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reproducibility.md

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Reproducibility

The ledger application is running in a trusted execution environment and has a measurement associated with it which does not change. The goal is to reproduce the same measured value from the source code to ensure the code can be trusted, transparent and auditable.

The assumption here is that the original build was done using a Docker.

Prerequisites

You need a couple pieces of information to begin with:

  • The ledger certificate. It might be distributed in a variety of ways by the ledger operator, please follow their guidance. Otherwise it is accessible at https://<LEDGER-URL>/app/parameters.

  • The quote of a running application code, get it from https://<LEDGER-URL>/node/quotes/self (replace with the URL of your ledger), e.g.:

    $ curl -s --cacert cacert.pem https://<LEDGER-URL>/node/quotes/self > node-quote.json

  • Source code version which was used to build the application, usually found in https://<LEDGER-URL>/app/version. If app/version is ambiguous then check the build logs of the Docker image to understand which commit produced the candidate value. e.g., fb2c496416fbab20837fedda0ba6db58d819fa5f5c1b3916062eb2fb9d889966 was built from fd77c0c69ee890bdc2fcf6ef0c9dddb7b211e164.

    $ curl -s --cacert cacert.pem https://<LEDGER-URL>/app/version | jq ".version"
"1.2.3"

Extract measurements

The quote contains the attestation report that has the necessary measurements. Measurement will have the launch measurement of the guest virtual machine (aka utility VM or UVM) which was used to run the container. Host data will have the security policy measurement which was used to make sure no other container was launched except the one you are inspecting. More detail on implementing relying party logic can be found in Confidential ACI scheme documentation.

  • Decode the report and save it to a file:

    cat node-quote.json | jq -r '.raw' | base64 -d > snp-report.bin

  • Inspect the report to get the measurements. You could use https://github.com/virtee/snpguest to display the report details:

    snpguest display report snp-report.bin

Reproduce measurements

Guest VM

Guest VM measurements can be authenticated using platform endorsements. To get platform endorsements:

cat node-quote.json | jq -r '.uvm_endorsements' | base64 -d > uvm_endorsements.cose

The details of how to reproduce the Guest VM (to compare it to a measurement in the report) are not ready yet.

Security policy and container image

Host data contains the hash of the security policy, but we do not have the steps to obtain the policy yet. Container image would be linked to the policy.