Ensure that trying to add points from different groups fails.

Producing garbage instead is asking for trouble.

3 files changed, 35 insertions, 13 deletions

diff --git a/src/lib/pubkey/ec_group/curve_gfp.h b/src/lib/pubkey/ec_group/curve_gfp.h
index 865bb68f8..888f87d46 100644
--- a/src/lib/pubkey/ec_group/curve_gfp.h
+++ b/src/lib/pubkey/ec_group/curve_gfp.h
@@ -201,6 +201,22 @@ class BOTAN_UNSTABLE_API CurveGFp final
          std::swap(m_repr, other.m_repr);
          }
 
+      /**
+      * Equality operator
+      * @param lhs a curve
+      * @param rhs a curve
+      * @return true iff lhs is the same as rhs
+      */
+      inline bool operator==(const CurveGFp& other) const
+         {
+         if(m_repr.get() == other.m_repr.get())
+            return true;
+
+         return (get_p() == other.get_p()) &&
+                (get_a() == other.get_a()) &&
+                (get_b() == other.get_b());
+         }
+
    private:
       static std::shared_ptr<CurveGFp_Repr>
          choose_repr(const BigInt& p, const BigInt& a, const BigInt& b);
@@ -208,19 +224,6 @@ class BOTAN_UNSTABLE_API CurveGFp final
       std::shared_ptr<CurveGFp_Repr> m_repr;
    };
 
-/**
-* Equality operator
-* @param lhs a curve
-* @param rhs a curve
-* @return true iff lhs is the same as rhs
-*/
-inline bool operator==(const CurveGFp& lhs, const CurveGFp& rhs)
-   {
-   return (lhs.get_p() == rhs.get_p()) &&
-          (lhs.get_a() == rhs.get_a()) &&
-          (lhs.get_b() == rhs.get_b());
-   }
-
 inline bool operator!=(const CurveGFp& lhs, const CurveGFp& rhs)
    {
    return !(lhs == rhs);
diff --git a/src/lib/pubkey/ec_group/point_gfp.cpp b/src/lib/pubkey/ec_group/point_gfp.cpp
index 8f53bb079..b1c921a51 100644
--- a/src/lib/pubkey/ec_group/point_gfp.cpp
+++ b/src/lib/pubkey/ec_group/point_gfp.cpp
@@ -87,6 +87,7 @@ inline bool all_zeros(const word x[], size_t len)
 
 void PointGFp::add_affine(const PointGFp& rhs, std::vector<BigInt>& workspace)
    {
+   BOTAN_ASSERT_NOMSG(m_curve == rhs.m_curve);
    BOTAN_DEBUG_ASSERT(rhs.is_affine());
 
    const size_t p_words = m_curve.get_p_words();
@@ -180,6 +181,8 @@ void PointGFp::add_affine(const word x_words[], size_t x_size,
 // Point addition
 void PointGFp::add(const PointGFp& rhs, std::vector<BigInt>& ws_bn)
    {
+   BOTAN_ASSERT_NOMSG(m_curve == rhs.m_curve);
+
    if(rhs.is_zero())
       return;
 
diff --git a/src/tests/unit_ecc.cpp b/src/tests/unit_ecc.cpp
index c79307c10..32d521d41 100644
--- a/src/tests/unit_ecc.cpp
+++ b/src/tests/unit_ecc.cpp
@@ -520,6 +520,21 @@ Test::Result test_mult_point()
    return result;
    }
 
+Test::Result test_mixed_points()
+   {
+   Test::Result result("ECC Unit");
+
+   Botan::EC_Group secp256r1("secp256r1");
+   Botan::EC_Group secp384r1("secp384r1");
+
+   const Botan::PointGFp& G256 = secp256r1.get_base_point();
+   const Botan::PointGFp& G384 = secp384r1.get_base_point();
+
+   result.test_throws("Mixing points from different groups",
+                      [&] { Botan::PointGFp p = G256 + G384; });
+   return result;
+   }
+
 Test::Result test_basic_operations()
    {
    Test::Result result("ECC Unit");
@@ -678,6 +693,7 @@ class ECC_Unit_Tests final : public Test
          results.push_back(test_point_mult());
          results.push_back(test_point_negative());
          results.push_back(test_mult_point());
+         results.push_back(test_mixed_points());
          results.push_back(test_basic_operations());
          results.push_back(test_enc_dec_compressed_160());
          results.push_back(test_enc_dec_compressed_256());