Message-ID: <20120727203000.GA22684@linux.vnet.ibm.com>
Date:	Fri, 27 Jul 2012 15:30:00 -0500
From:	Kent Yoder <key@...ux.vnet.ibm.com>
To:	"H. Peter Anvin" <hpa@...or.com>
Cc:	James Morris <jmorris@...ei.org>, linux-kernel@...r.kernel.org,
	linux-security-module@...r.kernel.org,
	tpmdd-devel@...ts.sourceforge.net,
	Peter Huewe <peter.huewe@...ineon.com>,
	Bryan Freed <bfreed@...omium.org>,
	David Safford <safford@...ux.vnet.ibm.com>
Subject: Re: [GIT PULL] New TPM driver, hwrng driver and fixes

Hi,

> Since you no longer modify *max anywhere in this function, why leave it
> a pointer?  Making it pass by value seems more logical at that point
> (and cleaner).
> 
> The only consumer which can make use of partial result is
> tpm_rng_read(), but that will now return zero unless the buffer is filled.
> 
> My suggestion would be to drop the pointer and instead return a positive
> result (number of bytes) if you read anything and a negative result
> (-errno) on error.
> 
> That way, a caller which can only use an exact number of bytes should do:
> 
> 	rv = tpm_get_random(chip, buf, size);
> 	if (rv != size)
> 		/* error! */
> 
> ... and tpm_rng_read() can do something smarter.
> 
> 	-hpa

  Alrighty, please take a look at these two updated patches that should
address your comments. This made the rng driver even simpler than it
was, and simplified the trusted keys changes. I only needed to make one
update in tpm_get_random to cover for the case when the error was returned
by the tpm itself, where that error code could be a positive value.

Dave, I'd appreciate one more Ack here, since your code did change.

Thanks,
Kent

commit 477ec712124adb9a3317139288d550ec4f6c2b2e
Author: Kent Yoder <key@...ux.vnet.ibm.com>
Date:   Thu Jun 7 13:47:42 2012 -0500

    hw_random: add support for the TPM chip as a hardware RNG source
    
    This driver will make use of any available TPM chip on the system as a
    hwrng source.
    
    Signed-off-by: Kent Yoder <key@...ux.vnet.ibm.com>
    Acked-by: David Safford <safford@...ux.vnet.ibm.com>

diff --git a/drivers/char/hw_random/Kconfig b/drivers/char/hw_random/Kconfig
index f45dad3..4e8c01a 100644
--- a/drivers/char/hw_random/Kconfig
+++ b/drivers/char/hw_random/Kconfig
@@ -263,3 +263,16 @@ config HW_RANDOM_PSERIES
 	  module will be called pseries-rng.
 
 	  If unsure, say Y.
+
+config HW_RANDOM_TPM
+	tristate "TPM HW Random Number Generator support"
+	depends on HW_RANDOM && TCG_TPM
+	default HW_RANDOM
+	---help---
+	  This driver provides kernel-side support for the Random Number
+	  Generator in the Trusted Platform Module
+
+	  To compile this driver as a module, choose M here: the
+	  module will be called tpm-rng.
+
+	  If unsure, say Y.
diff --git a/drivers/char/hw_random/Makefile b/drivers/char/hw_random/Makefile
index d901dfa..5dc10da 100644
--- a/drivers/char/hw_random/Makefile
+++ b/drivers/char/hw_random/Makefile
@@ -23,3 +23,4 @@ obj-$(CONFIG_HW_RANDOM_NOMADIK) += nomadik-rng.o
 obj-$(CONFIG_HW_RANDOM_PICOXCELL) += picoxcell-rng.o
 obj-$(CONFIG_HW_RANDOM_PPC4XX) += ppc4xx-rng.o
 obj-$(CONFIG_HW_RANDOM_PSERIES) += pseries-rng.o
+obj-$(CONFIG_HW_RANDOM_TPM) += tpm-rng.o
diff --git a/drivers/char/hw_random/tpm-rng.c b/drivers/char/hw_random/tpm-rng.c
new file mode 100644
index 0000000..d6d4482
--- /dev/null
+++ b/drivers/char/hw_random/tpm-rng.c
@@ -0,0 +1,50 @@
+/*
+ * Copyright (C) 2012 Kent Yoder IBM Corporation
+ *
+ * HWRNG interfaces to pull RNG data from a TPM
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307 USA
+ */
+
+#include <linux/module.h>
+#include <linux/hw_random.h>
+#include <linux/tpm.h>
+
+#define MODULE_NAME "tpm-rng"
+
+static int tpm_rng_read(struct hwrng *rng, void *data, size_t max, bool wait)
+{
+	return tpm_get_random(TPM_ANY_NUM, data, max);
+}
+
+static struct hwrng tpm_rng = {
+	.name = MODULE_NAME,
+	.read = tpm_rng_read,
+};
+
+static int __init rng_init(void)
+{
+	return hwrng_register(&tpm_rng);
+}
+module_init(rng_init);
+
+static void __exit rng_exit(void)
+{
+	hwrng_unregister(&tpm_rng);
+}
+module_exit(rng_exit);
+
+MODULE_LICENSE("GPL v2");
+MODULE_AUTHOR("Kent Yoder <key@...ux.vnet.ibm.com>");
+MODULE_DESCRIPTION("RNG driver for TPM devices");


