M8: add operational authentication mode

backend/app/core/security.py

@@ -4,6 +4,7 @@ import base64
 import hashlib
 import hmac
 import json
+import os
 import time
 from dataclasses import dataclass
 
@@ -50,3 +51,31 @@ def read_session_token(token: str) -> SessionPayload | None:
     if time.time() - payload.issued_at > settings.session_ttl_seconds:
         return None
     return payload
+
+
+def hash_password(password: str) -> str:
+    salt = os.urandom(16)
+    derived = hashlib.scrypt(password.encode(), salt=salt, n=2**14, r=8, p=1, dklen=32)
+    encoded_salt = base64.urlsafe_b64encode(salt).decode()
+    encoded_hash = base64.urlsafe_b64encode(derived).decode()
+    return f"scrypt$16384$8$1${encoded_salt}${encoded_hash}"
+
+
+def verify_password(password: str, encoded: str | None) -> bool:
+    if not encoded:
+        return False
+    try:
+        algorithm, n, r, p, salt, expected = encoded.split("$")
+        if algorithm != "scrypt":
+            return False
+        derived = hashlib.scrypt(
+            password.encode(),
+            salt=base64.urlsafe_b64decode(salt.encode()),
+            n=int(n),
+            r=int(r),
+            p=int(p),
+            dklen=32,
+        )
+        return hmac.compare_digest(derived, base64.urlsafe_b64decode(expected.encode()))
+    except (ValueError, TypeError):
+        return False