crypter: add a BytesToKey clone to replace the use of openssl

BytesToKeySHA512AES should be functionally identical to EVP_BytesToKey, but
drops the dependency on openssl.

Author: theuni

src/wallet/crypter.cpp

@@ -5,15 +5,41 @@
 #include "crypter.h"
 
 #include "crypto/aes.h"
+#include "crypto/sha512.h"
 #include "script/script.h"
 #include "script/standard.h"
 #include "util.h"
 
 #include <string>
 #include <vector>
 #include <boost/foreach.hpp>
-#include <openssl/aes.h>
-#include <openssl/evp.h>
+
+int CCrypter::BytesToKeySHA512AES(const std::vector<unsigned char>& chSalt, const SecureString& strKeyData, int count, unsigned char *key,unsigned char *iv) const
+{
+    // This mimics the behavior of openssl's EVP_BytesToKey with an aes256cbc
+    // cipher and sha512 message digest. Because sha512's output size (64b) is
+    // greater than the aes256 block size (16b) + aes256 key size (32b),
+    // there's no need to process more than once (D_0).
+
+    if(!count || !key || !iv)
+        return 0;
+
+    unsigned char buf[CSHA512::OUTPUT_SIZE];
+    CSHA512 di;
+
+    di.Write((const unsigned char*)strKeyData.c_str(), strKeyData.size());
+    if(chSalt.size())
+        di.Write(&chSalt[0], chSalt.size());
+    di.Finalize(buf);
+
+    for(int i = 0; i != count - 1; i++)
+        di.Reset().Write(buf, sizeof(buf)).Finalize(buf);
+
+    memcpy(key, buf, WALLET_CRYPTO_KEY_SIZE);
+    memcpy(iv, buf + WALLET_CRYPTO_KEY_SIZE, WALLET_CRYPTO_IV_SIZE);
+    memory_cleanse(buf, sizeof(buf));
+    return WALLET_CRYPTO_KEY_SIZE;
+}
 
 bool CCrypter::SetKeyFromPassphrase(const SecureString& strKeyData, const std::vector<unsigned char>& chSalt, const unsigned int nRounds, const unsigned int nDerivationMethod)
 {
@@ -22,8 +48,7 @@ bool CCrypter::SetKeyFromPassphrase(const SecureString& strKeyData, const std::v
 
     int i = 0;
     if (nDerivationMethod == 0)
-        i = EVP_BytesToKey(EVP_aes_256_cbc(), EVP_sha512(), &chSalt[0],
-                          (unsigned char *)&strKeyData[0], strKeyData.size(), nRounds, chKey, chIV);
+        i = BytesToKeySHA512AES(chSalt, strKeyData, nRounds, chKey, chIV);
 
     if (i != (int)WALLET_CRYPTO_KEY_SIZE)
     {

src/wallet/crypter.h

@@ -75,6 +75,8 @@ class CCrypter
     unsigned char chIV[WALLET_CRYPTO_IV_SIZE];
     bool fKeySet;
 
+    int BytesToKeySHA512AES(const std::vector<unsigned char>& chSalt, const SecureString& strKeyData, int count, unsigned char *key,unsigned char *iv) const;
+
 public:
     bool SetKeyFromPassphrase(const SecureString &strKeyData, const std::vector<unsigned char>& chSalt, const unsigned int nRounds, const unsigned int nDerivationMethod);
     bool Encrypt(const CKeyingMaterial& vchPlaintext, std::vector<unsigned char> &vchCiphertext) const;