feat(express): implement EdDSA commitments for external signer

implemented EdDSA commitment step for external signer added unit test

WP-94

modules/express/src/clientRoutes.ts

@@ -409,13 +409,17 @@ export async function handleV2GenerateShareTSS(req: express.Request): Promise<an
   const coin = bitgo.coin(req.params.coin);
   const eddUtils = new EddsaUtils(bitgo, coin);
   req.body.prv = privKey;
+  req.body.walletPassphrase = walletPw;
   try {
-    if (req.params.sharetype == 'R') {
-      return await eddUtils.createRShareFromTxRequest(req.body);
-    } else if (req.params.sharetype == 'G') {
-      return await eddUtils.createGShareFromTxRequest(req.body);
-    } else {
-      throw new Error('Share type not supported, only G and R share generation is supported.');
+    switch (req.params.sharetype) {
+      case 'commitment':
+        return await eddUtils.createCommitmentShareFromTxRequest(req.body);
+      case 'R':
+        return await eddUtils.createRShareFromTxRequest(req.body);
+      case 'G':
+        return await eddUtils.createGShareFromTxRequest(req.body);
+      default:
+        throw new Error('Share type not supported, only commitment, G and R share generation is supported.');
     }
   } catch (error) {
     console.error('error while signing wallet transaction ', error);

modules/express/test/unit/clientRoutes/externalSign.ts

@@ -47,6 +47,16 @@ describe('External signer', () => {
     bgUrl = common.Environments[bitgo.getEnv()].uri;
     hdTree = await Ed25519BIP32.initialize();
     MPC = await Eddsa.initialize(hdTree);
+
+    const bitgoPublicKey =
+      '-----BEGIN PGP PUBLIC KEY BLOCK-----\n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\n6eOi3w==\n=XFoJ\n-----END PGP PUBLIC KEY BLOCK-----\n';
+    const constants = {
+      mpc: {
+        bitgoPublicKey,
+      },
+    };
+
+    nock(bgUrl).persist().get('/api/v1/client/constants').reply(200, { ttl: 3600, constants });
   });
 
   after(() => {
@@ -194,7 +204,7 @@ describe('External signer', () => {
     envStub.restore();
   });
 
