//! Hidden service descriptor encoding.

mod inner;

mod middle;

mod outer;

use crate::NetdocBuilder;

use crate::doc::hsdesc::{IntroAuthType, IntroPointDesc};

use rand::{CryptoRng, Rng};

use tor_bytes::EncodeError;

use tor_cell::chancell::msg::HandshakeType;

use tor_cert::{CertEncodeError, CertType, CertifiedKey, Ed25519Cert, EncodedEd25519Cert};

use tor_error::into_bad_api_usage;

use tor_hscrypto::pk::{HsBlindIdKey, HsBlindIdKeypair, HsSvcDescEncKeypair};

use tor_hscrypto::{RevisionCounter, Subcredential};

use tor_llcrypto::pk::curve25519;

use tor_llcrypto::pk::ed25519;

use tor_units::IntegerMinutes;

use derive_builder::Builder;

use smallvec::SmallVec;

use std::borrow::{Borrow, Cow};

use std::time::SystemTime;

use self::inner::HsDescInner;

use self::middle::HsDescMiddle;

use self::outer::HsDescOuter;

use super::desc_enc::{HS_DESC_ENC_NONCE_LEN, HsDescEncNonce, HsDescEncryption};

use super::pow::PowParams;

/// An intermediary type for encoding hidden service descriptors.

///

/// This object is constructed via [`HsDescBuilder`], and then turned into a

/// signed document using [`HsDescBuilder::build_sign()`].

///

/// TODO: Add an example for using this API.

#[derive(Builder)]

#[builder(public, derive(Debug, Clone), pattern = "owned", build_fn(vis = ""))]

struct HsDesc<'a> {

    /// The blinded hidden service public key used for the first half of the "SECRET_DATA" field.

    ///

    /// (See rend-spec v3 2.5.1.1 and 2.5.2.1.)

    blinded_id: &'a HsBlindIdKey,

    /// The short-term descriptor signing key (KP_hs_desc_sign, KS_hs_desc_sign).

    hs_desc_sign: &'a ed25519::Keypair,

    /// The descriptor signing key certificate.

    ///

    /// This certificate can be created using [`create_desc_sign_key_cert`].

    hs_desc_sign_cert: EncodedEd25519Cert,

    /// A list of recognized CREATE handshakes that this onion service supports.

    create2_formats: &'a [HandshakeType],

    /// 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: &'a [IntroPointDesc],

    /// The expiration time of an introduction point authentication key certificate.

    intro_auth_key_cert_expiry: SystemTime,

    /// The expiration time of an introduction point encryption key certificate.

    intro_enc_key_cert_expiry: SystemTime,

    /// Proof-of-work parameters.

    #[builder(default)]

    #[cfg(feature = "hs-pow-full")]

    pow_params: Option<&'a PowParams>,

    /// The list of clients authorized to discover the hidden service.

    ///

    /// If `None`, restricted discovery is disabled.

    /// If `Some(&[])`, restricted discovery is enabled,

    /// but there will be no authorized clients.

    ///

    /// If restricted discovery is disabled, the resulting middle document will contain a single

    /// `auth-client` line populated with random values.

    ///

    /// Restricted discovery is disabled by default.

    #[builder(default)]

    auth_clients: Option<&'a [curve25519::PublicKey]>,

    /// The lifetime of this descriptor, in minutes.

    ///

    /// This doesn't actually list the starting time or the end time for the

    /// descriptor: presumably, because we didn't want to leak the onion

    /// service's view of the wallclock.

    lifetime: IntegerMinutes<u16>,

    /// A revision counter to tell whether this descriptor is more or less recent

    /// than another one for the same blinded ID.

    revision_counter: RevisionCounter,

    /// The "subcredential" of the onion service.

    subcredential: Subcredential,

    /// Maximum length of generated HsDesc.

    ///

    /// If the generated descriptor is larger than this, `build_sign` will return an error.

    #[builder(field(type = "Option<usize>", build = "()"), setter(strip_option))]

    #[allow(dead_code)]

    max_generated_len: (),

}

/// Restricted discovery parameters.

