From a13b6505ce733e7bd68c1a5523d12b254db66f32 Mon Sep 17 00:00:00 2001
From: CJ Cobb <46455409+cjcobb23@users.noreply.github.com>
Date: Fri, 22 Sep 2023 12:55:25 -0400
Subject: [PATCH] feat(multisig-prover): bcs msg to sign (#117)

* feat(multisig-prover): bcs msg to sign
---
 contracts/multisig-prover/src/encoding/bcs.rs | 57 ++++++++++++++++++-
 contracts/multisig-prover/src/encoding/mod.rs |  2 +-
 2 files changed, 56 insertions(+), 3 deletions(-)

diff --git a/contracts/multisig-prover/src/encoding/bcs.rs b/contracts/multisig-prover/src/encoding/bcs.rs
index 7605da1d6..6e28354aa 100644
--- a/contracts/multisig-prover/src/encoding/bcs.rs
+++ b/contracts/multisig-prover/src/encoding/bcs.rs
@@ -3,9 +3,13 @@ use cosmwasm_std::{HexBinary, Uint256};
 use itertools::Itertools;
 use multisig::{key::Signature, msg::Signer};
 
-use crate::{error::ContractError, types::Operator};
+use crate::{
+    error::ContractError,
+    types::{CommandBatch, Operator},
+};
 
 use super::Data;
+use sha3::{Digest, Keccak256};
 
 // TODO: all of the public functions in this file should be moved to a trait,
 // that has an abi and bcs implementation (and possibly others)
@@ -111,6 +115,19 @@ pub fn encode(data: &Data) -> HexBinary {
     .into()
 }
 
+pub fn msg_digest(command_batch: &CommandBatch) -> HexBinary {
+    let msg = Keccak256::digest(encode(&command_batch.data).as_slice());
+
+    // Sui is just mimicking EVM here
+    let unsigned = [
+        "\x19Sui Signed Message:\n32".as_bytes(), // Keccek256 hash length = 32
+        msg.as_slice(),
+    ]
+    .concat();
+
+    Keccak256::digest(unsigned).as_slice().into()
+}
+
 fn u256_to_u128(val: Uint256) -> u128 {
     val.to_string().parse().expect("value is larger than u128")
 }
@@ -128,6 +145,7 @@ mod test {
     use std::vec;
 
     use bcs::from_bytes;
+    use connection_router::msg::Message;
     use cosmwasm_std::{Addr, HexBinary, Uint256};
     use multisig::{
         key::{PublicKey, Signature},
@@ -139,11 +157,12 @@ mod test {
             bcs::{
                 command_params, encode, encode_proof, make_command_id, u256_to_u128, u256_to_u64,
             },
-            Data,
+            CommandBatchBuilder, Data,
         },
         types::Command,
     };
 
+    use super::msg_digest;
     #[test]
     fn test_u256_to_u128() {
         let val = u128::MAX;
@@ -343,4 +362,38 @@ mod test {
 
         assert_eq!(payload_hash_decoded, payload_hash.to_vec());
     }
+
+    #[test]
+    fn test_msg_to_sign() {
+        let mut builder = CommandBatchBuilder::new(1u128.into(), crate::encoding::Encoder::Bcs);
+        let _ = builder
+            .add_message(Message {
+                id: "ethereum:foobar".into(),
+                destination_address: "0F".repeat(32),
+                destination_chain: "sui".into(),
+                source_chain: "ethereum".into(),
+                source_address: "0x00".into(),
+                payload_hash: HexBinary::from(vec![1; 32]),
+            })
+            .unwrap();
+        let batch = builder.build().unwrap();
+        let msg = msg_digest(&batch);
+        assert_eq!(msg.len(), 32);
+
+        let mut builder = CommandBatchBuilder::new(1u128.into(), crate::encoding::Encoder::Bcs);
+        let _ = builder
+            .add_message(Message {
+                id: "ethereum:foobar2".into(),
+                destination_address: "0A".repeat(32),
+                destination_chain: "sui".into(),
+                source_chain: "ethereum".into(),
+                source_address: "0x00".into(),
+                payload_hash: HexBinary::from(vec![2; 32]),
+            })
+            .unwrap();
+
+        let batch = builder.build().unwrap();
+        let msg2 = msg_digest(&batch);
+        assert_ne!(msg, msg2);
+    }
 }
diff --git a/contracts/multisig-prover/src/encoding/mod.rs b/contracts/multisig-prover/src/encoding/mod.rs
index c6a9c03f3..14e905ad4 100644
--- a/contracts/multisig-prover/src/encoding/mod.rs
+++ b/contracts/multisig-prover/src/encoding/mod.rs
@@ -113,7 +113,7 @@ impl CommandBatch {
     pub fn msg_digest(&self) -> HexBinary {
         match self.encoder {
             Encoder::Abi => abi::msg_digest(self),
-            Encoder::Bcs => todo!(),
+            Encoder::Bcs => bcs::msg_digest(self),
         }
     }