Merge pull request #107 from chrysn-pull-requests/coap-example-using-…

…coap-handler

Add example / implementation for coap-handler

.github/workflows/build-and-test.yml

@@ -185,6 +185,9 @@ jobs:
     - name: Build client
       run: cargo build --bin coapclient
 
+    - name: Build coap-handler based server
+      run: cargo build --bin coapserver-coaphandler
+
 
   release:
     runs-on: ubuntu-latest

examples/coap/Cargo.toml

@@ -8,3 +8,11 @@ edhoc-rs = { path = "../../lib", features = [ "crypto-hacspec" ] }
 hexlit = "0.5.3"
 coap = { version = "0.13" }
 coap-lite = { version = "0.11.3" }
+
+std-embedded-nal = "^0.1.2"
+embedded-nal-minimal-coapserver = "0.3.1"
+embedded-nal = "0.6"
+coap-message = "0.2.3"
+coap-handler = "0.1.5"
+coap-handler-implementations = "0.4.2"
+coap-numbers = "0.2.3"

examples/coap/src/bin/coapserver-coaphandler.rs

@@ -0,0 +1,159 @@
+use edhoc_rs::*;
+use hexlit::hex;
+use std::net::UdpSocket;
+
+use embedded_nal::UdpFullStack;
+
+const ID_CRED_I: &[u8] = &hex!("a104412b");
+const ID_CRED_R: &[u8] = &hex!("a104410a");
+const CRED_I: &[u8] = &hex!("A2027734322D35302D33312D46462D45462D33372D33322D333908A101A5010202412B2001215820AC75E9ECE3E50BFC8ED60399889522405C47BF16DF96660A41298CB4307F7EB62258206E5DE611388A4B8A8211334AC7D37ECB52A387D257E6DB3C2A93DF21FF3AFFC8");
+const G_I: &[u8] = &hex!("ac75e9ece3e50bfc8ed60399889522405c47bf16df96660a41298cb4307f7eb6"); // not used
+const _G_I_Y_COORD: &[u8] =
+    &hex!("6e5de611388a4b8a8211334ac7d37ecb52a387d257e6db3c2a93df21ff3affc8"); // not used
+const CRED_R: &[u8] = &hex!("A2026008A101A5010202410A2001215820BBC34960526EA4D32E940CAD2A234148DDC21791A12AFBCBAC93622046DD44F02258204519E257236B2A0CE2023F0931F1F386CA7AFDA64FCDE0108C224C51EABF6072");
+const R: &[u8] = &hex!("72cc4761dbd4c78f758931aa589d348d1ef874a7e303ede2f140dcf3e6aa4aac");
+
+#[derive(Default, Debug)]
+struct EdhocHandler {
+    connections: Vec<(u8, EdhocResponder<'static>)>,
+}
+
+impl EdhocHandler {
+    fn connection_by_c_r(&mut self, c_r: u8) -> Option<&mut EdhocResponder<'static>> {
+        self.connections
+            .iter_mut()
+            .filter(|(current_c_r, _)| current_c_r == &c_r)
+            .map(|(_, responder)| responder)
+            .next()
+    }
+
+    fn new_c_r(&self) -> u8 {
+        // FIXME: We'll need to do better, but a) that'll be more practical when we can do more
+        // than u8, and b) that'll best be coordinated with a storage that not only stores EDHOC
+        // contexts but also OSCORE ones.
+        let result = self.connections.len();
+        if result >= 24 {
+            panic!("Contexts exceeded");
+        }
+        result as _
+    }
+}
+
+enum EdhocResponse {
+    OkSend2 { c_r: u8 },
+    Message3Processed,
+}
+
+impl coap_handler::Handler for EdhocHandler {
+    type RequestData = EdhocResponse;
+    fn extract_request_data(
+        &mut self,
+        request: &impl coap_message::ReadableMessage,
+    ) -> Self::RequestData {
+        let starts_with_true = request.payload().get(0) == Some(&0xf5);
+
+        if starts_with_true {
+            let state = EdhocState::default();
+            let mut responder = EdhocResponder::new(state, &R, &CRED_R, Some(&CRED_I));
+
+            let error = responder
+                .process_message_1(&request.payload()[1..].try_into().expect("wrong length"));
+
+            if error.is_ok() {
+                let c_r = self.new_c_r();
+                // save edhoc connection
+                self.connections.push((c_r, responder));
+                EdhocResponse::OkSend2 { c_r }
+            } else {
+                panic!("How to respond to non-OK?")
+            }
+        } else {
