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[PATCH v8 05/12] tpm2-sessions: Define TPM2_NAME_MAX_SIZE

Jarkko Sakkinen posted 12 patches 1 month, 3 weeks ago
There is a newer version of this series
[PATCH v8 05/12] tpm2-sessions: Define TPM2_NAME_MAX_SIZE
Posted by Jarkko Sakkinen 1 month, 3 weeks ago 
Define TPM2_NAME_MAX_SIZE, which describes the maximum size for hashes
encoded as TPMT_HA, which the prime identifier used for persistent and
transient keys in TPM2 protocol.

Set its value to 'SHA512_DIGEST_SIZE + 2', as SHA512 has the largest
digest size of the algorithms in TCG algorithm repository.

In additionl, rename TPM2_NAME_SIZE as TPM2_NULL_NAME_SIZE in order to
avoid any possible confusion.

Signed-off-by: Jarkko Sakkinen <jarkko@kernel.org>
---
v6:
- Rewrote the commit message.
v2:
- Rename TPM2_NAME_SIZE as TPM2_NULL_NAME_SIZE.
---
 drivers/char/tpm/tpm-sysfs.c     |  2 +-
 drivers/char/tpm/tpm2-sessions.c |  2 +-
 include/linux/tpm.h              | 37 +++++++++++++++++++++-----------
 3 files changed, 27 insertions(+), 14 deletions(-)

diff --git a/drivers/char/tpm/tpm-sysfs.c b/drivers/char/tpm/tpm-sysfs.c
index 94231f052ea7..4a6a27ee295d 100644
--- a/drivers/char/tpm/tpm-sysfs.c
+++ b/drivers/char/tpm/tpm-sysfs.c
@@ -314,7 +314,7 @@ static ssize_t null_name_show(struct device *dev, struct device_attribute *attr,
 			      char *buf)
 {
 	struct tpm_chip *chip = to_tpm_chip(dev);
-	int size = TPM2_NAME_SIZE;
+	int size = TPM2_NULL_NAME_SIZE;
 
 	bin2hex(buf, chip->null_key_name, size);
 	size *= 2;
diff --git a/drivers/char/tpm/tpm2-sessions.c b/drivers/char/tpm/tpm2-sessions.c
index 4149379665c4..525b8622d1c3 100644
--- a/drivers/char/tpm/tpm2-sessions.c
+++ b/drivers/char/tpm/tpm2-sessions.c
@@ -137,7 +137,7 @@ struct tpm2_auth {
 	 * we must compute and remember
 	 */
 	u32 name_h[AUTH_MAX_NAMES];
-	u8 name[AUTH_MAX_NAMES][2 + SHA512_DIGEST_SIZE];
+	u8 name[AUTH_MAX_NAMES][TPM2_MAX_NAME_SIZE];
 };
 
 #ifdef CONFIG_TCG_TPM2_HMAC
diff --git a/include/linux/tpm.h b/include/linux/tpm.h
index 202da079d500..e10f2096eae7 100644
--- a/include/linux/tpm.h
+++ b/include/linux/tpm.h
@@ -27,9 +27,33 @@
 
 #define TPM_DIGEST_SIZE 20	/* Max TPM v1.2 PCR size */
 
+/*
+ * SHA-512 is, as of today, the largest digest in the TCG algorithm repository.
+ */
 #define TPM2_MAX_DIGEST_SIZE	SHA512_DIGEST_SIZE
+
+/*
+ * A TPM name digest i.e., TPMT_HA, is a concatenation of TPM_ALG_ID of the
+ * name algorithm and hash of TPMT_PUBLIC.
+ */
+#define TPM2_MAX_NAME_SIZE	(TPM2_MAX_DIGEST_SIZE + 2)
+
+/*
+ * The maximum number of PCR banks.
+ */
 #define TPM2_MAX_PCR_BANKS	8
 
+/*
+ * fixed define for the size of a name.  This is actually HASHALG size
+ * plus 2, so 32 for SHA256
+ */
+#define TPM2_NULL_NAME_SIZE	34
+
+/*
+ * The maximum size for an object context
+ */
+#define TPM2_MAX_CONTEXT_SIZE	4096
+
 struct tpm_chip;
 struct trusted_key_payload;
 struct trusted_key_options;
@@ -139,17 +163,6 @@ struct tpm_chip_seqops {
 /* fixed define for the curve we use which is NIST_P256 */
 #define EC_PT_SZ	32
 
