115 lines
2.5 KiB
Lua
115 lines
2.5 KiB
Lua
local expect = require "cc.expect".expect
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local blake3 = require "ccryptolib.blake3"
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local chacha20 = require "ccryptolib.chacha20"
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local packing = require "ccryptolib.internal.packing"
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local u1x4, fmt1x4 = packing.compileUnpack("<I4")
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-- Initialize from local context.
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local ctx = {
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"ccryptolib 2022-03-05T08:50:36Z random.lua initialization context",
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os.epoch("utc"),
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math.random(0, 2 ^ 24 - 1),
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math.random(0, 2 ^ 24 - 1),
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tostring({}),
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tostring({}),
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}
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local state = blake3.digest(table.concat(ctx, "|"))
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local accumulator = {}
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local accumulatorLen = 0
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--- Adds data to the accumulator without context.
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--
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-- @tparam string data The input bytes.
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--
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local function reseed(data)
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local acc = accumulator
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local len = accumulatorLen
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-- Append to the accumulator.
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acc[#acc + 1] = data
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len = len + #data
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if len < 64 then
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accumulatorLen = len
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return
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end
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-- Concatenate.
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local cat = table.concat(acc)
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-- Align by 64-byte block.
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local rlen = len % 64
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local blen = len - rlen
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-- Digest.
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state = blake3.digestKeyed(state, cat:sub(1, blen))
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accumulator = {cat:sub(blen + 1)}
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accumulatorLen = rlen
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end
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do -- Load entropy from disk.
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local file = fs.open("/.random", "rb")
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if file then
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reseed(file.read(32) or "")
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file.close()
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end
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end
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local mod = {}
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--- Adds entropy into the generator state.
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--
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-- @tparam string data The entropy data.
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--
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function mod.reseed(data)
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expect(1, data, "string")
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reseed(data)
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end
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--- Adds entropy from sampling system noise.
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--
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-- @tparam number n The number of iterations to spend extracting entropy.
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--
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function mod.stir(n)
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expect(1, n, "number")
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error("TODO") -- TODO
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end
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--- Generates random bytes.
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--
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-- @tparam number len The desired output length.
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--
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function mod.random(len)
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local msg = ("\0"):rep(len + 32)
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local nonce = ("\0"):rep(12)
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local out = chacha20.crypt(state, nonce, msg, 8, 0)
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state = out:sub(1, 32)
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return out:sub(33)
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end
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local random = mod.random
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--- Saves the state to the filesystem.
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--
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-- This potentially adds security when starting the generator from boot. The
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-- saved path is fixed and located at `/.random`.
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--
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function mod.save()
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local file = fs.open("/.random", "wb")
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file.write(random(32))
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file.close()
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end
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-- Add extra entropy.
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mod.stir(error("TODO")) -- TODO
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-- Save.
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mod.save()
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-- Regenerate the math.random seed.
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math.randomseed(u1x4(fmt1x4, random(4), 1))
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return mod
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