server side encryption WIP

services/data_encryption.js

@@ -0,0 +1,33 @@
+const protected_session = require('./protected_session');
+const utils = require('./utils');
+const aesjs = require('./aes');
+
+function getProtectedSessionId(req) {
+    return req.headers['x-protected-session-id'];
+}
+
+function getDataAes(dataKey) {
+    return new aesjs.ModeOfOperation.ctr(dataKey, new aesjs.Counter(5));
+}
+
+function decrypt(dataKey, encryptedBase64) {
+    if (!dataKey) {
+        return "[protected]";
+    }
+
+    const aes = getDataAes(dataKey);
+
+    const encryptedBytes = utils.fromBase64(encryptedBase64);
+
+    const decryptedBytes = aes.decrypt(encryptedBytes);
+
+    const digest = decryptedBytes.slice(0, 4);
+    const payload = decryptedBytes.slice(4);
+
+    return aesjs.utils.utf8.fromBytes(payload);
+}
+
+module.exports = {
+    getProtectedSessionId,
+    decrypt
+};