# Signing checksums and artifacts

Signing ensures that the artifacts have been generated by yourself, and your
users can verify that by comparing the generated signature with your public
signing key.

GoReleaser provides means to sign both executables and archives.

## Usage

Signing works in combination with checksum files, and it is generally enough
to sign the checksum files only.

The default is configured to create a detached signature for the checksum files
with [GnuPG](https://www.gnupg.org/), and your default key. To enable signing
just add

```yaml
# .goreleaser.yaml
signs:
  - artifacts: checksum
```

To customize the signing pipeline you can use the following options:

```yaml
# .goreleaser.yaml
signs:
  -
    # ID of the sign config, must be unique.
    #
    # Default: 'default'
    id: foo

    # Name of the signature file.
    #
    # Default: '${artifact}.sig'
    # Templates: allowed
    signature: "${artifact}_sig"

    # Path to the signature command
    #
    # Default: 'gpg'
    cmd: gpg2

    # Command line arguments for the command
    #
    # to sign with a specific key use
    # args: ["-u", "<key id, fingerprint, email, ...>", "--output", "${signature}", "--detach-sign", "${artifact}"]
    #
    # Default: ["--output", "${signature}", "--detach-sign", "${artifact}"]
    # Templates: allowed
    args: ["--output", "${signature}", "${artifact}", "{{ .ProjectName }}"]

    # Which artifacts to sign
    #
    #   all:      all artifacts
    #   none:     no signing
    #   checksum: only checksum file(s)
    #   source:   source archive
    #   package:  linux packages (deb, rpm, apk)
    #   archive:  archives from archive pipe
    #   binary:   binaries if archiving format is set to binary
    #   sbom:     any Software Bill of Materials generated for other artifacts
    #
    # Default: 'none'
    artifacts: all

    # IDs of the artifacts to sign.
    #
    # If `artifacts` is checksum or source, this fields has no effect.
    ids:
      - foo
      - bar

    # Stdin data to be given to the signature command as stdin.
    #
    # Templates: allowed
    stdin: '{{ .Env.GPG_PASSWORD }}'

    # StdinFile file to be given to the signature command as stdin.
    stdin_file: ./.password

    # Sets a certificate that your signing command should write to.
    # You can later use `${certificate}` or `.Env.certificate` in the `args` section.
    # This is particularly useful for keyless signing (for instance, with cosign).
    # Note that this should be a name, not a path.
    certificate: '{{ trimsuffix .Env.artifact ".tar.gz" }}.pem'

    # List of environment variables that will be passed to the signing command
    # as well as the templates.
    env:
    - FOO=bar
    - HONK=honkhonk

    # By default, the stdout and stderr of the signing cmd are discarded unless
    # GoReleaser is running with `--debug` set.
    # You can set this to true if you want them to be displayed regardless.
    #
    # Since: v1.2
    output: true
```

### Available variable names

These environment variables might be available in the fields that accept
templates:

- `${artifact}`: the path to the artifact that will be signed
- `${artifactID}`: the ID of the artifact that will be signed
- `${certificate}`: the certificate filename, if provided
- `${signature}`: the signature filename

## Signing with cosign

You can sign your artifacts with [cosign][] as well.

Assuming you have a `cosign.key` in the repository root and a `COSIGN_PWD`
environment variable set, a simple usage example would look like this:

```yaml
# .goreleaser.yaml
signs:
- cmd: cosign
  stdin: '{{ .Env.COSIGN_PWD }}'
  args:
  - "sign-blob"
  - "--key=cosign.key"
  - "--output-signature=${signature}"
  - "${artifact}"
  - "--yes" # needed on cosign 2.0.0+
  artifacts: all
```

Your users can then verify the signature with:

```sh
cosign verify-blob -key cosign.pub -signature file.tar.gz.sig file.tar.gz
```

<!-- TODO: keyless signing with cosign example -->

## Signing executables

Executables can be signed after build using post hooks.

### With gon

For example, you can use [gon][] to create notarized macOS apps:

```yaml
# .goreleaser.yaml
builds:
- binary: foo
  id: foo
  goos:
  - linux
  - windows
  goarch:
  - amd64

# notice that we need a separated build for the MacOS binary only:
- binary: foo
  id: foo-macos
  goos:
  - darwin
  goarch:
  - amd64
  hooks:
    post: gon gon.hcl
```

and:

```terraform
# gon.hcl
#
# The path follows a pattern
# ./dist/BUILD-ID_TARGET/BINARY-NAME
source = ["./dist/foo-macos_darwin_amd64/foo"]
bundle_id = "com.mitchellh.example.terraform"

apple_id {
  username = "mitchell@example.com"
  password = "@env:AC_PASSWORD"
}

sign {
  application_identity = "Developer ID Application: Mitchell Hashimoto"
}
```

Note that notarizing may take some time, and will need to be run from a macOS
machine.

If you generate ZIP or DMG as part of your signing via gon you may need to
ensure their file names align with desired pattern of other artifacts as
GoReleaser doesn't control how these get generated beyond just executing `gon`
with given arguments. Relatedly you may need to list these additional artifacts
as `extra_files` in the `release` section to make sure they also get uploaded.

You can also check
[this issue](https://github.com/goreleaser/goreleaser/issues/1227) for more
details.


### With cosign

You can also use [cosign][] to sign the binaries directly, but you'll need to
manually add the `.sig` files to the release and/or archive:

```yaml
# .goreleaser.yaml
builds:
- hooks:
    post:
      - sh -c "COSIGN_PASSWORD=$COSIGN_PWD cosign sign-blob --key cosign.key --output-signature dist/{{ .ProjectName }}_{{ .Version }}_{{ .Target }}.sig {{ .Path }}"

# add to the release directly:
release:
  extra_files:
  - glob: dist/*.sig

# or just to the archives:
archives:
- files:
  - dist/*.sig
```

While this works, I would recommend using the signing pipe directly.

## Signing Docker images and manifests

Please refer to [Docker Images Signing](/customization/docker_sign/).

## Limitations

You can sign with any command that either outputs a file or modify the file
being signed.

If you want to sign with something that writes to `STDOUT` instead of a file,
you can wrap the command inside a `sh -c` execution, for instance:

```yaml
# .goreleaser.yaml
signs:
- cmd: sh
  args:
  - '-c'
  - 'echo "${artifact} is signed and I can prove it" | tee ${signature}'
  artifacts: all
```

And it will work just fine. Just make sure to always use the `${signature}`
template variable as the result file name and `${artifact}` as the origin file.

[gon]: https://github.com/mitchellh/gon
[cosign]: https://github.com/sigstore/cosign
