Add rustls-mbedpki-provider crate (#1)

* Create ci.yml

* Add rustls-mbedpki-provider crate

* Formatting changes

* Check for mbedpki-provider warnings in ci.yml

* Implement signature verification methods of `ClientCertVerifier` and `ServerSertVerifier`

* Address review comments

* Add doc comments to public items

---------

Co-authored-by: Arash Sahebolamri <[email protected]>

.github/workflows/ci.yml

@@ -0,0 +1,28 @@
+name: Rust
+
+on:
+  push:
+    branches: [ "master" ]
+  pull_request:
+    branches: [ "master" ]
+
+env:
+  CARGO_TERM_COLOR: always
+
+jobs:
+  build:
+
+    runs-on: ubuntu-latest
+
+    steps:
+    - uses: actions/checkout@v3
+
+    - name: check mbedpki-provider
+      working-directory: rustls-mbedpki-provider
+      env:
+        RUSTFLAGS: -D warnings
+      run: cargo check
+
+    - name: Run mbedpki-provider tests
+      working-directory: rustls-mbedpki-provider
+      run: cargo test

.rustfmt.toml

@@ -0,0 +1,3 @@
+chain_width=40
+max_width = 128
+struct_lit_width = 80

README.md

@@ -1,5 +1,11 @@
 # rustls-mbedtls-provider
 
+This repository will contain code to allow [mbedtls](https://github.com/fortanix/rust-mbedtls) to be used
+as the crypto and PKI provider for [rustls](https://github.com/rustls/rustls).
+
+## PKI provider
+Implements [`ClientCertVerifier`](https://docs.rs/rustls/latest/rustls/server/trait.ClientCertVerifier.html) and [`ClientCertVerifier`](https://docs.rs/rustls/latest/rustls/client/trait.ServerCertVerifier.html) traits from `rustls` using mbedtls.
+
 
 # Contributing
 

rustls-mbedpki-provider/Cargo.toml

@@ -0,0 +1,16 @@
+[package]
+name = "rustls-mbedpki-provider"
+version = "0.1.0"
+edition = "2021"
+description = "Implements rustls PKI traits using mbedtls"
+# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
+
+[dependencies]
+rustls = {version = "0.21", features = ["dangerous_configuration"]}
+mbedtls = {version = "0.12.0-alpha.1", features = ["x509", "chrono", "std"], default_features = false}
+
+x509-parser = "0.15"
+chrono = "0.4"
+
+[dev-dependencies]
+rustls-pemfile = "1.0"

