Re: [PATCH v4 8/8] tpm: add securityfs support for TPM 2.0 firmware event log

[Jarkko Sakkinen <jarkko.sakkinen-VuQAYsv1563Yd54FQh9/CA@public.gmane.org>]

On Wed, Sep 28, 2016 at 04:34:42AM -0400, Nayna Jain wrote:
> Unlike the device driver support for TPM 1.2, the TPM 2.0 support
> does not create 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 adds the TPM 2.0 event log parser to understand the crypto
> agile format.

I'll got through the patch (the split comment is valid)

> Signed-off-by: Nayna Jain <nayna-23VcF4HTsmIX0ybBhKVfKdBPR1lH4CV8@public.gmane.org>
> ---
>  drivers/char/tpm/Makefile            |   2 +-
>  drivers/char/tpm/tpm-chip.c          |  26 ++---
>  drivers/char/tpm/tpm2.h              |  79 +++++++++++++
>  drivers/char/tpm/tpm2_eventlog.c     | 216 +++++++++++++++++++++++++++++++++++
>  drivers/char/tpm/tpm_eventlog_init.c |  30 +++--
>  drivers/char/tpm/tpm_of.c            |  26 ++++-
>  6 files changed, 348 insertions(+), 31 deletions(-)
>  create mode 100644 drivers/char/tpm/tpm2.h
>  create mode 100644 drivers/char/tpm/tpm2_eventlog.c
> 
> diff --git a/drivers/char/tpm/Makefile b/drivers/char/tpm/Makefile
> index 1dc2671..f185a6a5 100644
> --- a/drivers/char/tpm/Makefile
> +++ b/drivers/char/tpm/Makefile
> @@ -3,7 +3,7 @@
>  #
>  obj-$(CONFIG_TCG_TPM) += tpm.o
>  tpm-y := tpm-interface.o tpm-dev.o tpm-sysfs.o tpm-chip.o tpm2-cmd.o \
> -		tpm_eventlog.o tpm_eventlog_init.o
> +		tpm_eventlog.o tpm_eventlog_init.o tpm2_eventlog.o
>  tpm-$(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-chip.c b/drivers/char/tpm/tpm-chip.c
> index 826609d..72715fa 100644
> --- a/drivers/char/tpm/tpm-chip.c
> +++ b/drivers/char/tpm/tpm-chip.c
> @@ -278,23 +278,12 @@ static void tpm_del_char_device(struct tpm_chip *chip)
>  
>  static int tpm1_chip_register(struct tpm_chip *chip)
>  {
> -	int rc;
>  	if (chip->flags & TPM_CHIP_FLAG_TPM2)
>  		return 0;
>  
>  	tpm_sysfs_add_device(chip);
>  
> -	rc = tpm_bios_log_setup(chip);
> -
> -	return rc;
> -}
> -
> -static void tpm1_chip_unregister(struct tpm_chip *chip)
> -{
> -	if (chip->flags & TPM_CHIP_FLAG_TPM2)
> -		return;
> -
> -	tpm_bios_log_teardown(chip);
> +	return 0;
>  }
>  
>  static void tpm_del_legacy_sysfs(struct tpm_chip *chip)
> @@ -370,10 +359,8 @@ int tpm_chip_register(struct tpm_chip *chip)
>  	tpm_add_ppi(chip);
>  
>  	rc = tpm_add_char_device(chip);
> -	if (rc) {
> -		tpm1_chip_unregister(chip);
> +	if (rc)
>  		return rc;
> -	}
>  
>  	chip->flags |= TPM_CHIP_FLAG_REGISTERED;
>  
> @@ -383,6 +370,12 @@ int tpm_chip_register(struct tpm_chip *chip)
>  		return rc;
>  	}
>  
> +	rc = tpm_bios_log_setup(chip);
> +	if (rc) {
> +		tpm_chip_unregister(chip);
> +		return rc;
> +	}
> +
>  	return 0;
>  }
>  EXPORT_SYMBOL_GPL(tpm_chip_register);
> @@ -405,9 +398,10 @@ void tpm_chip_unregister(struct tpm_chip *chip)
>  	if (!(chip->flags & TPM_CHIP_FLAG_REGISTERED))
>  		return;
>  
> +	tpm_bios_log_teardown(chip);
> +
>  	tpm_del_legacy_sysfs(chip);
>  
> -	tpm1_chip_unregister(chip);
>  	tpm_del_char_device(chip);
>  }
>  EXPORT_SYMBOL_GPL(tpm_chip_unregister);

