[PATCH v7 0/3] Optimize tpm2_read_public() calls

[PATCH v7 0/3] Optimize tpm2_read_public() calls

[Jarkko Sakkinen]

The main goal is fairly straight-forwrd here.

The aim of these patches is optimize the number of tpm2_read_public() calls
to the bare minimum. 

## About dropping 'parentName' attribute for ASN.1 keys from the patch set

I wrote this section as a remainder as I have facts fresh in my mind so 
that I can return them as soon as there is working group for the ASN.1 
specification. We really need to have this in the spec.

I dropped [1] given that [2] is landing shortly to IETF draft process,
according to James Bottomley [3]. We will return to [1] as soon as draft
process is open for comments. Still, that attribute is super important,
and here is why.

This will cause a overhead as tpm2_unseal_trusted needs to do an
unnecessary (from pure technical perspective) TPM2_ReadPublic command to
acquire TPM name of the parent. This is obviously known at the time of
creation of a key but the information is not stored anywhere by the
key format.

It also aligns badly with TCG specifications as Table 6 of architecture
spec explicitly defines a reference (or name) for transient keys,
persistent keys and NV indexes to be TPM_ALG_ID concatenated together
with the hash of TPMT_PUBLIC. I.e. the file format is using exactly
the opposite what should be use as reference for keys than what it 
should use.

Other benefits are of course auto-discovery of parent for a key file,
which is nasty to do without the name pre-stored.

[1] https://lore.kernel.org/linux-integrity/20251207173210.93765-3-jarkko@kernel.org/
[2] https://www.hansenpartnership.com/draft-bottomley-tpm2-keys.txt
[3] https://lore.kernel.org/linux-integrity/89d90617ba9b7a5eff1d5fad6bb9773033d3c18c.camel@HansenPartnership.com/

Jarkko Sakkinen (3):
  tpm2-sessions: Define TPM2_NAME_MAX_SIZE
  KEYS: trusted: Re-orchestrate tpm2_read_public() calls
  tpm2-sessions: Remove AUTH_MAX_NAMES

 drivers/char/tpm/tpm2-cmd.c               |   3 +-
 drivers/char/tpm/tpm2-sessions.c          | 116 ++++++--------------
 include/linux/tpm.h                       |  19 +++-
 security/keys/trusted-keys/trusted_tpm2.c | 124 ++++++++++++++--------
 4 files changed, 133 insertions(+), 129 deletions(-)

-- 
2.39.5

[PATCH v7 1/3] tpm2-sessions: Define TPM2_NAME_MAX_SIZE

[Jarkko Sakkinen]

This is somewhat cosmetic change but it does serve a purpose on tracking
the value set for the maximum length of TPM names, and to clearly states
what components it is composed of. It also anchors the value so that when
buffers are declared for this particular purpose, the same value is used
for the capacity.

Signed-off-by: Jarkko Sakkinen <jarkko@kernel.org>
---
v7:
- A new patch.
---
 drivers/char/tpm/tpm2-sessions.c | 2 +-
 include/linux/tpm.h              | 9 +++++++++
 2 files changed, 10 insertions(+), 1 deletion(-)

diff --git a/drivers/char/tpm/tpm2-sessions.c b/drivers/char/tpm/tpm2-sessions.c
index 79f27a46bd7f..a0c88fb1804c 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 42e2a091f43d..b4b5bd586501 100644
--- a/include/linux/tpm.h
+++ b/include/linux/tpm.h
@@ -28,7 +28,16 @@
 #define TPM_DIGEST_SIZE		20	/* Max TPM v1.2 PCR size */
 #define TPM_BUFSIZE		4096
 
+/*
+ * 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)
 #define TPM2_MAX_PCR_BANKS	8
 
 struct tpm_chip;
-- 
2.39.5

[PATCH v7 2/3] KEYS: trusted: Re-orchestrate tpm2_read_public() calls

[Jarkko Sakkinen]

tpm2_load_cmd() and tpm2_unseal_cmd() use the same parent, and calls to
tpm_buf_append_name() cause the exact same TPM2_ReadPublic command to be
sent to the chip, causing unnecessary traffic.

