secrets

Documentation

Overview

Package secrets provides an interface for a simple secret store: you ask it for a secret (a byte blob, identifies by some key), and it returns it to you (current version, as well as a bunch of previous versions). Caller are supposed to use the secret for an operation and then forget it (e.g. do not try to store it elsewhere).

Secure storage, retrieval and rotation of secrets is outside of the scope of this interface: it's the responsibility of the implementation.

Index

• Variables
• func NewModule(opts *ModuleOptions) module.Module
• func NewModuleFromFlags() module.Module
• func Set(c context.Context, s Store) context.Context
• func SetFactory(c context.Context, f Factory) context.Context
• type DerivedStore
  • func NewDerivedStore(root Secret) *DerivedStore
  • func (d *DerivedStore) GetSecret(name string) (Secret, error)
  • func (d *DerivedStore) SetRoot(root Secret)
• type Factory
• type FileSource
  • func (s *FileSource) Close() error
  • func (s *FileSource) ReadSecret(context.Context) (*Secret, error)
• type ModuleOptions
  • func (o *ModuleOptions) Register(f *flag.FlagSet)
• type Secret
  • func GetSecret(c context.Context, key string) (Secret, error)
  • func (s Secret) Blobs() [][]byte
  • func (s Secret) Equal(a Secret) bool
• type SecretManagerSource
  • func NewSecretManagerSource(ctx context.Context, secretURL string, ts oauth2.TokenSource) (*SecretManagerSource, error)
  • func (s *SecretManagerSource) Close() error
  • func (s *SecretManagerSource) ReadSecret(ctx context.Context) (*Secret, error)
• type Source
• type StaticSource
  • func (s *StaticSource) Close() error
  • func (s *StaticSource) ReadSecret(context.Context) (*Secret, error)
• type StaticStore
  • func (s StaticStore) GetSecret(k string) (Secret, error)
• type Store
  • func Get(c context.Context) Store

Variables

var (
	// ErrNoStoreConfigured is returned by GetSecret if secret store is not in
	// the context.
	ErrNoStoreConfigured = errors.New("secrets.Store is not in the context")
)

var (
	// ErrNoSuchSecret is returned by Store.GetSecret if it can't find a secret.
	ErrNoSuchSecret = errors.New("secret not found")
)

Functions

func NewModule

func NewModule(opts *ModuleOptions) module.Module

NewModule returns a server module that adds a secret store to the global server context.

Uses a DerivedStore with the root secret populated based on the supplied options. When the server starts, the module reads the initial root secret (if provided) and launches a job to periodically reread it.

An error to read the secret during the startup is fatal. But if the server managed to start successfully and can't re-read the secret later (e.g. the file disappeared), it logs the error and keeps using the cached secret.

func NewModuleFromFlags

func NewModuleFromFlags() module.Module

NewModuleFromFlags is a variant of NewModule that initializes options through command line flags.

Calling this function registers flags in flag.CommandLine. They are usually parsed in server.Main(...).

func Set

func Set(c context.Context, s Store) context.Context

Set injects the Store object in the context to be returned by Get as is.

func SetFactory

func SetFactory(c context.Context, f Factory) context.Context

SetFactory sets the function to produce Store instances when Get(c) is used.

Types

type DerivedStore

type DerivedStore struct {
	// contains filtered or unexported fields
}

DerivedStore implements Store by deriving secrets from some single master secret using HKDF.

Caches all derived secrets internally forever. Assumes the set of possible key names is limited.

func NewDerivedStore

func NewDerivedStore(root Secret) *DerivedStore

NewDerivedStore returns a store that derives secrets from the given root key.

func (*DerivedStore) GetSecret

func (d *DerivedStore) GetSecret(name string) (Secret, error)

GetSecret returns a generated secret given its key.

func (*DerivedStore) SetRoot

func (d *DerivedStore) SetRoot(root Secret)

SetRoot replaces the root key used to derive secrets.

type Factory

type Factory func(context.Context) Store

Factory knows how to make a new Store.

type FileSource

type FileSource struct {
	Path string
}

FileSource reads the secret from a JSON file on disk.

func (*FileSource) Close

func (s *FileSource) Close() error

Close is part of Source interface.

func (*FileSource) ReadSecret

func (s *FileSource) ReadSecret(context.Context) (*Secret, error)

ReadSecret is part of Source interface.

