Fix bn256 precompile arguments (#205)

evm_loader/program/src/evm/precompile/bn256.rs

@@ -1,19 +1,42 @@
+use ethnum::U256;
 use solana_program::alt_bn128::prelude::*;
 
 /// Call inner `bn256Add`
 #[must_use]
 pub fn bn256_add(input: &[u8]) -> Vec<u8> {
-    alt_bn128_addition(input).unwrap_or_else(|_| vec![])
+    if input.len() >= ALT_BN128_ADDITION_INPUT_LEN {
+        alt_bn128_addition(&input[..ALT_BN128_ADDITION_INPUT_LEN])
+    } else {
+        let mut buffer = vec![0_u8; ALT_BN128_ADDITION_INPUT_LEN];
+        buffer[..input.len()].copy_from_slice(input);
+        alt_bn128_addition(&buffer)
+    }
+    .unwrap()
 }
 
 /// Call inner `bn256ScalarMul`
 #[must_use]
 pub fn bn256_scalar_mul(input: &[u8]) -> Vec<u8> {
-    alt_bn128_multiplication(input).unwrap_or_else(|_| vec![])
+    if input.len() >= ALT_BN128_MULTIPLICATION_INPUT_LEN {
+        alt_bn128_multiplication(&input[..ALT_BN128_MULTIPLICATION_INPUT_LEN])
+    } else {
+        let mut buffer = vec![0_u8; ALT_BN128_MULTIPLICATION_INPUT_LEN];
+        buffer[..input.len()].copy_from_slice(input);
+        alt_bn128_multiplication(&buffer)
+    }
+    .unwrap()
 }
 
 /// Call inner `bn256Pairing`
 #[must_use]
 pub fn bn256_pairing(input: &[u8]) -> Vec<u8> {
-    alt_bn128_pairing(input).unwrap_or_else(|_| vec![])
+    if input.is_empty() {
+        return U256::ONE.to_be_bytes().to_vec();
+    }
+
+    if (input.len() % ALT_BN128_PAIRING_ELEMENT_LEN) != 0 {
+        return U256::ZERO.to_be_bytes().to_vec();
+    }
+
+    alt_bn128_pairing(input).unwrap()
 }