//! Implementation for onion service descriptors.
//!
//! An onion service descriptor is a document generated by an onion service and
//! uploaded to one or more HsDir nodes for clients to later download.  It tells
//! the onion service client where to find the current introduction points for
//! the onion service, and how to connect to them.
//!
//! An onion service descriptor is more complicated than most other
//! documentation types, because it is partially encrypted.

#![allow(dead_code, unused_variables, clippy::missing_panics_doc)] // TODO hs: remove.
mod desc_enc;

mod build;
mod inner;
mod middle;
mod outer;

pub use desc_enc::DecryptionError;

use crate::{ParseErrorKind as EK, Result};

use tor_checkable::signed::{self, SignatureGated};
use tor_checkable::timed::{self, TimerangeBound};
use tor_hscrypto::pk::{
    HsBlindId, HsClientDescEncKey, HsClientDescEncSecretKey, HsIntroPtSessionIdKey, HsSvcNtorKey,
};
use tor_hscrypto::{RevisionCounter, Subcredential};
use tor_linkspec::UnparsedLinkSpec;
use tor_llcrypto::pk::curve25519;
use tor_units::IntegerMinutes;

use smallvec::SmallVec;

use std::time::SystemTime;

#[cfg(feature = "hsdesc-inner-docs")]
#[cfg_attr(docsrs, doc(cfg(feature = "hsdesc-inner-docs")))]
pub use {inner::HsDescInner, middle::HsDescMiddle, outer::HsDescOuter};

#[cfg(feature = "hs-service")]
#[cfg_attr(docsrs, doc(cfg(feature = "hs-service")))]
pub use build::HsDescBuilder;

/// Metadata about an onion service descriptor, as stored at an HsDir.
///
/// This object is parsed from the outermost document of an onion service
/// descriptor, and used on the HsDir to maintain its index.  It does not
/// include the inner documents' information about introduction points, since the
/// HsDir cannot decrypt those without knowing the onion service's un-blinded
/// identity.
///
/// The HsDir caches this value, along with the original text of the descriptor.
pub struct StoredHsDescMeta {
    /// The blinded onion identity for this descriptor.  (This is the only
    /// identity that the HsDir knows.)
    blinded_id: HsBlindId,

    /// Information about the expiration and revision counter for this
    /// descriptor.
    idx_info: IndexInfo,
}

/// An unchecked StoredHsDescMeta: parsed, but not checked for liveness or validity.
pub type UncheckedStoredHsDescMeta =
    signed::SignatureGated<timed::TimerangeBound<StoredHsDescMeta>>;

/// Information about how long to hold a given onion service descriptor, and
/// when to replace it.
#[derive(Debug, Clone)]
struct IndexInfo {
    /// The lifetime in minutes that this descriptor should be held after it is
    /// received.
    lifetime: IntegerMinutes<u16>,
    /// The expiration time on the `descriptor-signing-key-cert` included in this
    /// descriptor.
    signing_cert_expires: SystemTime,
    /// The revision counter on this descriptor: higher values should replace
    /// older ones.
    revision: RevisionCounter,
}

/// A decrypted, decoded onion service descriptor.
///
/// This object includes information from both the outer (plaintext) document of
/// the descriptor, and the inner (encrypted) documents.  It tells the client the
/// information it needs to contact the onion service, including necessary
/// introduction points and public keys.
#[derive(Debug, Clone)]
pub struct HsDesc {
    /// Information about the expiration and revision counter for this
    /// descriptor.
    idx_info: IndexInfo,

    /// `KP_hsc_desc_enc`, the public key corresponding to the private key that
    /// we used to decrypt this descriptor.
    ///
    /// This is set to None if we did not have to use a private key to decrypt
    /// the descriptor.
    decrypted_with_id: Option<HsClientDescEncKey>,

    /// A list of recognized CREATE handshakes that this onion service supports.
    // TODO hs: this should probably be a caret enum, not an integer
    // TODO hs: Add this if we actually need it.
    // create2_formats: Vec<u32>,

