Add user passwords (#301) (#308)

* add password fields to schema

* add password related config options

* add ability to set password

* add hidden fields

* password prompt at login

* rearchitect login to use callbacks

* add password check to stockterminal

* update tillweb

* handle hotkeypress() in password prompt

* force setting password on login if required

* add password-only logon

* update last seen when logging in with password

* show user ID in edit dialogs

* clear last_successful_login when tokens are (re)assigned

* allow users to remove their own passwords

quicktill/keyboard.py

@@ -117,6 +117,7 @@ def __repr__(self):
 keycode("K_PRICECHECK", "Price Check")
 keycode("K_LOCK", "Lock")
 keycode("K_ONLINE_ORDERS", "Online Orders")
+keycode("K_PASS_LOGON", "Log On")
 
 # Tendering keys referred to in the code
 keycode("K_CASH", "Cash / Enter")

quicktill/localutils.py

@@ -40,6 +40,7 @@
     K_LOCK,
     K_QUANTITY,
     K_DRINKIN,
+    K_PASS_LOGON,
     Key,
     notekey,
     paymentkey,
@@ -507,6 +508,7 @@ def global_hotkeys(register_hotkeys, stockterminal_location=["Bar"]):
         K_STOCKTERMINAL: lambda: stockterminal.page(
             register_hotkeys, stockterminal_location),
         K_LOCK: lockscreen.lockpage,
+        K_PASS_LOGON: lambda: tillconfig.passlogon_handler(),
     }
 
 
@@ -523,6 +525,13 @@ def activate_register_with_usertoken(register_hotkeys, timeout=300):
     }
 
 
+def activate_register_with_password(register_hotkeys, timeout=300):
+    return {
+        'passlogon_handler': lambda: register.handle_passlogon(
+            register_hotkeys, autolock=K_LOCK, timeout=timeout),
+    }
+
+
 def activate_stockterminal_with_usertoken(
         register_hotkeys,
         stockterminal_location=["Bar"],
@@ -539,6 +548,16 @@ def activate_stockterminal_with_usertoken(
     }
 
 
+def activate_stockterminal_with_password(register_hotkeys,
+                                         stockterminal_location=["Bar"],
+                                         max_unattended_updates=5):
+    return {
+        'passlogon_handler': lambda: stockterminal.handle_passlogon(
+            register_hotkeys, stockterminal_location,
+            max_unattended_updates=max_unattended_updates),
+    }
+
+
 class ServiceCharge(register.RegisterPlugin):
     """Apply a service charge to the current transaction
 

quicktill/models.py

@@ -869,6 +869,7 @@ class User(Base, Logged):
     message = Column(String(), nullable=True,
                      doc="Message to present to user on their next keypress")
     last_seen = Column(DateTime)
+    password = Column(String(), nullable=True)
     groups = relationship("Group", secondary="group_grants", backref="users")
     permissions = relationship(
         "Permission",
@@ -932,6 +933,7 @@ class UserToken(Base, Logged):
     description = Column(String())
     user_id = Column('user', Integer, ForeignKey('users.id'))
     last_seen = Column(DateTime)
+    last_successful_login = Column(DateTime, nullable=True)
     user = relationship(User, backref='tokens')
 
 

quicktill/passwords.py

@@ -0,0 +1,49 @@
+"""Till password hashing and checking logic.
+
+This module provides functions to create 'password tuples' which take the format
+`algorithm$iterations$salt$hash_hex`.
+"""
+
+import secrets
+import hashlib
+
+
+def compute_password_tuple(password):
+    """Computes the password tuple for storage in the database.
+
+    Returns a string in the format `algorithm$iterations$salt$hash_hex`.
+    """
+    iterations = 500_000
+    salt = secrets.token_hex(16)
+    hash = compute_pbkdf2(password, salt, iterations)
+    return f"pbkdf2${iterations}${salt}${hash}"
+
+
+def compute_pbkdf2(value, salt, iterations):
+    """Computes t he PBKDF2 hash for a value given a salt and number of
+    iterations.
+    """
+    hash = hashlib.pbkdf2_hmac("sha256", bytes(value, "utf-8"),
+                               bytes(salt, "utf-8"), iterations)
+    return hash.hex()
+
+
+def check_password(password, tuple):
+    """Checks a password against a tuple.
+
+    The tuple must be in the format `algorithm$iterations$salt$hash_hex`.
+    Malformed values will raise an exception.
+    """
+    elems = tuple.split("$")
+    if len(elems) != 4:
+        raise Exception("Invalid password tuple presented (len(elems) != 4).")
+
+    algo = elems[0]
+    iterations = int(elems[1])
+    salt = elems[2]
+    hash = elems[3]
+
+    if algo == 'pbkdf2':
+        return compute_pbkdf2(password, salt, iterations) == hash
+    else:
+        raise Exception("Unsupported password algorithm: " + algo)

