╭─────────────╮ │scroll to top│ ╰─────────────╯ ╭ serve_ssh_protocol.zig ───────────────────────────────────────╮ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ ╰───────────────────────────────────────────────────────────────╯
🬐 🬠 🬞🬂🬏 🬟 🬑 🬟 🬑 ╭3f636941..╮ 3f636941.. see-em: 🬋🬋🬋 🬋🬋🬋 🬋 🬋 │files │ commits refs discuss issues new login 🬐 🬠 🬐 🬠 🬑 🬟 🬰 ╰──────────╯ (95) user
╭────╮ ╭ clone ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ╮ │http│ ssh │ │ ╰────╯ ╰ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ╯
.. embed/ event/ test/ ui/ command.zig event.zig lib.zig main.zig main_wasm.zig serve.zig serve_ssh.zig ╭─────────────────────────────────╮ │serve_ssh_protocol.zig │ ╰─────────────────────────────────╯ test.zig testnet.zig try.zig ui.zig web.zig
1205 if (!std.mem.eql(u8, algo, "ssh-ed25519")) { 1206 auth_attempts += 1; 1207 if (auth_attempts >= max_auth_attempts) return error.TooManyAuthAttempts; 1208 try sendUserauthFailure(io, allocator, sc_cipher, writer); 1209 continue; 1210 } 1211 1212 if (!has_signature) { 1213 // probe — tell the client this key is acceptable so it'll send 1214 // the signed version next. 1215 var pk_ok: std.ArrayList(u8) = .empty; 1216 defer pk_ok.deinit(allocator); 1217 try pk_ok.append(allocator, SSH_MSG_USERAUTH_PK_OK); 1218 try writeStringField(&pk_ok, allocator, algo); 1219 try writeStringField(&pk_ok, allocator, pubkey_blob); 1220 try sc_cipher.writePacket(io, allocator, writer, pk_ok.items); 1221 continue; 1222 } 1223 1224 // has signature — verify it 1225 const signature_blob = try takeStringField(allocator, &req_reader, 1024); 1226 defer allocator.free(signature_blob); 1227 1228 const ok = verifyUserauthSignature( 1229 allocator, 1230 session_id, 1231 user_name, 1232 service_name, 1233 algo, 1234 pubkey_blob, 1235 signature_blob, 1236 ) catch false; 1237 1238 if (!ok) { 1239 auth_attempts += 1; 1240 if (auth_attempts >= max_auth_attempts) return error.TooManyAuthAttempts; 1241 try sendUserauthFailure(io, allocator, sc_cipher, writer); 1242 continue; 1243 } 1244 1245 try sc_cipher.writePacket(io, allocator, writer, &[_]u8{SSH_MSG_USERAUTH_SUCCESS}); 1246 return formatFingerprint(pubkey_blob); 1247 } 1248 } 1249 1250 fn sendUserauthFailure( 1251 io: std.Io, 1252 allocator: std.mem.Allocator, 1253 sc_cipher: *Cipher, 1254 writer: *std.Io.Writer, 1255 ) !void { 1256 var buf: std.ArrayList(u8) = .empty; 1257 defer buf.deinit(allocator); 1258 try buf.append(allocator, SSH_MSG_USERAUTH_FAILURE); 1259 try writeNameList(&buf, allocator, &.{"publickey"}); // allowed methods 1260 try buf.append(allocator, 0); // partial_success = false 1261 try sc_cipher.writePacket(io, allocator, writer, buf.items); 1262 } 1263 1264 fn sendDisconnect( 1265 io: std.Io, 1266 allocator: std.mem.Allocator, 1267 sc_cipher: *Cipher, 1268 writer: *std.Io.Writer, 1269 description: []const u8, 1270 ) !void { 1271 var buf: std.ArrayList(u8) = .empty; 1272 defer buf.deinit(allocator); 1273 try buf.append(allocator, SSH_MSG_DISCONNECT); 1274 try writeU32(&buf, allocator, SSH_DISCONNECT_PROTOCOL_ERROR); 1275 try writeStringField(&buf, allocator, description); 1276 try writeStringField(&buf, allocator, ""); 1277 try sc_cipher.writePacket(io, allocator, writer, buf.items); 1278 } 1279 1280 // build the bytes a publickey signature is