Add simple captcha

app/blueprints/users/account.py

@@ -105,11 +105,16 @@ class RegisterForm(FlaskForm):
 					Regexp("^[a-zA-Z0-9._-]+$", message="Only a-zA-Z0-9._ allowed")])
 	email    = StringField("Email", [InputRequired(), Email()])
 	password = PasswordField("Password", [InputRequired(), Length(6, 100)])
-	agree = BooleanField("I agree", [Required()])
+	question  = StringField("What is the result of the above calculation?", [InputRequired()])
+	agree    = BooleanField("I agree", [DataRequired()])
 	submit   = SubmitField("Register")
 
 
 def handle_register(form):
+	if form.question.data.strip().lower() != "19":
+		flash("Incorrect captcha answer", "danger")
+		return
+
 	user_by_name = User.query.filter(or_(
 			User.username == form.username.data,
 			User.username == form.display_name.data,
@@ -168,7 +173,8 @@ def register():
 		if ret:
 			return ret
 
-	return render_template("users/register.html", form=form, suggested_password=genphrase(entropy=52, wordset="bip39"))
+	return render_template("users/register.html", form=form,
+			suggested_password=genphrase(entropy=52, wordset="bip39"))
 
 
 class ForgotPasswordForm(FlaskForm):

app/templates/users/register.html

@@ -32,6 +32,11 @@ Register
 			<code>{{ suggested_password }}</code>
 		</p>
 
+		<p>
+			<img src="/static/puzzle.png" />
+		</p>
+		{{ render_field(form.question, hint=_("Please prove that you are human")) }}
+
 		{% set label %}
 			{{ _("I agree to the ") }}
 			<a href="{{ url_for('flatpage', path='privacy_policy') }} ">