refactor: use strum on EncryptionAlgorithm, use Xor as default when AesGcm not available (#1923)

easytier/src/peers/peer_session.rs

@@ -8,17 +8,17 @@ use std::{
 
 use atomic_shim::AtomicU64;
 
+use crate::{
+    common::PeerId,
+    peers::encrypt::{create_encryptor, Encryptor},
+    tunnel::packet_def::{StandardAeadTail, ZCPacket},
+};
 use anyhow::anyhow;
 use dashmap::DashMap;
 use hmac::{Hmac, Mac as _};
 use rand::RngCore as _;
 use sha2::Sha256;
-
-use crate::{
-    common::PeerId,
-    peers::encrypt::{create_encryptor, Encryptor},
-    tunnel::packet_def::{AesGcmTail, ZCPacket},
-};
+use zerocopy::FromBytes;
 
 type HmacSha256 = Hmac<Sha256>;
 pub struct UpsertResponderSessionReturn {
@@ -733,14 +733,8 @@ impl PeerSession {
     }
 
     fn parse_tail(payload: &[u8]) -> Option<[u8; 12]> {
-        if payload.len() < std::mem::size_of::<AesGcmTail>() {
-            return None;
-        }
-        let tail_off = payload.len() - std::mem::size_of::<AesGcmTail>();
-        let tail = &payload[tail_off..];
-        let mut nonce = [0u8; 12];
-        nonce.copy_from_slice(&tail[16..]);
-        Some(nonce)
+        let tail = StandardAeadTail::ref_from_suffix(payload)?;
+        Some(tail.nonce)
     }
 
     fn evict_old_rx_slots(rx: &mut [[EpochRxSlot; 2]; 2], now_ms: u64) {