| Current Path : /usr/share/nmap/nselib/ |
| Current File : //usr/share/nmap/nselib/netbios.lua |
---
-- Creates and parses NetBIOS traffic. The primary use for this is to send
-- NetBIOS name requests.
--
-- @author Ron Bowes <ron@skullsecurity.net>
-- @copyright Same as Nmap--See http://nmap.org/book/man-legal.html
module(... or "netbios", package.seeall)
require 'bit'
require 'bin'
require 'stdnse'
--- Encode a NetBIOS name for transport. Most packets that use the NetBIOS name
-- require this encoding to happen first. It takes a name containing any possible
-- character, and converted it to all uppercase characters (so it can, for example,
-- pass case-sensitive data in a case-insensitive way)
--
-- There are two levels of encoding performed:
-- * L1: Pad the string to 16 characters withs spaces (or NULLs if it's the
-- wildcard "*") and replace each byte with two bytes representing each
-- of its nibbles, plus 0x41.
-- * L2: Prepend the length to the string, and to each substring in the scope
-- (separated by periods).
--@param name The name that will be encoded (eg. "TEST1").
--@param scope [optional] The scope to encode it with. I've never seen scopes used
-- in the real world (eg, "insecure.org").
--@return The L2-encoded name and scope
-- (eg. "\x20FEEFFDFEDBCACACACACACACACACAAA\x08insecure\x03org")
function name_encode(name, scope)
stdnse.print_debug(3, "Encoding name '%s'", name)
-- Truncate or pad the string to 16 bytes
if(string.len(name) >= 16) then
name = string.sub(name, 1, 16)
else
local padding = " "
if name == "*" then
padding = "\0"
end
repeat
name = name .. padding
until string.len(name) == 16
end
-- Convert to uppercase
name = string.upper(name)
-- Do the L1 encoding
local L1_encoded = ""
for i=1, string.len(name), 1 do
local b = string.byte(name, i)
L1_encoded = L1_encoded .. string.char(bit.rshift(bit.band(b, 0xF0), 4) + 0x41)
L1_encoded = L1_encoded .. string.char(bit.rshift(bit.band(b, 0x0F), 0) + 0x41)
end
-- Do the L2 encoding
local L2_encoded = string.char(32) .. L1_encoded
if scope ~= nil then
-- Split the scope at its periods
local piece
for piece in string.gmatch(scope, "[^.]+") do
L2_encoded = L2_encoded .. string.char(string.len(piece)) .. piece
end
end
stdnse.print_debug(3, "=> '%s'", L2_encoded)
return L2_encoded
end
--- Does the exact opposite of name_encode. Converts an encoded name to
-- the string representation. If the encoding is invalid, it will still attempt
-- to decode the string as best as possible.
--@param encoded_name The L2-encoded name
--@return the decoded name and the scope. The name will still be padded, and the
-- scope will never be nil (empty string is returned if no scope is present)
function name_decode(encoded_name)
local name = ""
local scope = ""
local len = string.byte(encoded_name, 1)
local i
stdnse.print_debug(3, "Decoding name '%s'", encoded_name)
for i = 2, len + 1, 2 do
local ch = 0
ch = bit.bor(ch, bit.lshift(string.byte(encoded_name, i) - 0x41, 4))
ch = bit.bor(ch, bit.lshift(string.byte(encoded_name, i + 1) - 0x41, 0))
name = name .. string.char(ch)
end
-- Decode the scope
local pos = 34
while string.len(encoded_name) > pos do
local len = string.byte(encoded_name, pos)
scope = scope .. string.sub(encoded_name, pos + 1, pos + len) .. "."
pos = pos + 1 + len
end
-- If there was a scope, remove the trailing period
if(string.len(scope) > 0) then
scope = string.sub(scope, 1, string.len(scope) - 1)
end
stdnse.print_debug(3, "=> '%s'", name)
return name, scope
end
--- Sends out a UDP probe on port 137 to get a human-readable list of names the
-- the system is using.
--@param host The IP or hostname to check.