computed over (RFC 4252 §7) and 1281 // verify the supplied signature against them. 1282 fn verifyUserauthSignature( 1283 allocator: std.mem.Allocator, 1284 session_id: *const [Sha256.digest_length]u8, 1285 user_name: []const u8, 1286 service_name: []const u8, 1287 algo: []const u8, 1288 pubkey_blob: []const u8, 1289 signature_blob: []const u8, 1290 ) !bool { 1291 // signed data: 1292 // string session_id 1293 // byte SSH_MSG_USERAUTH_REQUEST 1294 // string user_name 1295 // string service_name 1296 // string "publickey" 1297 // bool TRUE 1298 // string algo 1299 // string pubkey 1300 var signed: std.ArrayList(u8) = .empty; 1301 defer signed.deinit(allocator); 1302 try writeStringField(&signed, allocator, session_id); 1303 try signed.append(allocator, SSH_MSG_USERAUTH_REQUEST); 1304 try writeStringField(&signed, allocator, user_name); 1305 try writeStringField(&signed, allocator, service_name); 1306 try writeStringField(&signed, allocator, "publickey"); 1307 try signed.append(allocator, 1); 1308 try writeStringField(&signed, allocator, algo); 1309 try writeStringField(&signed, allocator, pubkey_blob); 1310 1311 // parse pubkey_blob: string "ssh-ed25519" || string raw_pubkey 1312 var pubkey_reader = std.Io.Reader.fixed(pubkey_blob); 1313 const pk_algo = try takeStringField(allocator, &pubkey_reader, 64); 1314 defer allocator.free(pk_algo); 1315 if (!std.mem.eql(u8, pk_algo, "ssh-ed25519")) return false; 1316 const raw_pubkey = try takeStringField(allocator, &pubkey_reader, 64); 1317 defer allocator.free(raw_pubkey); 1318 if (raw_pubkey.len != Ed25519.PublicKey.encoded_length) return false; 1319 1320 // parse signature_blob: string "ssh-ed25519" || string raw_signature 1321 var sig_reader = std.Io.Reader.fixed(signature_blob); 1322 const sig_algo = try takeStringField(allocator, &sig_reader, 64); 1323 defer allocator.free(sig_algo); 1324 if (!std.mem.eql(u8, sig_algo, "ssh-ed25519")) return false; 1325 const raw_sig = try takeStringField(allocator, &sig_reader, Ed25519.Signature.encoded_length); 1326 defer allocator.free(raw_sig); 1327 if (raw_sig.len != Ed25519.Signature.encoded_length) return false; 1328 1329 var pubkey_bytes: [Ed25519.PublicKey.encoded_length]u8 = undefined; 1330 @memcpy(&pubkey_bytes, raw_pubkey); 1331 var sig_bytes: [Ed25519.Signature.encoded_length]u8 = undefined; 1332 @memcpy(&sig_bytes, raw_sig); 1333 1334 const pk = Ed25519.PublicKey.fromBytes(pubkey_bytes) catch return false; 1335 const sig = Ed25519.Signature.fromBytes(sig_bytes); 1336 sig.verify(signed.items, pk) catch return false; 1337 return true; 1338 } 1339 1340 // --------------------------------------------------------------------------- 1341 // connection layer (RFC 4254): channels, requests, data, flow control 1342 // --------------------------------------------------------------------------- 1343 1344 const Channel = struct { 1345 local_id: u32, 1346 remote_id: u32, 1347 local_window: u32, // bytes peer may still send us before we adjust 1348 remote_window: u32, // bytes we may still send to peer before they adjust 1349 max_packet: u32, // max CHANNEL_DATA payload the peer accepts in one packet 1350 eof_received: bool = false, 1351 pty: ?PtySize = null, 1352 }; 1353 1354 pub const PtySize = struct { width_cells: u16, height_cells: u16 }; 1355 1356 fn runChannelLayer( 1357 io: std.Io, 1358 allocator: std.mem.Allocator, 1359 reader: *std.Io.Reader, 1360 writer: *std.Io.Writer, 1361 cs_cipher: *Cipher, 1362 sc_cipher: *Cipher, 1363 fingerprint: *const [fingerprint_len]u8, 1364 handler: anytype, 1365 ) !void { 1366 var channel: ?Channel = null; 1367 var pending_exec: ?