Additive-progression deobfuscation

Some SA17-derived stores ship with an extra obfuscation pass on top of the page-store layer. The most prominent example is the Intuit QuickBooks Desktop .QBW format, which is an SA17 page store with a deterministic additive-progression keystream XORed across each page.

opensqlany::ApModel is the in-memory adapter that peels this layer off. It does not commit the result to disk and does not break any DRM - the obfuscation is a public, deterministic byte transformation that the lawful owner of the file can already reverse via the QuickBooks application.

Peeling the AP layer off

use opensqlany::{ApModel, PageStore};

let store = PageStore::open("Company.QBW")?;
let model = ApModel::learn(&store);

let page = store.page(1)?;
let plain = model.deobfuscate_with_store(page.bytes(), page.index(), &store);
// `plain` is now SA17 plaintext for this page; proceed as for a
// plaintext SA17 file (e.g. feed it to `SlottedPage::parse` via
// `Page::from_bytes`).
# Ok::<(), opensqlany::Error>(())

ApModel::learn scans every "pure-AP" page in the store (page types '@', 'C', 'H', 'M') to calibrate the per-block bv value used by the keystream formula below. It always succeeds - there is no separate detection step. Use the CLI's ap-info subcommand to check how many blocks were calibrated directly (learned_block_count) versus falling back to on-demand recovery (deobfuscate_with_store) or the block-0 approximation (deobfuscate).

bv is constant per 16-page block on the original corpus, but not on every file - some QuickBooks Enterprise 24.0 files vary bv from page to page within a block. deobfuscate_with_store always resolves bv for the specific page being decoded rather than trusting its block's learned value, so it stays correct either way; only the cheaper block-only deobfuscate is affected by this.

Companion: OpenQBW

OpenQBW is the companion project that builds the QuickBooks business-object layer on top. It uses ApModel for the obfuscation peel, then drives opensqlany for the page walk, then layers Intuit's schema on top of the resulting catalog rows.

Full algorithm

See Specification, section "AP keystream", for the byte-level derivation of the keystream from the file header.