feat(tests): add critical BLS tests with invalid point coordinates (#2000)

This adds test cases for BLS precompiles where one of the point (G1/G2)
coordinates is "slightly" above the value of the field prime P.
The "slightly above" means that a valid point is modified by adding P
to one of its field elements. Such test case has a chance of detecting
an invalid implementation where the field element is loaded as 384-bit
integer and converted to the Montgomery form. The Montgomery form
round-trip has the effect of computing a value mod P,
i.e. `(x + P) % P` gives `x` and the invalid point becomes valid.

In the similar way test cases may be extended to other BLS precompiles.
However, I assume BLS precompiles implementations share the input
validation code.

Author: chfast

tests/prague/eip2537_bls_12_381_precompiles/test_bls12_g1add.py

@@ -273,6 +273,22 @@ def test_valid(
             Spec.INF_G1 + PointG1(0, Spec.P),
             id="b_y_equal_to_p",
         ),
+        pytest.param(
+            PointG1(Spec.P1.x + Spec.P, Spec.P1.y) + Spec.G1,
+            id="a_x_above_p",
+        ),
+        pytest.param(
+            PointG1(Spec.P1.x, Spec.P1.y + Spec.P) + Spec.G1,
+            id="a_y_above_p",
+        ),
+        pytest.param(
+            Spec.P1 + PointG1(Spec.G1.x + Spec.P, Spec.G1.y),
+            id="b_x_above_p",
+        ),
+        pytest.param(
+            Spec.P1 + PointG1(Spec.G1.x, Spec.G1.y + Spec.P),
+            id="b_y_above_p",
+        ),
         pytest.param(
             b"\x80" + bytes(Spec.INF_G1)[1:] + Spec.INF_G1,
             id="invalid_encoding_a",

tests/prague/eip2537_bls_12_381_precompiles/test_bls12_g2add.py

@@ -289,6 +289,38 @@ def test_valid(
             Spec.INF_G2 + PointG2((0, 0), (0, Spec.P)),
             id="b_y_2_equal_to_p",
         ),
+        pytest.param(
+            PointG2((Spec.P2.x[0] + Spec.P, Spec.P2.x[1]), Spec.P2.y) + Spec.G2,
+            id="a_x_1_above_p",
+        ),
+        pytest.param(
+            PointG2((Spec.P2.x[0], Spec.P2.x[1] + Spec.P), Spec.P2.y) + Spec.G2,
+            id="a_x_2_above_p",
+        ),
+        pytest.param(
+            PointG2(Spec.P2.x, (Spec.P2.y[0] + Spec.P, Spec.P2.y[1])) + Spec.G2,
+            id="a_y_1_above_p",
+        ),
+        pytest.param(
+            PointG2(Spec.P2.x, (Spec.P2.y[0], Spec.P2.y[1] + Spec.P)) + Spec.G2,
+            id="a_y_2_above_p",
+        ),
+        pytest.param(
+            Spec.P2 + PointG2((Spec.G2.x[0] + Spec.P, Spec.G2.x[1]), Spec.G2.y),
+            id="b_x_1_above_p",
+        ),
+        pytest.param(
+            Spec.P2 + PointG2((Spec.G2.x[0], Spec.G2.x[1] + Spec.P), Spec.G2.y),
+            id="b_x_2_above_p",
+        ),
+        pytest.param(
+            Spec.P2 + PointG2(Spec.G2.x, (Spec.G2.y[0] + Spec.P, Spec.G2.y[1])),
+            id="b_y_1_above_p",
+        ),
+        pytest.param(
+            Spec.P2 + PointG2(Spec.G2.x, (Spec.G2.y[0], Spec.G2.y[1] + Spec.P)),
+            id="b_y_2_above_p",
+        ),
         pytest.param(
             b"\x80" + bytes(Spec.INF_G2)[1:] + Spec.INF_G2,
             id="invalid_encoding_a",