From 735282facf31b9ac688fd0724c1a68ca3dcc4107 Mon Sep 17 00:00:00 2001
From: Never <neverhub@users.noreply.github.com>
Date: Mon, 19 Dec 2016 13:35:18 +0100
Subject: Blind the ECDH/ECIES agree operation.

---
 src/lib/pubkey/ecdh/ecdh.cpp   | 20 +++++++++++++-------
 src/lib/pubkey/ecies/ecies.cpp | 13 ++++++++-----
 2 files changed, 21 insertions(+), 12 deletions(-)

diff --git a/src/lib/pubkey/ecdh/ecdh.cpp b/src/lib/pubkey/ecdh/ecdh.cpp
index 1bdf2c209..ed2f404dc 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<byte> raw_agree(const byte 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);
    }
diff --git a/src/lib/pubkey/ecies/ecies.cpp b/src/lib/pubkey/ecies/ecies.cpp
index b40d21251..060f9995e 100644
--- a/src/lib/pubkey/ecies/ecies.cpp
+++ b/src/lib/pubkey/ecies/ecies.cpp
@@ -55,9 +55,10 @@ class ECIES_PrivateKey : public EC_PrivateKey, public PK_Key_Agreement_Key
 class ECIES_ECDH_KA_Operation : public PK_Ops::Key_Agreement_with_KDF
    {
    public:
-      ECIES_ECDH_KA_Operation(const ECIES_PrivateKey& private_key) :
+      ECIES_ECDH_KA_Operation(const ECIES_PrivateKey& private_key, RandomNumberGenerator& rng) :
          PK_Ops::Key_Agreement_with_KDF("Raw"),
-         m_key(private_key)
+         m_key(private_key),
+         m_rng(rng)
          {
          }
 
@@ -65,21 +66,23 @@ class ECIES_ECDH_KA_Operation : public PK_Ops::Key_Agreement_with_KDF
          {
          const CurveGFp& curve = m_key.domain().get_curve();
          PointGFp point = OS2ECP(w, w_len, curve);
-         PointGFp S = point * m_key.private_value();
+         Blinded_Point_Multiply blinder(point, m_key.domain().get_order());
+         PointGFp S = blinder.blinded_multiply(m_key.private_value(), m_rng);
          BOTAN_ASSERT(S.on_the_curve(), "ECDH agreed value was on the curve");
          return BigInt::encode_1363(S.get_affine_x(), curve.get_p().bytes());
          }
 
    private:
       ECIES_PrivateKey m_key;
+      RandomNumberGenerator& m_rng;
    };
 
 std::unique_ptr<PK_Ops::Key_Agreement>
-ECIES_PrivateKey::create_key_agreement_op(RandomNumberGenerator& /*rng*/,
+ECIES_PrivateKey::create_key_agreement_op(RandomNumberGenerator& rng,
                                           const std::string& /*params*/,
                                           const std::string& /*provider*/) const
    {
-   return std::unique_ptr<PK_Ops::Key_Agreement>(new ECIES_ECDH_KA_Operation(*this));
+   return std::unique_ptr<PK_Ops::Key_Agreement>(new ECIES_ECDH_KA_Operation(*this, rng));
    }
 
 /**
-- 
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