fix(sol): decode Token-2022 unknown data as base64

Decode unknown Token-2022 instruction data as base64 before checking confidential-transfer discriminators.\n\nThis prevents BurnChecked pending approvals from throwing Non-base58 character during transaction explanation.\n\nTicket: CHALO-1512

Session-Id: b8d737f7-739a-42bb-81a7-a9fbaf1ec4a6
Task-Id: 6288c7bd-acc3-46ee-a0bf-b5f2d595384e

Author: akarath

modules/sdk-coin-sol/src/lib/explainTransactionWasm.ts

@@ -9,7 +9,6 @@ import {
 } from './constants';
 import { StakingAuthorizeParams, TransactionExplanation as SolLibTransactionExplanation } from './iface';
 import { findTokenName } from './instructionParamsFactory';
-import bs58 from 'bs58';
 
 export interface ExplainTransactionWasmOptions {
   txBase64: string;
@@ -110,7 +109,7 @@ function isWasmConfidentialTransferInstruction(instr: InstructionParams): boolea
   // Token-2022 CT extension: byte 0 = CT_EXT_DISCRIMINATOR, byte 1 ∈ CT_SUB_DISCRIMINATORS
   const TOKEN_2022_PROGRAM_ID = 'TokenzQdBNbLqP5VEhdkAS6EPFLC1PHnBqCXEpPxuEb';
   if (programId === TOKEN_2022_PROGRAM_ID) {
-    const dataBytes = bs58.decode(instr.data);
+    const dataBytes = Buffer.from(instr.data, 'base64');
     if (dataBytes.length >= 2) {
       return dataBytes[0] === CT_EXT_DISCRIMINATOR && CT_SUB_DISCRIMINATORS.has(dataBytes[1]);
     }

modules/sdk-coin-sol/test/unit/explainTransactionWasm.ts

@@ -45,6 +45,21 @@ describe('explainTransactionWasm', function () {
       explained.tokenEnablements?.[0].tokenName.should.equal('3VDBJWgzRUscjQzzAp52na1dDquExZmD1PkCvH9svGF6');
     });
 
+    it('should classify a Token-2022 BurnChecked unknown instruction as CustomTx', function () {
+      // BurnChecked is not decoded by the WASM parser, so it is emitted as Unknown with
+      // base64-encoded data. This must not throw while checking for confidential transfers.
+      const TOKEN_2022_BURN_CHECKED_BASE64 =
+        'AQAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAABAAIEd4VubrtXALIH766Ipu/Fvh26FyvOPjpBMkYBe3UO30SFN5lu5h+qbiflw3DnoJGsdJ035d0WtazcVkIoE5FhOgk/IBzpsSfv2fKcdhTIHFEQKNBi10zrLtUIacusFNtQBt324e51j94YQl285GzN2rYa/E2DuQ0n/r35KNihi/wAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAEDAwECAAoKQEIPAAAAAAAG';
+
+      const explained = explainSolTransaction({
+        txBase64: TOKEN_2022_BURN_CHECKED_BASE64,
+        feeInfo: { fee: '5000' },
+        coinName: 'tsol',
+      });
+
+      explained.type.should.equal('CustomTx');
+    });
+
     it('should classify token transfer with Token ACL permissionless thaw as Send', function () {
       // TokenTransfer (transferChecked, Token-2022) + Token ACL ThawPermissionlessIdempotent for
       // the destination ATA. The Unknown thaw instruction previously triggered the CustomTx