libfreemkv/src/disc/encrypt.rs

//! AACS encryption resolution — key derivation, SCSI handshake, VUK lookup.

use super::*;
use crate::error::{Error, Result};
use crate::sector::SectorReader;
use crate::udf;

/// Result of SCSI AACS handshake (ECDH authentication).
/// Only available when scanning from a real drive, not ISO images.
#[derive(Debug)]
pub(super) struct HandshakeResult {
    pub volume_id: [u8; 16],
    pub read_data_key: Option<[u8; 16]>,
}

impl Disc {
    /// SCSI handshake result — volume ID and bus keys from ECDH authentication.
    /// Only available when scanning from a real drive (not ISO images).
    pub(super) fn do_handshake(
        session: &mut crate::drive::Drive,
        opts: &ScanOptions,
    ) -> Option<HandshakeResult> {
        use crate::aacs::{self, KeyDb};

        let keydb_path = opts.resolve_keydb()?;
        let keydb = KeyDb::load(&keydb_path).ok()?;

        const MAX_CERT_ATTEMPTS: usize = 16;
        for hc in keydb.host_certs.iter().take(MAX_CERT_ATTEMPTS) {
            match aacs::handshake::aacs_authenticate(session, &hc.private_key, &hc.certificate) {
                Ok(mut auth) => {
                    let volume_id = match aacs::handshake::read_volume_id(session, &mut auth) {
                        Ok(vid) => vid,
                        Err(_) => return None, // handshake succeeded but can't read VID
                    };
                    let read_data_key = aacs::handshake::read_data_keys(session, &mut auth)
                        .ok()
                        .map(|(rdk, _)| rdk);
                    return Some(HandshakeResult {
                        volume_id,
                        read_data_key,
                    });
                }
                Err(_) => {
                    continue;
                }
            }
        }
        // All host certs failed — return None, not a fake success
        None
    }

    /// Resolve disc encryption — AACS 1.0, AACS 2.0, CSS, or none.
    ///
    /// Reads AACS files from UDF (via SectorReader), resolves keys through
    /// whatever path works: KEYDB VUK lookup, media key derivation, processing
    /// keys, device keys. Uses handshake result (volume ID, bus key) if available.
    pub(super) fn resolve_encryption(
        udf_fs: &udf::UdfFs,
        reader: &mut dyn SectorReader,
        keydb_path: &std::path::Path,
        handshake: Option<&HandshakeResult>,
    ) -> Result<AacsState> {
        use crate::aacs::{self, KeyDb};

        let keydb = KeyDb::load(keydb_path).map_err(|_| Error::KeydbLoad {
            path: keydb_path.display().to_string(),
        })?;

        // Read AACS files from disc/image via UDF
        let uk_ro_data = udf_fs
            .read_file(reader, "/AACS/Unit_Key_RO.inf")
            .or_else(|_| udf_fs.read_file(reader, "/AACS/DUPLICATE/Unit_Key_RO.inf"))
            .map_err(|_| Error::AacsNoKeys)?;

        let cc_data = udf_fs
            .read_file(reader, "/AACS/Content000.cer")
            .or_else(|_| udf_fs.read_file(reader, "/AACS/Content001.cer"))
            .ok();

        let mkb_data = udf_fs
            .read_file(reader, "/AACS/MKB_RW.inf")
            .or_else(|_| udf_fs.read_file(reader, "/AACS/MKB_RO.inf"))
            .ok();
        let mkb_ver = mkb_data.as_deref().and_then(aacs::mkb_version);

        // Use handshake volume ID if available, otherwise zeros
        // (KEYDB VUK lookup by disc hash works without volume ID)
        let volume_id = handshake.map(|h| h.volume_id).unwrap_or([0u8; 16]);
        let read_data_key = handshake.and_then(|h| h.read_data_key);

        // Resolve: tries all available paths — KEYDB VUK, media key, processing key, device key
        let resolved = aacs::resolve_keys(
            &uk_ro_data,
            cc_data.as_deref(),
            &volume_id,
            &keydb,
            mkb_data.as_deref(),
        )
        .ok_or(Error::AacsNoKeys)?;

        Ok(AacsState {
            version: if resolved.aacs2 { 2 } else { 1 },
            bus_encryption: resolved.bus_encryption,
            mkb_version: mkb_ver,
            disc_hash: aacs::disc_hash_hex(&resolved.disc_hash),
            key_source: match resolved.key_source {
                1 => KeySource::KeyDb,
                2 => KeySource::KeyDbDerived,
                3 => KeySource::ProcessingKey,
                4 => KeySource::DeviceKey,
                _ => KeySource::KeyDb,
            },
            vuk: resolved.vuk,
            unit_keys: resolved.unit_keys,
            read_data_key,
            volume_id,
        })
    }
}