distribution/docs/tokens.go

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package registry
import (
"crypto/hmac"
"crypto/sha256"
"encoding/base64"
"encoding/json"
"fmt"
"github.com/docker/distribution/storage"
)
// tokenProvider contains methods for serializing and deserializing state from token strings.
type tokenProvider interface {
// layerUploadStateFromToken retrieves the LayerUploadState for a given state token.
layerUploadStateFromToken(stateToken string) (storage.LayerUploadState, error)
// layerUploadStateToToken returns a token string representing the given LayerUploadState.
layerUploadStateToToken(layerUploadState storage.LayerUploadState) (string, error)
}
type hmacTokenProvider struct {
secret string
}
func newHMACTokenProvider(secret string) tokenProvider {
return &hmacTokenProvider{secret: secret}
}
// layerUploadStateFromToken deserializes the given HMAC stateToken and validates the prefix HMAC
func (ts *hmacTokenProvider) layerUploadStateFromToken(stateToken string) (storage.LayerUploadState, error) {
var lus storage.LayerUploadState
tokenBytes, err := base64.URLEncoding.DecodeString(stateToken)
if err != nil {
return lus, err
}
mac := hmac.New(sha256.New, []byte(ts.secret))
if len(tokenBytes) < mac.Size() {
return lus, fmt.Errorf("Invalid token")
}
macBytes := tokenBytes[:mac.Size()]
messageBytes := tokenBytes[mac.Size():]
mac.Write(messageBytes)
if !hmac.Equal(mac.Sum(nil), macBytes) {
return lus, fmt.Errorf("Invalid token")
}
if err := json.Unmarshal(messageBytes, &lus); err != nil {
return lus, err
}
return lus, nil
}
// layerUploadStateToToken serializes the given LayerUploadState to JSON with an HMAC prepended
func (ts *hmacTokenProvider) layerUploadStateToToken(lus storage.LayerUploadState) (string, error) {
mac := hmac.New(sha256.New, []byte(ts.secret))
stateJSON := fmt.Sprintf("{\"Name\": \"%s\", \"UUID\": \"%s\", \"Offset\": %d}", lus.Name, lus.UUID, lus.Offset)
mac.Write([]byte(stateJSON))
return base64.URLEncoding.EncodeToString(append(mac.Sum(nil), stateJSON...)), nil
}