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// Copyright (C) 2026 Doan Luu Duc Tai <doan@luuduct.ai>
//
// This program is free software: you can redistribute it and/or modify
// it under the terms of the GNU Affero General Public License as
// published by the Free Software Foundation, either version 3 of the
// License, or (at your option) any later version.
//
// This program is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
// GNU Affero General Public License for more details.
//
// You should have received a copy of the GNU Affero General Public License
// along with this program. If not, see <https://www.gnu.org/licenses/>.
// @license magnet:?xt=urn:btih:0b31508aeb0634b347b8270c7bee4d411b5d4109&dn=agpl-3.0.txt AGPL-3.0
async function execute(bytes: ArrayBuffer, input: string): Promise<StackChat.Execution> {
let memory: WebAssembly.Memory | undefined;
let output = '';
let errors = '';
const stdoutDecoder = new TextDecoder('utf-8', { fatal: true });
const stderrDecoder = new TextDecoder('utf-8', { fatal: true });
const stdin = new TextEncoder().encode(input);
let position = 0;
let randomCalls = 0;
let randomBytes = 0;
const memoryBuffer = (): ArrayBuffer => {
if (!memory) throw new Error('WASI memory is unavailable');
return memory.buffer;
};
const data = (): DataView => new DataView(memoryBuffer());
const put32 = (address: number, value: number) => data().setUint32(address, value, true);
const noEntries = (count: number, size: number) => { put32(count, 0); put32(size, 0); return 0; };
class Exit extends Error {
readonly code: number;
constructor(code: number) { super(`WASI exit ${code}`); this.code = code; }
}
const wasi: Record<string, WebAssembly.ImportValue> = {
args_sizes_get: noEntries,
environ_sizes_get: noEntries,
args_get: () => 0,
environ_get: () => 0,
random_get(address: number, length: number) {
const buffer = new Uint8Array(memoryBuffer(), address, length);
for (let offset = 0; offset < length; offset += 65536) {
crypto.getRandomValues(buffer.subarray(offset, Math.min(offset + 65536, length)));
}
randomCalls += 1;
randomBytes += length;
return 0;
},
clock_time_get(clock: number, _precision: bigint, address: number) {
if (clock !== 0 && clock !== 1) return 52;
const milliseconds = clock === 0 ? Date.now() : performance.now();
data().setBigUint64(address, BigInt(Math.floor(milliseconds * 1000000)), true);
return 0;
},
clock_res_get(_clock: number, address: number) { data().setBigUint64(address, 1000000n, true); return 0; },
fd_write(fd: number, vectors: number, count: number, written: number) {
if (fd !== 1 && fd !== 2) return 8;
let total = 0;
for (let index = 0; index < count; index += 1) {
const address = data().getUint32(vectors + index * 8, true);
const length = data().getUint32(vectors + index * 8 + 4, true);
const text = (fd === 1 ? stdoutDecoder : stderrDecoder).decode(new Uint8Array(memoryBuffer(), address, length), { stream: true });
if (fd === 1) output += text; else errors += text;
total += length;
if (output.length + errors.length > 1048576) throw new Error('Probe output exceeded its limit');
}
put32(written, total);
return 0;
},
fd_read(fd: number, vectors: number, count: number, read: number) {
if (fd !== 0) return 8;
let total = 0;
for (let index = 0; index < count && position < stdin.length; index += 1) {
const address = data().getUint32(vectors + index * 8, true);
const capacity = data().getUint32(vectors + index * 8 + 4, true);
const length = Math.min(capacity, stdin.length - position);
new Uint8Array(memoryBuffer(), address, length).set(stdin.subarray(position, position + length));
position += length;
total += length;
}
put32(read, total);
return 0;
},
fd_fdstat_get(fd: number, address: number) {
if (fd > 2) return 8;
new Uint8Array(memoryBuffer(), address, 24).fill(0);
data().setUint8(address, 2);
return 0;
},
fd_fdstat_set_flags: (fd: number) => fd <= 2 ? 0 : 8,
fd_prestat_get: () => 8,
fd_prestat_dir_name: () => 8,
fd_close: (fd: number) => fd <= 2 ? 0 : 8,
fd_seek: () => 70,
fd_tell: () => 70,
fd_filestat_get: () => 8,
path_open: () => 76,
sched_yield: () => 0,
proc_exit(code: number) { throw new Exit(code); },
};
for (const name of [
'fd_readdir', 'fd_advise', 'fd_allocate', 'fd_datasync', 'fd_sync',
'fd_filestat_set_size', 'fd_filestat_set_times', 'fd_fdstat_set_rights',
'path_filestat_get', 'path_filestat_set_times', 'path_readlink', 'path_unlink_file',
'path_rename', 'path_create_directory', 'path_remove_directory', 'path_link', 'path_symlink',
'sock_accept', 'sock_recv', 'sock_send', 'sock_shutdown', 'poll_oneoff',
]) wasi[name] = () => 76;
const module = await WebAssembly.compile(bytes);
for (const entry of WebAssembly.Module.imports(module)) {
if (entry.module !== 'wasi_snapshot_preview1' || typeof wasi[entry.name] !== 'function') {
throw new Error(`Unsupported WASI import: ${entry.module}.${entry.name}`);
}
}
const instance = await WebAssembly.instantiate(module, { wasi_snapshot_preview1: wasi });
const exportedMemory = instance.exports['memory'];
const start = instance.exports['_start'];
if (!(exportedMemory instanceof WebAssembly.Memory) || typeof start !== 'function') throw new Error('Invalid WASI exports');
memory = exportedMemory;
try { start(); }
catch (error) { if (!(error instanceof Exit) || error.code !== 0) throw new Error(`${error instanceof Error ? error.message : 'WASI execution failed'}: ${errors}`); }
output += stdoutDecoder.decode();
errors += stderrDecoder.decode();
stdin.fill(0);
return { output, randomCalls, randomBytes };
}
async function runProbe(bytes: ArrayBuffer) {
const result = await execute(bytes, '');
if (!result.output.startsWith('PASS: backend=OpenSSL ') || result.randomCalls === 0) {
throw new Error('OpenSSL probe did not pass');
}
return result;
}
async function runCommand(bytes: ArrayBuffer, request: StackChat.CryptoRequest): Promise<unknown> {
const input = JSON.stringify(request);
if (input.length > 8388608) throw new Error('Crypto request exceeds its limit');
const result = await execute(bytes, input);
const response: unknown = JSON.parse(result.output);
if (typeof response !== 'object' || response === null || Array.isArray(response)) throw new Error('Invalid crypto response');
if ('error' in response) throw new Error(typeof response.error === 'string' ? response.error : 'Cryptographic operation failed');
return response;
}
globalThis.stackChatWasi = Object.freeze({ runCommand, runProbe });
// @license-end
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