-/*
- * fixed define for the size of a name.  This is actually HASHALG size
- * plus 2, so 32 for SHA256
- */
-#define TPM2_NAME_SIZE	34
-
-/*
- * The maximum size for an object context
- */
-#define TPM2_MAX_CONTEXT_SIZE 4096
-
 struct tpm_chip {
 	struct device dev;
 	struct device devs;
@@ -211,7 +224,7 @@ struct tpm_chip {
 	/* saved context for NULL seed */
 	u8 null_key_context[TPM2_MAX_CONTEXT_SIZE];
 	 /* name of NULL seed */
-	u8 null_key_name[TPM2_NAME_SIZE];
+	u8 null_key_name[TPM2_NULL_NAME_SIZE];
 	u8 null_ec_key_x[EC_PT_SZ];
 	u8 null_ec_key_y[EC_PT_SZ];
 	struct tpm2_auth *auth;
-- 
2.39.5
Re: [PATCH v8 05/12] tpm2-sessions: Define TPM2_NAME_MAX_SIZE
Posted by Jonathan McDowell 1 month, 2 weeks ago 
On Tue, Dec 16, 2025 at 11:21:39AM +0200, Jarkko Sakkinen wrote:
>Define TPM2_NAME_MAX_SIZE, which describes the maximum size for hashes
>encoded as TPMT_HA, which the prime identifier used for persistent and
>transient keys in TPM2 protocol.
>
>Set its value to 'SHA512_DIGEST_SIZE + 2', as SHA512 has the largest
>digest size of the algorithms in TCG algorithm repository.
>
>In additionl, rename TPM2_NAME_SIZE as TPM2_NULL_NAME_SIZE in order to
>avoid any possible confusion.

One minor capitalisation nit, otherwise:

Reviewed-by: Jonathan McDowell <noodles@meta.com>

>Signed-off-by: Jarkko Sakkinen <jarkko@kernel.org>
>---
>v6:
>- Rewrote the commit message.
>v2:
>- Rename TPM2_NAME_SIZE as TPM2_NULL_NAME_SIZE.
>---
> drivers/char/tpm/tpm-sysfs.c     |  2 +-
> drivers/char/tpm/tpm2-sessions.c |  2 +-
> include/linux/tpm.h              | 37 +++++++++++++++++++++-----------
> 3 files changed, 27 insertions(+), 14 deletions(-)
>
>diff --git a/drivers/char/tpm/tpm-sysfs.c b/drivers/char/tpm/tpm-sysfs.c
>index 94231f052ea7..4a6a27ee295d 100644
>--- a/drivers/char/tpm/tpm-sysfs.c
>+++ b/drivers/char/tpm/tpm-sysfs.c
>@@ -314,7 +314,7 @@ static ssize_t null_name_show(struct device *dev, struct device_attribute *attr,
> 			      char *buf)
> {
> 	struct tpm_chip *chip = to_tpm_chip(dev);
>-	int size = TPM2_NAME_SIZE;
>+	int size = TPM2_NULL_NAME_SIZE;
>
> 	bin2hex(buf, chip->null_key_name, size);
> 	size *= 2;
>diff --git a/drivers/char/tpm/tpm2-sessions.c b/drivers/char/tpm/tpm2-sessions.c
>index 4149379665c4..525b8622d1c3 100644
>--- a/drivers/char/tpm/tpm2-sessions.c
>+++ b/drivers/char/tpm/tpm2-sessions.c
>@@ -137,7 +137,7 @@ struct tpm2_auth {
> 	 * we must compute and remember
> 	 */
> 	u32 name_h[AUTH_MAX_NAMES];
>-	u8 name[AUTH_MAX_NAMES][2 + SHA512_DIGEST_SIZE];
>+	u8 name[AUTH_MAX_NAMES][TPM2_MAX_NAME_SIZE];
> };
>
> #ifdef CONFIG_TCG_TPM2_HMAC
>diff --git a/include/linux/tpm.h b/include/linux/tpm.h
>index 202da079d500..e10f2096eae7 100644
>--- a/include/linux/tpm.h
>+++ b/include/linux/tpm.h
>@@ -27,9 +27,33 @@
>
> #define TPM_DIGEST_SIZE 20	/* Max TPM v1.2 PCR size */
>
>+/*
>+ * SHA-512 is, as of today, the largest digest in the TCG algorithm repository.
>+ */
> #define TPM2_MAX_DIGEST_SIZE	SHA512_DIGEST_SIZE
>+
>+/*
>+ * A TPM name digest i.e., TPMT_HA, is a concatenation of TPM_ALG_ID of the
>+ * name algorithm and hash of TPMT_PUBLIC.
>+ */
>+#define TPM2_MAX_NAME_SIZE	(TPM2_MAX_DIGEST_SIZE + 2)
>+
>+/*
>+ * The maximum number of PCR banks.
>+ */
> #define TPM2_MAX_PCR_BANKS	8
>
>+/*
>+ * fixed define for the size of a name.  This is actually HASHALG size