1. Export tpm2_read_public in order to make it callable from
   'trusted_tpm2'.
2. Re-orchestrate tpm2_seal_trusted() and tpm2_unseal_trusted() in order to
   halve the name resolutions required:
2a. Move tpm2_read_public() calls into trusted_tpm2.
2b. Pass TPM name to tpm_buf_append_name().
2c. Rework tpm_buf_append_name() to use the pre-resolved name.

Signed-off-by: Jarkko Sakkinen <jarkko@kernel.org>
---
v7:
- No changes of any of the versions so far.
---
 drivers/char/tpm/tpm2-cmd.c               |   3 +-
 drivers/char/tpm/tpm2-sessions.c          |  95 +++++------------
 include/linux/tpm.h                       |  10 +-
 security/keys/trusted-keys/trusted_tpm2.c | 124 ++++++++++++++--------
 4 files changed, 118 insertions(+), 114 deletions(-)

diff --git a/drivers/char/tpm/tpm2-cmd.c b/drivers/char/tpm/tpm2-cmd.c
index 2682f5ec09cb..5b04e74b6377 100644
--- a/drivers/char/tpm/tpm2-cmd.c
+++ b/drivers/char/tpm/tpm2-cmd.c
@@ -199,7 +199,8 @@ int tpm2_pcr_extend(struct tpm_chip *chip, u32 pcr_idx,
 	tpm_buf_reset(buf, TPM2_ST_SESSIONS, TPM2_CC_PCR_EXTEND);
 
 	if (!disable_pcr_integrity) {
-		rc = tpm_buf_append_name(chip, buf, pcr_idx, NULL);
+		rc = tpm_buf_append_name(chip, buf, pcr_idx, (u8 *)&pcr_idx,
+					 sizeof(u32));
 		if (rc)
 			return rc;
 		tpm_buf_append_hmac_session(chip, buf, 0, NULL, 0);
diff --git a/drivers/char/tpm/tpm2-sessions.c b/drivers/char/tpm/tpm2-sessions.c
index a0c88fb1804c..0816a91134fc 100644
--- a/drivers/char/tpm/tpm2-sessions.c
+++ b/drivers/char/tpm/tpm2-sessions.c
@@ -136,8 +136,8 @@ struct tpm2_auth {
 	 * handle, but they are part of the session by name, which
 	 * we must compute and remember
 	 */
-	u32 name_h[AUTH_MAX_NAMES];
 	u8 name[AUTH_MAX_NAMES][TPM2_MAX_NAME_SIZE];
+	u16 name_size_tbl[AUTH_MAX_NAMES];
 };
 
 #ifdef CONFIG_TCG_TPM2_HMAC
@@ -163,7 +163,17 @@ static int name_size(const u8 *name)
 	}
 }
 
-static int tpm2_read_public(struct tpm_chip *chip, u32 handle, void *name)
+/**
+ * tpm2_read_public: Resolve TPM name for a handle
+ * @chip:		TPM chip to use.
+ * @handle:		TPM handle.
+ * @name:		A buffer for returning the name blob. Must have a
+ *			capacity of 'SHA512_DIGET_SIZE + 2' bytes at minimum
+ *
+ * Returns size of TPM handle name of success.
+ * Returns tpm_transmit_cmd error codes when TPM2_ReadPublic fails.
+ */
+int tpm2_read_public(struct tpm_chip *chip, u32 handle, void *name)
 {
 	u32 mso = tpm2_handle_mso(handle);
 	off_t offset = TPM_HEADER_SIZE;
@@ -212,14 +222,16 @@ static int tpm2_read_public(struct tpm_chip *chip, u32 handle, void *name)
 	memcpy(name, &buf->data[offset], rc);
 	return name_size_alg;
 }
+EXPORT_SYMBOL_GPL(tpm2_read_public);
 #endif /* CONFIG_TCG_TPM2_HMAC */
 
