Re: [PATCH 1/3] integrity: TPM internel kernel interface

[Serge E. Hallyn]

Quoting Mimi Zohar (zohar@xxxxxxxxxxxxxxxxxx):
> The internal TPM kernel interface did not protect itself from
> the removal of the TPM driver, while being used.  We continue
> to protect the tpm_chip_list using the driver_lock as before,
> and are using an rcu lock to protect readers. The internal TPM

I still would like to see this spelled out somewhere - correct me
if I'm wrong but none of the patches sent so far have this spelled
out in in-line comments, do they?

It does look sane:

	1. writes to tpm_chip_list are protected by driver_lock
	2. readers of the list are protected by rcu
	3. chips which are read from the tpm_chip_list, if they
	   are used outside of the rcu_read_lock(), are pinned
	   using get_device(chip->dev) before releasing the
	   rcu_read_lock.

Like I say it looks sane, but something like the above summary
could stand to be in a comment on top of tpm.c or something.

> kernel interface now protects itself from the driver being
> removed by incrementing the module reference count.
> 
> Resubmitting integrity-tpm-internal-kernel-interface.patch, which
> was previously Signed-off-by Kylene Hall.
> Updated per feedback:
> 
> Adds the following support:
>   - make internal kernel interface to transmit TPM commands global
>   - adds reading a pcr value
>   - adds extending a pcr value
>   - adds lookup the tpm_chip for given chip number and type
> 
> Signed-off-by: Mimi Zohar <zohar@xxxxxxxxxxxxxxxxxx>
> Signed-off-by: Rajiv Andrade <srajiv@xxxxxxxxxxxxxxxxxx>

Now there are other, existing callers of tpm_transmit.  Are they
all protected by sysfs pinning the kobject and thereby the device,
for the duration of the call?

