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use std::sync::Arc;
use async_rustls::rustls::{
self, cipher_suite::TLS13_CHACHA20_POLY1305_SHA256, client::ServerCertVerifier,
server::ClientCertVerifier, Certificate, CertificateError, Error::InvalidCertificate,
PrivateKey, SupportedCipherSuite, SupportedKxGroup, SupportedProtocolVersion,
};
use log::error;
use x509_parser::{certificate::X509Certificate, parse_x509_certificate};
use karyons_core::key_pair::{KeyPair, KeyPairType, PublicKey};
use crate::{PeerID, Result};
// NOTE: This code needs a comprehensive audit.
static PROTOCOL_VERSIONS: &[&SupportedProtocolVersion] = &[&rustls::version::TLS13];
static CIPHER_SUITES: &[SupportedCipherSuite] = &[TLS13_CHACHA20_POLY1305_SHA256];
static KX_GROUPS: &[&SupportedKxGroup] = &[&rustls::kx_group::X25519];
const BAD_SIGNATURE_ERR: rustls::Error = InvalidCertificate(CertificateError::BadSignature);
const BAD_ENCODING_ERR: rustls::Error = InvalidCertificate(CertificateError::BadEncoding);
/// Returns a TLS client configuration.
pub fn tls_client_config(
key_pair: &KeyPair,
peer_id: Option<PeerID>,
) -> Result<rustls::ClientConfig> {
let (cert, private_key) = generate_cert(key_pair)?;
let server_verifier = SrvrCertVerifier { peer_id };
let client_config = rustls::ClientConfig::builder()
.with_cipher_suites(CIPHER_SUITES)
.with_kx_groups(KX_GROUPS)
.with_protocol_versions(PROTOCOL_VERSIONS)?
.with_custom_certificate_verifier(Arc::new(server_verifier))
.with_client_auth_cert(vec![cert], private_key)?;
Ok(client_config)
}
/// Returns a TLS server configuration.
pub fn tls_server_config(key_pair: &KeyPair) -> Result<rustls::ServerConfig> {
let (cert, private_key) = generate_cert(key_pair)?;
let client_verifier = CliCertVerifier {};
let server_config = rustls::ServerConfig::builder()
.with_cipher_suites(CIPHER_SUITES)
.with_kx_groups(KX_GROUPS)
.with_protocol_versions(PROTOCOL_VERSIONS)?
.with_client_cert_verifier(Arc::new(client_verifier))
.with_single_cert(vec![cert], private_key)?;
Ok(server_config)
}
/// Generates a certificate and returns both the certificate and the private key.
fn generate_cert(key_pair: &KeyPair) -> Result<(Certificate, PrivateKey)> {
let cert_key_pair = rcgen::KeyPair::generate(&rcgen::PKCS_ED25519)?;
let private_key = rustls::PrivateKey(cert_key_pair.serialize_der());
// Add a custom extension to the certificate:
// - Sign the certificate's public key with the provided key pair's public key
// - Append both the signature and the key pair's public key to the extension
let signature = key_pair.sign(&cert_key_pair.public_key_der());
let ext_content = yasna::encode_der(&(key_pair.public().as_bytes().to_vec(), signature));
// XXX: Not sure about the oid number ???
let mut ext = rcgen::CustomExtension::from_oid_content(&[0, 0, 0, 0], ext_content);
ext.set_criticality(true);
let mut params = rcgen::CertificateParams::new(vec![]);
params.alg = &rcgen::PKCS_ED25519;
params.key_pair = Some(cert_key_pair);
params.custom_extensions.push(ext);
let cert = rustls::Certificate(rcgen::Certificate::from_params(params)?.serialize_der()?);
Ok((cert, private_key))
}
/// Verifies the given certification.
fn verify_cert(end_entity: &Certificate) -> std::result::Result<PeerID, rustls::Error> {
// Parse the certificate.
let cert = parse_cert(end_entity)?;
match cert.extensions().first() {
Some(ext) => {
// Extract the peer id (public key) and the signature from the extension.
