reduced max message buffer size, use pod_read_unaligned in some places

Author: Athryx

decoder/decoder/src/crypto.rs

@@ -1,5 +1,5 @@
 use crate::DecoderError;
-use bytemuck::{from_bytes, Pod, Zeroable};
+use bytemuck::{pod_read_unaligned, Pod, Zeroable};
 use chacha20poly1305::{AeadInPlace, KeyInit, XChaCha20Poly1305};
 use ed25519_dalek::{Signature, Verifier, VerifyingKey, SIGNATURE_LENGTH};
 use rand_chacha::ChaCha20Rng;
@@ -42,7 +42,7 @@ pub fn decrypt_decoder_payload<'a>(
         return Err(DecoderError::InvalidEncoderPayload);
     }
 
-    let header: DecoderPayloadHeader = *from_bytes(&payload[..size_of::<DecoderPayloadHeader>()]);
+    let header: DecoderPayloadHeader = pod_read_unaligned(&payload[..size_of::<DecoderPayloadHeader>()]);
 
     // first verify signature
     // signature should include chacha nonce and tag, otherwise attacker can alter nonce and get invalid frame
@@ -71,12 +71,12 @@ pub fn decrypt_decoder_payload<'a>(
 }
 
 /// Gets a reference to the associated data of the given decoder payload.
-pub fn get_decoder_payload_associated_data<T: Pod>(payload: &[u8]) -> Result<&T, DecoderError> {
+pub fn get_decoder_payload_associated_data<T: Pod>(payload: &[u8]) -> Result<T, DecoderError> {
     if payload.len() < size_of::<DecoderPayloadHeader>() + size_of::<T>() {
         Err(DecoderError::InvalidEncoderPayload)
     } else {
         let associated_data = &payload[payload.len() - size_of::<T>()..];
-        Ok(from_bytes(associated_data))
+        Ok(pod_read_unaligned(associated_data))
     }
 }
 

decoder/decoder/src/decode.rs

@@ -34,7 +34,7 @@ struct FrameData {
 
 /// Performs all functionality related to decoding frames.
 pub fn decode(context: &mut DecoderContext, encoded_frame: &mut [u8]) -> Result<(), DecoderError> {
-    let frame_info: FrameAssociatedData = *get_decoder_payload_associated_data(encoded_frame)?;
+    let frame_info: FrameAssociatedData = get_decoder_payload_associated_data(encoded_frame)?;
 
     // check frame we are decoding is monotonically increasing for security requirement 3
     if context
@@ -57,6 +57,7 @@ pub fn decode(context: &mut DecoderContext, encoded_frame: &mut [u8]) -> Result<
         &public_key,
     )?;
 
+    // shouldn't have alignmanet issues, frame data is 1 byte aligned
     let frame_data: &FrameData = try_from_bytes(frame_data)?;
 
     // decoding succeeded, update last decoded timestamp

decoder/decoder/src/message.rs

@@ -79,8 +79,8 @@ impl Opcode {
 }
 
 pub const MAGIC: u8 = b'%';
-// 5 KiB
-pub const MAX_BODY_SIZE: usize = 5120;
+// 4.5 KiB
+pub const MAX_BODY_SIZE: usize = 4608;
 const CHUNK_SIZE: usize = 256;
 
 /// Opcodes that don't require an ack response.

decoder/decoder/src/subscribe.rs

@@ -82,7 +82,7 @@ pub fn subscribe(
     context: &mut DecoderContext,
     subscribe_data: &mut [u8],
 ) -> Result<(), DecoderError> {
-    let associated_data: SubscriptionAssociatedData = *get_decoder_payload_associated_data(subscribe_data)?;
+    let associated_data: SubscriptionAssociatedData = get_decoder_payload_associated_data(subscribe_data)?;
     if associated_data.decoder_id != DECODER_ID {
         return Err(DecoderError::InvalidSubscription);
     }