libfreemkv/tests/pass_n_patch_fix.rs

//! Regression tests for Pass N (patch) fix — decrypt key inversion bug.
//!
//! Tests that decrypt_sectors is invoked correctly when opts.decrypt=true.
//! The 2026-05-03 bug at `libfreemkv/src/disc/mod.rs:1938-1942` inverted
//! the decrypt key arms, causing patch to pass DecryptKeys::None on encrypted discs.

use libfreemkv::{aacs, decrypt::DecryptKeys};

/// Test: decrypt_sectors with AACS keys actually decrypts units.
#[test]
fn decrypt_sectors_with_aacs_keys_works() {
    // Build an encrypted aligned unit
    let mut unit = vec![0xFFu8; aacs::content::ALIGNED_UNIT_LEN];

    // Set encryption flag (bits 6-7 of byte 0)
    unit[0] |= 0xC0;

    // Fill with recognizable pattern
    for (i, byte) in unit
        .iter_mut()
        .enumerate()
        .take(aacs::content::ALIGNED_UNIT_LEN)
        .skip(1)
    {
        *byte = ((i * 3 + 7) & 0xFF) as u8;
    }

    let unit_key: [u8; 16] = [0xAAu8; 16];

    // Apply the key to the pattern to produce ciphertext-shaped bytes for the
    // call below. (decrypt_unit is now PURE — it applies the key unconditionally,
    // so it is NOT idempotent; never call it twice on the same unit.)
    aacs::content::decrypt_unit(&mut unit, &unit_key);
    // (byte 0 keeps its CPI bits set from above, so `decrypt_sectors` recognises
    // this as encrypted content and actually applies the key.)

    let mut aacs_keys = DecryptKeys::Aacs {
        unit_keys: vec![(0u32, unit_key)],
        read_data_key: None,
        format: libfreemkv::disc::ContentFormat::BdTs,
    };
    let mut none_keys = DecryptKeys::None;

    // The regression this guards is passing `DecryptKeys::None` where AACS keys
    // were meant. Prove the two DIVERGE: AACS applies the key (bytes change), None
    // leaves the unit byte-for-byte untouched. is_ok alone can't catch that —
    // both variants return Ok.
    let mut with_aacs = unit.clone();
    let mut with_none = unit.clone();
    libfreemkv::decrypt::decrypt_sectors(&mut with_aacs, &mut aacs_keys, 0)
        .expect("AACS decrypt must not error");
    libfreemkv::decrypt::decrypt_sectors(&mut with_none, &mut none_keys, 0)
        .expect("None decrypt must not error");

    assert_ne!(
        with_aacs, unit,
        "AACS keys must actually transform the unit"
    );
    assert_eq!(with_none, unit, "None keys must leave the unit untouched");
    assert_ne!(
        with_aacs, with_none,
        "AACS decrypt must differ from the None no-op (the None-vs-Aacs regression)"
    );
}

/// Test: decrypt_sectors with DecryptKeys::None is a no-op.
#[test]
fn decrypt_sectors_with_none_keys_is_noop() {
    let mut sector = vec![0x42u8; 2048];

    let mut keys = DecryptKeys::None;
    let result = libfreemkv::decrypt::decrypt_sectors(&mut sector, &mut keys, 0);

    assert!(result.is_ok());
    assert_eq!(
        &sector[..],
        &[0x42u8; 2048][..],
        "DecryptKeys::None should not modify buffer"
    );
}

/// Test: decrypt_sectors with CSS keys descrambles sectors.
#[test]
fn decrypt_sectors_with_css_keys_works() {
    let mut sector = vec![0xFFu8; 2048];

    // Set CSS scramble flag (bits 4-5 of byte 0x14)
    sector[0x14] |= 0x30;

    let title_key: [u8; 5] = [0x42, 0x13, 0x37, 0xBE, 0xEF]; // Not used - defined later
    let mut keys = DecryptKeys::Css { title_key };

    // Descramble (CSS uses same operation for encrypt/decrypt)
    libfreemkv::decrypt::decrypt_sectors(&mut sector, &mut keys, 0).unwrap();

    // Flag should be cleared
    assert_eq!(sector[0x14] & 0x30, 0x00, "CSS flag should be cleared");
}

/// Test: AACS unit encryption detection works.
#[test]
fn aacs_encryption_flag_detection() {
    // A clear unit: TS syncs (0x47) intact at every 192-byte packet.
    let mut unit = vec![0u8; aacs::content::ALIGNED_UNIT_LEN];
    let mut off = 4;
    while off < aacs::content::ALIGNED_UNIT_LEN {
        unit[off] = 0x47;
        off += 192;
    }
    // Encryption is the scrambled body (TS syncs destroyed), NOT a flag bit.
    assert!(aacs::content::is_clean(
        &unit,
        libfreemkv::disc::ContentFormat::BdTs
    ));

    // Flag bits on a synced unit do not make it look encrypted.
    unit[0] = 0xC0;
    unit[7] = 0xC0;
    assert!(aacs::content::is_clean(
        &unit,
        libfreemkv::disc::ContentFormat::BdTs
    ));

    // Scrambled body (syncs gone) → encrypted.
    let scrambled = vec![0x99u8; aacs::content::ALIGNED_UNIT_LEN];
    assert!(!aacs::content::is_clean(
        &scrambled,
        libfreemkv::disc::ContentFormat::BdTs
    ));
}

/// Test: DecryptKeys::is_encrypted() correctly identifies encrypted state.
#[test]
fn decrypt_keys_is_encrypted_variants() {
    let none = DecryptKeys::None;
    assert!(!none.is_encrypted());

    let aacs = DecryptKeys::Aacs {
        unit_keys: vec![],
        read_data_key: None,
        format: libfreemkv::disc::ContentFormat::BdTs,
    };
    assert!(aacs.is_encrypted());

    let css = DecryptKeys::Css {
        title_key: [0u8; 5],
    };
    assert!(css.is_encrypted());
}