peass-ng/PEASS-ng · error · InvalidOperationException

Should never get here

Error message

Should never get here

What it means

GenerateWorkingKey's key-schedule switch has cases only for the valid key control-word counts; the default case throws InvalidOperationException("Should never get here"). It is unreachable through the public API because key length is validated earlier, but signals internal corruption if hit.

Solutions

1. Use the library unmodified and validate key length (16/24/32) before Init
2. Restore the original AesEngine.cs from the official BouncyCastle source
3. If you patched the code, re-add the length guard before the switch

// unreachable via public API; just ensure key length is 16/24/32 before Init

static bool IsValidAesKey(byte[] key) => key != null && (key.Length == 16 || key.Length == 24 || key.Length == 32);

try { cipher.Init(forEncryption, new KeyParameter(key)); } catch (InvalidOperationException ex) { /* treat as library integrity failure: ex.Message == "Should never get here" */ }

When it happens

Trigger: Only reachable if the key-length guard at the top of GenerateWorkingKey was bypassed or modified, producing a KC value outside {4,6,8}.

Common situations: A patched/modified BouncyCastle build, memory corruption, or custom subclassing that calls GenerateWorkingKey directly with unvalidated key lengths.

Related errors

• AES engine not initialised
• invalid parameter passed to AES init -
• Key length not 128/192/256 bits.
• attempt to absorb with odd length queue
• Decryption failed due to MAC mismatch

AI-assisted analysis of peass-ng/PEASS-ng@53fb989abc (2026-09-02). Data as JSON: /api/errors/17e22b3cb7cbe0cb. Report an issue: GitHub.

Appendix: source

Thrown at winPEAS/winPEASexe/winPEAS/3rdParty/BouncyCastle/crypto/engines/AesEngine.cs:405

                            t3 ^= t2; W[i][3] = t3;
                            u = SubWord(t3);
                            t4 ^= u; W[i + 1][0] = t4;
                            t5 ^= t4; W[i + 1][1] = t5;
                            t6 ^= t5; W[i + 1][2] = t6;
                            t7 ^= t6; W[i + 1][3] = t7;
                        }

                        u = SubWord(Shift(t7, 8)) ^ rcon;
                        t0 ^= u; W[14][0] = t0;
                        t1 ^= t0; W[14][1] = t1;
                        t2 ^= t1; W[14][2] = t2;
                        t3 ^= t2; W[14][3] = t3;

                        break;
                    }
                default:
                    {
                        throw new InvalidOperationException("Should never get here");
                    }
            }

            if (!forEncryption)
            {
                for (int j = 1; j < ROUNDS; j++)
                {
                    uint[] w = W[j];
                    for (int i = 0; i < 4; i++)
                    {
                        w[i] = Inv_Mcol(w[i]);
                    }
                }
            }

            return W;
        }

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