169 lines
6.4 KiB
Lua
169 lines
6.4 KiB
Lua
function hasbit(x, p)
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return x % (p + p) >= p
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end
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tsdebug_ll = Proto("tsdebug", "Tailscale debug")
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PATH = ProtoField.string("tsdebug.PATH","PATH", base.ASCII)
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SNAT_IP_4 = ProtoField.ipv4("tsdebug.SNAT_IP_4", "Pre-NAT Source IPv4 address")
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SNAT_IP_6 = ProtoField.ipv4("tsdebug.SNAT_IP_6", "Pre-NAT Source IPv6 address")
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DNAT_IP_4 = ProtoField.ipv4("tsdebug.DNAT_IP_4", "Pre-NAT Dest IPv4 address")
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DNAT_IP_6 = ProtoField.ipv4("tsdebug.DNAT_IP_6", "Pre-NAT Dest IPv6 address")
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tsdebug_ll.fields = {PATH, SNAT_IP_4, SNAT_IP_6, DNAT_IP_4, DNAT_IP_6}
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function tsdebug_ll.dissector(buffer, pinfo, tree)
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pinfo.cols.protocol = tsdebug_ll.name
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packet_length = buffer:len()
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local offset = 0
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local subtree = tree:add(tsdebug_ll, buffer(), "Tailscale packet")
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-- -- Get path UINT16
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local path_id = buffer:range(offset, 2):le_uint()
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if path_id == 0 then subtree:add(PATH, "FromLocal")
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elseif path_id == 1 then subtree:add(PATH, "FromPeer")
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elseif path_id == 2 then subtree:add(PATH, "Synthesized (Inbound / ToLocal)")
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elseif path_id == 3 then subtree:add(PATH, "Synthesized (Outbound / ToPeer)")
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elseif path_id == 254 then subtree:add(PATH, "Disco frame")
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end
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offset = offset + 2
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-- -- Get SNAT address
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local snat_addr_len = buffer:range(offset, 1):le_uint()
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if snat_addr_len == 4 then subtree:add(SNAT_IP_4, buffer:range(offset + 1, snat_addr_len))
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elseif snat_addr_len > 0 then subtree:add(SNAT_IP_6, buffer:range(offset + 1, snat_addr_len))
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end
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offset = offset + 1 + snat_addr_len
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-- -- Get DNAT address
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local dnat_addr_len = buffer:range(offset, 1):le_uint()
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if dnat_addr_len == 4 then subtree:add(DNAT_IP_4, buffer:range(offset + 1, dnat_addr_len))
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elseif dnat_addr_len > 0 then subtree:add(DNAT_IP_6, buffer:range(offset + 1, dnat_addr_len))
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end
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offset = offset + 1 + dnat_addr_len
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-- -- Handover rest of data to lower-level dissector
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local data_buffer = buffer:range(offset, packet_length-offset):tvb()
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if path_id == 254 then
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Dissector.get("tsdisco"):call(data_buffer, pinfo, tree)
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else
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Dissector.get("ip"):call(data_buffer, pinfo, tree)
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end
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end
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-- Install the dissector on link-layer ID 147 (User-defined protocol 0)
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local eth_table = DissectorTable.get("wtap_encap")
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eth_table:add(wtap.USER0, tsdebug_ll)
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local ts_dissectors = DissectorTable.new("ts.proto", "Tailscale-specific dissectors", ftypes.STRING, base.NONE)
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--
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-- DISCO metadata dissector
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--
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tsdisco_meta = Proto("tsdisco", "Tailscale DISCO metadata")
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DISCO_IS_DERP = ProtoField.bool("tsdisco.IS_DERP","From DERP")
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DISCO_SRC_IP_4 = ProtoField.ipv4("tsdisco.SRC_IP_4", "Source IPv4 address")
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DISCO_SRC_IP_6 = ProtoField.ipv4("tsdisco.SRC_IP_6", "Source IPv6 address")
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DISCO_SRC_PORT = ProtoField.uint16("tsdisco.SRC_PORT","Source port", base.DEC)
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DISCO_DERP_PUB = ProtoField.bytes("tsdisco.DERP_PUB", "DERP public key", base.SPACE)
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tsdisco_meta.fields = {DISCO_IS_DERP, DISCO_SRC_PORT, DISCO_DERP_PUB, DISCO_SRC_IP_4, DISCO_SRC_IP_6}
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function tsdisco_meta.dissector(buffer, pinfo, tree)
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pinfo.cols.protocol = tsdisco_meta.name
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packet_length = buffer:len()
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local offset = 0
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local subtree = tree:add(tsdisco_meta, buffer(), "DISCO metadata")
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-- Parse flags
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local from_derp = hasbit(buffer(offset, 1):le_uint(), 0)
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subtree:add(DISCO_IS_DERP, from_derp) -- Flag bit 0
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offset = offset + 1
