liminal_cli/
seat.rs

1//! AGT-006 R3: a seat names the central services by default, `liminal seat
2//! init` writes them, and a seat on an unanswering loopback address is
3//! refused by name before the MCP handshake.
4
5use std::fs::OpenOptions;
6use std::io::Write;
7use std::net::{SocketAddr, TcpStream, ToSocketAddrs};
8use std::os::unix::fs::OpenOptionsExt;
9use std::path::Path;
10use std::time::Duration;
11
12/// The central exchange's WebSocket door (AGT-006 R1).
13pub const CENTRAL_SERVER: &str = "wss://liminal.ablative.com.au/ws";
14
15/// The central Lys.
16pub const CENTRAL_ISSUER: &str = "https://lys.ablative.com.au";
17
18/// The channel a new seat's routed requests travel on.
19const DEFAULT_CHANNEL: &str = "console.topology";
20
21/// Why `liminal seat init` wrote nothing.
22#[derive(Debug, thiserror::Error)]
23pub enum SeatInitError {
24    /// The agent id is empty or is not one line of printable characters.
25    #[error("liminal_seat_agent_invalid: the agent id must be one line of printable characters")]
26    Agent,
27    /// The key file path cannot be written into the seat as text.
28    #[error("liminal_seat_key_file_invalid: {0} is not a UTF-8 path")]
29    KeyFile(String),
30    /// The open exchange address is empty or is not one line of printable characters.
31    #[error("liminal_seat_server_invalid: the server must be one line of printable characters")]
32    Server,
33    /// The seat file exists or cannot be created; it is never overwritten.
34    #[error("liminal_seat_unwritable: {path}: {message}")]
35    Unwritable {
36        /// The seat file asked for.
37        path: String,
38        /// The operating system's words.
39        message: String,
40    },
41}
42
43/// Writes a seat file at `out`, mode 0600, naming the central exchange and
44/// Lys, the agent and its key file, and never a pass. An existing file is
45/// refused, never replaced.
46///
47/// # Errors
48/// An invalid agent id or key path, or a file that exists or cannot be made.
49pub fn init(agent: &str, key_file: &Path, out: &Path) -> Result<(), SeatInitError> {
50    if agent.is_empty()
51        || agent
52            .chars()
53            .any(|c| c.is_control() || c == '"' || c == '\\')
54    {
55        return Err(SeatInitError::Agent);
56    }
57    let key = key_file
58        .to_str()
59        .filter(|k| !k.chars().any(|c| c.is_control() || c == '"' || c == '\\'))
60        .ok_or_else(|| SeatInitError::KeyFile(key_file.display().to_string()))?;
61    let text = format!(
62        "# Written by liminal seat init (AGT-006 R3): the central exchange and Lys.\n\
63         server = \"{CENTRAL_SERVER}\"\n\
64         channel = \"{DEFAULT_CHANNEL}\"\n\
65         \n\
66         [lys]\n\
67         issuer = \"{CENTRAL_ISSUER}\"\n\
68         agent = \"{agent}\"\n\
69         key_file = \"{key}\"\n\
70         \n\
71         [limits]\n\
72         frame_bytes = 65536\n\
73         record_bytes = 1048576\n\
74         reply_timeout_ms = 10000\n\
75         flow_steps = 8\n\
76         request_bytes = 65536\n"
77    );
78    write_private(out, &text)
79}
80
81/// Writes an open seat file at `out`, mode 0600 (ACCESS-011 R1).
82///
83/// The file names the open exchange at `server`, no credential, and
84/// `[open] reach = "network"` when the address is off loopback. An existing
85/// file is refused, never replaced.
86///
87/// # Errors
88/// An invalid server address, or a file that exists or cannot be made.
