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/BUILD

@@ -3,12 +3,14 @@ package(default_visibility = ["//visibility:public"])
 load(
     "@io_bazel_rules_go//go:def.bzl",
     "go_library",
+    "go_test",
 )
 
 go_library(
     name = "go_default_library",
     srcs = [
         "doc.go",
+        "helpers.go",
         "types.go",
     ],
     deps = ["//vendor/k8s.io/api/core/v1:go_default_library"],
@@ -26,3 +28,9 @@ filegroup(
     srcs = [":package-srcs"],
     tags = ["automanaged"],
 )
+
+go_test(
+    name = "go_default_test",
+    srcs = ["helpers_test.go"],
+    library = ":go_default_library",
+)

pkg/bootstrap/api/helpers.go

@@ -0,0 +1,34 @@
+/*
+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 (
+	"fmt"
+	"regexp"
+)
+
+var bootstrapGroupRegexp = regexp.MustCompile(`\A` + BootstrapGroupPattern + `\z`)
+
+// ValidateBootstrapGroupName checks if the provided group name is a valid
+// bootstrap group name. Returns nil if valid or a validation error if invalid.
+// TODO(mattmoyer): this validation should migrate out to client-go (see https://github.com/kubernetes/client-go/issues/114)
+func ValidateBootstrapGroupName(name string) error {
+	if bootstrapGroupRegexp.Match([]byte(name)) {
+		return nil
+	}
+	return fmt.Errorf("bootstrap group %q is invalid (must match %s)", name, BootstrapGroupPattern)
+}

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)
+		}
+	}
+}

pkg/bootstrap/api/types.go

@@ -51,6 +51,11 @@ const (
 	// describes what the bootstrap token is used for. Optional.
 	BootstrapTokenDescriptionKey = "description"
 
+	// BootstrapTokenExtraGroupsKey is a comma-separated list of group names.
+	// The  bootstrap token will authenticate as these groups in addition to the
+	// "system:bootstrappers" group.
+	BootstrapTokenExtraGroupsKey = "auth-extra-groups"
+
 	// BootstrapTokenUsagePrefix is the prefix for the other usage constants that specifies different
 	// functions of a bootstrap token
 	BootstrapTokenUsagePrefix = "usage-bootstrap-"
@@ -63,7 +68,8 @@ const (
 	// BootstrapTokenUsageAuthentication signals that this token should be used
 	// as a bearer token to authenticate against the Kubernetes API. The bearer
 	// token takes the form "<token-id>.<token-secret>" and authenticates as the
-	// user "system:bootstrap:<token-id>" in the group "system:bootstrappers".
+	// user "system:bootstrap:<token-id>" in the "system:bootstrappers" group
+	// as well as any groups specified using BootstrapTokenExtraGroupsKey.
 	// Value must be "true". Any other value is assumed to be false. Optional.
 	BootstrapTokenUsageAuthentication = "usage-bootstrap-authentication"
 
@@ -80,6 +86,12 @@ const (
 	// authenticate as. The full username given is "system:bootstrap:<token-id>".
 	BootstrapUserPrefix = "system:bootstrap:"
 
-	// BootstrapGroup is the group bootstrapping bearer tokens authenticate in.
-	BootstrapGroup = "system:bootstrappers"
+	// BootstrapGroupPattern is the valid regex pattern that all groups
+	// assigned to a bootstrap token by BootstrapTokenExtraGroupsKey must match.
+	// See also ValidateBootstrapGroupName().
+	BootstrapGroupPattern = "system:bootstrappers:[a-z0-9:-]{0,255}[a-z0-9]"
+
+	// BootstrapDefaultGroup is the default group for bootstrapping bearer
+	// tokens (in addition to any groups from BootstrapTokenExtraGroupsKey).
+	BootstrapDefaultGroup = "system:bootstrappers"
 )

plugin/pkg/auth/authenticator/token/bootstrap/bootstrap.go

@@ -136,7 +136,7 @@ func (t *TokenAuthenticator) AuthenticateToken(token string) (user.Info, bool, e
 
 	return &user.DefaultInfo{
 		Name:   bootstrapapi.BootstrapUserPrefix + string(id),
-		Groups: []string{bootstrapapi.BootstrapGroup},
+		Groups: []string{bootstrapapi.BootstrapDefaultGroup},
 	}, true, nil
 }