[Crypto] Add ctx initialisation for bip38

Warrows · Warrows · commit f10439c8784d · 2018-06-11T15:36:44.000+02:00
diff --git a/src/bip38.cpp b/src/bip38.cpp
@@ -8,6 +8,7 @@
 #include "pubkey.h"
 #include "util.h"
 #include "utilstrencodings.h"
+#include "random.h"
 
 #include <openssl/aes.h>
 #include <openssl/sha.h>
@@ -49,14 +50,25 @@ void ComputePassfactor(std::string ownersalt, uint256 prefactor, uint256& passfa
 bool ComputePasspoint(uint256 passfactor, CPubKey& passpoint)
 {
     size_t clen = 65;
-    secp256k1_context *ctx = NULL;
+    secp256k1_context *ctx = secp256k1_context_create(SECP256K1_CONTEXT_SIGN);
+    assert(ctx != nullptr);
+    {
+        // Pass in a random blinding seed to the secp256k1 context.
+        std::vector<unsigned char, secure_allocator<unsigned char>> vseed(32);
+        GetRandBytes(vseed.data(), 32);
+        bool ret = secp256k1_context_randomize(ctx, vseed.data());
+        assert(ret);
+    }
     secp256k1_pubkey pubkey;
 
     //passpoint is the ec_mult of passfactor on secp256k1
-    if (!secp256k1_ec_pubkey_create(ctx, &pubkey, passfactor.begin()))
+    if (!secp256k1_ec_pubkey_create(ctx, &pubkey, passfactor.begin())) {
+        secp256k1_context_destroy(ctx);
         return false;
+    }
 
     secp256k1_ec_pubkey_serialize(ctx, (unsigned char*)passpoint.begin(), &clen, &pubkey, SECP256K1_EC_COMPRESSED);
+    secp256k1_context_destroy(ctx);
 
     if (passpoint.size() != clen)
         return false;
@@ -241,10 +253,21 @@ bool BIP38_Decrypt(std::string strPassphrase, std::string strEncryptedKey, uint2
     ComputeFactorB(seedB, factorB);
 
     //multiply passfactor by factorb mod N to yield the priv key
-    secp256k1_context *ctx = NULL;
+    secp256k1_context *ctx = secp256k1_context_create(SECP256K1_CONTEXT_SIGN);
+    assert(ctx != nullptr);
+    {
+        // Pass in a random blinding seed to the secp256k1 context.
+        std::vector<unsigned char, secure_allocator<unsigned char>> vseed(32);
+        GetRandBytes(vseed.data(), 32);
+        bool ret = secp256k1_context_randomize(ctx, vseed.data());
+        assert(ret);
+    }
     privKey = factorB;
-    if (!secp256k1_ec_privkey_tweak_mul(ctx, privKey.begin(), passfactor.begin()))
+    if (!secp256k1_ec_privkey_tweak_mul(ctx, privKey.begin(), passfactor.begin())) {
+        secp256k1_context_destroy(ctx);
         return false;
+    }
+    secp256k1_context_destroy(ctx);
 
     //double check that the address hash matches our final privkey
     CKey k;
