214 lines
7.0 KiB
Go
214 lines
7.0 KiB
Go
// Copyright (c) 2021 Tulir Asokan
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//
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// This Source Code Form is subject to the terms of the Mozilla Public
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// License, v. 2.0. If a copy of the MPL was not distributed with this
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// file, You can obtain one at http://mozilla.org/MPL/2.0/.
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package whatsmeow
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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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"fmt"
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"io"
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"net/http"
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"google.golang.org/protobuf/proto"
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"google.golang.org/protobuf/reflect/protoreflect"
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waProto "go.mau.fi/whatsmeow/binary/proto"
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"go.mau.fi/whatsmeow/util/cbcutil"
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"go.mau.fi/whatsmeow/util/hkdfutil"
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)
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// MediaType represents a type of uploaded file on WhatsApp.
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// The value is the key which is used as a part of generating the encryption keys.
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type MediaType string
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// The known media types
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const (
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MediaImage MediaType = "WhatsApp Image Keys"
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MediaVideo MediaType = "WhatsApp Video Keys"
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MediaAudio MediaType = "WhatsApp Audio Keys"
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MediaDocument MediaType = "WhatsApp Document Keys"
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MediaHistory MediaType = "WhatsApp History Keys"
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MediaAppState MediaType = "WhatsApp App State Keys"
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)
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// DownloadableMessage represents a protobuf message that contains attachment info.
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type DownloadableMessage interface {
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proto.Message
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GetDirectPath() string
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GetMediaKey() []byte
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GetFileSha256() []byte
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GetFileEncSha256() []byte
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}
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// All the message types that are intended to be downloadable
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var (
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_ DownloadableMessage = (*waProto.ImageMessage)(nil)
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_ DownloadableMessage = (*waProto.AudioMessage)(nil)
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_ DownloadableMessage = (*waProto.VideoMessage)(nil)
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_ DownloadableMessage = (*waProto.DocumentMessage)(nil)
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_ DownloadableMessage = (*waProto.StickerMessage)(nil)
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_ DownloadableMessage = (*waProto.HistorySyncNotification)(nil)
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_ DownloadableMessage = (*waProto.ExternalBlobReference)(nil)
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)
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type downloadableMessageWithLength interface {
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DownloadableMessage
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GetFileLength() uint64
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}
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type downloadableMessageWithSizeBytes interface {
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DownloadableMessage
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GetFileSizeBytes() uint64
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}
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type downloadableMessageWithURL interface {
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DownloadableMessage
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GetUrl() string
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}
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var classToMediaType = map[protoreflect.Name]MediaType{
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"ImageMessage": MediaImage,
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"AudioMessage": MediaAudio,
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"VideoMessage": MediaVideo,
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"DocumentMessage": MediaDocument,
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"StickerMessage": MediaImage,
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"HistorySyncNotification": MediaHistory,
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"ExternalBlobReference": MediaAppState,
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}
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var mediaTypeToMMSType = map[MediaType]string{
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MediaImage: "image",
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MediaAudio: "audio",
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MediaVideo: "video",
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MediaDocument: "document",
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MediaHistory: "md-msg-hist",
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MediaAppState: "md-app-state",
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}
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// DownloadAny loops through the downloadable parts of the given message and downloads the first non-nil item.
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func (cli *Client) DownloadAny(msg *waProto.Message) (data []byte, err error) {
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downloadables := []DownloadableMessage{msg.GetImageMessage(), msg.GetAudioMessage(), msg.GetVideoMessage(), msg.GetDocumentMessage(), msg.GetStickerMessage()}
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for _, downloadable := range downloadables {
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if downloadable != nil {
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return cli.Download(downloadable)
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}
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}
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return nil, ErrNothingDownloadableFound
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}
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func getSize(msg DownloadableMessage) int {
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switch sized := msg.(type) {
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case downloadableMessageWithLength:
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return int(sized.GetFileLength())
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case downloadableMessageWithSizeBytes:
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return int(sized.GetFileSizeBytes())
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default:
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return -1
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}
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}
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// Download downloads the attachment from the given protobuf message.