 /**
- * tpm_buf_append_name() - add a handle area to the buffer
- * @chip: the TPM chip structure
- * @buf: The buffer to be appended
- * @handle: The handle to be appended
- * @name: The name of the handle (may be NULL)
+ * tpm_buf_append_name() - Append a handle and store TPM name
+ * @chip:		TPM chip to use.
+ * @buf:		TPM buffer containing the TPM command in-transit.
+ * @handle:		TPM handle to be appended.
+ * @name:		TPM name of the handle
+ * @name_size:		Size of the TPM name.
  *
  * In order to compute session HMACs, we need to know the names of the
  * objects pointed to by the handles.  For most objects, this is simply
@@ -236,15 +248,14 @@ static int tpm2_read_public(struct tpm_chip *chip, u32 handle, void *name)
  * will be caused by an incorrect programming model and indicated by a
  * kernel message.
  *
- * Ends the authorization session on failure.
+ * Returns zero on success.
+ * Returns -EIO when the authorization area state is malformed.
  */
 int tpm_buf_append_name(struct tpm_chip *chip, struct tpm_buf *buf,
-			u32 handle, u8 *name)
+			u32 handle, u8 *name, u16 name_size)
 {
 #ifdef CONFIG_TCG_TPM2_HMAC
-	enum tpm2_mso_type mso = tpm2_handle_mso(handle);
 	struct tpm2_auth *auth;
-	u16 name_size_alg;
 	int slot;
 	int ret;
 #endif
@@ -269,36 +280,15 @@ int tpm_buf_append_name(struct tpm_chip *chip, struct tpm_buf *buf,
 	}
 	tpm_buf_append_u32(buf, handle);
 	auth->session += 4;
-
-	if (mso == TPM2_MSO_PERSISTENT ||
-	    mso == TPM2_MSO_VOLATILE ||
-	    mso == TPM2_MSO_NVRAM) {
-		if (!name) {
-			ret = tpm2_read_public(chip, handle, auth->name[slot]);
-			if (ret < 0)
-				goto err;
-
-			name_size_alg = ret;
-		}
-	} else {
-		if (name) {
-			dev_err(&chip->dev, "handle 0x%08x does not use a name\n",
-				handle);
-			ret = -EIO;
-			goto err;
-		}
-	}
-
-	auth->name_h[slot] = handle;
-	if (name)
-		memcpy(auth->name[slot], name, name_size_alg);
+	memcpy(auth->name[slot], name, name_size);
+	auth->name_size_tbl[slot] = name_size;
 #endif
 	return 0;
 
 #ifdef CONFIG_TCG_TPM2_HMAC
 err:
 	tpm2_end_auth_session(chip);
-	return tpm_ret_to_err(ret);
+	return ret;
 #endif
 }
 EXPORT_SYMBOL_GPL(tpm_buf_append_name);
@@ -606,22 +596,8 @@ int tpm_buf_fill_hmac_session(struct tpm_chip *chip, struct tpm_buf *buf)
 	attrs = chip->cc_attrs_tbl[i];
 
 	handles = (attrs >> TPM2_CC_ATTR_CHANDLES) & GENMASK(2, 0);
+	offset_s += handles * sizeof(u32);
 
-	/*
-	 * just check the names, it's easy to make mistakes.  This
-	 * would happen if someone added a handle via
-	 * tpm_buf_append_u32() instead of tpm_buf_append_name()
-	 */
-	for (i = 0; i < handles; i++) {
-		u32 handle = tpm_buf_read_u32(buf, &offset_s);
-
-		if (auth->name_h[i] != handle) {
-			dev_err(&chip->dev, "invalid handle 0x%08x\n", handle);
-			ret = -EIO;
-			goto err;
-		}
-	}
-	/* point offset_s to the start of the sessions */
 	val = tpm_buf_read_u32(buf, &offset_s);
 	/* point offset_p to the start of the parameters */
 	offset_p = offset_s + val;
@@ -682,23 +658,8 @@ int tpm_buf_fill_hmac_session(struct tpm_chip *chip, struct tpm_buf *buf)
 	/* ordinal is already BE */
 	sha256_update(&sctx, (u8 *)&head->ordinal, sizeof(head->ordinal));
 	/* add the handle names */
-	for (i = 0; i < handles; i++) {
-		enum tpm2_mso_type mso = tpm2_handle_mso(auth->name_h[i]);
-
-		if (mso == TPM2_MSO_PERSISTENT ||
-		    mso == TPM2_MSO_VOLATILE ||
-		    mso == TPM2_MSO_NVRAM) {
-			ret = name_size(auth->name[i]);
-			if (ret < 0)
-				goto err;
-
-			sha256_update(&sctx, auth->name[i], ret);
-		} else {
-			__be32 h = cpu_to_be32(auth->name_h[i]);
-
-			sha256_update(&sctx, (u8 *)&h, 4);
-		}
-	}
+	for (i = 0; i < handles; i++)
+		sha256_update(&sctx, auth->name[i], auth->name_size_tbl[i]);
 	if (offset_s != tpm_buf_length(buf))
 		sha256_update(&sctx, &buf->data[offset_s],
 			      tpm_buf_length(buf) - offset_s);
diff --git a/include/linux/tpm.h b/include/linux/tpm.h
index b4b5bd586501..db716841973f 100644
--- a/include/linux/tpm.h
+++ b/include/linux/tpm.h
@@ -539,7 +539,7 @@ static inline struct tpm2_auth *tpm2_chip_auth(struct tpm_chip *chip)
 }
 
