plugincreds

Documentation

Overview

Package plugincreds implements a credentials provider sourced from a Go plugin. This package allows you to use a Go plugin to retrieve AWS credentials for the SDK to use for service API calls.

As of Go 1.8 plugins are only supported on the Linux platform.

Plugin Symbol Name

The "GetAWSSDKCredentialProvider" is the symbol name that will be used to lookup the credentials provider getter from the plugin. If you want to use a custom symbol name you should use GetPluginProviderFnsByName to lookup the symbol by a custom name.

This symbol is a function that returns two additional functions. One to retrieve the credentials, and another to determine if the credentials have expired.

Plugin Symbol Signature

The plugin credential provider requires the symbol to match the following signature.

func() (RetrieveFn func() (key, secret, token string, err error), IsExpiredFn func() bool)

Plugin Implementation Exmaple

The following is an example implementation of a SDK credential provider using the plugin provider in this package. See the SDK's example/aws/credential/plugincreds/plugin folder for a runnable example of this.

package main

func main() {}

var myCredProvider provider

// Build: go build -o plugin.so -buildmode=plugin plugin.go
func init() {
	// Initialize a mock credential provider with stubs
	myCredProvider = provider{"a","b","c"}
}

// GetAWSSDKCredentialProvider is the symbol SDK will lookup and use to
// get the credential provider's retrieve and isExpired functions.
func GetAWSSDKCredentialProvider() (func() (key, secret, token string, err error), func() bool) {
	return myCredProvider.Retrieve,	myCredProvider.IsExpired
}

// mock implementation of a type that returns retrieves credentials and
// returns if they have expired.
type provider struct {
	key, secret, token string
}

func (p provider) Retrieve() (key, secret, token string, err error) {
	return p.key, p.secret, p.token, nil
}

func (p *provider) IsExpired() bool {
	return false;
}

Configuring SDK for Plugin Credentials

To configure the SDK to use a plugin's credential provider you'll need to first open the plugin file using the plugin standard library package. Once you have a handle to the plugin you can use the NewCredentials function of this package to create a new credentials.Credentials value that can be set as the credentials loader of a Session or Config. See the SDK's example/aws/credential/plugincreds folder for a runnable example of this.

// Open plugin, and load it into the process.
p, err := plugin.Open("somefile.so")
if err != nil {
	return nil, err
}

// Create a new Credentials value which will source the provider's Retrieve
// and IsExpired functions from the plugin.
creds, err := plugincreds.NewCredentials(p)
if err != nil {
	return nil, err
}

// Example to configure a Session with the newly created credentials that
// will be sourced using the plugin's functionality.
sess := session.Must(session.NewSession(&aws.Config{
	Credentials:  creds,
}))

Index

• Constants
• func GetPluginProviderFns(p *plugin.Plugin) (func() (key, secret, token string, err error), func() bool, error)
• func GetPluginProviderFnsByName(p *plugin.Plugin, symbolName string) (func() (key, secret, token string, err error), func() bool, error)
• func NewCredentials(p *plugin.Plugin) (*credentials.Credentials, error)
• type Provider
  • func (p Provider) IsExpired() bool
  • func (p Provider) Retrieve() (credentials.Value, error)

Constants

const (
	// ErrCodeLookupSymbolError failed to lookup symbol
	ErrCodeLookupSymbolError = "LookupSymbolError"

	// ErrCodeInvalidSymbolError symbol invalid
	ErrCodeInvalidSymbolError = "InvalidSymbolError"

	// ErrCodePluginRetrieveNil Retrieve function was nil
	ErrCodePluginRetrieveNil = "PluginRetrieveNilError"

	// ErrCodePluginIsExpiredNil IsExpired Function was nil
	ErrCodePluginIsExpiredNil = "PluginIsExpiredNilError"

	// ErrCodePluginProviderRetrieve plugin provider's retrieve returned error
	ErrCodePluginProviderRetrieve = "PluginProviderRetrieveError"
)

const ProviderName = `PluginCredentialsProvider`

ProviderName is the name this credentials provider will label any returned credentials Value with.

const ProviderSymbolName = `GetAWSSDKCredentialProvider`

ProviderSymbolName the symbol name the SDK will use to lookup the plugin provider value from.

Functions

func GetPluginProviderFns

func GetPluginProviderFns(p *plugin.Plugin) (func() (key, secret, token string, err error), func() bool, error)

GetPluginProviderFns returns the plugin's Retrieve and IsExpired functions returned by the plugin's credential provider getter.

Uses ProviderSymbolName as the symbol name when lookup up the symbol. If you want to use a different symbol name, use GetPluginProviderFnsByName.

func GetPluginProviderFnsByName

func GetPluginProviderFnsByName(p *plugin.Plugin, symbolName string) (func() (key, secret, token string, err error), func() bool, error)

GetPluginProviderFnsByName returns the plugin's Retrieve and IsExpired functions returned by the plugin's credential provider getter.

Same as GetPluginProviderFns, but takes a custom symbolName to lookup with.

func NewCredentials

func NewCredentials(p *plugin.Plugin) (*credentials.Credentials, error)

NewCredentials returns a new Credentials loader using the plugin provider. If the symbol isn't found or is invalid in the plugin an error will be returned.

Types

type Provider

type Provider struct {
	RetrieveFn  func() (key, secret, token string, err error)
	IsExpiredFn func() bool
}

Provider is the credentials provider that will use the plugin provided Retrieve and IsExpired functions to retrieve credentials.

func (Provider) IsExpired

func (p Provider) IsExpired() bool

IsExpired will return the expired state of the underlying plugin provider.

func (Provider) Retrieve

func (p Provider) Retrieve() (credentials.Value, error)

Retrieve will return the credentials Value if they were successfully retrieved from the underlying plugin provider. An error will be returned otherwise.