#51 hmac verification
This commit is contained in:
Mikayla
@@ -7,14 +7,14 @@ local log = require("scada-common.log")
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local insert = table.insert
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---@diagnostic disable-next-line: undefined-field
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local C_ID = os.getComputerID() ---@type integer computer ID
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local COMPUTER_ID = os.getComputerID() ---@type integer computer ID
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local max_distance = nil ---@type number|nil maximum acceptable transmission distance
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local max_distance = nil ---@type number|nil maximum acceptable transmission distance
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---@class comms
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local comms = {}
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comms.version = "2.0.0"
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comms.version = "2.1.0"
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---@enum PROTOCOL
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local PROTOCOL = {
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@@ -149,6 +149,7 @@ function comms.scada_packet()
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dest_addr = comms.BROADCAST,
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seq_num = -1,
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protocol = PROTOCOL.SCADA_MGMT,
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mac = "",
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length = 0,
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payload = {}
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}
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@@ -163,14 +164,13 @@ function comms.scada_packet()
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---@param payload table
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function public.make(dest_addr, seq_num, protocol, payload)
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self.valid = true
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---@diagnostic disable-next-line: undefined-field
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self.src_addr = C_ID
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self.src_addr = COMPUTER_ID
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self.dest_addr = dest_addr
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self.seq_num = seq_num
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self.protocol = protocol
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self.length = #payload
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self.payload = payload
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self.raw = { self.src_addr, self.dest_addr, self.seq_num, self.protocol, self.payload }
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self.raw = { self.src_addr, self.dest_addr, self.seq_num, self.protocol, self.mac, self.payload }
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end
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-- parse in a modem message as a SCADA packet
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@@ -198,43 +198,58 @@ function comms.scada_packet()
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-- log.debug("comms.scada_packet.receive(): discarding packet with distance " .. distance .. " outside of trusted range")
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else
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if type(self.raw) == "table" then
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if #self.raw == 5 then
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if #self.raw == 6 then
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self.src_addr = self.raw[1]
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self.dest_addr = self.raw[2]
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self.seq_num = self.raw[3]
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self.protocol = self.raw[4]
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self.mac = self.raw[5]
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-- element 5 must be a table
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if type(self.raw[5]) == "table" then
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self.length = #self.raw[5]
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self.payload = self.raw[5]
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if type(self.raw[6]) == "table" then
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self.length = #self.raw[6]
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self.payload = self.raw[6]
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end
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else
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self.src_addr = nil
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self.dest_addr = nil
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self.seq_num = nil
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self.protocol = nil
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self.mac = ""
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self.length = 0
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self.payload = {}
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end
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-- check if this packet is destined for this device
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local is_destination = (self.dest_addr == comms.BROADCAST) or (self.dest_addr == C_ID)
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local is_destination = (self.dest_addr == comms.BROADCAST) or (self.dest_addr == COMPUTER_ID)
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self.valid = is_destination and type(self.src_addr) == "number" and type(self.dest_addr) == "number" and
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type(self.seq_num) == "number" and type(self.protocol) == "number" and type(self.payload) == "table"
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self.valid = is_destination and
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type(self.src_addr) == "number" and
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type(self.dest_addr) == "number" and
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type(self.seq_num) == "number" and
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type(self.protocol) == "number" and
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type(self.mac) == "string" and
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type(self.payload) == "table"
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end
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end
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return self.valid
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end
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-- set message authentication code
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function public.set_mac(code)
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self.mac = code
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self.raw = { self.src_addr, self.dest_addr, self.seq_num, self.protocol, self.mac, self.payload }
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end
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-- public accessors --
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---@nodiscard
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function public.modem_event() return self.modem_msg_in end
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---@nodiscard
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function public.raw_sendable() return self.raw end
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---@nodiscard
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function public.raw_verifiable() return { self.src_addr, self.dest_addr, self.seq_num, self.protocol, "", self.payload } end
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---@nodiscard
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function public.local_channel() return self.modem_msg_in.s_channel end
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@@ -253,6 +268,8 @@ function comms.scada_packet()
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---@nodiscard
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function public.protocol() return self.protocol end
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---@nodiscard
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function public.mac() return self.mac end
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---@nodiscard
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function public.length() return self.length end
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---@nodiscard
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function public.data() return self.payload end
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@@ -2,15 +2,13 @@
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-- Cryptographic Communications Engine
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--
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local aes128 = require("lockbox.cipher.aes128")
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local ctr_mode = require("lockbox.cipher.mode.ctr")
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local sha1 = require("lockbox.digest.sha1")
