Initial IP session cookie implementation

src/web/middleware/ipsessioncookie.js

@@ -0,0 +1,76 @@
+import path from 'path';
+import fs from 'fs';
+import crypto from 'crypto';
+
+const SALT_PATH = path.resolve(__dirname, '..', '..', '..', 'state', 'ipsessionsalt.json');
+
+var SALT;
+try {
+    SALT = require(SALT_PATH);
+} catch (error) {
+    SALT = crypto.randomBytes(32).toString('base64');
+    fs.writeFileSync(SALT_PATH, SALT);
+}
+
+function sha256(input) {
+    var hash = crypto.createHash("sha256");
+    hash.update(input);
+    return hash.digest("base64");
+}
+
+export function createIPSessionCookie(ip, date) {
+    const hashInput = [
+        ip,
+        date.getTime(),
+        SALT
+    ].join(':');
+
+    return [
+        date.getTime(),
+        sha256(hashInput)
+    ].join(':');
+}
+
+export function verifyIPSessionCookie(ip, cookie) {
+    const parts = cookie.split(':');
+    if (parts.length !== 2) {
+        return false;
+    }
+
+    const timestamp = parseInt(parts[0], 10);
+    if (isNaN(timestamp)) {
+        return false;
+    }
+
+    const date = new Date(timestamp);
+    const expected = createIPSessionCookie(ip, date);
+    if (expected !== cookie) {
+        return false;
+    }
+
+    return {
+        date: date,
+    };
+}
+
+export function ipSessionCookieMiddleware(req, res, next) {
+    var firstSeen = new Date();
+    var hasSession = false;
+    if (req.signedCookies && req.signedCookies['ip-session']) {
+        var sessionMatch = verifyIPSessionCookie(req.realIP, req.signedCookies['ip-session']);
+        if (sessionMatch) {
+            hasSession = true;
+            firstSeen = sessionMatch.date;
+        }
+    }
+
+    if (!hasSession) {
+        res.cookie('ip-session', createIPSessionCookie(req.realIP, firstSeen), {
+            signed: true,
+            httpOnly: true
+        });
+    }
+
+    req.ipSessionFirstSeen = firstSeen;
+    next();
+}