% JSON Domain Format as Implemented by Pdns-Pipe-Nmc This document is based on [Namecoin Domain Name Specification](https://wiki.namecoin.info/index.php?title=Domain_Name_Specification). It tries to follow it closely, and clarify parts that are not specified, or specified ambiguously, in the original document. One notable deviation is the specification of `"delegate"` and `"import"` attributes: domain objects to which their value point are replacing/merging to the domain object in which they are defined. This seems to be in line with at least one existing "real world" implementation. This specification is implemented by the `pdns-pipe-nmc` program. ## Data Format ### `DomObj` Object `DomObj` is a data structure that is associated with an FQDN. It is either a `String` containing a dotted quad (see Note below), or a JSON `Map`, with the following attributes, all optional: | Key | Type | Comment | |-------------|---------------------------------------|--------------------------------------------| | service | Array(SrvObj) | Located two levels above position | | ip | Array(String) | Dotted quad format "1.2.3.4" | | ip6 | Array(String) | Semicolon format "DEAD::BEEF" | | tor | String | Onion name | | i2p | I2pObj | | | freenet | String | | | alias | String | Nullifies other attributes | | translate | String | Nullifies the "map" attribute | | email | String | Used in `SOA` | | loc | String | Format suitable for `LOC` | | info | JsonObj | Currently unspecified | | ns | Array(String) | Domain names as in `NS` | | delegate | String | Replaces current object | | import | Array(String) | "Deep" merges into current object | | map | Map(String:DomObj) | Tree of subdomain objects | | fingerprint | Array(String) | | | tls | Map(String:Map(String:Array(TlsObj))) | Outer `Map` by `Protocol`, inner by `Port` | | ds | Array(DsObj) | | #### Notes: * Any attribute specified as `Array(String)` may be present in the JSON document as a plain `String`, which is interpreted the same way as an `Array` containing a single `String` element. In other words, `"ip":"1.2.3.4"` is equivalent to `"ip":["1.2.3.4"]`. (This does not apply to non-string-array attributes, like "service" or "ds".) * If `DomObj` is a `String`, it is interpreted as an IPv4 address. In other words, string `"1.2.3.4"` is the same as the Map `"{\"ip\":\"1.2.3.4\"}"`. Such "shorthand" DomObj can be present at the top level or as a value in the `"map"` attribute. ### `SrvObj` Object `SrvObj` is a heterogenous Array of fixed size containing 6 elements: | N | Type | Meaning | |---|--------|----------| | 0 | String | Service | | 1 | String | Protocol | | 2 | Int | Priority | | 3 | Int | Weight | | 4 | Int | Port | | 5 | String | FQDN | #### Notes * `Service` and `Protocol` are two elements of the domain name, without the undescore '_'. * `SrvObj` with Service `"smtp"`, Protocol `"tcp"` and Port `25` is also interpteted as an `MX` DNS resource at the domain level containing the `"service"` object. * When lookup is performed for `SRV` records at fqdn `"_serv._proto.sub.dom.bit"`, domain object for `"sub.dom.bit"` must be fetched, and in this object, `SrvObj`s for the Service `"serv"` and Protocol `"proto"` selected from its `"service"` attribute. ### `TlsObj` Object `TlsObj` is a heterogenous Array of fixed size containing 3 elements: | N | Type | Meaning | |---|--------|-------------------------------------------------------| | 0 | Int | Match type - 0:Exact, 1:SHA-256, 2:SHA-512 | | 1 | String | Match value - certificate or hash of it as hex string | | 2 | Int | Include subdomains - 0:No, 1:Yes | #### Notes * The fields of the object correspond to the attributes defined by [RFC-6698](http://tools.ietf.org/html/rfc6698) ("DANE"). ### `DsObj` Object `DsObj` is a heterogenous Array of fixed size containing 4 elements: | N | Type | Meaning | |---|--------|--------------------------| | 0 | Int | Key Tag | | 1 | Int | Key Algorithm | | 2 | Int | Hash Type | | 3 | String | Hash Value as hex string | #### Notes * The fields of the object correspond to the attributes defined by [RFC-3658](http://tools.ietf.org/html/rfc3658). ## Data Interpretation ### Semantics of the Attributes #### service attribute Translates to DNS `SRV` RR, only it is located in the subdomain tree two levels higher than the `SRV` record would. For example, a `"service"` attribute in the `"map"` hieararchy at the point corresponding to the FQDN "sub.dom.bit" with the value ``` "service": [ ["imap", "tcp", 0, 0, 143, "mail.host.com" ], ["smtp", "tcp", 0, 0, 25, "relay.host.com"] ] ``` corresponds to two `SRV` RRs at two different points in the subdomain tree: ``` _imap._tcp.sub.dom.bit. IN