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| 1 | +// Copyright (c) 2024 Tulir Asokan |
| 2 | +// |
| 3 | +// This Source Code Form is subject to the terms of the Mozilla Public |
| 4 | +// License, v. 2.0. If a copy of the MPL was not distributed with this |
| 5 | +// file, You can obtain one at http://mozilla.org/MPL/2.0/. |
| 6 | + |
| 7 | +package whatsmeow |
| 8 | + |
| 9 | +import ( |
| 10 | + "crypto/hmac" |
| 11 | + "crypto/sha256" |
| 12 | + "encoding/base64" |
| 13 | + "errors" |
| 14 | + "fmt" |
| 15 | + "io" |
| 16 | + "os" |
| 17 | + "strings" |
| 18 | + "time" |
| 19 | + |
| 20 | + "go.mau.fi/util/fallocate" |
| 21 | + "go.mau.fi/util/retryafter" |
| 22 | + |
| 23 | + "go.mau.fi/whatsmeow/proto/waMediaTransport" |
| 24 | + "go.mau.fi/whatsmeow/util/cbcutil" |
| 25 | +) |
| 26 | + |
| 27 | +type File interface { |
| 28 | + io.Reader |
| 29 | + io.Writer |
| 30 | + io.Seeker |
| 31 | + io.ReaderAt |
| 32 | + io.WriterAt |
| 33 | + Truncate(size int64) error |
| 34 | + Stat() (os.FileInfo, error) |
| 35 | +} |
| 36 | + |
| 37 | +// DownloadToFile downloads the attachment from the given protobuf message. |
| 38 | +// |
| 39 | +// This is otherwise identical to [Download], but writes the attachment to a file instead of returning it as a byte slice. |
| 40 | +func (cli *Client) DownloadToFile(msg DownloadableMessage, file File) error { |
| 41 | + mediaType, ok := classToMediaType[msg.ProtoReflect().Descriptor().Name()] |
| 42 | + if !ok { |
| 43 | + return fmt.Errorf("%w '%s'", ErrUnknownMediaType, string(msg.ProtoReflect().Descriptor().Name())) |
| 44 | + } |
| 45 | + urlable, ok := msg.(downloadableMessageWithURL) |
| 46 | + var url string |
| 47 | + var isWebWhatsappNetURL bool |
| 48 | + if ok { |
| 49 | + url = urlable.GetUrl() |
| 50 | + isWebWhatsappNetURL = strings.HasPrefix(url, "https://web.whatsapp.net") |
| 51 | + } |
| 52 | + if len(url) > 0 && !isWebWhatsappNetURL { |
| 53 | + return cli.downloadAndDecryptToFile(url, msg.GetMediaKey(), mediaType, getSize(msg), msg.GetFileEncSHA256(), msg.GetFileSHA256(), file) |
| 54 | + } else if len(msg.GetDirectPath()) > 0 { |
| 55 | + return cli.DownloadMediaWithPathToFile(msg.GetDirectPath(), msg.GetFileEncSHA256(), msg.GetFileSHA256(), msg.GetMediaKey(), getSize(msg), mediaType, mediaTypeToMMSType[mediaType], file) |
| 56 | + } else { |
| 57 | + if isWebWhatsappNetURL { |
| 58 | + cli.Log.Warnf("Got a media message with a web.whatsapp.net URL (%s) and no direct path", url) |
| 59 | + } |
| 60 | + return ErrNoURLPresent |
| 61 | + } |
| 62 | +} |
| 63 | + |
| 64 | +func (cli *Client) DownloadFBToFile(transport *waMediaTransport.WAMediaTransport_Integral, mediaType MediaType, file File) error { |
| 65 | + return cli.DownloadMediaWithPathToFile(transport.GetDirectPath(), transport.GetFileEncSHA256(), transport.GetFileSHA256(), transport.GetMediaKey(), -1, mediaType, mediaTypeToMMSType[mediaType], file) |
| 66 | +} |
| 67 | + |
| 68 | +func (cli *Client) DownloadMediaWithPathToFile(directPath string, encFileHash, fileHash, mediaKey []byte, fileLength int, mediaType MediaType, mmsType string, file File) error { |