--@param prefix [optional] The prefix to put on each line when it's returned.
--@return (status, result) If status is true, the result is a human-readable
-- list of names. Otherwise, result is an error message.
function get_names(host, prefix)
local status, names, statistics = do_nbstat(host)
if(prefix == nil) then
prefix = ""
end
if(status) then
local result = ""
for i = 1, #names, 1 do
result = result .. string.format("%s%s<%02x>\n", prefix, names[i]['name'], names[i]['prefix'])
end
return true, result
else
return false, names
end
end
--- Sends out a UDP probe on port 137 to get the server's name (that is, the
-- entry in its NBSTAT table with a 0x20 suffix).
--@param host The IP or hostname of the server.
--@param names [optional] The names to use, from <code>do_nbstat</code>.
--@return (status, result) If status is true, the result is the NetBIOS name.
-- otherwise, result is an error message.
function get_server_name(host, names)
local status
local i
if names == nil then
status, names = do_nbstat(host)
if(status == false) then
return false, names
end
end
for i = 1, #names, 1 do
if names[i]['suffix'] == 0x20 then
return true, names[i]['name']
end
end
return false, "Couldn't find NetBIOS server name"
end
--- Sends out a UDP probe on port 137 to get the user's name (that is, the
-- entry in its NBSTAT table with a 0x03 suffix, that isn't the same as
-- the server's name. If the username can't be determined, which is frequently
-- the case, nil is returned.
--@param host The IP or hostname of the server.
--@param names [optional] The names to use, from <code>do_nbstat</code>.
--@return (status, result) If status is true, the result is the NetBIOS name or nil.
-- otherwise, result is an error message.
function get_user_name(host, names)
local status, server_name = get_server_name(host, names)
if(status == false) then
return false, server_name
end
if(names == nil) then
status, names = do_nbstat(host)
if(status == false) then
return false, names
end
end
for i = 1, #names, 1 do
if names[i]['suffix'] == 0x03 and names[i]['name'] ~= server_name then
return true, names[i]['name']
end
end
return true, nil
end
--- This is the function that actually handles the UDP query to retrieve
-- the NBSTAT information. We make use of the Nmap registry here, so if another
-- script has already performed a nbstat query, the result can be re-used.
--
-- The NetBIOS request's header looks like this:
--<code>
-- --------------------------------------------------
-- | 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0 |
-- | NAME_TRN_ID |
-- | R | OPCODE | NM_FLAGS | RCODE | (FLAGS)
-- | QDCOUNT |
-- | ANCOUNT |
-- | NSCOUNT |
-- | ARCOUNT |
-- --------------------------------------------------
--</code>
--
-- In this case, the TRN_ID is a constant (0x1337, what else?), the flags
-- are 0, and we have one question. All fields are network byte order.
--
-- The body of the packet is a list of names to check for in the following
-- format:
-- * (ntstring) encoded name
-- * (2 bytes) query type (0x0021 = NBSTAT)
-- * (2 bytes) query class (0x0001 = IN)
--
-- The response header is the exact same, except it'll have some flags set
-- (0x8000 for sure, since it's a response), and ANCOUNT will be 1. The format
-- of the answer is:
--
-- * (ntstring) requested name
-- * (2 bytes) query type
-- * (2 bytes) query class
-- * (2 bytes) time to live
-- * (2 bytes) record length
-- * (1 byte) number of names
-- * [for each name]
-- * (16 bytes) padded name, with a 1-byte suffix
-- * (2 bytes) flags
-- * (variable) statistics (usually mac address)
--
--@param host The IP or hostname of the system.
--@return (status, names, statistics) If status is true, then the servers names are
-- returned as a table containing 'name', 'suffix', and 'flags'.
