Use serde_jcs for RFC 8785 compliancy

This fixes serialization and reduces maintainance cost, but does more
data copying on serialization.

Cargo.lock

@@ -259,11 +259,12 @@ dependencies = [
  "ed25519-dalek",
  "hex",
  "html-escape",
+ "rand",
  "rand_core",
  "rusqlite",
  "serde",
+ "serde_jcs",
  "serde_json",
- "syn",
  "uuid",
 ]
 
@@ -1392,6 +1393,12 @@ version = "1.0.18"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "f3cb5ba0dc43242ce17de99c180e96db90b235b8a9fdc9543c96d2209116bd9f"
 
+[[package]]
+name = "ryu-js"
+version = "0.2.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "6518fc26bced4d53678a22d6e423e9d8716377def84545fe328236e3af070e7f"
+
 [[package]]
 name = "schannel"
 version = "0.1.23"
@@ -1478,6 +1485,17 @@ dependencies = [
  "syn",
 ]
 
+[[package]]
+name = "serde_jcs"
+version = "0.1.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "cacecf649bc1a7c5f0e299cc813977c6a78116abda2b93b1ee01735b71ead9a8"
+dependencies = [
+ "ryu-js",
+ "serde",
+ "serde_json",
+]
+
 [[package]]
 name = "serde_json"
 version = "1.0.127"

Cargo.toml

@@ -18,11 +18,10 @@ bitflags_serde_shim = "0.2"
 ed25519-dalek = "2.1"
 hex = { version = "0.4", features = ["serde"] }
 html-escape = "0.2"
+rand = "0.8.5"
 rand_core = "0.6"
 rusqlite = { version = "0.32", optional = true }
 serde = { version = "1", features = ["derive"] }
+serde_jcs = "0.1"
 serde_json = "1"
 uuid = { version = "1", features = ["serde"] }
-
-[dev-dependencies]
-syn = { version = "2.0.76", features = ["full", "visit"] }

blahctl/src/main.rs

@@ -5,8 +5,8 @@ use std::{fs, io};
 use anyhow::{Context, Result};
 use blah::bitflags;
 use blah::types::{
-    ChatPayload, CreateRoomPayload, MemberPermission, RichText, RoomAttrs, RoomMember,
+    get_timestamp, ChatPayload, CreateRoomPayload, MemberPermission, RichText, RoomAttrs,
-    RoomMemberList, ServerPermission, UserKey, WithSig,
+    RoomMember, RoomMemberList, ServerPermission, UserKey, WithSig,
 };
 use blah::uuid::Uuid;
 use ed25519_dalek::pkcs8::spki::der::pem::LineEnding;
@@ -220,7 +220,7 @@ async fn main_api(api_url: Url, command: ApiCommand) -> Result<()> {
                     user: UserKey(key.verifying_key().to_bytes()),
                 }]),
             };
-            let payload = WithSig::sign(&key, &mut OsRng, payload)?;
+            let payload = WithSig::sign(&key, get_timestamp(), &mut OsRng, payload)?;
 
             let ret = client
                 .post(api_url.join("/room/create")?)
@@ -242,7 +242,7 @@ async fn main_api(api_url: Url, command: ApiCommand) -> Result<()> {
                 room,
                 rich_text: RichText::from(text),
             };
-            let payload = WithSig::sign(&key, &mut OsRng, payload)?;
+            let payload = WithSig::sign(&key, get_timestamp(), &mut OsRng, payload)?;
 
             let ret = client
                 .post(api_url.join(&format!("/room/{room}/item"))?)

pages/main.js

@@ -96,7 +96,12 @@ async function showChatMsg(chat) {
     let verifyRet = null;
     crypto.subtle.exportKey('raw', keypair.publicKey)
     try {
-        const signeeBytes = (new TextEncoder()).encode(JSON.stringify(chat.signee));
+        const sortKeys = (obj) =>
+            Object.fromEntries(Object.entries(obj).sort((lhs, rhs) => lhs[0] > rhs[0]));
+        const canonicalJson = chat.signee
+        // Just for simplicity. Only this struct is unsorted due to serde implementation.
+        canonicalJson.payload = sortKeys(canonicalJson.payload)
+        const signeeBytes = (new TextEncoder()).encode(JSON.stringify(canonicalJson));
         const rawkey = hexToBuf(chat.signee.user);
         const senderKey = await crypto.subtle.importKey('raw', rawkey, { name: 'Ed25519' }, true, ['verify']);
         const success = await crypto.subtle.verify('Ed25519', senderKey, hexToBuf(chat.sig), signeeBytes);
@@ -244,9 +249,10 @@ async function postChat(text) {
             richText = [text];
         }
         const signedPayload = await signData({
-            typ: 'chat',
+            // sorted fields.
             rich_text: richText,
             room: roomUuid,
+            typ: 'chat',
         });
         const resp = await fetch(`${roomUrl}/item`, {
             method: 'POST',

src/types.rs

@@ -1,7 +1,3 @@
-//! NB. All structs here that are part of signee must be lexically sorted, as RFC8785.
-//! This is tested by `canonical_fields_sorted`.
-//! See: https://www.rfc-editor.org/rfc/rfc8785
-//! FIXME: `typ` is still always the first field because of `serde`'s implementation.
 use std::fmt;
 use std::time::SystemTime;
 
