Rust now integrated into bcachefs binary

Rust is now required for building the bcachefs tool, and rust code is
now fully integrated with the C codebase - meaning it is possible to
call back and forth.

The mount helper is now a subcommand, 'mount.bcachefs' is now a small
shell wrapper that invokes 'bcachefs mount'.

This will make it easier to start rewriting other subcommands in rust,
and eventually the whole command line interface.

Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>

1 files changed, 124 insertions, 0 deletions

diff --git a/rust-src/src/key.rs b/rust-src/src/key.rs
new file mode 100644
index 00000000..e2d0e4c0
--- /dev/null
+++ b/rust-src/src/key.rs
@@ -0,0 +1,124 @@
+use bch_bindgen::info;
+use colored::Colorize;
+use crate::c_str;
+use anyhow::anyhow;
+
+#[derive(Clone, Debug)]
+pub enum KeyLocation {
+    Fail,
+    Wait,
+    Ask,
+}
+
+#[derive(Clone, Debug)]
+pub struct KeyLoc(pub Option<KeyLocation>);
+impl std::ops::Deref for KeyLoc {
+    type Target = Option<KeyLocation>;
+    fn deref(&self) -> &Self::Target {
+        &self.0
+    }
+}
+
+impl std::str::FromStr for KeyLoc {
+    type Err = anyhow::Error;
+    fn from_str(s: &str) -> anyhow::Result<Self> {
+        match s {
+            "" => Ok(KeyLoc(None)),
+            "fail" => Ok(KeyLoc(Some(KeyLocation::Fail))),
+            "wait" => Ok(KeyLoc(Some(KeyLocation::Wait))),
+            "ask" => Ok(KeyLoc(Some(KeyLocation::Ask))),
+            _ => Err(anyhow!("invalid password option")),
+        }
+    }
+}
+
+fn check_for_key(key_name: &std::ffi::CStr) -> anyhow::Result<bool> {
+    use bch_bindgen::keyutils::{self, keyctl_search};
+    let key_name = key_name.to_bytes_with_nul().as_ptr() as *const _;
+    let key_type = c_str!("logon");
+
+    let key_id = unsafe { keyctl_search(keyutils::KEY_SPEC_USER_KEYRING, key_type, key_name, 0) };
+    if key_id > 0 {
+        info!("Key has became available");
+        Ok(true)
+    } else if errno::errno().0 != libc::ENOKEY {
+        Err(crate::ErrnoError(errno::errno()).into())
+    } else {
+        Ok(false)
+    }
+}
+
+fn wait_for_key(uuid: &uuid::Uuid) -> anyhow::Result<()> {
+    let key_name = std::ffi::CString::new(format!("bcachefs:{}", uuid)).unwrap();
+    loop {
+        if check_for_key(&key_name)? {
+            break Ok(());
+        }
+
+        std::thread::sleep(std::time::Duration::from_secs(1));
+    }
+}
+
+const BCH_KEY_MAGIC: &str = "bch**key";
+use crate::filesystem::FileSystem;
+fn ask_for_key(fs: &FileSystem) -> anyhow::Result<()> {
+    use bch_bindgen::bcachefs::{self, bch2_chacha_encrypt_key, bch_encrypted_key, bch_key};
+    use byteorder::{LittleEndian, ReadBytesExt};
+    use std::os::raw::c_char;
+
+    let key_name = std::ffi::CString::new(format!("bcachefs:{}", fs.uuid())).unwrap();
+    if check_for_key(&key_name)? {
+        return Ok(());
+    }
+
+    let bch_key_magic = BCH_KEY_MAGIC.as_bytes().read_u64::<LittleEndian>().unwrap();
+    let crypt = fs.sb().sb().crypt().unwrap();
+    let pass = rpassword::read_password_from_tty(Some("Enter passphrase: "))?;
+    let pass = std::ffi::CString::new(pass.trim_end())?; // bind to keep the CString alive
+    let mut output: bch_key = unsafe {
+        bcachefs::derive_passphrase(
+            crypt as *const _ as *mut _,
+            pass.as_c_str().to_bytes_with_nul().as_ptr() as *const _,
+        )
+    };
+
+    let mut key = crypt.key().clone();
+    let ret = unsafe {
+        bch2_chacha_encrypt_key(
+            &mut output as *mut _,
+            fs.sb().sb().nonce(),
+            &mut key as *mut _ as *mut _,
+            std::mem::size_of::<bch_encrypted_key>() as usize,
+        )
+    };
+    if ret != 0 {
+        Err(anyhow!("chacha decryption failure"))
+    } else if key.magic != bch_key_magic {
+        Err(anyhow!("failed to verify the password"))
+    } else {
+        let key_type = c_str!("logon");
+        let ret = unsafe {
+            bch_bindgen::keyutils::add_key(
+                key_type,
+                key_name.as_c_str().to_bytes_with_nul() as *const _ as *const c_char,
+                &output as *const _ as *const _,
+                std::mem::size_of::<bch_key>() as usize,
+                bch_bindgen::keyutils::KEY_SPEC_USER_KEYRING,
+            )
+        };
+        if ret == -1 {
+            Err(anyhow!("failed to add key to keyring: {}", errno::errno()))
+        } else {
+            Ok(())
+        }
+    }
+}
+
+pub fn prepare_key(fs: &FileSystem, password: KeyLocation) -> anyhow::Result<()> {
+    info!("checking if key exists for filesystem {}", fs.uuid());
+    match password {
+        KeyLocation::Fail => Err(anyhow!("no key available")),
+        KeyLocation::Wait => Ok(wait_for_key(fs.uuid())?),
+        KeyLocation::Ask => ask_for_key(fs),
+    }
+}