Add privacy statement for PII storage

This statement has been added just before the OIDC code/normal flow,
since only in this flow we expect a user to be present. For the device
flow or when a token is provided, it's likely that Cosign is being run
in an automated environment.

This requires the user either type Y or provide a global flag for
confirmation. This should not break any existing flows in automated
environments because it's only the flow when a browser is needed, not
for the device flow or when a token is provided.

Signed-off-by: Hayden Blauzvern <hblauzvern@google.com>

wip

cmd/cosign/cli/commands.go

@@ -26,6 +26,7 @@ import (
 
 	cranecmd "github.com/google/go-containerregistry/cmd/crane/cmd"
 	"github.com/sigstore/cosign/cmd/cosign/cli/options"
+	"github.com/sigstore/cosign/pkg/cosign"
 )
 
 var (
@@ -73,6 +74,11 @@ func New() *cobra.Command {
 			if ro.Verbose {
 				logs.Debug.SetOutput(os.Stderr)
 			}
+
+			if ro.Confirmation {
+				cosign.SetConfirmation(ro.Confirmation)
+			}
+
 			return nil
 		},
 		PersistentPostRun: func(cmd *cobra.Command, args []string) {

cmd/cosign/cli/fulcio/fulcio.go

@@ -22,6 +22,7 @@ import (
 	"crypto/rand"
 	"crypto/sha256"
 	"crypto/x509"
+	"errors"
 	"fmt"
 	"net/url"
 	"os"
@@ -41,6 +42,12 @@ const (
 	FlowNormal = "normal"
 	FlowDevice = "device"
 	FlowToken  = "token"
+	// spacing is intentional to have this indented
+	PrivacyStatement = `
+        Note that there may be personally identifiable information associated with this signed artifact.
+        This may include the email address associated with the account with which you authenticate.
+        This information will be used for signing this artifact and will be stored in public transparency logs and cannot be removed later.
+        By typing 'Y', you attest that you grant (or have permission to grant) and agree to have this information stored permanently in transparency logs.`
 )
 
 type oidcConnector interface {
@@ -92,6 +99,14 @@ func GetCert(ctx context.Context, priv *ecdsa.PrivateKey, idToken, flow, oidcIss
 		c.flow = oauthflow.NewDeviceFlowTokenGetter(
 			oidcIssuer, oauthflow.SigstoreDeviceURL, oauthflow.SigstoreTokenURL)
 	case FlowNormal:
+		fmt.Fprintln(os.Stderr, PrivacyStatement)
+		ok, err := cosign.ConfirmPrompt("")
+		if err != nil {
+			return nil, err
+		}
+		if !ok {
+			return nil, errors.New("no confirmation")
+		}
 		c.flow = oauthflow.DefaultIDTokenGetter
 	case FlowToken:
 		c.flow = &oauthflow.StaticTokenGetter{RawToken: idToken}

cmd/cosign/cli/options/root.go

@@ -23,9 +23,10 @@ import (
 
 // RootOptions define flags and options for the root cosign cli.
 type RootOptions struct {
-	OutputFile string
-	Verbose    bool
-	Timeout    time.Duration
+	OutputFile   string
+	Verbose      bool
+	Timeout      time.Duration
+	Confirmation bool
 }
 
 // DefaultTimeout specifies the default timeout for commands.
@@ -43,4 +44,7 @@ func (o *RootOptions) AddFlags(cmd *cobra.Command) {
 
 	cmd.PersistentFlags().DurationVarP(&o.Timeout, "timeout", "t", DefaultTimeout,
 		"timeout for commands")
+
+	cmd.PersistentFlags().BoolVarP(&o.Confirmation, "yes", "y", false,
+		"skip confirmation prompts")
 }

pkg/cosign/common.go

@@ -26,6 +26,14 @@ import (
 	"golang.org/x/term"
 )
 
+// confirmation is a global variable to store whether or not the user has provided
+// the --yes flag to skip all confirmation prompts
+var confirmation bool
+
+func SetConfirmation(confirm bool) {
+	confirmation = confirm
+}
+
 // TODO need to centralize this logic
 func FileExists(filename string) bool {
 	info, err := os.Stat(filename)
@@ -36,6 +44,10 @@ func FileExists(filename string) bool {
 }
 
 func ConfirmPrompt(msg string) (bool, error) {
+	if confirmation {
+		return confirmation, nil
+	}
+
 	fmt.Fprintf(os.Stderr, "%s\n\nAre you sure you want to continue? [Y/n]: ", msg)
 	reader := bufio.NewReader(os.Stdin)
 	r, err := reader.ReadString('\n')