Authenticated Dat URLs and HTTPS to Dat Discovery

Beaker needs a mechanism by which users can securely deploy a site at a domain, eg dat://beakerbrowser.com. Ideally, this mechanism will allow discovery and automatic redirection; for instance, if the user browses to https://beakerbrowser.com, they should be prompted to redirect to dat://beakerbrowser.com.

Requirements

1. MUST provide a single canonical Dat URL for the domain. It should not be possible for multiple Dats to be specified within a domain. This means the Dat must be specified by a single fixed file, or by DNS.
2. MUST not be controllable by non-owners of the domain. It should not be possible for user-input or injections to set the Dat URL.
3. MUST cryptographically authenticate the validity of the entry.
4. SHOULD be accessible to as many users as possible (eg response headers are frequently unsettable).

Options

DNS

Satisfies requirement 1 and 2, fails requirement 3, not ideal for requirement 4. DNSSEC could be used to satisfy requirement 3, but support for DNSSEC by gTLDs is limited.

HTML tags (eg meta)

Satisfies requirements 3 (with HTTPS) and 4, fails requirements 1 and 2.

.Well-known file over TLS

Satisfies requirements 1, 2, 3, and 4.

Discussion

https://github.com/beakerbrowser/beaker/issues/227

https://github.com/beakerbrowser/beaker/issues/228

Proposal

Place a file at /.well-known/dat with the following schema:

{dat-url}
TTL={time in seconds}

TTL is optional and will default to 3600 (one hour). If set to 0, the entry is not cached.

Dat-name Resolution

Resolution of a site at dat://hostname will occur with the following process:

• Browser checks its dat names cache. If a non-expired entry is found, return with the entry.
• Browser issues a GET request to https://hostname/.well-known/dat.
• If the server responds with a 404 Not Found status, store a null entry in the cache with a TTL of 3600 and return a failed lookup.
• If the server responds with anything other than a 200 OK status, return a failed lookup.
• If the server responds with a malformed file, return a failed lookup.
• If the response includes no TTL, set to default 3600.
• If the response includes a non-zero TTL, store the entry in the dat-name cache.
• Return the entry.

Discovery

Visits to sites served over HTTPS should trigger Dat-name Resolution. If an entry is found, the browser UI will present the user with an option to redirect to the Dat site. Discovery traffic will be throttled by the Dat-name caching.

Possible variations

Dat sites use the dat.json file to confer metadata. See https://beakerbrowser.com/docs/apis/manifest.html. The schema includes a standard url field. This could be used as an alternative to /.well-known/dat, though it would probably lack the TTL (unless we choose to add it).