 int tpm_buf_append_name(struct tpm_chip *chip, struct tpm_buf *buf,
-			u32 handle, u8 *name);
+			u32 handle, u8 *name, u16 name_size);
 void tpm_buf_append_hmac_session(struct tpm_chip *chip, struct tpm_buf *buf,
 				 u8 attributes, u8 *passphrase,
 				 int passphraselen);
@@ -553,6 +553,7 @@ int tpm_buf_fill_hmac_session(struct tpm_chip *chip, struct tpm_buf *buf);
 int tpm_buf_check_hmac_response(struct tpm_chip *chip, struct tpm_buf *buf,
 				int rc);
 void tpm2_end_auth_session(struct tpm_chip *chip);
+int tpm2_read_public(struct tpm_chip *chip, u32 handle, void *name);
 #else
 #include <linux/unaligned.h>
 
@@ -576,6 +577,13 @@ static inline int tpm_buf_check_hmac_response(struct tpm_chip *chip,
 {
 	return rc;
 }
+
+static inline int tpm2_read_public(struct tpm_chip *chip, u32 handle,
+				   void *name)
+{
+	memcpy(name, &handle, sizeof(u32));
+	return sizeof(u32);
+}
 #endif	/* CONFIG_TCG_TPM2_HMAC */
 
 #endif
diff --git a/security/keys/trusted-keys/trusted_tpm2.c b/security/keys/trusted-keys/trusted_tpm2.c
index fb76c4ea496f..b05808c39d9d 100644
--- a/security/keys/trusted-keys/trusted_tpm2.c
+++ b/security/keys/trusted-keys/trusted_tpm2.c
@@ -233,7 +233,9 @@ int tpm2_seal_trusted(struct tpm_chip *chip,
 		      struct trusted_key_payload *payload,
 		      struct trusted_key_options *options)
 {
+	u8 parent_name[TPM2_MAX_NAME_SIZE];
 	off_t offset = TPM_HEADER_SIZE;
+	u16 parent_name_size;
 	int blob_len = 0;
 	int hash;
 	u32 flags;
@@ -250,6 +252,12 @@ int tpm2_seal_trusted(struct tpm_chip *chip,
 	if (rc)
 		return rc;
 
+	rc = tpm2_read_public(chip, options->keyhandle, parent_name);
+	if (rc < 0)
+		goto out_put;
+
+	parent_name_size = rc;
+
 	rc = tpm2_start_auth_session(chip);
 	if (rc)
 		goto out_put;
@@ -264,7 +272,8 @@ int tpm2_seal_trusted(struct tpm_chip *chip,
 	tpm_buf_init(buf, TPM_BUFSIZE);
 	tpm_buf_reset(buf, TPM2_ST_SESSIONS, TPM2_CC_CREATE);
 
-	rc = tpm_buf_append_name(chip, buf, options->keyhandle, NULL);
+	rc = tpm_buf_append_name(chip, buf, options->keyhandle, parent_name,
+				 parent_name_size);
 	if (rc)
 		goto out_put;
 
