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gcpsecretmanager.go
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gcpsecretmanager.go
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// Copyright 2020 The Go Cloud Development Kit 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
//
// 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 gcpsecretmanager provides a runtimevar implementation with
// secrets read from GCP Secret Manager
// (https://cloud.google.com/secret-manager).
// Use OpenVariable to construct a *runtimevar.Variable.
//
// # URLs
//
// For runtimevar.OpenVariable, gcpsecretmanager registers for the scheme
// "gcpsecretmanager".
// The default URL opener will creating a connection using use default
// credentials from the environment, as described in
// https://cloud.google.com/docs/authentication/production.
// To customize the URL opener, or for more details on the URL format,
// see URLOpener.
// See https://gocloud.dev/concepts/urls/ for background information.
//
// # As
//
// gcpsecretmanager exposes the following types for As:
// - Snapshot: *secretmanagerpb.AccessSecretVersionResponse
// - Error: *status.Status
package gcpsecretmanager // import "gocloud.dev/runtimevar/gcpsecretmanager"
import (
"bytes"
"context"
"errors"
"fmt"
"net/url"
"path"
"regexp"
"sync"
"time"
secretmanager "cloud.google.com/go/secretmanager/apiv1"
"github.com/google/wire"
"gocloud.dev/gcerrors"
"gocloud.dev/gcp"
"gocloud.dev/internal/gcerr"
"gocloud.dev/runtimevar"
"gocloud.dev/runtimevar/driver"
"google.golang.org/api/option"
secretmanagerpb "google.golang.org/genproto/googleapis/cloud/secretmanager/v1"
"google.golang.org/grpc"
"google.golang.org/grpc/codes"
"google.golang.org/grpc/credentials"
"google.golang.org/grpc/credentials/oauth"
"google.golang.org/grpc/status"
)
// Dial opens a gRPC connection to the Secret Manager API using
// credentials from ts. It is provided as an optional helper with useful
// defaults.
//
// The second return value is a function that should be called to clean up
// the connection opened by Dial.
func Dial(ctx context.Context, ts gcp.TokenSource) (*secretmanager.Client, func(), error) {
client, err := secretmanager.NewClient(ctx,
option.WithGRPCDialOption(
grpc.WithTransportCredentials(credentials.NewClientTLSFromCert(nil, "")),
),
option.WithTokenSource(oauth.TokenSource{TokenSource: ts}),
option.WithUserAgent("runtimevar"),
)
if err != nil {
return nil, nil, err
}
return client, func() { _ = client.Close() }, nil
}
func init() {
runtimevar.DefaultURLMux().RegisterVariable(Scheme, new(lazyCredsOpener))
}
// Set holds Wire providers for this package.
var Set = wire.NewSet(
Dial,
wire.Struct(new(URLOpener), "Client"),
)
// lazyCredsOpener obtains Application Default Credentials on the first call
// to OpenVariableURL.
type lazyCredsOpener struct {
init sync.Once
opener *URLOpener
err error
}
func (o *lazyCredsOpener) OpenVariableURL(ctx context.Context, u *url.URL) (*runtimevar.Variable, error) {
o.init.Do(func() {
creds, err := gcp.DefaultCredentials(ctx)
if err != nil {
o.err = err
return
}
client, _, err := Dial(ctx, creds.TokenSource)
if err != nil {
o.err = err
return
}
o.opener = &URLOpener{Client: client}
})
if o.err != nil {
return nil, fmt.Errorf("open variable %v: %v", u, o.err)
}
return o.opener.OpenVariableURL(ctx, u)
}
// Scheme is the URL scheme gcpsecretmanager registers its URLOpener under on runtimevar.DefaultMux.
const Scheme = "gcpsecretmanager"
// URLOpener opens gcpsecretmanager URLs like "gcpsecretmanager://projects/[project_id]/secrets/[secret_id]".
//
// The URL Host+Path are used as the GCP Secret Manager secret key;
// see https://cloud.google.com/secret-manager
// for more details.
