Implemented image encryption/decryption libraries and ctr commands

Signed-off-by: Stefan Berger <stefanb@linux.ibm.com>
Signed-off-by: Brandon Lum <lumjjb@gmail.com>

cmd/ctr/commands/commands.go

@@ -127,6 +127,22 @@ var (
 			Usage: "memory limit (in bytes) for the container",
 		},
 	}
+	// ImageDecryptionFlags are cli flags needed when decrypting an image
+	ImageDecryptionFlags = []cli.Flag{
+		cli.StringFlag{
+			Name:  "gpg-homedir",
+			Usage: "The GPG homedir to use; by default gpg uses ~/.gnupg",
+		}, cli.StringFlag{
+			Name:  "gpg-version",
+			Usage: "The GPG version (\"v1\" or \"v2\"), default will make an educated guess",
+		}, cli.StringSliceFlag{
+			Name:  "key",
+			Usage: "A secret key's filename and an optional password separated by colon; this option may be provided multiple times",
+		}, cli.StringSliceFlag{
+			Name:  "dec-recipient",
+			Usage: "Recipient of the image; used only for PKCS7 and must be an x509 certificate",
+		},
+	}
 )
 
 // ObjectWithLabelArgs returns the first arg and a LabelArgs object