# MSIX Package

Firefox MSIX packages are full participants in the "modern" Windows
app packaging system. They are distributed, installed, updated,
repaired, and uninstalled entirely using that system. This gives
administrators lots of deployment options, and also grants complete
control over when and how application updates are rolled out
(Firefox's built-in updater is always fully disabled in MSIX
packages). This stands in contrast to Firefox MSI packages, which
mostly work against the Windows Installer framework rather than with
it, and therefore are missing a lot of important functionality; for
example, tools that install MSI packages generally cannot uninstall
Firefox [^footnote-1]. This means the MSIX package may well be the better
option for deploying to Windows 10 and up.

## In automation

The `repackage-msix` and `repackage-shippable-l10n-msix` tasks
repackage the ZIP packages produced by signed build tasks into MSIX
packages. The `shippable-l10n` variants depend on Linux64 builds and
localization tasks to produce signed langpacks, which are incorporated
into the MSIX package as distribution extensions. (This is the same
approach taken by `snap` and `flatpak` Linux packages.)

The `repackage-signing-msix` and
`repackage-signing-shippable-l10n-msix` tasks sign the MSIX packages
produced by the repackage tasks.

### Signing in automation

MSIX packages are signed by the same certificates that sign binaries for
other jobs. In practice, this means that try builds are signed with the
`` `Mozilla Fake CA ``
certificate [MozFakeCA_2017-10-13.cer](https://raw.githubusercontent.com/mozilla-releng/OpenCloudConfig/3493a608bf700b68a54ff2fd506f33373bb87a04/userdata/Configuration/Mozilla%20Maintenance%20Service/MozFakeCA_2017-10-13.cer).
In order to install try builds locally, you must trust this certificate.
**For your own security, it's best to do this in Windows Sandbox or a
Virtual Machine**. To do so run the following in an elevated
(administrator) Powershell:

```
$ Import-Certificate -FilePath "MozFakeCA_2017-10-13.cer" -Cert Cert:\LocalMachine\Root\
...
Thumbprint                                Subject
----------                                -------
FA056CEBEFF3B1D0500A1FB37C2BD2F9CE4FB5D8  CN=Mozilla Fake CA
```

The `shippable-l10n` MSIX variants incorporate signed langpacks. These
in turn are signed with the same certificate. Firefox knows about this
certificate but does not trust it by default. To trust it, set the
hidden Gecko boolean preference

```
xpinstall.signatures.dev-root=true
```

Sadly, it's not possible to set preferences via a `distribution.ini`
early enough to impact loading the signed langpacks (see [Bug
1721764](https://bugzilla.mozilla.org/show_bug.cgi?id=1721764)), and
once the signed langpacks fail to load once, they will not be reloaded
(see [Bug
1721763](https://bugzilla.mozilla.org/show_bug.cgi?id=1721763)). This
make testing the first-run experience challenging. What can be done is
to install the MSIX package (perhaps using
`Add-AppxPackage -Path ...`) and determine the profile directory
(using `about:support`). Uninstall the MSIX package (perhaps using
`Get-AppxPackage | Where -Property Name -like "Mozilla.*" | Remove-AppxPackage`).
Delete the contents of the profile directory entirely, but add a file
`user.js` containing:

```
user_pref("xpinstall.signatures.dev-root", true);
user_pref("extensions.logging.enabled", true);
```

Reinstall the MSIX package and the signed langpacks should now be loaded
(slowly!) and available after first startup.

## Local developer builds

`mach repackage msix` lets you repackage a Firefox package (or
directory) into an MSIX/App Package. The main complication is that an
App Package contains channel-specific paths and assets, and therefore
needs to be branding-aware, much as an Android package needs to be
branding-aware.

### Usage

The tool is designed to repackage ZIP archives produced in automation.
Start looking for official builds at locations like:

| Channel    | URL                                                                                                                          |
| ---------- | ---------------------------------------------------------------------------------------------------------------------------- |
| Release    | <https://archive.mozilla.org/pub/firefox/candidates/88.0.1-candidates/build1/win64/en-US/firefox-88.0.1.zip>                 |
| Beta       | <https://archive.mozilla.org/pub/firefox/candidates/89.0b15-candidates/build1/win64/en-US/firefox-89.0b15.zip>               |
| Devedition | <https://archive.mozilla.org/pub/devedition/candidates/89.0b15-candidates/build1/win64/en-US/firefox-89.0b15.zip>            |
| Nightly    | <https://archive.mozilla.org/pub/firefox/nightly/2021/05/2021-05-21-09-57-54-mozilla-central/firefox-90.0a1.en-US.win64.zip> |

Repackage using commands like:

```
$ ./mach repackage msix \
  --input firefox-88.0.1.zip \
  --channel=official \
  --arch=x86_64 \
  --verbose
```

Or package a local developer build directly with `mach repackage msix`:

```
$ ./mach repackage msix
```

This command will do its best to guess your channel and other necessary
information. You can override these with options like `--channel`
(see the `--help` text for all supported options).

