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