Fix handling of devices

Devices are supposed to be able to be passed in via the form of

--device /dev/foo
--device /dev/foo:/dev/bar
--device /dev/foo:rwm
--device /dev/foo:/dev/bar:rwm

Signed-off-by: Daniel J Walsh <dwalsh@redhat.com>

Closes: #1299
Approved by: umohnani8

pkg/spec/parse.go

@@ -126,3 +126,58 @@ func getLoggingPath(opts []string) string {
 	}
 	return ""
 }
+
+// parseDevice parses device mapping string to a src, dest & permissions string
+func parseDevice(device string) (string, string, string, error) { //nolint
+	src := ""
+	dst := ""
+	permissions := "rwm"
+	arr := strings.Split(device, ":")
+	switch len(arr) {
+	case 3:
+		if !validDeviceMode(arr[2]) {
+			return "", "", "", fmt.Errorf("invalid device mode: %s", arr[2])
+		}
+		permissions = arr[2]
+		fallthrough
+	case 2:
+		if validDeviceMode(arr[1]) {
+			permissions = arr[1]
+		} else {
+			if arr[1][0] != '/' {
+				return "", "", "", fmt.Errorf("invalid device mode: %s", arr[2])
+			}
+			dst = arr[1]
+		}
+		fallthrough
+	case 1:
+		src = arr[0]
+	default:
+		return "", "", "", fmt.Errorf("invalid device specification: %s", device)
+	}
+
+	if dst == "" {
+		dst = src
+	}
+	return src, dst, permissions, nil
+}
+
+// validDeviceMode checks if the mode for device is valid or not.
+// Valid mode is a composition of r (read), w (write), and m (mknod).
+func validDeviceMode(mode string) bool {
+	var legalDeviceMode = map[rune]bool{
+		'r': true,
+		'w': true,
+		'm': true,
+	}
+	if mode == "" {
+		return false
+	}
+	for _, c := range mode {
+		if !legalDeviceMode[c] {
+			return false
+		}
+		legalDeviceMode[c] = false
+	}
+	return true
+}