rustls-mbedpki-provider/src/client_cert_verifier.rs

@@ -0,0 +1,244 @@
+use std::time::SystemTime;
+
+use rustls::{
+    server::{ClientCertVerified, ClientCertVerifier},
+    DistinguishedName,
+};
+
+use crate::{
+    mbedtls_err_into_rustls_err, mbedtls_err_into_rustls_err_with_error_msg, rustls_cert_to_mbedtls_cert,
+    verify_certificates_active, verify_tls_signature,
+};
+
+/// A `rustls` `ClientCertVerifier` implemented using the PKI functionality of
+/// `mbedtls`
+#[derive(Clone)]
+pub struct MbedTlsClientCertVerifier {
+    trusted_cas: mbedtls::alloc::List<mbedtls::x509::Certificate>,
+    root_subjects: Vec<rustls::DistinguishedName>,
+}
+
+impl MbedTlsClientCertVerifier {
+    /// Constructs a new `MbedTlsClientCertVerifier` object given the provided trusted certificate authority
+    /// certificates.
+    ///
+    /// Returns an error if any of the certificates are invalid.
+    pub fn new<'a>(trusted_cas: impl IntoIterator<Item = &'a rustls::Certificate>) -> mbedtls::Result<Self> {
+        let trusted_cas = trusted_cas
+            .into_iter()
+            .map(rustls_cert_to_mbedtls_cert)
+            .collect::<mbedtls::Result<Vec<_>>>()?
+            .into_iter()
+            .collect();
+        Self::new_from_mbedtls_trusted_cas(trusted_cas)
+    }
+
+    /// Constructs a new `MbedTlsClientCertVerifier` object given the provided trusted certificate authority
+    /// certificates.
+    pub fn new_from_mbedtls_trusted_cas(
+        trusted_cas: mbedtls::alloc::List<mbedtls::x509::Certificate>,
+    ) -> mbedtls::Result<Self> {
+        let mut root_subjects = vec![];
+        for ca in trusted_cas.iter() {
+            root_subjects.push(DistinguishedName::from(ca.subject_raw()?));
+        }
+        Ok(Self { trusted_cas, root_subjects })
+    }
+
+    /// The certificate authority certificates used to construct this object
+    pub fn trusted_cas(&self) -> &mbedtls::alloc::List<mbedtls::x509::Certificate> {
+        &self.trusted_cas
+    }
+
+    /// the Subjects of the client authentication trust anchors to share with the client when
+    /// requesting client authentication, extractd from CA certificates.
+    pub fn root_subjects(&self) -> &[DistinguishedName] {
+        self.root_subjects.as_ref()
+    }
+}
+
+impl ClientCertVerifier for MbedTlsClientCertVerifier {
+    fn client_auth_root_subjects(&self) -> &[DistinguishedName] {
+        &self.root_subjects
+    }
+
+    fn verify_client_cert(
+        &self,
+        end_entity: &rustls::Certificate,
+        intermediates: &[rustls::Certificate],
+        now: SystemTime,
+    ) -> Result<rustls::server::ClientCertVerified, rustls::Error> {
+        let now = chrono::DateTime::<chrono::Local>::from(now).naive_local();
+
+        let chain: mbedtls::alloc::List<_> = [end_entity]
+            .into_iter()
+            .chain(intermediates)
+            .map(rustls_cert_to_mbedtls_cert)
+            .collect::<mbedtls::Result<Vec<_>>>()
+            .map_err(mbedtls_err_into_rustls_err)?
+            .into_iter()
+            .collect();
+
+        verify_certificates_active(chain.iter().map(|c| &**c), now)?;
+
+        let mut error_msg = String::default();
+        mbedtls::x509::Certificate::verify(&chain, &self.trusted_cas, None, Some(&mut error_msg))
+            .map_err(|e| mbedtls_err_into_rustls_err_with_error_msg(e, &error_msg))?;
+
+        Ok(ClientCertVerified::assertion())
+    }
+
+    fn verify_tls12_signature(
+        &self,
+        message: &[u8],
+        cert: &rustls::Certificate,
+        dss: &rustls::DigitallySignedStruct,
+    ) -> Result<rustls::client::HandshakeSignatureValid, rustls::Error> {
+        verify_tls_signature(message, cert, dss, false)
+    }
+
+    fn verify_tls13_signature(
+        &self,
+        message: &[u8],
+        cert: &rustls::Certificate,
+        dss: &rustls::DigitallySignedStruct,
+    ) -> Result<rustls::client::HandshakeSignatureValid, rustls::Error> {
+        verify_tls_signature(message, cert, dss, true)
+    }
+}
+
+// ../test-data/rsa/client.fullchain has these three certificates:
+// cert subject: CN=ponytown client, cert issuer: CN=ponytown RSA level 2 intermediate
+// cert subject: CN=ponytown RSA level 2 intermediate, cert issuer: CN=ponytown RSA CA
+// cert subject: CN=ponytown RSA CA, cert issuer: CN=ponytown RSA CA
+#[cfg(test)]
+mod tests {
+
+    use chrono::DateTime;
+    use rustls::{
+        server::ClientCertVerifier, Certificate, ClientConfig, ClientConnection, RootCertStore, ServerConfig, ServerConnection,
+    };
+    use std::{sync::Arc, time::SystemTime};
+
+    use super::MbedTlsClientCertVerifier;
+    use crate::tests_common::{do_handshake_until_error, get_chain, get_key};
+
+    fn server_config_with_verifier(client_cert_verifier: MbedTlsClientCertVerifier) -> ServerConfig {
+        ServerConfig::builder()
+            .with_safe_defaults()
+            .with_client_cert_verifier(Arc::new(client_cert_verifier))
+            .with_single_cert(