@@ -44,7 +40,7 @@ pub struct Signee<T> {
     pub user: UserKey,
 }
 
-fn get_timestamp() -> u64 {
+pub fn get_timestamp() -> u64 {
     SystemTime::now()
         .duration_since(SystemTime::UNIX_EPOCH)
         .expect("after UNIX epoch")
@@ -55,16 +51,17 @@ impl<T: Serialize> WithSig<T> {
     /// Sign the payload with the given `key`.
     pub fn sign(
         key: &SigningKey,
+        timestamp: u64,
         rng: &mut impl RngCore,
         payload: T,
     ) -> Result<Self, SignatureError> {
         let signee = Signee {
             nonce: rng.next_u32(),
             payload,
-            timestamp: get_timestamp(),
+            timestamp,
             user: UserKey(key.verifying_key().to_bytes()),
         };
-        let canonical_signee = serde_json::to_vec(&signee).expect("serialization cannot fail");
+        let canonical_signee = serde_jcs::to_vec(&signee).expect("serialization cannot fail");
         let sig = key.try_sign(&canonical_signee)?.to_bytes();
         Ok(Self { sig, signee })
     }
@@ -73,7 +70,7 @@ impl<T: Serialize> WithSig<T> {
     ///
     /// Note that this does nott check validity of timestamp and other data.
     pub fn verify(&self) -> Result<(), SignatureError> {
-        let canonical_signee = serde_json::to_vec(&self.signee).expect("serialization cannot fail");
+        let canonical_signee = serde_jcs::to_vec(&self.signee).expect("serialization cannot fail");
         let sig = Signature::from_bytes(&self.sig);
         VerifyingKey::from_bytes(&self.signee.user.0)?.verify_strict(&canonical_signee, &sig)?;
         Ok(())
@@ -431,49 +428,32 @@ mod sql_impl {
 
 #[cfg(test)]
 mod tests {
-    use std::fmt::Write;
-
-    use syn::visit;
-
     use super::*;
 
-    #[derive(Default)]
-    struct Visitor {
-        errors: String,
-    }
-
-    const SKIP_CHECK_STRUCTS: &[&str] = &["RichTextPiece", "RichTextPieceRaw"];
-
-    impl<'ast> syn::visit::Visit<'ast> for Visitor {
-        fn visit_fields_named(&mut self, i: &'ast syn::FieldsNamed) {
-            let fields = i
-                .named
-                .iter()
-                .flat_map(|f| f.ident.clone())
-                .map(|i| i.to_string())
-                .collect::<Vec<_>>();
-            if !fields.windows(2).all(|w| w[0] < w[1]) {
-                writeln!(self.errors, "unsorted fields: {fields:?}").unwrap();
-            }
-        }
-
-        fn visit_item_struct(&mut self, i: &'ast syn::ItemStruct) {
-            if !SKIP_CHECK_STRUCTS.contains(&&*i.ident.to_string()) {
-                visit::visit_item_struct(self, i);
-            }
-        }
-    }
-
     #[test]
-    fn canonical_fields_sorted() {
+    fn canonical_chat() {
-        let src = std::fs::read_to_string(file!()).unwrap();
+        let mut fake_rng = rand::rngs::mock::StepRng::new(0x42, 1);
-        let file = syn::parse_file(&src).unwrap();
+        let signing_key = SigningKey::from_bytes(&[0x42; 32]);
+        let timestamp = 0xDEAD_BEEF;
+        let item = WithSig::sign(
+            &signing_key,
+            timestamp,
+            &mut fake_rng,
+            ChatPayload {
+                rich_text: RichText::from("hello"),
+                room: Uuid::nil(),
+            },
+        )
+        .unwrap();
 
-        let mut v = Visitor::default();
+        let json = serde_jcs::to_string(&item).unwrap();
-        syn::visit::visit_file(&mut v, &file);
+        assert_eq!(
-        if !v.errors.is_empty() {
+            json,
-            panic!("{}", v.errors);
+            r#"{"sig":"5e52985dc9e43a77267f0b383a8223af96f36e83c180a36da627dfac6504b2bb4c6b80c9903a6c3a0bbc742718466d72af4407a8e74d41af5cb0137cf3798d08","signee":{"nonce":66,"payload":{"rich_text":["hello"],"room":"00000000-0000-0000-0000-000000000000","typ":"chat"},"timestamp":3735928559,"user":"2152f8d19b791d24453242e15f2eab6cb7cffa7b6a5ed30097960e069881db12"}}"#
-        }
+        );
+        let roundtrip_item = serde_json::from_str::<WithSig<ChatPayload>>(&json).unwrap();
+        // assert_eq!(roundtrip_item, item);
+        roundtrip_item.verify().unwrap();
     }
 
     #[test]