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Add (skopeo generate-sigstore-key) #1869

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1 change: 1 addition & 0 deletions README.md
Original file line number Diff line number Diff line change
Expand Up @@ -208,6 +208,7 @@ Please read the [contribution guide](CONTRIBUTING.md) if you want to collaborate
| -------------------------------------------------- | ---------------------------------------------------------------------------------------------|
| [skopeo-copy(1)](/docs/skopeo-copy.1.md) | Copy an image (manifest, filesystem layers, signatures) from one location to another. |
| [skopeo-delete(1)](/docs/skopeo-delete.1.md) | Mark the image-name for later deletion by the registry's garbage collector. |
| [skopeo-generate-sigstore-key(1)](/docs/skopeo-generate-sigstore-key.1.md) | Generate a sigstore public/private key pair. |
| [skopeo-inspect(1)](/docs/skopeo-inspect.1.md) | Return low-level information about image-name in a registry. |
| [skopeo-list-tags(1)](/docs/skopeo-list-tags.1.md) | Return a list of tags for the transport-specific image repository. |
| [skopeo-login(1)](/docs/skopeo-login.1.md) | Login to a container registry. |
Expand Down
90 changes: 90 additions & 0 deletions cmd/skopeo/generate_sigstore_key.go
Original file line number Diff line number Diff line change
@@ -0,0 +1,90 @@
package main

import (
"errors"
"fmt"
"io"
"io/fs"
"os"

"github.com/containers/image/v5/pkg/cli"
"github.com/containers/image/v5/signature/sigstore"
"github.com/spf13/cobra"
)

type generateSigstoreKeyOptions struct {
outputPrefix string
passphraseFile string
}

func generateSigstoreKeyCmd() *cobra.Command {
var opts generateSigstoreKeyOptions
cmd := &cobra.Command{
Use: "generate-sigstore-key [command options] --output-prefix PREFIX",
Short: "Generate a sigstore public/private key pair",
RunE: commandAction(opts.run),
Example: "skopeo generate-sigstore-key --output-prefix my-key",
}
adjustUsage(cmd)
flags := cmd.Flags()
flags.StringVar(&opts.outputPrefix, "output-prefix", "", "Write the keys to `PREFIX`.pub and `PREFIX`.private")
flags.StringVar(&opts.passphraseFile, "passphrase-file", "", "Read a passphrase for the private key from `PATH`")
return cmd
}

// ensurePathDoesNotExist verifies that path does not refer to an existing file,
// and returns an error if so.
func ensurePathDoesNotExist(path string) error {
switch _, err := os.Stat(path); {
case err == nil:
return fmt.Errorf("Refusing to overwrite existing %q", path)
case errors.Is(err, fs.ErrNotExist):
return nil
default:
return fmt.Errorf("Error checking existence of %q: %w", path, err)
}
}

func (opts *generateSigstoreKeyOptions) run(args []string, stdout io.Writer) error {
if len(args) != 0 || opts.outputPrefix == "" {
return errors.New("Usage: generate-sigstore-key --output-prefix PREFIX")
}

pubKeyPath := opts.outputPrefix + ".pub"
privateKeyPath := opts.outputPrefix + ".private"
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.private or just .key?

.key is somewhat traditional, OTOH users publish private keys often enough that making that harder seems worthwhile.

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👍 on .private. I am very likely such a user that would do it on low caffeine.

if err := ensurePathDoesNotExist(pubKeyPath); err != nil {
return err
}
if err := ensurePathDoesNotExist(privateKeyPath); err != nil {
return err
}

var passphrase string
if opts.passphraseFile != "" {
p, err := cli.ReadPassphraseFile(opts.passphraseFile)
if err != nil {
return err
}
passphrase = p
} else {
p, err := promptForPassphrase(privateKeyPath, os.Stdin, os.Stdout)
if err != nil {
return err
}
passphrase = p
}

keys, err := sigstore.GenerateKeyPair([]byte(passphrase))
if err != nil {
return fmt.Errorf("Error generating key pair: %w", err)
}

if err := os.WriteFile(privateKeyPath, keys.PrivateKey, 0600); err != nil {
return fmt.Errorf("Error writing private key to %q: %w", privateKeyPath, err)
}
if err := os.WriteFile(pubKeyPath, keys.PublicKey, 0644); err != nil {
return fmt.Errorf("Error writing private key to %q: %w", pubKeyPath, err)
}
fmt.Fprintf(stdout, "Key written to %q and %q", privateKeyPath, pubKeyPath)
return nil
}
79 changes: 79 additions & 0 deletions cmd/skopeo/generate_sigstore_key_test.go
Original file line number Diff line number Diff line change
@@ -0,0 +1,79 @@
package main

import (
"os"
"path/filepath"
"testing"

