config: Overhaul config format and implementation

- Split the config system into multiple files in its own folder.
- Use a manual Deserialize implementation for VtSelection.
- Change config format to use sections for better organization.
- Add temporary fallback to parse old format.

greetd/src/config.rs

@@ -1,141 +0,0 @@
-use std::{env, fs::read_to_string};
-
-use getopts::Options;
-use serde::Deserialize;
-
-fn default_vt() -> toml::Value {
-    toml::Value::String("next".to_string())
-}
-
-fn default_greeter_user() -> String {
-    "greeter".to_string()
-}
-
-fn default_socket_path() -> String {
-    "/run/greetd.sock".to_string()
-}
-
-#[derive(Debug, Deserialize)]
-pub struct Config {
-    #[serde(default = "default_vt")]
-    pub vt: toml::Value,
-    pub greeter: String,
-    #[serde(default = "default_greeter_user")]
-    pub greeter_user: String,
-
-    #[serde(default = "default_socket_path")]
-    pub socket_path: String,
-
-    #[serde(skip_deserializing)]
-    pub session_worker: usize,
-}
-
-pub enum VtSelection {
-    Next,
-    Current,
-    None,
-    Specific(usize),
-}
-
-impl Config {
-    pub fn vt(&self) -> VtSelection {
-        match &self.vt {
-            toml::Value::String(s) => match s.as_str() {
-                "next" => VtSelection::Next,
-                "current" => VtSelection::Current,
-                "none" => VtSelection::None,
-                _ => panic!("unknown value of vt, expect next, current, none, or vt number"),
-            },
-            toml::Value::Integer(u) => VtSelection::Specific(*u as usize),
-            _ => panic!("unknown value of vt, expect next, current, or vt number"),
-        }
-    }
-}
-
-fn print_usage(program: &str, opts: Options) {
-    let brief = format!("Usage: {} [options]", program);
-    print!("{}", opts.usage(&brief));
-}
-
-pub fn read_config() -> Config {
-    let args: Vec<String> = env::args().collect();
-    let program = args[0].clone();
-    let mut opts = Options::new();
-    opts.optflag("h", "help", "print this help menu");
-    opts.optopt("t", "vt", "VT to run on", "VT");
-    opts.optopt("s", "socket-path", "socket path to use", "SOCKET_PATH");
-    opts.optopt("g", "greeter", "greeter to run", "GREETER");
-    opts.optopt("u", "greeter-user", "user to run greeter as", "USER");
-    opts.optopt("c", "config", "config file to use", "CONFIG_FILE");
-    opts.optopt(
-        "w",
-        "session-worker",
-        "start a session worker (internal)",
-        "FD",
-    );
-    let matches = match opts.parse(&args[1..]) {
-        Ok(m) => m,
-        Err(f) => panic!(f.to_string()),
-    };
-    if matches.opt_present("h") {
-        print_usage(&program, opts);
-        std::process::exit(0);
-    }
-
-    let mut config = match read_to_string(
-        matches
-            .opt_str("config")
-            .unwrap_or_else(|| "/etc/greetd/config.toml".to_string()),
-    ) {
-        Ok(s) => match toml::from_str(&s) {
-            Ok(v) => v,
-            Err(e) => {
-                eprintln!("Unable to parse configuration file: {:?}", e);
-                eprintln!("Please fix the configuration file and try again.");
-                std::process::exit(1);
-            }
-        },
-        Err(_) => Config {
-            vt: default_vt(),
-            greeter: "".to_string(),
-            greeter_user: "".to_string(),
-            socket_path: default_socket_path(),
-            session_worker: 0,
-        },
-    };
-
-    if let Some(vt) = matches.opt_str("vt") {
-        config.vt = match vt.as_str() {
-            "next" => toml::Value::String("next".to_string()),
-            "current" => toml::Value::String("current".to_string()),
-            "none" => toml::Value::String("none".to_string()),
-            v => toml::Value::Integer(v.parse().expect("could not parse vt number")),
-        }
-    }
-    if let Some(greeter) = matches.opt_str("greeter") {
-        config.greeter = greeter;
-    }
-    if let Some(user) = matches.opt_str("greeter-user") {
-        config.greeter_user = user;
-    }
-    if let Some(socket_path) = matches.opt_str("socket-path") {
-        config.socket_path = socket_path;
-    }
-    if let Some(session_worker) = matches
-        .opt_get("session-worker")
-        .expect("unable to parse session-worker")
-    {
-        config.session_worker = session_worker
-    }
-
-    if config.greeter.is_empty() {
-        eprintln!("No greeter specified. Run with --help for more information.");
-        std::process::exit(1);
-    }
-    if config.greeter_user.is_empty() {
-        eprintln!("No greeter user specified. Run with --help for more information.");
-        std::process::exit(1);
-    }
-
-    config
-}