"Fixed define".

>+ * plus 2, so 32 for SHA256
>+ */
>+#define TPM2_NULL_NAME_SIZE	34
>+
>+/*
>+ * The maximum size for an object context
>+ */
>+#define TPM2_MAX_CONTEXT_SIZE	4096
>+
> struct tpm_chip;
> struct trusted_key_payload;
> struct trusted_key_options;
>@@ -139,17 +163,6 @@ struct tpm_chip_seqops {
> /* fixed define for the curve we use which is NIST_P256 */
> #define EC_PT_SZ	32
>
>-/*
>- * fixed define for the size of a name.  This is actually HASHALG size
>- * plus 2, so 32 for SHA256
>- */
>-#define TPM2_NAME_SIZE	34
>-
>-/*
>- * The maximum size for an object context
>- */
>-#define TPM2_MAX_CONTEXT_SIZE 4096
>-
> struct tpm_chip {
> 	struct device dev;
> 	struct device devs;
>@@ -211,7 +224,7 @@ struct tpm_chip {
> 	/* saved context for NULL seed */
> 	u8 null_key_context[TPM2_MAX_CONTEXT_SIZE];
> 	 /* name of NULL seed */
>-	u8 null_key_name[TPM2_NAME_SIZE];
>+	u8 null_key_name[TPM2_NULL_NAME_SIZE];
> 	u8 null_ec_key_x[EC_PT_SZ];
> 	u8 null_ec_key_y[EC_PT_SZ];
> 	struct tpm2_auth *auth;
>-- 
>2.39.5
>
>

J.

