╭─────────────╮ │scroll to top│ ╰─────────────╯ ╭ serve_ssh_protocol.zig ───────────────────────────────────────╮ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ ╰───────────────────────────────────────────────────────────────╯
🬐 🬠 🬞🬂🬏 🬟 🬑 🬟 🬑 ╭dc4d0b37..╮ dc4d0b37.. see-em: 🬋🬋🬋 🬋🬋🬋 🬋 🬋 │files │ commits refs discuss issues new login 🬐 🬠 🬐 🬠 🬑 🬟 🬰 ╰──────────╯ (246) user
╭────╮ ╭ clone ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ╮ │http│ ssh │ │ ╰────╯ ╰ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ╯
.. embed/ event/ test/ ui/ command.zig event.zig lib.zig main.zig main_wasm.zig serve.zig serve_common.zig serve_http.zig serve_ssh.zig ╭─────────────────────────────────╮ │serve_ssh_protocol.zig │ ╰─────────────────────────────────╯ test.zig testnet.zig try.zig ui.zig web.zig
1517 ) catch false; 1518 1519 if (!ok) { 1520 auth_attempts += 1; 1521 if (auth_attempts >= max_auth_attempts) return error.TooManyAuthAttempts; 1522 try sendUserauthFailure(io, allocator, sc_cipher, writer); 1523 continue; 1524 } 1525 1526 try sc_cipher.writePacket(io, allocator, writer, &[_]u8{SSH_MSG_USERAUTH_SUCCESS}); 1527 return formatFingerprint(pubkey_blob); 1528 } 1529 } 1530 1531 fn sendUserauthFailure( 1532 io: std.Io, 1533 allocator: std.mem.Allocator, 1534 sc_cipher: *Cipher, 1535 writer: *std.Io.Writer, 1536 ) !void { 1537 var buf: std.ArrayList(u8) = .empty; 1538 defer buf.deinit(allocator); 1539 try buf.append(allocator, SSH_MSG_USERAUTH_FAILURE); 1540 try writeNameList(&buf, allocator, &.{"publickey"}); // allowed methods 1541 try buf.append(allocator, 0); // partial_success = false 1542 try sc_cipher.writePacket(io, allocator, writer, buf.items); 1543 } 1544 1545 /// Append the canonical publickey-signed-data bytes (RFC 4252 §7) to `buf`. 1546 /// Used by the server to recompute the signed input for verification 1547 pub fn appendPublickeySignedData( 1548 buf: *std.ArrayList(u8), 1549 allocator: std.mem.Allocator, 1550 session_id: []const u8, 1551 user_name: []const u8, 1552 service_name: []const u8, 1553 algo: []const u8, 1554 pubkey_blob: []const u8, 1555 ) !void { 1556 try writeStringField(buf, allocator, session_id); 1557 try buf.append(allocator, SSH_MSG_USERAUTH_REQUEST); 1558 try writeStringField(buf, allocator, user_name); 1559 try writeStringField(buf, allocator, service_name); 1560 try writeStringField(buf, allocator, "publickey"); 1561 try buf.append(allocator, 1); 1562 try writeStringField(buf, allocator, algo); 1563 try writeStringField(buf, allocator, pubkey_blob); 1564 } 1565 1566 // build the bytes a publickey signature is computed over (RFC 4252 §7) and 1567 // verify the supplied signature against them. 1568 fn verifyUserauthSignature( 1569 allocator: std.mem.Allocator, 1570 session_id: *const [Sha256.digest_length]u8, 1571 user_name: []const u8, 1572 service_name: []const u8, 1573 algo: []const u8, 1574 pubkey_blob: []const u8, 1575 signature_blob: []const u8, 1576 ) !bool { 1577 var signed: std.ArrayList(u8) = .empty; 1578 defer signed.deinit(allocator); 1579 try appendPublickeySignedData(&signed, allocator, session_id, user_name, service_name, algo, pubkey_blob); 