//
// The following query parameters are supported:
//
// - decoder: The decoder to use. Defaults to URLOpener.Decoder, or
// runtimevar.BytesDecoder if URLOpener.Decoder is nil.
// See runtimevar.DecoderByName for supported values.
// - wait: The poll interval, in time.ParseDuration formats.
// Defaults to 30s.
type URLOpener struct {
// Client must be set to a non-nil client authenticated with
// Secret Manager scope or equivalent.
Client *secretmanager.Client
// Decoder specifies the decoder to use if one is not specified in the URL.
// Defaults to runtimevar.BytesDecoder.
Decoder *runtimevar.Decoder
// Options specifies the options to pass to New.
Options Options
}
// OpenVariableURL opens a gcpsecretmanager Secret.
func (o *URLOpener) OpenVariableURL(ctx context.Context, u *url.URL) (*runtimevar.Variable, error) {
q := u.Query()
decoderName := q.Get("decoder")
q.Del("decoder")
decoder, err := runtimevar.DecoderByName(ctx, decoderName, o.Decoder)
if err != nil {
return nil, fmt.Errorf("open variable %v: invalid decoder: %v", u, err)
}
opts := o.Options
if s := q.Get("wait"); s != "" {
q.Del("wait")
d, err := time.ParseDuration(s)
if err != nil {
return nil, fmt.Errorf("open variable %v: invalid wait %q: %v", u, s, err)
}
opts.WaitDuration = d
}
for param := range q {
return nil, fmt.Errorf("open variable %v: invalid query parameter %q", u, param)
}
return OpenVariable(o.Client, path.Join(u.Host, u.Path), decoder, &opts)
}
// Options sets options.
type Options struct {
// WaitDuration controls the rate at which Secret Manager is polled.
// Defaults to 30 seconds.
WaitDuration time.Duration
}
// OpenVariable constructs a *runtimevar.Variable backed by secretKey in GCP Secret Manager.
//
// A secretKey will look like:
//
// projects/[project_id]/secrets/[secret_id]
//
// A project ID is a unique, user-assigned ID of the Project.
// It must be 6 to 30 lowercase letters, digits, or hyphens.
// It must start with a letter. Trailing hyphens are prohibited.
//
// A secret ID is a string with a maximum length of 255 characters and can
// contain uppercase and lowercase letters, numerals, and the hyphen (`-`) and
// underscore (`_`) characters.
//
// gcpsecretmanager package will always use the latest secret value,
// so `/version/latest` postfix must NOT be added to the secret key.
//
// You can use the full string (e.g., copied from the GCP Console), or
// construct one from its parts using SecretKey.
//
// See https://cloud.google.com/secret-manager for more details.
//
// Secret Manager returns raw bytes; provide a decoder to decode the raw bytes
// into the appropriate type for runtimevar.Snapshot.Value.
// See the runtimevar package documentation for examples of decoders.
func OpenVariable(client *secretmanager.Client, secretKey string, decoder *runtimevar.Decoder, opts *Options) (*runtimevar.Variable, error) {
w, err := newWatcher(client, secretKey, decoder, opts)
if err != nil {
return nil, err
}
return runtimevar.New(w), nil
}
var secretKeyRE = regexp.MustCompile("^projects/[a-z][a-z0-9_\\-]{4,28}[a-z0-9_]/secrets/[a-zA-Z0-9_\\-]{1,255}$")
const latestVersion = "/versions/latest"
func newWatcher(client *secretmanager.Client, secretKey string, decoder *runtimevar.Decoder, opts *Options) (driver.Watcher, error) {
if opts == nil {
opts = &Options{}
}
if !secretKeyRE.MatchString(secretKey) {
return nil, fmt.Errorf("invalid secretKey %q; must match %v", secretKey, secretKeyRE)
}
return &watcher{
client: client,
wait: driver.WaitDuration(opts.WaitDuration),
name: secretKey,
decoder: decoder,
}, nil
}
// SecretKey constructs a GCP Secret Manager secret key from component parts.
