give Lua access to tomcrypt's SHA256

This adds Lua hooks to CryptManager for libtomcrypt's SHA256 hash
function.  It follows along with the C++ patterns Glenn wrote a decade
and a half ago for CryptMananger's MD5 and SHA1 hooks.

StepMania's CMakeProject-tomcrypt file has been updated to build with
sha256 symbols.  Invoking cmake to build with system tomcrypt works fine
as-is.

Note that these functions return binary formatted strings, but themers
can convert to hexadecimal format using the global Lua function
BinaryToHex().

src/CryptManager.cpp

@@ -420,6 +420,37 @@ RString CryptManager::GetSHA1ForFile( RString fn )
 	return RString( (const char *) digest, sizeof(digest) );
 }
 
+RString CryptManager::GetSHA256ForString( RString sData )
+{
+	unsigned char digest[32];
+
+	int iHash = register_hash( &sha256_desc );
+
+	hash_state hash;
+	hash_descriptor[iHash].init( &hash );
+	hash_descriptor[iHash].process( &hash, (const unsigned char *) sData.data(), sData.size() );
+	hash_descriptor[iHash].done( &hash, digest );
+
+	return RString( (const char *) digest, sizeof(digest) );
+}
+
+RString CryptManager::GetSHA256ForFile( RString fn )
+{
+	RageFile file;
+	if( !file.Open( fn, RageFile::READ ) )
+	{
+		LOG->Warn( "GetSHA256: Failed to open file '%s'", fn.c_str() );
+		return RString();
+	}
+	int iHash = register_hash( &sha256_desc );
+	ASSERT( iHash >= 0 );
+
+	unsigned char digest[32];
+	HashFile( file, digest, iHash );
+
+	return RString( (const char *) digest, sizeof(digest) );
+}
+
 RString CryptManager::GetPublicKeyFileName()
 {
 	return PUBLIC_KEY_PATH;
@@ -478,6 +509,20 @@ public:
 		lua_pushlstring(L, sha1fout, sha1fout.size());
 		return 1;
 	}
+	static int SHA256String( T* p, lua_State *L )
+	{
+		RString sha256out;
+		sha256out = p->GetSHA256ForString(SArg(1));
+		lua_pushlstring(L, sha256out, sha256out.size());
+		return 1;
+	}
+	static int SHA256File( T* p, lua_State *L )
+	{
+		RString sha256fout;
+		sha256fout = p->GetSHA256ForFile(SArg(1));
+		lua_pushlstring(L, sha256fout, sha256fout.size());
+		return 1;
+	}
 	static int GenerateRandomUUID( T* p, lua_State *L )
 	{
 		RString uuidOut;
@@ -492,6 +537,8 @@ public:
 		ADD_METHOD( MD5File );
 		ADD_METHOD( SHA1String );
 		ADD_METHOD( SHA1File );
+		ADD_METHOD( SHA256String );
+		ADD_METHOD( SHA256File );
 		ADD_METHOD( GenerateRandomUUID );
 	}
 };