reversehard

another-onion

DiceCTF 2026 Quals

Task: Self-decrypting onion binary with 256 layers, each requiring 2-byte key brute-force using SHA-NI derived keystream, 30-minute time limit. Solution: JIT execution with fork/COW isolation and 32 parallel workers achieving ~3500 candidates/sec.

$ ls tags/ techniques/

brute_force xor_decryption x86_64 self_modifying_code sha256_ni layered_encryption jit_execution fork_cow parallel_processing time_limited

jit_code_executionfork_cow_isolationparallel_brute_forceoracle_based_decryptionmmap_fixed_addressptrace_state_extractionsignal_handler_recoveryshared_memory_optimization

Analysis

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$ python3 exploit.py --target 192.168.1.1 --port 8080
[*] Connecting to target...
[+] Shell obtained!

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