This is good place for split. Do a separate patch that moves the BIOS
log setup to tpm_chip_register(). In the preceding commit, just return
if the chip is TPM2

> diff --git a/drivers/char/tpm/tpm2.h b/drivers/char/tpm/tpm2.h
> new file mode 100644
> index 0000000..399c15c
> --- /dev/null
> +++ b/drivers/char/tpm/tpm2.h
> @@ -0,0 +1,79 @@
> +#ifndef __TPM2_H__
> +#define __TPM2_H__
> +
> +#define TPM_ALG_SHA1_DIGEST_SIZE	20
> +#define TPM_ALG_SHA256_DIGEST_SIZE	32
> +#define TPM_ALG_SHA384_DIGEST_SIZE	48
> +
> +#define HASH_COUNT	3
> +#define MAX_TPM_LOG_MSG	128
> +#define MAX_DIGEST_SIZE	64
> +
> +/**
> + * All the structures related to 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".
> + */
> +
> +/* Event log header algorithm spec. */
> +struct tcg_efispecideventalgorithmsize {
> +	u16	alg_id;
> +	u16	digest_size;
> +} __packed;
> +
> +/* Event log header data. */
> +struct tcg_efispecideventstruct {
> +	u8					signature[16];
> +	u32					platform_class;
> +	u8					spec_version_minor;
> +	u8					spec_version_major;
> +	u8					spec_errata;
> +	u8					uintnsize;
> +	u32					num_algs;
> +	struct tcg_efispecideventalgorithmsize	digest_sizes[HASH_COUNT];
> +	u8					vendor_info_size;
> +	u8					vendor_info[0];
> +} __packed;

I think it would be good practice for the subsystem that struct fields
the fields are not aligned like this because it can easily break down
(not it in this particular case but some times you need to add nested
unions to structures).

For enums, it's easy to stay consistent and it improves readability.
There pros override cons (in a rare occasion you might need to realign
the fields).

I had discussion about this before with Jason. If I understood his point
right he was not aligning both for structs and enums. I agree with that
for structs.

I know that in tpm2-cmd.c I used aligning for structs but I think it
was not a good idea afterall.

> +
> +/* Header entry for eventlog. */
> +struct tcg_pcr_event {
> +	u32	pcr_idx;
> +	u32	event_type;
> +	u8	digest[20];
> +	u32	event_size;
> +	u8	event[MAX_TPM_LOG_MSG];
> +} __packed;
> +
> +/* Crypto Agile algorithm and respective digest. */
> +struct tpmt_ha {
> +	u16		alg_id;
> +	u8		digest[MAX_DIGEST_SIZE];
> +} __packed;
> +
> +/* Crypto agile digests list. */
> +struct tpml_digest_values {
> +	u32		count;
> +	struct tpmt_ha	digests[HASH_COUNT];
> +} __packed;
> +
> +/* Event field structure. */
> +struct tcg_event_field {
> +	u32	event_size;
> +	u8      event[MAX_TPM_LOG_MSG];
> +} __packed;
> +
> +/* Crypto agile log entry format for TPM 2.0. */
> +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_measurments_seqops;

There's a typo here. Also I'm wondering what this '_b_' stands for?

