tools: add tty helper module

with read_password() and stdin_isatty() functions

Signed-off-by: Wolfgang Bumiller <w.bumiller@proxmox.com>

src/tools.rs

@@ -26,6 +26,7 @@ pub mod common_regex;
 pub mod ticket;
 pub mod borrow;
 pub mod fs;
+pub mod tty;
 
 /// Macro to write error-handling blocks (like perl eval {})
 ///

src/tools/tty.rs

@@ -0,0 +1,84 @@
+//! Helpers for terminal interaction
+
+use std::io::{Read, Write};
+use std::os::unix::io::AsRawFd;
+
+use failure::*;
+
+use crate::try_block;
+
+/// Returns whether the current stdin is a tty .
+pub fn stdin_isatty() -> bool {
+    unsafe { libc::isatty(std::io::stdin().as_raw_fd()) == 1 }
+}
+
+/// Read a password from stdin, masking the echoed output with asterisks and writing a query first.
+pub fn read_password(query: &str) -> Result<Vec<u8>, Error> {
+    let input = std::io::stdin();
+    if unsafe { libc::isatty(input.as_raw_fd()) } != 1 {
+        let mut out = String::new();
+        input.read_line(&mut out)?;
+        return Ok(out.into_bytes());
+    }
+
+    let mut out = std::io::stdout();
+    let _ignore_error = out.write_all(query.as_bytes());
+    let _ignore_error = out.flush();
+
+    let infd = input.as_raw_fd();
+    let mut termios: libc::termios = unsafe { std::mem::uninitialized() };
+    if unsafe { libc::tcgetattr(infd, &mut termios) } != 0 {
+        bail!("tcgetattr() failed");
+    }
+    let old_termios = termios.clone();
+    unsafe {
+        libc::cfmakeraw(&mut termios);
+    }
+    if unsafe { libc::tcsetattr(infd, libc::TCSANOW, &termios) } != 0 {
+        bail!("tcsetattr() failed");
+    }
+
+    let mut password = Vec::<u8>::new();
+    let mut asterisks = true;
+
+    let ok: Result<(), Error> = try_block!({
+        for byte in input.bytes() {
+            let byte = byte?;
+            match byte {
+                3 => bail!("cancelled"), // ^C
+                4 => break, // ^D / EOF
+                9 => asterisks = false, // tab disables echo
+                0xA | 0xD => { // newline, we're done
+                    let _ignore_error = out.write_all("\r\n".as_bytes());
+                    let _ignore_error = out.flush();
+                    break;
+                }
+                0x7F => { // backspace
+                    if password.len() > 0{
+                        password.pop();
+                        if asterisks {
+                            let _ignore_error = out.write_all("\x08 \x08".as_bytes());
+                            let _ignore_error = out.flush();
+                        }
+                    }
+                }
+                other => {
+                    password.push(other);
+                    if asterisks {
+                        let _ignore_error = out.write_all("*".as_bytes());
+                        let _ignore_error = out.flush();
+                    }
+                }
+            }
+        }
+        Ok(())
+    });
+    if unsafe { libc::tcsetattr(infd, libc::TCSANOW, &old_termios) } != 0 {
+        // not fatal...
+        eprintln!("failed to reset terminal attributes!");
+    }
+    match ok {
+        Ok(_) => Ok(password),
+        Err(e) => Err(e),
+    }
+}