taler-typescript-core

commit 65a9d6018681316fc58347b50fae3f6fd2629884
parent 19c41e767739a409083e93cd9a17ed6cce57f8e6
Author: Florian Dold <dold@taler.net>
Date:   Wed, 22 Jul 2026 19:24:20 +0200

wallet: derive the donation unit key hash instead of reading it

This fixes test failures due to a breaking protocol change in donau.

Diffstat:
M
packages/taler-util/src/types-donau.ts
 | 
39
++++++++++++++++++++++++++++++++++++---
M
packages/taler-wallet-core/src/donau.ts
 | 
5
+++--

2 files changed, 39 insertions(+), 5 deletions(-)
diff --git a/packages/taler-util/src/types-donau.ts b/packages/taler-util/src/types-donau.ts
@@ -46,6 +46,8 @@ import {
   AmountString,
 } from "./types-taler-common.js";
 import { DenomKeyType } from "./types-taler-exchange.js";
+import { assertUnreachable } from "./errors.js";
+import { decodeCrock, encodeCrock, hash } from "./taler-crypto.js";
 
 export interface DonauVersionResponse {
   // libtool-style representation of the Donau protocol version, see
@@ -137,10 +139,27 @@ export interface DonationUnitKeyGroupCommon {
   lost?: boolean;
 }
 
+/**
+ * Public key of a donation unit, as it appears in the donau's key response.
+ *
+ * The hash of the key is not part of this: the donau does not send it
+ * (`DONAU_JSON_pack_donation_unit_pub` packs the cipher and the key only) and
+ * derives it locally when parsing, so clients do the same.  See
+ * {@link hashDonationUnitPub}.
+ */
+export type DonationUnitPub =
+  | {
+      cipher: "RSA";
+      rsa_public_key: RsaPublicKeyString;
+    }
+  | {
+      cipher: "CS";
+      cs_public_key: Cs25519Point;
+    };
+
 export interface DonationUnitKeyGroupRsa extends DonationUnitKeyGroupCommon {
   donation_unit_pub: {
     cipher: "RSA";
-    pub_key_hash: HashCodeString;
     rsa_public_key: RsaPublicKeyString;
   };
 }
@@ -148,11 +167,25 @@ export interface DonationUnitKeyGroupRsa extends DonationUnitKeyGroupCommon {
 export interface DonationUnitKeyGroupCs extends DonationUnitKeyGroupCommon {
   donation_unit_pub: {
     cipher: "CS";
-    pub_key_hash: HashCodeString;
-    cs_pub: Cs25519Point;
+    cs_public_key: Cs25519Point;
   };
 }
 
+/**
+ * Hash of a donation unit public key, as the donau computes it: the hash of
+ * the encoded key, which is what the wire format carries.
+ */
+export function hashDonationUnitPub(pub: DonationUnitPub): HashCodeString {
+  switch (pub.cipher) {
+    case "RSA":
+      return encodeCrock(hash(decodeCrock(pub.rsa_public_key)));
+    case "CS":
+      return encodeCrock(hash(decodeCrock(pub.cs_public_key)));
+    default:
+      assertUnreachable(pub);
+  }
+}
+
 // FIXME: Validate properly!
 export const codecForDonationUnitKeyGroup: Codec<DonationUnitKeyGroup> =
   codecForAny();
diff --git a/packages/taler-wallet-core/src/donau.ts b/packages/taler-wallet-core/src/donau.ts
@@ -36,6 +36,7 @@ import {
   DonationUnitKeyGroupRsa,
   DonauHttpClient,
   DonauKeysResponse,
+  hashDonationUnitPub,
   DonauStatementItem,
   DonauUnitPubKey,
   EmptyObject,
@@ -357,7 +358,7 @@ async function getCandidateDonationUnits(
       continue;
     }
     candidates.push({
-      unitHash: g.donation_unit_pub.pub_key_hash,
+      unitHash: hashDonationUnitPub(g.donation_unit_pub),
       unitKey: {
         cipher: DenomKeyType.Rsa,
         age_mask: 0,
@@ -572,7 +573,7 @@ export async function acceptDonauBlindSigs(
       const candidate = keysResp.donation_units[j];
       if (
         candidate.donation_unit_pub.cipher === "RSA" &&
-        candidate.donation_unit_pub.pub_key_hash ===
+        hashDonationUnitPub(candidate.donation_unit_pub) ===
           myPlanchet.donationUnitPubHash
       ) {
         unitKey = candidate as DonationUnitKeyGroupRsa;