let (public_key, signature): (Vec<u8>, Vec<u8>) =
yasna::decode_der(ext.value).map_err(|_| BAD_ENCODING_ERR)?;
// Use the peer id (public key) to verify the extracted signature.
let public_key = PublicKey::from_bytes(&KeyPairType::Ed25519, &public_key)
.map_err(|_| BAD_ENCODING_ERR)?;
public_key
.verify(cert.public_key().raw, &signature)
.map_err(|_| BAD_SIGNATURE_ERR)?;
// Verify the certificate signature.
verify_cert_signature(
&cert,
cert.tbs_certificate.as_ref(),
cert.signature_value.as_ref(),
)?;
PeerID::try_from(public_key).map_err(|_| BAD_ENCODING_ERR)
}
None => Err(BAD_ENCODING_ERR),
}
}
/// Parses the given x509 certificate.
fn parse_cert(end_entity: &Certificate) -> std::result::Result<X509Certificate, rustls::Error> {
let (_, cert) = parse_x509_certificate(end_entity.as_ref()).map_err(|_| BAD_ENCODING_ERR)?;
if !cert.validity().is_valid() {
return Err(InvalidCertificate(CertificateError::NotValidYet));
}
Ok(cert)
}
/// Verifies the signature of the given certificate.
fn verify_cert_signature(
cert: &X509Certificate,
message: &[u8],
signature: &[u8],
) -> std::result::Result<(), rustls::Error> {
let public_key = PublicKey::from_bytes(
&KeyPairType::Ed25519,
cert.tbs_certificate.subject_pki.subject_public_key.as_ref(),
)
.map_err(|_| BAD_ENCODING_ERR)?;
public_key
.verify(message, signature)
.map_err(|_| BAD_SIGNATURE_ERR)
}
struct SrvrCertVerifier {
peer_id: Option<PeerID>,
}
impl ServerCertVerifier for SrvrCertVerifier {
fn verify_server_cert(
&self,
end_entity: &Certificate,
_intermediates: &[Certificate],
_server_name: &rustls::ServerName,
_scts: &mut dyn Iterator<Item = &[u8]>,
_ocsp_response: &[u8],
_now: std::time::SystemTime,
) -> std::result::Result<rustls::client::ServerCertVerified, rustls::Error> {
let peer_id = match verify_cert(end_entity) {
Ok(pid) => pid,
Err(err) => {
error!("Failed to verify cert: {err}");
return Err(err);
}
};
// Verify that the peer id in the certificate's extension matches the
// one the client intends to connect to.
// Both should be equal for establishing a fully secure connection.
if let Some(pid) = &self.peer_id {
if pid != &peer_id {
return Err(InvalidCertificate(
CertificateError::ApplicationVerificationFailure,
));
}
}
Ok(rustls::client::ServerCertVerified::assertion())
}
fn verify_tls13_signature(
&self,
message: &[u8],
cert: &Certificate,
dss: &rustls::DigitallySignedStruct,
) -> std::result::Result<rustls::client::HandshakeSignatureValid, rustls::Error> {
let cert = parse_cert(cert)?;
verify_cert_signature(&cert, message, dss.signature())?;
Ok(rustls::client::HandshakeSignatureValid::assertion())
}
}
struct CliCertVerifier {}
impl ClientCertVerifier for CliCertVerifier {
fn verify_client_cert(
&self,
end_entity: &Certificate,
_intermediates: &[Certificate],
_now: std::time::SystemTime,
) -> std::result::Result<rustls::server::ClientCertVerified, rustls::Error> {
if let Err(err) = verify_cert(end_entity) {
error!("Failed to verify cert: {err}");
return Err(err);
};
Ok(rustls::server::ClientCertVerified::assertion())
}
fn verify_tls13_signature(
&self,
message: &[u8],
cert: &Certificate,
dss: &rustls::DigitallySignedStruct,
) -> std::result::Result<rustls::client::HandshakeSignatureValid, rustls::Error> {
let cert = parse_cert(cert)?;
verify_cert_signature(&cert, message, dss.signature())?;
Ok(rustls::client::HandshakeSignatureValid::assertion())
}
fn client_auth_root_subjects(&self) -> &[rustls::DistinguishedName] {
&[]
}
}
|
