resolves #859

[ematery]

…rom 0x01c00100 to 0x01c001ff, with the certificates stored concatenated in DER format.

If handles within this specified range are present, the following steps will be executed:

1. The content of all NV handles will be collected into a vector.
2. The content of the vector will be split into individual certificates.
3. Each certificate will be converted to PEM format.
4. The resulting PEM certificate chain will be provided as the 'ek_ca_chain' attribute to the registrar.

I appreciate any feedback, as I have no experience with the Rust programming language.

[ansasaki]

Hello, thank you for your contribution!

The proposed changes require changes to the REST API definition, as well as changes on the Keylime registrar.
Please create an enhancement proposal in https://github.com/keylime/enhancements as this is not a simple change and could affect compatibility.

After the enhancement is discussed and approved the changes to both sides (registrar and agent) can be implemented.

Notice that most probably the proposed change to the registrar will also lead to a change in the database as it will require a new entry where the intermediate certificates would be stored. For this reason, the corresponding alembic database upgrade will also be required.

Sorry for the complex process, but it is the best way we could find to have all the steps reviewed and documented, as well as to reduce the chances of breaking existing users.

[ansasaki]

@ematery Could you please rebase this PR and align to the latest version of the enhancement proposal?

Also, please use a more descriptive title so that we can understand what is the goal of the PR just by reading it.

[ematery]

I screwed up with this pull request and opened a new one #951