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wireshark/test/lua/pcap_file.lua

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-- pcap_file_reader.lua
--------------------------------------------------------------------------------
--[[
This is a Wireshark Lua-based pcap capture file reader.
Author: Hadriel Kaplan
This "capture file" reader reads pcap files - the old style ones. Don't expect this to
be as good as the real thing; this is a simplistic implementation to show how to
create such file readers, and for testing purposes.
This script requires Wireshark v1.12 or newer.
--]]
--------------------------------------------------------------------------------
-- do not modify this table
local debug = {
DISABLED = 0,
LEVEL_1 = 1,
LEVEL_2 = 2
}
-- set this DEBUG to debug.LEVEL_1 to enable printing debug info
-- set it to debug.LEVEL_2 to enable really verbose printing
local DEBUG = debug.LEVEL_1
local wireshark_name = "Wireshark"
if not GUI_ENABLED then
wireshark_name = "Tshark"
end
-- verify Wireshark is new enough
local major, minor, micro = get_version():match("(%d+)%.(%d+)%.(%d+)")
if major and tonumber(major) <= 1 and ((tonumber(minor) <= 10) or (tonumber(minor) == 11 and tonumber(micro) < 3)) then
error( "Sorry, but your " .. wireshark_name .. " version (" .. get_version() .. ") is too old for this script!\n" ..
"This script needs " .. wireshark_name .. "version 1.12 or higher.\n" )
end
-- verify we have the Struct library in wireshark
-- technically we should be able to do this with 'require', but Struct is a built-in
assert(Struct.unpack, wireshark_name .. " does not have the Struct library!")
--------------------------------------------------------------------------------
-- early definitions
-- throughout most of this file I try to pre-declare things to help ease
-- reading it and following the logic flow, but some things just have to be done
-- before others, so this sections has such things that cannot be avoided
--------------------------------------------------------------------------------
-- first some variable declarations for functions we'll define later
local parse_file_header, parse_rec_header, read_common
-- these will be set inside of parse_file_header(), but we're declaring them up here
local default_settings =
{
debug = DEBUG,
corrected_magic = 0xa1b2c3d4,
version_major = 2,
version_minor = 4,
timezone = 0,
sigfigs = 0,
read_snaplen = 0, -- the snaplen we read from file
snaplen = 0, -- the snaplen we use (limited by WTAP_MAX_PACKET_SIZE)
linktype = -1, -- the raw linktype number in the file header
wtap_type = wtap_encaps.UNKNOWN, -- the mapped internal wtap number based on linktype
endianess = ENC_BIG_ENDIAN,
time_precision = wtap_tsprecs.USEC,
rec_hdr_len = 16, -- default size of record header
rec_hdr_patt = "I4 I4 I4 I4", -- pattern for Struct to use
num_rec_fields = 4, -- number of vars in pattern
}
local dprint = function() end
local dprint2 = function() end
local function reset_debug()
if default_settings.debug > debug.DISABLED then
dprint = function(...)
print(table.concat({"Lua:", ...}," "))
end
if default_settings.debug > debug.LEVEL_1 then
dprint2 = dprint
end
end
end
-- call it now
reset_debug()
--------------------------------------------------------------------------------
-- file reader handling functions for Wireshark to use
--------------------------------------------------------------------------------
----------------------------------------
-- The read_open() is called by Wireshark once per file, to see if the file is this reader's type.
-- Wireshark passes in (1) a File object and (2) CaptureInfo object to this function
-- It expects in return either nil or false to mean it's not our file type, or true if it is
-- In our case what this means is we figure out if the file has the magic header, and get the
-- endianess of the file, and the encapsulation type of its frames/records
local function read_open(file, capture)
dprint2("read_open() called")
local file_settings = parse_file_header(file)
if file_settings then
dprint2("read_open: success, file is for us")
-- save our state
capture.private_table = file_settings
-- if the file is for us, we MUST set the file position cursor to
-- where we want the first call to read() function to get it the next time
-- for example if we checked a few records to be sure it's or type
-- but in this simple example we only verify the file header (24 bytes)
-- and we want the file position to remain after that header for our read()
-- call, so we don't change it back
--file:seek("set",position)
-- these we can also set per record later during read operations
capture.time_precision = file_settings.time_precision
capture.encap = file_settings.wtap_type
capture.snapshot_length = file_settings.snaplen
return true
end
dprint2("read_open: file not for us")
-- if it's not for us, wireshark will reset the file position itself
return false
end
----------------------------------------
-- Wireshark/tshark calls read() for each frame/record in the file
-- It passes in (1) a File, (2) CaptureInfo, and (3) FrameInfo object to this function
-- It expects in return the file offset position the record starts at,
-- or nil/false if there's an error or end-of-file is reached.