> +
> +#endif
> diff --git a/drivers/char/tpm/tpm2_eventlog.c b/drivers/char/tpm/tpm2_eventlog.c
> new file mode 100644
> index 0000000..32c7d5c
> --- /dev/null
> +++ b/drivers/char/tpm/tpm2_eventlog.c
> @@ -0,0 +1,216 @@
> +/*
> + * Copyright (C) 2016 IBM Corporation
> + *
> + * Authors:
> + *      Nayna Jain <nayna-23VcF4HTsmIX0ybBhKVfKdBPR1lH4CV8@public.gmane.org>
> + *
> + * Access to TPM 2.0 event log as written by Firmware.
> + * It assumes that writer of event log has followed TCG Spec 2.0
> + * has written the event struct 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 "tpm2.h"
> +#include "tpm_eventlog.h"
> +
> +
> +static int calc_tpm2_event_size(struct tcg_pcr_event2 *event,
> +		struct tcg_pcr_event *event_header)
> +{
> +	struct tcg_efispecideventstruct *efispecid;
> +	struct tcg_event_field *event_field;
> +	void *marker, *marker_start;
> +	int i, j;
> +	u16 halg;
> +	u32 halg_size;
> +	size_t size = 0;
> +
> +	/*
> +	 * NOTE: 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.
> +	 * TCG EFI Protocol Specification defines the procedure to parse
> +	 * the event log. Below code implements this procedure to parse
> +	 * correctly the Crypto agile log entry format.
> +	 * Example of Crypto Agile Log Digests Format :
> +	 * digest_values.count = 2;
> +	 * digest_values.digest[0].alg_id = sha1;
> +	 * digest_values.digest[0].digest.sha1 = {20 bytes raw data};
> +	 * digest_values.digest[1].alg_id = sha256;
> +	 * digest_values.digest[1].digest.sha256 = {32 bytes raw data};
> +	 * Offset of eventsize is sizeof(count) + sizeof(alg_id) + 20
> +	 *			+ sizeof(alg_id) + 32;
> +	 *
> +	 * Since, offset of event_size can vary based on digests count, offset
> +	 * has to be calculated at run time. void *marker is used to traverse
> +	 * the dynamic structure and calculate the offset of event_size.
> +	 */
> +
> +	marker = event;
> +	marker_start = marker;
> +	marker = marker + sizeof(event->pcr_idx) + sizeof(event->event_type)
> +		+ sizeof(event->digests.count);
> +
> +	efispecid = (struct tcg_efispecideventstruct *) event_header->event;
> +
> +	for (i = 0; (i < event->digests.count) && (i < HASH_COUNT); 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_bios_log *log = m->private;
> +	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 = 0;
> +
> +	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;
> +	}
> +
> +	/* read over *pos measurements */
> +	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_bios_log *log = m->private;
> +	void *limit = log->bios_event_log_end;
> +	void *marker;
> +	size_t event_size = 0;
> +
> +	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;
> +		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_bios_log *log = m->private;
> +	struct tcg_pcr_event *event_header = log->bios_event_log;
> +	struct tcg_pcr_event2 *event = v;
> +	void *temp_ptr;
> +	size_t size = 0;
> +
> +	if (v == SEQ_START_TOKEN) {
> +

Extra new line.

> +		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 {
> +

Extra new line.

> +		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_measurments_seqops = {
> +	.start = tpm2_bios_measurements_start,
> +	.next = tpm2_bios_measurements_next,
> +	.stop = tpm2_bios_measurements_stop,
> +	.show = tpm2_binary_bios_measurements_show,
> +};

I don't want to go too much into reviewing these because I don't have
facilities to run this code. Overrally it looks good to me (not same
as reviewed-by).