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local md5 = require("lockbox.digest.md5")
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local sha2_256 = require("lockbox.digest.sha2_256")
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local pbkdf2 = require("lockbox.kdf.pbkdf2")
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local hmac = require("lockbox.mac.hmac")
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local zero_pad = require("lockbox.padding.zero")
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local stream = require("lockbox.util.stream")
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local array = require("lockbox.util.array")
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local comms = require("scada-common.comms")
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local log = require("scada-common.log")
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local util = require("scada-common.util")
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@@ -19,136 +17,56 @@ local crypto = {}
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local c_eng = {
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key = nil,
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cipher = nil,
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decipher = nil,
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hmac = nil
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}
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---@alias hex string
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-- initialize cryptographic system
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function crypto.init(password, server_port)
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function crypto.init(password)
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local key_deriv = pbkdf2()
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-- setup PBKDF2
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-- the primary goal is to just turn our password into a 16 byte key
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key_deriv.setPassword(password)
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key_deriv.setSalt("salty_salt_at_" .. server_port)
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key_deriv.setSalt("pepper")
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key_deriv.setIterations(32)
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key_deriv.setBlockLen(8)
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key_deriv.setDKeyLen(16)
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local start = util.time()
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local start = util.time_ms()
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key_deriv.setPRF(hmac().setBlockSize(64).setDigest(sha2_256))
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key_deriv.finish()
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log.dmesg("pbkdf2: key derivation took " .. (util.time() - start) .. "ms", "CRYPTO", colors.yellow)
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local message = "pbkdf2 key derivation took " .. (util.time_ms() - start) .. "ms"
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log.dmesg(message, "CRYPTO", colors.yellow)
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log.info("crypto.init: " .. message)
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c_eng.key = array.fromHex(key_deriv.asHex())
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-- initialize cipher
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c_eng.cipher = ctr_mode.Cipher()
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c_eng.cipher.setKey(c_eng.key)
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c_eng.cipher.setBlockCipher(aes128)
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c_eng.cipher.setPadding(zero_pad)
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-- initialize decipher
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c_eng.decipher = ctr_mode.Decipher()
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c_eng.decipher.setKey(c_eng.key)
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c_eng.decipher.setBlockCipher(aes128)
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c_eng.decipher.setPadding(zero_pad)
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-- initialize HMAC
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c_eng.hmac = hmac()
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c_eng.hmac.setBlockSize(64)
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c_eng.hmac.setDigest(sha1)
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c_eng.hmac.setDigest(md5)
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c_eng.hmac.setKey(c_eng.key)
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log.dmesg("init: completed in " .. (util.time() - start) .. "ms", "CRYPTO", colors.yellow)
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end
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-- encrypt plaintext
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---@nodiscard
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---@param plaintext string
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---@return table initial_value, string ciphertext
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function crypto.encrypt(plaintext)
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local start = util.time()
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-- initial value
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local iv = {
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math.random(0, 255),
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math.random(0, 255),
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math.random(0, 255),
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math.random(0, 255),
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math.random(0, 255),
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math.random(0, 255),
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math.random(0, 255),
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math.random(0, 255),
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math.random(0, 255),
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math.random(0, 255),
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math.random(0, 255),
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math.random(0, 255),
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math.random(0, 255),
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math.random(0, 255),
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math.random(0, 255),
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math.random(0, 255)
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}
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log.debug("crypto.random: iv random took " .. (util.time() - start) .. "ms")
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start = util.time()
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c_eng.cipher.init()
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c_eng.cipher.update(stream.fromArray(iv))
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c_eng.cipher.update(stream.fromString(plaintext))
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c_eng.cipher.finish()
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local ciphertext = c_eng.cipher.asHex() ---@type hex
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log.debug("crypto.encrypt: aes128-ctr-mode took " .. (util.time() - start) .. "ms")
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log.debug("ciphertext: " .. util.strval(ciphertext))
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return iv, ciphertext
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end
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-- decrypt ciphertext
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---@nodiscard
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---@param iv string CTR initial value
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---@param ciphertext string ciphertext hex
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---@return string plaintext
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function crypto.decrypt(iv, ciphertext)
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local start = util.time()
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c_eng.decipher.init()
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c_eng.decipher.update(stream.fromArray(iv))
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c_eng.decipher.update(stream.fromHex(ciphertext))
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c_eng.decipher.finish()
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local plaintext_hex = c_eng.decipher.asHex() ---@type hex
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local plaintext = stream.toString(stream.fromHex(plaintext_hex))
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log.debug("crypto.decrypt: aes128-ctr-mode took " .. (util.time() - start) .. "ms")
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log.debug("plaintext: " .. util.strval(plaintext))
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return plaintext
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message = "init: completed in " .. (util.time_ms() - start) .. "ms"
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log.dmesg(message, "CRYPTO", colors.yellow)
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log.info("crypto." .. message)
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end