-- The offset position is used later: wireshark remembers it and gives
-- it to seek_read() at various random times
local function read(file, capture, frame)
dprint2("read() called")
-- call our common reader function
local position = file:seek()
if not read_common("read", file, capture, frame) then
-- this isnt' actually an error, because it might just mean we reached end-of-file
-- so let's test for that (read(0) is a special case in Lua, see Lua docs)
if file:read(0) ~= nil then
dprint("read: failed to call read_common")
else
dprint2("read: reached end of file")
end
return false
end
dprint2("read: succeess")
-- return the position we got to (or nil if we hit EOF/error)
return position
end
----------------------------------------
-- Wireshark/tshark calls seek_read() for each frame/record in the file, at random times
-- It passes in (1) a File, (2) CaptureInfo, (3) FrameInfo object, and the offset position number
-- It expects in return true for successful parsing, or nil/false if there's an error.
local function seek_read(file, capture, frame, offset)
dprint2("seek_read() called")
-- first move to the right position in the file
file:seek("set",offset)
if not read_common("seek_read", file, capture, frame) then
dprint("seek_read: failed to call read_common")
return false
end
return true
end
----------------------------------------
-- Wireshark/tshark calls read_close() when it's closing the file completely
-- It passes in (1) a File and (2) CaptureInfo object to this function
-- this is a good opportunity to clean up any state you may have created during
-- file reading. (in our case there's no real state)
local function read_close(file, capture)
dprint2("read_close() called")
-- we don't really have to reset anything, because we used the
-- capture.private_table and wireshark clears it for us after this function
return true
end
----------------------------------------
-- An often unused function, Wireshark calls this when the sequential walk-through is over
-- (i.e., no more calls to read(), only to seek_read()).
-- It passes in (1) a File and (2) CaptureInfo object to this function
-- This gives you a chance to clean up any state you used during read() calls, but remember
-- that there will be calls to seek_read() after this (in Wireshark, though not Tshark)
local function seq_read_close(file, capture)
dprint2("First pass of read() calls are over, but there may be seek_read() calls after this")
return true
end
----------------------------------------
-- ok, so let's create a FileHandler object
local fh = FileHandler.new("Lua-based PCAP reader", "lua_pcap", "A Lua-based file reader for PCAP-type files","rms")
-- set above functions to the FileHandler
fh.read_open = read_open
fh.read = read
fh.seek_read = seek_read
fh.read_close = read_close
fh.seq_read_close = seq_read_close
fh.extensions = "pcap;cap" -- this is just a hint
-- and finally, register the FileHandler!
