From 3a81cab627289bbdfd7c386ce2b24e217cdc4efa Mon Sep 17 00:00:00 2001
From: Jean-Paul Calderone <exarkun@twistedmatrix.com>
Date: Fri, 15 Nov 2019 10:48:40 -0500
Subject: [PATCH] Teach PaymentController what to do on AlreadySpent errors
---
src/_zkapauthorizer/controller.py | 55 +++++++++++++++++---
src/_zkapauthorizer/tests/test_controller.py | 34 ++++++++++++
2 files changed, 81 insertions(+), 8 deletions(-)
diff --git a/src/_zkapauthorizer/controller.py b/src/_zkapauthorizer/controller.py
index 56dae0b..b1c4d4b 100644
--- a/src/_zkapauthorizer/controller.py
+++ b/src/_zkapauthorizer/controller.py
@@ -39,6 +39,7 @@ from twisted.python.url import (
from twisted.internet.defer import (
Deferred,
succeed,
+ fail,
inlineCallbacks,
returnValue,
)
@@ -62,6 +63,13 @@ from .model import (
)
+class AlreadySpent(Exception):
+ """
+ An attempt was made to redeem a voucher which has already been redeemed.
+ The redemption cannot succeed and should not be retried automatically.
+ """
+
+
class IRedeemer(Interface):
"""
An ``IRedeemer`` can exchange a voucher for one or more passes.
@@ -100,7 +108,10 @@ class IRedeemer(Interface):
:return: A ``Deferred`` which fires with a list of ``UnblindedToken``
instances on successful redemption or which fails with any error
- to allow a retry to be made at some future point.
+ to allow a retry to be made at some future point. It may also
+ fail with an ``AlreadySpent`` error to indicate the redemption
+ server considers the voucher to have been redeemed already and
+ will not allow it to be redeemed.
"""
def tokens_to_passes(message, unblinded_tokens):
@@ -150,6 +161,28 @@ class NonRedeemer(object):
)
+@implementer(IRedeemer)
+@attr.s
+class DoubleSpentRedeemer(object):
+ """
+ A ``DoubleSpentRedeemer`` pretends to try to redeem vouchers for ZKAPs but
+ always fails with an error indicating the voucher has already been spent.
+ """
+ def random_tokens_for_voucher(self, voucher, count):
+ return dummy_random_tokens(voucher, count)
+
+ def redeem(self, voucher, random_tokens):
+ return fail(AlreadySpent(voucher))
+
+
+def dummy_random_tokens(voucher, count):
+ return list(
+ RandomToken(u"{}-{}".format(voucher.number, n))
+ for n
+ in range(count)
+ )
+
+
@implementer(IRedeemer)
@attr.s
class DummyRedeemer(object):
@@ -167,12 +200,7 @@ class DummyRedeemer(object):
Generate some number of random tokens to submit along with a voucher for
redemption.
"""
- # Dummy token generation.
- return list(
- RandomToken(u"{}-{}".format(voucher.number, n))
- for n
- in range(count)
- )
+ return dummy_random_tokens(voucher, count)
def redeem(self, voucher, random_tokens):
"""
@@ -431,7 +459,18 @@ class PaymentController(object):
self.store.insert_unblinded_tokens_for_voucher(voucher, unblinded_tokens)
def _redeemFailure(self, voucher, reason):
- self._log.failure("Redeeming random tokens for a voucher ({voucher}) failed.", reason, voucher=voucher)
+ if reason.check(AlreadySpent):
+ self._log.error(
+ "Voucher {voucher} reported as already spent during redemption.",
+ voucher=voucher,
+ )
+ self.store.mark_voucher_double_spent(voucher)
+ else:
+ self._log.failure(
+ "Redeeming random tokens for a voucher ({voucher}) failed.",
+ reason,
+ voucher=voucher,
+ )
return None
def _finalRedeemError(self, voucher, reason):
diff --git a/src/_zkapauthorizer/tests/test_controller.py b/src/_zkapauthorizer/tests/test_controller.py
index bb72c66..17876ca 100644
--- a/src/_zkapauthorizer/tests/test_controller.py
+++ b/src/_zkapauthorizer/tests/test_controller.py
@@ -43,6 +43,7 @@ from testtools.matchers import (
IsInstance,
HasLength,
AfterPreprocessing,
+ MatchesStructure,
)
from testtools.twistedsupport import (
succeeded,
@@ -94,6 +95,7 @@ from ..controller import (
IRedeemer,
NonRedeemer,
DummyRedeemer,
+ DoubleSpentRedeemer,
RistrettoRedeemer,
PaymentController,
)
@@ -146,6 +148,9 @@ class PaymentControllerTests(TestCase):
@given(tahoe_configs(), datetimes(), vouchers())
def test_redeemed_after_redeeming(self, get_config, now, voucher):
+ """
+ A ``Voucher`` is marked as redeemed after ``IRedeemer.redeem`` succeeds.
+ """
tempdir = self.useFixture(TempDir())
store = VoucherStore.from_node_config(
get_config(
@@ -167,6 +172,35 @@ class PaymentControllerTests(TestCase):
Equals(u"redeemed"),
)
+ @given(tahoe_configs(), datetimes(), vouchers())
+ def test_double_spent_after_double_spend(self, get_config, now, voucher):
+ """
+ A ``Voucher`` is marked as double-spent after ``IRedeemer.redeem`` fails
+ with ``AlreadySpent``.
+ """
+ tempdir = self.useFixture(TempDir())
+ store = VoucherStore.from_node_config(
+ get_config(
+ tempdir.join(b"node"),
+ b"tub.port",
+ ),
+ now=lambda: now,
+ connect=memory_connect,
+ )
+ controller = PaymentController(
+ store,
+ DoubleSpentRedeemer(),
+ )
+ controller.redeem(voucher)
+
+ persisted_voucher = store.get(voucher)
+ self.assertThat(
+ persisted_voucher,
+ MatchesStructure(
+ state=Equals(u"double-spend"),
+ ),
+ )
+
NOWHERE = URL.from_text(u"https://127.0.0.1/")
--
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