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167 lines
3.2 KiB
Plaintext
167 lines
3.2 KiB
Plaintext
Wire Protocol (version 1)
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The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
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"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
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document are to be interpreted as described in RFC 2119 [RFC2119].
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LLARP supports by default an authenticated message transport over a
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datagram based network layer.
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outer message format:
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{
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A: command,
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B: <16 bytes flow id>,
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C: <optional 32 bytes cookie>,
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X: <N bytes payload>
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}
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comamnds:
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A - get handshake cookie
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obtain a handshake cookie
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B is randomized
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X MUST contain the user agent string of the requester.
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the if the network id differs from the current network's id a reject message is
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sent:
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{
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A: R,
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B: msg.B,
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X: "<reply line>"
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}
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MUST be replied to with a message rejected or a give handshake cookie
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C - give handshake cookie
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give a handshake cookie to a remote endpoint that asks for one
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B is the B value from the get handshake cookie message
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X is a 32 byte handshake cookie, calcuated via:
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r = RAND(32)
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a = "<ascii representation of ip>" + " " + "<port number>"
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X = HS(a + B + r)
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R - message rejected
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B is the flow id from the recipiant
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X is a reply line
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reject a message with flow id B
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S - session negotiation
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negotiate encrypted session
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B is the flow id from the recipiant
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C is the handshake cookie
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X is encrypted session negotiation data
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D - encrypted data transmission
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transmit encrypted data on session
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B is the flow id from the recipiant
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X is authenticated and encrypted data
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BNF:
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<reply-line> ::= <status-code> <space> <method> <space> <message>
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<status-code> ::= <integer> <digit> <digit>
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<word> ::= <letter>+
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<message> ::= <word> <space> <word>* | <word>
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<method> ::= "COOKIE" | "HANDSHAKE"
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<user-agent> ::= <net-id> <space> <protocol-version> <space> <agent-version>
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<net-id> ::= "lokinet" | "testnet"
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<space> ::= " "
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<zero> ::= "0"
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<integer> ::= "1" | "2" | "3" | "4" | "5" | "6" | "7" | "8" | "9"
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<digit> ::= <zero> | <integer>
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<number> ::= <zero> | <integer> <digit>*
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<agent-version> ::= <number> "." <number> "." <number>
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<protocol-version> ::= <number>
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session negotiation:
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The session starts out with each side having 2 session keys rx_K and tx_K for
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decrypting inbound messages and encrypting outbound messages respectively.
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The initiator (alice) and the recipiant (bob) start out with static session keys
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k_a = HS(a.k)
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k_b = HS(b.k)
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a.rx_K = k_a
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b.rx_K = k_b
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a.tx_K = k_b
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b.tx_K = k_a
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inner message format:
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<32 bytes blake2s keyed hash of following data>
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<24 bytes nounce>
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<remaining bytes encrypted payload>
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decryption is done via:
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SD(remaining, rx_K, nounce)
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encrypted payload is bencoded LIM (see proto_v0.txt)
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the initiator starts out by sending a LIM a_LIM to the recipiant.
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the recipiant replies with a LIM b_LIM to the initiator.
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when the initiator gets a valid LIM from the recipiant the session keys for data
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transmission are set to:
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k_a = TKE(a.k, b.k, a.sk, a_LIM.n)
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k_b = TKE(b.k, a.k, b.sk, b_LIM.n)
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a.rx_K = k_a
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b.rx_K = k_b
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a.tx_K = k_b
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b.tx_K = k_a
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afterwards data transmission may happen
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data tranmission:
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message format:
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<10 byte header>
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<remaining data payload>
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header format:
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<1 byte proto version>
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<1 byte command>
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<1 byte flags>
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<1 byte fragno>
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<2 bytes fraglen>
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<4 bytes seqno>
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