commit ad5f963f7b69b9f798944ebc0bbb02520ecf5cae
Author: Kent Yoder <key@...ux.vnet.ibm.com>
Date:   Thu Jun 7 13:47:14 2012 -0500

    tpm: Move tpm_get_random api into the TPM device driver
    
    Move the tpm_get_random api from the trusted keys code into the TPM
    device driver itself so that other callers can make use of it. Also,
    change the api slightly so that the number of bytes read is returned in
    the call, since the TPM command can potentially return fewer bytes than
    requested.
    
    Signed-off-by: Kent Yoder <key@...ux.vnet.ibm.com>
    Acked-by: David Safford <safford@...ux.vnet.ibm.com>

diff --git a/drivers/char/tpm/tpm.c b/drivers/char/tpm/tpm.c
index beb98c3..60051e2 100644
--- a/drivers/char/tpm/tpm.c
+++ b/drivers/char/tpm/tpm.c
@@ -32,12 +32,6 @@
 #include "tpm.h"
 #include "tpm_eventlog.h"
 
-enum tpm_const {
-	TPM_MINOR = 224,	/* officially assigned */
-	TPM_BUFSIZE = 4096,
-	TPM_NUM_DEVICES = 256,
-};
-
 enum tpm_duration {
 	TPM_SHORT = 0,
 	TPM_MEDIUM = 1,
@@ -483,6 +477,7 @@ static ssize_t transmit_cmd(struct tpm_chip *chip, struct tpm_cmd_t *cmd,
 #define TPM_INTERNAL_RESULT_SIZE 200
 #define TPM_TAG_RQU_COMMAND cpu_to_be16(193)
 #define TPM_ORD_GET_CAP cpu_to_be32(101)
+#define TPM_ORD_GET_RANDOM cpu_to_be32(70)
 
 static const struct tpm_input_header tpm_getcap_header = {
 	.tag = TPM_TAG_RQU_COMMAND,
@@ -1327,6 +1322,64 @@ int tpm_pm_resume(struct device *dev)
 }
 EXPORT_SYMBOL_GPL(tpm_pm_resume);
 
