[PATCH] tpm2-sessions: Fix tpm2_read_public range checks

Jarkko Sakkinen
2025-12-01T16:55:55Z

'tpm2_read_public' has some rudimentary range checks but does not
explicitly check that both fields of TPMT_HA actually fit within the buffer
size limits.

Introduce a new function 'tpm2_resolve_name' to address all the possible
out-of-range issues, and in addition do handle type validation.

Cc: stable@vger.kernel.org # v6.10+
Fixes: d0a25bb961e6 ("tpm: Add HMAC session name/handle append")
Signed-off-by: Jarkko Sakkinen <jarkko@kernel.org>
---
drivers/char/tpm/tpm2-cmd.c | 95 ++++++++++++++++++++++++++++++++
drivers/char/tpm/tpm2-sessions.c | 78 +-------------------------
include/linux/tpm.h | 2 +
3 files changed, 98 insertions(+), 77 deletions(-)

diff --git a/drivers/char/tpm/tpm2-cmd.c b/drivers/char/tpm/tpm2-cmd.c
index e63254135a74..d51272573004 100644
--- a/drivers/char/tpm/tpm2-cmd.c
+++ b/drivers/char/tpm/tpm2-cmd.c
@@ -11,8 +11,11 @@
* used by the kernel internally.
*/

+#include "linux/dev_printk.h"
+#include "linux/tpm.h"
#include "tpm.h"
#include <crypto/hash_info.h>
+#include <linux/unaligned.h>

static bool disable_pcr_integrity;
module_param(disable_pcr_integrity, bool, 0444);
@@ -769,3 +772,95 @@ int tpm2_find_cc(struct tpm_chip *chip, u32 cc)

return -1;
}
+
+/**
+ * tpm2_name_size() - Resolve size of a TPMT_HA instance
+ * @name: Pointer to TPMT_HA structure extracted from TPM2B_NAME.
+ *
+ * Calculate size of the TPMT_HA payload of TPM2B_NAME. It is used with
+ * transient keys, persistent and NV indexes.
+ *
+ * Returns zero when the hash size was successfully calculated.
+ * Returns -EINVAL when the hash algorithm was not recognized.
+ */
+int tpm2_name_size(const u8 *name)
+{
+ u16 hash_alg = get_unaligned_be16(name);
+
+ switch (hash_alg) {
+ case TPM_ALG_SHA1:
+ return SHA1_DIGEST_SIZE + 2;
+ case TPM_ALG_SHA256:
+ return SHA256_DIGEST_SIZE + 2;
+ case TPM_ALG_SHA384:
+ return SHA384_DIGEST_SIZE + 2;
+ case TPM_ALG_SHA512:
+ return SHA512_DIGEST_SIZE + 2;
+ case TPM_ALG_SM3_256:
+ return SM3256_DIGEST_SIZE + 2;
+ }
+
+ return -EINVAL;
+}
+
+/**
+ * tpm2_resolve_name - Resolve TPM object's name from the public area
+ * @handle: Persistent, transient or nv handle.
+ *
+ * Returns zero on success.
+ * Returns -EINVAL when handles are not of valid type.
+ * Returns -EIO if the transmission fails or response is malformed.
+ */
+int tpm2_resolve_name(struct tpm_chip *chip, u32 handle, void *name)
+{
+ u32 mso = tpm2_handle_mso(handle);
+ off_t offset = TPM_HEADER_SIZE;
+ int name_size, name_size_2;
+ struct tpm_buf buf;
+ int rc;
+
+ if (mso != TPM2_MSO_PERSISTENT && mso != TPM2_MSO_VOLATILE &&
+ mso != TPM2_MSO_NVRAM)
+ return -EINVAL;
+
+ rc = tpm_buf_init(&buf, TPM2_ST_NO_SESSIONS, TPM2_CC_READ_PUBLIC);
+ if (rc)
+ return rc;
+
+ tpm_buf_append_u32(&buf, handle);
+
+ rc = tpm_transmit_cmd(chip, &buf, 0, "TPM2_ReadPublic");
+ if (rc) {
+ tpm_buf_destroy(&buf);
+ return tpm_ret_to_err(rc);
+ }
+
+ /* Skip TPMT_PUBLIC: */
+ offset += tpm_buf_read_u16(&buf, &offset);
+
+ /*
+ * Ensure space for the length field of TPM2B_NAME and hashAlg field of
+ * TPMT_HA (the extra four bytes).
+ */
+ if (offset + 4 > tpm_buf_length(&buf)) {
+ tpm_buf_destroy(&buf);
+ return -EIO;
+ }
+
+ name_size = tpm_buf_read_u16(&buf, &offset);
+ name_size_2 = tpm2_name_size(&buf.data[offset]);
+
+ if (name_size != name_size_2) {
+ tpm_buf_destroy(&buf);
+ return -EIO;
+ }
+
+ if (offset + name_size > tpm_buf_length(&buf)) {
+ tpm_buf_destroy(&buf);
+ return -EIO;
+ }
+
+ memcpy(name, &buf.data[offset], name_size);
+ return 0;
+}
+EXPORT_SYMBOL_GPL(tpm2_resolve_name);
diff --git a/drivers/char/tpm/tpm2-sessions.c b/drivers/char/tpm/tpm2-sessions.c
index 82b9d9096fd1..7c85333d47c4 100644
--- a/drivers/char/tpm/tpm2-sessions.c
+++ b/drivers/char/tpm/tpm2-sessions.c
@@ -140,82 +140,6 @@ struct tpm2_auth {
u8 name[AUTH_MAX_NAMES][2 + SHA512_DIGEST_SIZE];
};

