Public Access
jaap-jan
b20f7cae04
The relay checkbox said it was not wired up, and the plan said the server half was built and shipped. It was not: there was ADR 0004, the contract records, RelayOptions and a CHECK constraint, and RelayOptions said in its own remarks that there was no endpoint and no dialler. So both halves are built here, as step 3 of docs/reaching-a-host-you-cannot-dial.md. Server, in Features/Relay: - POST /api/v1/relay/tickets makes every decision: the host, Connect on its vault, the relay switched on, and the stored name resolved once and judged by RelayAddressPolicy. Loopback, link-local, 0.0.0.0/8, multicast and the metadata endpoints are refused with no configuration escape, with IPv4-mapped and NAT64 spellings unwrapped first; then the operator's denials, allow-list and private-network switch. What passes goes into a Data Protection ticket, and nothing resolves the name again. Every target refusal is the same 403, so the endpoint cannot be used to map the operator's DNS; the real reason is logged. - GET /api/v1/relay/connect takes the ticket as a second subprotocol, checks its expiry against TimeProvider and spends it with a unique insert into relay_ticket_use before accepting the upgrade. After the upgrade a refusal is a close code: 4502 for a host the server could not reach, 4429 for a limit, 4408 idle, 4409 lifetime, 1001 after a drain. - relay_session is the audit row, written from short-lived scopes. Client: - RelayBridge is a loopback SOCKS5 listener that accepts once and pipes to the relay socket. It rides on the new SshLoopbackProxy.Lifetime, so the connection disposes it on every way a session ends and a failed connect disposes it before throwing. - ServerRelay, exposed as IVaultServer.Relay from /api/v1/meta, asks for the ticket, opens the socket, starts the bridge and turns every refusal into a sentence. - VaultViewModel and TransfersViewModel reach a relayed host through it, never fall back to dialling it directly, and replace SSH.NET's transport error with the relay's own reason when it gave one. Neither side ever cancels a WebSocket operation. Cancelling one aborts the socket, and an aborted socket sends no close frame, which is the only way the client learns the server could not reach the host. AnIdleSession_IsClosedWithTheIdleCode asserts that the code arrives. Three departures from ADR 0004, recorded in it: awaited copy loops rather than Pipelines (same backpressure, two 32 KiB buffers), no ?ticket= fallback, and no device id in the ticket. Tests: API 245, shell 582 (5 skipped), layout 170, SSH 110 including a real login through the bridge, API client 30, contracts 25. Not run: the Android build (its change is copy only) and the Alpine layout oracle.
62 lines
2.4 KiB
C#
62 lines
2.4 KiB
C#
using System.Net;
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using System.Net.Sockets;
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namespace DodoSSH.Api.Features.Relay;
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/// <summary>
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/// The two things the relay asks of the network: what a name resolves to, and a connection to an address.
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/// </summary>
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/// <remarks>
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/// <para>
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/// A seam for tests, and a narrow one on purpose. <see cref="RelayAddressPolicy"/> is not behind it:
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/// whatever this answers, the policy judges, and a test that replaces this still runs every address
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/// through the real rules. What a test cannot do without the seam is dial anything, because every
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/// address a test machine can reach on its own — loopback — is one the policy refuses outright.
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/// </para>
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/// </remarks>
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internal interface IRelayNetwork
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{
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/// <summary>Resolves a stored hostname, which may be an address literal.</summary>
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Task<IPAddress[]> ResolveAsync(string host, CancellationToken cancellationToken);
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/// <summary>Opens a TCP connection to one address.</summary>
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/// <returns>A stream that owns the connection.</returns>
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Task<Stream> ConnectAsync(IPAddress address, int port, CancellationToken cancellationToken);
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}
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/// <summary>The operating system's resolver and sockets.</summary>
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internal sealed class SystemRelayNetwork : IRelayNetwork
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{
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/// <inheritdoc />
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public Task<IPAddress[]> ResolveAsync(string host, CancellationToken cancellationToken) =>
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// A literal parses to itself without a lookup, which is what an address typed into a host
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// editor should do — and what makes "10.0.0.5" mean the same thing on every node.
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IPAddress.TryParse(host, out var literal)
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? Task.FromResult<IPAddress[]>([literal])
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: Dns.GetHostAddressesAsync(host, cancellationToken);
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/// <inheritdoc />
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public async Task<Stream> ConnectAsync(IPAddress address, int port, CancellationToken cancellationToken)
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{
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var socket = new Socket(address.AddressFamily, SocketType.Stream, ProtocolType.Tcp)
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{
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// An interactive shell is a stream of keystrokes; Nagle would hold each one back for the
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// acknowledgement of the last, which is the latency the user feels as a sticky terminal.
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NoDelay = true,
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};
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try
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{
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await socket.ConnectAsync(new IPEndPoint(address, port), cancellationToken).ConfigureAwait(false);
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return new NetworkStream(socket, ownsSocket: true);
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}
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catch
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{
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socket.Dispose();
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throw;
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}
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}
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}
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