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c++winapiregistry

Why does RegOpenKeyExA fail to open a key path with a space in the name?

Why does RegOpenKeyExA throw a path not found error according to the error codes from Microsoft docs

other paths (no spaces) do open flawlessly


int res;
HKEY hKey;
res = RegOpenKeyExA(HKEY_CURRENT_USER, "SOFTWARE\\Policies\\Microsoft\\Windows Defender",
                     0, KEY_QUERY_VALUE|KEY_WRITE|KEY_READ|KEY_SET_VALUE, &hKey);
std::cout << " Error code ["+res+"]"<<std::endl;

the error code I am getting is 2

I am running the compiled executable as admin

Solution

  • RegOpenKeyEx() allows spaces just fine. MANY Registry keys have spaces in their names.

    Error 2 is ERROR_FILE_NOT_FOUND, which means the key you are trying to open does not exist. And indeed, the Windows Defender key does not exist in HKEY_CURRENT_USER, it exists in HKEY_LOCAL_MACHINE instead.

    image

    BTW, KEY_WRITE includes KEY_SET_VALUE (among others), and KEY_READ includes KEY_QUERY_VALUE (among others), so technically you are opening the key with just KEY_WRITE|KEY_READ. Which is likely to fail unless your program is running with elevated permissions, since most of HKEY_LOCAL_MACHINE is read-only to non-admin users. It is rarely of good idea to open a key under HKEY_LOCAL_MACHINE for both read and write permissions at the same time. If you need to read something, open the key for read-only access, which is likely to succeed. If you need to write something, open the key for write-only access, which will succeed only if you have permission to write.