Re: [PATCH v7 2/2] tpm: add securityfs support for TPM 2.0 firmware event log

[Jarkko Sakkinen]

On Sun, Dec 11, 2016 at 12:35:33AM -0500, Nayna Jain wrote:
> Unlike the device driver support for TPM 1.2, the TPM 2.0 does
> not support the securityfs pseudo files for displaying the
> firmware event log.
> 
> This patch enables support for providing the TPM 2.0 event log in
> binary form. TPM 2.0 event log supports a crypto agile format that
> records multiple digests, which is different from TPM 1.2. This
> patch enables the tpm_bios_log_setup for TPM 2.0  and adds the
> event log parser which understand the TPM 2.0 crypto agile format.
> 
> Signed-off-by: Nayna Jain <nayna@xxxxxxxxxxxxxxxxxx>

There is something fundamentally wrong in this commit.

You must not allow this feature unless CONFIG_OF is set. It is the only
interface where the supply path of the event log is well defined on
platforms that include a TPM 2.0 chip.

There's buch casts in the form '(char *) foo'. They should be
'(char *)foo'.

> ---
>  drivers/char/tpm/Makefile                          |   2 +-
>  .../char/tpm/{tpm_eventlog.c => tpm1_eventlog.c}   |  35 ++--
>  drivers/char/tpm/tpm2_eventlog.c                   | 203 +++++++++++++++++++++
>  drivers/char/tpm/tpm_eventlog.h                    |  70 +++++++
>  4 files changed, 295 insertions(+), 15 deletions(-)
>  rename drivers/char/tpm/{tpm_eventlog.c => tpm1_eventlog.c} (95%)
>  create mode 100644 drivers/char/tpm/tpm2_eventlog.c
> 
> diff --git a/drivers/char/tpm/Makefile b/drivers/char/tpm/Makefile
> index a05b1eb..3d386a8 100644
> --- a/drivers/char/tpm/Makefile
> +++ b/drivers/char/tpm/Makefile
> @@ -3,7 +3,7 @@
>  #
>  obj-$(CONFIG_TCG_TPM) += tpm.o
>  tpm-y := tpm-interface.o tpm-dev.o tpm-sysfs.o tpm-chip.o tpm2-cmd.o \
> -		tpm_eventlog.o
> +		tpm1_eventlog.o tpm2_eventlog.o
>  tpm-$(CONFIG_ACPI) += tpm_ppi.o tpm_acpi.o
>  tpm-$(CONFIG_OF) += tpm_of.o
>  obj-$(CONFIG_TCG_TIS_CORE) += tpm_tis_core.o
> diff --git a/drivers/char/tpm/tpm_eventlog.c b/drivers/char/tpm/tpm1_eventlog.c
> similarity index 95%
> rename from drivers/char/tpm/tpm_eventlog.c
> rename to drivers/char/tpm/tpm1_eventlog.c
> index 11bb113..9a8605e 100644
> --- a/drivers/char/tpm/tpm_eventlog.c
> +++ b/drivers/char/tpm/tpm1_eventlog.c
> @@ -390,9 +390,6 @@ int tpm_bios_log_setup(struct tpm_chip *chip)
>  	unsigned int cnt;
>  	int rc = 0;
>  
> -	if (chip->flags & TPM_CHIP_FLAG_TPM2)
> -		return 0;
> -
>  	rc = tpm_read_log(chip);
>  	if (rc)
>  		return rc;
> @@ -407,7 +404,13 @@ int tpm_bios_log_setup(struct tpm_chip *chip)
