Correctly handle result data bounds

src/improv.rs

@@ -483,21 +483,34 @@ impl ImprovDataFromPacket for RPCResultPacket {
             return Err(anyhow!("Packet is not RPCResult"));
         }
 
+        // Byte 1
+        let command_responded_to = RPCCommand::try_from(&raw_packet.data[0]).context("Failed to determine RPC command this packet responds to")?;
+
+        // Byte 2
+        let result_data_len = usize::from(raw_packet.data[1]);
+
+        // Byte 3...
+        // slice the part of the raw_packet data that contains the result strings
+        let result_data = &raw_packet.data[2..result_data_len+2];
+        // the ESPHome implementation has a trailing nullbyte after the strings, so result_data
+        // ends before raw_packet.data, everything after that is ignored
+
+        // store result strings
         let mut results: Vec<String> = Vec::new();
 
-        let mut data_position: usize = 2;
+        let mut data_position: usize = 0;
         loop {
-            if data_position >= raw_packet.data.len() {
+            if data_position >= result_data.len() {
                 break;
             }
 
             // find string bounds
-            let current_string_len: usize = usize::from(raw_packet.data[data_position]);
+            let current_string_len: usize = usize::from(result_data[data_position]);
             let current_string_begin = data_position + 1;
             let current_string_end = data_position + current_string_len;
 
             // load string and append to results
-            let string_bytes = &raw_packet.data[current_string_begin..current_string_end+1];
+            let string_bytes = &result_data[current_string_begin..current_string_end+1];
             let string = std::str::from_utf8(string_bytes).context("Failed to convert response to UTF-8 string")?.to_string();
             results.push(string);
 
@@ -506,7 +519,7 @@ impl ImprovDataFromPacket for RPCResultPacket {
         }
 
         return Ok(Self {
-            command_responded_to: RPCCommand::try_from(&raw_packet.data[0]).context("Failed to determine RPC command this packet responds to")?,
+            command_responded_to: command_responded_to,
             results: results,
         })
     }