SRV 0 0 143 mail.host.com. _smtp._tcp.sub.dom.bit. IN SRV 0 0 25 relay.host.com. ``` In addition to these, an `MX` RR is syntesized at the "sub.dom.bit" level: ``` sub.dom.bit. IN MX 0 relay.host.com. ``` Note: Hostname element **must** be specified as fully qualified domain name of the host, and **must not** terminate with a dot. This requirement seems to be in line with many existing definitions in the blockchain; however it deviates from the BIND zone file format, in which names that have not terminating dot are automatically expanded by attaching the current origin zone to the end of the name. #### ip attribute Contains a list of strings representing IPv4 addresses in dotted quad notation. For example, ``` "ip": ["1.2.3.4", "5.6.7.8"] ``` translates into a series of `A` RRs: ``` IN A 1.2.3.4 IN A 5.6.7.8 ``` #### ip6 attribute Contains a list of strings representing IPv6 addresses in semicolon quads notation. For example, ``` "ip6": ["2001:4860:0:1001::68"] ``` translates into one AAAA RR: ``` IN AAAA 2001:4860:0:1001::68 ``` #### tor attribute Does not translate into any DNS RR. Contains Tor hidden service address. ``` "tor": "eqt5g4fuenphqinx.onion" ``` #### i2p attribute Does not translate into any DNS RR. It is a JSON Map with three optional String attributes: `"destination"`, `"name"` and `"b32"`. ``` "i2p": { "destination": "XaZscx...0jGAAAA" , "name": "example.i2p" , "b32" : "ukeu...nkdq.b32.i2p" } ``` #### freenet attribute Does not translate into any DNS RR. Contains Freesite key. ``` "freenet": "USK@0I8g...xbZ4,AQACAAE/Example/42/" ``` #### alias attribute Translates into `CNAME` RR. Invalidates all other attributes. ``` "alias": "realhost.example.bit" ``` Notes: * Hostname **must** be specified as fully qualified domain name of the host, and **must not** terminate with a dot. * Element of the `"map"` with empty key, `"delegate"` and `"import"` are processed before this invalidation takes place. #### translate attribute Translates into `DNAME` RR. Invalidates the contents of the `"map"` attribute. ``` "translate": "otherhost.bit" ``` Notes: * Hostname **must** be specified as fully qualified domain name of the host, and **must not** terminate with a dot. * Element of the `"map"` with empty key, `"delegate"` and `"import"` are processed before this invalidation takes place. #### email attribute Translates into the `email` element of the SOA and RP RRs. The value `"email":"user@domain.tld"` becomes `user.domain.tld.` in the DNS record. ``` "email": "hostmaster@example.bit" ``` #### loc attribute Translates into `LOC` RR. Value must conform to the format defined by [RFC-1876](http://tools.ietf.org/html/rfc1876). ``` "loc": "46 31 18.000 N 6 34 26.000 E 401.00m 1m 10000m 10m" ``` #### info attribute Does not translate into any DNS RR. Contains a JSON object with format unspecified at the time of this writing. Intented for the registrant information. #### ns attribute Translates into `NS` RR. Because it effectively delegates all control over the domain to external nameservers, it also invalidates all other attributes. ``` "ns": ["ns.myserver.net", "192.168.3.4"] ``` Notes: * Hostname **must** be specified as fully qualified domain name of the host, and **must not** terminate with a dot. * Element of the `"map"` with empty key, `"delegate"` and `"import"` are processed before this invalidation takes place. #### delegate attribute Does not translate into any DNS RR. Instead, the value is used as a key for namecoin lookup (i.e. the value must be specified with the namespace prefix), and the result of the lookup replaces all other attributes ``` "delegate": "s/example74845" ``` Notes: * Element of the `"map"` with empty key, `"delegate"` and `"import"` are processed before this invalidation takes place. * Unlike many other attributes, this can only contain a single string as the value, rather than a list. #### import attribute Does not translate into any DNS RR. Instead, the value is used as the key for namecoin lookup (i.e. the value must be specified with the namespace prefix), and the result of the lookup is merged with the current domain object. ``` "import": ["dd/example", "s/example6473"] ``` #### map attribute JSON Map object containing subdomain names as its keys and domain objects as values. Element of the map with empty key "" has special meaning: the value of this map element is merged into the current domain object. This operaton happens first when a new domain object is analyzed, and is performed recursively. In the result of the merge, the `"map"` does not contain the element with empty key. Further operatons that can potentially modify the contents of