``` Filename: ExtraRelayDescriptorFields.txt Title: Adding X-namespace to extra-info descriptor for key:value pairs Author: Virgil Griffith Created: 2015-09-30 Status: Open 1. Motivation We wish to allow developers to build new applications atop relays. Towards this end, we wish to add the ability for users to specify arbitrary new key-value entries under the "X-" namespace to the extra-info descriptor. The canonical applications for this are adding a bitcoin donation address, networking of tor2web nodes, and display operator information on a Roster[1] page. 2. Proposal Allow optional key-value lines in the relay's torrc file. The following would be added to section 2.1.2 of the dir-spec [2] (Extra-info document format): ======================================================== "X-" CustomKey SP CustomValue NL CustomKeyChar = "a"-"z" / "0" - "9" / "-" / "_" CustomKey = 1*32 CustomKeyChar CustomValueChar = atext / specials CustomValue = 1*1024 CustomValueChar There can be multiple X-fields, for example... X-bitcoin 19mP9FKrXqL46Si58pHdhGKow88SUPy1V8 X-gravatar https://s.gravatar.com/avatar/d27fce46c9ac41a41bb52455ae75701d X-linkedin https://www.linkedin.com/in/virgilgr X-keybase http://fncuwbiisyh6ak3i.onion/virgil X-favoritequote Be excellent to each other. Party on dudes! X-foo bar The same CustomKey appearing more than once is disallowed. Possible values for CustomValueChar as specified per RFC 2822 sections 3.2.1 and 3.2.4 [3]. The sum size accounting for all such custom fields is truncated to 5 kilobytes. ======================================================== To mitigate the chance of a malformed torrc file, I additionally propose that the relay descriptor be scanned and if it does not match the specification, that it exit with error telling her torrc file is a likely culprit. References [1] [http://tor-roster.org](http://tor-roster.org/) [2] https://gitweb.torproject.org/torspec.git/tree/dir-spec.txt#n700 [3] https://www.ietf.org/rfc/rfc2822.txt ```