Re: [PATCH v6 2/2] tpm: enhance TPM 2.0 PCR extend to support multiple banks

[Jarkko Sakkinen]

On Mon, Jan 23, 2017 at 10:11:48PM +0530, Nayna wrote:
> 
> 
> 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@xxxxxxxxxxxxxxxxxx>
> > > Reviewed-by: Jarkko Sakkinen <jarkko.sakkinen@xxxxxxxxxxxxxxx>
> > > ---
> > >   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.
> 

If it is common, why is it in tpm_eventlog.h and not in tpm.h?

> Thanks & Regards,
>   - Nayna

/Jarkko