"github.com/stretchr/testify/assert"
"github.com/stretchr/testify/require"
)

func TestGenerateSigstoreKey(t *testing.T) {
// Invalid command-line arguments
for _, args := range [][]string{
{},
{"--output-prefix", "foo", "a1"},
} {
out, err := runSkopeo(append([]string{"generate-sigstore-key"}, args...)...)
assertTestFailed(t, out, err, "Usage")
}

// One of the destination files already exists
outputSuffixes := []string{".pub", ".private"}
for _, suffix := range outputSuffixes {
dir := t.TempDir()
prefix := filepath.Join(dir, "prefix")
err := os.WriteFile(prefix+suffix, []byte{}, 0600)
require.NoError(t, err)
out, err := runSkopeo("generate-sigstore-key",
"--output-prefix", prefix, "--passphrase-file", "/dev/null",
)
assertTestFailed(t, out, err, "Refusing to overwrite")
}

// One of the destinations is inaccessible (simulate by a symlink that tries to
// traverse a non-directory)
for _, suffix := range outputSuffixes {
dir := t.TempDir()
nonDirectory := filepath.Join(dir, "nondirectory")
err := os.WriteFile(nonDirectory, []byte{}, 0600)
require.NoError(t, err)
prefix := filepath.Join(dir, "prefix")
err = os.Symlink(filepath.Join(nonDirectory, "unaccessible"), prefix+suffix)
require.NoError(t, err)
out, err := runSkopeo("generate-sigstore-key",
"--output-prefix", prefix, "--passphrase-file", "/dev/null",
)
assertTestFailed(t, out, err, prefix+suffix) // + an OS-specific error message
}
destDir := t.TempDir()
// Error reading passphrase
out, err := runSkopeo("generate-sigstore-key",
"--output-prefix", filepath.Join(destDir, "prefix"),
"--passphrase-file", filepath.Join(destDir, "this-does-not-exist"),
)
assertTestFailed(t, out, err, "this-does-not-exist")

// (The interactive passphrase prompting is not yet tested)

// Error writing outputs is untested: when unit tests run as root, we can’t use permissions on a directory to cause write failures,
// with the --output-prefix mechanism, and refusing to even start writing to pre-exisiting files, directories are the only mechanism
// we have to trigger a write failure.

// Success
// Just a smoke-test, useability of the keys is tested in the generate implementation.
dir := t.TempDir()
prefix := filepath.Join(dir, "prefix")
passphraseFile := filepath.Join(dir, "passphrase")
err = os.WriteFile(passphraseFile, []byte("some passphrase"), 0600)
require.NoError(t, err)
out, err = runSkopeo("generate-sigstore-key",
"--output-prefix", prefix, "--passphrase-file", passphraseFile,
)
assert.NoError(t, err)
for _, suffix := range outputSuffixes {
assert.Contains(t, out, prefix+suffix)
}

}
1 change: 1 addition & 0 deletions cmd/skopeo/main.go
Original file line number Diff line number Diff line change
Expand Up @@ -98,6 +98,7 @@ func createApp() (*cobra.Command, *globalOptions) {
rootCommand.AddCommand(
copyCmd(&opts),
deleteCmd(&opts),
generateSigstoreKeyCmd(),
inspectCmd(&opts),
layersCmd(&opts),
loginCmd(&opts),
Expand Down
47 changes: 47 additions & 0 deletions docs/skopeo-generate-sigstore-key.1.md
Original file line number Diff line number Diff line change
@@ -0,0 +1,47 @@
% skopeo-generate-sigstore-key(1)

## NAME
skopeo\-generate-sigstore-key - Generate a sigstore public/private key pair.

## SYNOPSIS
**skopeo generate-sigstore-key** [*options*] **--output-prefix** _prefix_

## DESCRIPTION

Generates a public/private key pair suitable for creating sigstore image signatures.
The private key is encrypted with a passphrase;
if one is not provided using an option, this command prompts for it interactively.

The private key is written to _prefix_**.private** .
The private key is written to _prefix_**.pub** .

## OPTIONS

**--help**, **-h**

Print usage statement

**--output-prefix** _prefix_

Mandatory.
Path prefix for the output keys (_prefix_**.private** and _prefix_**.pub**).

**--passphrase-file** _path_

The passphare to use to encrypt the private key.
Only the first line will be read.
A passphrase stored in a file is of questionable security if other users can read this file.
Do not use this option if at all avoidable.

