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local s_gsub = string.gsub;
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 static_header = b64url('{"alg":"HS256","typ":"JWT"}') .. '.';
local function sign(key, payload)
local encoded_payload = json.encode(payload);
local signed = static_header .. b64url(encoded_payload);
local signature = hashes.hmac_sha256(key, signed);
return signed .. "." .. b64url(signature);
end
local jwt_pattern = "^(([A-Za-z0-9-_]+)%.([A-Za-z0-9-_]+))%.([A-Za-z0-9-_]+)$"
local function verify(key, blob)
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 ~= "HS256" then
return nil, "unsupported-algorithm";
end
if not secure_equals(b64url(hashes.hmac_sha256(key, signed)), signature) then
return false, "signature-mismatch";
end
local payload, err = json.decode(unb64url(bpayload));
if err ~= nil then
return nil, "json-decode-error";
end
return true, payload;
end
return {
sign = sign;
verify = verify;
};
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