vendor/github.com/aws/aws-sdk-go/aws/credentials/chain_provider.go

   1 package credentials
   2
   3 import (
   4         "github.com/aws/aws-sdk-go/aws/awserr"
   5 )
   6
   7 var (
   8         // ErrNoValidProvidersFoundInChain Is returned when there are no valid
   9         // providers in the ChainProvider.
  10         //
  11         // This has been deprecated. For verbose error messaging set
  12         // aws.Config.CredentialsChainVerboseErrors to true
  13         //
  14         // @readonly
  15         ErrNoValidProvidersFoundInChain = awserr.New("NoCredentialProviders",
  16                 `no valid providers in chain. Deprecated.
  17         For verbose messaging see aws.Config.CredentialsChainVerboseErrors`,
  18                 nil)
  19 )
  20
  21 // A ChainProvider will search for a provider which returns credentials
  22 // and cache that provider until Retrieve is called again.
  23 //
  24 // The ChainProvider provides a way of chaining multiple providers together
  25 // which will pick the first available using priority order of the Providers
  26 // in the list.
  27 //
  28 // If none of the Providers retrieve valid credentials Value, ChainProvider's
  29 // Retrieve() will return the error ErrNoValidProvidersFoundInChain.
  30 //
  31 // If a Provider is found which returns valid credentials Value ChainProvider
  32 // will cache that Provider for all calls to IsExpired(), until Retrieve is
  33 // called again.
  34 //
  35 // Example of ChainProvider to be used with an EnvProvider and EC2RoleProvider.
  36 // In this example EnvProvider will first check if any credentials are available
  37 // via the environment variables. If there are none ChainProvider will check
  38 // the next Provider in the list, EC2RoleProvider in this case. If EC2RoleProvider
  39 // does not return any credentials ChainProvider will return the error
  40 // ErrNoValidProvidersFoundInChain
  41 //
  42 //     creds := credentials.NewChainCredentials(
  43 //         []credentials.Provider{
  44 //             &credentials.EnvProvider{},
  45 //             &ec2rolecreds.EC2RoleProvider{
  46 //                 Client: ec2metadata.New(sess),
  47 //             },
  48 //         })
  49 //
  50 //     // Usage of ChainCredentials with aws.Config
  51 //     svc := ec2.New(session.Must(session.NewSession(&aws.Config{
  52 //       Credentials: creds,
  53 //     })))
  54 //
  55 type ChainProvider struct {
  56         Providers     []Provider
  57         curr          Provider
  58         VerboseErrors bool
  59 }
  60
  61 // NewChainCredentials returns a pointer to a new Credentials object
  62 // wrapping a chain of providers.
  63 func NewChainCredentials(providers []Provider) *Credentials {
  64         return NewCredentials(&ChainProvider{
  65                 Providers: append([]Provider{}, providers...),
  66         })
  67 }
  68
  69 // Retrieve returns the credentials value or error if no provider returned
  70 // without error.
  71 //
  72 // If a provider is found it will be cached and any calls to IsExpired()
  73 // will return the expired state of the cached provider.
  74 func (c *ChainProvider) Retrieve() (Value, error) {
  75         var errs []error
  76         for _, p := range c.Providers {
  77                 creds, err := p.Retrieve()
  78                 if err == nil {
  79                         c.curr = p
  80                         return creds, nil
  81                 }
  82                 errs = append(errs, err)
  83         }
  84         c.curr = nil
  85
  86         var err error
  87         err = ErrNoValidProvidersFoundInChain
  88         if c.VerboseErrors {
  89                 err = awserr.NewBatchError("NoCredentialProviders", "no valid providers in chain", errs)
  90         }
  91         return Value{}, err
  92 }
  93
  94 // IsExpired will returned the expired state of the currently cached provider
  95 // if there is one.  If there is no current provider, true will be returned.
  96 func (c *ChainProvider) IsExpired() bool {
  97         if c.curr != nil {
  98                 return c.curr.IsExpired()
  99         }
 100
 101         return true
 102 }