+#define TPM_GETRANDOM_RESULT_SIZE	18
+static struct tpm_input_header tpm_getrandom_header = {
+	.tag = TPM_TAG_RQU_COMMAND,
+	.length = cpu_to_be32(14),
+	.ordinal = TPM_ORD_GET_RANDOM
+};
+
+/**
+ * tpm_get_random() - Get random bytes from the tpm's RNG
+ * @chip_num: A specific chip number for the request or TPM_ANY_NUM
+ * @out: destination buffer for the random bytes
+ * @max: the max number of bytes to write to @out
+ *
+ * Returns < 0 on error and the number of bytes read on success
+ */
+int tpm_get_random(u32 chip_num, u8 *out, size_t max)
+{
+	struct tpm_chip *chip;
+	struct tpm_cmd_t tpm_cmd;
+	u32 recd, num_bytes = min_t(u32, max, TPM_MAX_RNG_DATA);
+	int err, total = 0, retries = 5;
+	u8 *dest = out;
+
+	chip = tpm_chip_find_get(chip_num);
+	if (chip == NULL)
+		return -ENODEV;
+
+	if (!out || !num_bytes || max > TPM_MAX_RNG_DATA)
+		return -EINVAL;
+
+	do {
+		tpm_cmd.header.in = tpm_getrandom_header;
+		tpm_cmd.params.getrandom_in.num_bytes = cpu_to_be32(num_bytes);
+
+		err = transmit_cmd(chip, &tpm_cmd,
+				   TPM_GETRANDOM_RESULT_SIZE + num_bytes,
+				   "attempting get random");
+		if (err) {
+			/* err can be positive if it came from the TPM itself,
+			 * so return a negative value here instead. */
+			err = -EFAULT;
+			goto out_err;
+		}
+
+		recd = be32_to_cpu(tpm_cmd.params.getrandom_out.rng_data_len);
+		memcpy(dest, tpm_cmd.params.getrandom_out.rng_data, recd);
+
+		dest += recd;
+		total += recd;
+		num_bytes -= recd;
+	} while (retries-- && total < max);
+
+	err = total;
+out_err:
+	return err;
+}
+EXPORT_SYMBOL_GPL(tpm_get_random);
+
 /* In case vendor provided release function, call it too.*/
 
 void tpm_dev_vendor_release(struct tpm_chip *chip)
diff --git a/drivers/char/tpm/tpm.h b/drivers/char/tpm/tpm.h
index b1c5280..610fe42 100644
--- a/drivers/char/tpm/tpm.h
+++ b/drivers/char/tpm/tpm.h
@@ -28,6 +28,12 @@
 #include <linux/io.h>
 #include <linux/tpm.h>
 
+enum tpm_const {
+	TPM_MINOR = 224,	/* officially assigned */
+	TPM_BUFSIZE = 4096,
+	TPM_NUM_DEVICES = 256,
+};
+
 enum tpm_timeout {
 	TPM_TIMEOUT = 5,	/* msecs */
 };
@@ -269,6 +275,21 @@ struct tpm_pcrextend_in {
 	u8	hash[TPM_DIGEST_SIZE];
 }__attribute__((packed));
 
+/* 128 bytes is an arbitrary cap. This could be as large as TPM_BUFSIZE - 18
+ * bytes, but 128 is still a relatively large number of random bytes and
+ * anything much bigger causes users of struct tpm_cmd_t to start getting
+ * compiler warnings about stack frame size. */
+#define TPM_MAX_RNG_DATA	128
+
+struct tpm_getrandom_out {
+	__be32 rng_data_len;
+	u8     rng_data[TPM_MAX_RNG_DATA];
+}__attribute__((packed));
+
+struct tpm_getrandom_in {
+	__be32 num_bytes;
+}__attribute__((packed));
+
 typedef union {
 	struct	tpm_getcap_params_out getcap_out;
 	struct	tpm_readpubek_params_out readpubek_out;
@@ -277,6 +298,8 @@ typedef union {
 	struct	tpm_pcrread_in	pcrread_in;
 	struct	tpm_pcrread_out	pcrread_out;
 	struct	tpm_pcrextend_in pcrextend_in;
+	struct	tpm_getrandom_in getrandom_in;
+	struct	tpm_getrandom_out getrandom_out;
 } tpm_cmd_params;
 
 struct tpm_cmd_t {
diff --git a/include/linux/tpm.h b/include/linux/tpm.h
index fdc718a..fcb627f 100644
--- a/include/linux/tpm.h
+++ b/include/linux/tpm.h
@@ -32,6 +32,7 @@
 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);
 extern int tpm_send(u32 chip_num, void *cmd, size_t buflen);
+extern int tpm_get_random(u32 chip_num, u8 *data, size_t max);
 #else
 static inline int tpm_pcr_read(u32 chip_num, int pcr_idx, u8 *res_buf) {
 	return -ENODEV;
@@ -42,5 +43,8 @@ static inline int tpm_pcr_extend(u32 chip_num, int pcr_idx, const u8 *hash) {
 static inline int tpm_send(u32 chip_num, void *cmd, size_t buflen) {
 	return -ENODEV;
 }
+static inline int tpm_get_random(u32 chip_num, u8 *data, size_t max) {
+	return -ENODEV;
+}
 #endif
 #endif
diff --git a/security/keys/trusted.c b/security/keys/trusted.c
index 2d5d041..e1dc198 100644
--- a/security/keys/trusted.c
+++ b/security/keys/trusted.c
@@ -369,38 +369,6 @@ static int trusted_tpm_send(const u32 chip_num, unsigned char *cmd,
 }
 
