From a06ae48e2f2c7a1f4d910176534e36e91a67c8d1 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Jon=20H=C3=A4ggblad?= <jon.haggblad@gmail.com>
Date: Mon, 20 May 2024 10:22:28 +0200
Subject: [PATCH] Add methods to MixnetClient to sign messages (#4602)

---
 .../client-core/src/client/base_client/mod.rs  |  5 ++++-
 sdk/rust/nym-sdk/src/mixnet/client.rs          |  2 ++
 sdk/rust/nym-sdk/src/mixnet/native_client.rs   | 18 ++++++++++++++++++
 3 files changed, 24 insertions(+), 1 deletion(-)

diff --git a/common/client-core/src/client/base_client/mod.rs b/common/client-core/src/client/base_client/mod.rs
index 42adcf2da4..ec8026d076 100644
--- a/common/client-core/src/client/base_client/mod.rs
+++ b/common/client-core/src/client/base_client/mod.rs
@@ -39,7 +39,7 @@ use log::{debug, error, info, warn};
 use nym_bandwidth_controller::BandwidthController;
 use nym_client_core_gateways_storage::{GatewayDetails, GatewaysDetailsStore};
 use nym_credential_storage::storage::Storage as CredentialStorage;
-use nym_crypto::asymmetric::encryption;
+use nym_crypto::asymmetric::{encryption, identity};
 use nym_gateway_client::{
     AcknowledgementReceiver, GatewayClient, GatewayConfig, MixnetMessageReceiver, PacketRouter,
 };
@@ -670,6 +670,7 @@ where
         let self_address = Self::mix_address(&init_res);
         let ack_key = init_res.client_keys.ack_key();
         let encryption_keys = init_res.client_keys.encryption_keypair();
+        let identity_keys = init_res.client_keys.identity_keypair();
 
         // the components are started in very specific order. Unless you know what you are doing,
         // do not change that.
@@ -792,6 +793,7 @@ where
 
         Ok(BaseClient {
             address: self_address,
+            identity_keys,
             client_input: ClientInputStatus::AwaitingProducer {
                 client_input: ClientInput {
                     connection_command_sender: client_connection_tx,
@@ -816,6 +818,7 @@ where
 
 pub struct BaseClient {
     pub address: Recipient,
+    pub identity_keys: Arc<identity::KeyPair>,
     pub client_input: ClientInputStatus,
     pub client_output: ClientOutputStatus,
     pub client_state: ClientState,
diff --git a/sdk/rust/nym-sdk/src/mixnet/client.rs b/sdk/rust/nym-sdk/src/mixnet/client.rs
index cfcc6b3f45..f6239d62ff 100644
--- a/sdk/rust/nym-sdk/src/mixnet/client.rs
+++ b/sdk/rust/nym-sdk/src/mixnet/client.rs
@@ -742,10 +742,12 @@ where
         let mut client_output = started_client.client_output.register_consumer();
         let client_state = started_client.client_state;
 
+        let identity_keys = started_client.identity_keys.clone();
         let reconstructed_receiver = client_output.register_receiver()?;
 
         Ok(MixnetClient::new(
             nym_address,
+            identity_keys,
             client_input,
             client_output,
             client_state,
diff --git a/sdk/rust/nym-sdk/src/mixnet/native_client.rs b/sdk/rust/nym-sdk/src/mixnet/native_client.rs
index c4e4c13739..ad514d6513 100644
--- a/sdk/rust/nym-sdk/src/mixnet/native_client.rs
+++ b/sdk/rust/nym-sdk/src/mixnet/native_client.rs
@@ -10,6 +10,7 @@ use nym_client_core::client::{
     inbound_messages::InputMessage,
     received_buffer::ReconstructedMessagesReceiver,
 };
+use nym_crypto::asymmetric::identity;
 use nym_sphinx::addressing::clients::Recipient;
 use nym_sphinx::{params::PacketType, receiver::ReconstructedMessage};
 use nym_task::{
@@ -18,6 +19,7 @@ use nym_task::{
 };
 use nym_topology::NymTopology;
 use std::pin::Pin;
+use std::sync::Arc;
 use std::task::{Context, Poll};
 
 /// Client connected to the Nym mixnet.
@@ -25,6 +27,8 @@ pub struct MixnetClient {
     /// The nym address of this connected client.
     pub(crate) nym_address: Recipient,
 
+    pub(crate) identity_keys: Arc<identity::KeyPair>,
+
     /// Input to the client from the users perspective. This can be either data to send or control
     /// messages.
     pub(crate) client_input: ClientInput,
@@ -50,8 +54,10 @@ pub struct MixnetClient {
 }
 
 impl MixnetClient {
+    #[allow(clippy::too_many_arguments)]
     pub(crate) fn new(
         nym_address: Recipient,
+        identity_keys: Arc<identity::KeyPair>,
         client_input: ClientInput,
         client_output: ClientOutput,
         client_state: ClientState,
@@ -61,6 +67,7 @@ impl MixnetClient {
     ) -> Self {
         Self {
             nym_address,
+            identity_keys,
             client_input,
             client_output,
             client_state,
@@ -98,6 +105,17 @@ impl MixnetClient {
         &self.nym_address
     }
 
+    /// Sign a message with the client's private identity key.
+    pub fn sign(&self, data: &[u8]) -> identity::Signature {
+        self.identity_keys.private_key().sign(data)
+    }
+
+    /// Sign a message with the client's private identity key and return it as a base58 encoded
+    /// signature.
+    pub fn sign_text(&self, text: &str) -> String {
+        self.identity_keys.private_key().sign_text(text)
+    }
+
     /// Get gateway connection information, like the file descriptor of the WebSocket
     pub fn gateway_connection(&self) -> GatewayConnection {
         self.client_state.gateway_connection