thanks,
-serge

> ---
> diff --git a/drivers/char/tpm/tpm.c b/drivers/char/tpm/tpm.c
> index 1fee703..bcef771 100644
> --- a/drivers/char/tpm/tpm.c
> +++ b/drivers/char/tpm/tpm.c
> @@ -1,11 +1,12 @@
>  /*
> - * Copyright (C) 2004 IBM Corporation
> + * Copyright (C) 2004,2007,2008 IBM Corporation
>   *
>   * Authors:
>   * Leendert van Doorn <leendert@xxxxxxxxxxxxxx>
>   * Dave Safford <safford@xxxxxxxxxxxxxx>
>   * Reiner Sailer <sailer@xxxxxxxxxxxxxx>
>   * Kylene Hall <kjhall@xxxxxxxxxx>
> + * Debora Velarde <dvelarde@xxxxxxxxxx>
>   *
>   * Maintained by: <tpmdd-devel@xxxxxxxxxxxxxxxxxxxxx>
>   *
> @@ -28,6 +29,14 @@
>  #include <linux/spinlock.h>
>  #include <linux/smp_lock.h>
>  
> +#include <linux/mm.h>
> +#include <linux/slab.h>
> +#include <linux/string.h>
> +#include <linux/crypto.h>
> +#include <linux/fs.h>
> +#include <linux/scatterlist.h>
> +#include <linux/rcupdate.h>
> +#include <asm/unaligned.h>
>  #include "tpm.h"
>  
>  enum tpm_const {
> @@ -50,6 +59,8 @@ enum tpm_duration {
>  static LIST_HEAD(tpm_chip_list);
>  static DEFINE_SPINLOCK(driver_lock);
>  static DECLARE_BITMAP(dev_mask, TPM_NUM_DEVICES);
> +#define TPM_CHIP_NUM_MASK       0x0000ffff
> +#define TPM_CHIP_TYPE_SHIFT     16
>  
>  /*
>   * Array with one entry per ordinal defining the maximum amount
> @@ -366,8 +377,7 @@ EXPORT_SYMBOL_GPL(tpm_calc_ordinal_duration);
>  /*
>   * Internal kernel interface to transmit TPM commands
>   */
> -static ssize_t tpm_transmit(struct tpm_chip *chip, const char *buf,
> -			    size_t bufsiz)
> +ssize_t tpm_transmit(struct tpm_chip *chip, char *buf, size_t bufsiz)
>  {
>  	ssize_t rc;
>  	u32 count, ordinal;
> @@ -425,6 +435,7 @@ out:
>  	mutex_unlock(&chip->tpm_mutex);
>  	return rc;
>  }
> +EXPORT_SYMBOL_GPL(tpm_transmit);
>  
>  #define TPM_DIGEST_SIZE 20
>  #define TPM_ERROR_SIZE 10
> @@ -710,6 +721,7 @@ ssize_t tpm_show_temp_deactivated(struct device * dev,
>  }
>  EXPORT_SYMBOL_GPL(tpm_show_temp_deactivated);
>  
> +#define READ_PCR_RESULT_SIZE 30
>  static const u8 pcrread[] = {
>  	0, 193,			/* TPM_TAG_RQU_COMMAND */
>  	0, 0, 0, 14,		/* length */
> @@ -765,6 +777,128 @@ out:
>  }
>  EXPORT_SYMBOL_GPL(tpm_show_pcrs);
>  
> +/*
> + * tpm_chip_lookup - return tpm_chip for given chip number and type
> + *
> + * Must be called with rcu_read_lock.
> + */
> +static struct tpm_chip *tpm_chip_lookup(int chip_num, int chip_typ)
> +{
> +	struct tpm_chip *pos;
> +	int rc;
> +
> +	list_for_each_entry_rcu(pos, &tpm_chip_list, list) {
> +		rc = (chip_num == TPM_ANY_NUM || pos->dev_num == chip_num)
> +		    && (chip_typ == TPM_ANY_TYPE);
> +		if (rc)
> +			return pos;
> +	}
> +	return NULL;
> +}
> +
> +/**
> + * tpm_pcr_read - read a pcr value
> + * @chip_id: 	tpm chip identifier
> + * 		Upper 2 bytes: ANY, HW_ONLY or SW_ONLY
> + * 		Lower 2 bytes: tpm idx # or AN&
> + * @pcr_idx:	pcr idx to retrieve
> + * @res_buf: 	TPM_PCR value
> + * 		size of res_buf is 20 bytes (or NULL if you don't care)
> + *
> + * The TPM driver should be built-in, but for whatever reason it
> + * isn't, protect against the chip disappearing, by incrementing
> + * the module usage count.
> + */
> +int tpm_pcr_read(u32 chip_id, int pcr_idx, u8 *res_buf)
> +{
> +	u8 data[READ_PCR_RESULT_SIZE];
> +	int rc;
> +	__be32 index;
> +	int chip_num = chip_id & TPM_CHIP_NUM_MASK;
> +	struct tpm_chip *chip;
> +
> +	rcu_read_lock();
> +	chip = tpm_chip_lookup(chip_num, chip_id >> TPM_CHIP_TYPE_SHIFT);
> +	if (chip == NULL) {
> +		rcu_read_unlock();
> +		return -ENODEV;
> +	}
> +	if (!try_module_get(chip->dev->driver->owner)) {
> +		rcu_read_unlock();
> +		return -ENODEV;
> +	}
> +	rcu_read_unlock();
> +
> +	BUILD_BUG_ON(sizeof(pcrread) > READ_PCR_RESULT_SIZE);
> +	memcpy(data, pcrread, sizeof(pcrread));
> +	index = cpu_to_be32(pcr_idx);
> +	memcpy(data + 10, &index, 4);
> +	rc = tpm_transmit(chip, data, sizeof(data));
> +	if (rc > 0)
> +		rc = get_unaligned_be32((__be32 *) (data + 6));
> +
> +	if (rc == 0 && res_buf)
> +		memcpy(res_buf, data + 10, TPM_DIGEST_SIZE);
> +
> +	module_put(chip->dev->driver->owner);
> +	return rc;
> +}
> +EXPORT_SYMBOL_GPL(tpm_pcr_read);
> +
> +#define EXTEND_PCR_SIZE 34
> +static const u8 pcrextend[] = {
> +	0, 193,			/* TPM_TAG_RQU_COMMAND */
> +	0, 0, 0, 34,		/* length */
> +	0, 0, 0, 20,		/* TPM_ORD_Extend */
> +	0, 0, 0, 0		/* PCR index */
> +};
> +
> +/**
> + * tpm_pcr_extend - extend pcr value with hash
> + * @chip_id: 	tpm chip identifier
