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package s3
import (
"context"
"crypto/hmac"
"crypto/sha256"
"errors"
"fmt"
"sync"
"time"
"github.com/aws/aws-sdk-go-v2/aws"
"github.com/aws/aws-sdk-go-v2/internal/sdk"
"github.com/aws/aws-sdk-go-v2/internal/sync/singleflight"
"github.com/aws/smithy-go/container/private/cache"
"github.com/aws/smithy-go/container/private/cache/lru"
)
const s3ExpressCacheCap = 100
const s3ExpressRefreshWindow = 1 * time.Minute
type cacheKey struct {
CredentialsHash string // hmac(sigv4 akid, sigv4 secret)
Bucket string
}
func (c cacheKey) Slug() string {
return fmt.Sprintf("%s%s", c.CredentialsHash, c.Bucket)
}
type sessionCredsCache struct {
mu sync.Mutex
cache cache.Cache
}
func (c *sessionCredsCache) Get(key cacheKey) (*aws.Credentials, bool) {
c.mu.Lock()
defer c.mu.Unlock()
if v, ok := c.cache.Get(key); ok {
return v.(*aws.Credentials), true
}
return nil, false
}
func (c *sessionCredsCache) Put(key cacheKey, creds *aws.Credentials) {
c.mu.Lock()
defer c.mu.Unlock()
c.cache.Put(key, creds)
}
// The default S3Express provider uses an LRU cache with a capacity of 100.
//
// Credentials will be refreshed asynchronously when a Retrieve() call is made
// for cached credentials within an expiry window (1 minute, currently
// non-configurable).
type defaultS3ExpressCredentialsProvider struct {
sf singleflight.Group
client createSessionAPIClient
cache *sessionCredsCache
refreshWindow time.Duration
v4creds aws.CredentialsProvider // underlying credentials used for CreateSession
}
type createSessionAPIClient interface {
CreateSession(context.Context, *CreateSessionInput, ...func(*Options)) (*CreateSessionOutput, error)
}
func newDefaultS3ExpressCredentialsProvider() *defaultS3ExpressCredentialsProvider {
return &defaultS3ExpressCredentialsProvider{
cache: &sessionCredsCache{
cache: lru.New(s3ExpressCacheCap),
},
refreshWindow: s3ExpressRefreshWindow,
}
}
// returns a cloned provider using new base credentials, used when per-op
// config mutations change the credentials provider
func (p *defaultS3ExpressCredentialsProvider) CloneWithBaseCredentials(v4creds aws.CredentialsProvider) *defaultS3ExpressCredentialsProvider {
return &defaultS3ExpressCredentialsProvider{
client: p.client,
cache: p.cache,
refreshWindow: p.refreshWindow,
v4creds: v4creds,
}
}
func (p *defaultS3ExpressCredentialsProvider) Retrieve(ctx context.Context, bucket string) (aws.Credentials, error) {
v4creds, err := p.v4creds.Retrieve(ctx)
if err != nil {
return aws.Credentials{}, fmt.Errorf("get sigv4 creds: %w", err)
}
key := cacheKey{
CredentialsHash: gethmac(v4creds.AccessKeyID, v4creds.SecretAccessKey),
Bucket: bucket,
}
creds, ok := p.cache.Get(key)
if !ok || creds.Expired() {
return p.awaitDoChanRetrieve(ctx, key)
}
if creds.Expires.Sub(sdk.NowTime()) <= p.refreshWindow {
p.doChanRetrieve(ctx, key)
}
return *creds, nil
}
func (p *defaultS3ExpressCredentialsProvider) doChanRetrieve(ctx context.Context, key cacheKey) <-chan singleflight.Result {
return p.sf.DoChan(key.Slug(), func() (interface{}, error) {
return p.retrieve(ctx, key)
})
}
func (p *defaultS3ExpressCredentialsProvider) awaitDoChanRetrieve(ctx context.Context, key cacheKey) (aws.Credentials, error) {
ch := p.doChanRetrieve(ctx, key)
select {
case r := <-ch:
return r.Val.(aws.Credentials), r.Err
case <-ctx.Done():
return aws.Credentials{}, errors.New("s3express retrieve credentials canceled")
}
}
func (p *defaultS3ExpressCredentialsProvider) retrieve(ctx context.Context, key cacheKey) (aws.Credentials, error) {
resp, err := p.client.CreateSession(ctx, &CreateSessionInput{
Bucket: aws.String(key.Bucket),
})
if err != nil {
return aws.Credentials{}, err
}
creds, err := credentialsFromResponse(resp)
if err != nil {
return aws.Credentials{}, err
}
p.cache.Put(key, creds)
return *creds, nil
}
func credentialsFromResponse(o *CreateSessionOutput) (*aws.Credentials, error) {
if o.Credentials == nil {
return nil, errors.New("s3express session credentials unset")
}
if o.Credentials.AccessKeyId == nil || o.Credentials.SecretAccessKey == nil || o.Credentials.SessionToken == nil || o.Credentials.Expiration == nil {
return nil, errors.New("s3express session credentials missing one or more required fields")
}
return &aws.Credentials{
AccessKeyID: *o.Credentials.AccessKeyId,
SecretAccessKey: *o.Credentials.SecretAccessKey,
SessionToken: *o.Credentials.SessionToken,
CanExpire: true,
Expires: *o.Credentials.Expiration,
}, nil
}
func gethmac(p, key string) string {
hash := hmac.New(sha256.New, []byte(key))
hash.Write([]byte(p))
return string(hash.Sum(nil))
}
|