register_filehandler(fh)
dprint2("FileHandler registered")
--------------------------------------------------------------------------------
-- ok now for the boring stuff that actually does the work
--------------------------------------------------------------------------------
----------------------------------------
-- in Lua, we have access to encapsulation types in the 'wtap_encaps' table, but
-- those numbers don't actually necessarily match the numbers in pcap files
-- for the encapsulation type, because the namespace got screwed up at some
-- point in the past (blame LBL NRG, not wireshark for that)
-- but I'm not going to create the full mapping of these two namespaces
-- instead we'll just use this smaller table to map them
-- these are taken from wiretap/pcap-common.c
local pcap2wtap = {
[0] = wtap_encaps.NULL,
[1] = wtap_encaps.ETHERNET,
[6] = wtap_encaps.TOKEN_RING,
[8] = wtap_encaps.SLIP,
[9] = wtap_encaps.PPP,
[101] = wtap_encaps.RAW_IP,
[105] = wtap_encaps.IEEE_802_11,
[127] = wtap_encaps.IEEE_802_11_RADIOTAP,
[140] = wtap_encaps.MTP2,
[141] = wtap_encaps.MTP3,
[143] = wtap_encaps.DOCSIS,
[147] = wtap_encaps.USER0,
[148] = wtap_encaps.USER1,
[149] = wtap_encaps.USER2,
[150] = wtap_encaps.USER3,
[151] = wtap_encaps.USER4,
[152] = wtap_encaps.USER5,
[153] = wtap_encaps.USER6,
[154] = wtap_encaps.USER7,
[155] = wtap_encaps.USER8,
[156] = wtap_encaps.USER9,
[157] = wtap_encaps.USER10,
[158] = wtap_encaps.USER11,
[159] = wtap_encaps.USER12,
[160] = wtap_encaps.USER13,
[161] = wtap_encaps.USER14,
[162] = wtap_encaps.USER15,
[186] = wtap_encaps.USB,
[187] = wtap_encaps.BLUETOOTH_H4,
[189] = wtap_encaps.USB_LINUX,
[195] = wtap_encaps.IEEE802_15_4,
}
-- we can use the above to directly map very quickly
-- but to map it backwards we'll use this, because I'm lazy:
local function wtap2pcap(encap)
for k,v in pairs(pcap2wtap) do
if v == encap then
return k
end
end
return 0
end
----------------------------------------
-- here are the "structs" we're going to parse, of the various records in a pcap file
-- these pattern string gets used in calls to Struct.unpack()
--
-- we will prepend a '<' or '>' later, once we figure out what endian-ess the files are in
--
-- this is a constant for minimum we need to read before we figure out the filetype
local FILE_HDR_LEN = 24
-- a pcap file header struct
-- this is: magic, version_major, version_minor, timezone, sigfigs, snaplen, encap type
local FILE_HEADER_PATT = "I4 I2 I2 i4 I4 I4 I4"
-- it's too bad Struct doesn't have a way to get the number of vars the pattern holds
-- another thing to add to my to-do list?
local NUM_HDR_FIELDS = 7
-- these will hold the '<'/'>' prepended version of above
--local file_header, rec_header
-- snaplen/caplen can't be bigger than this
local WTAP_MAX_PACKET_SIZE = 65535
----------------------------------------
-- different pcap file types have different magic values
-- we need to know various things about them for various functions
-- in this script, so this table holds all the info
--
-- See default_settings table above for the defaults used if this table
-- doesn't override them.
--
-- Arguably, these magic types represent different "Protocols" to dissect later,
-- but this script treats them all as "pcapfile" protocol.
--
-- From this table, we'll auto-create a value-string table for file header magic field
local magic_spells =
{
normal =
{
magic = 0xa1b2c3d4,
name = "Normal (Big-endian)",
},
swapped =
{
magic = 0xd4c3b2a1,
name = "Swapped Normal (Little-endian)",
endianess = ENC_LITTLE_ENDIAN,
},
modified =
{
-- this is for a ss991029 patched format only
magic = 0xa1b2cd34,
name = "Modified",
rec_hdr_len = 24,
rec_hdr_patt = "I4I4I4I4 I4 I2 I1 I1",
num_rec_fields = 8,
},
swapped_modified =
{
-- this is for a ss991029 patched format only
magic = 0x34cdb2a1,
name = "Swapped Modified",
rec_hdr_len = 24,
rec_hdr_patt = "I4I4I4I4 I4 I2 I1 I1",
num_rec_fields = 8,
endianess = ENC_LITTLE_ENDIAN,
},
nsecs =
{
magic = 0xa1b23c4d,
name = "Nanosecond",
time_precision = wtap_filetypes.TSPREC_NSEC,
},
swapped_nsecs =
{
magic = 0x4d3cb2a1,
name = "Swapped Nanosecond",
endianess = ENC_LITTLE_ENDIAN,
time_precision = wtap_filetypes.TSPREC_NSEC,
},
}
-- create a magic-to-spell entry table from above magic_spells table
-- so we can find them faster during file read operations
-- we could just add them right back into spells table, but this is cleaner
local magic_values = {}
for k,t in pairs(magic_spells) do
magic_values[t.magic] = t
end
-- the function which makes a copy of the default settings per file
local function new_settings()
dprint2("creating new file_settings")
local file_settings = {}
for k,v in pairs(default_settings) do
file_settings[k] = v
end
return file_settings
end
-- set the file_settings that the magic value defines in magic_values
