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local crypto = require "util.crypto";
local json = require "util.json";
local hashes = require "util.hashes";
local base64_encode = require "util.encodings".base64.encode;
local base64_decode = require "util.encodings".base64.decode;
local secure_equals = require "util.hashes".equals;
local bit = require "util.bitcompat";
local hex = require "util.hex";
local rand = require "util.random";
local s_pack = require "util.struct".pack;
local s_gsub = string.gsub;
local v4_public = {};
local b64url_rep = { ["+"] = "-", ["/"] = "_", ["="] = "", ["-"] = "+", ["_"] = "/" };
local function b64url(data)
return (s_gsub(base64_encode(data), "[+/=]", b64url_rep));
end
local valid_tails = {
nil; -- Always invalid
"^.[AQgw]$"; -- b??????00
"^..[AQgwEUk0IYo4Mcs8]$"; -- b????0000
}
local function unb64url(data)
local rem = #data%4;
if data:sub(-1,-1) == "=" or rem == 1 or (rem > 1 and not data:sub(-rem):match(valid_tails[rem])) then
return nil;
end
return base64_decode(s_gsub(data, "[-_]", b64url_rep).."==");
end
local function le64(n)
return s_pack("<I8", bit.band(n, 0x7F));
end
local function pae(parts)
if type(parts) ~= "table" then
error("bad argument #1 to 'pae' (table expected, got "..type(parts)..")");
end
local o = { le64(#parts) };
for _, part in ipairs(parts) do
table.insert(o, le64(#part)..part);
end
return table.concat(o);
end
function v4_public.sign(m, sk, f, i)
if type(m) ~= "table" then
return nil, "PASETO payloads must be a table";
end
m = json.encode(m);
local h = "v4.public.";
local m2 = pae({ h, m, f or "", i or "" });
local sig = crypto.ed25519_sign(sk, m2);
if not f or f == "" then
return h..b64url(m..sig);
else
return h..b64url(m..sig).."."..b64url(f);
end
end
function v4_public.verify(tok, pk, expected_f, i)
local h, sm, f = tok:match("^(v4%.public%.)([^%.]+)%.?(.*)$");
if not h then
return nil, "invalid-token-format";
end
f = f and unb64url(f) or nil;
if expected_f then
if not f or not secure_equals(expected_f, f) then
return nil, "invalid-footer";
end
end
local raw_sm = unb64url(sm);
if not raw_sm or #raw_sm <= 64 then
return nil, "invalid-token-format";
end
local s, m = raw_sm:sub(-64), raw_sm:sub(1, -65);
local m2 = pae({ h, m, f or "", i or "" });
local ok = crypto.ed25519_verify(pk, m2, s);
if not ok then
return nil, "invalid-token";
end
local payload, err = json.decode(m);
if err ~= nil or type(payload) ~= "table" then
return nil, "json-decode-error";
end
return payload;
end
v4_public.import_private_key = crypto.import_private_pem;
v4_public.import_public_key = crypto.import_public_pem;
function v4_public.new_keypair()
return crypto.generate_ed25519_keypair();
end
function v4_public.init(private_key_pem, public_key_pem, options)
local sign, verify = v4_public.sign, v4_public.verify;
local public_key = public_key_pem and v4_public.import_public_key(public_key_pem);
local private_key = private_key_pem and v4_public.import_private_key(private_key_pem);
local default_footer = options and options.default_footer;
local default_assertion = options and options.default_implicit_assertion;
return private_key and function (token, token_footer, token_assertion)
return sign(token, private_key, token_footer or default_footer, token_assertion or default_assertion);
end, public_key and function (token, expected_footer, token_assertion)
return verify(token, public_key, expected_footer or default_footer, token_assertion or default_assertion);
end;
end
function v4_public.new_signer(private_key_pem, options)
return (v4_public.init(private_key_pem, nil, options));
end
function v4_public.new_verifier(public_key_pem, options)
return (select(2, v4_public.init(nil, public_key_pem, options)));
end
local v3_local = { _key_mt = {} };
local function v3_local_derive_keys(k, n)
local tmp = hashes.hkdf_hmac_sha384(48, k, nil, "paseto-encryption-key"..n);
local Ek = tmp:sub(1, 32);
local n2 = tmp:sub(33);
local Ak = hashes.hkdf_hmac_sha384(48, k, nil, "paseto-auth-key-for-aead"..n);
return Ek, Ak, n2;
end
function v3_local.encrypt(m, k, f, i)
assert(#k == 32)
if type(m) ~= "table" then
return nil, "PASETO payloads must be a table";
end
m = json.encode(m);
local h = "v3.local.";
local n = rand.bytes(32);
local Ek, Ak, n2 = v3_local_derive_keys(k, n);
local c = crypto.aes_256_ctr_encrypt(Ek, n2, m);
local m2 = pae({ h, n, c, f or "", i or "" });
local t = hashes.hmac_sha384(Ak, m2);
if not f or f == "" then
return h..b64url(n..c..t);
else
return h..b64url(n..c..t).."."..b64url(f);
end
end
function v3_local.decrypt(tok, k, expected_f, i)
assert(#k == 32)
local h, sm, f = tok:match("^(v3%.local%.)([^%.]+)%.?(.*)$");
if not h then
return nil, "invalid-token-format";
end
f = f and unb64url(f) or nil;
if expected_f then
if not f or not secure_equals(expected_f, f) then
return nil, "invalid-footer";
end
end
local m = unb64url(sm);
if not m or #m <= 80 then
return nil, "invalid-token-format";
end
local n, c, t = m:sub(1, 32), m:sub(33, -49), m:sub(-48);
local Ek, Ak, n2 = v3_local_derive_keys(k, n);
local preAuth = pae({ h, n, c, f or "", i or "" });
local t2 = hashes.hmac_sha384(Ak, preAuth);
if not secure_equals(t, t2) then
return nil, "invalid-token";
end
local m2 = crypto.aes_256_ctr_decrypt(Ek, n2, c);
if not m2 then
return nil, "invalid-token";
end
local payload, err = json.decode(m2);
if err ~= nil or type(payload) ~= "table" then
return nil, "json-decode-error";
end
return payload;
end
function v3_local.new_key()
return "secret-token:paseto.v3.local:"..hex.encode(rand.bytes(32));
end
function v3_local.init(key, options)
local encoded_key = key:match("^secret%-token:paseto%.v3%.local:(%x+)$");
if not encoded_key or #encoded_key ~= 64 then
return error("invalid key for v3.local");
end
local raw_key = hex.decode(encoded_key);
local default_footer = options and options.default_footer;
local default_assertion = options and options.default_implicit_assertion;
return function (token, token_footer, token_assertion)
return v3_local.encrypt(token, raw_key, token_footer or default_footer, token_assertion or default_assertion);
end, function (token, token_footer, token_assertion)
return v3_local.decrypt(token, raw_key, token_footer or default_footer, token_assertion or default_assertion);
end;
end
function v3_local.new_signer(key, options)
return (v3_local.init(key, options));
end
function v3_local.new_verifier(key, options)
return (select(2, v3_local.init(key, options)));
end
return {
pae = pae;
v3_local = v3_local;
v4_public = v4_public;
};
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