The JSON evidence is allocated on the module instance heap, but no API
was given to dispose of this memory buffer. The sample mentions using
the function free, which behaves differently depending on the
execution context.
This fix provides a new function called librats_dispose_evidence_json,
enabling freeing the JSON evidence directly from the Wasm app.
The current implementation of remote attestation does not take into
account the integrity of the wasm module. The SHA256 of the wasm
module has been put into user_data to generate the quote, and more
parameters are exposed for further verification.
