WSL-Helper: Add test for cert use-after-free

Signed-off-by: Mark Yen <[email protected]>

.github/actions/spelling/expect.txt

@@ -243,6 +243,7 @@ fav
 fcb
 fdx
 featurename
+FEEEFEEE
 femto
 ffi
 ficlone

src/go/wsl-helper/pkg/certificates/certificates_windows_test.go

@@ -0,0 +1,47 @@
+package certificates_test
+
+import (
+	"bytes"
+	"crypto/x509"
+	"encoding/pem"
+	"testing"
+
+	"github.com/rancher-sandbox/rancher-desktop/src/go/wsl-helper/pkg/certificates"
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+)
+
+// Test that we don't use memory that we don't own
+func TestGetSystemCertificates_UseAfterFree(t *testing.T) {
+	var certs []*x509.Certificate
+	ch, err := certificates.GetSystemCertificates("CA")
+	require.NoError(t, err, "failed to get CA certificates")
+	for entry := range ch {
+		if assert.NoError(t, err, entry.Err) {
+			certs = append(certs, entry.Cert)
+		}
+	}
+	ch, err = certificates.GetSystemCertificates("ROOT")
+	require.NoError(t, err, "failed to get ROOT certificates")
+	for entry := range ch {
+		if assert.NoError(t, err, entry.Err) {
+			certs = append(certs, entry.Cert)
+		}
+	}
+
+	// By this point, both channels have been closed, which also means we have
+	// closed both cert stores.
+	for _, cert := range certs {
+		buf := bytes.Buffer{}
+		block := &pem.Block{Type: "CERTIFICATE", Bytes: cert.Raw}
+		err = pem.Encode(&buf, block)
+		if assert.NoError(t, err, "Failed to encode certificate") {
+			// Look for invalid certificates:
+			// - A line of all A (nulls)
+			// - A line with 0xFEEEFEEE (HeapAlloc freed marker)
+			output := buf.String()
+			assert.NotContains(t, output, "AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA", "encoded cert contains nulls")
+			assert.NotContains(t, output, "7v7u/u7+7v7u/u7+7v7u/u7+7v7u/u7+7v7u/u7+7v7u/u7+7v7u/u7+7v7u/u7+", "encoded cert contains FEEEFEEE")
+		}
+	}
+}