67 lines
2.2 KiB
Lua
67 lines
2.2 KiB
Lua
local expect = require "cc.expect".expect
|
|
local chacha20 = require "ccryptolib.chacha20"
|
|
local poly1305 = require "ccryptolib.poly1305"
|
|
|
|
local bxor = bit32.bxor
|
|
local bor = bit32.bor
|
|
|
|
local function encrypt(key, nonce, message, aad, rounds)
|
|
expect(1, key, "string")
|
|
assert(#key == 32, "key length must be 32")
|
|
expect(2, nonce, "string")
|
|
assert(#nonce == 12, "nonce length must be 12")
|
|
expect(3, message, "string")
|
|
expect(4, aad, "string")
|
|
expect(5, rounds, "number", "nil")
|
|
rounds = rounds or 20
|
|
|
|
-- Generate auth key and encrypt.
|
|
local msgLong = ("\0"):rep(64) .. message
|
|
local ctxLong = chacha20.crypt(key, nonce, msgLong, rounds, 0)
|
|
local authKey = ctxLong:sub(1, 32)
|
|
local ciphertext = ctxLong:sub(65)
|
|
|
|
-- Authenticate.
|
|
local pad1 = ("\0"):rep(-#aad % 16)
|
|
local pad2 = ("\0"):rep(-#ciphertext % 16)
|
|
local aadLen = ("<I8"):pack(#aad)
|
|
local ctxLen = ("<I8"):pack(#ciphertext)
|
|
local combined = aad .. pad1 .. ciphertext .. pad2 .. aadLen .. ctxLen
|
|
local tag = poly1305.mac(authKey, combined)
|
|
|
|
return ciphertext, tag
|
|
end
|
|
|
|
local function decrypt(key, nonce, tag, ciphertext, aad, rounds)
|
|
expect(1, key, "string")
|
|
assert(#key == 32, "key length must be 32")
|
|
expect(2, nonce, "string")
|
|
assert(#nonce == 12, "nonce length must be 12")
|
|
expect(3, ciphertext, "string")
|
|
expect(4, aad, "string")
|
|
expect(5, rounds, "number", "nil")
|
|
rounds = rounds or 20
|
|
|
|
-- Generate auth key and decrypt.
|
|
local ctxLong = ("\0"):rep(64) .. ciphertext
|
|
local msgLong = chacha20.crypt(key, nonce, ctxLong, rounds, 0)
|
|
local authKey = msgLong:sub(1, 32)
|
|
local message = msgLong:sub(65)
|
|
|
|
-- Check tag.
|
|
local pad1 = ("\0"):rep(-#aad % 16)
|
|
local pad2 = ("\0"):rep(-#ciphertext % 16)
|
|
local aadLen = ("<I8"):pack(#aad)
|
|
local ctxLen = ("<I8"):pack(#ciphertext)
|
|
local combined = aad .. pad1 .. ciphertext .. pad2 .. aadLen .. ctxLen
|
|
local t1, t2, t3, t4 = ("<I4I4I4I4"):unpack(tag)
|
|
local u1, u2, u3, u4 = ("<I4I4I4I4"):unpack(poly1305.mac(authKey, combined))
|
|
local eq = bor(bxor(t1, u1), bxor(t2, u2), bxor(t3, u3), bxor(t4, u4))
|
|
if eq == 0 then return message end
|
|
end
|
|
|
|
return {
|
|
encrypt = encrypt,
|
|
decrypt = decrypt,
|
|
}
|