greetd/src/config/defaults.rs

@@ -0,0 +1,9 @@
+use super::vtselection::VtSelection;
+
+pub fn default_vt() -> VtSelection {
+    VtSelection::Next
+}
+
+pub fn default_greeter_user() -> String {
+    "greeter".to_string()
+}

greetd/src/config/mod.rs

@@ -0,0 +1,93 @@
+mod defaults;
+mod old_config;
+mod types;
+mod vtselection;
+
+use std::{env, fs::read_to_string};
+
+use getopts::Options;
+
+use super::error::Error;
+use old_config::*;
+
+pub use types::*;
+pub use vtselection::VtSelection;
+
+fn print_usage(program: &str, opts: Options) {
+    let brief = format!("Usage: {} [options]", program);
+    print!("{}", opts.usage(&brief));
+}
+
+pub fn read_config() -> Result<Config, Error> {
+    let args: Vec<String> = env::args().collect();
+    let program = args[0].clone();
+    let mut opts = Options::new();
+    opts.optflag("h", "help", "print this help menu");
+    opts.optopt("s", "socket-path", "socket path to use", "SOCKET_PATH");
+    opts.optopt("c", "config", "config file to use", "CONFIG_FILE");
+    opts.optopt(
+        "w",
+        "session-worker",
+        "start a session worker (internal)",
+        "FD",
+    );
+    let matches = match opts.parse(&args[1..]) {
+        Ok(m) => m,
+        Err(f) => return Err(format!("could not parse arguments: {}", f).into()),
+    };
+    if matches.opt_present("h") {
+        print_usage(&program, opts);
+        std::process::exit(0);
+    }
+
+    let internal = ConfigInternal {
+        socket_path: matches
+            .opt_str("socket-path")
+            .unwrap_or_else(|| "/run/greetd.sock".to_string()),
+        session_worker: matches
+            .opt_get("session-worker")
+            .expect("unable to parse session-worker")
+            .unwrap_or(0),
+    };
+
+    let file = match read_to_string(
+        matches
+            .opt_str("config")
+            .unwrap_or_else(|| "/etc/greetd/config.toml".to_string()),
+    ) {
+        Ok(s) => match toml::from_str(&s) {
+            Ok(v) => v,
+            Err(e) => match try_read_old_config(&s) {
+                Ok(v) => {
+                    eprintln!("warning: Fallback to old config format, caused by : {}", e);
+                    v
+                }
+                Err(_e) => {
+                    return Err(Error::ConfigError(
+                        format!("unable to parse configuration file: {}", e).to_string(),
+                    ))
+                }
+            },
+        },
+        Err(_) => ConfigFile {
+            default_session: ConfigDefaultSession {
+                user: "greeter".to_string(),
+                command: "".to_string(),
+            },
+            terminal: Default::default(),
+        },
+    };
+
+    if file.default_session.command.is_empty() {
+        return Err(Error::ConfigError(
+            "no default session user specified".to_string(),
+        ));
+    }
+    if file.default_session.user.is_empty() {
+        return Err(Error::ConfigError(
+            "no default session user specified".to_string(),
+        ));
+    }
+
+    Ok(Config { file, internal })
+}

greetd/src/config/old_config.rs

@@ -0,0 +1,35 @@
+use serde::Deserialize;
+
+use crate::error::Error;
+
+use super::vtselection::VtSelection;
+
+use super::{defaults::*, types::*};
+
+#[derive(Debug, Deserialize)]
+pub struct OldConfig {
+    #[serde(default = "default_vt")]
+    pub vt: VtSelection,
+    pub greeter: String,
+    #[serde(default = "default_greeter_user")]
+    pub greeter_user: String,
+}
+
+pub fn try_read_old_config(s: &str) -> Result<super::ConfigFile, Error> {
+    let oldconfig: OldConfig = match toml::from_str(&s) {
+        Ok(v) => v,
+        Err(e) => {
+            return Err(Error::ConfigError(
+                format!("unable to parse configuration file: {}", e).to_string(),
+            ))
+        }
+    };
+
+    Ok(ConfigFile {
+        terminal: ConfigTerminal { vt: oldconfig.vt },
+        default_session: ConfigDefaultSession {
+            user: oldconfig.greeter_user,
+            command: oldconfig.greeter,
+        },
+    })
+}

