Implement auto detection of encrypted root devices (fix #21)

src/storage/crypt.rs

@@ -2,10 +2,16 @@ use super::markers::BlockDevice;
 use crate::error::{Error, ErrorKind};
 use crate::process::CommandExt;
 use crate::tool::Tool;
+use failure::ResultExt;
 use log::{debug, warn};
+use std::fs;
+use std::io::Read;
 use std::marker::PhantomData;
 use std::path::{Path, PathBuf};
 
+static LUKS_MAGIC_1: &'static [u8] = &[0x4c, 0x55, 0x4b, 0x53, 0xba, 0xbe];
+static LUKS_MAGIC_2: &'static [u8] = &[0x53, 0x4b, 0x55, 0x4c, 0xba, 0xbe];
+
 #[derive(Debug)]
 pub struct EncryptedDevice<'t, 'o> {
     cryptsetup: &'t Tool,
@@ -78,3 +84,17 @@ impl<'t, 'o> BlockDevice for EncryptedDevice<'t, 'o> {
         &self.path
     }
 }
+
+pub fn is_encrypted_device(device: &BlockDevice) -> Result<bool, Error> {
+    let mut f = fs::OpenOptions::new()
+        .read(true)
+        .write(false)
+        .open(device.path())
+        .context(ErrorKind::LuksDetection)?;
+
+    let mut buffer = [0; 6];
+    f.read_exact(&mut buffer)
+        .context(ErrorKind::LuksDetection)?;
+
+    Ok(buffer == LUKS_MAGIC_1 || buffer == LUKS_MAGIC_2)
+}

src/storage/mod.rs

@@ -6,7 +6,7 @@ mod mount_stack;
 mod partition;
 mod storage_device;
 
-pub use crypt::EncryptedDevice;
+pub use crypt::{is_encrypted_device, EncryptedDevice};
 pub use filesystem::{Filesystem, FilesystemType};
 pub use loop_device::LoopDevice;
 pub use markers::BlockDevice;