-  it('should read an encrypted prv from signerFileSystemPath and pass it to R and G share generators, with commitment', async () => {
+  it('should read an encrypted prv from signerFileSystemPath and pass it to commitment, R and G share generators', async () => {
     const walletID = '62fe536a6b4cf70007acb48c0e7bb0b0';
     const user = MPC.keyShare(1, 2, 3);
     const backup = MPC.keyShare(2, 2, 3);
@@ -215,12 +225,41 @@ describe('External signer', () => {
       .value({ WALLET_62fe536a6b4cf70007acb48c0e7bb0b0_PASSPHRASE: walletPassphrase });
     const tMessage = 'testMessage';
     const bgTest = new BitGo({ env: 'test' });
+
+    const reqCommitment = {
+      bitgo: bgTest,
+      body: {
+        txRequest: {
+          apiVersion: 'full',
+          walletId: walletID,
+          transactions: [
+            {
+              unsignedTx: {
+                derivationPath: 'm/0',
+                signableHex: tMessage,
+              },
+            },
+          ],
+        },
+      },
+      params: {
+        coin: 'tsol',
+        sharetype: 'commitment',
+      },
+      config: {
+        signerFileSystemPath: 'signerFileSystemPath',
+      },
+    } as unknown as express.Request;
+    const cResult = await handleV2GenerateShareTSS(reqCommitment);
+    cResult.should.have.property('userToBitgoCommitment');
+    cResult.should.have.property('encryptedSignerShare');
+    cResult.should.have.property('encryptedUserToBitgoRShare');
+    const encryptedUserToBitgoRShare = cResult.encryptedUserToBitgoRShare;
     const reqR = {
       bitgo: bgTest,
       body: {
         txRequest: {
           apiVersion: 'full',
-          state: 'pendingCommitment',
           walletId: walletID,
           transactions: [
             {
@@ -231,6 +270,7 @@ describe('External signer', () => {
             },
           ],
         },
+        encryptedUserToBitgoRShare,
       },
       params: {
         coin: 'tsol',
@@ -240,8 +280,10 @@ describe('External signer', () => {
         signerFileSystemPath: 'signerFileSystemPath',
       },
     } as unknown as express.Request;
-    const result = await handleV2GenerateShareTSS(reqR);
-    const bitgoCombine = MPC.keyCombine(bitgo.uShare, [result.signingKeyYShare, backup.yShares[3]]);
+    const rResult = await handleV2GenerateShareTSS(reqR);
+    rResult.should.have.property('rShare');
+    rResult.should.have.property('signingKeyYShare');
+    const bitgoCombine = MPC.keyCombine(bitgo.uShare, [rResult.signingKeyYShare, backup.yShares[3]]);
     const bitgoSignShare = await MPC.signShare(Buffer.from(tMessage, 'hex'), bitgoCombine.pShare, [
       bitgoCombine.jShares[1],
     ]);
@@ -271,7 +313,7 @@ describe('External signer', () => {
             },
           ],
         },
-        userToBitgoRShare: result.rShare,
+        userToBitgoRShare: rResult.rShare,
         bitgoToUserRShare: signatureShareRec,
         bitgoToUserCommitment: bitgoToUserCommitmentShare,
       },
@@ -284,14 +326,18 @@ describe('External signer', () => {
       },
     } as unknown as express.Request;
     const userGShare = await handleV2GenerateShareTSS(reqG);
+    userGShare.should.have.property('i');
+    userGShare.should.have.property('y');
+    userGShare.should.have.property('gamma');
+    userGShare.should.have.property('R');
     const userToBitgoRShare = {
       i: ShareKeyPosition.BITGO,
       j: ShareKeyPosition.USER,
-      u: result.signingKeyYShare.u,
-      v: result.rShare.rShares[3].v,
-      r: result.rShare.rShares[3].r,
-      R: result.rShare.rShares[3].R,
-      commitment: result.rShare.rShares[3].commitment,
+      u: rResult.signingKeyYShare.u,
+      v: rResult.rShare.rShares[3].v,
+      r: rResult.rShare.rShares[3].r,
+      R: rResult.rShare.rShares[3].R,
+      commitment: rResult.rShare.rShares[3].commitment,
     };
     const bitgoGShare = MPC.sign(
       Buffer.from(tMessage, 'hex'),

modules/sdk-core/src/bitgo/utils/tss/baseTSSUtils.ts

@@ -25,6 +25,7 @@ import {
   PopulatedIntentForTypedDataSigning,
   CreateBitGoKeychainParamsBase,
   CommitmentShareRecord,
+  EncryptedSignerShareRecord,
 } from './baseTypes';
 import { GShare, SignShare, YShare } from '../../../account-lib/mpc/tss';
 
@@ -123,6 +124,22 @@ export default class BaseTssUtils<KeyShare> extends MpcUtils implements ITssUtil
     throw new Error('Method not implemented.');
   }
 