    /// A list of authentication types that this onion service supports.
    auth_required: Option<SmallVec<[IntroAuthType; 2]>>,

    /// If true, this a "single onion service" and is not trying to keep its own location private.
    is_single_onion_service: bool,

    /// One or more introduction points used to contact the onion service.
    intro_points: Vec<IntroPointDesc>,
}

/// A type of authentication that is required when introducing to an onion
/// service.
#[non_exhaustive]
#[derive(Debug, Clone, Copy, Eq, PartialEq, derive_more::Display)]
pub enum IntroAuthType {
    /// Ed25519 authentication is required.
    #[display(fmt = "ed25519")]
    Ed25519,
}

/// Information in an onion service descriptor about a single
/// introduction point.
#[derive(Debug, Clone)]
pub struct IntroPointDesc {
    /// A list of link specifiers needed to extend a circuit to the introduction point.
    ///
    /// These can include public keys and network addresses.
    //
    // TODO hs: perhaps we should make certain link specifiers mandatory? That
    // would make it possible for IntroPointDesc to implement CircTarget.
    link_specifiers: Vec<UnparsedLinkSpec>,

    /// The key used to extend a circuit _to the introduction point_, using the
    /// ntor or ntor3 handshakes.  (`KP_ntor`)
    ipt_ntor_key: curve25519::PublicKey,

    /// A key used to identify the onion service at this introduction point.
    /// (`KP_hs_ipt_sid`)
    ipt_sid_key: HsIntroPtSessionIdKey,

    /// `KP_hss_ntor`, the key used to encrypt a handshake _to the onion
    /// service_ when using this introduction point.
    ///
    /// The onion service uses a separate key of this type with each
    /// introduction point as part of its strategy for preventing replay
    /// attacks.
    svc_ntor_key: HsSvcNtorKey,
}

/// An onion service after it has been parsed by the client, but not yet decrypted.
pub struct EncryptedHsDesc {
    /// The un-decoded outer document of our onion service descriptor.
    outer_doc: outer::HsDescOuter,
}

/// An unchecked HsDesc: parsed, but not checked for liveness or validity.
pub type UncheckedEncryptedHsDesc = signed::SignatureGated<timed::TimerangeBound<EncryptedHsDesc>>;

impl StoredHsDescMeta {
    // TODO hs: needs accessor functions too.  (Let's not use public fields; we
    // are likely to want to mess with the repr of these types.)

    /// Parse the outermost layer of the descriptor in `input`, and return the
    /// resulting metadata (if possible).
    pub fn parse(input: &str) -> Result<UncheckedStoredHsDescMeta> {
        let outer = outer::HsDescOuter::parse(input)?;
        Ok(outer.dangerously_map(|timebound| {
            timebound.dangerously_map(|outer| StoredHsDescMeta::from_outer_doc(&outer))
        }))
    }
}

impl HsDesc {
    // TODO hs: needs accessor functions too.  (Let's not use public fields; we
    // are likely to want to mess with the repr of these types.)

    /// Parse the outermost document of the descriptor in `input`, and validate
    /// that its identity is consistent with `blinded_onion_id`.
    ///
    /// On success, the caller will get a wrapped object which they must
    /// validate and then decrypt.
    pub fn parse(
        input: &str,
        // We don't actually need this to parse the HsDesc, but we _do_ need it to prevent
        // a nasty pattern where we forget to check that we got the right one.
        blinded_onion_id: &HsBlindId,
    ) -> Result<UncheckedEncryptedHsDesc> {
        let outer = outer::HsDescOuter::parse(input)?;
        let mut id_matches = false;
        let result = outer.dangerously_map(|timebound| {
            timebound.dangerously_map(|outer| {
                id_matches = blinded_onion_id == &outer.blinded_id();
                EncryptedHsDesc::from_outer_doc(outer)
            })
        });
        if !id_matches {
            // TODO hs: This errorkind is not quite right.
            return Err(
                EK::BadObjectVal.with_msg("onion service descriptor did not have the expected ID")
            );
        }

