src/backup/crypt_config.rs: make code more flexible

Allow to pass magic numbers as parameters.

src/backup/crypt_config.rs

@@ -64,7 +64,18 @@ impl CryptConfig {
     /// Compress and encrypt data using a random 16 byte IV.
     ///
     /// Return the encrypted data, including IV and MAC (MAGIC || IV || MAC || ENC_DATA).
-    pub fn encode_chunk(&self, data: &[u8], compress: bool) -> Result<Vec<u8>, Error> {
+    /// If compression does not help, we return the uncompresssed, encrypted data.
+    pub fn encode_chunk(
+        &self,
+        // The data you want to encode
+        data: &[u8],
+        // Whether try to compress data before encryption
+        compress: bool,
+        // Magic number used for uncompressed results
+        uncomp_magic: &[u8; 8],
+        // Magic number used for compressed results
+        comp_magic: &[u8; 8],
+    ) -> Result<Vec<u8>, Error> {
 
         let iv = proxmox::sys::linux::random_data(16)?;
         let mut c = Crypter::new(self.cipher, Mode::Encrypt, &self.enc_key, Some(&iv))?;
@@ -76,7 +87,7 @@ impl CryptConfig {
             if compr_data.len() < data.len() {
                 let mut enc = vec![0; compr_data.len()+40+self.cipher.block_size()];
 
-                enc[0..8].copy_from_slice(&super::ENCR_COMPR_CHUNK_MAGIC_1_0);
+                enc[0..8].copy_from_slice(comp_magic);
                 enc[8..24].copy_from_slice(&iv);
 
                 let count = c.update(&compr_data, &mut enc[40..])?;
@@ -91,7 +102,7 @@ impl CryptConfig {
 
         let mut enc = vec![0; data.len()+40+self.cipher.block_size()];
 
-        enc[0..8].copy_from_slice(&super::ENCRYPTED_CHUNK_MAGIC_1_0);
+        enc[0..8].copy_from_slice(uncomp_magic);
         enc[8..24].copy_from_slice(&iv);
 
         let count = c.update(data, &mut enc[40..])?;
@@ -105,19 +116,18 @@ impl CryptConfig {
 
     /// Decompress and decrypt chunk, verify MAC.
     ///
-    /// Binrary ``data`` is expected to be in format returned by encode_chunk.
+    /// Binrary ``data`` is expected to be in format returned by encode_chunk. The magic number
-    pub fn decode_chunk(&self, data: &[u8]) -> Result<Vec<u8>, Error> {
+    /// is not used here.
+    pub fn decode_compressed_chunk(&self, data: &[u8]) -> Result<Vec<u8>, Error> {
 
         if data.len() < 40 {
             bail!("Invalid chunk len (<40)");
         }
 
-        let magic = &data[0..8];
+        // let magic = &data[0..8];
         let iv = &data[8..24];
         let mac = &data[24..40];
 
-        if magic == super::ENCR_COMPR_CHUNK_MAGIC_1_0 {
-
         let dec = Vec::with_capacity(1024*1024);
 
         let mut decompressor = zstd::stream::write::Decoder::new(dec)?;
@@ -149,9 +159,23 @@ impl CryptConfig {
 
         decompressor.flush()?;
 
-            return Ok(decompressor.into_inner());
+        Ok(decompressor.into_inner())
+    }
+
+    /// Decrypt chunk, verify MAC.
+    ///
+    /// Binrary ``data`` is expected to be in format returned by encode_chunk. The magic number
+    /// is not used here.
+    pub fn decode_uncompressed_chunk(&self, data: &[u8]) -> Result<Vec<u8>, Error> {
+
+        if data.len() < 40 {
+            bail!("Invalid chunk len (<40)");
+        }
+
+        // let magic = &data[0..8];
+        let iv = &data[8..24];
+        let mac = &data[24..40];
 
-        } else if magic == super::ENCRYPTED_CHUNK_MAGIC_1_0 {
         let decr_data = decrypt_aead(
             self.cipher,
             &self.enc_key,
@@ -160,9 +184,7 @@ impl CryptConfig {
             &data[40..],
             mac,
         )?;
-            return Ok(decr_data);
+
-        } else {
+        Ok(decr_data)
-            bail!("Invalid magic number (expected encrypted chunk).");
-        }
     }
 }

src/backup/data_chunk.rs

@@ -66,7 +66,12 @@ impl DataChunk {
 
         if let Some(config) = config {
 
-            let enc_data = config.encode_chunk(data, compress)?;
+            let enc_data = config.encode_chunk(
+                data,
+                compress,
+                &ENCRYPTED_CHUNK_MAGIC_1_0,
+                &ENCR_COMPR_CHUNK_MAGIC_1_0,
+            )?;
             let chunk = DataChunk { digest, raw_data: enc_data };
 
             Ok(chunk)
@@ -108,8 +113,11 @@ impl DataChunk {
 
         } else if magic == &ENCR_COMPR_CHUNK_MAGIC_1_0 || magic == &ENCRYPTED_CHUNK_MAGIC_1_0 {
             if let Some(config) = config  {
-                let data = config.decode_chunk(&self.raw_data)?;
+                let data = if magic == &ENCR_COMPR_CHUNK_MAGIC_1_0 {
-
+                    config.decode_compressed_chunk(&self.raw_data)?
+                } else {
+                    config.decode_uncompressed_chunk(&self.raw_data)?
+                };
                 return Ok(data);
             } else {
                 bail!("unable to decrypt chunk - missing CryptConfig");