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backend.go
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backend.go
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package plugin
import (
"context"
"fmt"
"net/rpc"
"reflect"
"sync"
log "github.com/hashicorp/go-hclog"
"github.com/hashicorp/go-multierror"
"github.com/hashicorp/go-uuid"
v5 "github.com/hashicorp/vault/builtin/plugin/v5"
"github.com/hashicorp/vault/sdk/framework"
"github.com/hashicorp/vault/sdk/helper/consts"
"github.com/hashicorp/vault/sdk/logical"
bplugin "github.com/hashicorp/vault/sdk/plugin"
)
var (
ErrMismatchType = fmt.Errorf("mismatch on mounted backend and plugin backend type")
ErrMismatchPaths = fmt.Errorf("mismatch on mounted backend and plugin backend special paths")
)
// Factory returns a configured plugin logical.Backend.
func Factory(ctx context.Context, conf *logical.BackendConfig) (logical.Backend, error) {
merr := &multierror.Error{}
_, ok := conf.Config["plugin_name"]
if !ok {
return nil, fmt.Errorf("plugin_name not provided")
}
b, err := v5.Backend(ctx, conf)
if err == nil {
if err := b.Setup(ctx, conf); err != nil {
return nil, err
}
return b, nil
}
merr = multierror.Append(merr, err)
b, err = Backend(ctx, conf)
if err != nil {
merr = multierror.Append(merr, err)
return nil, fmt.Errorf("invalid backend version: %s", merr)
}
if err := b.Setup(ctx, conf); err != nil {
merr = multierror.Append(merr, err)
return nil, merr.ErrorOrNil()
}
return b, nil
}
// Backend returns an instance of the backend, either as a plugin if external
// or as a concrete implementation if builtin, casted as logical.Backend.
func Backend(ctx context.Context, conf *logical.BackendConfig) (*PluginBackend, error) {
var b PluginBackend
name := conf.Config["plugin_name"]
pluginType, err := consts.ParsePluginType(conf.Config["plugin_type"])
if err != nil {
return nil, err
}
version := conf.Config["plugin_version"]
sys := conf.System
// NewBackendWithVersion with isMetadataMode set to true
raw, err := bplugin.NewBackendWithVersion(ctx, name, pluginType, sys, conf, true, version)
if err != nil {
return nil, err
}
err = raw.Setup(ctx, conf)
if err != nil {
raw.Cleanup(ctx)
return nil, err
}
// Get SpecialPaths and BackendType
paths := raw.SpecialPaths()
btype := raw.Type()
runningVersion := ""
if versioner, ok := raw.(logical.PluginVersioner); ok {
runningVersion = versioner.PluginVersion().Version
}
external := false
if externaler, ok := raw.(logical.Externaler); ok {
external = externaler.IsExternal()
}
// Cleanup meta plugin backend
raw.Cleanup(ctx)
// Initialize b.Backend with placeholder backend since plugin
// backends will need to be lazy loaded.
b.Backend = &placeholderBackend{
Backend: framework.Backend{
PathsSpecial: paths,
BackendType: btype,
RunningVersion: runningVersion,
},
external: external,
}
b.config = conf
return &b, nil
}
// placeholderBackend is used a placeholder before a backend is lazy-loaded.
// It is mostly used to mark that the backend is an external backend.
type placeholderBackend struct {
framework.Backend
external bool
}
func (p *placeholderBackend) IsExternal() bool {
return p.external
}
var (
_ logical.Externaler = (*placeholderBackend)(nil)
_ logical.PluginVersioner = (*placeholderBackend)(nil)
)
// PluginBackend is a thin wrapper around plugin.BackendPluginClient
type PluginBackend struct {
Backend logical.Backend
sync.RWMutex
config *logical.BackendConfig
// Used to detect if we already reloaded
canary string
// Used to detect if plugin is set
loaded bool
}
// startBackend starts a plugin backend
func (b *PluginBackend) startBackend(ctx context.Context, storage logical.Storage) error {
pluginName := b.config.Config["plugin_name"]
pluginType, err := consts.ParsePluginType(b.config.Config["plugin_type"])
if err != nil {
return err
}
// Ensure proper cleanup of the backend (i.e. call client.Kill())
b.Backend.Cleanup(ctx)
nb, err := bplugin.NewBackendWithVersion(ctx, pluginName, pluginType, b.config.System, b.config, false, b.config.Config["plugin_version"])
if err != nil {
return err
}
err = nb.Setup(ctx, b.config)
if err != nil {
nb.Cleanup(ctx)
return err
}
// If the backend has not been loaded (i.e. still in metadata mode),
// check if type and special paths still matches
if !b.loaded {
if b.Backend.Type() != nb.Type() {
nb.Cleanup(ctx)
b.Backend.Logger().Warn("failed to start plugin process", "plugin", pluginName, "error", ErrMismatchType)
return ErrMismatchType
}
if !reflect.DeepEqual(b.Backend.SpecialPaths(), nb.SpecialPaths()) {
nb.Cleanup(ctx)
b.Backend.Logger().Warn("failed to start plugin process", "plugin", pluginName, "error", ErrMismatchPaths)
return ErrMismatchPaths
}
}
b.Backend = nb
b.loaded = true
// call Initialize() explicitly here.