        Ok(result)
    }
}

impl EncryptedHsDesc {
    /// Attempt to decrypt both layers of encryption in this onion service
    /// descriptor.
    ///
    /// If `hsc_desc_enc` is provided, we use it to decrypt the inner encryption layer;
    /// otherwise, we require that the inner document is encrypted using the "no
    /// client authorization" method.
    ///
    /// Note that `hsc_desc_enc` must be a key *pair* - ie, a KP_hsc_desc_enc
    /// and corresponding KS_hsc_desc_enc. This function **does not check**
    /// this.
    //
    // TODO hs: I'm not sure that taking `hsc_desc_enc` as an argument is correct. Instead, maybe
    // we should take a set of keys?
    pub fn decrypt(
        self,
        subcredential: &Subcredential,
        hsc_desc_enc: Option<(&HsClientDescEncKey, &HsClientDescEncSecretKey)>,
    ) -> Result<TimerangeBound<SignatureGated<HsDesc>>> {
        let blinded_id = self.outer_doc.blinded_id();
        let revision_counter = self.outer_doc.revision_counter;
        let kp_desc_sign = self.outer_doc.desc_sign_key_id();

        // Decrypt the superencryption layer; parse the middle document.
        let middle = self.outer_doc.decrypt_body(subcredential).map_err(|e| {
            EK::BadObjectVal.with_msg("onion service descriptor superencryption failed.")
        })?;
        let middle = std::str::from_utf8(&middle[..])
            .map_err(|e| EK::BadObjectVal.with_msg("Bad utf-8 in middle document"))?;
        let middle = middle::HsDescMiddle::parse(middle)?;

        // Decrypt the encryption layer and parse the inner document.
        let inner = middle
            .decrypt_inner(
                &blinded_id,
                revision_counter,
                subcredential,
                hsc_desc_enc.map(|keys| keys.1),
            )
            .map_err(|e| {
                EK::BadObjectVal.with_msg("onion service descriptor encryption failed.")
            })?;
        let inner = std::str::from_utf8(&inner[..])
            .map_err(|e| EK::BadObjectVal.with_msg("Bad utf-8 in inner document"))?;
        let (cert_signing_key, time_bound) = inner::HsDescInner::parse(inner)?;

        if cert_signing_key.as_ref() != Some(kp_desc_sign) {
            return Err(EK::BadObjectVal
                .with_msg("Signing keys in inner document did not match those in outer document"));
        }

        // Construct the HsDesc!
        let time_bound = time_bound.dangerously_map(|sig_bound| {
            sig_bound.dangerously_map(|inner| HsDesc {
                idx_info: IndexInfo::from_outer_doc(&self.outer_doc),
                decrypted_with_id: hsc_desc_enc.map(|keys| keys.0.clone()),
                auth_required: inner.intro_auth_types,
                is_single_onion_service: inner.single_onion_service,
                intro_points: inner.intro_points,
            })
        });
        Ok(time_bound)
    }

    /// Create a new `IndexInfo` from the outer part of an onion service descriptor.
    fn from_outer_doc(outer_layer: outer::HsDescOuter) -> Self {
        EncryptedHsDesc {
            outer_doc: outer_layer,
        }
    }
}

impl IndexInfo {
    /// Create a new `IndexInfo` from the outer part of an onion service descriptor.
    fn from_outer_doc(outer: &outer::HsDescOuter) -> Self {
        IndexInfo {
            lifetime: outer.lifetime,
            signing_cert_expires: outer.desc_signing_key_cert.expiry(),
            revision: outer.revision_counter,
        }
    }
}

impl StoredHsDescMeta {
    /// Create a new `StoredHsDescMeta` from the outer part of an onion service descriptor.
    fn from_outer_doc(outer: &outer::HsDescOuter) -> Self {
        let blinded_id = outer.blinded_id();
        let idx_info = IndexInfo::from_outer_doc(outer);
        StoredHsDescMeta {
            blinded_id,
            idx_info,
        }
    }
}

