cli: Initial yubikey-cli utility with list command

Adds a `yubikey-cli` crate to the workspace, with a `yubikey` binary,
which presently provides a `list` command for listing detected readers.

Dependencies:

- `env_logger`: logging
- `gumdrop`: argument parsing
- `termcolor`: colored terminal output

As this repo now contains a binary, it also checks in `Cargo.lock`.

cli/src/bin/yubikey/main.rs

@@ -0,0 +1,16 @@
+//! `yubikey` command-line utility
+
+#![forbid(unsafe_code)]
+#![warn(
+    missing_docs,
+    rust_2018_idioms,
+    unused_lifetimes,
+    unused_qualifications
+)]
+
+use gumdrop::Options;
+use yubikey_cli::commands::YubikeyCli;
+
+fn main() {
+    YubikeyCli::parse_args_default_or_exit().run();
+}

cli/src/commands.rs

@@ -0,0 +1,98 @@
+//! Commands of the CLI application
+
+pub mod list;
+
+use self::list::ListCmd;
+use crate::status;
+use gumdrop::Options;
+use std::env;
+use std::process::exit;
+use termcolor::ColorChoice;
+
+/// The `yubikey` CLI utility
+#[derive(Debug, Options)]
+pub struct YubikeyCli {
+    /// Obtain help about the current command
+    #[options(short = "h", help = "print help message")]
+    pub help: bool,
+
+    /// Subcommand to execute.
+    #[options(command)]
+    pub command: Option<Commands>,
+}
+
+impl YubikeyCli {
+    /// Run the underlying command type or print usage info and exit
+    pub fn run(&self) {
+        // TODO(tarcieri): make this more configurable
+        status::set_color_choice(ColorChoice::Auto);
+
+        // Only show logs if `RUST_LOG` is set
+        if env::var("RUST_LOG").is_ok() {
+            env_logger::builder().format_timestamp(None).init();
+        }
+
+        match &self.command {
+            Some(cmd) => cmd.run(),
+            None => println!("{}", Commands::usage()),
+        }
+    }
+}
+
+/// Subcommands of this application
+#[derive(Debug, Options)]
+pub enum Commands {
+    /// `help` subcommand
+    #[options(help = "show help for a command")]
+    Help(HelpOpts),
+
+    /// `version` subcommand
+    #[options(help = "display version information")]
+    Version(VersionOpts),
+
+    /// `list` subcommand
+    #[options(help = "list detected readers")]
+    List(ListCmd),
+}
+
+impl Commands {
+    /// Run the given command
+    pub fn run(&self) {
+        match self {
+            Commands::Help(help) => help.run(),
+            Commands::Version(version) => version.run(),
+            Commands::List(list) => list.run(),
+        }
+    }
+}
+
+/// Help options
+#[derive(Debug, Options)]
+pub struct HelpOpts {
+    #[options(free, help = "subcommand to get help for")]
+    free: Vec<String>,
+}
+
+impl HelpOpts {
+    fn run(&self) {
+        if let Some(command) = self.free.first() {
+            if let Some(usage) = Commands::command_usage(command) {
+                println!("{}", usage);
+                exit(1);
+            }
+        }
+
+        println!("{}", Commands::usage());
+    }
+}
+
+/// Version options
+#[derive(Debug, Options)]
+pub struct VersionOpts {}
+
+impl VersionOpts {
+    /// Display version information
+    pub fn run(&self) {
+        println!("{} {}", env!("CARGO_PKG_NAME"), env!("CARGO_PKG_VERSION"));
+    }
+}

cli/src/commands/list.rs

@@ -0,0 +1,40 @@
+//! List detected readers
+
+use gumdrop::Options;
+use std::process::exit;
+use yubikey_piv::readers::Readers;
+
+/// The `list` subcommand
+#[derive(Debug, Options)]
+pub struct ListCmd {}
+
+impl ListCmd {
+    /// Run the `list` subcommand
+    pub fn run(&self) {
+        let mut readers = Readers::open().unwrap_or_else(|e| {
+            status_err!("couldn't open PC/SC context: {}", e);
+            exit(1);
+        });
+
+        let readers_iter = readers.iter().unwrap_or_else(|e| {
+            status_err!("couldn't enumerate PC/SC readers: {}", e);
+            exit(1);
+        });
+
+        if readers_iter.len() == 0 {
+            status_err!("no YubiKeys detected!");
+            exit(1);
+        }
+
+        for (i, reader) in readers_iter.enumerate() {
+            let name = reader.name();
+            let mut yubikey = match reader.open() {
+                Ok(yk) => yk,
+                Err(_) => continue,
+            };
+
+            let serial = yubikey.serial();
+            println!("{}: {} (serial: {})", i + 1, name, serial);
+        }
+    }
+}

cli/src/lib.rs

@@ -0,0 +1,14 @@
+//! `yubikey` command-line utility
+
+#![forbid(unsafe_code)]
+#![warn(
+    missing_docs,
+    rust_2018_idioms,
+    unused_lifetimes,
+    unused_qualifications
+)]
+
+#[macro_use]
+pub mod status;
+
+pub mod commands;