the current domain object (`import` and `delegate` lookups) start when the empty element of the `"map"` has been recursively merged into the current object. ``` "map": { "www": { "alias" : "www.example.com" } , "www2": { "delegate": "d/example" } } ``` Note: When a key contains dots ".", it is converted to a nested map. If empty element appears as a result of split, such as when a dot is at the beginning or at the end of the key, or there are consequitive dots, such elemets are ignored. For example, ``` "map": { "www.uk": { "alias" : "www.example.co.uk" } , "www..us": { "alias" : "www.example.com" } , "smtp.us.": { "alias" : "smtp.example.com" } ``` is equivalent to ``` "map": { "uk": { "map": { "www": { "alias" : "www.example.co.uk" }}} , "us": { "map": { "www": { "alias" : "www.example.com" } , "smtp": { "alias" : "smtp.example.com" }} } } ``` #### fingerprint attribute Does not translate into any DNS RR. Contains a list of TLS certificate fingerprints. Deprecated. #### tls attribute Intended to carry attributes as per [RFC-6698](http://tools.ietf.org/html/rfc6698) ("DANE"). ``` "tls": { "tcp": { { "443": [ [1, "660008F9...7621B787", 1] ] , "25": [ [1, "660008F9...7621B787", 1] ] } } } ``` translates into: ``` _443._tcp TLSA (3 0 1 660008F9...7621B787) _25._tcp TLSA (3 0 1 660008F9...7621B787) ``` The third element of the `TlsObj` heterogenous array is an extention to the DANE definition. Value `0` means that this rule is not enforced upon subdomains, value `1` means that it is enforced on subdomains. Rule defined inside a subdomain `DomObj` that specifies `0` on a rule existing in upper domain, that specifies `1` should be ignored. I.e. subdomain rule cannot revoke enforcement imposed by an upper domain rule. #### ds attribute Translates into `DS` RR. Carries attributes defined by [RFC-4034](http://tools.ietf.org/html/rfc4034). ``` "ds": [ [31381,8,1,"pA1W...ceTI="] , [31381,8,2,"toHB...ndexitQ6j8E="] ] ``` ### Lookup Sequence Assuming a query is performed for `sdN`++"."++{...}++"."++`sd2`++"."++`sd1`++"."++`dom`++".bit" (`sdX` list possibly being empty), the lookup process starts by querying the database for the object corresponding to `dom`. Technically, it is easiest to populate a "seed" DomObj with a single attribute `"import"` the value of which corresponds to the `dom` name in the Namecoin namespace, which is `"d/" ++ dom`. This domain object is then transformed by the following recursive sequece: 1. Value of the element of the `"map"` attribute with the key `""` (empty string) is recursively merged into the base domain. The `""` element of the `"map"` is removed from the result. 2. If attribute `"delegate"` does not exist in the resulting object, step 3 is is performed. If attribute `"delegate"` exists, in the resulting object, lookup is performed for the values of this attribute, and fetched object replaces the base domain completely. The result is passed as base domain to step 1. 3. If attribute `"import"` does not exist in the resulting object, recursion stops, and step 4 is performed on the result If attribute `"import"` exists in the resulting object, lookup is performed for the values of this attribute, and fetched objects are recursively merged into the base domain. The `"import"` attribute is removed from the result. Then the result is passed as base domain to step 1. 4. If subdomain chain is empty, recursion stops, and step 5 is performed on the result. If subdomain chain is not empty, next element is taken out of the chain, and the `"map"` is looked up for the element with the name matching the subdomain element. The value of this element of the `"map"` is passed as base domain to step 1. If matching element does not exist, lookup is considered failed. 5. Domain object in which all `""` map elements and all `"delegate"` and `"import"` elements are acted upon and removed, is then "normalized" by removal of attributes that are nullified by the presence of other attributes. Note that the process involves recursion nested levels deep. ### Merging Procedure When a domain object `extra` needs merging into a domain object `base`, the following rules are applied: * Of `String` and other "scalar" attributes, one is chosen, the value from the `base` taking precedence. * On `Array` attribtes, `union` operation is performed. (Of equal elements, only one copy is left.) * On `Map` attributes, recursive merge is performed. On the top level, elemens with keys that are only present in either `base` or `extra` object are all put into result. The values of the elements that are present in both `base` and `extra` objects are merged according to the rules applicable to their type.