1580 1581 // parse pubkey_blob: string "ssh-ed25519" || string raw_pubkey 1582 var pubkey_reader = std.Io.Reader.fixed(pubkey_blob); 1583 const pk_algo = try takeStringField(allocator, &pubkey_reader, 64); 1584 defer allocator.free(pk_algo); 1585 if (!std.mem.eql(u8, pk_algo, "ssh-ed25519")) return false; 1586 const raw_pubkey = try takeStringField(allocator, &pubkey_reader, 64); 1587 defer allocator.free(raw_pubkey); 1588 if (raw_pubkey.len != Ed25519.PublicKey.encoded_length) return false; 1589 1590 // parse signature_blob: string "ssh-ed25519" || string raw_signature 1591 var sig_reader = std.Io.Reader.fixed(signature_blob); 1592 const sig_algo = try takeStringField(allocator, &sig_reader, 64); 1593 defer allocator.free(sig_algo); 1594 if (!std.mem.eql(u8, sig_algo, "ssh-ed25519")) return false; 1595 const raw_sig = try takeStringField(allocator, &sig_reader, Ed25519.Signature.encoded_length); 1596 defer allocator.free(raw_sig); 1597 if (raw_sig.len != Ed25519.Signature.encoded_length) return false; 1598 1599 var pubkey_bytes: [Ed25519.PublicKey.encoded_length]u8 = undefined; 1600 @memcpy(&pubkey_bytes, raw_pubkey); 1601 var sig_bytes: [Ed25519.Signature.encoded_length]u8 = undefined; 1602 @memcpy(&sig_bytes, raw_sig); 1603 1604 const pk = Ed25519.PublicKey.fromBytes(pubkey_bytes) catch return false; 1605 const sig = Ed25519.Signature.fromBytes(sig_bytes); 1606 sig.verify(signed.items, pk) catch return false; 1607 return true; 1608 } 1609 1610 // --------------------------------------------------------------------------- 1611 // connection layer (RFC 4254): channels, requests, data, flow control 1612 // --------------------------------------------------------------------------- 1613 1614 const Channel = struct { 1615 local_id: u32, 1616 remote_id: u32, 1617 local_window: u32, // bytes peer may still send us before we adjust 1618 remote_window: u32, // bytes we may still send to peer before they adjust 1619 max_packet: u32, // max CHANNEL_DATA payload the peer accepts in one packet 1620 pty: ?PtySize = null, 1621 }; 1622 1623 pub const PtySize = struct { width_cells: u16, height_cells: u16 }; 1624 1625 // take the uint32 width/height cell counts of a pty-req or window-change, 1626 // clamped to u16 1627 fn takePtySize(r: *std.Io.Reader) !PtySize { 1628 const width = try r.takeInt(u32, .big); 1629 const height = try r.takeInt(u32, .big); 1630 return .{ 1631 .width_cells = @intCast(@min(width, 0xFFFF)), 1632 .height_cells = @intCast(@min(height, 0xFFFF)), 1633 }; 1634 } 1635 1636 fn runChannelLayer( 1637 io: std.Io, 1638 allocator: std.mem.Allocator, 1639 reader: *std.Io.Reader, 1640 writer: *std.Io.Writer, 1641 cs_cipher: *Cipher, 1642 sc_cipher: *Cipher, 1643 rekey: *const RekeyState, 1644 fingerprint: *const [fingerprint_len]u8, 1645 handler: anytype, 1646 ) !void { 1647 var channel: ?Channel = null; 1648 var pending_exec: ?