static void cgc_initialize_flag_page(void) {
// Initially reserve the flag page to see where it ends up
LPVOID flag_addr, rsrv_addr = VirtualAlloc(CGC_FLAG_PAGE_ADDRESS, PAGE_SIZE,
MEM_RESERVE, PAGE_READWRITE);
if (rsrv_addr != CGC_FLAG_PAGE_ADDRESS) {
// Address was rounded down
// Figure out how much more space we need to reserve
intptr_t padding = CGC_FLAG_PAGE_ADDRESS - (intptr_t) rsrv_addr;
// Free the old space and reserve the correct size
VirtualFree(rsrv_addr, 0, MEM_RELEASE);
rsrv_addr = VirtualAlloc(rsrv_addr, PAGE_SIZE + padding,
MEM_RESERVE, PAGE_READWRITE);
}
// Allocate the flag page
flag_addr = VirtualAlloc(CGC_FLAG_PAGE_ADDRESS, PAGE_SIZE,
MEM_COMMIT, PAGE_READWRITE);
// Make sure it worked
if (flag_addr != CGC_FLAG_PAGE_ADDRESS) {
fprintf(stderr, "[!] Failed to map the flag page");
exit(1);
}
// Fill the flag page with bytes from the prng
cgc_try_init_prng();
cgc_aes_get_bytes(cgc_internal_prng, PAGE_SIZE, flag_addr);
}
int cgc_random(void *buf, cgc_size_t count, cgc_size_t *rnd_bytes) {
// Get random bytes from the prng
cgc_try_init_prng();
cgc_aes_get_bytes(cgc_internal_prng, count, buf);
if (rnd_bytes)
*rnd_bytes = count;
return 0;
}
static void __attribute__ ((constructor)) cgc_initialize_flag_page(void) {
void *mmap_addr = mmap(CGC_FLAG_PAGE_ADDRESS, PAGE_SIZE,
PROT_READ | PROT_WRITE,
MAP_FIXED | MAP_PRIVATE | MAP_ANONYMOUS,
-1, 0);
if (mmap_addr != CGC_FLAG_PAGE_ADDRESS) {
err(1, "[!] Failed to map the flag page");
}
// Fill the flag page with bytes from the prng
try_init_prng();
cgc_aes_get_bytes(cgc_internal_prng, PAGE_SIZE, mmap_addr);
}