type ModuleOptions

type ModuleOptions struct {
	// RootSecret points to the root secret key used to derive all other secrets.
	//
	// It can be either a local file system path, a reference to a Google Secret
	// Manager secret (in a form "sm://<project>/<secret>"), or a literal secret
	// value (in a form "devsecret://<base64-encoded secret>"). The latter is
	// supposed to be used **only** during development (e.g. locally or in
	// development deployments).
	//
	// When it is a local file system path, it should point to a JSON file with
	// the following structure (see Secret struct):
	//
	//   {
	//     "current": <base64-encoded blob>,
	//     "previous": [<base64-encoded blob>, <base64-encoded blob>, ...]
	//   }
	//
	// When using Google Secret Manager, the secret version "latest" is used to
	// get the current value of the secret, and a single immediately preceding
	// previous version (if it is still enabled) is used to get the previous
	// version of the secret. This allows graceful rotation of secrets.
	RootSecret string

	// Source produces the root secret to use by the module.
	//
	// If given, overrides RootSecret. This is useful when the secrets module
	// is initialized programmatically rather than through flags.
	//
	// The module will periodically use Source's ReadSecret to refresh the root
	// secret it stores in memory. This allows the secret to be rotated without
	// restarting all servers that use it.
	Source Source
}

ModuleOptions contain configuration of the secrets server module.

func (*ModuleOptions) Register

func (o *ModuleOptions) Register(f *flag.FlagSet)

Register registers the command line flags.

type Secret

type Secret struct {
	Current  []byte   `json:"current"`            // current value of the secret, always set
	Previous [][]byte `json:"previous,omitempty"` // optional list of previous values, most recent first
}

Secret represents a current value of a secret as well as a set of few previous values. Previous values are important when key is being rotated: there may be valid outstanding derivatives of previous values of the secret.

func GetSecret

func GetSecret(c context.Context, key string) (Secret, error)

GetSecret is a shortcut for grabbing a Store from the context and using its GetSecret method.

If the context doesn't have Store set, returns ErrNoStoreConfigured.

func (Secret) Blobs

func (s Secret) Blobs() [][]byte

Blobs returns current blob and all previous blobs as one array.

func (Secret) Equal

func (s Secret) Equal(a Secret) bool

Equal returns true if secrets are equal.

Does *not* run in constant time. Shouldn't be used in a cryptographic context due to susceptibility to timing attacks.

type SecretManagerSource

type SecretManagerSource struct {
	// contains filtered or unexported fields
}

SecretManagerSource is a Source that uses Google Secret Manager.

Construct it with NewSecretManagerSource.

func NewSecretManagerSource

func NewSecretManagerSource(ctx context.Context, secretURL string, ts oauth2.TokenSource) (*SecretManagerSource, error)

NewSecretManagerSource parses "sm://<project>/<name>" and sets up the source that fetches the latest two versions of this GSM secret as a single *Secret.

Uses the given TokenSource for authentication.

func (*SecretManagerSource) Close

func (s *SecretManagerSource) Close() error

Close is part of Source interface.

func (*SecretManagerSource) ReadSecret

func (s *SecretManagerSource) ReadSecret(ctx context.Context) (*Secret, error)

ReadSecret is part of Source interface.

type Source

type Source interface {
	// ReadSecret returns the most recent value of the secret in the source.
	ReadSecret(context.Context) (*Secret, error)
	// Close releases any allocated resources.
	Close() error
}

Source knows how to fetch (and refetch) a secret from some fixed location.

type StaticSource

type StaticSource struct {
	Secret *Secret
}

StaticSource is a Source that returns the same static secret all the time.

func (*StaticSource) Close

func (s *StaticSource) Close() error

Close is part of Source interface.

func (*StaticSource) ReadSecret

func (s *StaticSource) ReadSecret(context.Context) (*Secret, error)

ReadSecret is part of Source interface.

type StaticStore

type StaticStore map[string]Secret

StaticStore is Store with predefined secrets.

func (StaticStore) GetSecret

func (s StaticStore) GetSecret(k string) (Secret, error)

GetSecret returns a secret given its key or ErrNoSuchSecret if no such secret exists.

The caller must not mutate the secret.

type Store

type Store interface {
	// GetSecret returns a secret given its key.
	//
	// Store may choose to autogenerate a secret if there's no existing one, or it
	// may choose to treat it as a error and return ErrNoSuchSecret.
	GetSecret(name string) (Secret, error)
}

Store knows how to retrieve (or autogenerate) a secret given its key.

func Get

func Get(c context.Context) Store

Get grabs a Store by calling Factory stored in the context. If one hasn't been set, it returns nil.