local function set_magic_file_settings(magic)
local t = magic_values[magic]
if not t then
dprint("set_magic_file_settings: did not find magic settings for:",magic)
return false
end
local file_settings = new_settings()
-- the magic_values/spells table uses the same key names, so this is easy
for k,v in pairs(t) do
file_settings[k] = v
end
-- based on endianess, set the file_header and rec_header
-- and determine corrected_magic
if file_settings.endianess == ENC_BIG_ENDIAN then
file_settings.file_hdr_patt = '>' .. FILE_HEADER_PATT
file_settings.rec_hdr_patt = '>' .. file_settings.rec_hdr_patt
file_settings.corrected_magic = magic
else
file_settings.file_hdr_patt = '<' .. FILE_HEADER_PATT
file_settings.rec_hdr_patt = '<' .. file_settings.rec_hdr_patt
local m = Struct.pack(">I4", magic)
file_settings.corrected_magic = Struct.unpack("<I4", m)
end
file_settings.rec_hdr_len = Struct.size(file_settings.rec_hdr_patt)
return file_settings
end
----------------------------------------
-- internal functions declared previously
----------------------------------------
----------------------------------------
-- used by read_open(), this parses the file header
parse_file_header = function(file)
dprint2("parse_file_header() called")
-- by default, file:read() gets the next "string", meaning ending with a newline \n
-- but we want raw byte reads, so tell it how many bytes to read
local line = file:read(FILE_HDR_LEN)
-- it's ok for us to not be able to read it, but we need to tell wireshark the
-- file's not for us, so return false
if not line then return false end
dprint2("parse_file_header: got this line:\n'", Struct.tohex(line,false,":"), "'")
-- let's peek at the magic int32, assuming it's big-endian
local magic = Struct.unpack(">I4", line)
local file_settings = set_magic_file_settings(magic)
if not file_settings then
dprint("magic was: '", magic, "', so not a known pcap file?")
return false
end
-- this is: magic, version_major, version_minor, timezone, sigfigs, snaplen, encap type
local fields = { Struct.unpack(file_settings.file_hdr_patt, line) }
-- sanity check; also note that Struct.unpack() returns the fields plus
-- a number of where in the line it stopped reading (i.e., the end in this case)
-- so we got back number of fields + 1
if #fields ~= NUM_HDR_FIELDS + 1 then
-- this should never happen, since we already told file:read() to grab enough bytes
dprint("parse_file_header: failed to read the file header")
return nil
end
-- fields[1] is the magic, which we already parsed and saved before, but just to be sure
-- our endianess is set right, we validate what we got is what we expect now that
-- endianess has been corrected
if fields[1] ~= file_settings.corrected_magic then
dprint ("parse_file_header: endianess screwed up? Got:'", fields[1],
"', but wanted:", file_settings.corrected_magic)
return nil
end
file_settings.version_major = fields[2]
file_settings.version_minor = fields[3]
file_settings.timezone = fields[4]
file_settings.sigfigs = fields[5]
file_settings.read_snaplen = fields[6]
file_settings.linktype = fields[7]
-- wireshark only supports version 2.0 and later
if fields[2] < 2 then
dprint("got version =",VERSION_MAJOR,"but only version 2 or greater supported")
return false
end
-- convert pcap file interface type to wtap number type
file_settings.wtap_type = pcap2wtap[file_settings.linktype]
if not file_settings.wtap_type then
dprint("file nettype", file_settings.linktype,
"couldn't be mapped to wireshark wtap type")
return false
end
file_settings.snaplen = file_settings.read_snaplen
if file_settings.snaplen > WTAP_MAX_PACKET_SIZE then
file_settings.snaplen = WTAP_MAX_PACKET_SIZE
end
dprint2("read_file_header: got magic='", magic,
"', major version='", file_settings.version_major,
"', minor='", file_settings.version_minor,
"', timezone='", file_settings.timezone,
"', sigfigs='", file_settings.sigfigs,
"', read_snaplen='", file_settings.read_snaplen,
"', snaplen='", file_settings.snaplen,
"', nettype ='", file_settings.linktype,
"', wtap ='", file_settings.wtap_type)
--ok, it's a pcap file
dprint2("parse_file_header: success")
return file_settings
end
----------------------------------------
-- this is used by both read() and seek_read()
-- the calling function to this should have already set the file position correctly
read_common = function(funcname, file, capture, frame)
dprint2(funcname,": read_common() called")
-- get the state info
local file_settings = capture.private_table
-- first parse the record header, which will set the FrameInfo fields
if not parse_rec_header(funcname, file, file_settings, frame) then
dprint2(funcname, ": read_common: hit end of file or error")
return false
end
frame.encap = file_settings.wtap_type
-- now we need to get the packet bytes from the file record into the frame...