#[derive(Debug)]

pub(super) struct ClientAuth<'a> {

    /// An ephemeral x25519 keypair generated by the hidden service (`KP_hss_desc_enc`).

    ///

    /// A new keypair MUST be generated every time a descriptor is encoded, or the descriptor

    /// encryption will not be secure.

    ephemeral_key: HsSvcDescEncKeypair,

    /// The list of clients authorized to discover this service.

    auth_clients: &'a [curve25519::PublicKey],

    /// The `N_hs_desc_enc` descriptor_cookie key generated by the hidden service.

    ///

    /// A new descriptor cookie is randomly generated for each descriptor.

    descriptor_cookie: [u8; HS_DESC_ENC_NONCE_LEN],

}

impl<'a> ClientAuth<'a> {

    /// Create a new `ClientAuth` using the specified authorized clients.

    ///

    /// If `auth_clients` is empty list, there will be no authorized clients.

    ///

    /// This returns `None` if the list of `auth_clients` is `None`.

            // Restricted discovery is disabled

        };

        // Generate a new `N_hs_desc_enc` descriptor_cookie key for this descriptor.

}

impl<'a> NetdocBuilder for HsDescBuilder<'a> {

        /// The superencrypted field must be padded to the nearest multiple of 10k bytes

        ///

        /// rend-spec-v3 2.5.1.1

        const SUPERENCRYPTED_ALIGN: usize = 10 * (1 << 10);

        // Construct the inner (second layer) plaintext. This is the unencrypted value of the

        // "encrypted" field.

        // Encrypt the inner document. The encrypted blob is the ciphertext contained in the

        // "encrypted" field described in section 2.5.1.2. of rend-spec-v3.

        );

        // Construct the middle (first player) plaintext. This is the unencrypted value of the

        // "superencrypted" field.

        // Section 2.5.1.1. of rend-spec-v3: before encryption, pad the plaintext to the nearest

        // multiple of 10k bytes

        // Encrypt the middle document. The encrypted blob is the ciphertext contained in the

        // "superencrypted" field described in section 2.5.1.1. of rend-spec-v3.

            // desc_enc_nonce is absent when handling the superencryption layer (2.5.1.1).

        );

        // Finally, build the hidden service descriptor.

}

/// Create the descriptor signing key certificate.

///

/// Returns the encoded representation of the certificate

/// obtained by signing the descriptor signing key `hs_desc_sign`

/// with the blinded id key `blind_id`.

///

/// This certificate is meant to be passed to [`HsDescBuilder::hs_desc_sign_cert`].

    // "The certificate cross-certifies the short-term descriptor signing key with the blinded

    // public key.  The certificate type must be [08], and the blinded public key must be

    // present as the signing-key extension."

impl<'a> HsDesc<'a> {

    /// Encrypt the specified plaintext using the algorithm described in section

    /// `[HS-DESC-ENCRYPTION-KEYS]` of rend-spec-v3.txt.

}

/// Pad `v` with zeroes to the next multiple of `alignment`.

    } else {

        // No need to pad.

    }

#[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::mixed_attributes_style)]

    #![allow(clippy::print_stderr)]

    #![allow(clippy::print_stdout)]

    #![allow(clippy::single_char_pattern)]

    #![allow(clippy::unwrap_used)]

    #![allow(clippy::unchecked_time_subtraction)]

    #![allow(clippy::useless_vec)]

    #![allow(clippy::needless_pass_by_value)]

    //! <!-- @@ end test lint list maintained by maint/add_warning @@ -->

    use std::net::Ipv4Addr;

    use std::time::Duration;

    use super::*;

    use crate::doc::hsdesc::{EncryptedHsDesc, HsDesc as ParsedHsDesc};

    use tor_basic_utils::test_rng::Config;

    use tor_checkable::{SelfSigned, Timebound};

    use tor_hscrypto::pk::{HsClientDescEncKeypair, HsIdKeypair};

    use tor_hscrypto::time::TimePeriod;

    use tor_linkspec::LinkSpec;

    use tor_llcrypto::pk::{curve25519, ed25519::ExpandedKeypair};

    use web_time_compat::SystemTimeExt;

    // TODO: move the test helpers to a separate module and make them more broadly available if

    // necessary.

