initial commit

fluxer_api/src/utils/MediaProxyUtils.ts

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+/*
+ * Copyright (C) 2026 Fluxer Contributors
+ *
+ * This file is part of Fluxer.
+ *
+ * Fluxer 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.
+ *
+ * Fluxer 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 Fluxer. If not, see <https://www.gnu.org/licenses/>.
+ */
+
+import crypto from 'node:crypto';
+
+const BASE64_URL_REGEX = /=*$/;
+
+const encodeComponent = (component: string) => encodeURIComponent(component).replace(/%2F/g, '/');
+const decodeComponent = (component: string) => decodeURIComponent(component);
+
+export const getProxyURLPath = (inputUrl: string): string => {
+	const parsedUrl = new URL(inputUrl);
+	const query = parsedUrl.search.slice(1);
+	const protocol = parsedUrl.protocol.slice(0, -1);
+	const hostname = parsedUrl.hostname;
+	const port = parsedUrl.port;
+	const path = parsedUrl.pathname.slice(1);
+	const encodedQuery = query ? `${encodeComponent(query)}/` : '';
+	const encodedHostname = encodeComponent(hostname);
+	const encodedPort = port ? `:${encodeComponent(port)}` : '';
+	const encodedPath = encodeComponent(path);
+	return `${encodedQuery}${protocol}/${encodedHostname}${encodedPort}/${encodedPath}`;
+};
+
+export const createSignature = (inputString: string, mediaProxySecretKey: string): string => {
+	const hmac = crypto.createHmac('sha256', mediaProxySecretKey);
+	hmac.update(inputString);
+	return hmac.digest('base64url').replace(BASE64_URL_REGEX, '');
+};
+
+interface MediaProxyParams {
+	inputURL: string;
+	mediaProxyEndpoint: string;
+	mediaProxySecretKey: string;
+}
+
+export const getExternalMediaProxyURL = ({
+	inputURL,
+	mediaProxyEndpoint,
+	mediaProxySecretKey,
+}: MediaProxyParams): string => {
+	const proxyUrlPath = getProxyURLPath(inputURL);
+	const proxyUrlSignature = createSignature(proxyUrlPath, mediaProxySecretKey);
+	return `${mediaProxyEndpoint}/external/${proxyUrlSignature}/${proxyUrlPath}`;
+};
+
+export const verifySignature = (
+	proxyUrlPath: string,
+	providedSignature: string,
+	mediaProxySecretKey: string,
+): boolean => {
+	const expectedSignature = createSignature(proxyUrlPath, mediaProxySecretKey);
+	return crypto.timingSafeEqual(Buffer.from(expectedSignature), Buffer.from(providedSignature));
+};
+
+export const reconstructOriginalURL = (proxyUrlPath: string): string => {
+	const parts = proxyUrlPath.split('/');
+	let currentIndex = 0;
+	let query = '';
+	if (parts[currentIndex].includes('%3D')) {
+		query = decodeComponent(parts[currentIndex]);
+		currentIndex += 1;
+	}
+	const protocol = parts[currentIndex++];
+	if (!protocol) throw new Error('Protocol is missing in the proxy URL path.');
+	const hostPart = parts[currentIndex++];
+	if (!hostPart) throw new Error('Hostname is missing in the proxy URL path.');
+	const [encodedHostname, encodedPort] = hostPart.split(':');
+	const hostname = decodeComponent(encodedHostname);
+	const port = encodedPort ? decodeComponent(encodedPort) : '';
+	const encodedPath = parts.slice(currentIndex).join('/');
+	const path = decodeComponent(encodedPath);
+	return `${protocol}://${hostname}${port ? `:${port}` : ''}/${path}${query ? `?${query}` : ''}`;
+};