-- we *could* read them into a string using file:read(numbytes), and then
-- set them to frame.data so that wireshark gets it...
-- but that would mean the packet's string would be copied into Lua
-- and then sent right back into wireshark, which is gonna slow things
-- down; instead FrameInfo has a read_data() method, which makes
-- wireshark read directly from the file into the frame buffer, so we use that
if not frame:read_data(file, frame.captured_length) then
dprint(funcname, ": read_common: failed to read data from file into buffer")
return false
end
return true
end
----------------------------------------
-- the function to parse individual records
parse_rec_header = function(funcname, file, file_settings, frame)
dprint2(funcname,": parse_rec_header() called")
local line = file:read(file_settings.rec_hdr_len)
-- it's ok for us to not be able to read it, if it's end of file
if not line then return false end
-- this is: time_sec, time_usec, capture_len, original_len
local fields = { Struct.unpack(file_settings.rec_hdr_patt, line) }
-- sanity check; also note that Struct.unpack() returns the fields plus
-- a number of where in the line it stopped reading (i.e., the end in this case)
-- so we got back number of fields + 1
if #fields ~= file_settings.num_rec_fields + 1 then
dprint(funcname, ": parse_rec_header: failed to read the record header, got:",
#fields, ", expected:", file_settings.num_rec_fields)
return nil
end
local nsecs = fields[2]
if file_settings.time_precision == wtap_filetypes.TSPREC_USEC then
nsecs = nsecs * 1000
elseif file_settings.time_precision == wtap_filetypes.TSPREC_MSEC then
nsecs = nsecs * 1000000
end
frame.time = NSTime(fields[1], nsecs)
local caplen, origlen = fields[3], fields[4]
-- sanity check, verify captured length isn't more than original length
if caplen > origlen then
dprint("captured length of", caplen, "is bigger than original length of", origlen)
-- swap them, a cool Lua ability
caplen, origlen = origlen, caplen
end
if caplen > WTAP_MAX_PACKET_SIZE then
dprint("Got a captured_length of", caplen, "which is too big")
caplen = WTAP_MAX_PACKET_SIZE
end
frame.rec_type = wtap_rec_types.PACKET
frame.captured_length = caplen
frame.original_length = origlen
frame.flags = wtap_presence_flags.TS + wtap_presence_flags.CAP_LEN -- for timestamp|cap_len
dprint2(funcname,": parse_rec_header() returning")
return true
end
--------------------------------------------------------------------------------
-- file writer handling functions for Wireshark to use
--------------------------------------------------------------------------------
-- file encaps we can handle writing
local canwrite = {
[ wtap_encaps.NULL ] = true,
[ wtap_encaps.ETHERNET ] = true,
[ wtap_encaps.PPP ] = true,
[ wtap_encaps.RAW_IP ] = true,
[ wtap_encaps.IEEE_802_11 ] = true,
[ wtap_encaps.MTP2 ] = true,
[ wtap_encaps.MTP3 ] = true,
-- etc., etc.
