🪡Needle in a Haystack(s)

This page will include writeups for all 5 Needles in a Haystack

Needle in a Haystack

We are given 100 text files that seem to contain fake flags, we can safely assume that the real flag is hidden within the 100 text files.

Below is a script that iterates through every text file and looks for unique flags:

solution.py

unique = []
for i in range(1, 100):
    with open(f"../hell_naw/file{i}.txt", "r") as f:
        temp = f.read()
        if temp not in unique:
            unique.append(temp)
print(unique)

# CTF101{ThaT5_4_lOt_0f_FlaGS}

Needle in a Haystack 2

We are given 400 text files, and they all contain different fake flags this time

We can actually reuse the same script from the previous challenge to print out the unique flags and find the non-fake flag.

solve.py

unique = []
for i in range(1, 400):
    with open(f"../hell_naw_2/file{i}.txt", "r") as f:
        temp = f.read()
        if temp not in unique:
            unique.append(temp)
print(unique)

# CTF101{Hey_you_fouND_ThE_flAG}

Needle in a Haystack 3

We are now given uh.. 1350 text files, and.. they contain rick roll lyrics... man who made this challenge...

The first 3 text files confirm that the flag is scattered across the 1350 files, but they are always on the first line.

The following python script iterates through all the text files and attempts to identify if the first line of the text file contains a non white-space character, if not- print it.

solve.py

lines = []
for i in range(0, 1351):
    with open(f"../hell_naw_3/file{i}.txt", "r") as f:
        line = f.readline().strip()
        if line:
            lines.append(line)

print("".join(lines))

# CTF101{rIcK_rolld}

Needle in a Haystack 4

We are given 871 text files that each contain 1 alphabet, matching up the first couple alphabets show a fake flag.

The following python script combines the concepts from the last challenges; it iterates through the first character of every text file and appends it to form a string of length 35, then unique flags are extracted.

solve.py

unique = []

for i in range(0, 900, 35):
    temp = ''
    for j in range(i, i+35):
        try:
            with open(f"../hell_naw_4/file{j}.txt", "r") as f:
                temp += f.read()
        except:
            pass
    if temp not in unique:
        unique.append(temp)

print(unique)

# CTF101{Br0_7H1s_CH4l1En9E_I5_FuNny}

Needle in a Haystack 5

The final challenge of the pantology! Cool, so we are given... 3134 text files...

Anyway, this challenge is actually the easiest of the 5 :D. Just join the text files together and scroll around to find the flag :P

solve.py

letter_list = ""
for i in range(0, 3134):
    try:
        with open(f"../hell_naw_5/file{i}.txt", "r") as f:
            letter_list += f.read()
    except FileNotFoundError:
        pass

print(letter_list)

# CTF101{a1DeN_rICk_roll3D_yOu}

Making the final challenge the easiest was truly an evil decision; but it's called sanity check for a reason! (you don't need to complete the challenges in order)