This EIP defines a resolver profile for ENS that provides features for storage and lookup of DNS records. This allows ENS to be used as a store of authoritative DNS information.
ENS is a highly desirable store for DNS information. It provides the distributed authority of DNS without conflating ownership and authoritative serving of information. With ENS, the owner of a domain has full control over their own DNS records. Also, ENS has the ability (through smart contracts) for a domain's subdomains to be irrevocably assigned to another entity.
The resolver profile to support DNS on ENS follows the resolver specification as defined in ERC-137.
Traditionally, DNS is a zone-based system in that all of the records for a zone are kept together in the same file. This has the benefit of simplicity and atomicity of zone updates, but when transposed to ENS can result in significant gas costs for simple changes. As a result, the resolver works on the basis of record sets. A record set is uniquely defined by the tuple (domain, name, resource record type), for example the tuple (example.com, www.example.com, A) defines the record set of A records for the name www.example.com in the domain example.com. A record set can contain 0 or more values, for example if www.example.com has A records 1.2.3.4 and 5.6.7.8 then the aforementioned tuple will have two values.
The choice to work at the level of record sets rather than zones means that this specification cannot completely support some features of DNS, such as zone transfers and DNSSEC. It would be possible to build a different resolver profile that works at the zone level, however it would be very expensive to carry out updates and so is not considered further for this EIP.
The DNS resolver interface consists of two functions to set DNS information and two functions to query DNS information.
setDNSRecords() sets, updates or clears 1 or more DNS records for a given node. It has function signature 0x0af179d7.
The arguments for the function are as follows:
clearDNSZone() removes all DNS records for the domain. It has function signature 0xad5780af.
Although it is possible to clear records individually with setDNSRecords() as described above this requires the owner to know all of the records that have been set (as the resolver has no methods to iterate over the records for a given domain), and might require multiple transactions. clearDNSZone() removes all zone information in a single operation.
The arguments for the function is as follows:
dnsRecords() obtains the DNS records for a given node, name and resource. It has function signature 0x2461e851.
The arguments for the function are as follows:
keccak256() hash of the name of the record in DNS wire format.The function returns all matching records in DNS wire format. If there are no records present the function will return nothing.
hasDNSRecords() reports if there are any records for the provided name in the domain. It has function signature 0x4cbf6ba4.
This function is needed by DNS resolvers when working with wildcard resources as defined in RFC4592.
The arguments for the function are as follows:
keccak256() hash of the name of the record in DNS wire format.The function returns true if there are any records for the provided node and name, otherwise false.
DNS is a federated system of naming, and the higher-level entities control availability of everything beneath them (e.g. .org controls the availability of ethereum.org). A decentralized version of DNS would not have this constraint, and allow lookups directly for any domain with relevant records within ENS.
Not applicable.
The reference implementation of the DNS resolver is as follows:
Security of this solution would be dependent on security of the records within the ENS domain. This degenenrates to the security of the key(s) which have authority over that domain.
Copyright and related rights waived via CC0.