fix: price fiat keypad sales on the server; no 1 sat/unit rate fallback

services.py

@@ -36,6 +36,16 @@ async def ensure_tpos_tabs_access(tpos: Tpos) -> str:
     return user_id
 
 
+async def tpos_fiat_as_satoshis(amount: float, currency: str) -> int:
+    try:
+        return await fiat_amount_as_satoshis(amount, currency)
+    except ValueError as exc:
+        raise HTTPException(
+            HTTPStatus.SERVICE_UNAVAILABLE,
+            "Exchange rate not available. Please try again later.",
+        ) from exc
+
+
 async def validate_tpos_sale_amount(
     tpos: Tpos, data: CreateTposInvoice, amount: float, *, minimum: bool = False
 ) -> None:
@@ -56,7 +66,7 @@ async def validate_tpos_sale_amount(
         )
     if minimum:
         amount = max(supplied, amount)
-    data.amount = await fiat_amount_as_satoshis(amount, tpos.currency)
+    data.amount = await tpos_fiat_as_satoshis(amount, tpos.currency)
     if data.amount <= 0:
         raise HTTPException(HTTPStatus.BAD_REQUEST, "Sale amount is below one satoshi.")
     data.amount_fiat = amount

static/js/tpos.js

@@ -29,7 +29,7 @@ window.app = Vue.createApp({
       withdrawMaximum: 0,
       tip_options: null,
       exchangeRateLoaded: false,
-      exchangeRate: 1,
+      exchangeRate: 0,
       stack: [],
       tipAmount: 0.0,
       tipRounding: null,
@@ -1687,6 +1687,7 @@ window.app = Vue.createApp({
         }
       } catch (e) {
         console.error(e)
+        rate = 0
       } finally {
         Quasar.Loading.hide()
         this.exchangeRate = rate
@@ -1701,15 +1702,18 @@ window.app = Vue.createApp({
             let last = [...res.data]
             this.lastPaymentsDialog.data = last.map(obj => {
               obj.dateFrom = moment(obj.time).fromNow()
-              if (obj.currency != g.settings.denomination) {
+              const paidRate = obj.exchange_rate || this.exchangeRate
+              if (obj.currency != g.settings.denomination && paidRate) {
                 obj.amountFiat = this.formatAmount(
-                  obj.amount / 1000 / (obj.exchange_rate || this.exchangeRate),
-                  this.currency
-                )
-                obj.amountFiatNow = this.formatAmount(
-                  Math.abs(obj.amount) / 1000 / this.exchangeRate,
+                  obj.amount / 1000 / paidRate,
                   this.currency
                 )
+                obj.amountFiatNow = this.exchangeRate
+                  ? this.formatAmount(
+                      Math.abs(obj.amount) / 1000 / this.exchangeRate,
+                      this.currency
+                    )
+                  : null
               }
               return obj
             })

templates/tpos/dialogs.html

@@ -180,6 +180,7 @@ <h5 class="q-mt-none q-mb-sm">
               <q-item-label v-if="payment.amountFiat">
                 <span class="text-bold" v-text="payment.amountFiat"></span>
                 <span
+                  v-if="payment.amountFiatNow"
                   class="text-italic q-ml-sm"
                   v-text="`(${payment.amountFiatNow})`"
                 >

tests/test_api.py

@@ -25,6 +25,7 @@
     get_tab_settlements,
 )
 
+import tpos.services as services  # type: ignore[import]
 import tpos.tasks as tpos_tasks  # type: ignore[import]
 import tpos.views_api as views_api  # type: ignore[import]
 import tpos.views_atm as views_atm  # type: ignore[import]
@@ -478,6 +479,9 @@ async def fake_websocket_updater(channel, message):
         sent_messages.append((channel, json.loads(message)))
 
     monkeypatch.setattr(views_payments, "websocket_updater", fake_websocket_updater)
+    monkeypatch.setattr(
+        services, "fiat_amount_as_satoshis", AsyncMock(return_value=36800)
+    )
     invoice_response = await client.post(
         f"/tpos/api/v1/tposs/{tpos['id']}/invoices",
         json={

tests/test_security.py

@@ -492,6 +492,68 @@ async def convert(value, _currency):
     assert (await client.get(f"{base}/tabs")).json()["data"] == []
 
