encryption: encryption may corrupt data when partial write

[YuJuncen]

Bug Report

What version of TiKV are you using?

Current Master.

What operating system and CPU are you using?

Linux, x86_64.

Steps to reproduce

Apply the following patch (based on a5f1a26d3bb5121a845f644b5eebff3d6c041278):

Patch Content

+++ b/components/encryption/src/io.rs
@@ -525,6 +525,18 @@ mod tests {
         key
     }
 
+    struct Throttle<W>(W);
+
+    impl<W: Write> Write for Throttle<W> {
+        fn write(&mut self, buf: &[u8]) -> IoResult<usize> {
+            self.0.write(&buf[..2.min(buf.len())])
+        }
+
+        fn flush(&mut self) -> IoResult<()> {
+            Ok(())
+        }
+    }
+
     #[test]
     fn test_decrypt_encrypted_text() {
         let methods = [
@@ -557,10 +569,10 @@ mod tests {
                 let mut plaintext = vec![0; 1024];
                 OsRng.fill_bytes(&mut plaintext);
                 let buf = Vec::with_capacity(1024);
-                let mut encrypter = EncrypterWriter::new(buf, method, &key, iv).unwrap();
+                let mut encrypter = EncrypterWriter::new(Throttle(buf), method, &key, iv).unwrap();
                 encrypter.write_all(&plaintext).unwrap();
 
-                let buf = encrypter.finalize().unwrap();
+                let buf = encrypter.finalize().unwrap().0;
                 // Make sure it's properly encrypted.
                 if method != EncryptionMethod::Plaintext {
                     assert_ne!(buf, plaintext);

Then, run the test case test_decrypt_encrypted_text.

What did you expect?

The case should pass.

What did happened?

---- io::tests::test_decrypt_encrypted_text stdout ----
thread 'io::tests::test_decrypt_encrypted_text' panicked at 'assertion failed: `(left == right)`
  left: `[122, 11, 30, 119, 4]`,
 right: `[122, 11, 66, 84, 249]`', components/encryption/src/io.rs:589:21

[YuJuncen]

This is probably because some of the block encryption method(includes AES256, if I have rightly understood it.) requires the integrity of the encrypted block. But the current Write implementation doesn't make sure the integrity of data written.

tikv/components/encryption/src/io.rs

Lines 333 to 338 in a5f1a26

	fn write(&mut self, buf: &[u8]) -> IoResult<usize> {
	if let Some(crypter) = self.crypter.as_mut() {
	let crypted = crypter.do_crypter(buf)?;
	debug_assert!(crypted.len() == buf.len());
	self.writer.write(crypted)
	} else {

When L337 writes partial of the content, the encrypted block will be partial. The counter of CTR mode may contribute to this problem too. (What if some blocks are skipped? they will be lost in the sequence generated by the counter.)