[]u8 = null; 1368 defer if (pending_exec) |s| allocator.free(s); 1369 1370 while (true) { 1371 const packet = try cs_cipher.readPacket(allocator, reader); 1372 defer allocator.free(packet); 1373 if (packet.len < 1) return error.EmptyPacket; 1374 const msg_type = packet[0]; 1375 1376 switch (msg_type) { 1377 SSH_MSG_GLOBAL_REQUEST => try handleGlobalRequest(io, allocator, sc_cipher, writer, packet), 1378 1379 SSH_MSG_KEXINIT => { 1380 try sendDisconnect(io, allocator, sc_cipher, writer, "rekey is not supported"); 1381 return error.RekeyUnsupported; 1382 }, 1383 1384 SSH_MSG_CHANNEL_OPEN => { 1385 if (channel != null) { 1386 try sendChannelOpenFailure(io, allocator, sc_cipher, writer, packet, SSH_OPEN_RESOURCE_SHORTAGE, "only one channel per connection"); 1387 continue; 1388 } 1389 channel = try handleChannelOpen(io, allocator, sc_cipher, writer, packet) orelse continue; 1390 }, 1391 1392 SSH_MSG_CHANNEL_REQUEST => { 1393 const ch = if (channel) |*c| c else continue; 1394 const start_request = try handleChannelRequest(io, allocator, sc_cipher, writer, ch, packet, &pending_exec); 1395 if (start_request) |req_kind| { 1396 const request: Request = switch (req_kind) { 1397 .shell => .{ .shell = ch.pty }, 1398 .exec => .{ .exec = pending_exec.? }, 1399 }; 1400 var sess = SessionCtx{ 1401 .io = io, 1402 .allocator = allocator, 1403 .reader = reader, 1404 .writer = writer, 1405 .cs_cipher = cs_cipher, 1406 .sc_cipher = sc_cipher, 1407 .channel = ch, 1408 .fingerprint = fingerprint.*, 1409 }; 1410 defer sess.deinit(); 1411 handler.handleSession(&sess, request) catch |session_err| { 1412 // try to send a non-zero exit status before closing 1413 sess.exit(1) catch {}; 1414 return session_err; 1415 }; 1416 if (!sess.closed) try sess.exit(0); 1417 return; 1418 } 1419 }, 1420 1421 SSH_MSG_CHANNEL_WINDOW_ADJUST => { 1422 const ch = if (channel) |*c| c else continue; 1423 try handleWindowAdjust(ch, packet); 1424 }, 1425 1426 SSH_MSG_CHANNEL_DATA, SSH_MSG_CHANNEL_EXTENDED_DATA => { 1427 const ch = if (channel) |*c| c else continue; 1428 // before shell/exec the client shouldn't be sending data, but 1429 // some clients are chatty; discard and refill window. 1430 try discardChannelData(io, allocator, sc_cipher, writer, ch, packet, msg_type == SSH_MSG_CHANNEL_EXTENDED_DATA); 1431 }, 1432 1433 SSH_MSG_CHANNEL_EOF => { 1434 if (channel) |*c| { 1435 try parseChannelId(packet, c.local_id); 1436 c.eof_received = true; 1437 } 1438 }, 1439 1440 SSH_MSG_CHANNEL_CLOSE => { 1441 if (channel) |*c| try parseChannelId(packet, c.local_id); 1442 return; 1443 }, 1444 1445 else => {}, // ignore unknown messages 1446 } 1447 } 1448 } 1449 1450 fn handleGlobalRequest( 1451 io: std.Io, 1452 allocator: std.mem.Allocator, 1453 sc_cipher: *Cipher, 1454 writer: *std.Io.Writer, 1455 packet: []const u8, 1456 ) !void { 1457 // byte SSH_MSG_GLOBAL_REQUEST 1458 // string request_name 1459 // boolean want_reply 1460 // …request-specific data we ignore 1461 var r = std.Io.Reader.fixed(packet[1..]); 