fix potential buffer overflow in deck code import/export module (#61)

gframe/base64.h

@@ -2,6 +2,7 @@
 #define BASE64_H
 
 #include <string>
+#include <cstring>
 
 const char kBase64Alphabet[] = "ABCDEFGHIJKLMNOPQRSTUVWXYZ"
     "abcdefghijklmnopqrstuvwxyz"
@@ -60,8 +61,10 @@ class Base64 {
 
     size_t encoded_length = EncodedLength(input_length);
 
-    if (out_length < encoded_length) return false;
-
+    if (out_length < encoded_length + 1) return false;
+    
+    std::memset(out, 0, out_length);
+    
     while (input_length--) {
       a3[i++] = *input++;
       if (i == 3) {

gframe/deck_manager.cpp

@@ -322,7 +322,7 @@ int DeckManager::TypeCount(std::vector<code_pointer> list, unsigned int ctype) {
 bool DeckManager::LoadDeckFromCode(Deck& deck, const char *code, int len) {
 	char data[1024], *pdeck = data, *data_ = data;
 	int decoded_len = Base64::DecodedLength(code, len);
-	if(decoded_len < 8 || !Base64::Decode(code, len, data_, decoded_len))
+	if(decoded_len > 1024 || decoded_len < 8 || !Base64::Decode(code, len, data_, decoded_len))
 		return false;
 	int mainc = BufferIO::ReadInt32(pdeck);
 	int sidec = BufferIO::ReadInt32(pdeck);
@@ -341,7 +341,7 @@ int DeckManager::SaveDeckToCode(Deck& deck, char* code) {
 		BufferIO::WriteInt32(pdeck, deck.side[i]->first);
 	int len = pdeck - deckbuf;
 	int encoded_len = Base64::EncodedLength(len);
-	Base64::Encode(deckbuf, len, code, encoded_len);
+	Base64::Encode(deckbuf, len, code, encoded_len+1);
 	return encoded_len;
 }
 bool DeckManager::CreateCategory(const wchar_t* name) {