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func (cli *Client) Download(msg DownloadableMessage) (data []byte, err error) {
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mediaType, ok := classToMediaType[msg.ProtoReflect().Descriptor().Name()]
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if !ok {
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return nil, fmt.Errorf("%w '%s'", ErrUnknownMediaType, string(msg.ProtoReflect().Descriptor().Name()))
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}
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urlable, ok := msg.(downloadableMessageWithURL)
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if ok && len(urlable.GetUrl()) > 0 {
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return downloadAndDecrypt(urlable.GetUrl(), msg.GetMediaKey(), mediaType, getSize(msg), msg.GetFileEncSha256(), msg.GetFileSha256())
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} else if len(msg.GetDirectPath()) > 0 {
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return cli.downloadMediaWithPath(msg.GetDirectPath(), msg.GetFileEncSha256(), msg.GetFileSha256(), msg.GetMediaKey(), getSize(msg), mediaType, mediaTypeToMMSType[mediaType])
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} else {
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return nil, ErrNoURLPresent
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}
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}
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func (cli *Client) downloadMediaWithPath(directPath string, encFileHash, fileHash, mediaKey []byte, fileLength int, mediaType MediaType, mmsType string) (data []byte, err error) {
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err = cli.refreshMediaConn(false)
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if err != nil {
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return nil, fmt.Errorf("failed to refresh media connections: %w", err)
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}
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for i, host := range cli.mediaConn.Hosts {
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mediaURL := fmt.Sprintf("https://%s%s&hash=%s&mms-type=%s&__wa-mms=", host.Hostname, directPath, base64.URLEncoding.EncodeToString(encFileHash), mmsType)
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data, err = downloadAndDecrypt(mediaURL, mediaKey, mediaType, fileLength, encFileHash, fileHash)
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// TODO there are probably some errors that shouldn't retry
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if err != nil {
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if i >= len(cli.mediaConn.Hosts)-1 {
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return nil, fmt.Errorf("failed to download media from last host: %w", err)
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}
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cli.Log.Warnf("Failed to download media: %s, trying with next host...", err)
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}
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}
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return
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}
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func downloadAndDecrypt(url string, mediaKey []byte, appInfo MediaType, fileLength int, fileEncSha256, fileSha256 []byte) (data []byte, err error) {
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iv, cipherKey, macKey, _ := getMediaKeys(mediaKey, appInfo)
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var ciphertext, mac []byte
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if ciphertext, mac, err = downloadEncryptedMedia(url, fileEncSha256); err != nil {
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} else if err = validateMedia(iv, ciphertext, macKey, mac); err != nil {
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} else if data, err = cbcutil.Decrypt(cipherKey, iv, ciphertext); err != nil {
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err = fmt.Errorf("failed to decrypt file: %w", err)
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} else if fileLength >= 0 && len(data) != fileLength {
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err = fmt.Errorf("%w: expected %d, got %d", ErrFileLengthMismatch, fileLength, len(data))
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} else if len(fileSha256) == 32 && sha256.Sum256(data) != *(*[32]byte)(fileSha256) {
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err = ErrInvalidMediaSHA256
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}
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return
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}
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func getMediaKeys(mediaKey []byte, appInfo MediaType) (iv, cipherKey, macKey, refKey []byte) {
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mediaKeyExpanded := hkdfutil.SHA256(mediaKey, nil, []byte(appInfo), 112)
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return mediaKeyExpanded[:16], mediaKeyExpanded[16:48], mediaKeyExpanded[48:80], mediaKeyExpanded[80:]
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}
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func downloadEncryptedMedia(url string, checksum []byte) (file, mac []byte, err error) {
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var resp *http.Response
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resp, err = http.Get(url)
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if err != nil {
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return
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}
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defer resp.Body.Close()
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if resp.StatusCode != http.StatusOK {
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if resp.StatusCode == http.StatusNotFound {
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err = ErrMediaDownloadFailedWith404
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} else if resp.StatusCode == http.StatusGone {
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err = ErrMediaDownloadFailedWith410
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} else {
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err = fmt.Errorf("download failed with status code %d", resp.StatusCode)
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}
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return
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}
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var data []byte
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data, err = io.ReadAll(resp.Body)
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if err != nil {
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return
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} else if len(data) <= 10 {
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err = ErrTooShortFile
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return
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}
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file, mac = data[:len(data)-10], data[len(data)-10:]
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if len(checksum) == 32 && sha256.Sum256(data) != *(*[32]byte)(checksum) {
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err = ErrInvalidMediaEncSHA256
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}
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return
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}
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func validateMedia(iv, file, macKey, mac []byte) error {
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h := hmac.New(sha256.New, macKey)
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h.Write(iv)
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h.Write(file)
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if !hmac.Equal(h.Sum(nil)[:10], mac) {
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return ErrInvalidMediaHMAC
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}
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return nil
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}
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