-#ifdef CONFIG_TCG_TPM2_HMAC
-
-/*
- * Calculate size of the TPMT_HA payload of TPM2B_NAME.
- */
-static int tpm2_name_size(const u8 *name)
-{
- u16 hash_alg = get_unaligned_be16(name);
-
- switch (hash_alg) {
- case TPM_ALG_SHA1:
- return SHA1_DIGEST_SIZE + 2;
- case TPM_ALG_SHA256:
- return SHA256_DIGEST_SIZE + 2;
- case TPM_ALG_SHA384:
- return SHA384_DIGEST_SIZE + 2;
- case TPM_ALG_SHA512:
- return SHA512_DIGEST_SIZE + 2;
- case TPM_ALG_SM3_256:
- return SM3256_DIGEST_SIZE + 2;
- }
-
- return -EINVAL;
-}
-
-static int tpm2_parse_read_public(char *name, struct tpm_buf *buf)
-{
- struct tpm_header *head = (struct tpm_header *)buf->data;
- off_t offset = TPM_HEADER_SIZE;
- u32 tot_len = be32_to_cpu(head->length);
- int name_size_alg;
- u32 val;
-
- /* we're starting after the header so adjust the length */
- tot_len -= TPM_HEADER_SIZE;
-
- /* skip public */
- val = tpm_buf_read_u16(buf, &offset);
- if (val > tot_len)
- return -EINVAL;
- offset += val;
- /* name */
-
- val = tpm_buf_read_u16(buf, &offset);
- name_size_alg = tpm2_name_size(&buf->data[offset]);
- if (name_size_alg < 0)
- return name_size_alg;
-
- if (val != name_size_alg)
- return -EINVAL;
-
- memcpy(name, &buf->data[offset], val);
- /* forget the rest */
- return 0;
-}
-
-static int tpm2_read_public(struct tpm_chip *chip, u32 handle, char *name)
-{
- struct tpm_buf buf;
- int rc;
-
- rc = tpm_buf_init(&buf, TPM2_ST_NO_SESSIONS, TPM2_CC_READ_PUBLIC);
- if (rc)
- return rc;
-
- tpm_buf_append_u32(&buf, handle);
- rc = tpm_transmit_cmd(chip, &buf, 0, "read public");
- if (rc == TPM2_RC_SUCCESS)
- rc = tpm2_parse_read_public(name, &buf);
-
- tpm_buf_destroy(&buf);
-
- return rc;
-}
-#endif /* CONFIG_TCG_TPM2_HMAC */
-
/**
* tpm_buf_append_name() - add a handle area to the buffer
* @chip: the TPM chip structure
@@ -272,7 +196,7 @@ int tpm_buf_append_name(struct tpm_chip *chip, struct tpm_buf *buf,
mso == TPM2_MSO_VOLATILE ||
mso == TPM2_MSO_NVRAM) {
if (!name) {
- ret = tpm2_read_public(chip, handle, auth->name[slot]);
+ ret = tpm2_resolve_name(chip, handle, auth->name[slot]);
if (ret)
return tpm_ret_to_err(ret);
}
diff --git a/include/linux/tpm.h b/include/linux/tpm.h
index 1a59f0190eb3..727e6c26feeb 100644
--- a/include/linux/tpm.h
+++ b/include/linux/tpm.h
@@ -477,6 +477,8 @@ extern int tpm_pcr_extend(struct tpm_chip *chip, u32 pcr_idx,
extern int tpm_get_random(struct tpm_chip *chip, u8 *data, size_t max);
extern struct tpm_chip *tpm_default_chip(void);
void tpm2_flush_context(struct tpm_chip *chip, u32 handle);
+int tpm2_name_size(const u8 *name);
+int tpm2_resolve_name(struct tpm_chip *chip, u32 handle, void *name);

static inline void tpm_buf_append_empty_auth(struct tpm_buf *buf, u32 handle)
{
--
2.52.0