| 69 | + mediaConn, err := cli.refreshMediaConn(false) |
| 70 | + if err != nil { |
| 71 | + return fmt.Errorf("failed to refresh media connections: %w", err) |
| 72 | + } |
| 73 | + if len(mmsType) == 0 { |
| 74 | + mmsType = mediaTypeToMMSType[mediaType] |
| 75 | + } |
| 76 | + for i, host := range mediaConn.Hosts { |
| 77 | + // TODO omit hash for unencrypted media? |
| 78 | + mediaURL := fmt.Sprintf("https://%s%s&hash=%s&mms-type=%s&__wa-mms=", host.Hostname, directPath, base64.URLEncoding.EncodeToString(encFileHash), mmsType) |
| 79 | + err = cli.downloadAndDecryptToFile(mediaURL, mediaKey, mediaType, fileLength, encFileHash, fileHash, file) |
| 80 | + if err == nil || errors.Is(err, ErrFileLengthMismatch) || errors.Is(err, ErrInvalidMediaSHA256) { |
| 81 | + return err |
| 82 | + } else if i >= len(mediaConn.Hosts)-1 { |
| 83 | + return fmt.Errorf("failed to download media from last host: %w", err) |
| 84 | + } |
| 85 | + // TODO there are probably some errors that shouldn't retry |
| 86 | + cli.Log.Warnf("Failed to download media: %s, trying with next host...", err) |
| 87 | + } |
| 88 | + return err |
| 89 | +} |
| 90 | + |
| 91 | +func (cli *Client) downloadAndDecryptToFile(url string, mediaKey []byte, appInfo MediaType, fileLength int, fileEncSHA256, fileSHA256 []byte, file File) error { |
| 92 | + iv, cipherKey, macKey, _ := getMediaKeys(mediaKey, appInfo) |
| 93 | + hasher := sha256.New() |
| 94 | + if mac, err := cli.downloadPossiblyEncryptedMediaWithRetriesToFile(url, fileEncSHA256, file); err != nil { |
| 95 | + return err |
| 96 | + } else if mediaKey == nil && fileEncSHA256 == nil && mac == nil { |
| 97 | + // Unencrypted media, just return the downloaded data |
| 98 | + return nil |
| 99 | + } else if err = validateMediaFile(file, iv, macKey, mac); err != nil { |
| 100 | + return err |
| 101 | + } else if _, err = file.Seek(0, io.SeekStart); err != nil { |
| 102 | + return fmt.Errorf("failed to seek to start of file after validating mac: %w", err) |
| 103 | + } else if err = cbcutil.DecryptFile(cipherKey, iv, file); err != nil { |
| 104 | + return fmt.Errorf("failed to decrypt file: %w", err) |
| 105 | + } else if info, err := file.Stat(); err != nil { |
| 106 | + return fmt.Errorf("failed to stat file: %w", err) |
| 107 | + } else if info.Size() != int64(fileLength) { |
| 108 | + return fmt.Errorf("%w: expected %d, got %d", ErrFileLengthMismatch, fileLength, info.Size()) |
| 109 | + } else if _, err = file.Seek(0, io.SeekStart); err != nil { |
| 110 | + return fmt.Errorf("failed to seek to start of file after decrypting: %w", err) |
| 111 | + } else if _, err = io.Copy(hasher, file); err != nil { |
| 112 | + return fmt.Errorf("failed to hash file: %w", err) |
| 113 | + } else if !hmac.Equal(fileSHA256, hasher.Sum(nil)) { |
| 114 | + return ErrInvalidMediaSHA256 |
| 115 | + } |
| 116 | + return nil |
| 117 | +} |
| 118 | + |
| 119 | +func (cli *Client) downloadPossiblyEncryptedMediaWithRetriesToFile(url string, checksum []byte, file File) (mac []byte, err error) { |
| 120 | + for retryNum := 0; retryNum < 5; retryNum++ { |
