[v4,06/11] security: keys: trusted: Verify creation data
Commit Message
If a loaded key contains creation data, ask the TPM to verify that
creation data. This allows users like encrypted hibernate to know that
the loaded and parsed creation data has not been tampered with.
Suggested-by: Matthew Garrett <mjg59@google.com>
Signed-off-by: Evan Green <evgreen@chromium.org>
---
Source material for this change is at:
https://patchwork.kernel.org/project/linux-pm/patch/20210220013255.1083202-9-matthewgarrett@google.com/
(no changes since v3)
Changes in v3:
- Changed funky tag to suggested-by (Kees). Matthew, holler if you want
something different.
Changes in v2:
- Adjust hash len by 2 due to new ASN.1 storage, and add underflow
check.
include/linux/tpm.h | 1 +
security/keys/trusted-keys/trusted_tpm2.c | 77 ++++++++++++++++++++++-
2 files changed, 77 insertions(+), 1 deletion(-)
Comments
On Thu, Nov 03, 2022 at 11:01:14AM -0700, Evan Green wrote:
> If a loaded key contains creation data, ask the TPM to verify that
> creation data. This allows users like encrypted hibernate to know that
> the loaded and parsed creation data has not been tampered with.
>
> Suggested-by: Matthew Garrett <mjg59@google.com>
> Signed-off-by: Evan Green <evgreen@chromium.org>
Reviewed-by: Kees Cook <keescook@chromium.org>
@@ -224,6 +224,7 @@ enum tpm2_command_codes {
TPM2_CC_SELF_TEST = 0x0143,
TPM2_CC_STARTUP = 0x0144,
TPM2_CC_SHUTDOWN = 0x0145,
+ TPM2_CC_CERTIFYCREATION = 0x014A,
TPM2_CC_NV_READ = 0x014E,
TPM2_CC_CREATE = 0x0153,
TPM2_CC_LOAD = 0x0157,
@@ -703,6 +703,74 @@ static int tpm2_unseal_cmd(struct tpm_chip *chip,
return rc;
}
+/**
+ * tpm2_certify_creation() - execute a TPM2_CertifyCreation command
+ *
+ * @chip: TPM chip to use
+ * @payload: the key data in clear and encrypted form
+ * @blob_handle: the loaded TPM handle of the key
+ *
+ * Return: 0 on success
+ * -EINVAL on tpm error status
+ * < 0 error from tpm_send or tpm_buf_init
+ */
+static int tpm2_certify_creation(struct tpm_chip *chip,
+ struct trusted_key_payload *payload,
+ u32 blob_handle)
+{
+ struct tpm_header *head;
+ struct tpm_buf buf;
+ int rc;
+
+ rc = tpm_buf_init(&buf, TPM2_ST_SESSIONS, TPM2_CC_CERTIFYCREATION);
+ if (rc)
+ return rc;
+
+ /* Use TPM_RH_NULL for signHandle */
+ tpm_buf_append_u32(&buf, 0x40000007);
+
+ /* Object handle */
+ tpm_buf_append_u32(&buf, blob_handle);
+
+ /* Auth */
+ tpm_buf_append_u32(&buf, 9);
+ tpm_buf_append_u32(&buf, TPM2_RS_PW);
+ tpm_buf_append_u16(&buf, 0);
+ tpm_buf_append_u8(&buf, 0);
+ tpm_buf_append_u16(&buf, 0);
+
+ /* Qualifying data */
+ tpm_buf_append_u16(&buf, 0);
+
+ /* Creation data hash */
+ if (payload->creation_hash_len < 2) {
+ rc = -EINVAL;
+ goto out;
+ }
+
+ tpm_buf_append_u16(&buf, payload->creation_hash_len - 2);
+ tpm_buf_append(&buf, payload->creation_hash + 2,
+ payload->creation_hash_len - 2);
+
+ /* signature scheme */
+ tpm_buf_append_u16(&buf, TPM_ALG_NULL);
+
+ /* creation ticket */
+ tpm_buf_append(&buf, payload->tk, payload->tk_len);
+
+ rc = tpm_transmit_cmd(chip, &buf, 6, "certifying creation data");
+ if (rc)
+ goto out;
+
+ head = (struct tpm_header *)buf.data;
+
+ if (be32_to_cpu(head->return_code) != TPM2_RC_SUCCESS)
+ rc = -EINVAL;
+out:
+ tpm_buf_destroy(&buf);
+ return rc;
+}
+
/**
* tpm2_unseal_trusted() - unseal the payload of a trusted key
*
@@ -728,8 +796,15 @@ int tpm2_unseal_trusted(struct tpm_chip *chip,
goto out;
rc = tpm2_unseal_cmd(chip, payload, options, blob_handle);
- tpm2_flush_context(chip, blob_handle);
+ if (rc)
+ goto flush;
+
+ if (payload->creation_len)
+ rc = tpm2_certify_creation(chip, payload, blob_handle);
+
+flush:
+ tpm2_flush_context(chip, blob_handle);
out:
tpm_put_ops(chip);