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/*
* MinIO Go Library for Amazon S3 Compatible Cloud Storage
* Copyright 2017 MinIO, Inc.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package credentials
// A Chain will search for a provider which returns credentials
// and cache that provider until Retrieve is called again.
//
// The Chain provides a way of chaining multiple providers together
// which will pick the first available using priority order of the
// Providers in the list.
//
// If none of the Providers retrieve valid credentials Value, ChainProvider's
// Retrieve() will return the no credentials value.
//
// If a Provider is found which returns valid credentials Value ChainProvider
// will cache that Provider for all calls to IsExpired(), until Retrieve is
// called again after IsExpired() is true.
//
// creds := credentials.NewChainCredentials(
// []credentials.Provider{
// &credentials.EnvAWSS3{},
// &credentials.EnvMinio{},
// })
//
// // Usage of ChainCredentials.
// mc, err := minio.NewWithCredentials(endpoint, creds, secure, "us-east-1")
// if err != nil {
// log.Fatalln(err)
// }
//
type Chain struct {
Providers []Provider
curr Provider
}
// NewChainCredentials returns a pointer to a new Credentials object
// wrapping a chain of providers.
func NewChainCredentials(providers []Provider) *Credentials {
return New(&Chain{
Providers: append([]Provider{}, providers...),
})
}
// Retrieve returns the credentials value, returns no credentials(anonymous)
// if no credentials provider returned any value.
//
// If a provider is found with credentials, it will be cached and any calls
// to IsExpired() will return the expired state of the cached provider.
func (c *Chain) Retrieve() (Value, error) {
for _, p := range c.Providers {
creds, _ := p.Retrieve()
// Always prioritize non-anonymous providers, if any.
if creds.AccessKeyID == "" && creds.SecretAccessKey == "" {
continue
}
c.curr = p
return creds, nil
}
// At this point we have exhausted all the providers and
// are left without any credentials return anonymous.
return Value{
SignerType: SignatureAnonymous,
}, nil
}
// IsExpired will returned the expired state of the currently cached provider
// if there is one. If there is no current provider, true will be returned.
func (c *Chain) IsExpired() bool {
if c.curr != nil {
return c.curr.IsExpired()
}
return true
}
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