    /// Expect `err` to be a `Bug`, and return its string representation.

    ///

    /// # Panics

    ///

    /// Panics if `err` is not a `Bug`.

    pub(super) fn expect_bug(err: EncodeError) -> String {

        match err {

            EncodeError::Bug(b) => b.to_string(),

            EncodeError::BadLengthValue => panic!("expected Bug, got BadLengthValue"),

            _ => panic!("expected Bug, got unknown error"),

        }

    }

    pub(super) fn create_intro_point_descriptor<R: Rng + CryptoRng>(

        rng: &mut R,

        link_specifiers: &[LinkSpec],

    ) -> IntroPointDesc {

        let link_specifiers = link_specifiers

            .iter()

            .map(|link_spec| link_spec.encode())

            .collect::<Result<Vec<_>, _>>()

            .unwrap();

        IntroPointDesc {

            link_specifiers,

            ipt_ntor_key: create_curve25519_pk(rng),

            ipt_sid_key: ed25519::Keypair::generate(rng).verifying_key().into(),

            svc_ntor_key: create_curve25519_pk(rng).into(),

        }

    }

    /// Create a new curve25519 public key.

    pub(super) fn create_curve25519_pk<R: Rng + CryptoRng>(rng: &mut R) -> curve25519::PublicKey {

        let ephemeral_key = curve25519::EphemeralSecret::random_from_rng(rng);

        (&ephemeral_key).into()

    }

    /// Parse the specified hidden service descriptor.

    fn parse_hsdesc(

        unparsed_desc: &str,

        blinded_pk: ed25519::PublicKey,

        subcredential: &Subcredential,

        hsc_desc_enc: Option<&HsClientDescEncKeypair>,

    ) -> ParsedHsDesc {

        const TIMESTAMP: &str = "2023-01-23T15:00:00Z";

        let id = ed25519::Ed25519Identity::from(blinded_pk);

        let enc_desc: EncryptedHsDesc = ParsedHsDesc::parse(unparsed_desc, &id.into())

            .unwrap()

            .check_signature()

            .unwrap()

            .check_valid_at(&humantime::parse_rfc3339(TIMESTAMP).unwrap())

            .unwrap();

        enc_desc

            .decrypt(subcredential, hsc_desc_enc)

            .unwrap()

            .check_valid_at(&humantime::parse_rfc3339(TIMESTAMP).unwrap())

            .unwrap()

            .check_signature()

            .unwrap()

    }

    #[test]

    fn encode_decode() {

        const CREATE2_FORMATS: &[HandshakeType] = &[HandshakeType::TAP, HandshakeType::NTOR];

        const LIFETIME_MINS: u16 = 100;

        const REVISION_COUNT: u64 = 2;

        const CERT_EXPIRY_SECS: u64 = 60 * 60;

        let mut rng = Config::Deterministic.into_rng();

        // The identity keypair of the hidden service.

        let hs_id = ed25519::Keypair::generate(&mut rng);

        let hs_desc_sign = ed25519::Keypair::generate(&mut rng);

        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();

        let (_, blinded_id, subcredential) = HsIdKeypair::from(ExpandedKeypair::from(&hs_id))

            .compute_blinded_key(period)

            .unwrap();

        let expiry = SystemTime::get() + Duration::from_secs(CERT_EXPIRY_SECS);

        let mut rng = Config::Deterministic.into_rng();

        let intro_points = vec![IntroPointDesc {

            link_specifiers: vec![

                LinkSpec::OrPort(Ipv4Addr::LOCALHOST.into(), 9999)

                    .encode()

                    .unwrap(),

            ],

            ipt_ntor_key: create_curve25519_pk(&mut rng),

            ipt_sid_key: ed25519::Keypair::generate(&mut rng).verifying_key().into(),

            svc_ntor_key: create_curve25519_pk(&mut rng).into(),

        }];

        let hs_desc_sign_cert =

            create_desc_sign_key_cert(&hs_desc_sign.verifying_key(), &blinded_id, expiry).unwrap();

        let blinded_pk = (&blinded_id).into();

        let builder = HsDescBuilder::default()

