From 183c652b0576b55f8cc602206180d8d19308ae15 Mon Sep 17 00:00:00 2001
From: Roman Proskuryakov <r.proskuryakoff@gmail.com>
Date: Fri, 16 Jul 2021 18:41:07 +0300
Subject: [PATCH] More docs

---
 transports/tls-quic/src/verifier.rs | 35 ++++++++++++++++++++---------
 1 file changed, 24 insertions(+), 11 deletions(-)

diff --git a/transports/tls-quic/src/verifier.rs b/transports/tls-quic/src/verifier.rs
index 0dacc506cb75..c91a071e0bc5 100644
--- a/transports/tls-quic/src/verifier.rs
+++ b/transports/tls-quic/src/verifier.rs
@@ -20,9 +20,9 @@
 
 use rustls::{
     internal::msgs::handshake::DigitallySignedStruct,
-    internal::msgs::enums::SignatureScheme,
-    Certificate, ClientCertVerified,
-    HandshakeSignatureValid, ServerCertVerified, TLSError,
+    Certificate, ClientCertVerified, DistinguishedNames,
+    HandshakeSignatureValid, RootCertStore, ServerCertVerified,
+    SignatureScheme, TLSError,
 };
 
 /// Implementation of the `rustls` certificate verification traits for libp2p.
@@ -42,6 +42,9 @@ impl Libp2pCertificateVerifier {
             SignatureScheme::ECDSA_NISTP256_SHA256,
             // TODO SignatureScheme::ED448 is not supported by `ring` yet
             SignatureScheme::ED25519,
+
+            // In particular, RSA SHOULD NOT be used unless
+            // no elliptic curve algorithms are supported.
             SignatureScheme::RSA_PSS_SHA512,
             SignatureScheme::RSA_PSS_SHA384,
             SignatureScheme::RSA_PSS_SHA256,
@@ -55,11 +58,11 @@ impl Libp2pCertificateVerifier {
 impl rustls::ServerCertVerifier for Libp2pCertificateVerifier {
     fn verify_server_cert(
         &self,
-        _roots: &rustls::RootCertStore,
-        presented_certs: &[rustls::Certificate],
+        _roots: &RootCertStore,
+        presented_certs: &[Certificate],
         _dns_name: webpki::DNSNameRef<'_>,
         _ocsp_response: &[u8],
-    ) -> Result<rustls::ServerCertVerified, rustls::TLSError> {
+    ) -> Result<ServerCertVerified, TLSError> {
         verify_certs(presented_certs).map(|_| ServerCertVerified::assertion())
     }
 
@@ -69,6 +72,8 @@ impl rustls::ServerCertVerifier for Libp2pCertificateVerifier {
         _cert: &Certificate,
         _dss: &DigitallySignedStruct,
     ) -> Result<HandshakeSignatureValid, TLSError> {
+        // The libp2p handshake uses TLS 1.3 (and higher).
+        // Endpoints MUST NOT negotiate lower TLS versions.
         Err(TLSError::PeerIncompatibleError("Only TLS 1.3 certificates are supported".to_string()))
     }
 
@@ -94,7 +99,7 @@ impl rustls::ClientCertVerifier for Libp2pCertificateVerifier {
     fn client_auth_root_subjects(
         &self,
         _dns_name: Option<&webpki::DNSName>,
-    ) -> Option<rustls::DistinguishedNames> {
+    ) -> Option<DistinguishedNames> {
         Some(vec![])
     }
 
@@ -102,7 +107,7 @@ impl rustls::ClientCertVerifier for Libp2pCertificateVerifier {
         &self,
         presented_certs: &[Certificate],
         _dns_name: Option<&webpki::DNSName>,
-    ) -> Result<ClientCertVerified, rustls::TLSError> {
+    ) -> Result<ClientCertVerified, TLSError> {
         verify_certs(presented_certs).map(|_| ClientCertVerified::assertion())
     }
 
@@ -112,6 +117,8 @@ impl rustls::ClientCertVerifier for Libp2pCertificateVerifier {
         _cert: &Certificate,
         _dss: &DigitallySignedStruct,
     ) -> Result<HandshakeSignatureValid, TLSError> {
+        // The libp2p handshake uses TLS 1.3 (and higher).
+        // Endpoints MUST NOT negotiate lower TLS versions.
         Err(TLSError::PeerIncompatibleError("Only TLS 1.3 certificates are supported".to_string()))
     }
 
@@ -129,7 +136,13 @@ impl rustls::ClientCertVerifier for Libp2pCertificateVerifier {
     }
 }
 
-fn verify_certs(presented_certs: &[Certificate]) -> Result<(), rustls::TLSError> {
+/// When receiving the certificate chain, an endpoint
+/// MUST check these conditions and abort the connection attempt if
+/// (a) the presented certificate is not yet valid, OR
+/// (b) if it is expired.
+/// Endpoints MUST abort the connection attempt if more than one certificate is received,
+/// or if the certificate’s self-signature is not valid.
+fn verify_certs(presented_certs: &[Certificate]) -> Result<(), TLSError> {
     if presented_certs.len() != 1 {
         return Err(TLSError::NoCertificatesPresented);
     }
@@ -145,14 +158,14 @@ fn verify_certs(presented_certs: &[Certificate]) -> Result<(), rustls::TLSError>
 
 fn verify_tls13_signature(
     cert: &Certificate,
-    signature_scheme: rustls::SignatureScheme,
+    signature_scheme: SignatureScheme,
     message: &[u8],
     signature: &[u8],
 ) -> Result<HandshakeSignatureValid, TLSError> {
     let certificate = crate::certificate::parse_certificate(cert.as_ref())
         .map_err(|_| TLSError::CorruptMessage)?;
     if certificate.verify_signature(signature_scheme, message, signature) {
-        Ok(rustls::HandshakeSignatureValid::assertion())
+        Ok(HandshakeSignatureValid::assertion())
     } else {
         Err(TLSError::CorruptMessage)
     }