add support for recording creation timestamp for cosign attest

Signed-off-by: Zsolt Horvath <zsolte@gmail.com>
Signed-off-by: Zsolt Horvath <zsolt.horvath@real-digital.de>

Author: Zsolt Horvath

cmd/cosign/cli/attest.go

@@ -31,7 +31,7 @@ func Attest() *cobra.Command {
 	cmd := &cobra.Command{
 		Use:   "attest",
 		Short: "Attest the supplied container image.",
-		Example: `  cosign attest --key <key path>|<kms uri> [--predicate <path>] [--a key=value] [--no-upload=true|false] [--f] [--r] <image uri>
+		Example: `  cosign attest --key <key path>|<kms uri> [--predicate <path>] [--a key=value] [--no-upload=true|false] [--record-creation-timestamp=true|false] [--f] [--r] <image uri>
 
   # attach an attestation to a container image Google sign-in
   cosign attest --timeout 90s --predicate <FILE> --type <TYPE> <IMAGE>
@@ -58,7 +58,10 @@ func Attest() *cobra.Command {
   COSIGN_DOCKER_MEDIA_TYPES=1 cosign attest --predicate <FILE> --type <TYPE> --key cosign.key legacy-registry.example.com/my/image
 
   # supply attestation via stdin
-  echo <PAYLOAD> | cosign attest --predicate - <IMAGE>`,
+  echo <PAYLOAD> | cosign attest --predicate - <IMAGE>
+
+  # attach an attestation to a container image and honor the creation timestamp of the signature
+  cosign attest --predicate <FILE> --type <TYPE> --key cosign.key --record-creation-timestamp <IMAGE>`,
 
 		Args:             cobra.MinimumNArgs(1),
 		PersistentPreRun: options.BindViper,
@@ -86,17 +89,18 @@ func Attest() *cobra.Command {
 				TSAServerURL:             o.TSAServerURL,
 			}
 			attestCommand := attest.AttestCommand{
-				KeyOpts:         ko,
-				RegistryOptions: o.Registry,
-				CertPath:        o.Cert,
-				CertChainPath:   o.CertChain,
-				NoUpload:        o.NoUpload,
-				PredicatePath:   o.Predicate.Path,
-				PredicateType:   o.Predicate.Type,
-				Replace:         o.Replace,
-				Timeout:         ro.Timeout,
-				TlogUpload:      o.TlogUpload,
-				RekorEntryType:  o.RekorEntryType,
+				KeyOpts:                 ko,
+				RegistryOptions:         o.Registry,
+				CertPath:                o.Cert,
+				CertChainPath:           o.CertChain,
+				NoUpload:                o.NoUpload,
+				PredicatePath:           o.Predicate.Path,
+				PredicateType:           o.Predicate.Type,
+				Replace:                 o.Replace,
+				Timeout:                 ro.Timeout,
+				TlogUpload:              o.TlogUpload,
+				RekorEntryType:          o.RekorEntryType,
+				RecordCreationTimestamp: o.RecordCreationTimestamp,
 			}
 
 			for _, img := range args {

cmd/cosign/cli/attest/attest.go

@@ -71,16 +71,17 @@ func uploadToTlog(ctx context.Context, sv *sign.SignerVerifier, rekorURL string,
 type AttestCommand struct {
 	options.KeyOpts
 	options.RegistryOptions
-	CertPath       string
-	CertChainPath  string
-	NoUpload       bool
-	PredicatePath  string
-	PredicateType  string
-	Replace        bool
-	Timeout        time.Duration
-	TlogUpload     bool
-	TSAServerURL   string
-	RekorEntryType string
+	CertPath                string
+	CertChainPath           string
+	NoUpload                bool
+	PredicatePath           string
+	PredicateType           string
+	Replace                 bool
+	Timeout                 time.Duration
+	TlogUpload              bool
+	TSAServerURL            string
+	RekorEntryType          string
+	RecordCreationTimestamp bool
 }
 
 // nolint
@@ -226,6 +227,7 @@ func (c *AttestCommand) Exec(ctx context.Context, imageRef string) error {
 
 	signOpts := []mutate.SignOption{
 		mutate.WithDupeDetector(dd),
+		mutate.WithRecordCreationTimestamp(c.RecordCreationTimestamp),
 	}
 
 	if c.Replace {

cmd/cosign/cli/options/attest.go

@@ -21,16 +21,17 @@ import (
 
 // AttestOptions is the top level wrapper for the attest command.
 type AttestOptions struct {
-	Key              string
-	Cert             string
-	CertChain        string
-	NoUpload         bool
-	Recursive        bool
-	Replace          bool
-	SkipConfirmation bool
-	TlogUpload       bool
-	TSAServerURL     string
-	RekorEntryType   string
+	Key                     string
+	Cert                    string
+	CertChain               string
+	NoUpload                bool
+	Recursive               bool
+	Replace                 bool
+	SkipConfirmation        bool
+	TlogUpload              bool
+	TSAServerURL            string
+	RekorEntryType          string
+	RecordCreationTimestamp bool
 
 	Rekor       RekorOptions
 	Fulcio      FulcioOptions
@@ -86,4 +87,7 @@ func (o *AttestOptions) AddFlags(cmd *cobra.Command) {
 
 	cmd.Flags().StringVar(&o.TSAServerURL, "timestamp-server-url", "",
 		"url to the Timestamp RFC3161 server, default none. Must be the path to the API to request timestamp responses, e.g. https://freetsa.org/tsr")
+
+	cmd.Flags().BoolVar(&o.RecordCreationTimestamp, "record-creation-timestamp", false,
+		"set the createdAt timestamp in the attestation artifact to the time it was created; by default, cosign sets this to the zero value")
 }