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--[[
Copyright (c) 2019, Vsevolod Stakhov <vsevolod@highsecure.ru>
Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at
http://www.apache.org/licenses/LICENSE-2.0
Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.
]]--
-- Bitcoin filter rules
local fun = require "fun"
local bit = require "bit"
local lua_util = require "lua_util"
local rspamd_util = require "rspamd_util"
local N = "bitcoin"
local off = 0
local base58_dec = fun.tomap(fun.map(
function(c)
off = off + 1
return c,(off - 1)
end,
"123456789ABCDEFGHJKLMNPQRSTUVWXYZabcdefghijkmnopqrstuvwxyz"))
local function is_traditional_btc_address(word)
local hash = require "rspamd_cryptobox_hash"
local bytes = {}
for i=1,25 do bytes[i] = 0 end
-- Base58 decode loop
fun.each(function(ch)
local acc = base58_dec[ch] or 0
for i=25,1,-1 do
acc = acc + (58 * bytes[i]);
bytes[i] = acc % 256
acc = math.floor(acc / 256);
end
end, word)
-- Now create a validation tag
local sha256 = hash.create_specific('sha256')
for i=1,21 do
sha256:update(string.char(bytes[i]))
end
sha256 = hash.create_specific('sha256', sha256:bin()):bin()
-- Compare tags
local valid = true
for i=1,4 do
if string.sub(sha256, i, i) ~= string.char(bytes[21 + i]) then
valid = false
end
end
return valid
end
-- Beach32 checksum combiner
local function polymod(...)
local chk = 1;
local gen = {0x3b6a57b2, 0x26508e6d, 0x1ea119fa, 0x3d4233dd, 0x2a1462b3};
for _,t in ipairs({...}) do
for _,v in ipairs(t) do
local top = bit.rshift(chk, 25)
chk = bit.bxor(bit.lshift(bit.band(chk, 0x1ffffff), 5), v)
for i=1,5 do
if bit.band(bit.rshift(top, i - 1), 0x1) ~= 0 then
chk = bit.bxor(chk, gen[i])
end
end
end
end
return chk
end
-- Beach32 expansion function
local function hrpExpand(hrp)
local ret = {}
fun.each(function(byte)
ret[#ret + 1] = bit.rshift(byte, 5)
end, fun.map(string.byte, fun.iter(hrp)))
ret[#ret + 1] = 0
fun.each(function(byte)
ret[#ret + 1] = bit.band(byte, 0x1f)
end, fun.map(string.byte, fun.iter(hrp)))
return ret
end
local function verify_beach32_cksum(hrp, elts)
return polymod(hrpExpand(hrp), elts) == 1
end
local function gen_bleach32_table(input)
local d = {}
local i = 1
local res = true
local charset = 'qpzry9x8gf2tvdw0s3jn54khce6mua7l'
fun.each(function(byte)
if res then
local pos = charset:find(byte, 1, true)
if not pos then
res = false
else
d[i] = pos - 1
i = i + 1
end
end
end, fun.iter(input))
return res and d or nil
end
local function is_segwit_bech32_address(task, word)
local semicolon_pos = string.find(word, ':')
local address_part = word
if semicolon_pos then
address_part = string.sub(word, semicolon_pos + 1)
end
local prefix = address_part:sub(1, 3)
if prefix == 'bc1' or prefix:sub(1, 1) == '1' or prefix:sub(1, 1) == '3' then
-- Strip beach32 prefix in bitcoin
address_part = address_part:lower()
local last_one_pos = address_part:find('1[^1]*$')
if not last_one_pos or (last_one_pos < 1 or last_one_pos + 7 > #address_part) then
return false
end
local hrp = address_part:sub(1, last_one_pos - 1)
local addr = address_part:sub(last_one_pos + 1, -1)
local decoded = gen_bleach32_table(addr)
if decoded then
return verify_beach32_cksum(hrp, decoded)
end
else
-- Bitcoin cash address
-- https://www.bitcoincash.org/spec/cashaddr.html
local decoded = gen_bleach32_table(address_part)
lua_util.debugm(N, task, 'check %s, %s decoded', word, decoded)
if decoded and #decoded > 8 then
if semicolon_pos then
prefix = word:sub(1, semicolon_pos - 1)
else
prefix = 'bitcoincash'
end
local polymod_tbl = {}
fun.each(function(byte)
local b = bit.band(string.byte(byte), 0x1f)
table.insert(polymod_tbl, b)
end, fun.iter(prefix))
-- For semicolon
table.insert(polymod_tbl, 0)
fun.each(function(byte) table.insert(polymod_tbl, byte) end, decoded)
lua_util.debugm(N, task, 'final polymod table: %s', polymod_tbl)
return rspamd_util.btc_polymod(polymod_tbl)
end
end
end
local normal_wallet_re = [[/\b[13LM][1-9A-Za-z]{25,34}\b/AL{sa_body}]]
local btc_bleach_re = [[/\b(?:[a-zA-Z]\w+:)?[qpzry9x8gf2tvdw0s3jn54khce6mua7l]{14,}\b/AL{sa_body}]]
config.regexp['BITCOIN_ADDR'] = {
description = 'Message has a valid bitcoin wallet address',
re = string.format('(%s) || (%s)', normal_wallet_re, btc_bleach_re),
re_conditions = {
[normal_wallet_re] = function(task, txt, s, e)
if e - s <= 2 then
return false
end
local word = lua_util.str_trim(txt:sub(s + 1, e))
local valid = is_traditional_btc_address(word)
if valid then
-- To save option
task:insert_result('BITCOIN_ADDR', 1.0, word)
lua_util.debugm(N, task, 'found valid traditional bitcoin addr in the word: %s',
word)
return true
else
lua_util.debugm(N, task, 'found invalid bitcoin addr in the word: %s',
word)
return false
end
end,
[btc_bleach_re] = function(task, txt, s, e)
if e - s <= 2 then
return false
end
local word = tostring(lua_util.str_trim(txt:sub(s + 1, e)))
local valid = is_segwit_bech32_address(task, word)
if valid then
-- To save option
task:insert_result('BITCOIN_ADDR', 1.0, word)
lua_util.debugm(N, task, 'found valid bleach bitcoin addr in the word: %s',
word)
return true
else
lua_util.debugm(N, task, 'found invalid bitcoin addr in the word: %s',
word)
return false
end
end,
},
score = 0.0,
one_shot = true,
group = 'scams',
}
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