@@ -356,48 +365,38 @@ int tpm2_seal_trusted(struct tpm_chip *chip,
 }
 
 /**
- * tpm2_load_cmd() - execute a TPM2_Load command
- *
- * @chip: TPM chip to use
- * @payload: the key data in clear and encrypted form
- * @options: authentication values and other options
- * @blob_handle: returned blob handle
+ * tpm2_load_cmd() - Execute TPM2_Load
+ * @chip:		TPM chip to use.
+ * @payload:		Key data in clear text.
+ * @options:		Trusted key options.
+ * @parent_name:	A cryptographic name, i.e. a TPMT_HA blob, of the
+ *			parent key.
+ * @blob:		The decoded payload for the key.
+ * @blob_handle:	On success, will contain handle to the loaded keyedhash
+ *			blob.
  *
- * Return: 0 on success.
- *        -E2BIG on wrong payload size.
- *        -EPERM on tpm error status.
- *        < 0 error from tpm_send.
+ * Return -E2BIG when the blob size is too small for all the data.
+ * Returns tpm_transmit_cmd() error codes when either TPM2_Load fails.
  */
 static int tpm2_load_cmd(struct tpm_chip *chip,
 			 struct trusted_key_payload *payload,
 			 struct trusted_key_options *options,
+			 u8 *parent_name,
+			 u16 parent_name_size,
+			 const u8 *blob,
 			 u32 *blob_handle)
 {
 	u8 *blob_ref __free(kfree) = NULL;
 	unsigned int private_len;
 	unsigned int public_len;
 	unsigned int blob_len;
-	u8 *blob, *pub;
+	const u8 *pub;
 	int rc;
 	u32 attrs;
 
-	rc = tpm2_key_decode(payload, options, &blob);
-	if (rc) {
-		/* old form */
-		blob = payload->blob;
-		payload->old_format = 1;
-	} else {
-		/* Bind for cleanup: */
-		blob_ref = blob;
-	}
-
-	/* new format carries keyhandle but old format doesn't */
-	if (!options->keyhandle)
-		return -EINVAL;
-
 	/* must be big enough for at least the two be16 size counts */
 	if (payload->blob_len < 4)
-		return -EINVAL;
+		return -E2BIG;
 
 	private_len = get_unaligned_be16(blob);
 
@@ -436,7 +435,8 @@ static int tpm2_load_cmd(struct tpm_chip *chip,
 	tpm_buf_init(buf, TPM_BUFSIZE);
 	tpm_buf_reset(buf, TPM2_ST_SESSIONS, TPM2_CC_LOAD);
 
-	rc = tpm_buf_append_name(chip, buf, options->keyhandle, NULL);
+	rc = tpm_buf_append_name(chip, buf, options->keyhandle, parent_name,
+				 parent_name_size);
 	if (rc)
 		return rc;
 
@@ -464,20 +464,23 @@ static int tpm2_load_cmd(struct tpm_chip *chip,
 }
 
 /**
- * tpm2_unseal_cmd() - execute a TPM2_Unload command
+ * tpm2_unseal_cmd() - Execute TPM2_Unload
  *
- * @chip: TPM chip to use
- * @payload: the key data in clear and encrypted form
- * @options: authentication values and other options
- * @blob_handle: blob handle
+ * @chip:		TPM chip to use
+ * @payload:		Key data in clear text.
+ * @options:		Trusted key options.
+ * @parent_name:	A cryptographic name, i.e. a TPMT_HA blob, of the
+ *			parent key.
+ * @blob_handle:	Handle to the loaded keyedhash blob.
  *
- * Return: 0 on success
- *         -EPERM on tpm error status
- *         < 0 error from tpm_send
+ * Return -E2BIG when the blob size is too small for all the data.
+ * Returns tpm_transmit_cmd() error codes when either TPM2_Load fails.
  */
 static int tpm2_unseal_cmd(struct tpm_chip *chip,
 			   struct trusted_key_payload *payload,
 			   struct trusted_key_options *options,
+			   u8 *parent_name,
+			   u16 parent_name_size,
 			   u32 blob_handle)
 {
 	struct tpm_header *head;
@@ -497,7 +500,8 @@ static int tpm2_unseal_cmd(struct tpm_chip *chip,
 	tpm_buf_init(buf, TPM_BUFSIZE);
 	tpm_buf_reset(buf, TPM2_ST_SESSIONS, TPM2_CC_UNSEAL);
 
-	rc = tpm_buf_append_name(chip, buf, options->keyhandle, NULL);
+	rc = tpm_buf_append_name(chip, buf, options->keyhandle, parent_name,
+				 parent_name_size);
 	if (rc)
 		return rc;
 
