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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 sufficient to sign the checksum files only.

The default is configured to create a detached signature for the checksum files with GnuPG and your default key. To enable signing just add

# .goreleaser.yml
signs:
  - artifacts: checksum

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

# .goreleaser.yml
signs:
  -
    # ID of the sign config, must be unique.
    #
    # Defaults to "default".
    id: foo

    # Name/template of the signature file.
    #
    # Defaults to `${artifact}.sig`.
    signature: "${artifact}_sig"

    # Path to the signature command
    #
    # Defaults to `gpg`
    cmd: gpg2

    # Command line templateable arguments for the command
    #
    # to sign with a specific key use
    # args: ["-u", "<key id, fingerprint, email, ...>", "--output", "${signature}", "--detach-sign", "${artifact}"]
    #
    # Defaults to `["--output", "${signature}", "--detach-sign", "${artifact}"]`
    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
    #
    # Defaults to `none`
    artifacts: all

    # IDs of the artifacts to sign.
    #
    # If `artifacts` is checksum or source, this fields has no effect.
    #
    # Defaults to empty (which implies no filtering).
    ids:
      - foo
      - bar

    # Stdin data template to be given to the signature command as stdin.
    #
    # Defaults to empty
    stdin: '{{ .Env.GPG_PASSWORD }}'

    # StdinFile file to be given to the signature command as stdin.
    #
    # Defaults to empty
    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.
    #
    # Defaults to empty.
    certificate: '{{ trimsuffix .Env.artifact ".tar.gz" }}.pem'

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

Available variable names

These environment variables might be available in the fields that are templateable:

  • ${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 you 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:

# .goreleaser.yml
signs:
- cmd: cosign
  stdin: '{{ .Env.COSIGN_PWD }}'
  args: ["sign-blob", "-key=cosign.key", "-output=${signature}", "${artifact}"]
  artifacts: all

Your users can then verify the signature with:

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

Signing executables

Executables can be signed after build using post hooks.

With gon

For example, you can use gon to create notarized MacOS apps:

# .goreleaser.yml
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:

# 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 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:

# .goreleaser.yml
builds:
- hooks:
    post:
      - sh -c "echo $COSIGN_PWD | cosign sign-blob -key cosign.key {{ .Path }} > dist/{{ .ProjectName }}_{{ .Version }}_{{ .Target }}.sig"

# 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.

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:

# .goreleaser.yml
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.