Sanitize bridge descriptors containing old identity keys
Proposal 230 adds support for relays and bridges to migrate from one identity key to another. A relay or bridge that uses this new feature switches to a new identity key and includes information about its old identity key in its server descriptor.
In particular, the following data will be included:
- old RSA 1024 public identity key (not SHA-1 fingerprint),
- date and time of migration, and
- signature of date and time of migration and new identity key fingerprint, made with old identity key.
Sanitized bridge descriptors need to contain sanitized versions of these new fields. For example, we cannot include the full old public identity key, nor the old public identity key fingerprint. In general, we remove all crypto from sanitized bridge descriptors. Here's a suggestion of what we could include:
"old-rsa1024-id-fingerprint" SP FINGERPRINT SP ISO-TIME NL
We'll want to add support for parsing this field in metrics-lib.