cli/src/status.rs

@@ -0,0 +1,165 @@
+//! Status messages
+
+use lazy_static::lazy_static;
+use std::io::{self, Write};
+use std::sync::Mutex;
+use termcolor::{Color, ColorChoice, ColorSpec, StandardStream, WriteColor};
+
+/// Print a success status message (in green if colors are enabled)
+#[macro_export]
+macro_rules! status_ok {
+    ($status:expr, $msg:expr) => {
+        $crate::status::Status::new()
+            .justified()
+            .bold()
+            .color(termcolor::Color::Green)
+            .status($status)
+            .print_stdout($msg);
+    };
+    ($status:expr, $fmt:expr, $($arg:tt)+) => {
+        $crate::status_ok!($status, format!($fmt, $($arg)+));
+    };
+}
+
+/// Print a warning status message (in yellow if colors are enabled)
+#[macro_export]
+macro_rules! status_warn {
+    ($msg:expr) => {
+        $crate::status::Status::new()
+            .bold()
+            .color(termcolor::Color::Yellow)
+            .status("warning:")
+            .print_stdout($msg);
+    };
+    ($fmt:expr, $($arg:tt)+) => {
+        $crate::status_warn!(format!($fmt, $($arg)+));
+    };
+}
+
+/// Print an error message (in red if colors are enabled)
+#[macro_export]
+macro_rules! status_err {
+    ($msg:expr) => {
+        $crate::status::Status::new()
+            .bold()
+            .color(termcolor::Color::Red)
+            .status("error:")
+            .print_stderr($msg);
+    };
+    ($fmt:expr, $($arg:tt)+) => {
+        $crate::status_err!(format!($fmt, $($arg)+));
+    };
+}
+
+lazy_static! {
+    /// Color configuration
+    static ref COLOR_CHOICE: Mutex<Option<ColorChoice>> = Mutex::new(None);
+
+    /// Standard output
+    pub static ref STDOUT: StandardStream = StandardStream::stdout(get_color_choice());
+
+    /// Standard error
+    pub static ref STDERR: StandardStream = StandardStream::stderr(get_color_choice());
+}
+
+/// Obtain the color configuration.
+///
+/// Panics if no configuration has been provided.
+fn get_color_choice() -> ColorChoice {
+    let choice = COLOR_CHOICE.lock().unwrap();
+    *choice
+        .as_ref()
+        .expect("terminal stream accessed before initialized!")
+}
+
+/// Set the color configuration.
+///
+/// Panics if the terminal has already been configured.
+pub(super) fn set_color_choice(color_choice: ColorChoice) {
+    let mut choice = COLOR_CHOICE.lock().unwrap();
+    assert!(choice.is_none(), "terminal colors already configured!");
+    *choice = Some(color_choice);
+}
+
+/// Status message builder
+#[derive(Clone, Debug, Default)]
+pub struct Status {
+    /// Should the status be justified?
+    justified: bool,
+
+    /// Should colors be bold?
+    bold: bool,
+
+    /// Color in which status should be displayed
+    color: Option<Color>,
+
+    /// Prefix of the status message (e.g. `Success`)
+    status: Option<String>,
+}
+
+impl Status {
+    /// Create a new status message with default settings
+    pub fn new() -> Self {
+        Self::default()
+    }
+
+    /// Justify status on display
+    pub fn justified(mut self) -> Self {
+        self.justified = true;
+        self
+    }
+
+    /// Make colors bold
+    pub fn bold(mut self) -> Self {
+        self.bold = true;
+        self
+    }
+
+    /// Set the colors used to display this message
+    pub fn color(mut self, c: Color) -> Self {
+        self.color = Some(c);
+        self
+    }
+
+    /// Set a status message to display
+    pub fn status<S>(mut self, msg: S) -> Self
+    where
+        S: ToString,
+    {
+        self.status = Some(msg.to_string());
+        self
+    }
+
+    /// Print the given message to stdout
+    pub fn print_stdout(self, msg: impl AsRef<str>) {
+        self.print(&*STDOUT, msg)
+            .expect("error printing to stdout!")
+    }
+
+    /// Print the given message to stderr
+    pub fn print_stderr(self, msg: impl AsRef<str>) {
+        self.print(&*STDERR, msg)
+            .expect("error printing to stderr!")
+    }
+
+    /// Print the given message
+    fn print(self, stream: &StandardStream, msg: impl AsRef<str>) -> Result<(), io::Error> {
+        let mut s = stream.lock();
+        s.reset()?;
+        s.set_color(ColorSpec::new().set_fg(self.color).set_bold(self.bold))?;
+
+        if let Some(status) = self.status {
+            if self.justified {
+                write!(s, "{:>12}", status)?;
+            } else {
+                write!(s, "{}", status)?;
+            }
+        }
+
+        s.reset()?;
+        writeln!(s, " {}", msg.as_ref())?;
+        s.flush()?;
+
+        Ok(())
+    }
+}