-- Otherwise, names is an error message and statistics is undefined.
function do_nbstat(host)
local status, err
local socket = nmap.new_socket()
local encoded_name = name_encode("*")
local statistics
stdnse.print_debug(3, "Performing nbstat on host '%s'", host)
-- Check if it's cased in the registry for this host
if(nmap.registry["nbstat_names_" .. host] ~= nil) then
stdnse.print_debug(3, " |_ [using cached value]")
return true, nmap.registry["nbstat_names_" .. host], nmap.registry["nbstat_statistics_" .. host]
end
-- Create the query header
local query = bin.pack(">SSSSSS",
0x1337, -- Transaction id
0x0000, -- Flags
1, -- Questions
0, -- Answers
0, -- Authority
0 -- Extra
)
query = query .. bin.pack(">zSS",
encoded_name, -- Encoded name
0x0021, -- Query type (0x21 = NBSTAT)
0x0001 -- Class = IN
)
status, err = socket:connect(host, 137, "udp")
if(status == false) then
return false, err
end
status, err = socket:send(query)
if(status == false) then
return false, err
end
socket:set_timeout(1000)
local status, result = socket:receive_bytes(1)
if(status == false) then
return false, result
end
local close_status, err = socket:close()
if(close_status == false) then
return false, err
end
if(status) then
local pos, TRN_ID, FLAGS, QDCOUNT, ANCOUNT, NSCOUNT, ARCOUNT, rr_name, rr_type, rr_class, rr_ttl
local rrlength, name_count
pos, TRN_ID, FLAGS, QDCOUNT, ANCOUNT, NSCOUNT, ARCOUNT = bin.unpack(">SSSSSS", result)
-- Sanity check the result (has to have the same TRN_ID, 1 answer, and proper flags)
if(TRN_ID ~= 0x1337) then
return false, string.format("Invalid transaction ID returned: 0x%04x", TRN_ID)
end
if(ANCOUNT ~= 1) then
return false, "Server returned an invalid number of answers"
end
if(bit.band(FLAGS, 0x8000) == 0) then
return false, "Server's flags didn't indicate a response"
end
if(bit.band(FLAGS, 0x0007) ~= 0) then
return false, string.format("Server returned a NetBIOS error: 0x%02x", bit.band(FLAGS, 0x0007))
end
-- Start parsing the answer field
pos, rr_name, rr_type, rr_class, rr_ttl = bin.unpack(">zSSI", result, pos)
-- More sanity checks
if(rr_name ~= encoded_name) then
return false, "Server returned incorrect name"
end
if(rr_class ~= 0x0001) then
return false, "Server returned incorrect class"
end
if(rr_type ~= 0x0021) then
return false, "Server returned incorrect query type"
end
pos, rrlength, name_count = bin.unpack(">SC", result, pos)
local names = {}
for i = 1, name_count do
local name, suffix, flags
-- Instead of reading the 16-byte name and pulling off the suffix,
-- we read the first 15 bytes and then the 1-byte suffix.
pos, name, suffix, flags = bin.unpack(">A15CS", result, pos)
name = string.gsub(name, "[ ]*$", "")
names[i] = {}
names[i]['name'] = name
names[i]['suffix'] = suffix
names[i]['flags'] = flags
-- Decrement the length
rrlength = rrlength - 18
end
if(rrlength > 0) then
rrlength = rrlength - 1
end
pos, statistics = bin.unpack(string.format(">A%d", rrlength), result, pos)
-- Put it in the registry, in case anybody else needs it
nmap.registry["nbstat_names_" .. host] = names
nmap.registry["nbstat_statistics_" .. host] = statistics
return true, names, statistics
else
return false, "Name query failed: " .. result
end
end
---Convert the 16-bit flags field to a string.
--@param flags The 16-bit flags field
--@return A string representing the flags
function flags_to_string(flags)
local result = ""
if(bit.band(flags, 0x8000) ~= 0) then
result = result .. "<group>"
else
result = result .. "<unique>"
end
if(bit.band(flags, 0x1000) ~= 0) then
result = result .. "<deregister>"
end
if(bit.band(flags, 0x0800) ~= 0) then
result = result .. "<conflict>"
end
if(bit.band(flags, 0x0400) ~= 0) then
result = result .. "<active>"
end
if(bit.band(flags, 0x0200) ~= 0) then
result = result .. "<permanent>"
end
return result
end
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