60 lines
1.8 KiB
JavaScript
60 lines
1.8 KiB
JavaScript
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// Minimal fake DSH for the socat-WS PoC: plain HTTP on 127.0.0.1:8080 plus a
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// WebSocket echo (handshake + one text-frame round-trip) using only node built-ins.
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import { createServer } from 'node:http'
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import { createHash } from 'node:crypto'
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const GUID = '258EAFA5-E914-47DA-95CA-C5AB0DC85B11'
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const acceptKey = (key) => createHash('sha1').update(key + GUID).digest('base64')
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const server = createServer((req, res) => {
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res.writeHead(200, { 'Content-Type': 'text/plain' })
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res.end('fake-dsh\n')
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})
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server.on('upgrade', (req, socket) => {
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const key = req.headers['sec-websocket-key']
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if (!key) {
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socket.destroy()
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return
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}
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socket.write(
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'HTTP/1.1 101 Switching Protocols\r\n' +
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'Upgrade: websocket\r\n' +
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'Connection: Upgrade\r\n' +
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`Sec-WebSocket-Accept: ${acceptKey(key)}\r\n\r\n`,
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)
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socket.on('data', (buf) => {
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const opcode = buf[0] & 0x0f
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if (opcode === 0x8) {
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socket.end()
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return
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}
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if (opcode !== 0x1 && opcode !== 0x2) return
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const masked = (buf[1] & 0x80) !== 0
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let len = buf[1] & 0x7f
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let offset = 2
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if (len === 126) {
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len = buf.readUInt16BE(2)
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offset = 4
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} else if (len === 127) {
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return // not exercised in the PoC
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}
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let maskKey
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if (masked) {
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maskKey = buf.subarray(offset, offset + 4)
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offset += 4
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}
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const payload = Buffer.from(buf.subarray(offset, offset + len))
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if (masked && maskKey) {
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for (let i = 0; i < payload.length; i++) payload[i] ^= maskKey[i % 4]
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}
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// Echo back as an unmasked text frame.
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const out = Buffer.alloc(2 + payload.length)
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out[0] = 0x81
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out[1] = payload.length
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payload.copy(out, 2)
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socket.write(out)
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})
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})
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server.listen(8080, '127.0.0.1', () => console.log('fake-dsh listening on 127.0.0.1:8080'))
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