Paths to tools can be set via environment variables. In order, searched
first to searched last:

1. the tool name, like `MAKEAPPX` or `SIGNTOOL`
2. searching on `PATH`
3. searching under `WINDOWSSDKDIR`
4. searching under `C:/Program Files (x86)/Windows Kits/10`

If you are cross compiling from Linux or macOS you will need a
compiled version of [Mozilla's fork of Microsoft's msix-packaging](https://github.com/mozilla/msix-packaging/tree/johnmcpms/signing)
tools.

Linux users can obtain a prebuilt version with:

```
$ ./mach artifact toolchain --from-build linux64-msix-packaging
```

After [bug 1743036](https://bugzilla.mozilla.org/show_bug.cgi?id=1743036)
is fixed, macOS and Windows users will have a similar option.

### Avoiding signing locally with unsigned packages

Windows 11 allows to install unsigned packages, provided that its AppX
manifest includes a special OID (organization ID) value in its
`Identity` element. See
<https://github.com/MicrosoftDocs/msix-docs/blob/769dee9364df2b6fd0b78000774f8d14de8fe814/msix-src/package/unsigned-package.md>.
To produce a suitable package, use the `--unsigned` command line
switch, like:

```
$ ./mach repackage msix --unsigned
```

Note that unsigned packages **must** be installed by an administrator.
Generally, run Powershell as an administrator and then use commands like

```
$ Add-AppxPackage -Path ... -AllowUnsigned -ForceUpdateFromAnyVersion
```

### Signing locally

The repackaged MSIX files produced are not signed by default. In
automation, Mozilla's signing service signs the repackaged MSIX files.
For local testing, you can sign them with a self-signed certificate by
adding `--sign` to `mach repackage msix`, or with commands like:

```
$ ./mach repackage sign-msix --input test.msix --verbose
```

Or sign them yourself following [Microsoft's self-signed certificate
instructions](https://docs.microsoft.com/en-us/windows/msix/package/create-certificate-package-signing#create-a-self-signed-certificate).

#### Signing Certificates

Mach will create the necessary signing keys and certificates for you
and reuse them for subsequent signings. Before your locally signed
builds can be installed you will need to install the correct
certificate to the Windows Root Store. This can be done with a command
like:

```
$ powershell -c 'Import-Certificate -FilePath mycert.cer -Cert Cert:\LocalMachine\Root\'
```

The exact command to run will be shown if you run `./mach repackage`
with `--verbose`.

You \_may\_ choose to sign in a different manner, with a key and certificate
you create yourself, but Windows requires that the Subject of the certificate
match the Publisher found in the MSIX's AppxManifest.xml. If you choose
to go this route, ensure that you pass `--publisher` to
`./mach repackage msix` to set that correctly.

### For developers

#### Updating the MSIX template

MSIX is an "open format" in one sense: the MSIX container format is
specified at <https://github.com/Microsoft/msix-packaging>. It is
categorically *not* an open format in another sense: many of the
contained files are proprietary binary formats (`.reg` -- registry
hive files) or undocumented (`.pri` files -- resource index files).

Generally the MSIX packaging code tries to avoid requiring such files
that can't be built from sources. Where they are truly required, it
tries to use a single such file independent of branding and other
configuration, checked into the source tree.

##### resources.pri

Generate a new `resources.pri` file on a Windows machine using
`makepri.exe` from the Windows SDK, like:

```
$ makepri.exe new \
    -IndexName firefox \
    -ConfigXml browser/installer/windows/msix/priconfig.xml \
    -ProjectRoot browser/branding/official/msix \
    -OutputFile browser/installer/windows/msix/resources.pri \
    -Overwrite
```

The choice of channel (i.e.,
`browser/branding/{official,aurora,beta,nightly,unofficial}`) should
not matter.

[^footnote-1]: The MSI has to be limited in this way because of the difficulty
    of migrating existing installations into MSI and adding support
    for it to Firefox's update pipeline. MSIX does not have these
    constraints, because the partially virtualized file system that
    these kinds of apps run in makes install migration impossible
    and unnecessary.