 /*
- * get a random value from TPM
- */
-static int tpm_get_random(struct tpm_buf *tb, unsigned char *buf, uint32_t len)
-{
-	int ret;
-
-	INIT_BUF(tb);
-	store16(tb, TPM_TAG_RQU_COMMAND);
-	store32(tb, TPM_GETRANDOM_SIZE);
-	store32(tb, TPM_ORD_GETRANDOM);
-	store32(tb, len);
-	ret = trusted_tpm_send(TPM_ANY_NUM, tb->data, sizeof tb->data);
-	if (!ret)
-		memcpy(buf, tb->data + TPM_GETRANDOM_SIZE, len);
-	return ret;
-}
-
-static int my_get_random(unsigned char *buf, int len)
-{
-	struct tpm_buf *tb;
-	int ret;
-
-	tb = kmalloc(sizeof *tb, GFP_KERNEL);
-	if (!tb)
-		return -ENOMEM;
-	ret = tpm_get_random(tb, buf, len);
-
-	kfree(tb);
-	return ret;
-}
-
-/*
  * Lock a trusted key, by extending a selected PCR.
  *
  * Prevents a trusted key that is sealed to PCRs from being accessed.
@@ -413,7 +381,7 @@ static int pcrlock(const int pcrnum)
 
 	if (!capable(CAP_SYS_ADMIN))
 		return -EPERM;
-	ret = my_get_random(hash, SHA1_DIGEST_SIZE);
+	ret = tpm_get_random(TPM_ANY_NUM, hash, SHA1_DIGEST_SIZE);
 	if (ret < 0)
 		return ret;
 	return tpm_pcr_extend(TPM_ANY_NUM, pcrnum, hash) ? -EINVAL : 0;
@@ -429,7 +397,7 @@ static int osap(struct tpm_buf *tb, struct osapsess *s,
 	unsigned char ononce[TPM_NONCE_SIZE];
 	int ret;
 
-	ret = tpm_get_random(tb, ononce, TPM_NONCE_SIZE);
+	ret = tpm_get_random(TPM_ANY_NUM, ononce, TPM_NONCE_SIZE);
 	if (ret < 0)
 		return ret;
 
@@ -524,7 +492,7 @@ static int tpm_seal(struct tpm_buf *tb, uint16_t keytype,
 	if (ret < 0)
 		goto out;
 
-	ret = tpm_get_random(tb, td->nonceodd, TPM_NONCE_SIZE);
+	ret = tpm_get_random(TPM_ANY_NUM, td->nonceodd, TPM_NONCE_SIZE);
 	if (ret < 0)
 		goto out;
 	ordinal = htonl(TPM_ORD_SEAL);
@@ -634,7 +602,7 @@ static int tpm_unseal(struct tpm_buf *tb,
 
 	ordinal = htonl(TPM_ORD_UNSEAL);
 	keyhndl = htonl(SRKHANDLE);
-	ret = tpm_get_random(tb, nonceodd, TPM_NONCE_SIZE);
+	ret = tpm_get_random(TPM_ANY_NUM, nonceodd, TPM_NONCE_SIZE);
 	if (ret < 0) {
 		pr_info("trusted_key: tpm_get_random failed (%d)\n", ret);
 		return ret;
@@ -935,6 +903,7 @@ static int trusted_instantiate(struct key *key, const void *data,
 	char *datablob;
 	int ret = 0;
 	int key_cmd;
+	size_t key_len;
 
 	if (datalen <= 0 || datalen > 32767 || !data)
 		return -EINVAL;
@@ -974,7 +943,8 @@ static int trusted_instantiate(struct key *key, const void *data,
 			pr_info("trusted_key: key_unseal failed (%d)\n", ret);
 		break;
 	case Opt_new:
-		ret = my_get_random(payload->key, payload->key_len);
+		key_len = payload->key_len;
+		ret = tpm_get_random(TPM_ANY_NUM, payload->key, key_len);
 		if (ret < 0) {
 			pr_info("trusted_key: key_create failed (%d)\n", ret);
 			goto out;

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