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credentials.go
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credentials.go
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// Copyright (C) MongoDB, Inc. 2023-present.
//
// 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
//
// Based on github.com/aws/aws-sdk-go by Amazon.com, Inc. with code from:
// - github.com/aws/aws-sdk-go/blob/v1.44.225/aws/credentials/credentials.go
// See THIRD-PARTY-NOTICES for original license terms
package credentials
import (
"context"
"sync"
"time"
"go.mongodb.org/mongo-driver/internal/aws/awserr"
"golang.org/x/sync/singleflight"
)
// A Value is the AWS credentials value for individual credential fields.
//
// A Value is also used to represent Azure credentials.
// Azure credentials only consist of an access token, which is stored in the `SessionToken` field.
type Value struct {
// AWS Access key ID
AccessKeyID string
// AWS Secret Access Key
SecretAccessKey string
// AWS Session Token
SessionToken string
// Provider used to get credentials
ProviderName string
}
// HasKeys returns if the credentials Value has both AccessKeyID and
// SecretAccessKey value set.
func (v Value) HasKeys() bool {
return len(v.AccessKeyID) != 0 && len(v.SecretAccessKey) != 0
}
// A Provider is the interface for any component which will provide credentials
// Value. A provider is required to manage its own Expired state, and what to
// be expired means.
//
// The Provider should not need to implement its own mutexes, because
// that will be managed by Credentials.
type Provider interface {
// Retrieve returns nil if it successfully retrieved the value.
// Error is returned if the value were not obtainable, or empty.
Retrieve() (Value, error)
// IsExpired returns if the credentials are no longer valid, and need
// to be retrieved.
IsExpired() bool
}
// ProviderWithContext is a Provider that can retrieve credentials with a Context
type ProviderWithContext interface {
Provider
RetrieveWithContext(context.Context) (Value, error)
}
// A Credentials provides concurrency safe retrieval of AWS credentials Value.
//
// A Credentials is also used to fetch Azure credentials Value.
//
// Credentials will cache the credentials value until they expire. Once the value
// expires the next Get will attempt to retrieve valid credentials.
//
// Credentials is safe to use across multiple goroutines and will manage the
// synchronous state so the Providers do not need to implement their own
// synchronization.
//
// The first Credentials.Get() will always call Provider.Retrieve() to get the
// first instance of the credentials Value. All calls to Get() after that
// will return the cached credentials Value until IsExpired() returns true.
type Credentials struct {
sf singleflight.Group
m sync.RWMutex
creds Value
provider Provider
}
// NewCredentials returns a pointer to a new Credentials with the provider set.
func NewCredentials(provider Provider) *Credentials {
c := &Credentials{
provider: provider,
}
return c
}
// GetWithContext returns the credentials value, or error if the credentials
// Value failed to be retrieved. Will return early if the passed in context is
// canceled.
//
// Will return the cached credentials Value if it has not expired. If the
// credentials Value has expired the Provider's Retrieve() will be called
// to refresh the credentials.
//
// If Credentials.Expire() was called the credentials Value will be force
// expired, and the next call to Get() will cause them to be refreshed.
func (c *Credentials) GetWithContext(ctx context.Context) (Value, error) {
// Check if credentials are cached, and not expired.
select {
case curCreds, ok := <-c.asyncIsExpired():
// ok will only be true, of the credentials were not expired. ok will
// be false and have no value if the credentials are expired.
if ok {
return curCreds, nil
}
case <-ctx.Done():
return Value{}, awserr.New("RequestCanceled",
"request context canceled", ctx.Err())
}
// Cannot pass context down to the actual retrieve, because the first
// context would cancel the whole group when there is not direct
// association of items in the group.
resCh := c.sf.DoChan("", func() (interface{}, error) {
return c.singleRetrieve(&suppressedContext{ctx})
})
select {
case res := <-resCh:
return res.Val.(Value), res.Err
case <-ctx.Done():
return Value{}, awserr.New("RequestCanceled",
"request context canceled", ctx.Err())
}
}
func (c *Credentials) singleRetrieve(ctx context.Context) (interface{}, error) {
c.m.Lock()
defer c.m.Unlock()
if curCreds := c.creds; !c.isExpiredLocked(curCreds) {
return curCreds, nil
}
var creds Value
var err error
if p, ok := c.provider.(ProviderWithContext); ok {
creds, err = p.RetrieveWithContext(ctx)
} else {
creds, err = c.provider.Retrieve()
}
if err == nil {
c.creds = creds
}
return creds, err
}
// asyncIsExpired returns a channel of credentials Value. If the channel is
// closed the credentials are expired and credentials value are not empty.
func (c *Credentials) asyncIsExpired() <-chan Value {
ch := make(chan Value, 1)
go func() {
c.m.RLock()
defer c.m.RUnlock()
if curCreds := c.creds; !c.isExpiredLocked(curCreds) {
ch <- curCreds
}
close(ch)
}()
return ch
}
// isExpiredLocked helper method wrapping the definition of expired credentials.
func (c *Credentials) isExpiredLocked(creds interface{}) bool {
return creds == nil || creds.(Value) == Value{} || c.provider.IsExpired()
}
type suppressedContext struct {
context.Context
}
func (s *suppressedContext) Deadline() (deadline time.Time, ok bool) {
return time.Time{}, false
}
func (s *suppressedContext) Done() <-chan struct{} {
return nil
}
func (s *suppressedContext) Err() error {
return nil
}