[PATCH v3 2/3] tpm: Address !chip->auth in tpm_buf_append_name()

Jarkko Sakkinen
2024-07-04T08:57:34Z

Unless tpm_chip_bootstrap() was called by the driver, !chip->auth can
cause a null derefence in tpm_buf_append_name(). Thus, address
!chip->auth in tpm_buf_append_name() and remove the fallback
implementation for !TCG_TPM2_HMAC.

Cc: stable@vger.kernel.org # v6.10+
Reported-by: Stefan Berger <stefanb@linux.ibm.com>
Closes: https://lore.kernel.org/linux-integrity/20240617193408.1234365-1-stefanb@linux.ibm.com/
Fixes: d0a25bb961e6 ("tpm: Add HMAC session name/handle append")
Signed-off-by: Jarkko Sakkinen <jarkko@kernel.org>
---
v3:
* Address:
https://lore.kernel.org/linux-integrity/922603265d61011dbb23f18a04525ae973b83ffd.camel@HansenPartnership.com/
v2:
* N/A
---
drivers/char/tpm/Makefile | 2 +-
drivers/char/tpm/tpm2-sessions.c | 217 +++++++++++++++++--------------
include/linux/tpm.h | 14 +-
3 files changed, 121 insertions(+), 112 deletions(-)

diff --git a/drivers/char/tpm/Makefile b/drivers/char/tpm/Makefile
index 4c695b0388f3..9bb142c75243 100644
--- a/drivers/char/tpm/Makefile
+++ b/drivers/char/tpm/Makefile
@@ -16,8 +16,8 @@ tpm-y += eventlog/common.o
tpm-y += eventlog/tpm1.o
tpm-y += eventlog/tpm2.o
tpm-y += tpm-buf.o
+tpm-y += tpm2-sessions.o

-tpm-$(CONFIG_TCG_TPM2_HMAC) += tpm2-sessions.o
tpm-$(CONFIG_ACPI) += tpm_ppi.o eventlog/acpi.o
tpm-$(CONFIG_EFI) += eventlog/efi.o
tpm-$(CONFIG_OF) += eventlog/of.o
diff --git a/drivers/char/tpm/tpm2-sessions.c b/drivers/char/tpm/tpm2-sessions.c
index 2f1d96a5a5a7..179bcaac06ce 100644
--- a/drivers/char/tpm/tpm2-sessions.c
+++ b/drivers/char/tpm/tpm2-sessions.c
@@ -83,9 +83,6 @@
#define AES_KEY_BYTES AES_KEYSIZE_128
#define AES_KEY_BITS (AES_KEY_BYTES*8)

-static int tpm2_create_primary(struct tpm_chip *chip, u32 hierarchy,
- u32 *handle, u8 *name);
-
/*
* This is the structure that carries all the auth information (like
* session handle, nonces, session key and auth) from use to use it is
@@ -148,6 +145,7 @@ struct tpm2_auth {
u8 name[AUTH_MAX_NAMES][2 + SHA512_DIGEST_SIZE];
};

+#ifdef CONFIG_TCG_TPM2_HMAC
/*
* Name Size based on TPM algorithm (assumes no hash bigger than 255)
*/
@@ -163,6 +161,120 @@ static u8 name_size(const u8 *name)
return size_map[alg] + 2;
}

+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);
+ 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);
+ if (val != name_size(&buf->data[offset]))
+ 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
+ * @buf: The buffer to be appended
+ * @handle: The handle to be appended
+ * @name: The name of the handle (may be NULL)
+ *
+ * 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
+ * the actual 4 byte handle or an empty buf (in these cases @name
+ * should be NULL) but for volatile objects, permanent objects and NV
+ * areas, the name is defined as the hash (according to the name
+ * algorithm which should be set to sha256) of the public area to
+ * which the two byte algorithm id has been appended. For these
+ * objects, the @name pointer should point to this. If a name is
+ * required but @name is NULL, then TPM2_ReadPublic() will be called
+ * on the handle to obtain the name.
+ *
+ * As with most tpm_buf operations, success is assumed because failure
+ * will be caused by an incorrect programming model and indicated by a
+ * kernel message.
+ */
+void tpm_buf_append_name(struct tpm_chip *chip, struct tpm_buf *buf,
+ u32 handle, u8 *name)
+{
+ enum tpm2_mso_type __maybe_unused mso = tpm2_handle_mso(handle);
+ struct tpm2_auth __maybe_unused *auth;
+ int __maybe_unused slot;
+
+ if (!__and(IS_ENABLED(CONFIG_TCG_TPM2_HMAC), chip->auth)) {
+ tpm_buf_append_u32(buf, handle);
+ /* count the number of handles in the upper bits of flags */
+ buf->handles++;
+ return;
+ }
+
+#ifdef CONFIG_TCG_TPM2_HMAC
+ slot = (tpm_buf_length(buf) - TPM_HEADER_SIZE) / 4;
+ if (slot >= AUTH_MAX_NAMES) {
+ dev_err(&chip->dev, "TPM: too many handles\n");
+ return;
+ }
+ auth = chip->auth;
+ WARN(auth->session != tpm_buf_length(buf),
+ "name added in wrong place\n");
+ tpm_buf_append_u32(buf, handle);
+ auth->session += 4;
+
+ if (mso == TPM2_MSO_PERSISTENT ||
+ mso == TPM2_MSO_VOLATILE ||
+ mso == TPM2_MSO_NVRAM) {
+ if (!name)
+ tpm2_read_public(chip, handle, auth->name[slot]);
+ } else {
+ if (name)
+ dev_err(&chip->dev, "TPM: Handle does not require name but one is specified\n");
+ }
+
+ auth->name_h[slot] = handle;
+ if (name)
+ memcpy(auth->name[slot], name, name_size(name));
+#endif /* CONFIG_TCG_TPM2_HMAC */
+}
+EXPORT_SYMBOL_GPL(tpm_buf_append_name);
+
+#ifdef CONFIG_TCG_TPM2_HMAC
+
+static int tpm2_create_primary(struct tpm_chip *chip, u32 hierarchy,
+ u32 *handle, u8 *name);
+
/*
* It turns out the crypto hmac(sha256) is hard for us to consume
* because it assumes a fixed key and the TPM seems to change the key
@@ -567,104 +679,6 @@ void tpm_buf_fill_hmac_session(struct tpm_chip *chip, struct tpm_buf *buf)
}
EXPORT_SYMBOL(tpm_buf_fill_hmac_session);