quicktill/register.py

@@ -3443,7 +3443,22 @@ def handle_usertoken(t, *args, **kwargs):
     Used in the configuration file to specify what happens when a user
     token is handled by the default hotkey handler.
     """
-    u = user.user_from_token(t)
+    user.token_login(t,
+                     lambda u: finalize_logon(u, *args, **kwargs))
+
+
+def handle_passlogon(*args, **kwargs):
+    """Password logon handler for the register.
+    """
+    user.password_login(lambda u: finalize_logon(u, *args, **kwargs))
+
+
+def finalize_logon(u, *args, **kwargs):
+    """The other half of handle_usertoken.
+
+    This allows this function to be used as a callback, where, for example,
+    logging in requires some asynchronous user input (like a password).
+    """
     if u is None:
         return
     for p in ui.basicpage._pagelist:

quicktill/stockterminal.py

@@ -184,12 +184,22 @@ def set_location(self, location):
 
 
 def handle_usertoken(t, *args, **kwargs):
-    """
-    Called when a usertoken has been handled by the default hotkey
+    """Called when a usertoken has been handled by the default hotkey
     handler.
+    """
+    user.token_login(t,
+                     lambda u: finalize_logon(u, *args, **kwargs))
+
+
+def handle_passlogon(*args, **kwargs):
+    """Password logon handler for the register.
+    """
+    user.password_login(lambda u: finalize_logon(u, *args, **kwargs))
+
 
+def finalize_logon(u, *args, **kwargs):
+    """a la register.finalize_handle_usertoken
     """
-    u = user.user_from_token(t)
     if u is None:
-        return  # Should already have toasted
+        return
     return page(*args, user=u, **kwargs)

quicktill/till.py

@@ -438,6 +438,8 @@ def main():
             tillconfig.usertoken_listen_v6 = val
         elif opt == 'description':
             tillconfig.configdescription = val
+        elif opt == 'passlogon_handler':
+            tillconfig.passlogon_handler = val
         else:
             log.warning("Unknown configuration option '%s'", opt)
 

quicktill/tillconfig.py

@@ -75,6 +75,11 @@ def usertoken_handler(t):
     pass
 
 
+# Called by UI code whenever the password logon key is pressed
+def passlogon_handler():
+    pass
+
+
 usertoken_listen = None
 usertoken_listen_v6 = None
 

quicktill/tillweb/templates/tillweb/user.html

@@ -155,12 +155,13 @@
 	  <th scope="col">Description</th>
 	  <th scope="col">Value</th>
 	  <th scope="col">Last used</th>
+	  <th scope="col">Last successful login</th>
 	</tr>
       </thead>
       <tbody>
 	{% for t in tuser.tokens %}
 	<tr>
-	  <td>{{t.description}}</td><td>{{t.token}}</td><td>{{t.last_seen|date:dtf}}</td>
+	  <td>{{t.description}}</td><td>{{t.token}}</td><td>{{t.last_seen|date:dtf}}</td><td>{{t.last_successful_login|date:dtf}}</td>
 	</tr>
 	{% endfor %}
       </tbody>

quicktill/ui.py

@@ -1435,9 +1435,11 @@ class editfield(valuefield):
     is passed the proposed new contents and the cursor index, and
     should return either a (potentially updated) string or None if the
     input is not allowed
+
+    hidden: mask value with * characters
     """
     def __init__(self, y, x, w, keymap={}, f=None, flen=None, validate=None,
-                 readonly=False):
+                 readonly=False, hidden=False):
         self.y = y
         self.x = x
         self.w = w
@@ -1450,6 +1452,7 @@ def __init__(self, y, x, w, keymap={}, f=None, flen=None, validate=None,
         self.flen = flen
         self.validate = validate
         self.readonly = readonly
+        self.hidden = hidden
         super().__init__(keymap, f)
 
     # Internal attributes:
@@ -1487,8 +1490,14 @@ def draw(self):
             self.i = self.c
         self.win.clear(self.y, self.x, 1, self.w,
                        colour=self.win.colour.reversed)
-        self.win.addstr(self.y, self.x, self._f[self.i:self.i + self.w],
-                        self.win.colour.reversed)
+
+        if self.hidden:
+            self.win.addstr(self.y, self.x, '*' * (self.c - self.i),
+                            self.win.colour.reversed)
+        else:
+            self.win.addstr(self.y, self.x, self._f[self.i:self.i + self.w],
+                            self.win.colour.reversed)
+
         if self.focused:
             self.win.move(self.y, self.x + self.c - self.i)
         else: