Implement protection from brute-force attacks

The implementation enforces a timeout of one minute after three or
more incorrect login attempts for an account.

Fixes #8

mysql/sql/init.sql

@@ -11,6 +11,8 @@ CREATE TABLE users (
   state VARCHAR(50),
   postal_code VARCHAR(50),
   country VARCHAR(50),
+  login_attempts INT UNSIGNED,
+  last_login_attempt INT UNSIGNED,
   PRIMARY KEY (userid)
 );
 
@@ -84,7 +86,7 @@ CREATE TABLE task_files (
 * Initial data
 */
 
-insert into users values (NULL, "admin", "$2b$12$iKbYZ0MFwWWxoYUXKRhFiOPo7itaQO2DIRnLgXbECsj8XKVzkNCSi", "Admin Modsen", "ntnu", 'mail@ntnu.no', "street", "trondheim", "trondheim", "1234", "norway");
+insert into users values (NULL, "admin", "$2b$12$iKbYZ0MFwWWxoYUXKRhFiOPo7itaQO2DIRnLgXbECsj8XKVzkNCSi", "Admin Modsen", "ntnu", 'mail@ntnu.no', "street", "trondheim", "trondheim", "1234", "norway", 0, 0);
 
 insert into project_category values (NULL, "Gardening");
 insert into project_category values (NULL, "Programming");

src/app/models/register.py

@@ -28,7 +28,7 @@ def set_user(username, password, full_name, company, email,
     """
     db.connect()
     cursor = db.cursor()
-    query = ("INSERT INTO users VALUES (NULL, %s, %s, %s, %s, %s, %s, %s, %s, %s, %s)")
+    query = ("INSERT INTO users VALUES (NULL, %s, %s, %s, %s, %s, %s, %s, %s, %s, %s, 0, 0)")
     try:
         cursor.execute(query, (username, password, full_name, company, email, street_address,
                                city, state, postal_code, country))

src/app/models/user.py

@@ -12,7 +12,7 @@ def get_user(username):
     """
     db.connect()
     cursor = db.cursor()
-    query = ("SELECT userid, username, password from users where username = %s")
+    query = ("SELECT userid, username, password, login_attempts, last_login_attempt from users where username = %s")
     user = None
     try:
         cursor.execute(query, (username,))
@@ -51,6 +51,25 @@ def get_users():
     return users
 
 
+def set_login_attempts(userid, num, timestamp):
+    """
+    Set the number and timestamp of the failed login attempts for the given user.
+    """
+    db.connect()
+    cursor = db.cursor()
+    query = ("UPDATE users SET login_attempts = %s, last_login_attempt = %s WHERE userid = %s")
+    try:
+        cursor.execute(query, (num, timestamp, userid))
+        db.commit()
+    except mysql.connector.Error as err:
+        print("Failed executing query: {}".format(err))
+        cursor.fetchall()
+        exit(1)
+    finally:
+        cursor.close()
+        db.close()
+
+
 def get_user_id_by_name(username):
     """
     Get the id of the unique username

src/app/views/login.py

@@ -14,6 +14,10 @@ render = web.template.render('templates/')
 # The remember cookie should be valid for a week
 remember_timeout = 3600*24*7
 
+# The timeout between login attempts, after the 3rd incorrect one
+login_timeout = 60
+login_attempts_threshold = 2
+
 
 class Login():
 
@@ -47,11 +51,24 @@ class Login():
         # Validate login credential with database query
         user = models.user.get_user(data.username)
 
-        if bcrypt.checkpw(data.password.encode('UTF-8'), user[2].encode('UTF-8')):
-            self.login(user[1], user[0], data.remember)
+        if user is None:
+            return render.login(nav, login_form, "- User authentication failed")
+
+        userid, username, password_hash, login_attempts, last_login_attempt = user
+
+        if login_attempts > login_attempts_threshold and last_login_attempt + login_timeout > time.time():
+            return render.login(nav, login_form, "- There have been too many incorrect login attempts for your account. You have to wait a minute before you can log in.")
+
+        if bcrypt.checkpw(data.password.encode('UTF-8'), password_hash.encode('UTF-8')):
+            models.user.set_login_attempts(userid, 0, time.time())
+            self.login(username, userid, data.remember)
             raise web.seeother("/")
         else:
-            return render.login(nav, login_form, "- User authentication failed")
+            models.user.set_login_attempts(userid, login_attempts+1, time.time())
+            if login_attempts == login_attempts_threshold:
+                return render.login(nav, login_form, "- Too many incorrect login attempts. You have to wait a minute before trying again.")
+            else:
+                return render.login(nav, login_form, "- User authentication failed")
 
     def login(self, username, userid, remember):
         """