#![cfg_attr(docsrs, feature(doc_cfg))]

#![doc = include_str!("../README.md")]

// @@ begin lint list maintained by maint/add_warning @@

#![allow(renamed_and_removed_lints)] // @@REMOVE_WHEN(ci_arti_stable)

#![allow(unknown_lints)] // @@REMOVE_WHEN(ci_arti_nightly)

#![warn(missing_docs)]

#![warn(noop_method_call)]

#![warn(unreachable_pub)]

#![warn(clippy::all)]

#![deny(clippy::await_holding_lock)]

#![deny(clippy::cargo_common_metadata)]

#![deny(clippy::cast_lossless)]

#![deny(clippy::checked_conversions)]

#![allow(clippy::cognitive_complexity)] // See arti#2556

#![deny(clippy::debug_assert_with_mut_call)]

#![deny(clippy::exhaustive_enums)]

#![deny(clippy::exhaustive_structs)]

#![deny(clippy::expl_impl_clone_on_copy)]

#![deny(clippy::fallible_impl_from)]

#![deny(clippy::implicit_clone)]

#![deny(clippy::large_stack_arrays)]

#![warn(clippy::manual_ok_or)]

#![deny(clippy::missing_docs_in_private_items)]

#![warn(clippy::needless_borrow)]

#![warn(clippy::needless_pass_by_value)]

#![warn(clippy::option_option)]

#![deny(clippy::print_stderr)]

#![deny(clippy::print_stdout)]

#![warn(clippy::rc_buffer)]

#![deny(clippy::ref_option_ref)]

#![warn(clippy::semicolon_if_nothing_returned)]

#![warn(clippy::trait_duplication_in_bounds)]

#![deny(clippy::unchecked_time_subtraction)]

#![deny(clippy::unnecessary_wraps)]

#![warn(clippy::unseparated_literal_suffix)]

#![deny(clippy::unwrap_used)]

#![deny(clippy::mod_module_files)]

#![allow(clippy::let_unit_value)] // This can reasonably be done for explicitness

#![allow(clippy::uninlined_format_args)]

#![allow(clippy::significant_drop_in_scrutinee)] // arti/-/merge_requests/588/#note_2812945

#![allow(clippy::result_large_err)] // temporary workaround for arti#587

#![allow(clippy::needless_raw_string_hashes)] // complained-about code is fine, often best

#![allow(clippy::needless_lifetimes)] // See arti#1765

#![allow(mismatched_lifetime_syntaxes)] // temporary workaround for arti#2060

#![allow(clippy::collapsible_if)] // See arti#2342

#![deny(clippy::unused_async)]

#![deny(clippy::string_slice)] // See arti#2571

#![allow(recursion_depth_exceeding_limit)] // arti#2715, rust/issues/159228

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

// This module uses the `x509-cert` crate to generate certificates;

// if we decide to switch, `rcgen` and `x509-certificate`

// seem like the likeliest options.

use std::{

    sync::Arc,

    time::{Duration, SystemTime},

};

use digest::Digest;

use rand::CryptoRng;

use rsa::pkcs8::{EncodePrivateKey as _, SubjectPublicKeyInfo};

use tor_error::into_internal;

use tor_llcrypto::{pk::rsa::KeyPair as RsaKeypair, util::rng::RngCompat};

use x509_cert::{

    builder::{Builder, CertificateBuilder, Profile},

    der::{DateTime, Encode, asn1::GeneralizedTime, zeroize::Zeroizing},

    ext::pkix::{KeyUsage, KeyUsages},

    serial_number::SerialNumber,

    time::Validity,

};

/// Legacy identity keys are required to have this length.

const EXPECT_ID_BITS: usize = 1024;

/// Legacy identity keys are required to have this exponent.

const EXPECT_ID_EXPONENT: u32 = 65537;

/// Lifetime of generated id certs, in days.

const ID_CERT_LIFETIME_DAYS: u32 = 365;

/// Create an X.509 certificate, for use in a CERTS cell,

/// self-certifying the provided RSA identity key.

///

/// The resulting certificate will be encoded in DER.

