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Subject[PATCH 2/2] TPM: integrity interface
Date
This patch adds internal kernel support for:
- reading/extending a pcr value
- looking up the tpm_chip for a given chip number

Signed-off-by: Rajiv Andrade <srajiv@linux.vnet.ibm.com>
Signed-off-by: Mimi Zohar <zohar@us.ibm.com>
---
drivers/char/tpm/tpm.c | 129 +++++++++++++++++++++++++++++++++++++++++-------
drivers/char/tpm/tpm.h | 18 +++++++
include/linux/tpm.h | 35 +++++++++++++
3 files changed, 163 insertions(+), 19 deletions(-)
create mode 100644 include/linux/tpm.h
diff --git a/drivers/char/tpm/tpm.c b/drivers/char/tpm/tpm.c
index 9b9eb76..0387965 100644
--- a/drivers/char/tpm/tpm.c
+++ b/drivers/char/tpm/tpm.c
@@ -661,28 +661,125 @@ ssize_t tpm_show_temp_deactivated(struct device * dev,
}
EXPORT_SYMBOL_GPL(tpm_show_temp_deactivated);

-static const u8 pcrread[] = {
- 0, 193, /* TPM_TAG_RQU_COMMAND */
- 0, 0, 0, 14, /* length */
- 0, 0, 0, 21, /* TPM_ORD_PcrRead */
- 0, 0, 0, 0 /* PCR index */
+/*
+ * tpm_chip_find_get - return tpm_chip for given chip number
+ */
+static struct tpm_chip *tpm_chip_find_get(int chip_num)
+{
+ struct tpm_chip *pos;
+
+ rcu_read_lock();
+ list_for_each_entry_rcu(pos, &tpm_chip_list, list) {
+ if (chip_num != TPM_ANY_NUM && chip_num != pos->dev_num)
+ continue;
+
+ if (try_module_get(pos->dev->driver->owner))
+ break;
+ }
+ rcu_read_unlock();
+ return pos;
+}
+
+#define TPM_ORDINAL_PCRREAD cpu_to_be32(21)
+#define READ_PCR_RESULT_SIZE 30
+static struct tpm_input_header pcrread_header = {
+ .tag = TPM_TAG_RQU_COMMAND,
+ .length = cpu_to_be32(14),
+ .ordinal = TPM_ORDINAL_PCRREAD
+};
+
+int __tpm_pcr_read(struct tpm_chip *chip, int pcr_idx, u8 *res_buf)
+{
+ int rc;
+ struct tpm_cmd_t cmd;
+
+ cmd.header.in = pcrread_header;
+ cmd.params.pcrread_in.pcr_idx = cpu_to_be32(pcr_idx);
+ BUILD_BUG_ON(cmd.header.in.length > READ_PCR_RESULT_SIZE);
+ rc = transmit_cmd(chip, &cmd, cmd.header.in.length,
+ "attempting to read a pcr value");
+
+ if (rc == 0)
+ memcpy(res_buf, cmd.params.pcrread_out.pcr_result,
+ TPM_DIGEST_SIZE);
+ return rc;
+}
+
+/**
+ * tpm_pcr_read - read a pcr value
+ * @chip_num: tpm idx # or ANY
+ * @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_num, int pcr_idx, u8 *res_buf)
+{
+ struct tpm_chip *chip;
+ int rc;
+
+ chip = tpm_chip_find_get(chip_num);
+ if (chip == NULL)
+ return -ENODEV;
+ rc = __tpm_pcr_read(chip, pcr_idx, res_buf);
+ module_put(chip->dev->driver->owner);
+ return rc;
+}
+EXPORT_SYMBOL_GPL(tpm_pcr_read);
+
+/**
+ * tpm_pcr_extend - extend pcr value with hash
+ * @chip_num: 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.
+ */
+#define TPM_ORD_PCR_EXTEND cpu_to_be32(20)
+#define EXTEND_PCR_SIZE 34
+static struct tpm_input_header pcrextend_header = {
+ .tag = TPM_TAG_RQU_COMMAND,
+ .length = cpu_to_be32(34),
+ .ordinal = TPM_ORD_PCR_EXTEND
};

