From 1e6a25b6da1c816c2ad4ca43e5f1b8be8259162f Mon Sep 17 00:00:00 2001
From: Vibhav Simha G <vibhavgopalkrishna145@bitgo.com>
Date: Wed, 3 Jun 2026 16:44:16 +0530
Subject: [PATCH] fix(sdk-core): pass round to getBitgoSignatureShare helper
 Ticket: WCI-626 EdDSA MPCv2 signing can receive multiple BitGo-to-signer
 shares in a txRequest. Selecting only by sender/recipient can pick a stale
 round-1 output during round 2. - Add shareType param to
 getBitgoSignatureShare to filter by round output type. - Update EdDSA MPCv2
 callers to request round-1 or round-2 output explicitly. - Remove inline
 reverse().find() in offline round-3 path in favour of the helper. - Update
 tests to expect round-specific missing share error messages.

---
 modules/sdk-core/src/bitgo/tss/common.ts      | 10 +++++++---
 .../src/bitgo/utils/tss/eddsa/eddsaMPCv2.ts   | 19 ++++---------------
 .../unit/bitgo/utils/tss/eddsa/eddsaMPCv2.ts  |  4 ++--
 3 files changed, 13 insertions(+), 20 deletions(-)

diff --git a/modules/sdk-core/src/bitgo/tss/common.ts b/modules/sdk-core/src/bitgo/tss/common.ts
index 156729d78d..3eaddbaa58 100644
--- a/modules/sdk-core/src/bitgo/tss/common.ts
+++ b/modules/sdk-core/src/bitgo/tss/common.ts
@@ -20,12 +20,16 @@ const debug = require('debug')('bitgo:tss:common');
 
 export function getBitgoSignatureShare(
   signatureShares: SignatureShareRecord[],
-  signerShareType: SignatureShareType
+  signerShareType: SignatureShareType,
+  shareType: 'round1Output' | 'round2Output' | 'round3Output'
 ): SignatureShareRecord {
   const bitgoShare = signatureShares.find(
-    (share) => share.from === SignatureShareType.BITGO && share.to === signerShareType
+    (share) =>
+      share.from === SignatureShareType.BITGO &&
+      share.to === signerShareType &&
+      JSON.parse(share.share).type === shareType
   );
-  assert(bitgoShare, 'Missing BitGo signature share');
+  assert(bitgoShare, `Missing BitGo ${shareType} signature share`);
   return bitgoShare;
 }
 
diff --git a/modules/sdk-core/src/bitgo/utils/tss/eddsa/eddsaMPCv2.ts b/modules/sdk-core/src/bitgo/utils/tss/eddsa/eddsaMPCv2.ts
index 8dc3175f48..f11b0f94a5 100644
--- a/modules/sdk-core/src/bitgo/utils/tss/eddsa/eddsaMPCv2.ts
+++ b/modules/sdk-core/src/bitgo/utils/tss/eddsa/eddsaMPCv2.ts
@@ -469,7 +469,7 @@ export class EddsaMPCv2Utils extends BaseEddsaUtils {
         ? latestTxRequest.transactions![0].signatureShares
         : latestTxRequest.messages![0].signatureShares;
 
-    const bitgoShareRoundOne = getBitgoSignatureShare(signatureShares1, signerShareType);
+    const bitgoShareRoundOne = getBitgoSignatureShare(signatureShares1, signerShareType, 'round1Output');
     const parsedBitGoToUserSigShareRoundOne = decodeWithCodec(
       EddsaMPCv2SignatureShareRound1Output,
       JSON.parse(bitgoShareRoundOne.share),
@@ -508,7 +508,7 @@ export class EddsaMPCv2Utils extends BaseEddsaUtils {
         ? latestTxRequest.transactions![0].signatureShares
         : latestTxRequest.messages![0].signatureShares;
 
-    const bitgoShareRoundTwo = getBitgoSignatureShare(txRequestSignatureShares, signerShareType);
+    const bitgoShareRoundTwo = getBitgoSignatureShare(txRequestSignatureShares, signerShareType, 'round2Output');
     const parsedBitGoToUserSigShareRoundTwo = decodeWithCodec(
       EddsaMPCv2SignatureShareRound2Output,
       JSON.parse(bitgoShareRoundTwo.share),
@@ -649,7 +649,7 @@ export class EddsaMPCv2Utils extends BaseEddsaUtils {
     const signatureShares = transactions[0].signatureShares;
     assert(signatureShares, 'Missing signature shares in round 1 txRequest');
 
-    const bitgoShareRoundOne = getBitgoSignatureShare(signatureShares, SignatureShareType.USER);
+    const bitgoShareRoundOne = getBitgoSignatureShare(signatureShares, SignatureShareType.USER, 'round1Output');
     const parsedBitGoToUserSigShareRoundOne = decodeWithCodec(
       EddsaMPCv2SignatureShareRound1Output,
       JSON.parse(bitgoShareRoundOne.share),
@@ -754,18 +754,7 @@ export class EddsaMPCv2Utils extends BaseEddsaUtils {
     const signatureShares = transactions[0].signatureShares;
     assert(signatureShares, 'Missing signature shares in round 2 txRequest');
 
-    const bitgoShareRoundTwo = [...signatureShares].reverse().find((share) => {
-      if (share.from !== SignatureShareType.BITGO || share.to !== SignatureShareType.USER) {
-        return false;
-      }
-
-      try {
-        return JSON.parse(share.share).type === 'round2Output';
-      } catch {
-        return false;
-      }
-    });
-    assert(bitgoShareRoundTwo, 'Missing BitGo round 2 signature share');
+    const bitgoShareRoundTwo = getBitgoSignatureShare(signatureShares, SignatureShareType.USER, 'round2Output');
 
     const parsedBitGoToUserSigShareRoundTwo = decodeWithCodec(
       EddsaMPCv2SignatureShareRound2Output,
diff --git a/modules/sdk-core/test/unit/bitgo/utils/tss/eddsa/eddsaMPCv2.ts b/modules/sdk-core/test/unit/bitgo/utils/tss/eddsa/eddsaMPCv2.ts
index 77784805b8..ed24af96e3 100644
--- a/modules/sdk-core/test/unit/bitgo/utils/tss/eddsa/eddsaMPCv2.ts
+++ b/modules/sdk-core/test/unit/bitgo/utils/tss/eddsa/eddsaMPCv2.ts
@@ -799,7 +799,7 @@ describe('EddsaMPCv2Utils.createOfflineRound2Share', () => {
           encryptedUserGpgPrvKey: round1.encryptedUserGpgPrvKey,
           encryptedRound1Session: round1.encryptedRound1Session,
         }),
-      /Missing BitGo signature share/
+      /Missing BitGo round1Output signature share/
     );
   });
 
@@ -1114,7 +1114,7 @@ describe('EddsaMPCv2Utils.createOfflineRound3Share', () => {
           encryptedUserGpgPrvKey: round1.encryptedUserGpgPrvKey,
           encryptedRound2Session: round2.encryptedRound2Session,
         }),
-      /Missing BitGo round 2 signature share/
+      /Missing BitGo round2Output signature share/
     );
   });