Merge GH #779 Add ECDH/ECIES blinding and DH small subgroup checking

1 files changed, 13 insertions, 7 deletions

diff --git a/src/lib/pubkey/ecdh/ecdh.cpp b/src/lib/pubkey/ecdh/ecdh.cpp
index 32914be2e..0ddb39275 100644
--- a/src/lib/pubkey/ecdh/ecdh.cpp
+++ b/src/lib/pubkey/ecdh/ecdh.cpp
@@ -27,32 +27,38 @@ class ECDH_KA_Operation : public PK_Ops::Key_Agreement_with_KDF
    {
    public:
 
-      ECDH_KA_Operation(const ECDH_PrivateKey& key, const std::string& kdf) :
+      ECDH_KA_Operation(const ECDH_PrivateKey& key, const std::string& kdf, RandomNumberGenerator& rng) :
          PK_Ops::Key_Agreement_with_KDF(kdf),
          m_curve(key.domain().get_curve()),
-         m_cofactor(key.domain().get_cofactor())
+         m_cofactor(key.domain().get_cofactor()),
+         m_order(key.domain().get_order()),
+         m_rng(rng)
          {
-         m_l_times_priv = inverse_mod(m_cofactor, key.domain().get_order()) * key.private_value();
+         m_l_times_priv = inverse_mod(m_cofactor, m_order) * key.private_value();
          }
 
       secure_vector<uint8_t> raw_agree(const uint8_t w[], size_t w_len) override
          {
          PointGFp point = OS2ECP(w, w_len, m_curve);
-         // TODO: add blinding
-         PointGFp S = (m_cofactor * point) * m_l_times_priv;
+         PointGFp S = m_cofactor * point;
+         Blinded_Point_Multiply blinder(S, m_order);
+         S = blinder.blinded_multiply(m_l_times_priv, m_rng);
          BOTAN_ASSERT(S.on_the_curve(), "ECDH agreed value was on the curve");
          return BigInt::encode_1363(S.get_affine_x(), m_curve.get_p().bytes());
          }
    private:
       const CurveGFp& m_curve;
       const BigInt& m_cofactor;
+      const BigInt& m_order;
       BigInt m_l_times_priv;
+      RandomNumberGenerator& m_rng;
+
    };
 
 }
 
 std::unique_ptr<PK_Ops::Key_Agreement>
-ECDH_PrivateKey::create_key_agreement_op(RandomNumberGenerator& /*rng*/,
+ECDH_PrivateKey::create_key_agreement_op(RandomNumberGenerator& rng,
                                          const std::string& params,
                                          const std::string& provider) const
    {
@@ -72,7 +78,7 @@ ECDH_PrivateKey::create_key_agreement_op(RandomNumberGenerator& /*rng*/,
 #endif
 
    if(provider == "base" || provider.empty())
-      return std::unique_ptr<PK_Ops::Key_Agreement>(new ECDH_KA_Operation(*this, params));
+      return std::unique_ptr<PK_Ops::Key_Agreement>(new ECDH_KA_Operation(*this, params, rng));
 
    throw Provider_Not_Found(algo_name(), provider);
    }