tpm2_import: fix fixed AES key CVE-2021-3565
tpm2_import: fix fixed AES key CVE-2021-3565

tpm2_import used a fixed AES key for the inner wrapper, which means that
a MITM attack would be able to unwrap the imported key. Even the
use of an encrypted session will not prevent this. The TPM only
encrypts the first parameter which is the fixed symmetric key.

To fix this, ensure the key size is 16 bytes or bigger and use
OpenSSL to generate a secure random AES key.

Fixes: #2738

Signed-off-by: William Roberts <60148e894dabf0b83bde1d460768794cd453c455@intel.com>

01org/tpm2.0-tools,01org/tpm2.0-tools,01org/tpm2.0-tools