Simplify auth to HTTP Basic Auth

app.py

@@ -1,50 +1,73 @@
+import base64
+import hashlib
+import hmac
 import os
 
-from dotenv import load_dotenv
-from flask import Flask, redirect, render_template, request, session, url_for
-
-load_dotenv()
+from flask import Flask, Response, render_template, request
 
 app = Flask(__name__)
-app.secret_key = os.environ["SECRET_KEY"]
 
-SITE_PASSWORD = os.environ["SITE_PASSWORD"]
+PASSWORD_SALT = "fn-resi-v1"
+PASSWORD_HASH = "18194f5e151146895ddd7ff59fcac4f324b2832201df108d1d89cc0ef9d2ebe9"
+AUTH_REALM = "FBN Residential"
+
+
+def _password_matches(candidate):
+    expected = os.environ.get("SITE_PASSWORD")
+    if expected is not None:
+        return hmac.compare_digest(candidate, expected)
+
+    derived = hashlib.pbkdf2_hmac(
+        "sha256",
+        candidate.encode("utf-8"),
+        PASSWORD_SALT.encode("utf-8"),
+        390000,
+    ).hex()
+    return hmac.compare_digest(derived, PASSWORD_HASH)
+
+
+def _unauthorized():
+    return Response(
+        "Authentication required.\n",
+        401,
+        {
+            "WWW-Authenticate": f'Basic realm="{AUTH_REALM}"',
+            "Content-Type": "text/plain; charset=utf-8",
+        },
+    )
+
+
+def _authorized(req):
+    header = req.headers.get("Authorization", "")
+    if not header.startswith("Basic "):
+        return False
+
+    try:
+        decoded = base64.b64decode(header.split(None, 1)[1]).decode("utf-8")
+    except Exception:
+        return False
+
+    _, _, password = decoded.partition(":")
+    if not password:
+        return False
+
+    return _password_matches(password)
 
 
 @app.after_request
 def add_noindex_header(response):
     response.headers["X-Robots-Tag"] = "noindex, nofollow"
+    response.headers["Cache-Control"] = "no-store"
     return response
 
 
 @app.route("/")
 def index():
-    if not session.get("authenticated"):
-        return redirect(url_for("login"))
+    if not _authorized(request):
+        return _unauthorized()
     return render_template("dashboard.html")
 
 
-@app.route("/login", methods=["GET", "POST"])
-def login():
-    if session.get("authenticated"):
-        return redirect(url_for("index"))
-
-    error = None
-    if request.method == "POST":
-        if request.form.get("password") == SITE_PASSWORD:
-            session["authenticated"] = True
-            return redirect(url_for("index"))
-        error = "Wrong password."
-
-    return render_template("login.html", error=error)
-
-
-@app.route("/logout")
-def logout():
-    session.clear()
-    return redirect(url_for("login"))
-
-
 @app.route("/robots.txt")
 def robots():
     return "User-agent: *\nDisallow: /\n", 200, {"Content-Type": "text/plain"}

requirements.txt

@@ -1,3 +1,2 @@
 flask
 gunicorn
-python-dotenv

templates/dashboard.html

@@ -97,7 +97,7 @@
 
 <div style="display:flex;justify-content:space-between;align-items:baseline;">
 <h1>FBN Residential &mdash; Executive Summary</h1>
-<a href="/logout" style="color:var(--muted);font-size:12px;text-decoration:none;">Logout</a>
+<span style="color:var(--muted);font-size:12px;">Protected</span>
 </div>
 <p class="subtitle">As of March 27, 2026 &middot; FY 2023&ndash;2025 &middot; Source: GP</p>