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/// The limits a new seat is written with, and a seat named only by flags takes.
22const DEFAULT_LIMITS: [(&str, i64); 5] = [
23    ("frame_bytes", 65536),
24    ("record_bytes", 1_048_576),
25    ("reply_timeout_ms", 10000),
26    ("flow_steps", 8),
27    ("request_bytes", 65536),
28];
29
30/// A seat with no file: the default channel and limits, the central
31/// exchange by the server's own default, and no credential until a flag
32/// names one.
33pub(crate) fn defaults() -> toml::Table {
34    let limits: toml::Table = DEFAULT_LIMITS
35        .iter()
36        .map(|(field, value)| ((*field).to_owned(), toml::Value::Integer(*value)))
37        .collect();
38    toml::Table::from_iter([
39        (
40            "channel".to_owned(),
41            toml::Value::String(DEFAULT_CHANNEL.to_owned()),
42        ),
43        ("limits".to_owned(), toml::Value::Table(limits)),
44    ])
45}
46
47/// The `[limits]` table as `liminal seat init` writes it.
48fn limits_text() -> String {
49    DEFAULT_LIMITS
50        .iter()
51        .map(|(field, value)| format!("{field} = {value}\n"))
52        .fold(String::from("[limits]\n"), |text, line| text + &line)
53}
54
55/// Why `liminal seat init` wrote nothing.
56#[derive(Debug, thiserror::Error)]
57pub enum SeatInitError {
58    /// The agent id is empty or is not one line of printable characters.
59    #[error("liminal_seat_agent_invalid: the agent id must be one line of printable characters")]
60    Agent,
61    /// The key file path cannot be written into the seat as text.
62    #[error("liminal_seat_key_file_invalid: {0} is not a UTF-8 path")]
63    KeyFile(String),
64    /// The open exchange address is empty or is not one line of printable characters.
65    #[error("liminal_seat_server_invalid: the server must be one line of printable characters")]
66    Server,
67    /// The declared name is not 1 to 64 of `a-z`, `0-9`, `.`, `_` or `-` (ACCESS-012 R2).
68    #[error("liminal_seat_name_invalid: the name must be 1 to 64 of a-z, 0-9, '.', '_' or '-'")]
69    Name,
70    /// The seat file exists or cannot be created; it is never overwritten.
71    #[error("liminal_seat_unwritable: {path}: {message}")]
72    Unwritable {
73        /// The seat file asked for.
74        path: String,
75        /// The operating system's words.
76        message: String,
77    },
78}
79
80/// Writes a seat file at `out`, mode 0600, naming the central exchange and
81/// Lys, the agent and its key file, and never a pass. An existing file is
82/// refused, never replaced.
83///
84/// # Errors
85/// An invalid agent id or key path, or a file that exists or cannot be made.
86pub fn init(agent: &str, key_file: &Path, out: &Path) -> Result<(), SeatInitError> {
87    if agent.is_empty()
88        || agent
89            .chars()
90            .any(|c| c.is_control() || c == '"' || c == '\\')
91    {
92        return Err(SeatInitError::Agent);
93    }
94    let key = key_file
95        .to_str()
96        .filter(|k| !k.chars().any(|c| c.is_control() || c == '"' || c == '\\'))
97        .ok_or_else(|| SeatInitError::KeyFile(key_file.display().to_string()))?;
98    let text = format!(
99        "# Written by liminal seat init (AGT-006 R3): the central exchange and Lys.\n\
100         server = \"{CENTRAL_SERVER}\"\n\
101         channel = \"{DEFAULT_CHANNEL}\"\n\
102         \n\
103         [lys]\n\
104         issuer = \"{CENTRAL_ISSUER}\"\n\
105         agent = \"{agent}\"\n\
106         key_file = \"{key}\"\n\
107         \n\
108         {limits}",
109        limits = limits_text()
110    );
111    write_private(out, &text)
112}
113
114/// Writes an open seat file at `out`, mode 0600 (ACCESS-011 R1).
115///
116/// The file names the open exchange at `server`, no credential, and
117/// `[open] reach = "network"` when the address is off loopback. An existing
118/// file is refused, never replaced.
119///
120/// # Errors
121/// An invalid server address, or a file that exists or cannot be made.
122pub fn init_open(server: &str, out: &Path) -> Result<(), SeatInitError> {
123    init_open_named(server, None, out)
124}
125
126/// Writes an open seat for the open exchange at `server` declaring `name`
127/// (ACCESS-012 R2), recorded by the exchange as `open:<name>`; with no name
128/// the seat is anonymous.
129///
130/// # Errors
131/// The server address or the name is not one the seat can carry, or the
132/// file cannot be written.