// See https://cloud.google.com/secret-manager for more details.
func SecretKey(projectID gcp.ProjectID, secretID string) string {
return "projects/" + string(projectID) + "/secrets/" + secretID
}
// state implements driver.State.
type state struct {
val interface{}
raw *secretmanagerpb.AccessSecretVersionResponse
updateTime time.Time
rawBytes []byte
err error
}
// Value implements driver.State.Value.
func (s *state) Value() (interface{}, error) {
return s.val, s.err
}
// UpdateTime implements driver.State.UpdateTime.
func (s *state) UpdateTime() time.Time {
return s.updateTime
}
// As implements driver.State.As.
func (s *state) As(i interface{}) bool {
if s.raw == nil {
return false
}
p, ok := i.(**secretmanagerpb.AccessSecretVersionResponse)
if !ok {
return false
}
*p = s.raw
return true
}
// errorState returns a new State with err, unless prevS also represents
// the same error, in which case it returns nil.
func errorState(err error, prevS driver.State) driver.State {
s := &state{err: err}
if prevS == nil {
return s
}
prev := prevS.(*state)
if prev.err == nil {
// New error.
return s
}
if equivalentError(err, prev.err) {
// Same error, return nil to indicate no change.
return nil
}
return s
}
// equivalentError returns true iff err1 and err2 represent an equivalent error;
// i.e., we don't want to return it to the user as a different error.
func equivalentError(err1, err2 error) bool {
if err1 == err2 || err1.Error() == err2.Error() {
return true
}
code1, code2 := status.Code(err1), status.Code(err2)
return code1 != codes.OK && code1 != codes.Unknown && code1 == code2
}
// watcher implements driver.Watcher for secrets provided by the Secret Manager service.
type watcher struct {
client *secretmanager.Client
wait time.Duration
name string
decoder *runtimevar.Decoder
}
// WatchVariable implements driver.WatchVariable.
func (w *watcher) WatchVariable(ctx context.Context, prev driver.State) (driver.State, time.Duration) {
latest := w.name + latestVersion
secret, err := w.client.AccessSecretVersion(ctx, &secretmanagerpb.AccessSecretVersionRequest{Name: latest})
if err != nil {
return errorState(err, prev), w.wait
}
if secret == nil || secret.Payload == nil || secret.Payload.Data == nil {
return errorState(errors.New("invalid secret payload"), prev), w.wait
}
meta, err := w.client.GetSecretVersion(ctx, &secretmanagerpb.GetSecretVersionRequest{Name: latest})
if err != nil {
return errorState(err, prev), w.wait
}
createTime := meta.CreateTime.AsTime()
// See if it's the same raw bytes as before.
if prev != nil {
prevState, ok := prev.(*state)
if ok && prevState != nil && bytes.Equal(secret.Payload.Data, prevState.rawBytes) {
// No change!
return nil, w.wait
}
}
// Decode the value.
val, err := w.decoder.Decode(ctx, secret.Payload.Data)
if err != nil {
return errorState(err, prev), w.wait
}
// A secret version is immutable.
// The latest secret value creation time is the last time the secret value has been changed.
// Hence set updateTime as createTime.
return &state{val: val, raw: secret, updateTime: createTime, rawBytes: secret.Payload.Data}, w.wait
}
// Close implements driver.Close.
func (w *watcher) Close() error {
return nil
}
// ErrorAs implements driver.ErrorAs.
func (w *watcher) ErrorAs(err error, i interface{}) bool {
// FromError converts err to a *status.Status.
s, _ := status.FromError(err)
if p, ok := i.(**status.Status); ok {
*p = s
return true
}
return false
}
// ErrorCode implements driver.ErrorCode.
func (*watcher) ErrorCode(err error) gcerrors.ErrorCode {
return gcerr.GRPCCode(err)
}