/// Its cert_type field should be 02 when it is sent in a CERTS cell.

///

/// The resulting certificate is quite minimal, and has no unnecessary extensions.

///

/// Returns an error on failure, or if `keypair` is not a 1024-bit RSA key

/// with exponent of 65537.

    use rsa::pkcs1v15::SigningKey;

    use tor_llcrypto::d::Sha256;

    // NOTE: This is how C Tor builds its DNs, but that doesn't mean it's a good idea.

    // We do not, strictly speaking, need this extension: Tor doesn't care that it's there.

    // We do, however, need _some_ extension, or else we'll generate a v1 certificate,

    // which we don't want to do.

/// A set of x.509 certificate information and keys for use with a TLS library.

///

/// Only relays need this: They should set these as the certificate(s) to be used

/// for incoming TLS connections.

///

/// This is not necessarily the most convenient form to manipulate certificates in:

/// rather, it is intended to provide the formats that TLS libraries generally

/// expect to get.

#[derive(Clone, Debug)]

#[non_exhaustive]

pub struct TlsKeyAndCert {

    /// A list of certificates in DER form.

    ///

    /// (This may contain more than one certificate, but for now only one certificate is used.)

    certificates: Vec<Vec<u8>>,

    /// A private key for use in the TLS handshake.

    //

    // Disabled:

    // private_key: ecdsa::SigningKey<p256::NistP256>,

    private_key: rsa::RsaPrivateKey,

    /// A SHA256 digest of the link certificate

    /// (the one certifying the private key's public component).

    ///

    /// This digest is the one what will be certified by the relay's

    /// `SIGNING_V_TLS_CERT`

    /// certificate.

    sha256_digest: [u8; 32],

    /// A time after which this set of link information won't be valid,

    /// and another should be generated.

    expiration: SystemTime,

}

/// What lifetime do we pick for a TLS certificate, in days?

const TLS_CERT_LIFETIME_DAYS: u32 = 30;

impl TlsKeyAndCert {

    /// Return the certificates as a list of DER-encoded values.

    /// Return the certificates as a concatenated list in PEM ("BEGIN CERTIFICATE") format.

    /// Return the private key in (unencrypted) PKCS8 DER format.

    /// Return the private key in (unencrypted) PKCS8 PEM ("BEGIN PRIVATE KEY") format.

    /// Return the earliest time at which any of these certificates will expire.

    /// Return the SHA256 digest of the link certificate

    ///

    /// This digest is the one certified with the relay's

    /// `SIGNING_V_TLS_CERT`

    /// certificate.

    /// Create a new TLS link key and associated certificate(s).

    ///

    /// The certificate will be valid at `now`, and for a while after.

    ///

    /// The certificate parameters and keys are chosen for reasonable security,

    /// approximate conformance to RFC5280, and limited fingerprinting resistance.

    ///

    /// Note: The fingerprinting resistance is quite limited.

    /// We will likely want to pursue these avenues for better fingerprinting resistance:

    ///

    /// - Encourage more use of TLS 1.3, where server certificates are encrypted.

    ///   (This prevents passive fingerprinting only.)

    /// - Adjust this function to make certificates look even more normal

    /// - Integrate with ACME-supporting certificate issuers (Letsencrypt, etc)

    ///   to get real certificates for Tor relays.

        // We would prefer to use p256 here, since it is the most commonly used elliptic curve

        // group for X.509 web certificate signing, as of this writing.

        //

        // We want to use an elliptic curve here for its higher security/performance ratio than RSA,

        // and for its _much_ faster key generation time.

        //

        // But unfortunately, we can't: C tor has a bug where if the subject key is not RSA,

        // the connection will be closed with an error:

        // <https://gitlab.torproject.org/tpo/core/tor/-/issues/41226>.

        // If this bug is fixed, then we will have to wait until all clients and servers upgrade

        // before we can send p256 subject keys instead.