> diff --git a/drivers/char/tpm/tpm_eventlog_init.c b/drivers/char/tpm/tpm_eventlog_init.c
> index c4ac42630..aaac0e9 100644
> --- a/drivers/char/tpm/tpm_eventlog_init.c
> +++ b/drivers/char/tpm/tpm_eventlog_init.c
> @@ -28,6 +28,7 @@
>  #include <linux/slab.h>
>  
>  #include "tpm.h"
> +#include "tpm2.h"
>  #include "tpm_eventlog.h"
>  
>  static int tpm_bios_measurements_release(struct inode *inode,
> @@ -114,7 +115,11 @@ int tpm_bios_log_setup(struct tpm_chip *chip)
>  	chip->bios_dir_count++;
>  
>  	chip->bin_sfs_data.log = &chip->log;
> -	chip->bin_sfs_data.seqops = &tpm_binary_b_measurments_seqops;
> +	if (chip->flags & TPM_CHIP_FLAG_TPM2)
> +		chip->bin_sfs_data.seqops = &tpm2_binary_b_measurments_seqops;
> +	else
> +		chip->bin_sfs_data.seqops = &tpm_binary_b_measurments_seqops;
> +
>  
>  	chip->bios_dir[chip->bios_dir_count] =
>  	    securityfs_create_file("binary_bios_measurements",
> @@ -125,16 +130,19 @@ int tpm_bios_log_setup(struct tpm_chip *chip)
>  		goto err;
>  	chip->bios_dir_count++;
>  
> -	chip->ascii_sfs_data.log = &chip->log;
> -	chip->ascii_sfs_data.seqops =  &tpm_ascii_b_measurments_seqops;
> -	chip->bios_dir[chip->bios_dir_count] =
> -	    securityfs_create_file("ascii_bios_measurements",
> -				   S_IRUSR | S_IRGRP, chip->bios_dir[0],
> -				   (void *)&chip->ascii_sfs_data,
> -				   &tpm_bios_measurements_ops);
> -	if (is_bad(chip->bios_dir[chip->bios_dir_count]))
> -		goto err;
> -	chip->bios_dir_count++;
> +	if (!(chip->flags & TPM_CHIP_FLAG_TPM2)) {
> +		chip->ascii_sfs_data.log = &chip->log;
> +		chip->ascii_sfs_data.seqops =
> +			&tpm_ascii_b_measurments_seqops;
> +		chip->bios_dir[chip->bios_dir_count] =
> +			securityfs_create_file("ascii_bios_measurements",
> +				       S_IRUSR | S_IRGRP, chip->bios_dir[0],
> +				       (void *)&chip->ascii_sfs_data,
> +				       &tpm_bios_measurements_ops);
> +		if (is_bad(chip->bios_dir[chip->bios_dir_count]))
> +			goto err;
> +		chip->bios_dir_count++;
> +	}
>  
>  	return 0;
>  
> diff --git a/drivers/char/tpm/tpm_of.c b/drivers/char/tpm/tpm_of.c
> index 1464cae..d4151b5 100644
> --- a/drivers/char/tpm/tpm_of.c
> +++ b/drivers/char/tpm/tpm_of.c
> @@ -17,6 +17,7 @@
>  
>  #include <linux/slab.h>
>  #include <linux/of.h>
> +#include <linux/string.h>
>  
>  #include "tpm.h"
>  #include "tpm_eventlog.h"
> @@ -27,6 +28,7 @@ int read_log_of(struct tpm_chip *chip)
>  	const u32 *sizep;
>  	const u64 *basep;
>  	struct tpm_bios_log *log;
> +	u32 log_size;
>  
>  	log = &chip->log;
>  	if (chip->dev.parent->of_node)
> @@ -46,19 +48,37 @@ int read_log_of(struct tpm_chip *chip)
>  		return -EIO;
>  	}
>  
> +	/*
> +	 * For both vtpm/tpm, firmware has log addr and log size in big
> +	 * endian format. But in case of vtpm, there is a method called
> +	 * sml-handover which is run during kernel init even before
> +	 * device tree is setup. This sml-handover function takes care
> +	 * of endianness and writes to sml-base and sml-size in little
> +	 * endian format. For this reason, vtpm doesn't need conversion
> +	 * but physical tpm needs the conversion.
> +	 */
> +	if (of_property_match_string(np, "compatible", "IBM,vtpm") < 0)
> +		log_size = be32_to_cpup(sizep);
> +	else
> +		log_size = *sizep;
> +
>  	basep = of_get_property(np, "linux,sml-base", NULL);
>  	if (basep == NULL) {
>  		dev_dbg(&chip->dev, "%s: ERROR - SML not found\n", __func__);
>  		return -EIO;
>  	}
>  
> -	log->bios_event_log = kmalloc(*sizep, GFP_KERNEL);
> +	log->bios_event_log = kmalloc(log_size, GFP_KERNEL);
>  	if (!log->bios_event_log)
>  		return -ENOMEM;
>  
> -	log->bios_event_log_end = log->bios_event_log + *sizep;
> +	log->bios_event_log_end = log->bios_event_log + log_size;
>  
> -	memcpy(log->bios_event_log, __va(*basep), *sizep);
> +	if (of_property_match_string(np, "compatible", "IBM,vtpm") < 0)
> +		memcpy(chip->log.bios_event_log, __va(be64_to_cpup(basep)),
> +		       log_size);
> +	else
> +		memcpy(chip->log.bios_event_log, __va(*basep), log_size);
>  
>  	return 0;
>  }
> -- 
> 2.5.0
> 

/Jarkko

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