From c5492a3632f50271c2bb44e36a82380359441375 Mon Sep 17 00:00:00 2001
From: Jack Lloyd <jack@randombit.net>
Date: Sun, 6 Oct 2019 12:21:42 -0400
Subject: Throw if you attempt to use GOST 34.10-2012 with invalid params

It can only be used with 256 or 512 bit params, so enforce that.
---
 src/lib/pubkey/gost_3410/gost_3410.cpp | 25 +++++++++++++++++++++++--
 src/lib/pubkey/gost_3410/gost_3410.h   |  7 +++----
 2 files changed, 26 insertions(+), 6 deletions(-)

diff --git a/src/lib/pubkey/gost_3410/gost_3410.cpp b/src/lib/pubkey/gost_3410/gost_3410.cpp
index 7e4dbe221..61f674370 100644
--- a/src/lib/pubkey/gost_3410/gost_3410.cpp
+++ b/src/lib/pubkey/gost_3410/gost_3410.cpp
@@ -1,5 +1,5 @@
 /*
-* GOST 34.10-2001 implemenation
+* GOST 34.10-2012
 * (C) 2007 Falko Strenzke, FlexSecure GmbH
 *          Manuel Hartl, FlexSecure GmbH
 * (C) 2008-2010,2015,2018 Jack Lloyd
@@ -42,7 +42,12 @@ std::vector<uint8_t> GOST_3410_PublicKey::public_key_bits() const
 
 std::string GOST_3410_PublicKey::algo_name() const
    {
-   return "GOST-34.10-2012-" + std::to_string(domain().get_p_bits());
+   const size_t p_bits = domain().get_p_bits();
+
+   if(p_bits == 256 || p_bits == 512)
+      return "GOST-34.10-2012-" + std::to_string(p_bits);
+   else
+      throw Encoding_Error("GOST-34.10-2012 is not defined for parameters of this size");
    }
 
 AlgorithmIdentifier GOST_3410_PublicKey::algorithm_identifier() const
@@ -67,6 +72,11 @@ GOST_3410_PublicKey::GOST_3410_PublicKey(const AlgorithmIdentifier& alg_id,
 
    m_domain_params = EC_Group(ecc_param_id);
 
+   const size_t p_bits = m_domain_params.get_p_bits();
+   if(p_bits != 256 && p_bits != 512)
+      throw Decoding_Error("GOST-34.10-2012 is not defined for parameters of size " +
+                           std::to_string(p_bits));
+
    secure_vector<uint8_t> bits;
    BER_Decoder(key_bits).decode(bits, OCTET_STRING);
 
@@ -88,6 +98,17 @@ GOST_3410_PublicKey::GOST_3410_PublicKey(const AlgorithmIdentifier& alg_id,
                 "Loaded GOST 34.10 public key is on the curve");
    }
 
+GOST_3410_PrivateKey::GOST_3410_PrivateKey(RandomNumberGenerator& rng,
+                                           const EC_Group& domain,
+                                           const BigInt& x) :
+   EC_PrivateKey(rng, domain, x)
+   {
+   const size_t p_bits = m_domain_params.get_p_bits();
+   if(p_bits != 256 && p_bits != 512)
+      throw Decoding_Error("GOST-34.10-2012 is not defined for parameters of size " +
+                           std::to_string(p_bits));
+   }
+
 namespace {
 
 BigInt decode_le(const uint8_t msg[], size_t msg_len)
diff --git a/src/lib/pubkey/gost_3410/gost_3410.h b/src/lib/pubkey/gost_3410/gost_3410.h
index 28e8274de..9eedaf122 100644
--- a/src/lib/pubkey/gost_3410/gost_3410.h
+++ b/src/lib/pubkey/gost_3410/gost_3410.h
@@ -67,8 +67,8 @@ class BOTAN_PUBLIC_API(2,0) GOST_3410_PublicKey : public virtual EC_PublicKey
 /**
 * GOST-34.10 Private Key
 */
-class BOTAN_PUBLIC_API(2,0) GOST_3410_PrivateKey final : public GOST_3410_PublicKey,
-                                       public EC_PrivateKey
+class BOTAN_PUBLIC_API(2,0) GOST_3410_PrivateKey final :
+   public GOST_3410_PublicKey, public EC_PrivateKey
    {
    public:
       /**
@@ -88,8 +88,7 @@ class BOTAN_PUBLIC_API(2,0) GOST_3410_PrivateKey final : public GOST_3410_Public
       */
       GOST_3410_PrivateKey(RandomNumberGenerator& rng,
                            const EC_Group& domain,
-                           const BigInt& x = 0) :
-         EC_PrivateKey(rng, domain, x) {}
+                           const BigInt& x = 0);
 
       AlgorithmIdentifier pkcs8_algorithm_identifier() const override
          { return EC_PublicKey::algorithm_identifier(); }
-- 
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