Add ristretto multiply syscall (#12699)

programs/bpf/rust/ristretto/src/lib.rs

@@ -0,0 +1,31 @@
+//! @brief Example Rust-based BPF program that performs a ristretto multiply
+
+pub mod ristretto;
+
+extern crate solana_sdk;
+use crate::ristretto::ristretto_mul;
+use curve25519_dalek::{constants::RISTRETTO_BASEPOINT_POINT, scalar::Scalar};
+use solana_sdk::{
+    account_info::AccountInfo, entrypoint, entrypoint::ProgramResult, info, pubkey::Pubkey,
+};
+
+entrypoint!(process_instruction);
+fn process_instruction(
+    _program_id: &Pubkey,
+    _accounts: &[AccountInfo],
+    _instruction_data: &[u8],
+) -> ProgramResult {
+    info!("Ristretto multiply");
+
+    let point = RISTRETTO_BASEPOINT_POINT;
+    let scalar = Scalar::zero();
+    let result = ristretto_mul(&point, &scalar)?;
+    assert_ne!(point, result);
+
+    let point = RISTRETTO_BASEPOINT_POINT;
+    let scalar = Scalar::one();
+    let result = ristretto_mul(&point, &scalar)?;
+    assert_eq!(point, result);
+
+    Ok(())
+}

programs/bpf/rust/ristretto/src/ristretto.rs

@@ -0,0 +1,33 @@
+use curve25519_dalek::{ristretto::RistrettoPoint, scalar::Scalar};
+use solana_sdk::{entrypoint::SUCCESS, program_error::ProgramError};
+
+/// Multiply a ristretto point with a scalar
+///
+/// @param point - Ristretto point
+/// @param scalar - Scalar to mulitply against
+/// @return - result of the multiplication
+#[inline]
+pub fn ristretto_mul(
+    point: &RistrettoPoint,
+    scalar: &Scalar,
+) -> Result<RistrettoPoint, ProgramError> {
+    let mut result = RistrettoPoint::default();
+    let status = unsafe {
+        sol_ristretto_mul(
+            point as *const _ as *const u8,
+            scalar as *const _ as *const u8,
+            &mut result as *const _ as *mut u8,
+        )
+    };
+    match status {
+        SUCCESS => Ok(result),
+        _ => Err(status.into()),
+    }
+}
+extern "C" {
+    fn sol_ristretto_mul(
+        point_addr: *const u8,
+        scalar_addr: *const u8,
+        result_addr: *mut u8,
+    ) -> u64;
+}