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use std::{
ffi::{c_long, CStr, CString},
fs,
io::{stdin, IsTerminal},
mem,
path::Path,
ptr, thread,
time::Duration,
};
use anyhow::{anyhow, ensure, Result};
use bch_bindgen::{
bcachefs::{self, bch_key, bch_sb_handle},
c::{bch2_chacha_encrypt_key, bch_sb_field_crypt},
keyutils::{self, keyctl_search},
};
use byteorder::{LittleEndian, ReadBytesExt};
use log::info;
use uuid::Uuid;
use zeroize::{ZeroizeOnDrop, Zeroizing};
use crate::{c_str, ErrnoError};
const BCH_KEY_MAGIC: &str = "bch**key";
#[derive(Clone, Debug, clap::ValueEnum, strum::Display)]
pub enum UnlockPolicy {
Fail,
Wait,
Ask,
}
impl UnlockPolicy {
pub fn apply(&self, sb: &bch_sb_handle) -> Result<KeyHandle> {
let uuid = sb.sb().uuid();
info!("Using filesystem unlock policy '{self}' on {uuid}");
match self {
Self::Fail => Err(anyhow!("no passphrase available")),
Self::Wait => Ok(KeyHandle::wait_for_unlock(&uuid)?),
Self::Ask => Passphrase::new_from_prompt().and_then(|p| KeyHandle::new(sb, &p)),
}
}
}
impl Default for UnlockPolicy {
fn default() -> Self {
Self::Ask
}
}
/// A handle to an existing bcachefs key in the kernel keyring
pub struct KeyHandle {
// FIXME: Either these come in useful for something or we remove them
_uuid: Uuid,
_id: c_long,
}
impl KeyHandle {
pub fn format_key_name(uuid: &Uuid) -> CString {
CString::new(format!("bcachefs:{uuid}")).unwrap()
}
pub fn new(sb: &bch_sb_handle, passphrase: &Passphrase) -> Result<Self> {
let bch_key_magic = BCH_KEY_MAGIC.as_bytes().read_u64::<LittleEndian>().unwrap();
let crypt = sb.sb().crypt().unwrap();
let crypt_ptr = (crypt as *const bch_sb_field_crypt).cast_mut();
let mut output: bch_key =
unsafe { bcachefs::derive_passphrase(crypt_ptr, passphrase.get().as_ptr()) };
let mut key = *crypt.key();
let ret = unsafe {
bch2_chacha_encrypt_key(
ptr::addr_of_mut!(output),
sb.sb().nonce(),
ptr::addr_of_mut!(key).cast(),
mem::size_of_val(&key),
)
};
ensure!(ret == 0, "chacha decryption failure");
ensure!(key.magic == bch_key_magic, "failed to verify passphrase");
let key_name = Self::format_key_name(&sb.sb().uuid());
let key_name = CStr::as_ptr(&key_name);
let key_type = c_str!("user");
let key_id = unsafe {
keyutils::add_key(
key_type,
key_name,
ptr::addr_of!(output).cast(),
mem::size_of_val(&output),
keyutils::KEY_SPEC_USER_KEYRING,
)
};
if key_id > 0 {
info!("Found key in keyring");
Ok(KeyHandle {
_uuid: sb.sb().uuid(),
_id: c_long::from(key_id),
})
} else {
Err(anyhow!("failed to add key to keyring: {}", errno::errno()))
}
}
pub fn new_from_search(uuid: &Uuid) -> Result<Self> {
let key_name = Self::format_key_name(uuid);
let key_name = CStr::as_ptr(&key_name);
let key_type = c_str!("user");
let key_id =
unsafe { keyctl_search(keyutils::KEY_SPEC_USER_KEYRING, key_type, key_name, 0) };
if key_id > 0 {
info!("Found key in keyring");
Ok(Self {
_uuid: *uuid,
_id: key_id,
})
} else {
Err(ErrnoError(errno::errno()).into())
}
}
fn wait_for_unlock(uuid: &Uuid) -> Result<Self> {
loop {
match Self::new_from_search(uuid) {
Err(_) => thread::sleep(Duration::from_secs(1)),
r => break r,
}
}
}
}
#[derive(ZeroizeOnDrop)]
pub struct Passphrase(CString);
impl Passphrase {
fn get(&self) -> &CStr {
&self.0
}
// blocks indefinitely if no input is available on stdin
fn new_from_prompt() -> Result<Self> {
let passphrase = if stdin().is_terminal() {
Zeroizing::new(rpassword::prompt_password("Enter passphrase: ")?)
} else {
info!("Trying to read passphrase from stdin...");
let mut line = Zeroizing::new(String::new());
stdin().read_line(&mut line)?;
line
};
Ok(Self(CString::new(passphrase.as_str())?))
}
pub fn new_from_file(sb: &bch_sb_handle, passphrase_file: impl AsRef<Path>) -> Result<Self> {
let passphrase_file = passphrase_file.as_ref();
info!(
"Attempting to unlock key for filesystem {} with passphrase from file {}",
sb.sb().uuid(),
passphrase_file.display()
);
let passphrase = Zeroizing::new(fs::read_to_string(passphrase_file)?);
Ok(Self(CString::new(passphrase.as_str())?))
}
}
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