-- 
Why do I get the feeling I'm going to regret this?
This .sig brought to you by the letter S and the number 50
Product of the Republic of HuggieTag
Re: [PATCH v8 05/12] tpm2-sessions: Define TPM2_NAME_MAX_SIZE
Posted by Jarkko Sakkinen 1 month ago 
On Fri, Dec 19, 2025 at 09:32:02AM +0000, Jonathan McDowell wrote:
> On Tue, Dec 16, 2025 at 11:21:39AM +0200, Jarkko Sakkinen wrote:
> > Define TPM2_NAME_MAX_SIZE, which describes the maximum size for hashes
> > encoded as TPMT_HA, which the prime identifier used for persistent and
> > transient keys in TPM2 protocol.
> > 
> > Set its value to 'SHA512_DIGEST_SIZE + 2', as SHA512 has the largest
> > digest size of the algorithms in TCG algorithm repository.
> > 
> > In additionl, rename TPM2_NAME_SIZE as TPM2_NULL_NAME_SIZE in order to
> > avoid any possible confusion.
> 
> One minor capitalisation nit, otherwise:
> 
> Reviewed-by: Jonathan McDowell <noodles@meta.com>
> 
> > Signed-off-by: Jarkko Sakkinen <jarkko@kernel.org>
> > ---
> > v6:
> > - Rewrote the commit message.
> > v2:
> > - Rename TPM2_NAME_SIZE as TPM2_NULL_NAME_SIZE.
> > ---
> > drivers/char/tpm/tpm-sysfs.c     |  2 +-
> > drivers/char/tpm/tpm2-sessions.c |  2 +-
> > include/linux/tpm.h              | 37 +++++++++++++++++++++-----------
> > 3 files changed, 27 insertions(+), 14 deletions(-)
> > 
> > diff --git a/drivers/char/tpm/tpm-sysfs.c b/drivers/char/tpm/tpm-sysfs.c
> > index 94231f052ea7..4a6a27ee295d 100644
> > --- a/drivers/char/tpm/tpm-sysfs.c
> > +++ b/drivers/char/tpm/tpm-sysfs.c
> > @@ -314,7 +314,7 @@ static ssize_t null_name_show(struct device *dev, struct device_attribute *attr,
> > 			      char *buf)
> > {
> > 	struct tpm_chip *chip = to_tpm_chip(dev);
> > -	int size = TPM2_NAME_SIZE;
> > +	int size = TPM2_NULL_NAME_SIZE;
> > 
> > 	bin2hex(buf, chip->null_key_name, size);
> > 	size *= 2;
> > diff --git a/drivers/char/tpm/tpm2-sessions.c b/drivers/char/tpm/tpm2-sessions.c
> > index 4149379665c4..525b8622d1c3 100644
> > --- a/drivers/char/tpm/tpm2-sessions.c
> > +++ b/drivers/char/tpm/tpm2-sessions.c
> > @@ -137,7 +137,7 @@ struct tpm2_auth {
> > 	 * we must compute and remember
> > 	 */
> > 	u32 name_h[AUTH_MAX_NAMES];
> > -	u8 name[AUTH_MAX_NAMES][2 + SHA512_DIGEST_SIZE];
> > +	u8 name[AUTH_MAX_NAMES][TPM2_MAX_NAME_SIZE];
> > };
> > 
> > #ifdef CONFIG_TCG_TPM2_HMAC
> > diff --git a/include/linux/tpm.h b/include/linux/tpm.h
> > index 202da079d500..e10f2096eae7 100644
> > --- a/include/linux/tpm.h
> > +++ b/include/linux/tpm.h
> > @@ -27,9 +27,33 @@
> > 
> > #define TPM_DIGEST_SIZE 20	/* Max TPM v1.2 PCR size */
> > 
> > +/*
> > + * SHA-512 is, as of today, the largest digest in the TCG algorithm repository.
> > + */
> > #define TPM2_MAX_DIGEST_SIZE	SHA512_DIGEST_SIZE
> > +
> > +/*
> > + * A TPM name digest i.e., TPMT_HA, is a concatenation of TPM_ALG_ID of the
> > + * name algorithm and hash of TPMT_PUBLIC.
> > + */
> > +#define TPM2_MAX_NAME_SIZE	(TPM2_MAX_DIGEST_SIZE + 2)
> > +
> > +/*
> > + * The maximum number of PCR banks.
> > + */
> > #define TPM2_MAX_PCR_BANKS	8
> > 
> > +/*
> > + * fixed define for the size of a name.  This is actually HASHALG size
> 
> "Fixed define".

Thanks, yeah, I can fix this up :-)

> 
> > + * plus 2, so 32 for SHA256
> > + */
> > +#define TPM2_NULL_NAME_SIZE	34
> > +
> > +/*
> > + * The maximum size for an object context
> > + */
> > +#define TPM2_MAX_CONTEXT_SIZE	4096
> > +
> > struct tpm_chip;
> > struct trusted_key_payload;
> > struct trusted_key_options;
> > @@ -139,17 +163,6 @@ struct tpm_chip_seqops {
> > /* fixed define for the curve we use which is NIST_P256 */
> > #define EC_PT_SZ	32
> > 
> > -/*
> > - * fixed define for the size of a name.  This is actually HASHALG size
> > - * plus 2, so 32 for SHA256
> > - */
> > -#define TPM2_NAME_SIZE	34
> > -
> > -/*
> > - * The maximum size for an object context
> > - */
> > -#define TPM2_MAX_CONTEXT_SIZE 4096
> > -
> > struct tpm_chip {
> > 	struct device dev;
> > 	struct device devs;
> > @@ -211,7 +224,7 @@ struct tpm_chip {
> > 	/* saved context for NULL seed */
> > 	u8 null_key_context[TPM2_MAX_CONTEXT_SIZE];
> > 	 /* name of NULL seed */
> > -	u8 null_key_name[TPM2_NAME_SIZE];
> > +	u8 null_key_name[TPM2_NULL_NAME_SIZE];
> > 	u8 null_ec_key_x[EC_PT_SZ];
> > 	u8 null_ec_key_y[EC_PT_SZ];
> > 	struct tpm2_auth *auth;
> > -- 
> > 2.39.5
> > 
> > 
> 
> J.
> 
> -- 
> Why do I get the feeling I'm going to regret this?
> This .sig brought to you by the letter S and the number 50
> Product of the Republic of HuggieTag

BR, Jarkko

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