digest[SHA384_DIGEST_SIZE];
> +} __packed;

struct tpm2_hash

> +struct tpml_digest_values {
> + u32 count;
> + struct tpmt_ha digests[TPM2_ACTIVE_PCR_BANKS];
> +} __packed;

Please remove this structure.

> +
> #if defined(CONFIG_ACPI)
> int tpm_read_log_acpi(struct tpm_chip *chip);
> #else
> --
> 2.5.0
>

/Jarkko