return b.Backend.Initialize(ctx, &logical.InitializationRequest{
Storage: storage,
})
}
// lazyLoad lazy-loads the backend before running a method
func (b *PluginBackend) lazyLoadBackend(ctx context.Context, storage logical.Storage, methodWrapper func() error) error {
b.RLock()
canary := b.canary
// Lazy-load backend
if !b.loaded {
// Upgrade lock
b.RUnlock()
b.Lock()
// Check once more after lock swap
if !b.loaded {
err := b.startBackend(ctx, storage)
if err != nil {
b.Unlock()
return err
}
}
b.Unlock()
b.RLock()
}
err := methodWrapper()
b.RUnlock()
// Need to compare string value for case were err comes from plugin RPC
// and is returned as plugin.BasicError type.
if err != nil &&
(err.Error() == rpc.ErrShutdown.Error() || err == bplugin.ErrPluginShutdown) {
// Reload plugin if it's an rpc.ErrShutdown
b.Lock()
if b.canary == canary {
b.Backend.Logger().Debug("reloading plugin backend", "plugin", b.config.Config["plugin_name"])
err := b.startBackend(ctx, storage)
if err != nil {
b.Unlock()
return err
}
b.canary, err = uuid.GenerateUUID()
if err != nil {
b.Unlock()
return err
}
}
b.Unlock()
// Try once more
b.RLock()
defer b.RUnlock()
return methodWrapper()
}
return err
}
// HandleRequest is a thin wrapper implementation of HandleRequest that includes
// automatic plugin reload.
func (b *PluginBackend) HandleRequest(ctx context.Context, req *logical.Request) (resp *logical.Response, err error) {
err = b.lazyLoadBackend(ctx, req.Storage, func() error {
var merr error
resp, merr = b.Backend.HandleRequest(ctx, req)
return merr
})
return
}
// HandleExistenceCheck is a thin wrapper implementation of HandleExistenceCheck
// that includes automatic plugin reload.
func (b *PluginBackend) HandleExistenceCheck(ctx context.Context, req *logical.Request) (checkFound bool, exists bool, err error) {
err = b.lazyLoadBackend(ctx, req.Storage, func() error {
var merr error
checkFound, exists, merr = b.Backend.HandleExistenceCheck(ctx, req)
return merr
})
return
}
// Initialize is intentionally a no-op here, the backend will instead be
// initialized when it is lazily loaded.
func (b *PluginBackend) Initialize(ctx context.Context, req *logical.InitializationRequest) error {
return nil
}
// SpecialPaths is a thin wrapper used to ensure we grab the lock for race purposes
func (b *PluginBackend) SpecialPaths() *logical.Paths {
b.RLock()
defer b.RUnlock()
return b.Backend.SpecialPaths()
}
// System is a thin wrapper used to ensure we grab the lock for race purposes
func (b *PluginBackend) System() logical.SystemView {
b.RLock()
defer b.RUnlock()
return b.Backend.System()
}
// Logger is a thin wrapper used to ensure we grab the lock for race purposes
func (b *PluginBackend) Logger() log.Logger {
b.RLock()
defer b.RUnlock()
return b.Backend.Logger()
}
// Cleanup is a thin wrapper used to ensure we grab the lock for race purposes
func (b *PluginBackend) Cleanup(ctx context.Context) {
b.RLock()
defer b.RUnlock()
b.Backend.Cleanup(ctx)
}
// InvalidateKey is a thin wrapper used to ensure we grab the lock for race purposes
func (b *PluginBackend) InvalidateKey(ctx context.Context, key string) {
b.RLock()
defer b.RUnlock()
b.Backend.InvalidateKey(ctx, key)
}
// Setup is a thin wrapper used to ensure we grab the lock for race purposes
func (b *PluginBackend) Setup(ctx context.Context, config *logical.BackendConfig) error {
b.RLock()
defer b.RUnlock()
return b.Backend.Setup(ctx, config)
}
// Type is a thin wrapper used to ensure we grab the lock for race purposes
func (b *PluginBackend) Type() logical.BackendType {
b.RLock()
defer b.RUnlock()
return b.Backend.Type()
}
func (b *PluginBackend) PluginVersion() logical.PluginVersion {
if versioner, ok := b.Backend.(logical.PluginVersioner); ok {
return versioner.PluginVersion()
}
return logical.EmptyPluginVersion
}
func (b *PluginBackend) IsExternal() bool {
if externaler, ok := b.Backend.(logical.Externaler); ok {
return externaler.IsExternal()
}
return false
}
var (
_ logical.PluginVersioner = (*PluginBackend)(nil)
_ logical.Externaler = (*PluginBackend)(nil)
)