[PATCH v5 08/17] KEYS: trusted: tpm2: Use struct tpm_buf for sized buffers

James Bottomley
2023-11-27T19:12:28Z

From: Jarkko Sakkinen <jarkko@kernel.org>

Take advantage of the new sized buffer (TPM2B) mode of struct tpm_buf in
tpm2_seal_trusted(). This allows to add robustness to the command
construction without requiring to calculate buffer sizes manually.

Signed-off-by: Jarkko Sakkinen <jarkko@kernel.org>
Signed-off-by: James Bottomley <James.Bottomley@HansenPartnership.com>
---
security/keys/trusted-keys/trusted_tpm2.c | 54 +++++++++++++----------
1 file changed, 31 insertions(+), 23 deletions(-)

diff --git a/security/keys/trusted-keys/trusted_tpm2.c b/security/keys/trusted-keys/trusted_tpm2.c
index bc700f85f80b..97b1dfca2dba 100644
--- a/security/keys/trusted-keys/trusted_tpm2.c
+++ b/security/keys/trusted-keys/trusted_tpm2.c
@@ -228,8 +228,9 @@ int tpm2_seal_trusted(struct tpm_chip *chip,
struct trusted_key_payload *payload,
struct trusted_key_options *options)
{
+ off_t offset = TPM_HEADER_SIZE;
+ struct tpm_buf buf, sized;
int blob_len = 0;
- struct tpm_buf buf;
u32 hash;
u32 flags;
int i;
@@ -258,6 +259,14 @@ int tpm2_seal_trusted(struct tpm_chip *chip,
return rc;
}

+ rc = tpm_buf_init_sized(&sized);
+ if (rc) {
+ tpm_buf_destroy(&buf);
+ tpm_put_ops(chip);
+ return rc;
+ }
+
+ tpm_buf_reset(&buf, TPM2_ST_SESSIONS, TPM2_CC_CREATE);
tpm_buf_append_u32(&buf, options->keyhandle);
tpm2_buf_append_auth(&buf, TPM2_RS_PW,
NULL /* nonce */, 0,
@@ -266,36 +275,36 @@ int tpm2_seal_trusted(struct tpm_chip *chip,
TPM_DIGEST_SIZE);

/* sensitive */
- tpm_buf_append_u16(&buf, 4 + options->blobauth_len + payload->key_len);
+ tpm_buf_append_u16(&sized, options->blobauth_len);

- tpm_buf_append_u16(&buf, options->blobauth_len);
if (options->blobauth_len)
- tpm_buf_append(&buf, options->blobauth, options->blobauth_len);
+ tpm_buf_append(&sized, options->blobauth, options->blobauth_len);

- tpm_buf_append_u16(&buf, payload->key_len);
- tpm_buf_append(&buf, payload->key, payload->key_len);
+ tpm_buf_append_u16(&sized, payload->key_len);
+ tpm_buf_append(&sized, payload->key, payload->key_len);
+ tpm_buf_append(&buf, sized.data, sized.length);

/* public */
- tpm_buf_append_u16(&buf, 14 + options->policydigest_len);
- tpm_buf_append_u16(&buf, TPM_ALG_KEYEDHASH);
- tpm_buf_append_u16(&buf, hash);
+ tpm_buf_reset_sized(&sized);
+ tpm_buf_append_u16(&sized, TPM_ALG_KEYEDHASH);
+ tpm_buf_append_u16(&sized, hash);

/* key properties */
flags = 0;
flags |= options->policydigest_len ? 0 : TPM2_OA_USER_WITH_AUTH;
- flags |= payload->migratable ? 0 : (TPM2_OA_FIXED_TPM |
- TPM2_OA_FIXED_PARENT);
- tpm_buf_append_u32(&buf, flags);
+ flags |= payload->migratable ? 0 : (TPM2_OA_FIXED_TPM | TPM2_OA_FIXED_PARENT);
+ tpm_buf_append_u32(&sized, flags);

/* policy */
- tpm_buf_append_u16(&buf, options->policydigest_len);
+ tpm_buf_append_u16(&sized, options->policydigest_len);
if (options->policydigest_len)
- tpm_buf_append(&buf, options->policydigest,
- options->policydigest_len);
+ tpm_buf_append(&sized, options->policydigest, options->policydigest_len);

/* public parameters */
- tpm_buf_append_u16(&buf, TPM_ALG_NULL);
- tpm_buf_append_u16(&buf, 0);
+ tpm_buf_append_u16(&sized, TPM_ALG_NULL);
+ tpm_buf_append_u16(&sized, 0);
+
+ tpm_buf_append(&buf, sized.data, sized.length);

/* outside info */
tpm_buf_append_u16(&buf, 0);
@@ -312,21 +321,20 @@ int tpm2_seal_trusted(struct tpm_chip *chip,
if (rc)
goto out;

- blob_len = be32_to_cpup((__be32 *) &buf.data[TPM_HEADER_SIZE]);
- if (blob_len > MAX_BLOB_SIZE) {
+ blob_len = tpm_buf_read_u32(&buf, &offset);
+ if (blob_len > MAX_BLOB_SIZE || buf.flags & TPM_BUF_BOUNDARY_ERROR) {
rc = -E2BIG;
goto out;
}
- if (tpm_buf_length(&buf) < TPM_HEADER_SIZE + 4 + blob_len) {
+ if (buf.length - offset < blob_len) {
rc = -EFAULT;
goto out;
}

- blob_len = tpm2_key_encode(payload, options,
- &buf.data[TPM_HEADER_SIZE + 4],
- blob_len);
+ blob_len = tpm2_key_encode(payload, options, &buf.data[offset], blob_len);

out:
+ tpm_buf_destroy(&sized);
tpm_buf_destroy(&buf);

if (rc > 0) {
--
2.35.3