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-- generate HMAC of message
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---@nodiscard
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---@param message_hex string initial value concatenated with ciphertext
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function crypto.hmac(message_hex)
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local start = util.time()
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---@param message string initial value concatenated with ciphertext
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function crypto.hmac(message)
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local start = util.time_ms()
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c_eng.hmac.init()
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c_eng.hmac.update(stream.fromHex(message_hex))
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c_eng.hmac.update(stream.fromString(message))
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c_eng.hmac.finish()
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local hash = c_eng.hmac.asHex() ---@type hex
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local hash = c_eng.hmac.asHex()
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log.debug("crypto.hmac: hmac-sha1 took " .. (util.time() - start) .. "ms")
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log.debug("hmac: " .. util.strval(hash))
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log.debug("crypto.hmac: hmac-md5 took " .. (util.time_ms() - start) .. "ms")
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log.debug("crypto.hmac: hmac = " .. util.strval(hash))
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return hash
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end
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@@ -173,7 +91,6 @@ function crypto.secure_modem(modem)
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-- wrap a modem
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---@param reconnected_modem table
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---@diagnostic disable-next-line: redefined-local
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function public.wrap(reconnected_modem)
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modem = reconnected_modem
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for key, func in pairs(modem) do
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@@ -184,58 +101,49 @@ function crypto.secure_modem(modem)
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-- wrap modem functions, then we replace transmit
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public.wrap(modem)
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-- send a packet with encryption
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---@param channel integer
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---@param reply_channel integer
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---@param payload table packet raw_sendable
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function public.transmit(channel, reply_channel, payload)
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local plaintext = textutils.serialize(payload, { allow_repetitions = true, compact = true })
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-- send a packet with message authentication
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---@param packet scada_packet packet raw_sendable
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function public.transmit(packet)
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local start = util.time_ms()
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local message = textutils.serialize(packet.raw_verifiable(), { allow_repetitions = true, compact = true })
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local computed_hmac = crypto.hmac(message)
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local iv, ciphertext = crypto.encrypt(plaintext)
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---@diagnostic disable-next-line: redefined-local
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local computed_hmac = crypto.hmac(iv .. ciphertext)
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packet.set_mac(computed_hmac)
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modem.transmit(channel, reply_channel, { computed_hmac, iv, ciphertext })
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log.debug("crypto.transmit: data processing took " .. (util.time_ms() - start) .. "ms")
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modem.transmit(packet.remote_channel(), packet.local_channel(), packet.raw_sendable())
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end
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-- parse in a modem message as a network packet
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---@nodiscard
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---@param side string modem side
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---@param sender integer sender port
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---@param reply_to integer reply port
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---@param message any encrypted packet sent with secure_modem.transmit
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---@param sender integer sender channel
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---@param reply_to integer reply channel
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---@param message any packet sent with message authentication
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---@param distance integer transmission distance
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---@return string side, integer sender, integer reply_to, any plaintext_message, integer distance
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---@return scada_packet|nil packet received packet if valid and passed authentication check
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function public.receive(side, sender, reply_to, message, distance)
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local body = ""
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local packet = nil
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local s_packet = comms.scada_packet()
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if type(message) == "table" then
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if #message == 3 then
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---@diagnostic disable-next-line: redefined-local
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local rx_hmac = message[1]
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local iv = message[2]
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local ciphertext = message[3]
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-- parse packet as generic SCADA packet
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s_packet.receive(side, sender, reply_to, message, distance)
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local computed_hmac = crypto.hmac(iv .. ciphertext)
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if s_packet.is_valid() then
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local start = util.time_ms()
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local packet_hmac = s_packet.mac()
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local computed_hmac = crypto.hmac(textutils.serialize(s_packet.raw_verifiable(), { allow_repetitions = true, compact = true }))
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if rx_hmac == computed_hmac then
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-- message intact
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local plaintext = crypto.decrypt(iv, ciphertext)
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body = textutils.unserialize(plaintext)
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if body == nil then
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-- failed decryption
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log.debug("crypto.secure_modem: decryption failed")
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body = ""
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end
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else
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-- something went wrong
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log.debug("crypto.secure_modem: hmac mismatch violation")
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end
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if packet_hmac == computed_hmac then
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log.debug("crypto.secure_modem.receive: HMAC verified in " .. (util.time_ms() - start) .. "ms")
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packet = s_packet
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else
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log.debug("crypto.secure_modem.receive: HMAC failed verification in " .. (util.time_ms() - start) .. "ms")
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end
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end
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return side, sender, reply_to, body, distance
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return packet
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end
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return public
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