 
+@pytest.mark.asyncio
+async def test_fiat_keypad_sale_uses_server_rate(client, monkeypatch):
+    _, _, pos = await terminal(client, currency="BRL")
+    url = f"/tpos/api/v1/tposs/{pos['id']}/invoices"
+
+    async def convert(value, _currency):
+        return int(Decimal(str(value)) * 229)
+
+    monkeypatch.setattr(services, "fiat_amount_as_satoshis", convert)
+    # A client whose rate fetch failed and fell back to 1 sat per BRL (#264).
+    data = {
+        "amount": 15,
+        "amount_fiat": 14.45,
+        "exchange_rate": 1,
+    }
+    created = await client.post(url, json=data)
+    assert created.status_code == 201, created.text
+    extra = created.json()["extra"]
+    assert extra["amount"] == 3309
+    assert extra["exchangeRate"] == pytest.approx(3309 / 14.45)
+    assert extra["details"]["exchangeRate"] == pytest.approx(3309 / 14.45)
+
+    async def no_rate(_value, currency):
+        raise ValueError(f"Could not get exchange rate for {currency}.")
+
+    monkeypatch.setattr(services, "fiat_amount_as_satoshis", no_rate)
+    unavailable = await client.post(url, json=data)
+    assert unavailable.status_code == 503
+    assert "Exchange rate not available" in unavailable.text
+
+
+@pytest.mark.asyncio
+async def test_fiat_keypad_sale_tax_uses_repriced_amount(client, monkeypatch):
+    _, _, pos = await terminal(client, currency="BRL", tax_default=10)
+
+    async def convert(value, _currency):
+        return int(Decimal(str(value)) * 229)
+
+    monkeypatch.setattr(services, "fiat_amount_as_satoshis", convert)
+    created = await client.post(
+        f"/tpos/api/v1/tposs/{pos['id']}/invoices",
+        json={"amount": 15, "amount_fiat": 14.45, "exchange_rate": 1},
+    )
+    assert created.status_code == 201, created.text
+    details = created.json()["extra"]["details"]
+    assert details["taxValue"] == pytest.approx(14.45 * 0.1 / 1.1)
+
+
+@pytest.mark.asyncio
+async def test_sats_keypad_sale_amount_is_unchanged(client, monkeypatch):
+    _, _, pos = await terminal(client)
+    convert = AsyncMock(side_effect=AssertionError("no conversion for sats"))
+    monkeypatch.setattr(services, "fiat_amount_as_satoshis", convert)
+    created = await client.post(
+        f"/tpos/api/v1/tposs/{pos['id']}/invoices",
+        json={"amount": 21, "tip_amount": 3},
+    )
+    assert created.status_code == 201, created.text
+    assert created.json()["extra"]["amount"] == 21
+    assert created.json()["extra"]["tip_amount"] == 3
+
+
 @pytest.mark.asyncio
 async def test_fractional_sats_tab_balance_rounds_up_without_changing_balance(client):
     _, _, pos = await terminal(client)

views_payments.py

@@ -87,6 +87,16 @@ async def api_tpos_create_invoice(
                 detail="Provided tags are not allowed for this TPoS.",
             )
 
+    if (
+        tpos.currency.lower() != "sats"
+        and data.amount_fiat is not None
+        and not (data.tab_settlement or inventory_payload or data.pay_in_fiat)
+    ):
+        # Keypad sales: price the sats on the server, so a client that fell back
+        # to a wrong exchange rate can't undercharge. Runs before the
+        # default details, so their tax uses the repriced amount.
+        await validate_tpos_sale_amount(tpos, data, data.amount_fiat)
+
     if not data.details:
         tax_value = 0.0
         if tpos.tax_default and data.exchange_rate: