Phase 5 (150 pts)

Getting more spicy...

Problem Statement

Are you really, really ready and excited for this stage?

(Flag uses the same rockyou.txt format as BBomb Phase 4)

Update: No input numberis below 2010 and each number increasingly larger than the previous

Author: treap_treap

Analysing

Let's take a look at what Ghidra tells us. There is a function which I have named prime because that is exactly what it does.

phase5

uint phase5(undefined8 param_1,undefined4 param_2,undefined4 param_3,undefined4 param_4,
           undefined4 param_5,undefined4 param_6,undefined4 param_7,undefined4 param_8,char *param_9
           )

{
  void *inputPtr;
  undefined8 uVar1;
  undefined4 extraout_XMM0_Da;
  uint result;
  int sum;
  int counter;
  
  puts("\nAre you really, really ready and excited for this stage?");
  result = 1;
  inputPtr = calloc(4,4);
  getInput(extraout_XMM0_Da,param_2,param_3,param_4,param_5,param_6,param_7,param_8,5,param_9,
           "%d%d%d%d",inputPtr,(long)inputPtr + 4,(long)inputPtr + 8,(char)inputPtr + '\f');
  sum = 0;
  counter = 0;
  while (counter < 4) {
    if ((0 < counter) && ((int)param_9[(long)counter + -1] < param_9[counter] + -10)) {
      result = 0;
    }
    uVar1 = prime(*(uint *)((long)inputPtr + (long)counter * 4));
    result = result & (uint)uVar1;
    sum = sum + *(int *)((long)inputPtr + (long)counter * 4);
    counter = counter + 1;
  }
  if (sum != 0x1f94) {
    result = 0;
  }
  free(inputPtr);
  return result;
}

prime

undefined8 prime(uint num)

{
  undefined8 result;
  int local_c;
  
  if (((num & 1) == 0) || ((int)num < 2)) {
    result = 0;
  }
  else {
    local_c = 3;
    while (local_c < (int)num / 2) {
      if ((int)num % local_c == 0) {
        return 0;
      }
      local_c = local_c + 2;
    }
    result = 1;
  }
  return result;
}

Solve.py

We can see from the decompiler that every integer must be greater than the previous and the program accepts 4 different numbers.

for i in range(2010, 2050):
    prime = True
    if (i & 1 == 0):
        continue
    for j in range(3, i // 2 + 1, 2):
        if (i % j == 0):
            prime = False
            break
    if (prime):
        print(i)

Output

We have to choose 4 which adds up to 0x1f94 which equates to the decimal value of 8084.

Hence, the values are: 2011, 2017, 2027, 2029.

Flag

DawgCTF{kayla1_harris_ilovemike_valencia}