133pub fn init_open_named(server: &str, name: Option<&str>, out: &Path) -> Result<(), SeatInitError> {
134    if server.is_empty()
135        || server
136            .chars()
137            .any(|c| c.is_control() || c == '"' || c == '\\')
138    {
139        return Err(SeatInitError::Server);
140    }
141    if name.is_some_and(|name| !crate::config::is_open_name(name)) {
142        return Err(SeatInitError::Name);
143    }
144    let reach = if names_loopback(server) {
145        ""
146    } else {
147        "reach = \"network\"\n"
148    };
149    let name = name.map_or(String::new(), |name| format!("name = \"{name}\"\n"));
150    let open = if reach.is_empty() && name.is_empty() {
151        String::new()
152    } else {
153        format!("\n[open]\n{reach}{name}")
154    };
155    let text = format!(
156        "# Written by liminal seat init --open (ACCESS-011 R1): an open exchange, no credential.\n\
157         server = \"{server}\"\n\
158         channel = \"{DEFAULT_CHANNEL}\"\n\
159         {open}\
160         \n\
161         {limits}",
162        limits = limits_text()
163    );
164    write_private(out, &text)
165}
166
167fn write_private(out: &Path, text: &str) -> Result<(), SeatInitError> {
168    let unwritable = |error: std::io::Error| SeatInitError::Unwritable {
169        path: out.display().to_string(),
170        message: error.to_string(),
171    };
172    let mut file = OpenOptions::new()
173        .write(true)
174        .create_new(true)
175        .mode(0o600)
176        .open(out)
177        .map_err(unwritable)?;
178    file.write_all(text.as_bytes()).map_err(unwritable)?;
179    file.sync_all().map_err(unwritable)
180}
181
182/// The `host:port` an address dials: a `host:port` as written, or a URL's
183/// host and its port (its scheme's default when it names none).
184fn dial_target(address: &str) -> Option<(String, u16)> {
185    const SCHEMES: [(&str, u16); 4] = [
186        ("wss://", 443),
187        ("https://", 443),
188        ("ws://", 80),
189        ("http://", 80),
190    ];
191    let (rest, default_port) = SCHEMES
192        .iter()
193        .find_map(|(scheme, port)| address.strip_prefix(scheme).map(|rest| (rest, *port)))
194        .unwrap_or((address, 0));
195    let authority = rest.split('/').next()?;
196    if let Some(bracketed) = authority.strip_prefix('[') {
197        let (host, after) = bracketed.split_once(']')?;
198        let port = match after.strip_prefix(':') {
199            Some(port) => port.parse().ok()?,
200            None if default_port > 0 => default_port,
201            None => return None,
202        };
203        return Some((host.to_owned(), port));
204    }
205    match authority.rsplit_once(':') {
206        Some((host, port)) => Some((host.to_owned(), port.parse().ok()?)),
207        None if default_port > 0 => Some((authority.to_owned(), default_port)),
208        None => None,
209    }
210}
211
212/// Whether `address` names this machine: a loopback host, with or without a
213/// scheme and a path (ACCESS-010 R3: an open seat reaches loopback only).
214#[must_use]
215pub fn names_loopback(address: &str) -> bool {
216    dial_target(address).is_some_and(|(host, _)| is_loopback(&host))
217}
218
219/// Whether `host` names this machine.
220fn is_loopback(host: &str) -> bool {
221    host.eq_ignore_ascii_case("localhost") || host == "127.0.0.1" || host == "::1"
222}
223
224/// Refuses an address on this machine that does not accept a connection
225/// within `bound`, with `liminal_mcp_loopback_unanswered` and the address;
226/// any other address is left to its own connection.
227///
228/// # Errors
229/// The loopback address named, when nothing answers on it.
230pub fn refuse_unanswered_loopback(address: &str, bound: Duration) -> Result<(), String> {
231    let Some((host, port)) = dial_target(address) else {
232        return Ok(());
233    };
234    if !is_loopback(&host) {
235        return Ok(());
236    }
237    let unanswered = || format!("liminal_mcp_loopback_unanswered: nothing answers at {address}");
238    let targets: Vec<SocketAddr> = (host.as_str(), port)
239        .to_socket_addrs()
240        .map_err(|_| unanswered())?
241        .collect();
242    if targets
243        .iter()
244        .any(|target| TcpStream::connect_timeout(target, bound).is_ok())
245    {
246        Ok(())
247    } else {
248        Err(unanswered())
249    }
250}
251
252#[cfg(test)]
253#[path = "seat_tests.rs"]
254mod tests;
liminal_cli/seat.rs

liminal_cli/
seat.rs
