how to store PE32+ preferred imageBase address? - c++

Question

I have this PE loader that works really fine with 32bit PEs but with x64 ones it can't allocate the 0X0000000140000000 preferred base address since it only reads it as 0X40000000.
Here is how I allocate that address:
DWORD hdr_image_base = p_NT_HDR->OptionalHeader.ImageBase;
char* ImageBase = (char*)VirtualAlloc((void*)hdr_image_base, size_of_image, MEM_RESERVE | MEM_COMMIT, PAGE_READWRITE);
but when I hardcode the address It works just fine:
char* ImageBase = (char*)VirtualAlloc((void*)0X140000000, size_of_image, MEM_RESERVE | MEM_COMMIT, PAGE_READWRITE);
Is DWORD not enough to store the address?
this reallocation code is stripping some variable-length somewhere since it still works with 32 but not with x64:
//this is how much we shifted the ImageBase
DWORD_PTR delta_VA_reloc = (reinterpret_cast<DWORD_PTR>(ImageBase)) - p_NT_HDR->OptionalHeader.ImageBase;
// if there is a relocation table, and we actually shitfted the ImageBase
if (data_directory[IMAGE_DIRECTORY_ENTRY_BASERELOC].VirtualAddress != 0 && delta_VA_reloc != 0) {
printf("\n[*] The relocated address is not the prefered address, started relocating\n");
//calculate the relocation table address
IMAGE_BASE_RELOCATION* p_reloc = (IMAGE_BASE_RELOCATION*)(ImageBase + data_directory[IMAGE_DIRECTORY_ENTRY_BASERELOC].VirtualAddress);
//once again, a null terminated array
while (p_reloc->VirtualAddress != 0) {
// how many relocations in this block
// ie the total size, minus the size of the "header", divided by 2 (those are words, so 2 bytes for each)
//std::cout << sizeof(WORD) << "\n"; sizeof word is 2
DWORD size = (p_reloc->SizeOfBlock - sizeof(IMAGE_BASE_RELOCATION)) / sizeof(WORD);
// the first relocation element in the block, right after the header (using pointer arithmetic again)
WORD* reloc = (WORD*)(p_reloc + 1);
for (int i = 0; i < size; ++i) {
//type is the first 4 bits of the relocation word
int type = reloc[i] >> 12;
// offset is the last 12 bits
unsigned long long int offset = reloc[i] & 0x0fff;
//printf("--------------- %#llx\n", offset);
//this is the address we are going to change
DWORD* change_addr = (DWORD*)(ImageBase + p_reloc->VirtualAddress + offset);
// there is only one type used that needs to make a change
// When you relocate you should look if the flag HIGHT_LOW is active for PE32 and DIR64 for PE32+
switch (type) {
case IMAGE_REL_BASED_HIGHLOW://for x86
*change_addr += delta_VA_reloc;
break;
case IMAGE_REL_BASED_DIR64://for x64
*change_addr += delta_VA_reloc;
break;
default:
break;
}
}
// switch to the next relocation block, based on the size
p_reloc = (IMAGE_BASE_RELOCATION*)((reinterpret_cast<DWORD_PTR>(p_reloc)) + p_reloc->SizeOfBlock);
}
}