🔒 Fix potential memory exhaustion in socket reads (#59)

Addresses a security vulnerability where the daemon or client could be
forced to allocate up to 10MB of memory per malformed socket message,
potentially leading to Out-Of-Memory (OOM) crashes.

Changes:
- Introduced a central `MAX_MESSAGE_SIZE` constant of 128KB in `src/types/socket.rs`.
- Enforced the 128KB limit on incoming requests in `src/bin/daemon.rs`.
- Enforced the 128KB limit on incoming responses in `src/utils/daemon.rs`.
- Preserved detailed `eprintln!` logging when messages are rejected.

Co-authored-by: google-labs-jules[bot] <161369871+google-labs-jules[bot]@users.noreply.github.com>

src/bin/daemon.rs

@@ -1,5 +1,5 @@
 use pwsp::{
-    types::socket::{Request, Response},
+    types::socket::{Request, Response, MAX_MESSAGE_SIZE},
     utils::{
         commands::parse_command,
         daemon::{
@@ -109,7 +109,7 @@ async fn commands_loop(listener: UnixListener) -> Result<(), Box<dyn Error>> {
 
             let request_len = u32::from_le_bytes(len_bytes) as usize;
 
-            if request_len > 10 * 1024 * 1024 {
+            if request_len > MAX_MESSAGE_SIZE {
                 eprintln!(
                     "Failed to read message from client: request too large ({} bytes)!",
                     request_len

src/types/socket.rs

@@ -1,6 +1,8 @@
 use serde::{Deserialize, Serialize};
 use std::collections::HashMap;
 
+pub const MAX_MESSAGE_SIZE: usize = 128 * 1024;
+
 #[derive(Default, Debug, Clone, Serialize, Deserialize, PartialEq)]
 pub struct Request {
     pub name: String,

src/utils/daemon.rs

@@ -2,7 +2,7 @@ use crate::{
     types::{
         audio_player::AudioPlayer,
         config::DaemonConfig,
-        socket::{Request, Response},
+        socket::{Request, Response, MAX_MESSAGE_SIZE},
     },
     utils::pipewire::{create_link, get_device},
 };
@@ -135,6 +135,14 @@ pub async fn make_request(request: Request) -> Result<Response, Box<dyn Error +
     }
     let response_len = u32::from_le_bytes(len_bytes) as usize;
 
+    if response_len > MAX_MESSAGE_SIZE {
+        eprintln!(
+            "Failed to read response from daemon: response too large ({} bytes)!",
+            response_len
+        );
+        return Err("Response too large".into());
+    }
+
     let mut buffer = vec![0u8; response_len];
     if stream.read_exact(&mut buffer).await.is_err() {
         return Err("Failed to read response".into());