1 files changed, 36 insertions, 0 deletions
diff --git a/cmd/podman/common/sign.go b/cmd/podman/common/sign.go
new file mode 100644
index 000000000..e8a90ed57
--- /dev/null
+++ b/cmd/podman/common/sign.go
@@ -0,0 +1,36 @@
+package common
+
+import (
+	"fmt"
+
+	"github.com/containers/image/v5/pkg/cli"
+	"github.com/containers/podman/v4/pkg/domain/entities"
+	"github.com/containers/podman/v4/pkg/terminal"
+)
+
+// PrepareSigningPassphrase updates pushOpts.SignPassphrase and SignSigstorePrivateKeyPassphrase based on a --sign-passphrase-file value signPassphraseFile,
+// and validates pushOpts.Sign* consistency.
+// It may interactively prompt for a passphrase if one is required and wasn’t provided otherwise.
+func PrepareSigningPassphrase(pushOpts *entities.ImagePushOptions, signPassphraseFile string) error {
+	// c/common/libimage.Image does allow creating both simple signing and sigstore signatures simultaneously,
+	// with independent passphrases, but that would make the CLI probably too confusing.
+	// For now, use the passphrase with either, but only one of them.
+	if signPassphraseFile != "" && pushOpts.SignBy != "" && pushOpts.SignBySigstorePrivateKeyFile != "" {
+		return fmt.Errorf("only one of --sign-by and sign-by-sigstore-private-key can be used with --sign-passphrase-file")
+	}
+
+	var passphrase string
+	if signPassphraseFile != "" {
+		p, err := cli.ReadPassphraseFile(signPassphraseFile)
+		if err != nil {
+			return err
+		}
+		passphrase = p
+	} else if pushOpts.SignBySigstorePrivateKeyFile != "" {
+		p := terminal.ReadPassphrase()
+		passphrase = string(p)
+	} // pushOpts.SignBy triggers a GPG-agent passphrase prompt, possibly using a more secure channel, so we usually shouldn’t prompt ourselves if no passphrase was explicitly provided.
+	pushOpts.SignPassphrase = passphrase
+	pushOpts.SignSigstorePrivateKeyPassphrase = []byte(passphrase)
+	return nil
+}