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-- Parse DERP public key
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if from_derp then
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subtree:add(DISCO_DERP_PUB, buffer(offset, 32))
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end
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offset = offset + 32
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-- Parse source port
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subtree:add(DISCO_SRC_PORT, buffer:range(offset, 2):le_uint())
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offset = offset + 2
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-- Parse source address
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local addr_len = buffer:range(offset, 2):le_uint()
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offset = offset + 2
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if addr_len == 4 then subtree:add(DISCO_SRC_IP_4, buffer:range(offset, addr_len))
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else subtree:add(DISCO_SRC_IP_6, buffer:range(offset, addr_len))
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end
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offset = offset + addr_len
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-- Handover to the actual disco frame dissector
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offset = offset + 2 -- skip over payload len
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local data_buffer = buffer:range(offset, packet_length-offset):tvb()
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Dissector.get("disco"):call(data_buffer, pinfo, tree)
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end
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ts_dissectors:add(1, tsdisco_meta)
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--
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-- DISCO frame dissector
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--
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tsdisco_frame = Proto("disco", "Tailscale DISCO frame")
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DISCO_TYPE = ProtoField.string("disco.TYPE", "Message type", base.ASCII)
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DISCO_VERSION = ProtoField.uint8("disco.VERSION","Protocol version", base.DEC)
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DISCO_TXID = ProtoField.bytes("disco.TXID", "Transaction ID", base.SPACE)
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DISCO_NODEKEY = ProtoField.bytes("disco.NODE_KEY", "Node key", base.SPACE)
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DISCO_PONG_SRC = ProtoField.ipv6("disco.PONG_SRC", "Pong source")
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DISCO_PONG_SRC_PORT = ProtoField.uint16("disco.PONG_SRC_PORT","Source port", base.DEC)
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DISCO_UNKNOWN = ProtoField.bytes("disco.UNKNOWN_DATA", "Trailing data", base.SPACE)
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tsdisco_frame.fields = {DISCO_TYPE, DISCO_VERSION, DISCO_TXID, DISCO_NODEKEY, DISCO_PONG_SRC, DISCO_PONG_SRC_PORT, DISCO_UNKNOWN}
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function tsdisco_frame.dissector(buffer, pinfo, tree)
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packet_length = buffer:len()
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local offset = 0
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local subtree = tree:add(tsdisco_frame, buffer(), "DISCO frame")
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-- Message type
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local message_type = buffer(offset, 1):le_uint()
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offset = offset + 1
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if message_type == 1 then subtree:add(DISCO_TYPE, "Ping")
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elseif message_type == 2 then subtree:add(DISCO_TYPE, "Pong")
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elseif message_type == 3 then subtree:add(DISCO_TYPE, "Call me maybe")
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end
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-- Message version
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local message_version = buffer(offset, 1):le_uint()
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offset = offset + 1
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subtree:add(DISCO_VERSION, message_version)
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-- TXID (Ping / Pong)
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if message_type == 1 or message_type == 2 then
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subtree:add(DISCO_TXID, buffer(offset, 12))
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offset = offset + 12
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end
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-- NodeKey (Ping)
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if message_type == 1 then
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subtree:add(DISCO_NODEKEY, buffer(offset, 32))
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offset = offset + 32
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end
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-- Src (Pong)
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if message_type == 2 then
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subtree:add(DISCO_PONG_SRC, buffer:range(offset, 16))
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offset = offset + 16
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end
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-- Src port (Pong)
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if message_type == 2 then
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subtree:add(DISCO_PONG_SRC_PORT, buffer(offset, 2):le_uint())
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offset = offset + 2
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end
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-- TODO(tom): Parse CallMeMaybe.MyNumber
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local trailing = buffer:range(offset, packet_length-offset)
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if trailing:len() > 0 then
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subtree:add(DISCO_UNKNOWN, trailing)
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end
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end
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ts_dissectors:add(2, tsdisco_frame) |