====================================== Addressbook Subscription Feed Commands ====================================== .. meta:: :author: zzz :created: 2014-09-15 :thread: http://zzz.i2p/topics/1704 :lastupdated: 2016-04-17 :status: Open .. contents:: Overview ======== This proposal is about extending the address subscription feed with commands, to enable name servers to broadcast entry updates from hostname holders. Motivation ========== Right now, the hosts.txt subscription servers just send data in a hosts.txt format, which is as follows:: foo.i2p=b64destination There are several problems with this: - Hostname holders cannot update the Destination associated with their hostnames (in order to e.g. upgrade the signing key to a stronger type). - Hostname holders cannot relinquish their hostnames arbitrarily; they must give the corresponding Destination private keys directly to the new holder. - There is no way to authenticate that a subdomain is controlled by the corresponding base hostname; this is currently only enforced individually by some name servers. Design ====== This proposal adds a number of command lines to the hosts.txt format. With these commands, name servers can extend their services to provide a number of additional features. Clients that implement this proposal will be able to listen for these features through the regular subscription process. All command lines must be signed by the corresponding Destination. This ensures that changes are only made at the request of the hostname holder. Security implications ===================== This proposal has no implications on anonymity. There is an increase in the risk associated with losing control of a Destination key, as someone who obtains it can use these commands to make changes to any associated hostnames. But this is no more of a problem than the status quo, where someone who obtains a Destination can impersonate a hostname and (partially) take over its traffic. The increased risk is also balanced our by giving hostname holders the ability to change the Destination associated with a hostname, in the event that they believe the Destination has been compromised; this is impossible with the current system. Specification ============= New line types -------------- This proposal adds two new types of lines: 1. Add and Change commands:: foo.i2p=b64destination#!key1=val1#key2=val2 ... 2. Remove commands:: #!key1=val1#key2=val2 ... Ordering ```````` A feed is not necessarily in-order or complete. For example, a change command may be on a line before an add command, or without an add command. Keys may be in any order. Duplicate keys are not allowed. All keys and values are case-sensitive. Common keys ----------- Required in all commands: sig B64 signature, using signing key from the destination References to a second hostname and/or destination: oldname A second hostname (new or changed) olddest A second b64 destination (new or changed) oldsig A second b64 signature, using signing key from nolddest Other common keys: action A command name The hostname, only present if not preceded by name=dest dest The b64 destination, only present if not preceded by name=dest date In seconds since epoch expires In seconds since epoch Commands -------- All commands except the "Add" command must contain an "action=command" key/value. For compatibility with older clients, most commands are preceded by name=dest, as noted below. For changes, these are always the new values. Any old values are included in the key/value section. Listed keys are required. All commands may contain additional key/value items not defined here. Add hostname ```````````` Preceded by name=dest YES, this is the new host name and destination. action NOT included, it is implied. sig signature Example:: name=dest#!sig=b64sig Change hostname ``````````````` Preceded by name=dest YES, this is the new host name and old destination. action changename oldname the old hostname, to be replaced sig signature Example:: name=dest#!action=changename#oldname=oldhostname#sig=b64sig Change destination `````````````````` Preceded by name=dest YES, this is the old host name and new destination. action changedest olddest the old dest, to be replaced oldsig signature using olddest sig signature Example:: name=dest#!action=changedest#olddest=oldb64dest#oldsig=b64sig#sig=b64sig Add hostname alias `````````````````` Preceded by name=dest YES, this is the new (alias) host name and old destination. action addname oldname the old hostname sig signature Example:: name=dest#!action=addname#oldname=oldhostname#sig=b64sig Add destination alias ````````````````````` (Used for crypto upgrade) Preceded by name=dest YES, this is the old host name and new (alternate) destination. action adddest olddest the old dest oldsig signature using olddest sig signature using dest Example:: name=dest#!action=adddest#olddest=oldb64dest#oldsig=b64sig#sig=b64sig Add subdomain ````````````` Preceded by name=dest YES, this is the new host subdomain name and destination. action addsubdomain oldname the old hostname, unchanged olddest the old dest, unchanged oldsig signature using olddest sig signature using dest Example:: name=dest#!action=addsubdomain#oldname=oldhostname#olddest=oldb64dest#oldsig=b64sig#sig=b64sig Update metadata ``````````````` Preceded by name=dest YES, this is the old host name and destination. action update sig signature (add any updated keys here) Example:: name=dest#!action=update#k1=v1#k2=v2#sig=b64sig Remove hostname ``````````````` Preceded by name=dest NO, these are specified in the options action remove name the hostname dest the destination sig signature Example:: #!action=removeall#name=hostname#dest=b64destsig=b64sig Remove all with this destination ```````````````````````````````` Preceded by name=dest NO, these are specified in the options action removeall name the old hostname, advisory only dest the old dest, all with this dest are removed sig signature Example:: #!action=removeall#name=hostname#dest=b64destsig=b64sig Signatures ---------- All commands must contain a signature key/value "sig=b64signature" where the signature for the other data, using the destination signing key. For commands including an old and new destination, there must also be an oldsig=b64signature, and either oldname, olddest, or both. In an Add or Change command, the public key for verification is in the Destination to be added or changed. In some add or edit commands, there may be an additional destination referenced, for example when adding an alias, or changing a destination or host name. In that case, there must be a second signature included and both should be verified. The second signature is the "inner" signature and is signed and verified first (excluding the "outer" signature). The client should take any additional action necessary to verify and accept changes. oldsig is always the "inner" signature. Sign and verify without the 'oldsig' or 'sig' keys present. sig is always the "outer" signature. Sign and verify with the 'oldsig' key present but not the 'sig' key. Input for signatures ```````````````````` To generate a byte stream to create or verify the signature, serialize as follows: - Remove the "sig" key - If verifying with oldsig, also remove the "oldsig" key - For Add or Change commands: - output name=b64dest (name must be lower-case) - If any keys remain, output "#!" - Sort the options by UTF-8 key, fail if duplicate keys - For each key/value, output key=value, followed by (if not the last key/value) a '#' - Do not output a newline - Output encoding is UTF-8 Compatibility ============= All new lines in the hosts.txt format are implemented using leading comment characters, so all older I2P versions will interpret the new commands as comments. When I2P routers update to the new specification, they will not re-interpret old comments, but will start listening to new commands in subsequent fetches of their subscription feeds. Thus it is important for name servers to persist command entries in some fashion, or enable etag support so that routers can fetch all past commands.