keys/trusted/tpm2: Validate TPM2_Create object sizes separately

TPM2_Create returns outPrivate, outPublic, creationData, creationHash and
creationTicket in its response parameter area. However, only outPrivate and
outPublic are included in the trusted key blob. The size of the blob is
therefore not determined by the size of the complete response parameter
area.

tpm2_seal_trusted() currently compares the size of the complete response
parameter area against MAX_BLOB_SIZE. This can reject a valid response
when the remaining response outputs cause the entire response parameter
area to exceed MAX_BLOB_SIZE, even though the outPrivate and outPublic
TPM2B structures consumed by tpm2_key_encode() remain small enough to be
encoded in the key blob.

This is observed when creating larger trusted keys using the swtpm TPM 2.0
emulator backed by libtpms.

For example, requesting a 113-byte key succeeds, 114 fails.

~$ keyctl add trusted trusted_key1 "new 113 keyhandle=0x81000001" @u
520504613
~$ keyctl add trusted trusted_key2 "new 114 keyhandle=0x81000001" @u
add_key: Argument list too long
~$

Remove the MAX_BLOB_SIZE check on the complete response parameter area.
Instead, use the response length passed to tpm2_key_encode() to validate
that the outPrivate and outPublic TPM2B structures are fully contained
in the response before accessing them.

Previously, a response parameter area larger than MAX_BLOB_SIZE was
rejected with -E2BIG before ASN.1 encoding. With this change, if the
resulting encoded blob does not fit in payload->blob, the error returned by
asn1_encode_sequence() is propagated instead.

Also, use scope-based cleanup to simplify resource management.

Signed-off-by: Srish Srinivasan <ssrish@linux.ibm.com>
Link: https://lore.kernel.org/r/20260926184203.479203-1-ssrish@linux.ibm.com
Reviewed-by: Jarkko Sakkinen <jarkko@kernel.org>
Signed-off-by: Jarkko Sakkinen <jarkko@kernel.org>

0 files changed, 0 insertions, 0 deletions