+  /**
+   * Create an Commitment (User to BitGo) share from an unsigned transaction and private user signing material
+   * EDDSA only
+   *
+   * @param {TxRequest} txRequest - transaction request with unsigned transaction
+   * @param {string} prv - user signing material
+   * @returns {Promise<{ userToBitgoCommitment: CommitmentShareRecor, encryptedSignerShare: EncryptedSignerShareRecord }>} - Commitment Share and the Encrypted Signer Share to BitGo
+   */
+  createCommitmentShareFromTxRequest(params: { txRequest: TxRequest; prv: string; walletPassphrase: string }): Promise<{
+    userToBitgoCommitment: CommitmentShareRecord;
+    encryptedSignerShare: EncryptedSignerShareRecord;
+    encryptedUserToBitgoRShare: EncryptedSignerShareRecord;
+  }> {
+    throw new Error('Method not implemented.');
+  }
+
   /**
    * Create an R (User to BitGo) share from an unsigned transaction and private user signing material
    *
@@ -133,6 +150,8 @@ export default class BaseTssUtils<KeyShare> extends MpcUtils implements ITssUtil
   createRShareFromTxRequest(params: {
     txRequest: TxRequest;
     prv: string;
+    walletPassphrase?: string;
+    encryptedUserToBitgoRShare?: EncryptedSignerShareRecord;
   }): Promise<{ rShare: SignShare; signingKeyYShare: YShare }> {
     throw new Error('Method not implemented.');
   }
@@ -144,7 +163,7 @@ export default class BaseTssUtils<KeyShare> extends MpcUtils implements ITssUtil
    * @param {string} prv - user signing material
    * @param {SignatureShareRecord} bitgoToUserRShare - BitGo to User R Share
    * @param {SignShare} userToBitgoRShare - User to BitGo R Share
-   * @param {string} [bitgoToUserCommitment] - BitGo to User Commitment
+   * @param {CommitmentShareRecord} [bitgoToUserCommitment] - BitGo to User Commitment
    * @returns {Promise<GShare>} - GShare from User to BitGo
    */
   createGShareFromTxRequest(params: {

modules/sdk-core/src/bitgo/utils/tss/baseTypes.ts

@@ -270,6 +270,7 @@ export interface ExchangeCommitmentResponse {
 
 export enum EncryptedSignerShareType {
   ENCRYPTED_SIGNER_SHARE = 'encryptedSignerShare',
+  ENCRYPTED_R_SHARE = 'encryptedRShare',
 }
 export interface EncryptedSignerShareRecord extends ShareBaseRecord {
   type: EncryptedSignerShareType;
@@ -341,9 +342,16 @@ export interface ITssUtils<KeyShare = EDDSA.KeyShare> {
     externalSignerRShareGenerator: CustomRShareGeneratingFunction,
     externalSignerGShareGenerator: CustomGShareGeneratingFunction
   ): Promise<TxRequest>;
+  createCommitmentShareFromTxRequest(params: { txRequest: TxRequest; prv: string; walletPassphrase: string }): Promise<{
+    userToBitgoCommitment: CommitmentShareRecord;
+    encryptedSignerShare: EncryptedSignerShareRecord;
+    encryptedUserToBitgoRShare: EncryptedSignerShareRecord;
+  }>;
   createRShareFromTxRequest(params: {
     txRequest: TxRequest;
     prv: string;
+    walletPassphrase?: string;
+    encryptedUserToBitgoRShare?: EncryptedSignerShareRecord;
   }): Promise<{ rShare: SignShare; signingKeyYShare: YShare }>;
   createGShareFromTxRequest(params: {
     txRequest: TxRequest;

modules/sdk-core/src/bitgo/utils/tss/eddsa/eddsa.ts

@@ -364,10 +364,16 @@ export class EddsaUtils extends baseTSSUtils<KeyShare> {
     return keychains;
   }
 
-  async createRShareFromTxRequest(params: {
+  async createCommitmentShareFromTxRequest(params: {
     txRequest: TxRequest;
     prv: string;
-  }): Promise<{ rShare: SignShare; signingKeyYShare: YShare }> {
+    walletPassphrase: string;
+  }): Promise<{
+    userToBitgoCommitment: CommitmentShareRecord;
+    encryptedSignerShare: EncryptedSignerShareRecord;
+    encryptedUserToBitgoRShare: EncryptedSignerShareRecord;
+  }> {
+    const bitgoIndex = 3;
     const { txRequest, prv } = params;
     const txRequestResolved: TxRequest = txRequest;
 
