cleanup

2026/cscg/rev/gloomweaver/find_hash.py

@@ -0,0 +1,28 @@
+# find_hash.py — find a flag that passes the checksum
+import struct
+
+def compute_hash(flag_bytes):
+    eax = 0x65
+    for b in flag_bytes:
+        ecx = eax & 0xFFFFFFFF
+        edx = eax & 0xFF  # dl only
+        ecx = (ecx << 6) & 0xFFFFFFFF
+        edx = (edx >> 6) & 0xFF
+        eax = (eax + ecx) & 0xFFFFFFFF
+        eax = (eax + edx) & 0xFFFFFFFF
+        eax ^= b
+    return eax & 0xFF
+
+prefix = b"CTF{th1s_"
+suffix = b"}"
+# 64 bytes total: 9 prefix + 54 middle + 1 suffix
+# Try different last middle byte
+for last in range(0x21, 0x7F):
+    middle = b"A" * 53 + bytes([last])
+    flag = prefix + middle + suffix
+    assert len(flag) == 64
+    h = compute_hash(flag)
+    if h == 0x0C:
+        print(f"Found: {flag.decode()}")
+        print(f"Hash: 0x{h:02x}")
+        break