1462 const name = try takeStringField(allocator, &r, 256); 1463 defer allocator.free(name); 1464 const want_reply = (try r.takeByte()) != 0; 1465 if (want_reply) { 1466 try sc_cipher.writePacket(io, allocator, writer, &[_]u8{SSH_MSG_REQUEST_FAILURE}); 1467 } 1468 } 1469 1470 /// Parse a CHANNEL_OPEN. On a session channel, send CHANNEL_OPEN_CONFIRMATION 1471 /// and return the new Channel. On other types, send CHANNEL_OPEN_FAILURE and 1472 /// return null. 1473 fn handleChannelOpen( 1474 io: std.Io, 1475 allocator: std.mem.Allocator, 1476 sc_cipher: *Cipher, 1477 writer: *std.Io.Writer, 1478 packet: []const u8, 1479 ) !?Channel { 1480 // byte SSH_MSG_CHANNEL_OPEN 1481 // string channel_type 1482 // uint32 sender_channel (peer's id) 1483 // uint32 initial_window 1484 // uint32 max_packet 1485 var r = std.Io.Reader.fixed(packet[1..]); 1486 const ch_type = try takeStringField(allocator, &r, 64); 1487 defer allocator.free(ch_type); 1488 const remote_id = try r.takeInt(u32, .big); 1489 const initial_window = try r.takeInt(u32, .big); 1490 const max_packet = try r.takeInt(u32, .big); 1491 1492 if (!std.mem.eql(u8, ch_type, "session")) { 1493 try sendChannelOpenFailure(io, allocator, sc_cipher, writer, packet, SSH_OPEN_UNKNOWN_CHANNEL_TYPE, "only session channels are supported"); 1494 return null; 1495 } 1496 1497 const local_id: u32 = 0; // single-channel connection — id is always 0 from our side 1498 var reply: std.ArrayList(u8) = .empty; 1499 defer reply.deinit(allocator); 1500 try reply.append(allocator, SSH_MSG_CHANNEL_OPEN_CONFIRMATION); 1501 try writeU32(&reply, allocator, remote_id); 1502 try writeU32(&reply, allocator, local_id); 1503 try writeU32(&reply, allocator, initial_recv_window); 1504 try writeU32(&reply, allocator, max_packet_size); 1505 try sc_cipher.writePacket(io, allocator, writer, reply.items); 1506 1507 return .{ 1508 .local_id = local_id, 1509 .remote_id = remote_id, 1510 .local_window = initial_recv_window, 1511 .remote_window = initial_window, 1512 .max_packet = max_packet, 1513 }; 1514 } 1515 1516 fn sendChannelOpenFailure( 1517 io: std.Io, 1518 allocator: std.mem.Allocator, 1519 sc_cipher: *Cipher, 1520 writer: *std.Io.Writer, 1521 open_packet: []const u8, 1522 reason: u32, 1523 description: []const u8, 1524 ) !void { 1525 // recover the sender_channel field from the CHANNEL_OPEN packet so we 1526 // address the failure to the correct id 1527 var r = std.Io.Reader.fixed(open_packet[1..]); 1528 const ch_type_len = try r.takeInt(u32, .big); 1529 try r.discardAll(ch_type_len); 1530 const remote_id = try r.takeInt(u32, .big); 1531 1532 var reply: std.ArrayList(u8) = .empty; 1533 defer reply.deinit(allocator); 1534 try reply.append(allocator, SSH_MSG_CHANNEL_OPEN_FAILURE); 1535 try writeU32(&reply, allocator, remote_id); 1536 try writeU32(&reply, allocator, reason); 1537 try writeStringField(&reply, allocator, description); 1538 try writeStringField(&reply, allocator, ""); // language tag 1539 try sc_cipher.writePacket(io, allocator, writer, reply.items); 1540 } 1541 1542 const RequestKind = enum { shell, exec }; 1543 1544 /// Returns the kind of session request if this triggered one, else null. 1545 fn handleChannelRequest( 1546 io: std.Io, 1547 allocator: std.mem.Allocator, 1548 sc_cipher: *Cipher, 1549 writer: *std.Io.Writer, 1550 ch: *Channel, 1551 packet: []const u8, 1552 pending_exec: *?