Merge pull request #80 from aave/mike/improve/wad-ray-math

Mike/improve/wad ray math

Author: mpsc0x

aave-core/aave-math/sources/wad_ray_math.move

@@ -115,6 +115,7 @@ module aave_math::wad_ray_math {
     /// @return c Result of a*b, in ray, rounded down
     public fun ray_mul_down(a: u256, b: u256): u256 {
         if (a == 0 || b == 0) return 0;
+        assert!(a <= U256_MAX / b, error_config::get_eoverflow());
         (a * b) / RAY
     }
 
@@ -155,6 +156,10 @@ module aave_math::wad_ray_math {
     public fun ray_div_down(a: u256, b: u256): u256 {
         assert!(b > 0, error_config::get_edivision_by_zero());
         if (a == 0) return 0;
+        assert!(
+            a <= U256_MAX / RAY,
+            error_config::get_eoverflow()
+        );
         (a * RAY) / b
     }
 

aave-core/aave-math/tests/wad_ray_math_tests.move

@@ -445,4 +445,22 @@ module aave_math::wad_ray_math_tests {
         assert!(interest_up == 1050000000000000000000000000, TEST_SUCCESS);
         assert!(interest_down == 1050000000000000000000000000, TEST_SUCCESS);
     }
+
+    #[test]
+    #[expected_failure(abort_code = EOVERFLOW, location = aave_math::wad_ray_math)]
+    fun test_ray_div_down_overflow() {
+        // a * RAY overflows at a = floor(U256_MAX / RAY) + 1
+        let a = get_u256_max_for_testing() / get_ray_for_testing() + 1;
+        let b = 1;
+        ray_div_down(a, b);
+    }
+
+    #[test]
+    #[expected_failure(abort_code = EOVERFLOW, location = aave_math::wad_ray_math)]
+    fun test_ray_mul_down_overflow() {
+        // a * b overflows at a = floor(U256_MAX / b) + 1 (choose b > 0)
+        let b = 1000000000000000000000000000; // 1 RAY
+        let a = get_u256_max_for_testing() / b + 1;
+        ray_mul_down(a, b);
+    }
 }