match-version-unlocker

An Atmosphere sysmodule for the Switch 1 that lets you share game updates with a Switch 2 through "Match Version with Local Users", for games where the Switch 2 otherwise cancels the update with error 2211-0520.

The problem

You want to keep your Switch 2 offline but some games show you an "Update required" error when you try to start them from a Switch 1 cartridge.
When a Switch 1 on firmware 20.0.0 or newer offers an update to a Switch 2 for a game that has a Switch 2 Edition or other Switch 2 specific content, the Switch 2 aborts the session:

• Switch 2: error 2211-0520
• Switch 1: the update can't be performed

Confirmed with Switch 1 (21.1.0) to Switch 2 (21.1.0)

• Animal Crossing: New Horizons - SuperXCI - 01006F8002326000 (1.8.0 -> 3.0.3)
• The Legend of Zelda: Breath of the Wild - SuperXCI - 01007EF00011E000 (1.6.0 -> 1.9.0)
• The Legend of Zelda: Tears of the Kingdom - XCI - 0100F2C0115B6000 (1.0.0 -> 1.4.3)
• Super Mario Bros. Wonder - SuperXCI - 010015100B514000 (1.0.1 -> 1.2.0) (also tested on 23.0.1 S1/S2 - AMS1.12.1 thank you jasapolis!)
• Mario Kart 8 Deluxe - SuperXCI - 0100152000022000 (3.0.3 -> 3.0.5)

Why it happens

The update offer contains an ApplicationDeliveryInfo, built and HMAC-signed by the sending console's ns. Since 20.0.0 it includes the ProperProgramExists content meta attribute, which ns reads with ncm IContentMetaDatabase::GetAttributes.

The receiving Switch 2 checks the sender's info with an extended CanDeliverApplication (ns command 2019, documented on switchbrew). When the sender is a different platform, it only accepts:

ContentMetaPlatform == 0 && ProperProgramExists == 0

A Switch 1 on 20.0.0+ reports ProperProgramExists = 1 for these games, so the Switch 2 refuses. Consoles on 18.x / 19.x never set the field, which is why they work.

What this module does

It intercepts ncm for the ns process only and clears the ProperProgramExists bit in GetAttributes results for applications and patches. ns then builds and signs the delivery info itself with ProperProgramExists = 0, and the Switch 2 accepts the update. All other ncm commands and all other processes are passed through unchanged.

The Switch 2 receives the regular Switch 1 version of the update.

Requirements

• Switch 1 running Atmosphere, firmware 19.0.0 or newer. One build covers all of them, including firmware released after the build: there is no upper limit. Below 19.0.0 the module stays inactive.
• ProperProgramExists was added in 20.0.0. On 19.x the module runs but most likely has nothing to change.
• No other sysmodule that lists ncm in its mitm.lst. Two modules declaring the same service make Atmosphere abort at boot.

Only the sending Switch 1 needs the module. The Switch 2 stays unmodified.

Installation

1. Download the latest release zip.
2. Extract it to the root of the SD card. It contains atmosphere/contents/42000000162C63DA/.
3. Reboot.

Usage

On both consoles, highlight the game on the HOME Menu, press + (Options) and select Software Update > Match Version with Local Users. Create the group on one console and join it with the other. The console with the newer version sends the update.

Risks

• It changes data the Switch 2 uses to decide compatibility. The Switch 2 gets the Switch 1 version of the update. If the game misbehaves on the Switch 2, or after buying the Nintendo Switch 2 Edition, update the game on the Switch 2 over the internet.

Building

Requires devkitPro with the Switch packages (switch-dev).

git clone --recursive https://github.com/Knight1/match-version-unlocker
cd match-version-unlocker
make

The output is in dist/. make release also creates a zip.

The program ID is set once, as title_id in config.json; the Makefile reads it from there for the atmosphere/contents/<ID>/ folder.

The Makefile applies patches/libstratosphere-allow-unknown-firmware.patch to the Atmosphere-libs submodule. Without it, libstratosphere aborts at startup on firmware it doesn't know, which would leave ns waiting and hang the boot. With it, the module also runs on firmware released after the build.

The Atmosphere libs need a newer libnx than the latest libnx release. The libnx submodule is pinned to libnx master as of the Atmosphere release; the Makefile builds it into build/ and uses it instead of the libnx installed with devkitPro, which stays untouched.

GitHub Actions builds every push with the latest devkitPro image and attaches the zip to releases created from v* tags.

Credits ❤️

• switchbrew Community, for documenting ns, ncm and ldn
• SciresM for creating Atmosphere-NX and libstratosphere
• ldn_debug_logger, which this module grew out of.

License

GPLv2, see LICENSE.