[]u8, 1553 ) !?RequestKind { 1554 // byte SSH_MSG_CHANNEL_REQUEST 1555 // uint32 recipient_channel (== our local_id) 1556 // string request_type 1557 // boolean want_reply 1558 // …request-specific data 1559 var r = std.Io.Reader.fixed(packet[1..]); 1560 const recipient_channel = try r.takeInt(u32, .big); 1561 if (recipient_channel != ch.local_id) return error.UnknownChannel; 1562 const req_type = try takeStringField(allocator, &r, 64); 1563 defer allocator.free(req_type); 1564 const want_reply = (try r.takeByte()) != 0; 1565 1566 if (std.mem.eql(u8, req_type, "pty-req")) { 1567 // string TERM, uint32 width chars, uint32 height rows, uint32 width px, 1568 // uint32 height px, string modes 1569 const term = try takeStringField(allocator, &r, 64); 1570 defer allocator.free(term); 1571 const width = try r.takeInt(u32, .big); 1572 const height = try r.takeInt(u32, .big); 1573 ch.pty = .{ .width_cells = @intCast(@min(width, 0xFFFF)), .height_cells = @intCast(@min(height, 0xFFFF)) }; 1574 try replyChannelRequest(io, allocator, sc_cipher, writer, ch, want_reply, true); 1575 return null; 1576 } 1577 1578 if (std.mem.eql(u8, req_type, "env")) { 1579 // ignore environment variables silently (we don't pass them anywhere) 1580 try replyChannelRequest(io, allocator, sc_cipher, writer, ch, want_reply, true); 1581 return null; 1582 } 1583 1584 if (std.mem.eql(u8, req_type, "window-change")) { 1585 // uint32 width cells, uint32 height rows, uint32 width px, uint32 height px 1586 const width = try r.takeInt(u32, .big); 1587 const height = try r.takeInt(u32, .big); 1588 if (ch.pty != null) { 1589 ch.pty = .{ .width_cells = @intCast(@min(width, 0xFFFF)), .height_cells = @intCast(@min(height, 0xFFFF)) }; 1590 } 1591 // spec: window-change MUST NOT request a reply, but accept either 1592 try replyChannelRequest(io, allocator, sc_cipher, writer, ch, want_reply, true); 1593 return null; 1594 } 1595 1596 if (std.mem.eql(u8, req_type, "shell")) { 1597 try replyChannelRequest(io, allocator, sc_cipher, writer, ch, want_reply, true); 1598 return .shell; 1599 } 1600 1601 if (std.mem.eql(u8, req_type, "exec")) { 1602 // capture the command string for the handler to inspect 1603 const cmd = try takeStringField(allocator, &r, 4096); 1604 if (pending_exec.*) |old| allocator.free(old); 1605 pending_exec.* = cmd; 1606 try replyChannelRequest(io, allocator, sc_cipher, writer, ch, want_reply, true); 1607 return .exec; 1608 } 1609 1610 // unknown request kind — fail it 1611 try replyChannelRequest(io, allocator, sc_cipher, writer, ch, want_reply, false); 1612 return null; 1613 } 1614 1615 fn replyChannelRequest( 1616 io: std.Io, 1617 allocator: std.mem.Allocator, 1618 sc_cipher: *Cipher, 1619 writer: *std.Io.Writer, 1620 ch: *Channel, 1621 want_reply: bool, 1622 success: bool, 1623 ) !void { 1624 if (!want_reply) return; 1625 var reply: std.ArrayList(u8) = .empty; 1626 defer reply.deinit(allocator); 1627 try reply.append(allocator, if (success) SSH_MSG_CHANNEL_SUCCESS else SSH_MSG_CHANNEL_FAILURE); 1628 try writeU32(&reply, allocator, ch.remote_id); 1629 try sc_cipher.writePacket(io, allocator, writer, reply.items); 1630 } 1631 1632 fn handleWindowAdjust(ch: *Channel, packet: []const u8) !void { 1633 // byte SSH_MSG_CHANNEL_WINDOW_ADJUST 1634 // uint32 recipient_channel 1635 // uint32 bytes_to_add 1636 var r = std.Io.Reader.fixed(packet[1..]); 1637 const recipient_channel = try r.takeInt(u32, .big); 1638 if (recipient_channel != ch.local_id) return error.UnknownChannel; 1639 const add = try r.takeInt(u32, .big); 1640 ch.remote_window +|= add; 1641 } 1642 1643 fn discardChannelData( 1644 io: std.Io, 1645 allocator: std.mem.Allocator, 1646 sc_cipher: *Cipher, 1647 writer: *std.Io.Writer, 1648 ch: *Channel, 1649 packet: []const u8, 1650 extended: bool, 1651 ) !void { 1652 // byte SSH_MSG_CHANNEL_DATA/EXTENDED_DATA 1653 // uint32 recipient_channel 1654 // [if extended: uint32 type_code] 1655 // string data 1656 const payload = try parseChannelData(packet, extended, ch.local_id); 1657 const data_len: u32 = @intCast(payload.len); 1658 1659 if (data_len > ch.local_window) return error.WindowExceeded; 1660 ch.local_window -= data_len; 1661 try maybeRefillRecvWindow(io, allocator, sc_cipher, writer, ch); 1662 } 1663 1664 pub fn parseChannelData(packet: []const u8, extended: bool, expected_channel: u32) ![]const u8 { 1665 if (packet.len < 1) return error.EmptyPacket; 1666 var r = std.Io.Reader.fixed(packet[1..]); 1667 const recipient_channel = try r.takeInt(u32, .big); 1668 if (recipient_channel != expected_channel) return error.UnknownChannel; 1669 if (extended) { 1670 const data_type = try r.takeInt(u32, .big); 1671 if (data_type != SSH_EXTENDED_DATA_STDERR) return error.UnsupportedExtendedData; 1672 } 1673 const data_len = try r.takeInt(u32, .big); 1674 // catches both data_len > remaining (would otherwise be a bounds-check 1675 // panic on the slice) and trailing junk after the declared payload. 1676 if (data_len != r.buffered().len) return error.InvalidChannelData; 1677 return r.buffered(); 1678 } 1679 1680 fn parseChannelId(packet: []const u8, expected_channel: u32) !void { 1681 if (packet.len < 1) return error.EmptyPacket; 1682 var r = std.Io.Reader.fixed(packet[1..]); 1683 const recipient_channel = try r.takeInt(u32, .big); 1684 if (recipient_channel != expected_channel) return error.UnknownChannel; 1685 if (r.buffered().len != 0) return error.InvalidChannelMessage; 1686 } 1687 1688 /// Send a CHANNEL_WINDOW_ADJUST if our receive window has dipped below half 1689 /// of the initial value. Used both for the pre-session discard path and by 1690 /// SessionCtx after it consumes a CHANNEL_DATA payload. 1691 fn maybeRefillRecvWindow( 1692 io: std.Io, 1693 allocator: std.mem.Allocator, 1694 sc_cipher: *Cipher, 1695 writer: *std.Io.Writer, 1696 ch: *Channel, 1697 ) !void { 1698 if (ch.local_window >= initial_recv_window / 2) return; 1699 const add = initial_recv_window - ch.local_window; 1700 ch.local_window += add; 1701 var adj: std.ArrayList(u8) = .empty; 1702 defer adj.deinit(allocator); 1703 try adj.append(allocator, SSH_MSG_CHANNEL_WINDOW_ADJUST); 1704 try writeU32(&adj, allocator, ch.remote_id); 1705 try writeU32(&adj, allocator, add); 1706 try sc_cipher.writePacket(io, allocator, writer, adj.items); 1707 } 1708 1709 fn writeU32(buf: *std.ArrayList(u8), allocator: std.mem.Allocator, value: u32) !void { 1710 var bytes: [4]u8 = undefined; 1711 std.mem.writeInt(u32, &bytes, value, .big); 1712 try buf.appendSlice(allocator, &bytes); 1713 } 1714