>  	cnt++;
>  
>  	chip->bin_log_seqops.chip = chip;
> -	chip->bin_log_seqops.seqops = &tpm_binary_b_measurements_seqops;
> +	if (chip->flags & TPM_CHIP_FLAG_TPM2)
> +		chip->bin_log_seqops.seqops =
> +			&tpm2_binary_b_measurements_seqops;
> +	else
> +		chip->bin_log_seqops.seqops =
> +			&tpm_binary_b_measurements_seqops;
> +
>  
>  	chip->bios_dir[cnt] =
>  	    securityfs_create_file("binary_bios_measurements",
> @@ -418,17 +421,21 @@ int tpm_bios_log_setup(struct tpm_chip *chip)
>  		goto err;
>  	cnt++;
>  
> -	chip->ascii_log_seqops.chip = chip;
> -	chip->ascii_log_seqops.seqops = &tpm_ascii_b_measurements_seqops;
> +	if (!(chip->flags & TPM_CHIP_FLAG_TPM2)) {
>  
> -	chip->bios_dir[cnt] =
> -	    securityfs_create_file("ascii_bios_measurements",
> -				   0440, chip->bios_dir[0],
> -				   (void *)&chip->ascii_log_seqops,
> -				   &tpm_bios_measurements_ops);
> -	if (IS_ERR(chip->bios_dir[cnt]))
> -		goto err;
> -	cnt++;
> +		chip->ascii_log_seqops.chip = chip;
> +		chip->ascii_log_seqops.seqops =
> +			&tpm_ascii_b_measurements_seqops;
> +
> +		chip->bios_dir[cnt] =
> +			securityfs_create_file("ascii_bios_measurements",
> +					       0440, chip->bios_dir[0],
> +					       (void *)&chip->ascii_log_seqops,
> +					       &tpm_bios_measurements_ops);
> +		if (IS_ERR(chip->bios_dir[cnt]))
> +			goto err;
> +		cnt++;
> +	}
>  
>  	return 0;
>  
> diff --git a/drivers/char/tpm/tpm2_eventlog.c b/drivers/char/tpm/tpm2_eventlog.c
> new file mode 100644
> index 0000000..63690d3
> --- /dev/null
> +++ b/drivers/char/tpm/tpm2_eventlog.c
> @@ -0,0 +1,203 @@
> +/*
> + * Copyright (C) 2016 IBM Corporation
> + *
> + * Authors:
> + *      Nayna Jain <nayna@xxxxxxxxxxxxxxxxxx>
> + *
> + * Access to TPM 2.0 event log as written by Firmware.
> + * It assumes that writer of event log has followed TCG Specification
> + * for Family "2.0" and written the event data in little endian.
> + * With that, it doesn't need any endian conversion for structure
> + * content.
> + *
> + * This program is free software; you can redistribute it and/or
> + * modify it under the terms of the GNU General Public License
> + * as published by the Free Software Foundation; either version
> + * 2 of the License, or (at your option) any later version.
> + */
> +
> +#include <linux/seq_file.h>
> +#include <linux/fs.h>
> +#include <linux/security.h>
> +#include <linux/module.h>
> +#include <linux/slab.h>
> +
> +#include "tpm.h"
> +#include "tpm_eventlog.h"
> +
> +static int calc_tpm2_event_size(struct tcg_pcr_event2 *event,
> +		struct tcg_pcr_event *event_header)

