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ThreadNet-Web/apps/web/src/utils/ContentScanner.ts
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/*
Copyright 2026 aXion1337
SPDX-License-Identifier: AGPL-3.0-only OR GPL-3.0-only OR LicenseRef-Element-Commercial
Please see LICENSE files in the repository root for full details.
*/
// Client-side ClamAV scanning (Issue #19 extension): Synapse's own server-side spam-checker
// module can never see E2EE attachment content - only a cooperating client can, since only
// the client ever holds the room's decryption key. This calls a small self-hosted scan
// service (same ClamAV instance the server-side module uses) directly from the browser, both
// before encrypting/uploading a file and after downloading/decrypting one - see
// ContentMessages.ts (send) and DecryptFile.ts (receive) for the two call sites.
import { logger } from "matrix-js-sdk/src/logger";
export class ContentScanRejectedError extends Error {
public readonly signature: string;
public constructor(signature: string) {
super(`Blocked by content scanner: ${signature}`);
this.name = "ContentScanRejectedError";
this.signature = signature;
}
}
/**
* Scans plaintext bytes against the self-hosted ClamAV scan service.
* Fails open (resolves normally) on any network/scanner-side error, matching the same
* fail-open policy as the server-side Synapse module - a scanner outage should not block
* uploads or downloads site-wide.
* @throws {ContentScanRejectedError} if the scanner positively identifies the content as infected.
*/
export async function scanContent(data: ArrayBuffer | ArrayBufferView, accessToken: string): Promise<void> {
let response: Response;
try {
response = await fetch("/_scan", {
method: "POST",
headers: { Authorization: `Bearer ${accessToken}` },
body: data as BodyInit,
});
} catch (e) {
logger.warn("Content scan request failed (scanner unreachable?) - allowing through", e);
return;
}
if (!response.ok) {
logger.warn("Content scan request failed with status", response.status, "- allowing through");
return;
}
let result: { clean: boolean; signature?: string };
try {
result = await response.json();
} catch (e) {
logger.warn("Content scan response was not valid JSON - allowing through", e);
return;
}
if (result.clean === false) {
throw new ContentScanRejectedError(result.signature ?? "unknown");
}
}