在解析rlpx时出现lua错误

在帧列表中，有一个帧（编号 1561）出现了 Lua 错误。具体来说，错误信息是：“Lua Error: /root/local/lib/wireshark/plugins/rlpx.lua:97: attempt to index local ‘dec_msg’ (a nil value)”。在解码器脚本 rlpx.lua 的第 97 行尝试访问一个名为 dec_msg 的局部变量，但它是一个空值（nil），导致解码器无法成功解析数据包

img

img

rlpx.lua代码如下，lua版本为Lua 5.4.7 ：

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
local python = require 'python'

-- Temporary for development
-- local sys = python.import 'sys'
-- sys.path.append('/home/jkemp/cs700/pydevp2p/')
-- End of Temporary for development

local rlpxBridge = python.import 'pydevp2p.bridge'

-- create a new dissector
local NAME = "rlpx"
local PORT = 30305
local rlpx = Proto(NAME, "Ethereum RLPx Protocol")

local fields = rlpx.fields
fields.auth_size = ProtoField.uint16(NAME .. ".auth_size", "Auth Size")
fields.ack_size = ProtoField.uint16(NAME .. ".ack_size", "Ack Size")
fields.body = ProtoField.bytes(NAME .. ".body", "Data")
fields.frame_header = ProtoField.bytes(NAME .. ".frame_header", "Frame Header")
fields.frame_body = ProtoField.bytes(NAME .. ".frame_body", "Frame Body")

local known_ports = { 30303, 30304, 30305, 30306, 30307, 30308 }

local function table_has_value(tab, val)
    for _, value in ipairs(tab) do
        if value == val then
            return true
        end
    end

    return false
end

local function array_iterator(array, len)
    -- This lets us iterate over a c object (like a python array)
    local index = 0
    local count = len

    -- The closure function is returned

    return function()
        index = index + 1

        if index <= count
        then
            -- return the current element of the iterator
            return array[index]
        end

    end
end

-- main dissect packet function
function rlpx.dissector(tvb, pinfo, tree)
    local subtree = tree:add(rlpx, tvb())
    local offset = 0

    -- show protocol name in protocol column
    pinfo.cols.protocol = rlpx.name

    local srcaddr = tostring(pinfo.src)
    local dstaddr = tostring(pinfo.dst)

    local payload = tostring(tvb:bytes())

    -- dissect field one by one, and add to protocol tree
    local auth_size = tvb(offset, 2)
    if (tvb:len() - auth_size:int() == 2) then
        if (table_has_value(known_ports, pinfo.src_port)) then
            -- This is most likely a handshake AUTH-ACK packet
            offset = offset + 2
            subtree:add(fields.ack_size, auth_size)
            pinfo.cols.info:set(pinfo.src_port .. " → " .. pinfo.dst_port .. " [HANDSHAKE] AUTH ACK")
            -- print(payload, dstNode)
            local dec_msg = rlpxBridge.handleRLPxHandshakeMsg(srcaddr, dstaddr, payload, pinfo.visited, pinfo.number)
            local payloadtree = subtree:add(fields.body, tvb(offset))
            payloadtree:set_text("Handshake AUTH ACK")
            for element in array_iterator(dec_msg, dec_msg[0]) do
                payloadtree:add(element)
            end
        elseif (table_has_value(known_ports, pinfo.dst_port)) then
            -- This is most likely a handshake AUTH packet
            offset = offset + 2
            subtree:add(fields.auth_size, auth_size)
            pinfo.cols.info:set(pinfo.src_port .. " → " .. pinfo.dst_port .. " [HANDSHAKE] AUTH INIT")
            -- print(payload, dstNode)
            local dec_msg = rlpxBridge.handleRLPxHandshakeMsg(srcaddr, dstaddr, payload, pinfo.visited, pinfo.number)
            local payloadtree = subtree:add(fields.body, tvb(offset))
            for element in array_iterator(dec_msg, dec_msg[0]) do
                payloadtree:add(element)
            end
        else
            subtree:add(fields.body, tvb(offset))
        end
    else
        local dec_msg = rlpxBridge.handleRLPxMsg(srcaddr, dstaddr, payload, pinfo.visited, pinfo.number)
        local frame_header = dec_msg[0]
        local frame_body = dec_msg[1]
        local frame_type = dec_msg[2]
        -- Set the column information to the Frame Type
        if frame_type ~= nil then
            pinfo.cols.info:set(pinfo.src_port .. " → " .. pinfo.dst_port .. " " .. frame_type)
        end
        -- Show the frame header information (if available) in Wireshark
        if frame_header ~= nil then
            local frame_header_tree = subtree:add(fields.frame_header, tvb(0, frame_header.headerSize))
            frame_header_tree:add("Decrypted Header Data:", frame_header.header)
            frame_header_tree:add("Header MAC:", frame_header.headerMac)
            frame_header_tree:add("Frame Body MAC:", frame_header.frameMac)
            frame_header_tree:add("Frame Size:", frame_header.frameSize)
            frame_header_tree:add("Read Size:", frame_header.readSize)
            frame_header_tree:add("Header Data:", frame_header.headerData)
            pinfo.cols.info:append(" Len=" .. frame_header.readSize)
        end
        -- Show the frame body information (if available) in Wireshark
        if frame_header ~= nil and frame_type ~= nil and frame_body ~= nil and frame_body[0] > 0 then
            local frame_body_tree = subtree:add(fields.frame_body, tvb(frame_header.headerSize))
            for element in array_iterator(frame_body, frame_body[0]) do
                frame_body_tree:add(element)
            end
        end
    end
end

-- register this dissector
DissectorTable.get("tcp.port"):add(PORT, rlpx)
DissectorTable.get("tcp.port"):add("30303", rlpx)
DissectorTable.get("tcp.port"):add("30304", rlpx)
DissectorTable.get("tcp.port"):add("30305", rlpx)
DissectorTable.get("tcp.port"):add("30306", rlpx)
DissectorTable.get("tcp.port"):add("30307", rlpx)
DissectorTable.get("tcp.port"):add("30308", rlpx)

不知道怎么改，不懂lua

可能是lua版本问题，改天看下文档

img

img

img