feat: add command su

Signed-off-by: sisungo <[email protected]>

bin/account/src/authenticate.rs

@@ -21,25 +21,9 @@ pub fn main(cli: Cli) -> anyhow::Result<()> {
     let mut client = client()?;
     let user = uuid_by_one_user_filter(&mut client, &cli.user)
         .ok_or_else(|| anyhow!("user \"{}\" not found", cli.user))?;
-    let available_methods = client.get_user_auth_methods(GetUserAuthMethodsArgs { user })?;
-    let main_method = available_methods
-        .iter()
-        .find(|x| x.flags.contains(UserAuthMethodFlags::MAIN));
-    let Some(method) = cli.method.or(main_method.map(|x| x.name.clone())) else {
-        return Err(anyhow!("no auth method available"));
-    };
-    if !available_methods.iter().any(|x| x.name == method) {
-        return Err(anyhow!("unregistered auth method {method}"));
+    let ret = crate::util::authenticate(&mut client, user, cli.method, &cli.mode)?;
+    if !ret {
+        std::process::exit(1);
     }
-    let executable = client.get_auth_method_path(GetAuthMethodPathArgs { name: method })?;
-    let args = AuthCli::Authenticate(AuthenticateArgs {
-        user_uuid: user,
-        mode: cli.mode,
-    })
-    .compose();
-    std::process::Command::new(executable)
-        .args(args)
-        .spawn()?
-        .wait()?;
     Ok(())
 }

bin/account/src/main.rs

@@ -2,6 +2,7 @@ mod authenticate;
 mod create_group;
 mod create_user;
 mod info;
+mod su;
 mod update_auth;
 mod util;
 
@@ -27,8 +28,14 @@ pub enum Cli {
 }
 
 fn main() {
-    let cli = Cli::parse();
+    // Invoke non-default utility if required
+    if progname() == "su" {
+        su::main();
+        std::process::exit(0);
+    }
 
+    // Invoke the default `account` utility
+    let cli = Cli::parse();
     let result = match cli {
         Cli::Info(cli) => info::main(cli),
         Cli::CreateUser(cli) => create_user::main(cli),
@@ -36,15 +43,29 @@ fn main() {
         Cli::Authenticate(cli) => authenticate::main(cli),
         Cli::UpdateAuth(cli) => update_auth::main(cli),
     };
-
     if let Err(err) = result {
         eprintln!("error: {err}");
         std::process::exit(1);
     }
 }
 
+fn progname() -> String {
+    std::env::args()
+        .next()
+        .as_deref()
+        .unwrap_or_else(|| "account")
+        .split('/')
+        .last()
+        .unwrap()
+        .into()
+}
+
+fn has_root_privs() -> bool {
+    unsafe { libc::geteuid() == 0 }
+}
+
 fn is_suid_mode() -> bool {
-    unsafe { libc::getuid() != libc::geteuid() && libc::geteuid() == 0 }
+    unsafe { libc::getuid() != libc::geteuid() && has_root_privs() }
 }
 
