From f2661507b3fd558fda68e4737161352a1e468cea Mon Sep 17 00:00:00 2001
From: Jean-Paul Calderone <exarkun@twistedmatrix.com>
Date: Wed, 15 Apr 2020 11:26:13 -0400
Subject: [PATCH] Put bounds checking on redeemCounter
---
src/PaymentServer/Redemption.hs | 47 ++++++++++++++++++++++-----------
1 file changed, 32 insertions(+), 15 deletions(-)
diff --git a/src/PaymentServer/Redemption.hs b/src/PaymentServer/Redemption.hs
index fa5a8e1..33d488f 100644
--- a/src/PaymentServer/Redemption.hs
+++ b/src/PaymentServer/Redemption.hs
@@ -73,6 +73,8 @@ data Result
= Unpaid -- ^ A voucher has not been paid for.
| DoubleSpend -- ^ A voucher has already been redeemed.
| OtherFailure Text -- ^ Some other unrecognized failure mode.
+ -- | Given counter was not in the expected range
+ | CounterOutOfBounds Integer Integer Integer
| Succeeded PublicKey [Signature] Proof
deriving (Show, Eq)
@@ -104,6 +106,13 @@ instance ToJSON Result where
[ "success" .= False
, "reason" .= ("double-spend" :: Text)
]
+ toJSON (CounterOutOfBounds min max received) = object
+ [ "success" .= False
+ , "reason" .= ("counter-out-of-bounds" :: Text)
+ , "min" .= min
+ , "max" .= max
+ , "received" .= received
+ ]
toJSON (OtherFailure description) = object
[ "success" .= False
, "reason" .= description
@@ -131,6 +140,11 @@ instance FromJSON Result where
then return DoubleSpend
else return $ OtherFailure reason
+-- | Limit the value for the counter value supplied during a voucher
+-- redemption attempt. A counter in the range [0..maxCounter) is allowed.
+maxCounter :: Integer
+maxCounter = 16
+
type RedemptionAPI = ReqBody '[JSON] Redeem :> Post '[JSON] Result
jsonErr400 reason = err400
@@ -145,21 +159,24 @@ redemptionServer = redeem
-- voucher and return signatures. Return a failure if this is not possible
-- (eg because the voucher was already redeemed).
redeem :: VoucherDatabase d => Issuer -> d -> Redeem -> Handler Result
-redeem issue database (Redeem voucher tokens) = do
- let fingerprint = fingerprintFromTokens tokens
- result <- liftIO $ PaymentServer.Persistence.redeemVoucher database voucher fingerprint
- case result of
- Left NotPaid -> do
- throwError $ jsonErr400 Unpaid
- Left AlreadyRedeemed -> do
- throwError $ jsonErr400 DoubleSpend
- Right () -> do
- let result = issue tokens
- case result of
- Left reason -> do
- throwError $ jsonErr400 $ OtherFailure reason
- Right (ChallengeBypass key signatures proof) ->
- return $ Succeeded key signatures proof
+redeem issue database (Redeem voucher tokens counter) =
+ if counter < 0 || counter >= maxCounter then
+ throwError $ jsonErr400 (CounterOutOfBounds 0 maxCounter counter)
+ else do
+ let fingerprint = fingerprintFromTokens tokens
+ result <- liftIO $ PaymentServer.Persistence.redeemVoucher database voucher fingerprint
+ case result of
+ Left NotPaid -> do
+ throwError $ jsonErr400 Unpaid
+ Left AlreadyRedeemed -> do
+ throwError $ jsonErr400 DoubleSpend
+ Right () -> do
+ let result = issue tokens
+ case result of
+ Left reason -> do
+ throwError $ jsonErr400 $ OtherFailure reason
+ Right (ChallengeBypass key signatures proof) ->
+ return $ Succeeded key signatures proof
-- | Compute a cryptographic hash (fingerprint) of a list of tokens which can
-- be used as an identifier for this exact sequence of tokens.
--
GitLab