Fix core subsystem logic and safety bugs @Sirus20x6

src/core/download_list.cc

@@ -1,6 +1,7 @@
 #include "config.h"
 
 #include <algorithm>
+#include <cstring>
 #include <fstream>
 #include <iostream>
 #include <torrent/data/file.h>
@@ -82,6 +83,9 @@ DownloadList::find(const torrent::HashString& hash) {
 
 DownloadList::iterator
 DownloadList::find_hex(const char* hash) {
+  if (strlen(hash) < 40)
+    return end();
+
   torrent::HashString key;
 
   if (torrent::utils::transform_from_hex(hash, hash + 40, key) != key.end())

src/core/manager.cc

@@ -238,9 +238,10 @@ is_data_uri(const std::string& uri) {
 
 std::string
 decode_data_uri(const std::string& uri) {
-  const auto start = uri.find("base64,", 5) + 7;
-  if (start == std::string::npos)
+  const auto pos = uri.find("base64,", 5);
+  if (pos == std::string::npos)
     throw torrent::input_error("Invalid data uri: not base64 encoded.");
+  const auto start = pos + 7;
   if (start >= uri.size())
     throw torrent::input_error("Empty base64.");
   return utils::decode_base64(uri.substr(start));