@@ -567,30 +571,60 @@ static int tpm2_unseal_cmd(struct tpm_chip *chip,
 }
 
 /**
- * tpm2_unseal_trusted() - unseal the payload of a trusted key
+ * tpm2_unseal_trusted() - Unseal a trusted key
+ * @chip:	TPM chip to use.
+ * @payload:	Key data in clear text.
+ * @options:	Trusted key options.
  *
- * @chip: TPM chip to use
- * @payload: the key data in clear and encrypted form
- * @options: authentication values and other options
- *
- * Return: Same as with tpm_send.
+ * Return -E2BIG when the blob size is too small for all the data.
+ * Return -EINVAL when parent's key handle has not been set.
+ * Returns tpm_transmit_cmd() error codes when either TPM2_Load or TPM2_Unseal
+ * fails.
  */
 int tpm2_unseal_trusted(struct tpm_chip *chip,
 			struct trusted_key_payload *payload,
 			struct trusted_key_options *options)
 {
+	u8 *blob_ref __free(kfree) = NULL;
+	u8 parent_name[TPM2_MAX_NAME_SIZE];
+	u16 parent_name_size;
 	u32 blob_handle;
+	u8 *blob;
 	int rc;
 
+	/*
+	 * Try to decode the provided blob as an ASN.1 blob. Assume that the
+	 * blob is in the legacy format if decoding does not end successfully.
+	 */
+	rc = tpm2_key_decode(payload, options, &blob);
+	if (rc) {
+		blob = payload->blob;
+		payload->old_format = 1;
+	} else {
+		blob_ref = blob;
+	}
+
+	if (!options->keyhandle)
+		return -EINVAL;
+
 	rc = tpm_try_get_ops(chip);
 	if (rc)
 		return rc;
 
-	rc = tpm2_load_cmd(chip, payload, options, &blob_handle);
+	rc = tpm2_read_public(chip, options->keyhandle, parent_name);
+	if (rc < 0)
+		goto out;
+
+	parent_name_size = rc;
+
+	rc = tpm2_load_cmd(chip, payload, options, parent_name,
+			   parent_name_size, blob, &blob_handle);
 	if (rc)
 		goto out;
 
-	rc = tpm2_unseal_cmd(chip, payload, options, blob_handle);
+	rc = tpm2_unseal_cmd(chip, payload, options, parent_name,
+			     parent_name_size, blob_handle);
+
 	tpm2_flush_context(chip, blob_handle);
 
 out:
-- 
2.39.5

[PATCH v7 3/3] tpm2-sessions: Remove AUTH_MAX_NAMES

[Jarkko Sakkinen]

In all of the call sites only one session is ever append. Thus, reduce
AUTH_MAX_NAMES, which leads into removing constant completely.

Signed-off-by: Jarkko Sakkinen <jarkko@kernel.org>
---
v7:
- A new patch.
---
 drivers/char/tpm/tpm2-sessions.c | 31 +++++++++++--------------------
 1 file changed, 11 insertions(+), 20 deletions(-)

diff --git a/drivers/char/tpm/tpm2-sessions.c b/drivers/char/tpm/tpm2-sessions.c
index 0816a91134fc..62a200ae72d7 100644
--- a/drivers/char/tpm/tpm2-sessions.c
+++ b/drivers/char/tpm/tpm2-sessions.c
@@ -72,9 +72,6 @@
 #include <crypto/sha2.h>
 #include <crypto/utils.h>
 
-/* maximum number of names the TPM must remember for authorization */
-#define AUTH_MAX_NAMES	3
-
 #define AES_KEY_BYTES	AES_KEYSIZE_128
 #define AES_KEY_BITS	(AES_KEY_BYTES*8)
 
@@ -136,8 +133,8 @@ struct tpm2_auth {
 	 * handle, but they are part of the session by name, which
 	 * we must compute and remember
 	 */
-	u8 name[AUTH_MAX_NAMES][TPM2_MAX_NAME_SIZE];
-	u16 name_size_tbl[AUTH_MAX_NAMES];
+	u8 name[TPM2_MAX_NAME_SIZE];
+	u16 name_size;
 };
 
