plugin/http_client.go

// Copyright 2018 Google LLC
//
// 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
//
// https://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 plugin

import (
	"context"
	"fmt"
	"io"
	"net/http"
	"os"

	"github.com/golang/glog"

	"golang.org/x/oauth2"
	"golang.org/x/oauth2/google"

	"google.golang.org/api/cloudkms/v1"

	"gopkg.in/gcfg.v1"
)

// tokenConfig represents attributes found in gce.conf - only attributes of the interest of this plugin are listed.
type tokenConfig struct {
	Global struct {
		TokenURL  string `gcfg:"token-url"`
		TokenBody string `gcfg:"token-body"`
	}
}

func NewHTTPClient(ctx context.Context, pathToGCEConf string) (*http.Client, error) {
	if pathToGCEConf != "" {
		r, err := os.Open(pathToGCEConf)
		if err != nil {
			return nil, fmt.Errorf("failed to open GCE Config: %s", pathToGCEConf)
		}
		defer r.Close()

		c, err := readConfig(r)
		if err != nil {
			return nil, err
		}

		if (tokenConfig{} == *c) {
			glog.Infof("Since TokenConfig contains neither TokenURI nor TokenBody assuming that running on GCE (ex. via kube-up.sh)")
			return getDefaultClient(ctx)
		}

		// Running on GKE Hosted Master
		glog.Infof("TokenURI:%s, TokenBody:%s - assuming that running on a Hosted Master - GKE.", c.Global.TokenURL, c.Global.TokenBody)
		a := newAltTokenSource(ctx, c.Global.TokenURL, c.Global.TokenBody)

		// TODO: Do I need to call a.Token to get access token here?
		if _, err := a.Token(); err != nil {
			glog.Errorf("error fetching initial token: %v", err)
			return nil, err
		}

		return oauth2.NewClient(ctx, a), nil
	}

	glog.Infof("Path to gce.conf was not supplied - assuming that need to rely on exported service account key.")
	return getDefaultClient(ctx)
}

func readConfig(reader io.Reader) (*tokenConfig, error) {
	cfg := &tokenConfig{}
	if err := gcfg.FatalOnly(gcfg.ReadInto(cfg, reader)); err != nil {
		glog.Errorf("Couldn't read GCE Config: %v", err)
		return nil, err
	}
	return cfg, nil
}

func getDefaultClient(ctx context.Context) (*http.Client, error) {
	client, err := google.DefaultClient(ctx, cloudkms.CloudPlatformScope)
	if err != nil {
		return nil, fmt.Errorf("failed to instantiate cloud sdk client: %v", err)
	}
	return client, nil
}