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package handlers
import (
"crypto/hmac"
"crypto/sha256"
"encoding/base64"
"encoding/json"
"fmt"
"time"
)
// blobUploadState captures the state serializable state of the blob upload.
type blobUploadState struct {
// name is the primary repository under which the blob will be linked.
Name string
// UUID identifies the upload.
UUID string
// offset contains the current progress of the upload.
Offset int64
// StartedAt is the original start time of the upload.
StartedAt time.Time
}
type hmacKey string
var errInvalidSecret = fmt.Errorf("invalid secret")
// unpackUploadState unpacks and validates the blob upload state from the
// token, using the hmacKey secret.
func (secret hmacKey) unpackUploadState(token string) (blobUploadState, error) {
var state blobUploadState
tokenBytes, err := base64.URLEncoding.DecodeString(token)
if err != nil {
return state, err
}
mac := hmac.New(sha256.New, []byte(secret))
if len(tokenBytes) < mac.Size() {
return state, errInvalidSecret
}
macBytes := tokenBytes[:mac.Size()]
messageBytes := tokenBytes[mac.Size():]
mac.Write(messageBytes)
if !hmac.Equal(mac.Sum(nil), macBytes) {
return state, errInvalidSecret
}
if err := json.Unmarshal(messageBytes, &state); err != nil {
return state, err
}
return state, nil
}
// packUploadState packs the upload state signed with and hmac digest using
// the hmacKey secret, encoding to url safe base64. The resulting token can be
// used to share data with minimized risk of external tampering.
func (secret hmacKey) packUploadState(lus blobUploadState) (string, error) {
mac := hmac.New(sha256.New, []byte(secret))
p, err := json.Marshal(lus)
if err != nil {
return "", err
}
mac.Write(p)
return base64.URLEncoding.EncodeToString(append(mac.Sum(nil), p...)), nil
}
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