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Fairdice Protocol v0.3 : Negotiation : Client-Server

Letter Name Description
M Mode Negotiate the encryption and authentication mode
R Remote Remote tunneling to connect User and Host
V Version Negotiate which version of the protocol to use
[Definition]
NEGOTIATION_MESSAGE = ("M " MODE_STR) | ("R " REMOTE_STR) | ("V " VERSION_STR)
; these are defined in this file

Mode

[Definition]
MODE_STR = ENCRYPTION_MODE | ENCRYPTION_TYPE | AUTHENTICATION_MODE | AUTHENTICATION_TYPE | ENCODING_MODE | ENCODING_TYPE
ENCRYPTION_MODE = "encryption mode " MODE_ORDER [ " " ENCRYPTION_NAME ]
ENCRYPTION_TYPE = "encryption type " ENCRYPTION_NAME OPAQUE
; In this case OPAQUE is a method specific argument
AUTHENTICATION_MODE = "authentication mode " MODE_ORDER [ " " AUTHENTICATION_NAME ]
AUTHENTICATION_TYPE = "authentication type " AUTHENTICATION_NAME OPAQUE
ENCODING_MODE = "encoding mode " MODE_ORDER [ " " ENCODING_NAME ]
ENCODING_TYPE = "encoding type " ENCODING_NAME OPAQUE
ENCRYPTION_NAME = <a short text string, identifying a particular encryption system>
; the only method named so far is "none"
AUTHENTICATION_NAME = <a short text string, identifying a particular authentication system>
; the only system named so far is "pass"
ENCODING_NAME = <a short text string, identifying a particular encoding system>
; the only method named so far is "ascii-hex"
MODE_ORDER = "require " | "confirm " | "failure"

[Sequence]
A mode negotiation happens after version sequence and before description. It only happens once.

The sequence of orders for each aspect is:

  1. mode require X
  2. mode confirm X
  3. type X foo
  4. type X bar
  5. ...
or
  1. mode require X
  2. mode failure
(in which case the connection fails)

[Example]
SERVER --> CLIENT   M encryption mode require none
CLIENT --> SERVER   M encryption mode confirm none
SERVER --> CLIENT   M authentication mode require pass
CLIENT --> SERVER   M authentication mode confirm pass
CLIENT --> SERVER   M authentication type pass NAME=WilliamGladstone
CLIENT --> SERVER   M authentication type pass PASS=CantGuess
CLIENT --> SERVER   M authentication type pass HOST=Harry.Com
SERVER --> CLIENT   M encoding mode require ascii-hex
CLIENT --> SERVER   M encoding mode confirm ascii-hex

Remote

[Definition]
REMOTE_STR = OPAQUE_STR

[Sequence]
A remote string may be sent or received any time after version and mode negotiation.

The opaque data is sent and received, unedited.

[Example]
  USER1 --> CLIENT1   R localhost:22201 ^ Harry.Com | [CHAT] Hi Steve, want to play a game?
CLIENT1 --> SERVER    R [CHAT] Hi Ben, want to play a game?
 SERVER --> HOST      R WilliamGladstone | [CHAT] Hi Ben, want to play a game?
   HOST --> SERVER    R BenjaminDisraeli | [CHAT] Bill says: Hi Ben, want to play a game?
 SERVER --> CLIENT2   R [CHAT] Bill says: Hi Ben, want to play a game?
CLIENT2 --> USER2     R localhost:22201 ^ Harry.Com | [CHAT] Bill says: Hi Ben, want to play a game?

Version

[Definition]
VERSION_STR = VERSION_REQUEST | VERSION_OFFER | VERSION_SELECT | VERSION_DECLINE | VERSION_ACCEPT
VERSION_REQUEST = "request"
VERSION_OFFER = "offer " VERSION_RANGE
VERSION_SELECT = "select " VERSION_NUMBER
VERSION_DECLINE = "decline " VERSION_NUMBER
VERSION_ACCEPT = "accept " VERSION_NUMBER
VERSION_RANGE = INT_RANGE
VERSION_NUMBER = SMALLINT

[Sequence]
The version sequence happens once, immediately after the link open sequence.

The version sequence will be initiated by the party initiating the connection.

It finishes either successfully with a selection being accepted or unsuccessfully, with the link being closed after an offer is not responded to (because the app understands none of the versions on offer). 

          X   may follow   Y

none              :   VERSION_REQUEST
VERSION_REQUEST   :   VERSION_OFFER
none              :   VERSION_OFFER
VERSION_OFFER     :   none
VERSION_OFFER     :   VERSION_SELECT
none              :   VERSION_SELECT
VERSION_SELECT    :   VERSION_ACCEPT
VERSION_ACCEPT    :   none
VERSION_SELECT    :   VERSION_DECLINE
VERSION_DECLINE   :   VERSION_SELECT
VERSION_DECLINE   :   VERSION_REQUEST

[Example]
CLIENT --> SERVER   V select 1
SERVER --> CLIENT   V decline 1
CLIENT --> SERVER   V request
SERVER --> CLIENT   V offer 2,4-7
CLIENT --> SERVER   V select 2
SERVER --> CLIENT   V accept 2

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