-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);
- 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);
- if (val != name_size(&buf->data[offset]))
- 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;
-}
-
-/**
- * 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)
- *
- * 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
- * the actual 4 byte handle or an empty buf (in these cases @name
- * should be NULL) but for volatile objects, permanent objects and NV
- * areas, the name is defined as the hash (according to the name
- * algorithm which should be set to sha256) of the public area to
- * which the two byte algorithm id has been appended. For these
- * objects, the @name pointer should point to this. If a name is
- * required but @name is NULL, then TPM2_ReadPublic() will be called
- * on the handle to obtain the name.
- *
- * As with most tpm_buf operations, success is assumed because failure
- * will be caused by an incorrect programming model and indicated by a
- * kernel message.
- */
-void tpm_buf_append_name(struct tpm_chip *chip, struct tpm_buf *buf,
- u32 handle, u8 *name)
-{
- enum tpm2_mso_type mso = tpm2_handle_mso(handle);
- struct tpm2_auth *auth = chip->auth;
- int slot;
-
- slot = (tpm_buf_length(buf) - TPM_HEADER_SIZE)/4;
- if (slot >= AUTH_MAX_NAMES) {
- dev_err(&chip->dev, "TPM: too many handles\n");
- return;
- }
- WARN(auth->session != tpm_buf_length(buf),
- "name added in wrong place\n");
- tpm_buf_append_u32(buf, handle);
- auth->session += 4;
-
- if (mso == TPM2_MSO_PERSISTENT ||
- mso == TPM2_MSO_VOLATILE ||
- mso == TPM2_MSO_NVRAM) {
- if (!name)
- tpm2_read_public(chip, handle, auth->name[slot]);
- } else {
- if (name)
- dev_err(&chip->dev, "TPM: Handle does not require name but one is specified\n");
- }
-
- auth->name_h[slot] = handle;
- if (name)
- memcpy(auth->name[slot], name, name_size(name));
-}
-EXPORT_SYMBOL(tpm_buf_append_name);
-
/**
* tpm_buf_check_hmac_response() - check the TPM return HMAC for correctness
* @chip: the TPM chip structure
@@ -1311,3 +1325,4 @@ int tpm2_sessions_init(struct tpm_chip *chip)

return rc;
}
+#endif /* CONFIG_TCG_TPM2_HMAC */
diff --git a/include/linux/tpm.h b/include/linux/tpm.h
index 21a67dc9efe8..d9a6991b247d 100644
--- a/include/linux/tpm.h
+++ b/include/linux/tpm.h
@@ -490,11 +490,13 @@ static inline void tpm_buf_append_empty_auth(struct tpm_buf *buf, u32 handle)
{
}
#endif
-#ifdef CONFIG_TCG_TPM2_HMAC

-int tpm2_start_auth_session(struct tpm_chip *chip);
void tpm_buf_append_name(struct tpm_chip *chip, struct tpm_buf *buf,
u32 handle, u8 *name);
+
+#ifdef CONFIG_TCG_TPM2_HMAC
+
+int tpm2_start_auth_session(struct tpm_chip *chip);
void tpm_buf_append_hmac_session(struct tpm_chip *chip, struct tpm_buf *buf,
u8 attributes, u8 *passphrase,
int passphraselen);
@@ -521,14 +523,6 @@ static inline int tpm2_start_auth_session(struct tpm_chip *chip)
static inline void tpm2_end_auth_session(struct tpm_chip *chip)
{
}
-static inline void tpm_buf_append_name(struct tpm_chip *chip,
- struct tpm_buf *buf,
- u32 handle, u8 *name)
-{
- tpm_buf_append_u32(buf, handle);
- /* count the number of handles in the upper bits of flags */
- buf->handles++;
-}
static inline void tpm_buf_append_hmac_session(struct tpm_chip *chip,
struct tpm_buf *buf,
u8 attributes, u8 *passphrase,
--
2.45.2