From 7b54439fd62bd2a5e15b3068a8fbaffeb0a57468 Mon Sep 17 00:00:00 2001
From: Florian Dold <florian.dold@gmail.com>
Date: Thu, 5 Dec 2019 23:07:46 +0100
Subject: validate wire fees and acct info

---
 src/crypto/workers/cryptoApi.ts            |  4 +++
 src/crypto/workers/cryptoImplementation.ts | 26 +++++++++++++++++---
 src/wallet-impl/exchanges.ts               | 39 +++++++++++++++++++++++++-----
 3 files changed, 59 insertions(+), 10 deletions(-)

(limited to 'src')

diff --git a/src/crypto/workers/cryptoApi.ts b/src/crypto/workers/cryptoApi.ts
index 5537bb39f..aa1ff2c42 100644
--- a/src/crypto/workers/cryptoApi.ts
+++ b/src/crypto/workers/cryptoApi.ts
@@ -409,6 +409,10 @@ export class CryptoApi {
     return this.doRpc<boolean>("rsaVerify", 4, hm, sig, pk);
   }
 
+  isValidWireAccount(paytoUri: string, sig: string, masterPub: string): Promise<boolean> {
+    return this.doRpc<boolean>("isValidWireAccount", 4, paytoUri, sig, masterPub);
+  }
+
   createPaybackRequest(coin: CoinRecord): Promise<PaybackRequest> {
     return this.doRpc<PaybackRequest>("createPaybackRequest", 1, coin);
   }
diff --git a/src/crypto/workers/cryptoImplementation.ts b/src/crypto/workers/cryptoImplementation.ts
index 00d81ce27..fa5a30d68 100644
--- a/src/crypto/workers/cryptoImplementation.ts
+++ b/src/crypto/workers/cryptoImplementation.ts
@@ -68,15 +68,17 @@ import {
   rsaVerify,
 } from "../talerCrypto";
 import { randomBytes } from "../primitives/nacl-fast";
+import { kdf } from "../primitives/kdf";
 
 enum SignaturePurpose {
   RESERVE_WITHDRAW = 1200,
   WALLET_COIN_DEPOSIT = 1201,
   MASTER_DENOMINATION_KEY_VALIDITY = 1025,
+  MASTER_WIRE_FEES = 1028,
+  MASTER_WIRE_DETAILS = 1030,
   WALLET_COIN_MELT = 1202,
   TEST = 4242,
   MERCHANT_PAYMENT_OK = 1104,
-  MASTER_WIRE_FEES = 1028,
   WALLET_COIN_PAYBACK = 1203,
   WALLET_COIN_LINK = 1204,
 }
@@ -157,9 +159,7 @@ export class CryptoImplementation {
    * Create a pre-coin of the given denomination to be withdrawn from then given
    * reserve.
    */
-  createPlanchet(
-    req: PlanchetCreationRequest,
-  ): PlanchetCreationResult {
+  createPlanchet(req: PlanchetCreationRequest): PlanchetCreationResult {
     const reservePub = decodeCrock(req.reservePub);
     const reservePriv = decodeCrock(req.reservePriv);
     const denomPub = decodeCrock(req.denomPub);
@@ -264,6 +264,7 @@ export class CryptoImplementation {
       .put(timestampToBuffer(wf.startStamp))
       .put(timestampToBuffer(wf.endStamp))
       .put(amountToBuffer(wf.wireFee))
+      .put(amountToBuffer(wf.closingFee))
       .build();
     const sig = decodeCrock(wf.sig);
     const pub = decodeCrock(masterPub);
@@ -292,6 +293,23 @@ export class CryptoImplementation {
     return eddsaVerify(p, sig, pub);
   }
 
+  isValidWireAccount(
+    paytoUri: string,
+    sig: string,
+    masterPub: string,
+  ): boolean {
+    const h = kdf(
+      64,
+      stringToBytes("exchange-wire-signature"),
+      stringToBytes(paytoUri + "\0"),
+      new Uint8Array(0),
+    );
+    const p = buildSigPS(SignaturePurpose.MASTER_WIRE_DETAILS)
+      .put(h)
+      .build();
+    return eddsaVerify(p, decodeCrock(sig), decodeCrock(masterPub));
+  }
+
   /**
    * Create a new EdDSA key pair.
    */
diff --git a/src/wallet-impl/exchanges.ts b/src/wallet-impl/exchanges.ts
index b89f3f84e..b6a2f1c8a 100644
--- a/src/wallet-impl/exchanges.ts
+++ b/src/wallet-impl/exchanges.ts
@@ -15,10 +15,13 @@
  */
 
 import { InternalWalletState } from "./state";
+import { WALLET_CACHE_BREAKER_CLIENT_VERSION } from "../wallet";
 import {
-  WALLET_CACHE_BREAKER_CLIENT_VERSION,
-} from "../wallet";
-import { KeysJson, Denomination, ExchangeWireJson } from "../talerTypes";
+  KeysJson,
+  Denomination,
+  ExchangeWireJson,
+  WireFeesJson,
+} from "../talerTypes";
 import { getTimestampNow, OperationError } from "../walletTypes";
 import {
   ExchangeRecord,
@@ -229,8 +232,12 @@ async function updateExchangeWithWireInfo(
   if (exchange.updateStatus != ExchangeUpdateStatus.FETCH_WIRE) {
     return;
   }
+  const details = exchange.details;
+  if (!details) {
+    throw Error("invalid exchange state");
+  }
   const reqUrl = new URL("wire", exchangeBaseUrl);
-  reqUrl.searchParams.set("cacheBreaker", WALLET_CACHE_BREAKER_CLIENT_VERSION)
+  reqUrl.searchParams.set("cacheBreaker", WALLET_CACHE_BREAKER_CLIENT_VERSION);
 
   const resp = await ws.http.get(reqUrl.href);
 
@@ -239,6 +246,17 @@ async function updateExchangeWithWireInfo(
     throw Error("/wire response malformed");
   }
   const wireInfo = ExchangeWireJson.checked(wiJson);
+  for (const a of wireInfo.accounts) {
+    console.log("validating exchange acct");
+    const isValid = await ws.cryptoApi.isValidWireAccount(
+      a.url,
+      a.master_sig,
+      details.masterPublicKey,
+    );
+    if (!isValid) {
+      throw Error("exchange acct signature invalid");
+    }
+  }
   const feesForType: { [wireMethod: string]: WireFee[] } = {};
   for (const wireMethod of Object.keys(wireInfo.fees)) {
     const feeList: WireFee[] = [];
@@ -251,13 +269,22 @@ async function updateExchangeWithWireInfo(
       if (!endStamp) {
         throw Error("wrong date format");
       }
-      feeList.push({
+      const fee: WireFee = {
         closingFee: Amounts.parseOrThrow(x.closing_fee),
         endStamp,
         sig: x.sig,
         startStamp,
         wireFee: Amounts.parseOrThrow(x.wire_fee),
-      });
+      };
+      const isValid = await ws.cryptoApi.isValidWireFee(
+        wireMethod,
+        fee,
+        details.masterPublicKey,
+      );
+      if (!isValid) {
+        throw Error("exchange wire fee signature invalid");
+      }
+      feeList.push(fee);
     }
     feesForType[wireMethod] = feeList;
   }
-- 
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