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local s_gsub = string.gsub;
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 b64url_rep = { ["+"] = "-", ["/"] = "_", ["="] = "", ["-"] = "+", ["_"] = "/" };
local function b64url(data)
return (s_gsub(base64_encode(data), "[+/=]", b64url_rep));
end
local function unb64url(data)
return base64_decode(s_gsub(data, "[-_]", b64url_rep).."==");
end
local jwt_pattern = "^(([A-Za-z0-9-_]+)%.([A-Za-z0-9-_]+))%.([A-Za-z0-9-_]+)$"
local function decode_jwt(blob, expected_alg)
local signed, bheader, bpayload, signature = string.match(blob, jwt_pattern);
if not signed then
return nil, "invalid-encoding";
end
local header = json.decode(unb64url(bheader));
if not header or type(header) ~= "table" then
return nil, "invalid-header";
elseif header.alg ~= expected_alg then
return nil, "unsupported-algorithm";
end
return signed, signature, bpayload;
end
local function new_static_header(algorithm_name)
return b64url('{"alg":"'..algorithm_name..'","typ":"JWT"}') .. '.';
end
local function decode_raw_payload(raw_payload)
local payload, err = json.decode(unb64url(raw_payload));
if err ~= nil then
return nil, "json-decode-error";
elseif type(payload) ~= "table" then
return nil, "invalid-payload-type";
end
return true, payload;
end
-- HS*** family
local function new_hmac_algorithm(name)
local static_header = new_static_header(name);
local hmac = hashes["hmac_sha"..name:sub(-3)];
local function sign(key, payload)
local encoded_payload = json.encode(payload);
local signed = static_header .. b64url(encoded_payload);
local signature = hmac(key, signed);
return signed .. "." .. b64url(signature);
end
local function verify(key, blob)
local signed, signature, raw_payload = decode_jwt(blob, name);
if not signed then return nil, signature; end -- nil, err
if not secure_equals(b64url(hmac(key, signed)), signature) then
return false, "signature-mismatch";
end
return decode_raw_payload(raw_payload);
end
local function load_key(key)
assert(type(key) == "string", "key must be string (long, random, secure)");
return key;
end
return { sign = sign, verify = verify, load_key = load_key };
end
local function new_crypto_algorithm(name, key_type, c_sign, c_verify, sig_encode, sig_decode)
local static_header = new_static_header(name);
return {
sign = function (private_key, payload)
local encoded_payload = json.encode(payload);
local signed = static_header .. b64url(encoded_payload);
local signature = c_sign(private_key, signed);
if sig_encode then
signature = sig_encode(signature);
end
return signed.."."..b64url(signature);
end;
verify = function (public_key, blob)
local signed, signature, raw_payload = decode_jwt(blob, name);
if not signed then return nil, signature; end -- nil, err
signature = unb64url(signature);
if sig_decode and signature then
signature = sig_decode(signature);
end
if not signature then
return false, "signature-mismatch";
end
local verify_ok = c_verify(public_key, signed, signature);
if not verify_ok then
return false, "signature-mismatch";
end
return decode_raw_payload(raw_payload);
end;
load_public_key = function (public_key_pem)
local key = assert(crypto.import_public_pem(public_key_pem));
assert(key:get_type() == key_type, "incorrect key type");
return key;
end;
load_private_key = function (private_key_pem)
local key = assert(crypto.import_private_pem(private_key_pem));
assert(key:get_type() == key_type, "incorrect key type");
return key;
end;
};
end
-- RS***, PS***
local rsa_sign_algos = { RS = "rsassa_pkcs1", PS = "rsassa_pss" };
local function new_rsa_algorithm(name)
local family, digest_bits = name:match("^(..)(...)$");
local c_sign = crypto[rsa_sign_algos[family].."_sha"..digest_bits.."_sign"];
local c_verify = crypto[rsa_sign_algos[family].."_sha"..digest_bits.."_verify"];
return new_crypto_algorithm(name, "rsaEncryption", c_sign, c_verify);
end
-- ES***
local function new_ecdsa_algorithm(name, c_sign, c_verify)
local function encode_ecdsa_sig(der_sig)
local r, s = crypto.parse_ecdsa_signature(der_sig);
return r..s;
end
local function decode_ecdsa_sig(jwk_sig)
return crypto.build_ecdsa_signature(jwk_sig:sub(1, 32), jwk_sig:sub(33, 64));
end
return new_crypto_algorithm(name, "id-ecPublicKey", c_sign, c_verify, encode_ecdsa_sig, decode_ecdsa_sig);
end
local algorithms = {
HS256 = new_hmac_algorithm("HS256"), HS384 = new_hmac_algorithm("HS384"), HS512 = new_hmac_algorithm("HS512");
ES256 = new_ecdsa_algorithm("ES256", crypto.ecdsa_sha256_sign, crypto.ecdsa_sha256_verify);
RS256 = new_rsa_algorithm("RS256"), RS384 = new_rsa_algorithm("RS384"), RS512 = new_rsa_algorithm("RS512");
PS256 = new_rsa_algorithm("PS256"), PS384 = new_rsa_algorithm("PS384"), PS512 = new_rsa_algorithm("PS512");
};
local function new_signer(algorithm, key_input, options)
local impl = assert(algorithms[algorithm], "Unknown JWT algorithm: "..algorithm);
local key = (impl.load_private_key or impl.load_key)(key_input);
local sign = impl.sign;
local default_ttl = (options and options.default_ttl) or 3600;
return function (payload)
local issued_at;
if not payload.iat then
issued_at = os.time();
payload.iat = issued_at;
end
if not payload.exp then
payload.exp = (issued_at or os.time()) + default_ttl;
end
return sign(key, payload);
end
end
local function new_verifier(algorithm, key_input, options)
local impl = assert(algorithms[algorithm], "Unknown JWT algorithm: "..algorithm);
local key = (impl.load_public_key or impl.load_key)(key_input);
local verify = impl.verify;
local check_expiry = not (options and options.accept_expired);
local claim_verifier = options and options.claim_verifier;
return function (token)
local ok, payload = verify(key, token);
if ok then
local expires_at = check_expiry and payload.exp;
if expires_at then
if type(expires_at) ~= "number" then
return nil, "invalid-expiry";
elseif expires_at < os.time() then
return nil, "token-expired";
end
end
if claim_verifier and not claim_verifier(payload) then
return nil, "incorrect-claims";
end
end
return ok, payload;
end
end
local function init(algorithm, private_key, public_key, options)
return new_signer(algorithm, private_key, options), new_verifier(algorithm, public_key or private_key, options);
end
return {
init = init;
new_signer = new_signer;
new_verifier = new_verifier;
-- Exported mainly for tests
_algorithms = algorithms;
-- Deprecated
sign = algorithms.HS256.sign;
verify = algorithms.HS256.verify;
};
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