#[cfg(test)]
mod test {
    // @@ begin test lint list maintained by maint/add_warning @@
    #![allow(clippy::bool_assert_comparison)]
    #![allow(clippy::clone_on_copy)]
    #![allow(clippy::dbg_macro)]
    #![allow(clippy::print_stderr)]
    #![allow(clippy::print_stdout)]
    #![allow(clippy::single_char_pattern)]
    #![allow(clippy::unwrap_used)]
    #![allow(clippy::unchecked_duration_subtraction)]
    //! <!-- @@ end test lint list maintained by maint/add_warning @@ -->
    use std::time::Duration;

    use super::*;
    use hex_literal::hex;
    use tor_checkable::{SelfSigned, Timebound};
    use tor_hscrypto::{pk::HsIdKey, time::TimePeriod};
    use tor_llcrypto::pk::ed25519;

    pub(super) const TEST_DATA: &str = include_str!("../../testdata/hsdesc1.txt");
    pub(super) const TEST_SUBCREDENTIAL: [u8; 32] =
        hex!("78210A0D2C72BB7A0CAF606BCD938B9A3696894FDDDBC3B87D424753A7E3DF37");

    // This HsDesc uses DescEnc authentication.
    pub(super) const TEST_DATA_2: &str = include_str!("../../testdata/hsdesc2.txt");
    pub(super) const TEST_DATA_TIMEPERIOD_2: u64 = 19397;
    // paozpdhgz2okvc6kgbxvh2bnfsmt4xergrtcl4obkhopyvwxkpjzvoad.onion
    pub(super) const TEST_HSID_2: [u8; 32] =
        hex!("781D978CE6CE9CAA8BCA306F53E82D2C993E5C91346625F1C151DCFC56D753D3");
    pub(super) const TEST_SUBCREDENTIAL_2: [u8; 32] =
        hex!("24A133E905102BDA9A6AFE57F901366A1B8281865A91F1FE0853E4B50CC8B070");
    // SACGOAEODFGCYY22NYZV45ZESFPFLDGLMBWFACKEO34XGHASSAMQ (base32)
    pub(super) const TEST_PUBKEY_2: [u8; 32] =
        hex!("900467008E194C2C635A6E335E7724915E558CCB606C50094476F9731C129019");
    // SDZNMD4RP4SCH4EYTTUZPFRZINNFWAOPPKZ6BINZAC7LREV24RBQ (base32)
    pub(super) const TEST_SECKEY_2: [u8; 32] =
        hex!("90F2D60F917F2423F0989CE9979639435A5B01CF7AB3E0A1B900BEB892BAE443");

    #[test]
    fn parse_meta_good() -> Result<()> {
        let meta = StoredHsDescMeta::parse(TEST_DATA)?
            .check_signature()?
            .check_valid_at(&humantime::parse_rfc3339("2023-01-23T15:00:00Z").unwrap())
            .unwrap();

        assert_eq!(
            meta.blinded_id.as_ref(),
            &hex!("43cc0d62fc6252f578705ca645a46109e265290343b1137e90189744b20b3f2d")
        );
        assert_eq!(
            Duration::try_from(meta.idx_info.lifetime).unwrap(),
            Duration::from_secs(60 * 180)
        );
        assert_eq!(
            meta.idx_info.signing_cert_expires,
            humantime::parse_rfc3339("2023-01-26T03:00:00Z").unwrap()
        );
        assert_eq!(meta.idx_info.revision, RevisionCounter::from(19655750));

