Change settle endpoint to use POST instead of GET

This is necessary to avoid XSS.  State-changing actions should never be
done with a GET.

ihatemoney/forms.py

@@ -14,6 +14,8 @@ from wtforms.fields import (
     BooleanField,
     DateField,
     DecimalField,
+    HiddenField,
+    IntegerField,
     Label,
     PasswordField,
     SelectField,
@@ -437,6 +439,22 @@ class BillForm(FlaskForm):
             raise ValidationError(msg)
 
 
+class HiddenCommaDecimalField(HiddenField, CommaDecimalField):
+    pass
+
+
+class HiddenIntegerField(HiddenField, IntegerField):
+    pass
+
+
+class SettlementForm(FlaskForm):
+    """Used internally for validation, not directly visible to users"""
+
+    amount = HiddenCommaDecimalField("Amount", validators=[DataRequired()])
+    sender_id = HiddenIntegerField("Sender", validators=[DataRequired()])
+    receiver_id = HiddenIntegerField("Receiver", validators=[DataRequired()])
+
+
 class MemberForm(FlaskForm):
     name = StringField(_("Name"), validators=[DataRequired()], filters=[strip_filter])
 

ihatemoney/templates/settle_bills.html

@@ -18,14 +18,24 @@
       <td>{{ transaction.amount|currency }}</td>
       <td>
         <span id="settle-bill" class="ml-auto pb-2">
+          <form class="" action="{{ url_for(".add_settlement_bill") }}" method="POST">
+              {{ settlement_form.csrf_token }}
+              {{ settlement_form.amount(value=transaction.amount) }}
+              {{ settlement_form.sender_id(value=transaction.ower.id) }}
+              {{ settlement_form.receiver_id(value=transaction.receiver.id) }}
+              <button class="btn btn-primary" type="submit" title="{{ _("Settle") }}">
+                <div
+                  data-toggle="tooltip"
+                  title='{{ _("Click here to record that the money transfer has been done") }}'
+                >
+                {{ _("Settle") }}
+                </div>
+              </button>
+          </form>
           <a
             href="{{ url_for('.add_settlement_bill', amount = transaction.amount, sender_id = transaction.ower.id, receiver_id = transaction.receiver.id) }}"
             class="btn btn-primary"
           >
-            <div
-              data-toggle="tooltip"
-              title='{{ _("Click here to record that the money transfer has been done") }}'
-            >
               {{ ("Settle") }}
             </div>
           </a>

ihatemoney/tests/budget_test.py

@@ -1358,23 +1358,25 @@ class TestBudget(IhatemoneyTestCase):
         count = 0
         for t in transactions:
             count += 1
-            self.client.get(
-                "/raclette/settle"
-                + "/"
-                + str(t["amount"])
-                + "/"
-                + str(t["ower"].id)
-                + "/"
-                + str(t["receiver"].id)
+            self.client.post(
+                "/raclette/settle",
+                data={
+                    "amount": t["amount"],
+                    "sender_id": t["ower"].id,
+                    "receiver_id": t["receiver"].id,
+                },
             )
             temp_transactions = project.get_transactions_to_settle_bill()
             # test if the one has disappeared
             assert len(temp_transactions) == len(transactions) - count
 
-            # test if theres a new one with bill_type reimbursement
+            # test if there is a new one with bill_type reimbursement
             bill = project.get_newest_bill()
             assert bill.bill_type == models.BillType.REIMBURSEMENT
-        return
+
+        # There should be no more settlement to do at the end
+        transactions = project.get_transactions_to_settle_bill()
+        assert len(transactions) == 0
 
     def test_settle_zero(self):
         self.post_project("raclette")

ihatemoney/web.py

@@ -56,6 +56,7 @@ from ihatemoney.forms import (
     ProjectForm,
     ProjectFormWithCaptcha,
     ResetPasswordForm,
+    SettlementForm,
     get_billform_for,
 )
 from ihatemoney.history import get_history, get_history_queries, purge_history
@@ -853,16 +854,32 @@ def change_lang(lang):
 def settle_bill():
     """Compute the sum each one have to pay to each other and display it"""
     transactions = g.project.get_transactions_to_settle_bill()
-    return render_template("settle_bills.html", transactions=transactions, current_view="settle_bill")
+    settlement_form = SettlementForm()
+    return render_template(
+        "settle_bills.html",
+        transactions=transactions,
+        settlement_form=settlement_form,
+        current_view="settle_bill",
+    )
+
+
+@main.route("/<project_id>/settle", methods=["POST"])
+def add_settlement_bill():
+    """Create a bill to register a settlement"""
+    form = SettlementForm(id=g.project.id)
+    if not form.validate():
+        flash(
+            format_form_errors(form, _("Error creating settlement bill")),
+            category="danger",
+        )
+        return redirect(url_for(".settle_bill"))
 
 
-@main.route("/<project_id>/settle/<amount>/<int:sender_id>/<int:receiver_id>")
-def add_settlement_bill(amount, sender_id, receiver_id):
     settlement = Bill(
-        amount=float(amount),
+        amount=form.amount.data,
         date=datetime.datetime.today(),
-        owers=[Person.query.get(receiver_id)],
-        payer_id=sender_id,
+        owers=[Person.query.get(form.receiver_id.data)],
+        payer_id=form.sender_id.data,
         project_default_currency=g.project.default_currency,
         bill_type=BillType.REIMBURSEMENT,
         what=_("Settlement"),