 fn client() -> std::io::Result<Client> {

bin/account/src/su.rs

@@ -0,0 +1,134 @@
+use semios_account::{protocol::GetUserInfoArgs, wellknown::CLI_LOGIN_SHELL};
+
+use crate::client;
+use std::{ffi::OsString, os::unix::process::CommandExt};
+
+#[derive(Debug)]
+struct Cli {
+    login: bool,
+    preserve_environment: bool,
+    fast: bool,
+    user: String,
+    command: Vec<OsString>,
+}
+impl Cli {
+    const USAGE: &str = "usage: su [options] [-] [login [args]]";
+
+    fn parse() -> Self {
+        let mut this = Self {
+            login: false,
+            preserve_environment: false,
+            fast: true,
+            user: "root".into(),
+            command: Vec::new(),
+        };
+
+        let mut positional = false;
+
+        for i in std::env::args_os().skip(1) {
+            let bytes = i.as_encoded_bytes();
+            if positional {
+                this.command.push(i);
+                continue;
+            }
+            if bytes == b"--login" {
+                this.login = true;
+            } else if bytes == b"--preserve-environment" {
+                this.preserve_environment = true;
+            } else if bytes == b"--fast" {
+                this.fast = true;
+            } else if bytes.starts_with(b"--") {
+                Self::parse_error(bytes);
+            } else if bytes.starts_with(b"-") {
+                if i == "-" {
+                    this.login = true;
+                    continue;
+                }
+                for &byte in &bytes[1..] {
+                    match byte {
+                        b'l' => {
+                            this.login = true;
+                        }
+                        b'm' | b'p' => {
+                            this.preserve_environment = true;
+                        }
+                        b'f' => {
+                            this.fast = true;
+                        }
+                        _ => Self::parse_error(&[byte]),
+                    };
+                }
+            } else {
+                debug_assert!(!positional);
+                positional = true;
+                this.user = String::from_utf8_lossy(bytes).to_string();
+            }
+        }
+
+        this
+    }
+
+    fn parse_error(bytes: &[u8]) -> ! {
+        eprintln!("su: illegal option -- {}", String::from_utf8_lossy(bytes));
+        eprintln!("{}", Self::USAGE);
+        std::process::exit(1);
+    }
+}
+
+pub fn main() {
+    let cli = Cli::parse();
+    let mut client = match client() {
+        Ok(val) => val,
+        Err(err) => {
+            eprintln!("su: Service error: {err}");
+            std::process::exit(1);
+        }
+    };
+    let Ok(user_info) = client.get_user_info(GetUserInfoArgs::Username(cli.user.clone())) else {
+        eprintln!("su: user {} does not exist", cli.user);
+        std::process::exit(1);
+    };
+    let auth_result =
+        crate::util::authenticate(&mut client, user_info.uuid, Some("password".into()), "CLI");
+    match auth_result {
+        Ok(true) => (),
+        Ok(false) => std::process::exit(1),
+        Err(err) => {
+            eprintln!("su: cannot authenticate user: {err}");
+            std::process::exit(1);
+        }
+    };
+    let Some(uid) = user_info.host_uid else {
+        eprintln!("su: user {} is not configured on this host", cli.user);
+        std::process::exit(1);
+    };
+    let Some(shell) = user_info.defaults.get(CLI_LOGIN_SHELL) else {
+        eprintln!("su: user {} has no login shell", cli.user);
+        std::process::exit(1);
+    };
+    let home_dir = user_info.home_directory.unwrap_or_else(|| "/".into());
+
+    if !crate::has_root_privs() {
+        eprintln!("su: the `su` binary is only available with root privileges");
+        std::process::exit(1);
+    }
+
+    // Set environment variables
+    if !cli.preserve_environment || cli.login {
+        // SAFETY: The program is single-threaded, so no data race is possible here.
+        unsafe {
+            std::env::set_var("HOME", &home_dir);
+            std::env::set_var("USER", &cli.user);
+            std::env::set_var("SHELL", &shell);
+            std::env::set_var("LOGNAME", &cli.user);
+        }
+    }
+
+    let err = std::process::Command::new(shell)
+        .uid(uid)
+        .args(cli.command)
+        .exec();
+
+    eprintln!("su: exec error: {err}");
+    std::process::exit(1);
+}

bin/account/src/util.rs

@@ -1,6 +1,8 @@
+use anyhow::anyhow;
 use semios_account::{
+    auth::{AuthCli, AuthenticateArgs, UserAuthMethodFlags},
     client::Client,
-    protocol::{GetGroupInfoArgs, GetUserInfoArgs},
+    protocol::{GetAuthMethodPathArgs, GetGroupInfoArgs, GetUserAuthMethodsArgs, GetUserInfoArgs},
     record::HostUid,
 };
 use std::fmt::Display;
@@ -68,3 +70,32 @@ pub fn uuid_by_one_group_filter(client: &mut Client, filter: &str) -> Option<Uui
 
     Some(client.get_group_info(args).ok()?.uuid)
 }
+
+pub fn authenticate(
+    client: &mut Client,
+    user: Uuid,
+    method: Option<String>,
+    mode: &str,
+) -> anyhow::Result<bool> {
+    let available_methods = client.get_user_auth_methods(GetUserAuthMethodsArgs { user })?;
+    let main_method = available_methods
+        .iter()
+        .find(|x| x.flags.contains(UserAuthMethodFlags::MAIN));
+    let Some(method) = method.or(main_method.map(|x| x.name.clone())) else {
+        return Err(anyhow!("no auth method available"));
+    };
+    if !available_methods.iter().any(|x| x.name == method) {
+        return Err(anyhow!("unregistered auth method {method}"));
+    }
+    let executable = client.get_auth_method_path(GetAuthMethodPathArgs { name: method })?;
+    let args = AuthCli::Authenticate(AuthenticateArgs {
+        user_uuid: user,
+        mode: mode.to_string(),
+    })
+    .compose();
+    let wait_status = std::process::Command::new(executable)
+        .args(args)
+        .spawn()?
+        .wait()?;
+    Ok(wait_status.success())
+}