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