            .blinded_id(&blinded_pk)

            .hs_desc_sign(&hs_desc_sign)

            .hs_desc_sign_cert(hs_desc_sign_cert)

            .create2_formats(CREATE2_FORMATS)

            .auth_required(None)

            .is_single_onion_service(true)

            .intro_points(&intro_points)

            .intro_auth_key_cert_expiry(expiry)

            .intro_enc_key_cert_expiry(expiry)

            .lifetime(LIFETIME_MINS.into())

            .revision_counter(REVISION_COUNT.into())

            .subcredential(subcredential);

        // Build and encode a new descriptor (cloning `builder` because it's needed later, when we

        // test if restricted discovery works):

        let encoded_desc = builder

            .clone()

            .build_sign(&mut Config::Deterministic.into_rng())

            .unwrap();

        // Now decode it...

        let desc = parse_hsdesc(

            encoded_desc.as_str(),

            *blinded_id.as_ref().public(),

            &subcredential,

            None, /* No restricted discovery */

        );

        let hs_desc_sign_cert =

            create_desc_sign_key_cert(&hs_desc_sign.verifying_key(), &blinded_id, expiry).unwrap();

        // ...and build a new descriptor using the information from the parsed descriptor,

        // asserting that the resulting descriptor is identical to the original.

        let reencoded_desc = HsDescBuilder::default()

            .blinded_id(&(&blinded_id).into())

            .hs_desc_sign(&hs_desc_sign)

            .hs_desc_sign_cert(hs_desc_sign_cert)

            // create2_formats is hard-coded rather than extracted from desc, because

            // create2_formats is ignored while parsing

            .create2_formats(CREATE2_FORMATS)

            .auth_required(None)

            .is_single_onion_service(desc.is_single_onion_service)

            .intro_points(&intro_points)

            .intro_auth_key_cert_expiry(expiry)

            .intro_enc_key_cert_expiry(expiry)

            .lifetime(desc.idx_info.lifetime)

            .revision_counter(desc.idx_info.revision)

            .subcredential(subcredential)

            .build_sign(&mut Config::Deterministic.into_rng())

            .unwrap();

        assert_eq!(&*encoded_desc, &*reencoded_desc);

        // The same test, this time with restricted discovery enabled

        // (with a single authorized client):

        let client_kp: HsClientDescEncKeypair = HsClientDescEncKeypair::generate(&mut rng);

        let client_pkey = client_kp.public().as_ref();

        let auth_clients = vec![*client_pkey];

        let encoded_desc = builder

            .auth_clients(Some(&auth_clients[..]))

            .build_sign(&mut Config::Deterministic.into_rng())

            .unwrap();

        // Now decode it...

        let desc = parse_hsdesc(

            encoded_desc.as_str(),

            *blinded_id.as_ref().public(),

            &subcredential,

            Some(&client_kp), /* With restricted discovery */

        );

        let hs_desc_sign_cert =

            create_desc_sign_key_cert(&hs_desc_sign.verifying_key(), &blinded_id, expiry).unwrap();

        // ...and build a new descriptor using the information from the parsed descriptor,

        // asserting that the resulting descriptor is identical to the original.

        let reencoded_desc = HsDescBuilder::default()

            .blinded_id(&(&blinded_id).into())

            .hs_desc_sign(&hs_desc_sign)

            .hs_desc_sign_cert(hs_desc_sign_cert)

            // create2_formats is hard-coded rather than extracted from desc, because

            // create2_formats is ignored while parsing

            .create2_formats(CREATE2_FORMATS)

            .auth_required(None)

            .is_single_onion_service(desc.is_single_onion_service)

            .intro_points(&intro_points)

            .intro_auth_key_cert_expiry(expiry)

            .intro_enc_key_cert_expiry(expiry)

            .auth_clients(Some(&auth_clients))

            .lifetime(desc.idx_info.lifetime)

            .revision_counter(desc.idx_info.revision)

            .subcredential(subcredential)

            .build_sign(&mut Config::Deterministic.into_rng())

            .unwrap();

        assert_eq!(&*encoded_desc, &*reencoded_desc);

    }

}