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Date:   Mon, 23 Jan 2017 22:11:48 +0530
From:   Nayna <nayna@...ux.vnet.ibm.com>
To:     Jarkko Sakkinen <jarkko.sakkinen@...ux.intel.com>
Cc:     tpmdd-devel@...ts.sourceforge.net, peterhuewe@....de,
        tpmdd@...horst.net, jgunthorpe@...idianresearch.com,
        linux-security-module@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v6 2/2] tpm: enhance TPM 2.0 PCR extend to support
 multiple banks



On 01/23/2017 08:49 PM, Jarkko Sakkinen wrote:
> On Fri, Jan 20, 2017 at 12:05:13PM -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.
>>
>> This patch reuses the defined digest sizes from the crypto subsystem,
>> adding a dependency on CRYPTO_HASH_INFO module.
>>
>> [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@...ux.vnet.ibm.com>
>> Reviewed-by: Jarkko Sakkinen <jarkko.sakkinen@...ux.intel.com>
>> ---
>>   drivers/char/tpm/Kconfig         |  1 +
>>   drivers/char/tpm/tpm-interface.c | 15 ++++++-
>>   drivers/char/tpm/tpm.h           |  3 +-
>>   drivers/char/tpm/tpm2-cmd.c      | 91 +++++++++++++++++++++-------------------
>>   drivers/char/tpm/tpm_eventlog.h  |  7 ++++
>>   5 files changed, 73 insertions(+), 44 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
>>   	---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 a3461cb..cf959c3 100644
>> --- a/drivers/char/tpm/tpm-interface.c
>> +++ b/drivers/char/tpm/tpm-interface.c
>> @@ -772,13 +772,26 @@ int tpm_pcr_extend(u32 chip_num, int pcr_idx, const u8 *hash)
>>   	struct tpm_cmd_t cmd;
>>   	int rc;
>>   	struct tpm_chip *chip;
>> +	int max_active_banks = ARRAY_SIZE(chip->active_banks);
>> +	struct tpm2_digest digest_list[max_active_banks];
>> +	u32 count = 0;
>> +	int i;
>>
>>   	chip = tpm_chip_find_get(chip_num);
>>   	if (chip == NULL)
>>   		return -ENODEV;
>>
>>   	if (chip->flags & TPM_CHIP_FLAG_TPM2) {
>> -		rc = tpm2_pcr_extend(chip, pcr_idx, hash);
>> +		memset(digest_list, 0, sizeof(digest_list));
>> +
>> +		for (i = 0; (chip->active_banks[i] != TPM2_ALG_ERROR) &&
>> +		     (i < max_active_banks); i++) {
>> +			digest_list[i].alg_id = chip->active_banks[i];
>> +			memcpy(digest_list[i].digest, hash, TPM_DIGEST_SIZE);
>> +			count++;
>> +		}
>> +
>> +		rc = tpm2_pcr_extend(chip, pcr_idx, count, digest_list);
>>   		tpm_put_ops(chip);
>>   		return rc;
>>   	}
>> diff --git a/drivers/char/tpm/tpm.h b/drivers/char/tpm/tpm.h
>> index c291f19..07a0677 100644
>> --- a/drivers/char/tpm/tpm.h
>> +++ b/drivers/char/tpm/tpm.h
>> @@ -534,7 +534,8 @@ 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, u32 count,
>> +		    struct tpm2_digest *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 0e000a3..d78adb8 100644
>> --- a/drivers/char/tpm/tpm2-cmd.c
>> +++ b/drivers/char/tpm/tpm2-cmd.c
>> @@ -53,22 +53,6 @@ struct tpm2_pcr_read_out {
>>   	u8	digest[TPM_DIGEST_SIZE];
>>   } __packed;
>>
>> -struct tpm2_null_auth_area {
>> -	__be32			handle;
>> -	__be16			nonce_size;
>> -	u8			attributes;
>> -	__be16			auth_size;
>> -} __packed;
>> -
>> -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];
>> -} __packed;
>> -
>>   struct tpm2_get_tpm_pt_in {
>>   	__be32	cap_id;
>>   	__be32	property_id;
>> @@ -97,7 +81,6 @@ union tpm2_cmd_params {
>>   	struct	tpm2_self_test_in	selftest_in;
>>   	struct	tpm2_pcr_read_in	pcrread_in;
>>   	struct	tpm2_pcr_read_out	pcrread_out;
>> -	struct	tpm2_pcr_extend_in	pcrextend_in;
>>   	struct	tpm2_get_tpm_pt_in	get_tpm_pt_in;
>>   	struct	tpm2_get_tpm_pt_out	get_tpm_pt_out;
>>   	struct	tpm2_get_random_in	getrandom_in;
>> @@ -290,46 +273,68 @@ 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)
>> -};
>> +struct tpm2_null_auth_area {
>> +	__be32  handle;
>> +	__be16  nonce_size;
>> +	u8  attributes;
>> +	__be16  auth_size;
>> +} __packed;
>>
>>   /**
>>    * 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.
>> + * @count:	number of digests passed.
>> + * @digests:	list of pcr banks and corresponding digest values to extend.
>>    *
>>    * 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, u32 count,
>> +		    struct tpm2_digest *digests)
>>   {
>> -	struct tpm2_cmd cmd;
>> +	struct tpm_buf buf;
>> +	struct tpm2_null_auth_area auth_area;
>>   	int rc;
>> +	int i;
>> +	int j;
>> +
>> +	if (count > ARRAY_SIZE(chip->active_banks))
>> +		return -EINVAL;
>>
>> -	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, 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]);
>> +		}
>> +	}
>> +
>> +	rc = tpm_transmit_cmd(chip, buf.data, tpm_buf_length(&buf), 0,
>>   			      "attempting extend a PCR value");
>>
>> +	tpm_buf_destroy(&buf);
>> +
>>   	return rc;
>>   }
>>
>> @@ -993,6 +998,8 @@ int tpm2_auto_startup(struct tpm_chip *chip)
>>   		}
>>   	}
>>
>> +	rc = tpm2_get_pcr_allocation(chip);
>> +
>>   out:
>>   	if (rc > 0)
>>   		rc = -ENODEV;
>> diff --git a/drivers/char/tpm/tpm_eventlog.h b/drivers/char/tpm/tpm_eventlog.h
>> index 1660d74..b5ae372 100644
>> --- a/drivers/char/tpm/tpm_eventlog.h
>> +++ b/drivers/char/tpm/tpm_eventlog.h
>> @@ -2,6 +2,8 @@
>>   #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' */
>> @@ -73,6 +75,11 @@ enum tcpa_pc_event_ids {
>>   	HOST_TABLE_OF_DEVICES,
>>   };
>>
>> +struct tpm2_digest {
>> +	u16 alg_id;
>> +	u8 digest[SHA512_DIGEST_SIZE];
>> +} __packed;
>
> Shouldn't this be in tpm.h?

This is a struct common for TPM 2.0 extend and eventlog structure i.e
struct tcg_pcr_event2.
And so I preferred to place it here.

Thanks & Regards,
   - Nayna

>
> /Jarkko
>

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