`bao operator init` fails at the seal with CKR_MECHANISM_INVALID. The
pkcs11 seal asks for AES-GCM by default and the TPM does not offer it: a
TPM 2.0's symmetric modes are CBC/CFB/CTR/OFB/ECB, and openbao accepts
only AEAD mechanisms — AES-GCM or RSA-OAEP — so RSA-OAEP is the single
mechanism both sides implement.
Measured on the deployed token (`pkcs11-tool --list-mechanisms`, #3860):
no AES-GCM, and `RSA-PKCS-OAEP, keySize={1024,2048}, hw, encrypt,
decrypt` present. CBC is not a fallback — openbao's
`MechanismFromString` rejects `CKM_AES_CBC_PAD` as deprecated and its
encrypt path implements exactly the two AEAD mechanisms.
The key gets a new label so a store provisioned by the earlier module
keeps its unusable AES key without the two resolving to one label, and
the addkey step is now keyed on the label rather than on the store not
existing — otherwise an existing deployment never gains the RSA key.
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