Add extra group constants and validation to pkg/bootstrap/api.

This adds constants and validation for a new `auth-extra-groups` key on `bootstrap.kubernetes.io/token` secrets. This key allows a bootstrap token to authenticate to extra groups in addition to the `system:bootstrappers` group.

Extra groups are always applied in addition to the `system:bootstrappers` group, must begin with a `system:bootstrappers:` prefix, are limited in length, and are limited to a restricted set of characters (alphanumeric, colons, and dashes without a trailing colon/dash).

pkg/bootstrap/api/helpers_test.go

@@ -0,0 +1,52 @@
+/*
+Copyright 2017 The Kubernetes Authors.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+package api
+
+import (
+	"strings"
+	"testing"
+)
+
+func TestValidateBootstrapGroupName(t *testing.T) {
+	tests := []struct {
+		name  string
+		input string
+		valid bool
+	}{
+		{"valid", "system:bootstrappers:foo", true},
+		{"valid nested", "system:bootstrappers:foo:bar:baz", true},
+		{"valid with dashes and number", "system:bootstrappers:foo-bar-42", true},
+		{"invalid uppercase", "system:bootstrappers:Foo", false},
+		{"missing prefix", "foo", false},
+		{"prefix with no body", "system:bootstrappers:", false},
+		{"invalid spaces", "system:bootstrappers: ", false},
+		{"invalid asterisk", "system:bootstrappers:*", false},
+		{"trailing colon", "system:bootstrappers:foo:", false},
+		{"trailing dash", "system:bootstrappers:foo-", false},
+		{"script tags", "system:bootstrappers:<script> alert(\"scary?!\") </script>", false},
+		{"too long", "system:bootstrappers:" + strings.Repeat("x", 300), false},
+	}
+	for _, test := range tests {
+		err := ValidateBootstrapGroupName(test.input)
+		if err != nil && test.valid {
+			t.Errorf("test %q: ValidateBootstrapGroupName(%q) returned unexpected error: %v", test.name, test.input, err)
+		}
+		if err == nil && !test.valid {
+			t.Errorf("test %q: ValidateBootstrapGroupName(%q) was supposed to return an error but didn't", test.name, test.input)
+		}
+	}
+}