Bad alignment.

> +{
> +	struct tcg_efi_specid_event *efispecid;
> +	struct tcg_event_field *event_field;
> +	void *marker;
> +	void *marker_start;
> +	int i;
> +	int j;
> +	u16 halg;
> +	u32 halg_size;
> +	size_t size;
> +
> +	/*
> +	 * TPM 2.0 supports extend to multiple PCR Banks. This implies
> +	 * event log also has multiple digest values, one for each PCR Bank.
> +	 * This is called Crypto Agile Log Entry Format.
> +	 * Below code implements the procedure defined in TCG EFI Protocol
> +	 * Specification Family "2.0" to parse the event log in Crypto Agile
> +	 * Log Entry Format.
> +	 */

Please, document the function and remove this inline comment.

> +
> +	marker = event;
> +	marker_start = marker;
> +	marker = marker + sizeof(event->pcr_idx) + sizeof(event->event_type)
> +		+ sizeof(event->digests.count);
> +
> +	efispecid = (struct tcg_efi_specid_event *) event_header->event;
> +
> +	for (i = 0; (i < event->digests.count) && (i < TPM2_ACTIVE_PCR_BANKS);
> +	     i++) {
> +		halg_size = sizeof(event->digests.digests[i].alg_id);
> +		memcpy(&halg, marker, halg_size);
> +		marker = marker + halg_size;
> +		for (j = 0; (j < efispecid->num_algs); j++) {
> +			if (halg == efispecid->digest_sizes[j].alg_id) {
> +				marker = marker +
> +					efispecid->digest_sizes[j].digest_size;
> +				break;
> +			}
> +		}
> +	}
> +
> +	event_field = (struct tcg_event_field *) marker;
> +	marker = marker + sizeof(event_field->event_size)
> +		+ event_field->event_size;
> +	size = marker - marker_start;
> +
> +	if ((event->event_type == 0) && (event_field->event_size == 0))
> +		return 0;
> +
> +	return size;
> +}
> +
> +static void *tpm2_bios_measurements_start(struct seq_file *m, loff_t *pos)
> +{
> +	struct tpm_chip *chip = m->private;
> +	struct tpm_bios_log *log = &chip->log;
> +	void *addr = log->bios_event_log;
> +	void *limit = log->bios_event_log_end;
> +	struct tcg_pcr_event *event_header;
> +	struct tcg_pcr_event2 *event;
> +	int i;
> +	size_t size;
> +
> +	event_header = addr;
> +	size = sizeof(struct tcg_pcr_event) - sizeof(event_header->event)
> +		+ event_header->event_size;
> +
> +	if (*pos == 0) {
> +		if (addr + size < limit) {
> +			if ((event_header->event_type == 0) &&
> +					(event_header->event_size == 0))
> +				return NULL;
> +			return SEQ_START_TOKEN;
> +		}
> +	}
> +
> +	if (*pos > 0) {
> +		addr += size;
> +		event = addr;
> +		size = calc_tpm2_event_size(event, event_header);
> +		if ((addr + size >=  limit) || (size == 0))
> +			return NULL;
> +	}
> +
> +	for (i = 0; i < (*pos - 1); i++) {
> +		event = addr;
> +		size = calc_tpm2_event_size(event, event_header);
> +
> +		if ((addr + size >= limit) || (size == 0))
> +			return NULL;
> +		addr += size;
> +	}
> +
> +	return addr;
> +}
> +
> +static void *tpm2_bios_measurements_next(struct seq_file *m, void *v,
> +		loff_t *pos)
> +{
> +	struct tcg_pcr_event *event_header;
> +	struct tcg_pcr_event2 *event;
> +	struct tpm_chip *chip = m->private;
> +	struct tpm_bios_log *log = &chip->log;
> +	void *limit = log->bios_event_log_end;
> +	void *marker;
> +	size_t event_size;
> +
> +	event_header = log->bios_event_log;
> +
> +	if (v == SEQ_START_TOKEN) {
> +		event_size = sizeof(struct tcg_pcr_event)
> +			- sizeof(event_header->event)
> +			+ event_header->event_size;

Bad alignment. Please, check the whole commit and if there is more of
these..