[]u8 = null; 1649 defer if (pending_exec) |s| allocator.free(s); 1650 1651 while (true) { 1652 const packet = try readSessionPacket(io, allocator, reader, writer, cs_cipher, sc_cipher, rekey); 1653 defer allocator.free(packet); 1654 if (packet.len < 1) return error.EmptyPacket; 1655 const msg_type = packet[0]; 1656 1657 switch (msg_type) { 1658 SSH_MSG_GLOBAL_REQUEST => try handleGlobalRequest(io, allocator, sc_cipher, writer, packet), 1659 1660 SSH_MSG_CHANNEL_OPEN => { 1661 if (channel != null) { 1662 try sendChannelOpenFailure(io, allocator, sc_cipher, writer, packet, SSH_OPEN_RESOURCE_SHORTAGE, "only one channel per connection"); 1663 continue; 1664 } 1665 channel = try handleChannelOpen(io, allocator, sc_cipher, writer, packet) orelse continue; 1666 }, 1667 1668 SSH_MSG_CHANNEL_REQUEST => { 1669 const ch = if (channel) |*c| c else continue; 1670 const start_request = try handleChannelRequest(io, allocator, sc_cipher, writer, ch, packet, &pending_exec); 1671 if (start_request) |req_kind| { 1672 const request: Request = switch (req_kind) { 1673 .shell => .{ .shell = ch.pty }, 1674 .exec => .{ .exec = pending_exec.? }, 1675 }; 1676 var sess = SessionCtx{ 1677 .io = io, 1678 .allocator = allocator, 1679 .reader = reader, 1680 .writer = writer, 1681 .cs_cipher = cs_cipher, 1682 .sc_cipher = sc_cipher, 1683 .rekey = rekey, 1684 .channel = ch, 1685 .fingerprint = fingerprint.*, 1686 }; 1687 defer sess.deinit(); 1688 handler.handleSession(&sess, request) catch |session_err| { 1689 // try to send a non-zero exit status before closing 1690 sess.exit(1) catch {}; 1691 return session_err; 1692 }; 1693 if (!sess.closed) try sess.exit(0); 1694 return; 1695 } 1696 }, 1697 1698 SSH_MSG_CHANNEL_WINDOW_ADJUST => { 1699 const ch = if (channel) |*c| c else continue; 1700 try handleWindowAdjust(ch, packet); 1701 }, 1702 1703 SSH_MSG_CHANNEL_DATA, SSH_MSG_CHANNEL_EXTENDED_DATA => { 1704 const ch = if (channel) |*c| c else continue; 1705 // before shell/exec the client shouldn't be sending data, but 1706 // some clients are chatty; discard and refill window. 1707 try discardChannelData(io, allocator, sc_cipher, writer, ch, packet, msg_type == SSH_MSG_CHANNEL_EXTENDED_DATA); 1708 }, 1709 1710 SSH_MSG_CHANNEL_EOF => { 1711 if (channel) |*c| try parseChannelId(packet, c.local_id); 1712 }, 1713 1714 SSH_MSG_CHANNEL_CLOSE => { 1715 if (channel) |*c| try parseChannelId(packet, c.local_id); 1716 return; 1717 }, 1718 1719 else => {}, // ignore unknown messages 1720 } 1721 } 1722 } 1723 1724 fn handleGlobalRequest( 1725 io: std.Io, 1726 allocator: std.mem.Allocator, 1727 sc_cipher: *Cipher, 1728 writer: *std.Io.Writer, 1729 packet: []const u8, 1730 ) !void { 1731 // byte SSH_MSG_GLOBAL_REQUEST 1732 // string request_name 1733 // boolean want_reply 1734 // …request-specific data we ignore 1735 var r = std.Io.Reader.fixed(packet[1..]); 1736 const name = try takeStringField(allocator, &r, 256); 1737 defer allocator.free(name); 1738 const want_reply = (try r.takeByte()) != 0; 1739 if (want_reply) { 1740 try sc_cipher.writePacket(io, allocator, writer, &[_]u8{SSH_MSG_REQUEST_FAILURE}); 1741 } 1742 } 1743 1744 /// Parse a CHANNEL_OPEN. On a session channel, send CHANNEL_OPEN_CONFIRMATION 1745 /// and return the new Channel. On other types, send CHANNEL_OPEN_FAILURE and 1746 /// return null. 1747 fn