@@ -394,8 +400,67 @@ export class EddsaUtils extends baseTSSUtils<KeyShare> {
     const signablePayload = Buffer.from(unsignedTx.signableHex, 'hex');
 
     const userSignShare = await createUserSignShare(signablePayload, signingKey.pShare);
+    const commitment = userSignShare.rShares[bitgoIndex]?.commitment;
+    assert(commitment, 'Unable to find commitment in userSignShare');
+    const userToBitgoCommitment = this.createUserToBitgoCommitmentShare(commitment);
+
+    const signerShare = signingKey.yShares[bitgoIndex].u + signingKey.yShares[bitgoIndex].chaincode;
+    const bitgoGpgKey = await getBitgoGpgPubKey(this.bitgo);
+    const bitgoToUserEncryptedSignerShare = await encryptText(signerShare, bitgoGpgKey);
+
+    const encryptedSignerShare = this.createUserToBitgoEncryptedSignerShare(bitgoToUserEncryptedSignerShare);
+    const stringifiedRShare = JSON.stringify(userSignShare);
+    const encryptedRShare = this.bitgo.encrypt({ input: stringifiedRShare, password: params.walletPassphrase });
+    const encryptedUserToBitgoRShare = this.createUserToBitgoEncryptedRShare(encryptedRShare);
+
+    return { userToBitgoCommitment, encryptedSignerShare, encryptedUserToBitgoRShare };
+  }
+
+  async createRShareFromTxRequest(params: {
+    txRequest: TxRequest;
+    prv: string;
+    walletPassphrase?: string;
+    encryptedUserToBitgoRShare?: EncryptedSignerShareRecord;
+  }): Promise<{ rShare: SignShare; signingKeyYShare: YShare }> {
+    const { txRequest, prv, walletPassphrase, encryptedUserToBitgoRShare } = params;
+    const txRequestResolved: TxRequest = txRequest;
+
+    const hdTree = await Ed25519BIP32.initialize();
+    const MPC = await Eddsa.initialize(hdTree);
+
+    const userSigningMaterial: SigningMaterial = JSON.parse(prv);
+    if (!userSigningMaterial.backupYShare) {
+      throw new Error('Invalid user key - missing backupYShare');
+    }
+
+    assert(txRequestResolved.transactions || txRequestResolved.unsignedTxs, 'Unable to find transactions in txRequest');
+    const unsignedTx =
+      txRequestResolved.apiVersion === 'full'
+        ? txRequestResolved.transactions![0].unsignedTx
+        : txRequestResolved.unsignedTxs[0];
+
+    const signingKey = MPC.keyDerive(
+      userSigningMaterial.uShare,
+      [userSigningMaterial.bitgoYShare, userSigningMaterial.backupYShare],
+      unsignedTx.derivationPath
+    );
+
+    let rShare: SignShare;
+    if (walletPassphrase && encryptedUserToBitgoRShare) {
+      const decryptedRShare = this.bitgo.decrypt({
+        input: encryptedUserToBitgoRShare.share,
+        password: walletPassphrase,
+      });
+      rShare = JSON.parse(decryptedRShare);
+      assert(rShare.xShare, 'Unable to find xShare in decryptedRShare');
+      assert(rShare.rShares, 'Unable to find rShares in decryptedRShare');
+    } else {
+      const signablePayload = Buffer.from(unsignedTx.signableHex, 'hex');
+
+      rShare = await createUserSignShare(signablePayload, signingKey.pShare);
+    }
 
-    return { rShare: userSignShare, signingKeyYShare: signingKey.yShares[3] };
+    return { rShare, signingKeyYShare: signingKey.yShares[3] };
   }
 
   async createGShareFromTxRequest(params: {
@@ -603,6 +668,15 @@ export class EddsaUtils extends baseTSSUtils<KeyShare> {
       type: EncryptedSignerShareType.ENCRYPTED_SIGNER_SHARE,
     };
   }
+
+  createUserToBitgoEncryptedRShare(encryptedRShare: string): EncryptedSignerShareRecord {
+    return {
+      from: SignatureShareType.USER,
+      to: SignatureShareType.BITGO,
+      share: encryptedRShare,
+      type: EncryptedSignerShareType.ENCRYPTED_R_SHARE,
+    };
+  }
 }
 /**
  * @deprecated - use EddsaUtils