From d0a6318334b5cb0421b17c4478defac6356f4533 Mon Sep 17 00:00:00 2001
From: Luis Neto <lneto@cloudflare.com>
Date: Tue, 1 Jul 2025 12:24:59 +0100
Subject: [PATCH] TUN-9161: Remove P256Kyber768Draft00PQKex curve from nonFips
 curve preferences

Remove P256Kyber768Draft00PQKex curve from nonFips curve preferences and add tests to verify that the advertised curves are the same as the curve preferences we set.

Closes TUN-9161
---
 supervisor/pqtunnels.go      |  4 ++--
 supervisor/pqtunnels_test.go | 41 +++++++++++++++++++++++++++++++++---
 2 files changed, 40 insertions(+), 5 deletions(-)

diff --git a/supervisor/pqtunnels.go b/supervisor/pqtunnels.go
index 2eaad9e8..30eb2e87 100644
--- a/supervisor/pqtunnels.go
+++ b/supervisor/pqtunnels.go
@@ -17,8 +17,8 @@ const (
 )
 
 var (
-	nonFipsPostQuantumStrictPKex []tls.CurveID = []tls.CurveID{X25519MLKEM768PQKex, X25519Kyber768Draft00PQKex}
-	nonFipsPostQuantumPreferPKex []tls.CurveID = []tls.CurveID{X25519MLKEM768PQKex, X25519Kyber768Draft00PQKex}
+	nonFipsPostQuantumStrictPKex []tls.CurveID = []tls.CurveID{X25519MLKEM768PQKex}
+	nonFipsPostQuantumPreferPKex []tls.CurveID = []tls.CurveID{X25519MLKEM768PQKex}
 	fipsPostQuantumStrictPKex    []tls.CurveID = []tls.CurveID{P256Kyber768Draft00PQKex}
 	fipsPostQuantumPreferPKex    []tls.CurveID = []tls.CurveID{P256Kyber768Draft00PQKex, tls.CurveP256}
 )
diff --git a/supervisor/pqtunnels_test.go b/supervisor/pqtunnels_test.go
index 383200db..3be54460 100644
--- a/supervisor/pqtunnels_test.go
+++ b/supervisor/pqtunnels_test.go
@@ -2,12 +2,16 @@ package supervisor
 
 import (
 	"crypto/tls"
+	"net/http"
+	"net/http/httptest"
+	"slices"
 	"testing"
 
 	"github.com/stretchr/testify/assert"
 	"github.com/stretchr/testify/require"
 
 	"github.com/cloudflare/cloudflared/features"
+	"github.com/cloudflare/cloudflared/fips"
 )
 
 func TestCurvePreferences(t *testing.T) {
@@ -48,7 +52,7 @@ func TestCurvePreferences(t *testing.T) {
 			pqMode:         features.PostQuantumPrefer,
 			fipsEnabled:    false,
 			currentCurves:  []tls.CurveID{tls.CurveP256},
-			expectedCurves: []tls.CurveID{X25519MLKEM768PQKex, X25519Kyber768Draft00PQKex, tls.CurveP256},
+			expectedCurves: []tls.CurveID{X25519MLKEM768PQKex, tls.CurveP256},
 		},
 		{
 			name:           "Non FIPS with Prefer PQ - no duplicates",
@@ -62,14 +66,14 @@ func TestCurvePreferences(t *testing.T) {
 			pqMode:         features.PostQuantumPrefer,
 			fipsEnabled:    false,
 			currentCurves:  []tls.CurveID{tls.CurveP256, X25519Kyber768Draft00PQKex},
-			expectedCurves: []tls.CurveID{X25519MLKEM768PQKex, X25519Kyber768Draft00PQKex, tls.CurveP256},
+			expectedCurves: []tls.CurveID{X25519MLKEM768PQKex, tls.CurveP256, X25519Kyber768Draft00PQKex},
 		},
 		{
 			name:           "Non FIPS with Strict PQ",
 			pqMode:         features.PostQuantumStrict,
 			fipsEnabled:    false,
 			currentCurves:  []tls.CurveID{tls.CurveP256},
-			expectedCurves: []tls.CurveID{X25519MLKEM768PQKex, X25519Kyber768Draft00PQKex},
+			expectedCurves: []tls.CurveID{X25519MLKEM768PQKex},
 		},
 	}
 
@@ -82,3 +86,34 @@ func TestCurvePreferences(t *testing.T) {
 		})
 	}
 }
+
+func runClientServerHandshake(t *testing.T, curves []tls.CurveID) []tls.CurveID {
+	var advertisedCurves []tls.CurveID
+	ts := httptest.NewUnstartedServer(nil)
+	ts.TLS = &tls.Config{ // nolint: gosec
+		GetConfigForClient: func(chi *tls.ClientHelloInfo) (*tls.Config, error) {
+			advertisedCurves = slices.Clone(chi.SupportedCurves)
+			return nil, nil
+		},
+	}
+	ts.StartTLS()
+	defer ts.Close()
+	clientTlsConfig := ts.Client().Transport.(*http.Transport).TLSClientConfig
+	clientTlsConfig.CurvePreferences = curves
+	resp, err := ts.Client().Head(ts.URL)
+	if err != nil {
+		t.Error(err)
+		return nil
+	}
+	defer resp.Body.Close()
+	return advertisedCurves
+}
+
+func TestSupportedCurvesNegotiation(t *testing.T) {
+	for _, tcase := range []features.PostQuantumMode{features.PostQuantumPrefer} {
+		curves, err := curvePreference(tcase, fips.IsFipsEnabled(), make([]tls.CurveID, 0))
+		require.NoError(t, err)
+		advertisedCurves := runClientServerHandshake(t, curves)
+		assert.Equal(t, curves, advertisedCurves)
+	}
+}