+                get_chain(include_bytes!("../test-data/rsa/end.fullchain")),
+                get_key(include_bytes!("../test-data/rsa/end.key")),
+            )
+            .unwrap()
+    }
+
+    #[test]
+    fn connection_client_cert_verifier() {
+        let client_config = ClientConfig::builder().with_safe_defaults();
+        let root_ca = Certificate(include_bytes!("../test-data/rsa/ca.der").to_vec());
+        let mut root_store = RootCertStore::empty();
+        root_store.add(&root_ca).unwrap();
+        let cert_chain = get_chain(include_bytes!("../test-data/rsa/client.fullchain"));
+
+        let client_config = client_config
+            .with_root_certificates(root_store)
+            .with_client_auth_cert(cert_chain, get_key(include_bytes!("../test-data/rsa/client.key")))
+            .unwrap();
+
+        let client_cert_verifier = MbedTlsClientCertVerifier::new([&root_ca]).unwrap();
+
+        let server_config = server_config_with_verifier(client_cert_verifier);
+
+        let mut client_conn = ClientConnection::new(Arc::new(client_config), "localhost".try_into().unwrap()).unwrap();
+        let mut server_conn = ServerConnection::new(Arc::new(server_config)).unwrap();
+
+        assert!(do_handshake_until_error(&mut client_conn, &mut server_conn).is_ok());
+    }
+
+    fn test_connection_client_cert_verifier_with_invalid_certs(invalid_cert_chain: Vec<Certificate>) {
+        let client_config = ClientConfig::builder().with_safe_defaults();
+        let root_ca = Certificate(include_bytes!("../test-data/rsa/ca.der").to_vec());
+        let mut root_store = RootCertStore::empty();
+        root_store.add(&root_ca).unwrap();
+
+        let client_config = client_config
+            .with_root_certificates(root_store)
+            .with_client_auth_cert(invalid_cert_chain, get_key(include_bytes!("../test-data/rsa/client.key")))
+            .unwrap();
+
+        let client_cert_verifier = MbedTlsClientCertVerifier::new([&root_ca]).unwrap();
+
+        let server_config = server_config_with_verifier(client_cert_verifier);
+
+        let mut client_conn = ClientConnection::new(Arc::new(client_config), "localhost".try_into().unwrap()).unwrap();
+        let mut server_conn = ServerConnection::new(Arc::new(server_config)).unwrap();
+
+        let res = do_handshake_until_error(&mut client_conn, &mut server_conn);
+        assert!(matches!(res, Err(rustls::Error::InvalidCertificate(_))));
+    }
+
+    #[test]
+    fn connection_client_cert_verifier_with_invalid_certs() {
+        let cert_chain = get_chain(include_bytes!("../test-data/rsa/client.fullchain"));
+
+        let mut invalid_chain1 = cert_chain.clone();
+        invalid_chain1.remove(1);
+
+        let mut invalid_chain2 = cert_chain.clone();
+        invalid_chain2.remove(0);
+
+        let mut invalid_chain3 = cert_chain.clone();
+        invalid_chain3.swap(0, 1);
+
+        for invalid_chain in [invalid_chain1, invalid_chain2, invalid_chain3] {
+            test_connection_client_cert_verifier_with_invalid_certs(invalid_chain);
+        }
+    }
+
+    #[test]
+    fn client_cert_verifier_valid_chain() {
+        let cert_chain = get_chain(include_bytes!("../test-data/rsa/client.fullchain"));
+        let trusted_cas = [Certificate(include_bytes!("../test-data/rsa/ca.der").to_vec())];
+
+        let verifier = MbedTlsClientCertVerifier::new(trusted_cas.iter()).unwrap();
+
+        let now = SystemTime::from(chrono::DateTime::parse_from_rfc3339("2023-11-26T12:00:00+00:00").unwrap());
+
+        assert!(verifier
+            .verify_client_cert(&cert_chain[0], &cert_chain[1..], now)
+            .is_ok());
+    }
+
+    #[test]
+    fn client_cert_verifier_broken_chain() {
+        let mut cert_chain = get_chain(include_bytes!("../test-data/rsa/client.fullchain"));
+        cert_chain.remove(1);
+        let trusted_cas = [Certificate(include_bytes!("../test-data/rsa/ca.der").to_vec())];
+
+        let verifier = MbedTlsClientCertVerifier::new(trusted_cas.iter()).unwrap();
+
+        let now = SystemTime::from(DateTime::parse_from_rfc3339("2023-11-26T12:00:00+00:00").unwrap());
+
+        let verify_res = verifier.verify_client_cert(&cert_chain[0], &cert_chain[1..], now);
+        assert!(matches!(verify_res, Err(rustls::Error::InvalidCertificate(_))));
+    }
+
+    #[test]
+    fn client_cert_verifier_expired_certs() {
+        let cert_chain = get_chain(include_bytes!("../test-data/rsa/client.fullchain"));
+        let trusted_cas = [Certificate(include_bytes!("../test-data/rsa/ca.der").to_vec())];
+
+        let verifier = MbedTlsClientCertVerifier::new(trusted_cas.iter()).unwrap();
+
+        let now = SystemTime::from(DateTime::parse_from_rfc3339("2052-11-26T12:00:00+00:00").unwrap());
+
+        assert_eq!(
+            verifier
+                .verify_client_cert(&cert_chain[0], &cert_chain[1..], now)
+                .unwrap_err(),
+            rustls::Error::InvalidCertificate(rustls::CertificateError::Expired)
+        );
+    }
+}