greetd/src/config/types.rs

@@ -0,0 +1,37 @@
+use super::{defaults::*, vtselection::VtSelection};
+use serde::Deserialize;
+
+#[derive(Debug, Deserialize)]
+pub struct ConfigDefaultSession {
+    pub command: String,
+    #[serde(default = "default_greeter_user")]
+    pub user: String,
+}
+
+pub struct ConfigInternal {
+    pub socket_path: String,
+    pub session_worker: usize,
+}
+
+#[derive(Debug, Deserialize)]
+pub struct ConfigTerminal {
+    #[serde(default = "default_vt")]
+    pub vt: VtSelection,
+}
+
+impl Default for ConfigTerminal {
+    fn default() -> ConfigTerminal {
+        ConfigTerminal { vt: default_vt() }
+    }
+}
+
+#[derive(Debug, Deserialize)]
+pub struct ConfigFile {
+    pub terminal: ConfigTerminal,
+    pub default_session: ConfigDefaultSession,
+}
+
+pub struct Config {
+    pub file: ConfigFile,
+    pub internal: ConfigInternal,
+}

greetd/src/config/vtselection.rs

@@ -0,0 +1,62 @@
+use std::fmt;
+
+use serde::{
+    de::{self, Deserializer, Visitor},
+    Deserialize,
+};
+
+struct VtSelectionVisitor;
+
+impl<'de> Visitor<'de> for VtSelectionVisitor {
+    type Value = VtSelection;
+
+    fn expecting(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+        formatter.write_str("next, currrent, none or a positive vt number")
+    }
+
+    fn visit_i64<E>(self, value: i64) -> Result<Self::Value, E>
+    where
+        E: de::Error,
+    {
+        if value < 1 {
+            Err(de::Error::invalid_value(
+                de::Unexpected::Signed(value),
+                &"next, current, none or a positive vt number",
+            ))
+        } else {
+            Ok(VtSelection::Specific(value as usize))
+        }
+    }
+
+    fn visit_str<E>(self, value: &str) -> Result<Self::Value, E>
+    where
+        E: de::Error,
+    {
+        match value {
+            "next" => Ok(VtSelection::Next),
+            "current" => Ok(VtSelection::Current),
+            "none" => Ok(VtSelection::None),
+            _ => Err(de::Error::invalid_value(
+                de::Unexpected::Str(value),
+                &"next, current, none or a postive vt number",
+            )),
+        }
+    }
+}
+
+#[derive(Debug)]
+pub enum VtSelection {
+    Next,
+    Current,
+    None,
+    Specific(usize),
+}
+
+impl<'de> Deserialize<'de> for VtSelection {
+    fn deserialize<D>(deserializer: D) -> Result<VtSelection, D::Error>
+    where
+        D: Deserializer<'de>,
+    {
+        deserializer.deserialize_any(VtSelectionVisitor)
+    }
+}

greetd/src/error.rs

@@ -16,6 +16,9 @@ pub enum Error {
 
     #[error("i/o error: {0}")]
     Io(String),
+
+    #[error("configuration error: {0}")]
+    ConfigError(String),
 }
 
 impl From<Box<dyn std::error::Error>> for Error {

greetd/src/main.rs

@@ -21,7 +21,7 @@ use tokio::task;
 use crate::{error::Error, session::worker};
 
 async fn session_worker_main(config: config::Config) -> Result<(), Error> {
-    let raw_fd = config.session_worker as RawFd;
+    let raw_fd = config.internal.session_worker as RawFd;
     let mut cur_flags = unsafe { FdFlag::from_bits_unchecked(fcntl(raw_fd, FcntlArg::F_GETFD)?) };
     cur_flags.insert(FdFlag::FD_CLOEXEC);
     fcntl(raw_fd, FcntlArg::F_SETFD(cur_flags))?;
@@ -31,11 +31,17 @@ async fn session_worker_main(config: config::Config) -> Result<(), Error> {
 
 #[tokio::main]
 async fn main() {
-    let config = config::read_config();
+    let config = match config::read_config() {
+        Ok(config) => config,
+        Err(e) => {
+            eprintln!("{}", e);
+            std::process::exit(1);
+        }
+    };
     mlockall(MlockAllFlags::all()).expect("unable to lock pages");
     let res = task::LocalSet::new()
         .run_until(async move {
-            if config.session_worker > 0 {
+            if config.internal.session_worker > 0 {
                 session_worker_main(config).await
             } else {
                 server::main(config).await

greetd/src/server.rs

@@ -77,17 +77,12 @@ async fn client_handler(ctx: &Context, mut s: UnixStream) -> Result<(), Error> {
 }
 
 pub async fn main(config: Config) -> Result<(), Error> {
-    std::env::set_var("GREETD_SOCK", &config.socket_path);
+    std::env::set_var("GREETD_SOCK", &config.internal.socket_path);
 
