fix(wasi-shim): re-read memory.buffer after await in all host functions

WebAssembly memory can grow (and return a new ArrayBuffer) during an
async host function call. Reading memory.buffer before await and using
it after the await causes host functions (kv_get / crypto_decrypt /
crypto_sign_rs256 / http_request) to write into a detached buffer,
so the WASM side reads zero bytes → empty string → JSON parse failure.

Fix: read inputs before await using the current buffer snapshot,
then call memory.buffer again after the await to write the result.
For crypto_sign_rs256 and http_request, input arrays are copied
before await so the snapshot can be released.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

cypher-executor/src/lib/wasi-shim.ts

@@ -221,15 +221,17 @@ export function createWasiShim(stdinData: string, hostFunctions?: WasiHostFuncti
               headersPtr: number, headersLen: number, bodyPtr: number, bodyLen: number,
               outPtr: number, outLenPtr: number): Promise<number> => {
               if (!memory) return 1;
-              const buf = memory.buffer;
+              // 在 await 前讀完所有輸入（memory.buffer 在 await 後可能因 grow 而失效）
+              const snapBuf = memory.buffer;
               const dec = new TextDecoder();
-              const url = dec.decode(new Uint8Array(buf, urlPtr, urlLen));
+              const url = dec.decode(new Uint8Array(snapBuf, urlPtr, urlLen));
-              const method = dec.decode(new Uint8Array(buf, methodPtr, methodLen));
+              const method = dec.decode(new Uint8Array(snapBuf, methodPtr, methodLen));
-              const headers = dec.decode(new Uint8Array(buf, headersPtr, headersLen));
+              const headers = dec.decode(new Uint8Array(snapBuf, headersPtr, headersLen));
-              const body = dec.decode(new Uint8Array(buf, bodyPtr, bodyLen));
+              const body = dec.decode(new Uint8Array(snapBuf, bodyPtr, bodyLen));
               try {
                 const result = await hostFunctions!.http_request!(url, method, headers, body);
-                return writeOut(buf, outPtr, outLenPtr, new TextEncoder().encode(result));
+                // await 後重新拿 memory.buffer（grow 會產生新的 ArrayBuffer）
+                return writeOut(memory.buffer, outPtr, outLenPtr, new TextEncoder().encode(result));
               } catch {
                 return 1;
               }
@@ -240,12 +242,11 @@ export function createWasiShim(stdinData: string, hostFunctions?: WasiHostFuncti
         kv_get: hostFunctions?.kv_get
           ? async (keyPtr: number, keyLen: number, outPtr: number, outLenPtr: number): Promise<number> => {
               if (!memory) return 1;
-              const buf = memory.buffer;
+              const key = new TextDecoder().decode(new Uint8Array(memory.buffer, keyPtr, keyLen));
-              const key = new TextDecoder().decode(new Uint8Array(buf, keyPtr, keyLen));
               try {
                 const result = await hostFunctions!.kv_get!(key);
                 if (result === null) return 2;
-                return writeOut(buf, outPtr, outLenPtr, new TextEncoder().encode(result));
+                return writeOut(memory.buffer, outPtr, outLenPtr, new TextEncoder().encode(result));
               } catch {
                 return 1;
               }
@@ -258,13 +259,12 @@ export function createWasiShim(stdinData: string, hostFunctions?: WasiHostFuncti
           ? async (encPtr: number, encLen: number, ivPtr: number, ivLen: number,
               outPtr: number, outLenPtr: number): Promise<number> => {
               if (!memory) return 1;
-              const buf = memory.buffer;
               const dec = new TextDecoder();
-              const encB64 = dec.decode(new Uint8Array(buf, encPtr, encLen));
+              const encB64 = dec.decode(new Uint8Array(memory.buffer, encPtr, encLen));
-              const ivB64 = dec.decode(new Uint8Array(buf, ivPtr, ivLen));
+              const ivB64 = dec.decode(new Uint8Array(memory.buffer, ivPtr, ivLen));
               try {
                 const plaintext = await hostFunctions!.crypto_decrypt!(encB64, ivB64);
-                return writeOut(buf, outPtr, outLenPtr, new TextEncoder().encode(plaintext));
+                return writeOut(memory.buffer, outPtr, outLenPtr, new TextEncoder().encode(plaintext));
               } catch {
                 return 1;
               }
@@ -276,12 +276,12 @@ export function createWasiShim(stdinData: string, hostFunctions?: WasiHostFuncti
           ? async (dataPtr: number, dataLen: number, pkcs8Ptr: number, pkcs8Len: number,
               outPtr: number, outLenPtr: number): Promise<number> => {
               if (!memory) return 1;
-              const buf = memory.buffer;
+              // await 前複製 typed array（避免 memory grow 後 buffer 失效）
-              const data = new Uint8Array(new Uint8Array(buf, dataPtr, dataLen));
+              const data = new Uint8Array(new Uint8Array(memory.buffer, dataPtr, dataLen));
-              const pkcs8 = new Uint8Array(new Uint8Array(buf, pkcs8Ptr, pkcs8Len));
+              const pkcs8 = new Uint8Array(new Uint8Array(memory.buffer, pkcs8Ptr, pkcs8Len));
               try {
                 const sig = await hostFunctions!.crypto_sign_rs256!(data, pkcs8);
-                return writeOut(buf, outPtr, outLenPtr, sig);
+                return writeOut(memory.buffer, outPtr, outLenPtr, sig);
               } catch {
                 return 1;
               }