[tor-bugs] #17387 [Tor]: ExtraRelayDescriptorFields needs proposal number

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#17387: ExtraRelayDescriptorFields needs proposal number
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     Reporter:  virgil  |      Owner:
         Type:  task    |     Status:  new
     Priority:  Medium  |  Milestone:
    Component:  Tor     |    Version:
     Severity:  Normal  |   Keywords:
Actual Points:          |  Parent ID:
       Points:          |    Sponsor:
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 {{{
 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

 }}}

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Ticket URL: <https://trac.torproject.org/projects/tor/ticket/17387>
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