        Ok(())
    }

    #[test]
    fn parse_desc_good() -> Result<()> {
        let wrong_blinded_id = [12; 32].into();
        let desc = HsDesc::parse(TEST_DATA, &wrong_blinded_id);
        assert!(desc.is_err());
        let blinded_id =
            hex!("43cc0d62fc6252f578705ca645a46109e265290343b1137e90189744b20b3f2d").into();
        let desc = HsDesc::parse(TEST_DATA, &blinded_id)?
            .check_signature()?
            .check_valid_at(&humantime::parse_rfc3339("2023-01-23T15:00:00Z").unwrap())
            .unwrap()
            .decrypt(&TEST_SUBCREDENTIAL.into(), None)?;
        let desc = desc
            .check_valid_at(&humantime::parse_rfc3339("2023-01-24T03:00:00Z").unwrap())
            .unwrap();
        let desc = desc.check_signature().unwrap();

        assert_eq!(
            Duration::try_from(desc.idx_info.lifetime).unwrap(),
            Duration::from_secs(60 * 180)
        );
        assert_eq!(
            desc.idx_info.signing_cert_expires,
            humantime::parse_rfc3339("2023-01-26T03:00:00Z").unwrap()
        );
        assert_eq!(desc.idx_info.revision, RevisionCounter::from(19655750));
        assert!(desc.decrypted_with_id.is_none());
        assert!(desc.auth_required.is_none());
        assert_eq!(desc.is_single_onion_service, false);
        assert_eq!(desc.intro_points.len(), 3);

        // TODO hs: add checks that the intro point fields are as expected.

        Ok(())
    }

    /// Get an EncryptedHsDesc corresponding to `TEST_DATA_2`.
    fn get_test2_encrypted() -> EncryptedHsDesc {
        let id: HsIdKey = ed25519::PublicKey::from_bytes(&TEST_HSID_2).unwrap().into();
        let period = TimePeriod::new(
            humantime::parse_duration("24 hours").unwrap(),
            humantime::parse_rfc3339("2023-02-09T12:00:00Z").unwrap(),
            humantime::parse_duration("12 hours").unwrap(),
        )
        .unwrap();
        assert_eq!(period.interval_num(), TEST_DATA_TIMEPERIOD_2);
        let (blind_id, subcredential) = id.compute_blinded_key(period).unwrap();

        assert_eq!(
            blind_id.as_bytes(),
            &hex!("706628758208395D461AA0F460A5E76E7B828C66B5E794768592B451302E961D")
        );

        assert_eq!(subcredential.as_ref(), &TEST_SUBCREDENTIAL_2);

        HsDesc::parse(TEST_DATA_2, &blind_id.into())
            .unwrap()
            .check_signature()
            .unwrap()
            .check_valid_at(&humantime::parse_rfc3339("2023-02-09T12:00:00Z").unwrap())
            .unwrap()
    }

    #[test]
    fn parse_desc_auth_missing() {
        // If we try to decrypt TEST_DATA_2 with no ClientDescEncKey, we get a
        // failure.
        let encrypted = get_test2_encrypted();
        let subcredential = TEST_SUBCREDENTIAL_2.into();
        let with_no_auth = encrypted.decrypt(&subcredential, None);
        assert!(with_no_auth.is_err());
    }

    #[test]
    fn parse_desc_auth_good() {
        // But if we try to decrypt TEST_DATA_2 with the correct ClientDescEncKey, we get a
        // the data inside!

        let encrypted = get_test2_encrypted();
        let subcredential = TEST_SUBCREDENTIAL_2.into();
        let pk = curve25519::PublicKey::from(TEST_PUBKEY_2).into();
        let sk = curve25519::StaticSecret::from(TEST_SECKEY_2).into();
        let desc = encrypted.decrypt(&subcredential, Some((&pk, &sk))).unwrap();
        let desc = desc
            .check_valid_at(&humantime::parse_rfc3339("2023-01-24T03:00:00Z").unwrap())
            .unwrap();
        let desc = desc.check_signature().unwrap();
        assert_eq!(desc.intro_points.len(), 3);
    }
}