feat: expand frame type to support stdout/stderr chan

app/server/agent/encoder.ts

@@ -0,0 +1,99 @@
+// Refer to agent/internal/sshutil/encoder.go for more details
+// This is the Node.js implementation of the SSH encoder
+import log from '~/utils/log';
+
+const MAGIC = 'HPLS';
+const VERSION = 1;
+
+// 0 -> Stdin
+// 1 -> Stdout
+// 2 -> Stderr
+export type ChannelType = 0 | 1 | 2;
+
+interface SSHFrame {
+	sessionId: string;
+	channel: ChannelType;
+	payload: Blob | ArrayBufferLike | string;
+}
+
+export async function encodeSSHFrame(frame: SSHFrame) {
+	const sid = Buffer.from(frame.sessionId, 'utf8');
+	if (sid.length > 255) {
+		log.error('agent', 'SSH session ID too long: %s', frame.sessionId);
+		return;
+	}
+
+	const payload = Buffer.isBuffer(frame.payload)
+		? frame.payload
+		: typeof frame.payload === 'string'
+			? Buffer.from(frame.payload, 'utf8')
+			: frame.payload instanceof Blob
+				? Buffer.from(await frame.payload.arrayBuffer())
+				: Buffer.from(frame.payload);
+
+	// Size can only hold 4 bytes
+	if (payload.length > 0xffffffff) {
+		log.error('agent', 'SSH payload too large: %d bytes', payload.length);
+		return;
+	}
+
+	const frameSize =
+		4 + // Magic
+		1 + // Version
+		1 + // Channel Type
+		(1 + sid.length) + // Session ID length + SID
+		(4 + payload.length); // Payload length + Payload
+
+	const buf = Buffer.alloc(frameSize);
+	buf.write(MAGIC, 0, 'utf8');
+	buf.writeUInt8(VERSION, 4);
+	buf.writeUInt8(frame.channel, 5);
+	buf.writeUInt8(sid.length, 6);
+
+	const offset = 7 + sid.length;
+	sid.copy(buf, 7);
+
+	buf.writeUInt32BE(payload.length, offset);
+	payload.copy(buf, offset + 4);
+	return buf;
+}
+
+export function decodeSSHFrame(data: Buffer) {
+	if (data.length < 5) {
+		log.error('agent', 'SSH frame too short: %d bytes', data.length);
+		return;
+	}
+
+	const magic = data.toString('utf8', 0, 4);
+	const version = data.readUInt8(4);
+
+	if (magic !== MAGIC || version !== VERSION) {
+		log.error('agent', 'Invalid SSH frame magic or version');
+		return;
+	}
+
+	const channel = data.readUInt8(5) as ChannelType;
+	const sidLength = data.readUInt8(6);
+	if (data.length < 7 + sidLength + 4) {
+		log.error('agent', 'SSH frame too short for session ID and payload');
+		return;
+	}
+
+	const sessionId = data.toString('utf8', 7, 7 + sidLength);
+	const payloadLength = data.readUInt32BE(7 + sidLength);
+	if (data.length < 7 + sidLength + 4 + payloadLength) {
+		log.error('agent', 'SSH frame too short for payload');
+		return;
+	}
+
+	const payload = data.subarray(
+		7 + sidLength + 4,
+		7 + sidLength + 4 + payloadLength,
+	);
+
+	return {
+		sessionId,
+		channel,
+		payload,
+	};
+}