 #ifdef CONFIG_TCG_TPM2_HMAC
@@ -254,11 +251,14 @@ EXPORT_SYMBOL_GPL(tpm2_read_public);
 int tpm_buf_append_name(struct tpm_chip *chip, struct tpm_buf *buf,
 			u32 handle, u8 *name, u16 name_size)
 {
-#ifdef CONFIG_TCG_TPM2_HMAC
 	struct tpm2_auth *auth;
-	int slot;
 	int ret;
-#endif
+
+	if (tpm_buf_length(buf) != TPM_HEADER_SIZE) {
+		dev_err(&chip->dev, "too many handles\n");
+		ret = -EIO;
+		goto err;
+	}
 
 	if (!tpm2_chip_auth(chip)) {
 		tpm_buf_append_handle(buf, handle);
@@ -266,12 +266,6 @@ int tpm_buf_append_name(struct tpm_chip *chip, struct tpm_buf *buf,
 	}
 
 #ifdef CONFIG_TCG_TPM2_HMAC
-	slot = (tpm_buf_length(buf) - TPM_HEADER_SIZE) / 4;
-	if (slot >= AUTH_MAX_NAMES) {
-		dev_err(&chip->dev, "too many handles\n");
-		ret = -EIO;
-		goto err;
-	}
 	auth = chip->auth;
 	if (auth->session != tpm_buf_length(buf)) {
 		dev_err(&chip->dev, "session state malformed");
@@ -280,16 +274,14 @@ int tpm_buf_append_name(struct tpm_chip *chip, struct tpm_buf *buf,
 	}
 	tpm_buf_append_u32(buf, handle);
 	auth->session += 4;
-	memcpy(auth->name[slot], name, name_size);
-	auth->name_size_tbl[slot] = name_size;
+	memcpy(auth->name, name, name_size);
+	auth->name_size = name_size;
 #endif
 	return 0;
 
-#ifdef CONFIG_TCG_TPM2_HMAC
 err:
 	tpm2_end_auth_session(chip);
 	return ret;
-#endif
 }
 EXPORT_SYMBOL_GPL(tpm_buf_append_name);
 
@@ -658,8 +650,7 @@ int tpm_buf_fill_hmac_session(struct tpm_chip *chip, struct tpm_buf *buf)
 	/* ordinal is already BE */
 	sha256_update(&sctx, (u8 *)&head->ordinal, sizeof(head->ordinal));
 	/* add the handle names */
-	for (i = 0; i < handles; i++)
-		sha256_update(&sctx, auth->name[i], auth->name_size_tbl[i]);
+	sha256_update(&sctx, auth->name, auth->name_size);
 	if (offset_s != tpm_buf_length(buf))
 		sha256_update(&sctx, &buf->data[offset_s],
 			      tpm_buf_length(buf) - offset_s);
-- 
2.39.5

Re: [PATCH v7 0/3] Optimize tpm2_read_public() calls

[Jarkko Sakkinen]

On Mon, Dec 08, 2025 at 07:06:16AM +0200, Jarkko Sakkinen wrote:
> The main goal is fairly straight-forwrd here.
> 
> The aim of these patches is optimize the number of tpm2_read_public() calls
> to the bare minimum. 
> 
> ## About dropping 'parentName' attribute for ASN.1 keys from the patch set
> 
> I wrote this section as a remainder as I have facts fresh in my mind so 
> that I can return them as soon as there is working group for the ASN.1 
> specification. We really need to have this in the spec.
> 
> I dropped [1] given that [2] is landing shortly to IETF draft process,
> according to James Bottomley [3]. We will return to [1] as soon as draft
> process is open for comments. Still, that attribute is super important,
> and here is why.
> 
> This will cause a overhead as tpm2_unseal_trusted needs to do an
> unnecessary (from pure technical perspective) TPM2_ReadPublic command to
> acquire TPM name of the parent. This is obviously known at the time of
> creation of a key but the information is not stored anywhere by the
> key format.
> 
> It also aligns badly with TCG specifications as Table 6 of architecture
> spec explicitly defines a reference (or name) for transient keys,
> persistent keys and NV indexes to be TPM_ALG_ID concatenated together
> with the hash of TPMT_PUBLIC. I.e. the file format is using exactly
> the opposite what should be use as reference for keys than what it 
> should use.
> 
> Other benefits are of course auto-discovery of parent for a key file,
> which is nasty to do without the name pre-stored.

Right and TPMT_HA is calculated everytime when a trusted key is
created, and right after that the already calculated data is simply
thrown into dumpster. And we are talking about spec compliant way
to refer other keys here, and only 66 bytes of extra payload.

I don't get it. And neither do I get how anyone would want to fix 
this issue with TPM2_CreatePrimary interception.

BR, Jarkko