chore: seed sgclaw rust baseline

src/pipe/handshake.rs

@@ -0,0 +1,53 @@
+use std::time::Duration;
+
+use uuid::Uuid;
+
+use crate::pipe::protocol::{supported_actions, AgentMessage, BrowserMessage, PROTOCOL_VERSION};
+use crate::pipe::{PipeError, Transport};
+use crate::security::derive_session_key;
+
+#[derive(Debug, Clone)]
+pub struct HandshakeResult {
+    pub agent_id: String,
+    pub session_key: Vec<u8>,
+    pub capabilities: Vec<String>,
+}
+
+pub fn perform_handshake<T: Transport>(
+    transport: &T,
+    timeout: Duration,
+) -> Result<HandshakeResult, PipeError> {
+    let init = transport.recv_timeout(timeout)?;
+
+    match init {
+        BrowserMessage::Init {
+            version,
+            hmac_seed,
+            capabilities,
+        } => {
+            if version != PROTOCOL_VERSION {
+                return Err(PipeError::Protocol(format!(
+                    "unsupported protocol version: {version}"
+                )));
+            }
+
+            let session_key = derive_session_key(&hmac_seed)?;
+            let agent_id = Uuid::new_v4().to_string();
+            let ack = AgentMessage::InitAck {
+                version: PROTOCOL_VERSION.to_string(),
+                agent_id: agent_id.clone(),
+                supported_actions: supported_actions(),
+            };
+            transport.send(&ack)?;
+
+            Ok(HandshakeResult {
+                agent_id,
+                session_key,
+                capabilities,
+            })
+        }
+        other => Err(PipeError::UnexpectedMessage(format!(
+            "expected init as first message, got {other:?}"
+        ))),
+    }
+}