        //

        // DISABLED:

        // let private_key = rsa::RsaPrivateKey::p256::ecdsa::SigningKey::random(&mut RngCompat::new(&mut *rng));

        // let public_key = p256::ecdsa::VerifyingKey::from(&private_key);

        const RSA_KEY_BITS: usize = 2048;

        // Note that we'll discard this key after signing the certificate with it:

        // The real certification for private_key is done in the SIGNING_V_TLS_CERT

        // certificate.

        // NOTE: This is how C Tor builds its DNs, but that doesn't mean it's a good idea.

}

/// Return a Validity that includes `now`, and lasts for `lifetime_days` additionally.

///

/// Additionally, return the time at which the certificate expires.

///

/// We ensure that our cert is valid at least a day into the past.

///

/// We obfuscate our current time a little by rounding to the nearest midnight UTC.

    const ONE_DAY: Duration = Duration::new(86400, 0);

    };

/// Return a random serial number for use in a new certificate.

    const SER_NUMBER_LEN: usize = 16;

/// An error that has occurred while trying to create a certificate.

#[derive(Clone, Debug, thiserror::Error)]

#[non_exhaustive]

pub enum X509CertError {

    /// We received a signing key that we can't use.

    #[error("Provided signing key not valid: {0}")]

    InvalidSigningKey(String),

    /// We received a subject key that we can't use.

    #[error("Couldn't use provided key as a subject")]

    SubjectKeyError(#[from] x509_cert::spki::Error),

    /// We received a hostname that we couldn't use:

    /// probably, it contained an equals sign or a comma.

    #[error("Unable to set hostname when creating certificate")]

    InvalidHostname(#[source] x509_cert::der::Error),

    /// We couldn't construct the certificate.

    #[error("Unable to build certificate")]

    CouldNotBuild(#[source] Arc<x509_cert::builder::Error>),

    /// We constructed the certificate, but couldn't encode it as DER.

    #[error("Unable to encode certificate")]

    CouldNotEncode(#[source] x509_cert::der::Error),

    /// We constructed a key but couldn't format it as PKCS8.

    #[error("Unable to format key as PKCS8")]

    CouldNotFormatPkcs8(#[source] p256::pkcs8::Error),

    /// We've encountered some kind of a bug.

    #[error("Internal error while creating certificate")]

    Bug(#[from] tor_error::Bug),

}

impl From<x509_cert::builder::Error> for X509CertError {

}

#[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)]

    #![allow(clippy::string_slice)] // See arti#2571

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

    use super::*;

    use tor_basic_utils::test_rng::testing_rng;

    use web_time_compat::SystemTimeExt;

    #[test]

    fn identity_cert_generation() {

        let mut rng = testing_rng();

        let keypair = RsaKeypair::generate(&mut rng).unwrap();

        let cert = create_legacy_rsa_id_cert(

            &mut rng,

            SystemTime::get(),

            "www.house-of-pancakes.example.com",

            &keypair,

        )

        .unwrap();

        let key_extracted = tor_llcrypto::util::x509_extract_rsa_subject_kludge(&cert[..]).unwrap();

        assert_eq!(key_extracted, keypair.to_public_key());

        // TODO: It would be neat to validate this certificate with an independent x509 implementation,

        // but afaict most of them sensibly refuse to handle RSA1024.

        //

        // I've checked the above-generated cert using `openssl verify`, but that's it.

    }

    #[test]

    fn identity_cert_generation_size_check() {

        let mut rng = testing_rng();

        let keypair = rsa::RsaPrivateKey::new(&mut RngCompat::new(&mut rng), 2048).unwrap();

        let keypair: RsaKeypair = keypair.into();

        // This fails since it's not 1024 bits.

        assert!(

            create_legacy_rsa_id_cert(

                &mut rng,

                SystemTime::get(),

                "www.house-of-pancakes.example.com",

                &keypair,

            )

            .unwrap_err()

            .to_string()

            .contains("Invalid key length")

        );

    }

    #[test]

    fn tls_cert_info() {

        let mut rng = testing_rng();

        let certified = TlsKeyAndCert::create(

            &mut rng,

            SystemTime::get(),

            "foo.example.com",

            "bar.example.com",

        )

        .unwrap();

        dbg!(certified);

    }

}