handleChannelOpen( 1748 io: std.Io, 1749 allocator: std.mem.Allocator, 1750 sc_cipher: *Cipher, 1751 writer: *std.Io.Writer, 1752 packet: []const u8, 1753 ) !?Channel { 1754 // byte SSH_MSG_CHANNEL_OPEN 1755 // string channel_type 1756 // uint32 sender_channel (peer's id) 1757 // uint32 initial_window 1758 // uint32 max_packet 1759 var r = std.Io.Reader.fixed(packet[1..]); 1760 const ch_type = try takeStringField(allocator, &r, 64); 1761 defer allocator.free(ch_type); 1762 const remote_id = try r.takeInt(u32, .big); 1763 const initial_window = try r.takeInt(u32, .big); 1764 const max_packet = try r.takeInt(u32, .big); 1765 1766 if (!std.mem.eql(u8, ch_type, "session")) { 1767 try sendChannelOpenFailure(io, allocator, sc_cipher, writer, packet, SSH_OPEN_UNKNOWN_CHANNEL_TYPE, "only session channels are supported"); 1768 return null; 1769 } 1770 1771 // a zero max_packet would leave writeChannel looping without progress 1772 if (max_packet == 0) { 1773 try sendChannelOpenFailure(io, allocator, sc_cipher, writer, packet, SSH_OPEN_RESOURCE_SHORTAGE, "max packet size must be non-zero"); 1774 return null; 1775 } 1776 1777 const local_id: u32 = 0; // single-channel connection — id is always 0 from our side 1778 var reply: std.ArrayList(u8) = .empty; 1779 defer reply.deinit(allocator); 1780 try reply.append(allocator, SSH_MSG_CHANNEL_OPEN_CONFIRMATION); 1781 try writeU32(&reply, allocator, remote_id); 1782 try writeU32(&reply, allocator, local_id); 1783 try writeU32(&reply, allocator, initial_recv_window); 1784 try writeU32(&reply, allocator, max_packet_size); 1785 try sc_cipher.writePacket(io, allocator, writer, reply.items); 1786 1787 return .{ 1788 .local_id = local_id, 1789 .remote_id = remote_id, 1790 .local_window = initial_recv_window, 1791 .remote_window = initial_window, 1792 .max_packet = max_packet, 1793 }; 1794 } 1795 1796 fn sendChannelOpenFailure( 1797 io: std.Io, 1798 allocator: std.mem.Allocator, 1799 sc_cipher: *Cipher, 1800 writer: *std.Io.Writer, 1801 open_packet: []const u8, 1802 reason: u32, 1803 description: []const u8, 1804 ) !void { 1805 // recover the sender_channel field from the CHANNEL_OPEN packet so we 1806 // address the failure to the correct id 1807 var r = std.Io.Reader.fixed(open_packet[1..]); 1808 const ch_type_len = try r.takeInt(u32, .big); 1809 try r.discardAll(ch_type_len); 1810 const remote_id = try r.takeInt(u32, .big); 1811 1812 var reply: std.ArrayList(u8) = .empty; 1813 defer reply.deinit(allocator); 1814 try reply.append(allocator, SSH_MSG_CHANNEL_OPEN_FAILURE); 1815 try writeU32(&reply, allocator, remote_id); 1816 try writeU32(&reply, allocator, reason); 1817 try writeStringField(&reply, allocator, description); 1818 try writeStringField(&reply, allocator, ""); // language tag 1819 try sc_cipher.writePacket(io, allocator, writer, reply.items); 1820 } 1821 1822 const RequestKind = enum { shell, exec }; 1823 1824 /// Returns the kind of session request if this triggered one, else null. 1825 fn handleChannelRequest( 1826 io: std.Io, 1827 allocator: std.mem.Allocator, 1828 sc_cipher: *Cipher, 1829 writer: *std.Io.Writer, 1830 ch: *Channel, 1831 packet: []const u8, 1832 pending_exec: *?