## EXAMPLES

```sh
$ skopeo generate-sigstore-key --output-prefix mykey
```

# SEE ALSO
skopeo(1), skopeo-copy(1), containers-policy.json(5)

## AUTHORS

Miloslav Trmač <mitr@redhat.com>
1 change: 1 addition & 0 deletions docs/skopeo.1.md
Original file line number Diff line number Diff line change
Expand Up @@ -101,6 +101,7 @@ Print the version number
| ----------------------------------------- | ------------------------------------------------------------------------------ |
| [skopeo-copy(1)](skopeo-copy.1.md) | Copy an image (manifest, filesystem layers, signatures) from one location to another. |
| [skopeo-delete(1)](skopeo-delete.1.md) | Mark the _image-name_ for later deletion by the registry's garbage collector. |
| [skopeo-generate-sigstore-key(1)](skopeo-generate-sigstore-key.1.md) | Generate a sigstore public/private key pair. |
| [skopeo-inspect(1)](skopeo-inspect.1.md) | Return low-level information about _image-name_ in a registry. |
| [skopeo-list-tags(1)](skopeo-list-tags.1.md) | List image names in a transport-specific collection of images.|
| [skopeo-login(1)](skopeo-login.1.md) | Login to a container registry. |
Expand Down
16 changes: 9 additions & 7 deletions go.mod
Original file line number Diff line number Diff line change
Expand Up @@ -4,7 +4,7 @@ go 1.17

require (
github.com/containers/common v0.50.1
github.com/containers/image/v5 v5.23.1-0.20230113185223-cf9ccfb4d9b1
github.com/containers/image/v5 v5.23.1-0.20230123151557-ed23a0036192
github.com/containers/ocicrypt v1.1.7
github.com/containers/storage v1.45.3
github.com/docker/distribution v2.8.1+incompatible
Expand All @@ -30,16 +30,18 @@ require (
github.com/asaskevich/govalidator v0.0.0-20210307081110-f21760c49a8d // indirect
github.com/containerd/cgroups v1.0.4 // indirect
github.com/containerd/stargz-snapshotter/estargz v0.13.0 // indirect
github.com/containers/libtrust v0.0.0-20200511145503-9c3a6c22cd9a // indirect
github.com/coreos/go-oidc/v3 v3.4.0 // indirect
github.com/containers/libtrust v0.0.0-20230121012942-c1716e8a8d01 // indirect
github.com/coreos/go-oidc/v3 v3.5.0 // indirect
github.com/cyberphone/json-canonicalization v0.0.0-20220623050100-57a0ce2678a7 // indirect
github.com/cyphar/filepath-securejoin v0.2.3 // indirect
github.com/davecgh/go-spew v1.1.1 // indirect
github.com/docker/docker v20.10.22+incompatible // indirect
github.com/docker/docker v20.10.23+incompatible // indirect
github.com/docker/docker-credential-helpers v0.7.0 // indirect
github.com/docker/go-connections v0.4.0 // indirect
github.com/docker/go-units v0.5.0 // indirect
github.com/dsnet/compress v0.0.2-0.20210315054119-f66993602bf5 // indirect
github.com/ghodss/yaml v1.0.0 // indirect
github.com/go-jose/go-jose/v3 v3.0.0 // indirect
github.com/go-openapi/analysis v0.21.4 // indirect
github.com/go-openapi/errors v0.20.3 // indirect
github.com/go-openapi/jsonpointer v0.19.5 // indirect
Expand Down Expand Up @@ -69,7 +71,7 @@ require (
github.com/inconshreveable/mousetrap v1.0.1 // indirect
github.com/josharian/intern v1.0.0 // indirect
github.com/json-iterator/go v1.1.12 // indirect
github.com/klauspost/compress v1.15.14 // indirect
github.com/klauspost/compress v1.15.15 // indirect
github.com/klauspost/pgzip v1.2.6-0.20220930104621-17e8dac29df8 // indirect
github.com/kr/pretty v0.3.0 // indirect
github.com/kr/text v0.2.0 // indirect
Expand Down Expand Up @@ -99,7 +101,7 @@ require (
github.com/segmentio/ksuid v1.0.4 // indirect
github.com/sigstore/fulcio v1.0.0 // indirect
github.com/sigstore/rekor v1.0.1 // indirect
github.com/sigstore/sigstore v1.5.0 // indirect
github.com/sigstore/sigstore v1.5.1 // indirect
github.com/skratchdot/open-golang v0.0.0-20200116055534-eef842397966 // indirect
github.com/stefanberger/go-pkcs11uri v0.0.0-20201008174630-78d3cae3a980 // indirect
github.com/sylabs/sif/v2 v2.9.0 // indirect
Expand All @@ -125,7 +127,7 @@ require (
golang.org/x/text v0.6.0 // indirect
golang.org/x/tools v0.4.0 // indirect
google.golang.org/appengine v1.6.7 // indirect
google.golang.org/genproto v0.0.0-20221207170731-23e4bf6bdc37 // indirect
google.golang.org/genproto v0.0.0-20221227171554-f9683d7f8bef // indirect
google.golang.org/grpc v1.51.0 // indirect
google.golang.org/protobuf v1.28.1 // indirect
gopkg.in/square/go-jose.v2 v2.6.0 // indirect
Expand Down
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