pagedb 0.1.0-beta.6

use crate::RealmId;
use crate::crypto::Cipher;
use crate::crypto::kdf::{derive_dek, derive_hk, derive_mk};
use crate::crypto::nonce::Nonce;
use crate::errors::PagedbError;

use super::{
    FOOTER_CLEARTEXT_END, FOOTER_FIELDS_END, FORMAT_VERSION, SegmentFooterFields,
    decode_segment_footer, encode_segment_footer, max_manifest_len,
};

const PAGE_SIZE: usize = 4096;

fn keys() -> (crate::crypto::keys::DerivedKey, Cipher) {
    let master = derive_mk(&[7; 32], &[0; 16], 0).unwrap();
    let header = derive_hk(&master).unwrap();
    let data = derive_dek(&master, RealmId([3; 16]), &[9; 16]).unwrap();
    (header, Cipher::new_aes_gcm(&data))
}

fn fields() -> SegmentFooterFields {
    SegmentFooterFields {
        format_version: FORMAT_VERSION,
        cipher_id: 1,
        segment_id: [9; 16],
        parent_file_id: [1; 16],
        realm_id: RealmId([3; 16]),
        mk_epoch: 0,
        page_count: 10,
        total_bytes: 40_960,
        final_counter: 9,
        index_start_page: 0,
        index_page_count: 0,
    }
}

#[test]
fn round_trip_preserves_manifest_and_authenticated_fields() {
    let (header, cipher) = keys();
    let expected = fields();
    let encoded =
        encode_segment_footer(&expected, b"manifest", &header, &cipher, PAGE_SIZE).unwrap();
    let (actual, manifest) = decode_segment_footer(&encoded, &header, &cipher, PAGE_SIZE).unwrap();
    assert_eq!(actual, expected);
    assert_eq!(manifest, b"manifest");
}

#[test]
fn rejects_manifest_larger_than_footer_payload() {
    let (header, cipher) = keys();
    let err = encode_segment_footer(
        &fields(),
        &vec![0; max_manifest_len(PAGE_SIZE) + 1],
        &header,
        &cipher,
        PAGE_SIZE,
    )
    .unwrap_err();
    assert!(matches!(err, PagedbError::ManifestTooLarge));
}

#[test]
fn rejects_footer_nonce_beyond_u48_counter_space() {
    let (header, cipher) = keys();
    let mut exhausted = fields();
    exhausted.final_counter = Nonce::COUNTER_MAX;
    assert!(matches!(
        encode_segment_footer(&exhausted, b"manifest", &header, &cipher, PAGE_SIZE),
        Err(PagedbError::NonceCounterExhausted)
    ));

    exhausted.final_counter = Nonce::COUNTER_MAX - 1;
    assert!(encode_segment_footer(&exhausted, b"manifest", &header, &cipher, PAGE_SIZE).is_ok());
}

#[test]
fn rejects_footer_whose_declared_format_version_is_not_the_accepted_one() {
    let (header, cipher) = keys();
    let encoded =
        encode_segment_footer(&fields(), b"manifest", &header, &cipher, PAGE_SIZE).unwrap();
    // A version this build does not read is a migration problem, not damage:
    // the footer is refused by version rather than reported as bad framing, so
    // an operator is not sent looking for corruption that is not there.
    for declared in [FORMAT_VERSION - 1, FORMAT_VERSION + 1, u16::MAX] {
        let mut forged = encoded.clone();
        forged[8..10].copy_from_slice(&declared.to_le_bytes());
        assert!(
            matches!(
                decode_segment_footer(&forged, &header, &cipher, PAGE_SIZE),
                Err(PagedbError::FormatVersionUnsupported {
                    stored,
                    supported: FORMAT_VERSION,
                }) if stored == declared
            ),
            "format_version={declared} must be refused by version"
        );
    }
}

#[test]
fn refuses_to_encode_a_footer_under_an_unaccepted_format_version() {
    let (header, cipher) = keys();
    let mut unknown = fields();
    unknown.format_version = FORMAT_VERSION + 1;
    assert!(matches!(
        encode_segment_footer(&unknown, b"manifest", &header, &cipher, PAGE_SIZE),
        Err(PagedbError::Unsupported)
    ));
}

#[test]
fn rejects_header_mac_and_manifest_tampering() {
    let (header, cipher) = keys();
    let mut encoded =
        encode_segment_footer(&fields(), b"manifest", &header, &cipher, PAGE_SIZE).unwrap();
    encoded[FOOTER_FIELDS_END] ^= 1;
    assert!(matches!(
        decode_segment_footer(&encoded, &header, &cipher, PAGE_SIZE),
        Err(PagedbError::Corruption(_))
    ));

    let mut encoded =
        encode_segment_footer(&fields(), b"manifest", &header, &cipher, PAGE_SIZE).unwrap();
    encoded[FOOTER_CLEARTEXT_END] ^= 1;
    assert!(matches!(
        decode_segment_footer(&encoded, &header, &cipher, PAGE_SIZE),
        Err(PagedbError::Corruption(_))
    ));
}