[]u8, 1833 ) !?RequestKind { 1834 // byte SSH_MSG_CHANNEL_REQUEST 1835 // uint32 recipient_channel (== our local_id) 1836 // string request_type 1837 // boolean want_reply 1838 // …request-specific data 1839 var r = std.Io.Reader.fixed(packet[1..]); 1840 const recipient_channel = try r.takeInt(u32, .big); 1841 if (recipient_channel != ch.local_id) return error.UnknownChannel; 1842 const req_type = try takeStringField(allocator, &r, 64); 1843 defer allocator.free(req_type); 1844 const want_reply = (try r.takeByte()) != 0; 1845 1846 if (std.mem.eql(u8, req_type, "pty-req")) { 1847 // string TERM, uint32 width chars, uint32 height rows, uint32 width px, 1848 // uint32 height px, string modes 1849 const term = try takeStringField(allocator, &r, 64); 1850 defer allocator.free(term); 1851 ch.pty = try takePtySize(&r); 1852 try replyChannelRequest(io, allocator, sc_cipher, writer, ch, want_reply, true); 1853 return null; 1854 } 1855 1856 if (std.mem.eql(u8, req_type, "env")) { 1857 // ignore environment variables silently (we don't pass them anywhere) 1858 try replyChannelRequest(io, allocator, sc_cipher, writer, ch, want_reply, true); 1859 return null; 1860 } 1861 1862 if (std.mem.eql(u8, req_type, "window-change")) { 1863 // uint32 width cells, uint32 height rows, uint32 width px, uint32 height px 1864 const sz = try takePtySize(&r); 1865 if (ch.pty != null) ch.pty = sz; 1866 // spec: window-change MUST NOT request a reply, but accept either 1867 try replyChannelRequest(io, allocator, sc_cipher, writer, ch, want_reply, true); 1868 return null; 1869 } 1870 1871 if (std.mem.eql(u8, req_type, "shell")) { 1872 try replyChannelRequest(io, allocator, sc_cipher, writer, ch, want_reply, true); 1873 return .shell; 1874 } 1875 1876 if (std.mem.eql(u8, req_type, "exec")) { 1877 // capture the command string for the handler to inspect 1878 const cmd = try takeStringField(allocator, &r, 4096); 1879 if (pending_exec.*) |old| allocator.free(old); 1880 pending_exec.* = cmd; 1881 try replyChannelRequest(io, allocator, sc_cipher, writer, ch, want_reply, true); 1882 return .exec; 1883 } 1884 1885 // unknown request kind — fail it 1886 try replyChannelRequest(io, allocator, sc_cipher, writer, ch, want_reply, false); 1887 return null; 1888 } 1889 1890 fn replyChannelRequest( 1891 io: std.Io, 1892 allocator: std.mem.Allocator, 1893 sc_cipher: *Cipher, 1894 writer: *std.Io.Writer, 1895 ch: *Channel, 1896 want_reply: bool, 1897 success: bool, 1898 ) !void { 1899 if (!want_reply) return; 1900 var reply: std.ArrayList(u8) = .empty; 1901 defer reply.deinit(allocator); 1902 try reply.append(allocator, if (success) SSH_MSG_CHANNEL_SUCCESS else SSH_MSG_CHANNEL_FAILURE); 1903 try writeU32(&reply, allocator, ch.remote_id); 1904 try sc_cipher.writePacket(io, allocator, writer, reply.items); 1905 } 1906 1907 fn handleWindowAdjust(ch: *Channel, packet: []const u8) !void { 1908 // byte SSH_MSG_CHANNEL_WINDOW_ADJUST 1909 // uint32 recipient_channel 1910 // uint32 bytes_to_add 1911 var r = std.Io.Reader.fixed(packet[1..]); 1912 const recipient_channel = try