> + * 		Upper 2 bytes: ANY, HW_ONLY or SW_ONLY
> + * 		Lower 2 bytes: tpm idx # or AN&
> + * @pcr_idx:	pcr idx to extend
> + * @hash: 	hash value used to extend pcr value
> + *
> + * The TPM driver should be built-in, but for whatever reason it
> + * isn't, protect against the chip disappearing, by incrementing
> + * the module usage count.
> + */
> +int tpm_pcr_extend(u32 chip_id, int pcr_idx, const u8 *hash)
> +{
> +	u8 data[EXTEND_PCR_SIZE];
> +	int rc;
> +	__be32 index;
> +	int chip_num = chip_id & TPM_CHIP_NUM_MASK;
> +	struct tpm_chip *chip;
> +
> +	rcu_read_lock();
> +	chip = tpm_chip_lookup(chip_num, chip_id >> TPM_CHIP_TYPE_SHIFT);
> +	if (chip == NULL) {
> +		rcu_read_unlock();
> +		return -ENODEV;
> +	}
> +	if (!try_module_get(chip->dev->driver->owner)) {
> +		rcu_read_unlock();
> +		return -ENODEV;
> +	}
> +	rcu_read_unlock();
> +
> +	BUILD_BUG_ON(sizeof(pcrextend) > EXTEND_PCR_SIZE);
> +	memcpy(data, pcrextend, sizeof(pcrextend));
> +	index = cpu_to_be32(pcr_idx);
> +	memcpy(data + 10, &index, 4);
> +	memcpy(data + 14, hash, TPM_DIGEST_SIZE);
> +	rc = tpm_transmit(chip, data, sizeof(data));
> +	if (rc > 0)
> +		rc = get_unaligned_be32((__be32 *) (data + 6));
> +
> +	module_put(chip->dev->driver->owner);
> +	return rc;
> +}
> +EXPORT_SYMBOL_GPL(tpm_pcr_extend);
> +
>  #define  READ_PUBEK_RESULT_SIZE 314
>  static const u8 readpubek[] = {
>  	0, 193,			/* TPM_TAG_RQU_COMMAND */
> diff --git a/drivers/char/tpm/tpm.h b/drivers/char/tpm/tpm.h
> index 8e30df4..e0ffddb 100644
> --- a/drivers/char/tpm/tpm.h
> +++ b/drivers/char/tpm/tpm.h
> @@ -1,5 +1,5 @@
>  /*
> - * Copyright (C) 2004 IBM Corporation
> + * Copyright (C) 2004, 2007, 2008 IBM Corporation
>   *
>   * Authors:
>   * Leendert van Doorn <leendert@xxxxxxxxxxxxxx>
> @@ -26,6 +26,7 @@
>  #include <linux/miscdevice.h>
>  #include <linux/platform_device.h>
>  #include <linux/io.h>
> +#include <linux/tpm.h>
>  
>  enum tpm_timeout {
>  	TPM_TIMEOUT = 5,	/* msecs */
> @@ -128,6 +129,7 @@ extern void tpm_get_timeouts(struct tpm_chip *);
>  extern void tpm_gen_interrupt(struct tpm_chip *);
>  extern void tpm_continue_selftest(struct tpm_chip *);
>  extern unsigned long tpm_calc_ordinal_duration(struct tpm_chip *, u32);
> +ssize_t tpm_transmit(struct tpm_chip *chip, char *buf, size_t bufsiz);
>  extern struct tpm_chip* tpm_register_hardware(struct device *,
>  				 const struct tpm_vendor_specific *);
>  extern int tpm_open(struct inode *, struct file *);
> diff --git a/drivers/char/tpm/tpm_tis.c b/drivers/char/tpm/tpm_tis.c
> index 717af7a..bc26116 100644
> --- a/drivers/char/tpm/tpm_tis.c
> +++ b/drivers/char/tpm/tpm_tis.c
> @@ -642,6 +642,9 @@ static __devexit void tpm_tis_pnp_remove(struct pnp_dev *dev)
>  
>  static struct pnp_driver tis_pnp_driver = {
>  	.name = "tpm_tis",
> +	.driver = {
> +		.owner = THIS_MODULE,
> +	},
>  	.id_table = tpm_pnp_tbl,
>  	.probe = tpm_tis_pnp_init,
>  	.suspend = tpm_tis_pnp_suspend,
> diff --git a/include/linux/tpm.h b/include/linux/tpm.h
> new file mode 100644
> index 0000000..355a442
> --- /dev/null
> +++ b/include/linux/tpm.h
> @@ -0,0 +1,49 @@
> +/*
> + * Copyright (C) 2004,2007,2008 IBM Corporation
> + *
> + * Authors:
> + * Leendert van Doorn <leendert@xxxxxxxxxxxxxx>
> + * Dave Safford <safford@xxxxxxxxxxxxxx>
> + * Reiner Sailer <sailer@xxxxxxxxxxxxxx>
> + * Kylene Hall <kjhall@xxxxxxxxxx>
> + * Debora Velarde <dvelarde@xxxxxxxxxx>
> + *
> + * Maintained by: <tpmdd_devel@xxxxxxxxxxxxxxxxxxxxx>
> + *
> + * Device driver for TCG/TCPA TPM (trusted platform module).
> + * Specifications at www.trustedcomputinggroup.org
> + *
> + * 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, version 2 of the
> + * License.
> + *
> + */
> +#ifndef __LINUX_TPM_H__
> +#define __LINUX_TPM_H__
> +
> +#define PCI_DEVICE_ID_AMD_8111_LPC    0x7468
> +
> +/*
> + * Chip type is one of these values in the upper two bytes of chip_id
> + */
> +enum tpm_chip_type {
> +	TPM_HW_TYPE = 0x0,
> +	TPM_SW_TYPE = 0x1,
> +	TPM_ANY_TYPE = 0xFFFF,
> +};
> +
> +/*
> + * Chip num is this value or a valid tpm idx in lower two bytes of chip_id
> + */
> +enum tpm_chip_num {
> +	TPM_ANY_NUM = 0xFFFF,
> +};
> +
> +
> +#if defined(CONFIG_TCG_TPM) || defined(CONFIG_TCG_TPM_MODULE)
> +
> +extern int tpm_pcr_read(u32 chip_id, int pcr_idx, u8 *res_buf);
> +extern int tpm_pcr_extend(u32 chip_id, int pcr_idx, const u8 *hash);
> +#endif
> +#endif
> -- 
> 1.5.5.1
> 
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