+            // potentially message 3
+            let c_r_rcvd = request.payload()[0];
+            let mut responder = self.connection_by_c_r(c_r_rcvd).expect("No such C_R found");
+
+            println!("Found state with connection identifier {:?}", c_r_rcvd);
+            let prk_out = responder
+                .process_message_3(&request.payload()[1..].try_into().expect("wrong length"));
+
+            if prk_out.is_err() {
+                println!("EDHOC processing error: {:?}", prk_out);
+                // FIXME remove state from edhoc_connections
+                panic!("Handler can't just not respond");
+            }
+
+            println!("EDHOC exchange successfully completed");
+            println!("PRK_out: {:02x?}", prk_out);
+
+            let mut _oscore_secret = responder.edhoc_exporter(0u8, &[], 16).unwrap(); // label is 0
+            println!("OSCORE secret: {:02x?}", _oscore_secret);
+            let mut _oscore_salt = responder.edhoc_exporter(1u8, &[], 8).unwrap(); // label is 1
+            println!("OSCORE salt: {:02x?}", _oscore_salt);
+
+            // context of key update is a test vector from draft-ietf-lake-traces
+            let prk_out_new = responder.edhoc_key_update(&[
+                0xa0, 0x11, 0x58, 0xfd, 0xb8, 0x20, 0x89, 0x0c, 0xd6, 0xbe, 0x16, 0x96, 0x02, 0xb8,
+                0xbc, 0xea,
+            ]);
+            println!("PRK_out after key update: {:02x?}?", prk_out_new);
+
+            _oscore_secret = responder.edhoc_exporter(0u8, &[], 16).unwrap(); // label is 0
+            println!("OSCORE secret after key update: {:02x?}", _oscore_secret);
+            _oscore_salt = responder.edhoc_exporter(1u8, &[], 8).unwrap(); // label is 1
+            println!("OSCORE salt after key update: {:02x?}", _oscore_salt);
+
+            EdhocResponse::Message3Processed
+        }
+    }
+    fn estimate_length(&mut self, _: &Self::RequestData) -> usize {
+        200
+    }
+    fn build_response(
+        &mut self,
+        response: &mut impl coap_message::MutableWritableMessage,
+        req: Self::RequestData,
+    ) {
+        response.set_code(coap_numbers::code::CHANGED.try_into().ok().unwrap());
+        match req {
+            EdhocResponse::OkSend2 { c_r } => {
+                let responder = self.connection_by_c_r(c_r).unwrap();
+                let message_2 = responder.prepare_message_2(c_r).unwrap();
+                response.set_payload(&message_2.content[..message_2.len]);
+            }
+            EdhocResponse::Message3Processed => (), // "send empty ack back"?
+        };
+    }
+}
+
+fn build_handler() -> impl coap_handler::Handler {
+    use coap_handler_implementations::{HandlerBuilder, ReportingHandlerBuilder};
+
+    let mut edhoc: EdhocHandler = Default::default();
+
+    coap_handler_implementations::new_dispatcher()
+        .at_with_attributes(&[".well-known", "edhoc"], &[], edhoc)
+        .with_wkc()
+}
+
+fn main_on_stack<S: UdpFullStack>(stack: &mut S) {
+    let mut sock = stack.socket().expect("Can't create a socket");
+
+    let mut handler = build_handler();
+
+    stack.bind(&mut sock, 5683).expect("Can't bind to port");
+
+    loop {
+        match embedded_nal_minimal_coapserver::poll(stack, &mut sock, &mut handler) {
+            Err(embedded_nal::nb::Error::WouldBlock) => {
+                // See <https://github.com/rust-embedded-community/embedded-nal/issues/47>
+                std::thread::sleep(std::time::Duration::from_millis(50));
+            }
+            e => e.expect("UDP error during send/receive"),
+        }
+    }
+}
+
+fn main() {
+    let mut stack = std_embedded_nal::Stack::default();
+    main_on_stack(&mut stack);
+}