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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 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)
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(word)
local semicolon_pos = string.find(word, ':')
if semicolon_pos then
word = string.sub(word, semicolon_pos + 1)
end
local prefix = word:sub(1, 3)
if prefix == 'bc1' or prefix:sub(1, 1) == '1' or prefix:sub(1, 1) == '3' then
-- Strip beach32 prefix in bitcoin
word = word:lower()
local last_one_pos = word:find('1[^1]*$')
if not last_one_pos or (last_one_pos < 1 or last_one_pos + 7 > #word) then
return false
end
local hrp = word:sub(1, last_one_pos - 1)
local addr = word:sub(last_one_pos + 1, -1)
local decoded = gen_bleach32_table(addr)
if decoded then
return verify_beach32_cksum(hrp, decoded)
end
else
-- BCH address
-- 1 byte address type (who cares)
-- XXX bytes address hash (who cares)
-- 40 bit checksum
local rspamd_util = require 'rspamd_util'
local decoded = rspamd_util.decode_base32(word:lower(), 'bleach')
if decoded and #decoded > 0 then
local bytes = decoded:bytes()
-- The version byte’s most signficant bit is reserved and must be 0.
-- The 4 next bits indicate the type of address and the 3 least significant bits indicate the size of the hash.
local version = bit.band(bytes[1], 128)
local addr_type = bit.rshift(bit.band(bytes[1], 120), 3)
local _ = bit.band(bytes[1], 7) -- hash size
if version == 0 and (addr_type == 0 or addr_type == 8) then
-- TODO: Add checksum validation some day
return true
end
end
end
end
rspamd_config:register_symbol{
name = 'BITCOIN_ADDR',
description = 'Message has a valid bitcoin wallet address',
callback = function(task)
local rspamd_re = require "rspamd_regexp"
local btc_wallet_re = rspamd_re.create_cached('^[13LM][1-9A-Za-z]{25,34}$')
local segwit_wallet_re = rspamd_re.create_cached('^(?:bc1|[13]|(?:[^:]*:))?[qpzry9x8gf2tvdw0s3jn54khce6mua7l]{14,}$', 'i')
local words_matched = {}
local segwit_words_matched = {}
local valid_wallets = {}
for _,part in ipairs(task:get_text_parts() or {}) do
local pw = part:filter_words(btc_wallet_re, 'raw', 3)
if pw and #pw > 0 then
for _,w in ipairs(pw) do
words_matched[#words_matched + 1] = w
end
end
pw = part:filter_words(segwit_wallet_re, 'raw', 3)
if pw and #pw > 0 then
for _,w in ipairs(pw) do
segwit_words_matched[#segwit_words_matched + 1] = w
end
end
end
for _,word in ipairs(words_matched) do
local valid = is_traditional_btc_address(word)
if valid then
valid_wallets[#valid_wallets + 1] = word
end
end
for _,word in ipairs(segwit_words_matched) do
local valid = is_segwit_bech32_address(word)
if valid then
valid_wallets[#valid_wallets + 1] = word
end
end
if #valid_wallets > 0 then
return true,1.0,valid_wallets
end
end,
score = 0.0,
group = 'scams'
}
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