diff --git a/unum/vendor/github.com/docker/libtrust/filter.go b/unum/vendor/github.com/docker/libtrust/filter.go
new file mode 100644
index 0000000..5b2b4fc
--- /dev/null
+++ b/unum/vendor/github.com/docker/libtrust/filter.go
@@ -0,0 +1,50 @@
+package libtrust
+
+import (
+	"path/filepath"
+)
+
+// FilterByHosts filters the list of PublicKeys to only those which contain a
+// 'hosts' pattern which matches the given host. If *includeEmpty* is true,
+// then keys which do not specify any hosts are also returned.
+func FilterByHosts(keys []PublicKey, host string, includeEmpty bool) ([]PublicKey, error) {
+	filtered := make([]PublicKey, 0, len(keys))
+
+	for _, pubKey := range keys {
+		var hosts []string
+		switch v := pubKey.GetExtendedField("hosts").(type) {
+		case []string:
+			hosts = v
+		case []interface{}:
+			for _, value := range v {
+				h, ok := value.(string)
+				if !ok {
+					continue
+				}
+				hosts = append(hosts, h)
+			}
+		}
+
+		if len(hosts) == 0 {
+			if includeEmpty {
+				filtered = append(filtered, pubKey)
+			}
+			continue
+		}
+
+		// Check if any hosts match pattern
+		for _, hostPattern := range hosts {
+			match, err := filepath.Match(hostPattern, host)
+			if err != nil {
+				return nil, err
+			}
+
+			if match {
+				filtered = append(filtered, pubKey)
+				continue
+			}
+		}
+	}
+
+	return filtered, nil
+}