+int tpm_pcr_extend(u32 chip_num, int pcr_idx, const u8 *hash)
+{
+ struct tpm_cmd_t cmd;
+ int rc;
+ struct tpm_chip *chip;
+
+ chip = tpm_chip_find_get(chip_num);
+ if (chip == NULL)
+ return -ENODEV;
+
+ cmd.header.in = pcrextend_header;
+ BUILD_BUG_ON(be32_to_cpu(cmd.header.in.length) > EXTEND_PCR_SIZE);
+ cmd.params.pcrextend_in.pcr_idx = cpu_to_be32(pcr_idx);
+ memcpy(cmd.params.pcrextend_in.hash, hash, TPM_DIGEST_SIZE);
+ rc = transmit_cmd(chip, &cmd, cmd.header.in.length,
+ "attempting extend a PCR value");
+
+ module_put(chip->dev->driver->owner);
+ return rc;
+}
+EXPORT_SYMBOL_GPL(tpm_pcr_extend);
+
ssize_t tpm_show_pcrs(struct device *dev, struct device_attribute *attr,
char *buf)
{
cap_t cap;
- u8 *data;
+ u8 digest[TPM_DIGEST_SIZE];
ssize_t rc;
int i, j, num_pcrs;
- __be32 index;
char *str = buf;
struct tpm_chip *chip = dev_get_drvdata(dev);

- data = kzalloc(TPM_INTERNAL_RESULT_SIZE, GFP_KERNEL);
- if (!data)
- return -ENOMEM;
-
rc = tpm_getcap(dev, TPM_CAP_PROP_PCR, &cap,
"attempting to determine the number of PCRS");
if (rc)
@@ -690,20 +787,14 @@ ssize_t tpm_show_pcrs(struct device *dev, struct device_attribute *attr,

num_pcrs = be32_to_cpu(cap.num_pcrs);
for (i = 0; i < num_pcrs; i++) {
- memcpy(data, pcrread, sizeof(pcrread));
- index = cpu_to_be32(i);
- memcpy(data + 10, &index, 4);
- rc = transmit_cmd(chip, (struct tpm_cmd_t *)data,
- TPM_INTERNAL_RESULT_SIZE,
- "attempting to read a PCR");
+ rc = __tpm_pcr_read(chip, i, digest);
if (rc)
break;
str += sprintf(str, "PCR-%02d: ", i);
for (j = 0; j < TPM_DIGEST_SIZE; j++)
- str += sprintf(str, "%02X ", *(data + 10 + j));
+ str += sprintf(str, "%02X ", digest[j]);
str += sprintf(str, "\n");
}
- kfree(data);
return str - buf;
}
EXPORT_SYMBOL_GPL(tpm_show_pcrs);
diff --git a/drivers/char/tpm/tpm.h b/drivers/char/tpm/tpm.h
index d64f6b7..8e00b4d 100644
--- a/drivers/char/tpm/tpm.h
+++ b/drivers/char/tpm/tpm.h
@@ -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 */
@@ -234,11 +235,28 @@ typedef union {
struct tpm_output_header out;
} tpm_cmd_header;

+#define TPM_DIGEST_SIZE 20
+struct tpm_pcrread_out {
+ u8 pcr_result[TPM_DIGEST_SIZE];
+}__attribute__((packed));
+
+struct tpm_pcrread_in {
+ __be32 pcr_idx;
+}__attribute__((packed));
+
+struct tpm_pcrextend_in {
+ __be32 pcr_idx;
+ u8 hash[TPM_DIGEST_SIZE];
+}__attribute__((packed));
+
typedef union {
struct tpm_getcap_params_out getcap_out;
struct tpm_readpubek_params_out readpubek_out;
u8 readpubek_out_buffer[sizeof(struct tpm_readpubek_params_out)];
struct tpm_getcap_params_in getcap_in;
+ struct tpm_pcrread_in pcrread_in;
+ struct tpm_pcrread_out pcrread_out;
+ struct tpm_pcrextend_in pcrextend_in;
} tpm_cmd_params;

struct tpm_cmd_t {
diff --git a/include/linux/tpm.h b/include/linux/tpm.h
new file mode 100644
index 0000000..3338b3f
--- /dev/null
+++ b/include/linux/tpm.h
@@ -0,0 +1,35 @@
+/*
+ * Copyright (C) 2004,2007,2008 IBM Corporation
+ *
+ * Authors:
+ * Leendert van Doorn <leendert@watson.ibm.com>
+ * Dave Safford <safford@watson.ibm.com>
+ * Reiner Sailer <sailer@watson.ibm.com>
+ * Kylene Hall <kjhall@us.ibm.com>
+ * Debora Velarde <dvelarde@us.ibm.com>
+ *
+ * Maintained by: <tpmdd_devel@lists.sourceforge.net>
+ *
+ * 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__
+
+/*
+ * Chip num is this value or a valid tpm idx
+ */
+#define TPM_ANY_NUM 0xFFFF
+
+#if defined(CONFIG_TCG_TPM)
+
+extern int tpm_pcr_read(u32 chip_num, int pcr_idx, u8 *res_buf);
+extern int tpm_pcr_extend(u32 chip_num, int pcr_idx, const u8 *hash);
+#endif
+#endif
--
1.5.6.3


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