Adding function to perform bcachfs unlock.

src/nyan_system.rs

@@ -135,6 +135,52 @@ pub fn list_gpt_labeled_devs() -> Result<Vec<String>, ExecCommandError> {
     Ok(res)
 }
 
+/// bcachefs unlock --file=/tmp/bzzpsspass.txt /dev/loop0somedev
+/// Ok so. It is stupid, because bcacheutils far from ideal.
+/// But if we provide wrong password from file or stdin this stuff plays stupid and asks for right password.
+/// Sooo.. In order to know if unlock was sucessfull we need to check if program exited with Ok status,
+/// or it shits to STDERR still waiting for stdin
+/// Returns true if unlock successful, and false otherwise
+pub fn bcachefs_unlock(pass: String, dev: &str) -> Result<bool, ExecCommandError> {
+    use std::io::Read;
+    use std::io::Write;
+    use std::process::Stdio;
+    let mut child = Command::new("bcachefs")
+        .arg("unlock")
+        .arg(dev)
+        .stdin(Stdio::piped())
+        .stdout(Stdio::piped())
+        .stderr(Stdio::piped())
+        .spawn()?;
+
+    let mut c_stderr = child.stderr.take().ok_or_else(||{"Unable to get child process STDERR".to_string()})?;
+
+    // Write password to STDIN in a limited scope
+    {
+        let mut c_stdin = child.stdin.take().ok_or_else(||{"Unable to get child process STDIN".to_string()})?;
+        // neccessery to use thread or we may be deadlocking
+        c_stdin.write_all(pass.as_bytes())?;
+        let bytes_written = c_stdin.write(b"\n")?;
+        println!("bytes_written: {}", bytes_written);
+        // stdin is dropped here automatically when the block ends
+    }
+
+    let mut buffer = [0u8; 10];
+    // This blocks.
+    // if unlok fails it reads 10 bytes (piece of err message)
+    // if sucess it reads 0 bytes and exit
+    let read_b = c_stderr.read(&mut buffer)?;
+    if read_b > 0 {
+        println!("STDERR error not empty, password incorrect! Try to kill a child.");
+        child.kill()?;
+    }
+
+    // Safe to wait now; child will see EOF
+    let exit_status = child.wait()?;
+    // if exit status is SUCCESS - unloking is successful
+    Ok(exit_status.success()) 
+}
+
 /// Cheking if device is encripted
 pub fn bzzpss_dev_encrypted(dev_name: &str) -> Result<bool, ExecCommandError> {
     match exec_command("bcachefs", &vec!["unlock", "--check"]) {