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Offline Verification

Danger

Because --offline disables trust root updates, sigstore-python falls back to the latest cached trust root or, if none exists, the trust root baked into sigstore-python itself. Like with any other offline verification, this means that users may miss trust root changes (such as new root keys, or revocations) unless they separately keep the trust root up-to-date.

Users who need to operationalize offline verification may wish to do this by distributing their own trust configuration; see Custom root of trust.

During verification, there are two kinds of network access that sigstore-python can perform:

  1. When verifying against "detached" materials (e.g. separate .crt and .sig files), sigstore-python can perform an online transparency log lookup.
  2. By default, during all verifications, sigstore-python will attempt to refresh the locally cached root of trust via a TUF update.

When performing bundle verification (i.e. .sigstore or .sigstore.json), (1) does not apply. However, (2) can still result in online accesses.

To perform fully offline verification, pass --offline to your sigstore verify subcommand:

$ sigstore verify identity foo.txt \
    --offline \
    --cert-identity 'hamilcar@example.com' \
    --cert-oidc-issuer 'https://github.com/login/oauth'

Alternatively, users may choose to bypass TUF entirely by passing an entire trust configuration to sigstore-python via --trust-config:

$ sigstore --trust-config public.trustconfig.json verify identity ...

This will similarly result in fully offline operation, as the trust configuration contains a full trust root.