Introduce monero-wallet crate

This is fairly bare-bones for now and only contains one piece of
functionality: choosing random key offsets.

More functionality for actually signing Monero transactions will
be added later.

Cargo.lock

@@ -2214,6 +2214,21 @@ dependencies = [
  "tracing",
 ]
 
+[[package]]
+name = "monero-wallet"
+version = "0.1.0"
+dependencies = [
+ "anyhow",
+ "curve25519-dalek",
+ "monero",
+ "monero-harness",
+ "monero-rpc",
+ "rand 0.7.3",
+ "testcontainers 0.12.0",
+ "tokio",
+ "tracing-subscriber",
+]
+
 [[package]]
 name = "multihash"
 version = "0.13.2"

Cargo.toml

@@ -1,5 +1,5 @@
 [workspace]
-members = [ "monero-harness", "monero-rpc", "swap" ]
+members = [ "monero-harness", "monero-rpc", "swap", "monero-wallet" ]
 
 [patch.crates-io]
 torut = { git = "https://github.com/bonomat/torut/", branch = "feature-flag-tor-secret-keys", default-features = false, features = [ "v3", "control" ] }

monero-wallet/Cargo.toml

@@ -0,0 +1,19 @@
+[package]
+name = "monero-wallet"
+version = "0.1.0"
+authors = [ "CoBloX Team <team@coblox.tech>" ]
+edition = "2018"
+
+[dependencies]
+anyhow = "1"
+monero = "0.12"
+monero-rpc = { path = "../monero-rpc" }
+rand = "0.7"
+
+[dev-dependencies]
+curve25519-dalek = "3"
+monero-harness = { path = "../monero-harness" }
+rand = "0.7"
+testcontainers = "0.12"
+tokio = { version = "1", features = [ "rt-multi-thread", "time", "macros", "sync", "process", "fs" ] }
+tracing-subscriber = { version = "0.2", default-features = false, features = [ "fmt", "ansi", "env-filter", "chrono", "tracing-log" ] }

monero-wallet/src/lib.rs

@@ -0,0 +1,93 @@
+use anyhow::{Context, Result};
+use monero::consensus::encode::VarInt;
+use monero::cryptonote::hash::Hashable;
+use monero_rpc::monerod;
+use monero_rpc::monerod::{GetBlockResponse, MonerodRpc as _};
+use rand::Rng;
+
+pub struct Wallet {
+    client: monerod::Client,
+}
+
+impl Wallet {
+    /// Chooses 10 random key offsets for use within a new confidential
+    /// transactions.
+    ///
+    /// Choosing these offsets randomly is not ideal for privacy, instead they
+    /// should be chosen in a way that mimics a real spending pattern as much as
+    /// possible.
+    pub async fn choose_ten_random_key_offsets(&self) -> Result<[VarInt; 10]> {
+        let latest_block = self.client.get_block_count().await?;
+        let latest_spendable_block = latest_block.count - 10;
+
+        let block: GetBlockResponse = self.client.get_block(latest_spendable_block).await?;
+
+        let tx_hash = block
+            .blob
+            .tx_hashes
+            .first()
+            .copied()
+            .unwrap_or_else(|| block.blob.miner_tx.hash());
+
+        let indices = self.client.get_o_indexes(tx_hash).await?;
+
+        let last_index = indices
+            .o_indexes
+            .into_iter()
+            .max()
+            .context("Expected at least one output index")?;
+        let oldest_index = last_index - (last_index / 100) * 40; // oldest index must be within last 40% TODO: CONFIRM THIS
+
+        let mut rng = rand::thread_rng();
+
+        Ok([
+            VarInt(rng.gen_range(oldest_index, last_index)),
+            VarInt(rng.gen_range(oldest_index, last_index)),
+            VarInt(rng.gen_range(oldest_index, last_index)),
+            VarInt(rng.gen_range(oldest_index, last_index)),
+            VarInt(rng.gen_range(oldest_index, last_index)),
+            VarInt(rng.gen_range(oldest_index, last_index)),
+            VarInt(rng.gen_range(oldest_index, last_index)),
+            VarInt(rng.gen_range(oldest_index, last_index)),
+            VarInt(rng.gen_range(oldest_index, last_index)),
+            VarInt(rng.gen_range(oldest_index, last_index)),
+        ])
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use monero_harness::image::Monerod;
+    use monero_rpc::monerod::{Client, GetOutputsOut};
+    use testcontainers::clients::Cli;
+    use testcontainers::Docker;
+
+    #[tokio::test]
+    async fn get_outs_for_key_offsets() {
+        let cli = Cli::default();
+        let container = cli.run(Monerod::default());
+        let rpc_client = Client::localhost(container.get_host_port(18081).unwrap()).unwrap();
+        rpc_client.generateblocks(150, "498AVruCDWgP9Az9LjMm89VWjrBrSZ2W2K3HFBiyzzrRjUJWUcCVxvY1iitfuKoek2FdX6MKGAD9Qb1G1P8QgR5jPmmt3Vj".to_owned()).await.unwrap();
+        let wallet = Wallet {
+            client: rpc_client.clone(),
+        };
+
+        let key_offsets = wallet.choose_ten_random_key_offsets().await.unwrap();
+        let result = rpc_client
+            .get_outs(
+                key_offsets
+                    .to_vec()
+                    .into_iter()
+                    .map(|varint| GetOutputsOut {
+                        amount: 0,
+                        index: varint.0,
+                    })
+                    .collect(),
+            )
+            .await
+            .unwrap();
+
+        assert_eq!(result.outs.len(), 10);
+    }
+}