-    let _ = std::fs::remove_file(config.socket_path.clone());
-    let mut listener = UnixListener::bind(&config.socket_path)
+    let _ = std::fs::remove_file(&config.internal.socket_path);
+    let mut listener = UnixListener::bind(&config.internal.socket_path)
         .map_err(|e| format!("unable to open listener: {}", e))?;
 
-    let u = users::get_user_by_name(&config.greeter_user).ok_or(format!(
-        "configured greeter user '{}' not found",
-        &config.greeter_user
-    ))?;
-
     let service = if Path::new("/etc/pam.d/greetd").exists() {
         "greetd"
     } else if Path::new("/etc/pam.d/login").exists() {
@@ -97,13 +92,22 @@ pub async fn main(config: Config) -> Result<(), Error> {
         return Err("PAM 'greetd' service missing".into());
     };
 
+    let u = users::get_user_by_name(&config.file.default_session.user).ok_or(format!(
+        "configured default session user '{}' not found",
+        &config.file.default_session.user
+    ))?;
+
     let uid = Uid::from_raw(u.uid());
     let gid = Gid::from_raw(u.primary_group_id());
-    chown(config.socket_path.as_str(), Some(uid), Some(gid))
-        .map_err(|e| format!("unable to chown greetd socket: {}", e))?;
+    chown(config.internal.socket_path.as_str(), Some(uid), Some(gid)).map_err(|e| {
+        format!(
+            "unable to chown greetd socket at {}: {}",
+            &config.internal.socket_path, e
+        )
+    })?;
 
     let term = Terminal::open(0).map_err(|e| format!("unable to open terminal: {}", e))?;
-    let vt = match config.vt() {
+    let vt = match config.file.terminal.vt {
         VtSelection::Current => term
             .vt_get_current()
             .map_err(|e| format!("unable to get current VT: {}", e))?,
@@ -116,11 +120,12 @@ pub async fn main(config: Config) -> Result<(), Error> {
     drop(term);
 
     let ctx = Rc::new(Context::new(
-        config.greeter,
-        config.greeter_user,
+        config.file.default_session.command,
+        config.file.default_session.user,
         vt,
         service.to_string(),
     ));
+
     if let Err(e) = ctx.greet().await {
         eprintln!("unable to start greeter: {}", e);
         reset_vt(vt).map_err(|e| format!("unable to reset VT: {}", e))?;

man/greetd-5.scd

@@ -10,6 +10,10 @@ greetd uses a simple TOML configuration file to define its behavior.
 
 # CONFIGURATION
 
+## terminal
+
+This section contains terminal configuration.
+
 *vt* = num|"next"|"current"
 	The VT to run on. Can be the number of a specific VT, "next" to select the
 	next available VT, or "current" to stay wherever greetd was started. The
@@ -23,16 +27,44 @@ greetd uses a simple TOML configuration file to define its behavior.
 
 	Use of a specific VT with appropriate conflict avoidance is recommended.
 
-*greeter* = command-line
-	The command-line to run to start the greeter, e.g. "agreety -c sway". The
-	greeter will be run when greetd is initially launched, and every time a
-	created session terminates.
+## default_session
+
+This section describes the default session, also referred to as the "greeter".
+
+*command* = command-line
+	The command-line to run to start the default session, e.g. "agreety -c sway".
+	The default session is automatically started when no other session is
+	running, such as when user session terminate, and when greetd is initially
+	started with no initial session configured.
 
 	See *greetd-ipc*(7) for information on how a greeter can create sessions.
 
-*greeter_user* = user
+*user* = user
 	The user to use for running the greeter. Defaults to "greeter".
 
+## initial_session
+
+This optional section describes the initial session, commonly referred to as
+"auto-login".
+
+*command* = command-line
+	The command-line to run to start the initial session, e.g. "sway". The
+	initial session will be run when exactly once when greetd is initially
+	launched.
+
+*user* = user
+	The user to use for running the initial session.
+
+# EXAMPLE
+
+```toml
+[terminal]
+vt = 1
+
+[default_session]
+command = "agreety -c sway"
+```
+
 # AUTHORS
 
 Maintained by Kenny Levinsen <contact@kl.wtf>. For more information about