| 121 | + if checksum == nil { |
| 122 | + _, _, err = cli.downloadMediaToFile(url, file) |
| 123 | + } else { |
| 124 | + mac, err = cli.downloadEncryptedMediaToFile(url, checksum, file) |
| 125 | + } |
| 126 | + if err == nil || !shouldRetryMediaDownload(err) { |
| 127 | + return |
| 128 | + } |
| 129 | + retryDuration := time.Duration(retryNum+1) * time.Second |
| 130 | + var httpErr DownloadHTTPError |
| 131 | + if errors.As(err, &httpErr) { |
| 132 | + retryDuration = retryafter.Parse(httpErr.Response.Header.Get("Retry-After"), retryDuration) |
| 133 | + } |
| 134 | + cli.Log.Warnf("Failed to download media due to network error: %v, retrying in %s...", err, retryDuration) |
| 135 | + time.Sleep(retryDuration) |
| 136 | + } |
| 137 | + return |
| 138 | +} |
| 139 | + |
| 140 | +func (cli *Client) downloadMediaToFile(url string, file io.Writer) (int64, []byte, error) { |
| 141 | + resp, err := cli.doMediaDownloadRequest(url) |
| 142 | + if err != nil { |
| 143 | + return 0, nil, err |
| 144 | + } |
| 145 | + defer resp.Body.Close() |
| 146 | + osFile, ok := file.(*os.File) |
| 147 | + if ok && resp.ContentLength > 0 { |
| 148 | + err = fallocate.Fallocate(osFile, int(resp.ContentLength)) |
| 149 | + if err != nil { |
| 150 | + return 0, nil, fmt.Errorf("failed to preallocate file: %w", err) |
| 151 | + } |
| 152 | + } |
| 153 | + hasher := sha256.New() |
| 154 | + n, err := io.Copy(file, io.TeeReader(resp.Body, hasher)) |
| 155 | + return n, hasher.Sum(nil), err |
| 156 | +} |
| 157 | + |
| 158 | +func (cli *Client) downloadEncryptedMediaToFile(url string, checksum []byte, file File) ([]byte, error) { |
| 159 | + size, hash, err := cli.downloadMediaToFile(url, file) |
| 160 | + if err != nil { |
| 161 | + return nil, err |
| 162 | + } else if size <= mediaHMACLength { |
| 163 | + return nil, ErrTooShortFile |
| 164 | + } else if len(checksum) == 32 && !hmac.Equal(checksum, hash) { |
| 165 | + return nil, ErrInvalidMediaEncSHA256 |
| 166 | + } |
| 167 | + mac := make([]byte, mediaHMACLength) |
| 168 | + _, err = file.ReadAt(mac, size-mediaHMACLength) |
| 169 | + if err != nil { |
| 170 | + return nil, fmt.Errorf("failed to read MAC from file: %w", err) |
| 171 | + } |
| 172 | + err = file.Truncate(size - mediaHMACLength) |
| 173 | + if err != nil { |
| 174 | + return nil, fmt.Errorf("failed to truncate file to remove MAC: %w", err) |
| 175 | + } |
| 176 | + return mac, nil |
| 177 | +} |
| 178 | + |
| 179 | +func validateMediaFile(file io.ReadSeeker, iv, macKey, mac []byte) error { |
| 180 | + h := hmac.New(sha256.New, macKey) |
| 181 | + h.Write(iv) |
| 182 | + _, err := file.Seek(0, io.SeekStart) |
| 183 | + if err != nil { |
| 184 | + return fmt.Errorf("failed to seek to start of file: %w", err) |
| 185 | + } |
| 186 | + _, err = io.Copy(h, file) |
| 187 | + if err != nil { |
| 188 | + return fmt.Errorf("failed to hash file: %w", err) |
| 189 | + } |
| 190 | + if !hmac.Equal(h.Sum(nil)[:mediaHMACLength], mac) { |
| 191 | + return ErrInvalidMediaHMAC |
| 192 | + } |
| 193 | + return nil |
| 194 | +} |
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