r.takeInt(u32, .big); 1913 if (recipient_channel != ch.local_id) return error.UnknownChannel; 1914 const add = try r.takeInt(u32, .big); 1915 ch.remote_window +|= add; 1916 } 1917 1918 fn discardChannelData( 1919 io: std.Io, 1920 allocator: std.mem.Allocator, 1921 sc_cipher: *Cipher, 1922 writer: *std.Io.Writer, 1923 ch: *Channel, 1924 packet: []const u8, 1925 extended: bool, 1926 ) !void { 1927 // byte SSH_MSG_CHANNEL_DATA/EXTENDED_DATA 1928 // uint32 recipient_channel 1929 // [if extended: uint32 type_code] 1930 // string data 1931 const payload = try parseChannelData(packet, extended, ch.local_id); 1932 const data_len: u32 = @intCast(payload.len); 1933 1934 if (data_len > ch.local_window) return error.WindowExceeded; 1935 ch.local_window -= data_len; 1936 try maybeRefillRecvWindow(io, allocator, sc_cipher, writer, ch); 1937 } 1938 1939 pub fn parseChannelData(packet: []const u8, extended: bool, expected_channel: u32) ![]const u8 { 1940 if (packet.len < 1) return error.EmptyPacket; 1941 var r = std.Io.Reader.fixed(packet[1..]); 1942 const recipient_channel = try r.takeInt(u32, .big); 1943 if (recipient_channel != expected_channel) return error.UnknownChannel; 1944 if (extended) { 1945 const data_type = try r.takeInt(u32, .big); 1946 if (data_type != SSH_EXTENDED_DATA_STDERR) return error.UnsupportedExtendedData; 1947 } 1948 const data_len = try r.takeInt(u32, .big); 1949 // catches both data_len > remaining (would otherwise be a bounds-check 1950 // panic on the slice) and trailing junk after the declared payload. 1951 if (data_len != r.buffered().len) return error.InvalidChannelData; 1952 return r.buffered(); 1953 } 1954 1955 fn parseChannelId(packet: []const u8, expected_channel: u32) !void { 1956 if (packet.len < 1) return error.EmptyPacket; 1957 var r = std.Io.Reader.fixed(packet[1..]); 1958 const recipient_channel = try r.takeInt(u32, .big); 1959 if (recipient_channel != expected_channel) return error.UnknownChannel; 1960 if (r.buffered().len != 0) return error.InvalidChannelMessage; 1961 } 1962 1963 /// Send a CHANNEL_WINDOW_ADJUST if our receive window has dipped below half 1964 /// of the initial value. Used both for the pre-session discard path and by 1965 /// SessionCtx after it consumes a CHANNEL_DATA payload. 1966 fn maybeRefillRecvWindow( 1967 io: std.Io, 1968 allocator: std.mem.Allocator, 1969 sc_cipher: *Cipher, 1970 writer: *std.Io.Writer, 1971 ch: *Channel, 1972 ) !void { 1973 if (ch.local_window >= initial_recv_window / 2) return; 1974 const add = initial_recv_window - ch.local_window; 1975 ch.local_window += add; 1976 var adj: std.ArrayList(u8) = .empty; 1977 defer adj.deinit(allocator); 1978 try adj.append(allocator, SSH_MSG_CHANNEL_WINDOW_ADJUST); 1979 try writeU32(&adj, allocator, ch.remote_id); 1980 try writeU32(&adj, allocator, add); 1981 try sc_cipher.writePacket(io, allocator, writer, adj.items); 1982 } 1983 1984 pub fn writeU32(buf: *std.ArrayList(u8), allocator: std.mem.Allocator, value: u32) !void { 1985 var bytes: [4]u8 = undefined; 1986 std.mem.writeInt(u32, &bytes, value, .big); 1987 try buf.appendSlice(allocator, &bytes); 1988 } 1989