Implement GetRemoteCertificate for DTLSTransport in wasm

dtlstransport_js.go

@@ -34,3 +34,32 @@ func (r *DTLSTransport) ICETransport() *ICETransport {
 		underlying: underlying,
 	}
 }
+
+func (t *DTLSTransport) GetRemoteCertificate() []byte {
+	if t.underlying.IsNull() || t.underlying.IsUndefined() {
+		return nil
+	}
+
+	// Firefox does not support getRemoteCertificates: https://bugzilla.mozilla.org/show_bug.cgi?id=1805446
+	jsGet := t.underlying.Get("getRemoteCertificates")
+	if jsGet.IsUndefined() || jsGet.IsNull() {
+		return nil
+	}
+
+	jsCerts := t.underlying.Call("getRemoteCertificates")
+	if jsCerts.Length() == 0 {
+		return nil
+	}
+
+	buf := jsCerts.Index(0)
+	u8 := js.Global().Get("Uint8Array").New(buf)
+
+	if u8.Length() == 0 {
+		return nil
+	}
+
+	cert := make([]byte, u8.Length())
+	js.CopyBytesToGo(cert, u8)
+
+	return cert
+}

peerconnection_js_test.go

@@ -121,3 +121,24 @@ func TestPeerConnectionCanTrickleICECandidatesJS(t *testing.T) {
 	pc.underlying = js.ValueOf(map[string]any{})
 	assert.Equal(t, ICETrickleCapabilityUnknown, pc.CanTrickleICECandidates())
 }
+
+func TestDTLSTransportGetRemoteCertificateMock(t *testing.T) {
+	expected := []byte{0x01, 0x02, 0x03, 0x04}
+
+	u8 := js.Global().Get("Uint8Array").New(len(expected))
+	if n := js.CopyBytesToJS(u8, expected); n != len(expected) {
+		t.Fatalf("copied %d bytes to Uint8Array; expected %d", n, len(expected))
+	}
+	certBuffer := u8.Get("buffer")
+
+	getRemoteCertificates := js.FuncOf(func(this js.Value, args []js.Value) any {
+		return js.ValueOf([]any{certBuffer})
+	})
+	defer getRemoteCertificates.Release()
+
+	mockTransport := js.Global().Get("Object").New()
+	mockTransport.Set("getRemoteCertificates", getRemoteCertificates)
+
+	dtlsTransport := &DTLSTransport{underlying: mockTransport}
+	assert.Equal(t, expected, dtlsTransport.GetRemoteCertificate())
+}