}
-- we can't reuse the variables we used in the reader, because this script might be used to both
-- open a file for reading and write it out, at the same time, so we cerate another file_settings
-- instance.
-- set the file_settings for the little-endian version in magic_spells
local function create_writer_file_settings()
dprint2("create_writer_file_settings called")
local t = magic_spells.swapped
local file_settings = new_settings()
-- the magic_values/spells table uses the same key names, so this is easy
for k,v in pairs(t) do
file_settings[k] = v
end
-- based on endianess, set the file_header and rec_header
-- and determine corrected_magic
if file_settings.endianess == ENC_BIG_ENDIAN then
file_settings.file_hdr_patt = '>' .. FILE_HEADER_PATT
file_settings.rec_hdr_patt = '>' .. file_settings.rec_hdr_patt
file_settings.corrected_magic = file_settings.magic
else
file_settings.file_hdr_patt = '<' .. FILE_HEADER_PATT
file_settings.rec_hdr_patt = '<' .. file_settings.rec_hdr_patt
local m = Struct.pack(">I4", file_settings.magic)
file_settings.corrected_magic = Struct.unpack("<I4", m)
end
file_settings.rec_hdr_len = Struct.size(file_settings.rec_hdr_patt)
return file_settings
end
----------------------------------------
-- The can_write_encap() function is called by Wireshark when it wants to write out a file,
-- and needs to see if this file writer can handle the packet types in the window.
-- We need to return true if we can handle it, else false
local function can_write_encap(encap)
dprint2("can_write_encap() called with encap=",encap)
return canwrite[encap] or false
end
local function write_open(file, capture)
dprint2("write_open() called")
local file_settings = create_writer_file_settings()
-- write out file header
local hdr = Struct.pack(file_settings.file_hdr_patt,
file_settings.corrected_magic,
file_settings.version_major,
file_settings.version_minor,
file_settings.timezone,
file_settings.sigfigs,
capture.snapshot_length,
wtap2pcap(capture.encap))
if not hdr then
dprint("write_open: error generating file header")
return false
end
dprint2("write_open generating:", Struct.tohex(hdr))
if not file:write(hdr) then
dprint("write_open: error writing file header to file")
return false
end
-- save settings
capture.private_table = file_settings
return true
end
local function write(file, capture, frame)
dprint2("write() called")
-- get file settings
local file_settings = capture.private_table
if not file_settings then
dprint("write() failed to get private table file settings")
return false
end
-- write out record header: time_sec, time_usec, capture_len, original_len
-- first get times
local nstime = frame.time
-- pcap format is in usecs, but wireshark's internal is nsecs
local nsecs = nstime.nsecs
if file_settings.time_precision == wtap_filetypes.TSPREC_USEC then
nsecs = nsecs / 1000
elseif file_settings.time_precision == wtap_filetypes.TSPREC_MSEC then
nsecs = nsecs / 1000000
end
local hdr = Struct.pack(file_settings.rec_hdr_patt,
nstime.secs,
nsecs,
frame.captured_length,
frame.original_length)
if not hdr then
dprint("write: error generating record header")
return false
end
if not file:write(hdr) then
dprint("write: error writing record header to file")
return false
end
-- we could write the packet data the same way, by getting frame.data and writing it out
-- but we can avoid copying those bytes into Lua by using the write_data() function
if not frame:write_data(file) then
dprint("write: error writing record data to file")
return false
end
return true
end
local function write_close(file, capture)
dprint2("write_close() called")
dprint2("Good night, and good luck")
return true
end
-- ok, so let's create another FileHandler object
local fh2 = FileHandler.new("Lua-based PCAP writer", "lua_pcap2", "A Lua-based file writer for PCAP-type files","wms")
-- set above functions to the FileHandler
fh2.can_write_encap = can_write_encap
fh2.write_open = write_open
fh2.write = write
fh2.write_close = write_close
fh2.extensions = "pcap;cap" -- this is just a hint
-- and finally, register the FileHandler!
register_filehandler(fh2)
dprint2("Second FileHandler registered")
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