89pub fn init_open(server: &str, out: &Path) -> Result<(), SeatInitError> {
90    if server.is_empty()
91        || server
92            .chars()
93            .any(|c| c.is_control() || c == '"' || c == '\\')
94    {
95        return Err(SeatInitError::Server);
96    }
97    let reach = if names_loopback(server) {
98        ""
99    } else {
100        "\n[open]\nreach = \"network\"\n"
101    };
102    let text = format!(
103        "# Written by liminal seat init --open (ACCESS-011 R1): an open exchange, no credential.\n\
104         server = \"{server}\"\n\
105         channel = \"{DEFAULT_CHANNEL}\"\n\
106         {reach}\
107         \n\
108         [limits]\n\
109         frame_bytes = 65536\n\
110         record_bytes = 1048576\n\
111         reply_timeout_ms = 10000\n\
112         flow_steps = 8\n\
113         request_bytes = 65536\n"
114    );
115    write_private(out, &text)
116}
117
118fn write_private(out: &Path, text: &str) -> Result<(), SeatInitError> {
119    let unwritable = |error: std::io::Error| SeatInitError::Unwritable {
120        path: out.display().to_string(),
121        message: error.to_string(),
122    };
123    let mut file = OpenOptions::new()
124        .write(true)
125        .create_new(true)
126        .mode(0o600)
127        .open(out)
128        .map_err(unwritable)?;
129    file.write_all(text.as_bytes()).map_err(unwritable)?;
130    file.sync_all().map_err(unwritable)
131}
132
133/// The `host:port` an address dials: a `host:port` as written, or a URL's
134/// host and its port (its scheme's default when it names none).
135fn dial_target(address: &str) -> Option<(String, u16)> {
136    const SCHEMES: [(&str, u16); 4] = [
137        ("wss://", 443),
138        ("https://", 443),
139        ("ws://", 80),
140        ("http://", 80),
141    ];
142    let (rest, default_port) = SCHEMES
143        .iter()
144        .find_map(|(scheme, port)| address.strip_prefix(scheme).map(|rest| (rest, *port)))
145        .unwrap_or((address, 0));
146    let authority = rest.split('/').next()?;
147    if let Some(bracketed) = authority.strip_prefix('[') {
148        let (host, after) = bracketed.split_once(']')?;
149        let port = match after.strip_prefix(':') {
150            Some(port) => port.parse().ok()?,
151            None if default_port > 0 => default_port,
152            None => return None,
153        };
154        return Some((host.to_owned(), port));
155    }
156    match authority.rsplit_once(':') {
157        Some((host, port)) => Some((host.to_owned(), port.parse().ok()?)),
158        None if default_port > 0 => Some((authority.to_owned(), default_port)),
159        None => None,
160    }
161}
162
163/// Whether `address` names this machine: a loopback host, with or without a
164/// scheme and a path (ACCESS-010 R3: an open seat reaches loopback only).
165#[must_use]
166pub fn names_loopback(address: &str) -> bool {
167    dial_target(address).is_some_and(|(host, _)| is_loopback(&host))
168}
169
170/// Whether `host` names this machine.
171fn is_loopback(host: &str) -> bool {
172    host.eq_ignore_ascii_case("localhost") || host == "127.0.0.1" || host == "::1"
173}
174
175/// Refuses an address on this machine that does not accept a connection
176/// within `bound`, with `liminal_mcp_loopback_unanswered` and the address;
177/// any other address is left to its own connection.
178///
179/// # Errors
180/// The loopback address named, when nothing answers on it.
181pub fn refuse_unanswered_loopback(address: &str, bound: Duration) -> Result<(), String> {
182    let Some((host, port)) = dial_target(address) else {
183        return Ok(());
184    };
185    if !is_loopback(&host) {
186        return Ok(());
187    }
188    let unanswered = || format!("liminal_mcp_loopback_unanswered: nothing answers at {address}");
189    let targets: Vec<SocketAddr> = (host.as_str(), port)
190        .to_socket_addrs()
191        .map_err(|_| unanswered())?
192        .collect();
193    if targets
194        .iter()
195        .any(|target| TcpStream::connect_timeout(target, bound).is_ok())
196    {
197        Ok(())
198    } else {
199        Err(unanswered())
200    }
201}
202
203#[cfg(test)]
204#[path = "seat_tests.rs"]
205mod tests;
liminal_cli/seat.rs

liminal_cli/
seat.rs
