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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
-- HS*** family
local function new_hmac_algorithm(name, hmac)
local static_header = new_static_header(name);
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
local payload, err = json.decode(unb64url(raw_payload));
if err ~= nil then
return nil, "json-decode-error";
end
return true, 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
-- ES*** family
local function new_ecdsa_algorithm(name, c_sign, c_verify)
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 der_sig = c_sign(private_key, signed);
local r, s = crypto.parse_ecdsa_signature(der_sig);
return signed.."."..b64url(r..s);
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
local raw_signature = unb64url(signature);
local der_sig = crypto.build_ecdsa_signature(raw_signature:sub(1, 32), raw_signature:sub(33, 64));
if not der_sig then
return false, "signature-mismatch";
end
local verify_ok = c_verify(public_key, signed, der_sig);
if not verify_ok then
return false, "signature-mismatch";
end
local payload, err = json.decode(unb64url(raw_payload));
if err ~= nil then
return nil, "json-decode-error";
end
return true, payload;
end;
load_public_key = function (public_key_pem)
local key = assert(crypto.import_public_pem(public_key_pem));
assert(key:get_type() == "id-ecPublicKey", "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() == "id-ecPublicKey", "incorrect key type");
return key;
end;
};
end
local algorithms = {
HS256 = new_hmac_algorithm("HS256", hashes.hmac_sha256);
ES256 = new_ecdsa_algorithm("ES256", crypto.ecdsa_sha256_sign, crypto.ecdsa_sha256_verify);
};
local function new_signer(algorithm, key_input)
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;
return function (payload)
return sign(key, payload);
end
end
local function new_verifier(algorithm, key_input)
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;
return function (token)
return verify(key, token);
end
end
return {
new_signer = new_signer;
new_verifier = new_verifier;
-- Deprecated
sign = algorithms.HS256.sign;
verify = algorithms.HS256.verify;
};
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