> +		marker = event_header;
> +	} else {
> +		event = v;
> +		event_size = calc_tpm2_event_size(event, event_header);
> +		if (event_size == 0)
> +			return NULL;
> +		marker =  event;
> +	}
> +
> +	marker = marker + event_size;
> +	if (marker >= limit)
> +		return NULL;
> +	v = marker;
> +	event = v;
> +
> +	event_size = calc_tpm2_event_size(event, event_header);
> +	if (((v + event_size) >= limit) || (event_size == 0))
> +		return NULL;
> +
> +	(*pos)++;
> +	return v;
> +}
> +
> +static void tpm2_bios_measurements_stop(struct seq_file *m, void *v)
> +{
> +}
> +
> +static int tpm2_binary_bios_measurements_show(struct seq_file *m, void *v)
> +{
> +	struct tpm_chip *chip = m->private;
> +	struct tpm_bios_log *log = &chip->log;
> +	struct tcg_pcr_event *event_header = log->bios_event_log;
> +	struct tcg_pcr_event2 *event = v;
> +	void *temp_ptr;
> +	size_t size;
> +
> +	if (v == SEQ_START_TOKEN) {
> +		size = sizeof(struct tcg_pcr_event)
> +			- sizeof(event_header->event)
> +			+ event_header->event_size;
> +
> +		temp_ptr = event_header;
> +
> +		if (size > 0)
> +			seq_write(m, temp_ptr, size);
> +	} else {
> +		size = calc_tpm2_event_size(event, event_header);
> +		temp_ptr = event;
> +		if (size > 0)
> +			seq_write(m, temp_ptr, size);
> +	}
> +
> +	return 0;
> +}
> +
> +const struct seq_operations tpm2_binary_b_measurements_seqops = {
> +	.start = tpm2_bios_measurements_start,
> +	.next = tpm2_bios_measurements_next,
> +	.stop = tpm2_bios_measurements_stop,
> +	.show = tpm2_binary_bios_measurements_show,
> +};
> diff --git a/drivers/char/tpm/tpm_eventlog.h b/drivers/char/tpm/tpm_eventlog.h
> index 1660d74..6886a11 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 +76,73 @@ enum tcpa_pc_event_ids {
>  	HOST_TABLE_OF_DEVICES,
>  };
>  
> +/*
> + * All the structures related to TPM 2.0 Event Log are taken from TCG EFI
> + * Protocol Specification, Family "2.0". Document is available on link
> + * http://www.trustedcomputinggroup.org/tcg-efi-protocol-specification/ .
> + * Information is also available on TCG PC Client Platform Firmware Profile
> + * Specification, Family "2.0".
> + * Detailed digest structures for TPM 2.0 are defined in document
> + * Trusted Platform Module Library Part 2: Structures, Family "2.0".
> + */
> +
> +/* TPM 2.0 Event log header algorithm spec. */
> +struct tcg_efi_specid_event_algs {
> +	u16 alg_id;
> +	u16 digest_size;
> +} __packed;
> +
> +/* TPM 2.0 Event log header data. */
> +struct tcg_efi_specid_event {
> +	u8 signature[16];
> +	u32 platform_class;
> +	u8 spec_version_minor;
> +	u8 spec_version_major;
> +	u8 spec_errata;
> +	u8 uintnsize;
> +	u32 num_algs;
> +	struct tcg_efi_specid_event_algs digest_sizes[TPM2_ACTIVE_PCR_BANKS];
> +	u8 vendor_info_size;
> +	u8 vendor_info[0];
> +} __packed;
> +
> +/* TPM 2.0 Event Log Header. */
> +struct tcg_pcr_event {
> +	u32 pcr_idx;
> +	u32 event_type;
> +	u8 digest[20];
> +	u32 event_size;
> +	u8 event[0];
> +} __packed;
> +
> +/* TPM 2.0 Crypto agile algorithm and respective digest. */
> +struct tpmt_ha {
> +	u16 alg_id;
> +	u8 digest[SHA384_DIGEST_SIZE];
> +} __packed;
> +
> +/* TPM 2.0 Crypto agile digests list. */
> +struct tpml_digest_values {
> +	u32 count;
> +	struct tpmt_ha digests[TPM2_ACTIVE_PCR_BANKS];
> +} __packed;
> +
> +/* TPM 2.0 Event field structure. */
> +struct tcg_event_field {
> +	u32 event_size;
> +	u8 event[0];
> +} __packed;
> +
> +/* TPM 2.0 Crypto agile log entry format. */

These one line comments are next to useless. Please remove them.

> +struct tcg_pcr_event2 {
> +	u32 pcr_idx;
> +	u32 event_type;
> +	struct tpml_digest_values digests;
> +	struct tcg_event_field event;
> +} __packed;
> +
> +extern const struct seq_operations tpm2_binary_b_measurements_seqops;
> +
>  #if defined(CONFIG_ACPI)
>  int tpm_read_log_acpi(struct tpm_chip *chip);
>  #else
> -- 
> 2.5.0
> 

/Jarkko